Add m-esr52 at 52.6.0

11 files changed, 10302 insertions, 0 deletions

diff --git a/js/src/shell/Makefile.in b/js/src/shell/Makefile.in
new file mode 100644
index 0000000000..ebc58cfc7f
--- /dev/null
+++ b/js/src/shell/Makefile.in
@@ -0,0 +1,16 @@
+# -*- Mode: makefile -*-
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+ifdef QEMU_EXE
+MOZ_POST_PROGRAM_COMMAND = $(topsrcdir)/build/qemu-wrap --qemu $(QEMU_EXE) --libdir $(CROSS_LIB)
+endif
+
+include $(topsrcdir)/config/rules.mk
+
+# Install versioned binary for parallel installability in Linux distributions
+install:: $(PROGRAM)
+	cp $^ $^$(MOZJS_MAJOR_VERSION)
+	$(SYSINSTALL) $^$(MOZJS_MAJOR_VERSION) $(DESTDIR)$(bindir)
diff --git a/js/src/shell/ModuleLoader.js b/js/src/shell/ModuleLoader.js
new file mode 100644
index 0000000000..d8767f05f4
--- /dev/null
+++ b/js/src/shell/ModuleLoader.js
@@ -0,0 +1,43 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// A basic synchronous module loader for testing the shell.
+
+Reflect.Loader = new class {
+    constructor() {
+        this.registry = new Map();
+        this.loadPath = getModuleLoadPath();
+    }
+
+    resolve(name) {
+        if (os.path.isAbsolute(name))
+            return name;
+
+        return os.path.join(this.loadPath, name);
+    }
+
+    fetch(path) {
+        return os.file.readFile(path);
+    }
+
+    loadAndParse(name) {
+        let path = this.resolve(name);
+
+        if (this.registry.has(path))
+            return this.registry.get(path);
+
+        let source = this.fetch(path);
+        let module = parseModule(source, path);
+        this.registry.set(path, module);
+        return module;
+    }
+
+    ["import"](name, referrer) {
+        let module = this.loadAndParse(name);
+        module.declarationInstantiation();
+        return module.evaluation();
+    }
+};
+
+setModuleResolveHook((module, requestName) => Reflect.Loader.loadAndParse(requestName));
diff --git a/js/src/shell/OSObject.cpp b/js/src/shell/OSObject.cpp
new file mode 100644
index 0000000000..846ec7b156
--- /dev/null
+++ b/js/src/shell/OSObject.cpp
@@ -0,0 +1,1029 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// OSObject.h - os object for exposing posix system calls in the JS shell
+
+#include "shell/OSObject.h"
+
+#include <errno.h>
+#include <stdlib.h>
+#ifdef XP_WIN
+#include <direct.h>
+#include <process.h>
+#include <string.h>
+#else
+#include <sys/wait.h>
+#include <unistd.h>
+#endif
+
+#include "jsapi.h"
+// For JSFunctionSpecWithHelp
+#include "jsfriendapi.h"
+#include "jsobj.h"
+#ifdef XP_WIN
+# include "jswin.h"
+#endif
+#include "jswrapper.h"
+
+#include "js/Conversions.h"
+#include "shell/jsshell.h"
+#include "vm/StringBuffer.h"
+#include "vm/TypedArrayObject.h"
+
+#include "jsobjinlines.h"
+
+#ifdef XP_WIN
+# define PATH_MAX (MAX_PATH > _MAX_DIR ? MAX_PATH : _MAX_DIR)
+# define getcwd _getcwd
+#else
+# include <libgen.h>
+#endif
+
+using js::shell::RCFile;
+
+static RCFile** gErrFilePtr = nullptr;
+static RCFile** gOutFilePtr = nullptr;
+
+namespace js {
+namespace shell {
+
+#ifdef XP_WIN
+const char PathSeparator = '\\';
+#else
+const char PathSeparator = '/';
+#endif
+
+static bool
+IsAbsolutePath(const JSAutoByteString& filename)
+{
+    const char* pathname = filename.ptr();
+
+    if (pathname[0] == PathSeparator)
+        return true;
+
+#ifdef XP_WIN
+    // On Windows there are various forms of absolute paths (see
+    // http://msdn.microsoft.com/en-us/library/windows/desktop/aa365247%28v=vs.85%29.aspx
+    // for details):
+    //
+    //   "\..."
+    //   "\\..."
+    //   "C:\..."
+    //
+    // The first two cases are handled by the test above so we only need a test
+    // for the last one here.
+
+    if ((strlen(pathname) > 3 &&
+        isalpha(pathname[0]) && pathname[1] == ':' && pathname[2] == '\\'))
+    {
+        return true;
+    }
+#endif
+
+    return false;
+}
+
+/*
+ * Resolve a (possibly) relative filename to an absolute path. If
+ * |scriptRelative| is true, then the result will be relative to the directory
+ * containing the currently-running script, or the current working directory if
+ * the currently-running script is "-e" (namely, you're using it from the
+ * command line.) Otherwise, it will be relative to the current working
+ * directory.
+ */
+JSString*
+ResolvePath(JSContext* cx, HandleString filenameStr, PathResolutionMode resolveMode)
+{
+    if (!filenameStr) {
+#ifdef XP_WIN
+        return JS_NewStringCopyZ(cx, "nul");
+#else
+        return JS_NewStringCopyZ(cx, "/dev/null");
+#endif
+    }
+
+    JSAutoByteString filename(cx, filenameStr);
+    if (!filename)
+        return nullptr;
+
+    if (IsAbsolutePath(filename))
+        return filenameStr;
+
+    /* Get the currently executing script's name. */
+    JS::AutoFilename scriptFilename;
+    if (!DescribeScriptedCaller(cx, &scriptFilename))
+        return nullptr;
+
+    if (!scriptFilename.get())
+        return nullptr;
+
+    if (strcmp(scriptFilename.get(), "-e") == 0 || strcmp(scriptFilename.get(), "typein") == 0)
+        resolveMode = RootRelative;
+
+    char buffer[PATH_MAX+1];
+    if (resolveMode == ScriptRelative) {
+#ifdef XP_WIN
+        // The docs say it can return EINVAL, but the compiler says it's void
+        _splitpath(scriptFilename.get(), nullptr, buffer, nullptr, nullptr);
+#else
+        strncpy(buffer, scriptFilename.get(), PATH_MAX+1);
+        if (buffer[PATH_MAX] != '\0')
+            return nullptr;
+
+        // dirname(buffer) might return buffer, or it might return a
+        // statically-allocated string
+        memmove(buffer, dirname(buffer), strlen(buffer) + 1);
+#endif
+    } else {
+        const char* cwd = getcwd(buffer, PATH_MAX);
+        if (!cwd)
+            return nullptr;
+    }
+
+    size_t len = strlen(buffer);
+    buffer[len] = '/';
+    strncpy(buffer + len + 1, filename.ptr(), sizeof(buffer) - (len+1));
+    if (buffer[PATH_MAX] != '\0')
+        return nullptr;
+
+    return JS_NewStringCopyZ(cx, buffer);
+}
+
+JSObject*
+FileAsTypedArray(JSContext* cx, JS::HandleString pathnameStr)
+{
+    JSAutoByteString pathname(cx, pathnameStr);
+    if (!pathname)
+        return nullptr;
+
+    FILE* file = fopen(pathname.ptr(), "rb");
+    if (!file) {
+        /*
+         * Use Latin1 variant here because the encoding of the return value of
+         * strerror function can be non-UTF-8.
+         */
+        JS_ReportErrorLatin1(cx, "can't open %s: %s", pathname.ptr(), strerror(errno));
+        return nullptr;
+    }
+    AutoCloseFile autoClose(file);
+
+    RootedObject obj(cx);
+    if (fseek(file, 0, SEEK_END) != 0) {
+        pathname.clear();
+        if (!pathname.encodeUtf8(cx, pathnameStr))
+            return nullptr;
+        JS_ReportErrorUTF8(cx, "can't seek end of %s", pathname.ptr());
+    } else {
+        size_t len = ftell(file);
+        if (fseek(file, 0, SEEK_SET) != 0) {
+            pathname.clear();
+            if (!pathname.encodeUtf8(cx, pathnameStr))
+                return nullptr;
+            JS_ReportErrorUTF8(cx, "can't seek start of %s", pathname.ptr());
+        } else {
+            obj = JS_NewUint8Array(cx, len);
+            if (!obj)
+                return nullptr;
+            js::TypedArrayObject& ta = obj->as<js::TypedArrayObject>();
+            if (ta.isSharedMemory()) {
+                // Must opt in to use shared memory.  For now, don't.
+                //
+                // (It is incorrect to read into the buffer without
+                // synchronization since that can create a race.  A
+                // lock here won't fix it - both sides must
+                // participate.  So what one must do is to create a
+                // temporary buffer, read into that, and use a
+                // race-safe primitive to copy memory into the
+                // buffer.)
+                pathname.clear();
+                if (!pathname.encodeUtf8(cx, pathnameStr))
+                    return nullptr;
+                JS_ReportErrorUTF8(cx, "can't read %s: shared memory buffer", pathname.ptr());
+                return nullptr;
+            }
+            char* buf = static_cast<char*>(ta.viewDataUnshared());
+            size_t cc = fread(buf, 1, len, file);
+            if (cc != len) {
+                if (ptrdiff_t(cc) < 0) {
+                    /*
+                     * Use Latin1 variant here because the encoding of the return
+                     * value of strerror function can be non-UTF-8.
+                     */
+                    JS_ReportErrorLatin1(cx, "can't read %s: %s", pathname.ptr(), strerror(errno));
+                } else {
+                    pathname.clear();
+                    if (!pathname.encodeUtf8(cx, pathnameStr))
+                        return nullptr;
+                    JS_ReportErrorUTF8(cx, "can't read %s: short read", pathname.ptr());
+                }
+                obj = nullptr;
+            }
+        }
+    }
+    return obj;
+}
+
+static bool
+ReadFile(JSContext* cx, unsigned argc, Value* vp, bool scriptRelative)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() < 1 || args.length() > 2) {
+        JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr,
+                                  args.length() < 1 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
+                                  "snarf");
+        return false;
+    }
+
+    if (!args[0].isString() || (args.length() == 2 && !args[1].isString())) {
+        JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "snarf");
+        return false;
+    }
+
+    RootedString givenPath(cx, args[0].toString());
+    RootedString str(cx, js::shell::ResolvePath(cx, givenPath, scriptRelative ? ScriptRelative : RootRelative));
+    if (!str)
+        return false;
+
+    if (args.length() > 1) {
+        JSString* opt = JS::ToString(cx, args[1]);
+        if (!opt)
+            return false;
+        bool match;
+        if (!JS_StringEqualsAscii(cx, opt, "binary", &match))
+            return false;
+        if (match) {
+            JSObject* obj;
+            if (!(obj = FileAsTypedArray(cx, str)))
+                return false;
+            args.rval().setObject(*obj);
+            return true;
+        }
+    }
+
+    if (!(str = FileAsString(cx, str)))
+        return false;
+    args.rval().setString(str);
+    return true;
+}
+
+static bool
+osfile_readFile(JSContext* cx, unsigned argc, Value* vp)
+{
+    return ReadFile(cx, argc, vp, false);
+}
+
+static bool
+osfile_readRelativeToScript(JSContext* cx, unsigned argc, Value* vp)
+{
+    return ReadFile(cx, argc, vp, true);
+}
+
+static bool
+osfile_writeTypedArrayToFile(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 2 ||
+        !args[0].isString() ||
+        !args[1].isObject() ||
+        !args[1].toObject().is<TypedArrayObject>())
+    {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "writeTypedArrayToFile");
+        return false;
+    }
+
+    RootedString givenPath(cx, args[0].toString());
+    RootedString str(cx, ResolvePath(cx, givenPath, RootRelative));
+    if (!str)
+        return false;
+
+    JSAutoByteString filename(cx, str);
+    if (!filename)
+        return false;
+
+    FILE* file = fopen(filename.ptr(), "wb");
+    if (!file) {
+        /*
+         * Use Latin1 variant here because the encoding of the return value of
+         * strerror function can be non-UTF-8.
+         */
+        JS_ReportErrorLatin1(cx, "can't open %s: %s", filename.ptr(), strerror(errno));
+        return false;
+    }
+    AutoCloseFile autoClose(file);
+
+    TypedArrayObject* obj = &args[1].toObject().as<TypedArrayObject>();
+
+    if (obj->isSharedMemory()) {
+        // Must opt in to use shared memory.  For now, don't.
+        //
+        // See further comments in FileAsTypedArray, above.
+        filename.clear();
+        if (!filename.encodeUtf8(cx, str))
+            return false;
+        JS_ReportErrorUTF8(cx, "can't write %s: shared memory buffer", filename.ptr());
+        return false;
+    }
+    void* buf = obj->viewDataUnshared();
+    if (fwrite(buf, obj->bytesPerElement(), obj->length(), file) != obj->length() ||
+        !autoClose.release())
+    {
+        filename.clear();
+        if (!filename.encodeUtf8(cx, str))
+            return false;
+        JS_ReportErrorUTF8(cx, "can't write %s", filename.ptr());
+        return false;
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+/* static */ RCFile*
+RCFile::create(JSContext* cx, const char* filename, const char* mode)
+{
+    FILE* fp = fopen(filename, mode);
+    if (!fp)
+        return nullptr;
+
+    RCFile* file = cx->new_<RCFile>(fp);
+    if (!file) {
+        fclose(fp);
+        return nullptr;
+    }
+
+    return file;
+}
+
+void
+RCFile::close()
+{
+    if (fp)
+        fclose(fp);
+    fp = nullptr;
+}
+
+bool
+RCFile::release()
+{
+    if (--numRefs)
+        return false;
+    this->close();
+    return true;
+}
+
+class FileObject : public JSObject {
+    enum : uint32_t {
+        FILE_SLOT = 0,
+        NUM_SLOTS
+    };
+
+  public:
+    static const js::Class class_;
+
+    static FileObject* create(JSContext* cx, RCFile* file) {
+        JSObject* obj = js::NewObjectWithClassProto(cx, &class_, nullptr);
+        if (!obj)
+            return nullptr;
+
+        FileObject* fileObj = &obj->as<FileObject>();
+        fileObj->setRCFile(file);
+        file->acquire();
+        return fileObj;
+    }
+
+    static void finalize(FreeOp* fop, JSObject* obj) {
+        FileObject* fileObj = &obj->as<FileObject>();
+        RCFile* file = fileObj->rcFile();
+        if (file->release()) {
+            fileObj->setRCFile(nullptr);
+            fop->delete_(file);
+        }
+    }
+
+    bool isOpen() {
+        RCFile* file = rcFile();
+        return file && file->isOpen();
+    }
+
+    void close() {
+        if (!isOpen())
+            return;
+        rcFile()->close();
+    }
+
+    RCFile* rcFile() {
+        return reinterpret_cast<RCFile*>(js::GetReservedSlot(this, FILE_SLOT).toPrivate());
+    }
+
+  private:
+
+    void setRCFile(RCFile* file) {
+        js::SetReservedSlot(this, FILE_SLOT, PrivateValue(file));
+    }
+};
+
+static const js::ClassOps FileObjectClassOps = {
+    nullptr,               /* addProperty */
+    nullptr,               /* delProperty */
+    nullptr,               /* getProperty */
+    nullptr,               /* setProperty */
+    nullptr,               /* enumerate */
+    nullptr,               /* resolve */
+    nullptr,               /* mayResolve */
+    FileObject::finalize,  /* finalize */
+    nullptr,               /* call */
+    nullptr,               /* hasInstance */
+    nullptr,               /* construct */
+    nullptr                /* trace */
+};
+
+const js::Class FileObject::class_ = {
+    "File",
+    JSCLASS_HAS_RESERVED_SLOTS(FileObject::NUM_SLOTS) |
+    JSCLASS_FOREGROUND_FINALIZE,
+    &FileObjectClassOps
+};
+
+static FileObject*
+redirect(JSContext* cx, HandleString relFilename, RCFile** globalFile)
+{
+    RootedString filename(cx, ResolvePath(cx, relFilename, RootRelative));
+    if (!filename)
+        return nullptr;
+    JSAutoByteString filenameABS(cx, filename);
+    if (!filenameABS)
+        return nullptr;
+    RCFile* file = RCFile::create(cx, filenameABS.ptr(), "wb");
+    if (!file) {
+        /*
+         * Use Latin1 variant here because the encoding of the return value of
+         * strerror function can be non-UTF-8.
+         */
+        JS_ReportErrorLatin1(cx, "cannot redirect to %s: %s", filenameABS.ptr(), strerror(errno));
+        return nullptr;
+    }
+
+    // Grant the global gOutFile ownership of the new file, release ownership
+    // of its old file, and return a FileObject owning the old file.
+    file->acquire(); // Global owner of new file
+
+    FileObject* fileObj = FileObject::create(cx, *globalFile); // Newly created owner of old file
+    if (!fileObj) {
+        file->release();
+        return nullptr;
+    }
+
+    (*globalFile)->release(); // Release (global) ownership of old file.
+    *globalFile = file;
+
+    return fileObj;
+}
+
+static bool
+Redirect(JSContext* cx, const CallArgs& args, RCFile** outFile)
+{
+    if (args.length() > 1) {
+        JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "redirect");
+        return false;
+    }
+
+    RCFile* oldFile = *outFile;
+    RootedObject oldFileObj(cx, FileObject::create(cx, oldFile));
+    if (!oldFileObj)
+        return false;
+
+    if (args.get(0).isUndefined()) {
+        args.rval().setObject(*oldFileObj);
+        return true;
+    }
+
+    if (args[0].isObject()) {
+        RootedObject fileObj(cx, js::CheckedUnwrap(&args[0].toObject()));
+        if (!fileObj)
+            return false;
+
+        if (fileObj->is<FileObject>()) {
+            // Passed in a FileObject. Create a FileObject for the previous
+            // global file, and set the global file to the passed-in one.
+            *outFile = fileObj->as<FileObject>().rcFile();
+            (*outFile)->acquire();
+            oldFile->release();
+
+            args.rval().setObject(*oldFileObj);
+            return true;
+        }
+    }
+
+    RootedString filename(cx);
+    if (!args[0].isNull()) {
+        filename = JS::ToString(cx, args[0]);
+        if (!filename)
+            return false;
+    }
+
+    if (!redirect(cx, filename, outFile))
+        return false;
+
+    args.rval().setObject(*oldFileObj);
+    return true;
+}
+
+static bool
+osfile_redirectOutput(JSContext* cx, unsigned argc, Value* vp) {
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return Redirect(cx, args, gOutFilePtr);
+}
+
+static bool
+osfile_redirectError(JSContext* cx, unsigned argc, Value* vp) {
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return Redirect(cx, args, gErrFilePtr);
+}
+
+static bool
+osfile_close(JSContext* cx, unsigned argc, Value* vp) {
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    Rooted<FileObject*> fileObj(cx);
+    if (args.get(0).isObject()) {
+        JSObject *obj = js::CheckedUnwrap(&args[0].toObject());
+        if (obj->is<FileObject>())
+            fileObj = &obj->as<FileObject>();
+    }
+
+    if (!fileObj) {
+        JS_ReportErrorNumberASCII(cx, js::shell::my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "close");
+        return false;
+    }
+
+    fileObj->close();
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static const JSFunctionSpecWithHelp osfile_functions[] = {
+    JS_FN_HELP("readFile", osfile_readFile, 1, 0,
+"readFile(filename, [\"binary\"])",
+"  Read filename into returned string. Filename is relative to the current\n"
+               "  working directory."),
+
+    JS_FN_HELP("readRelativeToScript", osfile_readRelativeToScript, 1, 0,
+"readRelativeToScript(filename, [\"binary\"])",
+"  Read filename into returned string. Filename is relative to the directory\n"
+"  containing the current script."),
+
+    JS_FS_HELP_END
+};
+
+static const JSFunctionSpecWithHelp osfile_unsafe_functions[] = {
+    JS_FN_HELP("writeTypedArrayToFile", osfile_writeTypedArrayToFile, 2, 0,
+"writeTypedArrayToFile(filename, data)",
+"  Write the contents of a typed array to the named file."),
+
+    JS_FN_HELP("redirect", osfile_redirectOutput, 1, 0,
+"redirect([path-or-object])",
+"  Redirect print() output to the named file.\n"
+"   Return an opaque object representing the previous destination, which\n"
+"   may be passed into redirect() later to restore the output."),
+
+    JS_FN_HELP("redirectErr", osfile_redirectError, 1, 0,
+"redirectErr([path-or-object])",
+"  Same as redirect(), but for printErr"),
+
+    JS_FN_HELP("close", osfile_close, 1, 0,
+"close(object)",
+"  Close the file returned by an earlier redirect call."),
+
+    JS_FS_HELP_END
+};
+
+static bool
+ospath_isAbsolute(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 1 || !args[0].isString()) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "isAbsolute");
+        return false;
+    }
+
+    JSAutoByteString path(cx, args[0].toString());
+    if (!path)
+        return false;
+
+    args.rval().setBoolean(IsAbsolutePath(path));
+    return true;
+}
+
+static bool
+ospath_join(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() < 1) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS, "join");
+        return false;
+    }
+
+    // This function doesn't take into account some aspects of Windows paths,
+    // e.g. the drive letter is always reset when an absolute path is appended.
+
+    StringBuffer buffer(cx);
+
+    for (unsigned i = 0; i < args.length(); i++) {
+        if (!args[i].isString()) {
+            JS_ReportErrorASCII(cx, "join expects string arguments only");
+            return false;
+        }
+
+        JSAutoByteString path(cx, args[i].toString());
+        if (!path)
+            return false;
+
+        if (IsAbsolutePath(path)) {
+            MOZ_ALWAYS_TRUE(buffer.resize(0));
+        } else if (i != 0) {
+            if (!buffer.append(PathSeparator))
+                return false;
+        }
+
+        if (!buffer.append(args[i].toString()))
+            return false;
+    }
+
+    JSString* result = buffer.finishString();
+    if (!result)
+        return false;
+
+    args.rval().setString(result);
+    return true;
+}
+
+static const JSFunctionSpecWithHelp ospath_functions[] = {
+    JS_FN_HELP("isAbsolute", ospath_isAbsolute, 1, 0,
+"isAbsolute(path)",
+"  Return whether the given path is absolute."),
+
+    JS_FN_HELP("join", ospath_join, 1, 0,
+"join(paths...)",
+"  Join one or more path components in a platform independent way."),
+
+    JS_FS_HELP_END
+};
+
+static bool
+os_getenv(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() < 1) {
+        JS_ReportErrorASCII(cx, "os.getenv requires 1 argument");
+        return false;
+    }
+    RootedString key(cx, ToString(cx, args[0]));
+    if (!key)
+        return false;
+    JSAutoByteString keyBytes;
+    if (!keyBytes.encodeUtf8(cx, key))
+        return false;
+
+    if (const char* valueBytes = getenv(keyBytes.ptr())) {
+        RootedString value(cx, JS_NewStringCopyZ(cx, valueBytes));
+        if (!value)
+            return false;
+        args.rval().setString(value);
+    } else {
+        args.rval().setUndefined();
+    }
+    return true;
+}
+
+static bool
+os_getpid(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() != 0) {
+        JS_ReportErrorASCII(cx, "os.getpid takes no arguments");
+        return false;
+    }
+    args.rval().setInt32(getpid());
+    return true;
+}
+
+#if !defined(XP_WIN)
+
+// There are two possible definitions of strerror_r floating around. The GNU
+// one returns a char* which may or may not be the buffer you passed in. The
+// other one returns an integer status code, and always writes the result into
+// the provided buffer.
+
+inline char*
+strerror_message(int result, char* buffer)
+{
+    return result == 0 ? buffer : nullptr;
+}
+
+inline char*
+strerror_message(char* result, char* buffer)
+{
+    return result;
+}
+
+#endif
+
+static void
+ReportSysError(JSContext* cx, const char* prefix)
+{
+    char buffer[200];
+
+#if defined(XP_WIN)
+    strerror_s(buffer, sizeof(buffer), errno);
+    const char* errstr = buffer;
+#else
+    const char* errstr = strerror_message(strerror_r(errno, buffer, sizeof(buffer)), buffer);
+#endif
+
+    if (!errstr)
+        errstr = "unknown error";
+
+    size_t nbytes = strlen(prefix) + strlen(errstr) + 3;
+    char* final = (char*) js_malloc(nbytes);
+    if (!final) {
+        JS_ReportOutOfMemory(cx);
+        return;
+    }
+
+    snprintf(final, nbytes, "%s: %s", prefix, errstr);
+    /*
+     * Use Latin1 variant here because the encoding of the return value of
+     * strerror_s and strerror_r function can be non-UTF-8.
+     */
+    JS_ReportErrorLatin1(cx, "%s", final);
+    js_free(final);
+}
+
+static bool
+os_system(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() == 0) {
+        JS_ReportErrorASCII(cx, "os.system requires 1 argument");
+        return false;
+    }
+
+    JSString* str = JS::ToString(cx, args[0]);
+    if (!str)
+        return false;
+
+    JSAutoByteString command(cx, str);
+    if (!command)
+        return false;
+
+    int result = system(command.ptr());
+    if (result == -1) {
+        ReportSysError(cx, "system call failed");
+        return false;
+    }
+
+    args.rval().setInt32(result);
+    return true;
+}
+
+#ifndef XP_WIN
+static bool
+os_spawn(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() == 0) {
+        JS_ReportErrorASCII(cx, "os.spawn requires 1 argument");
+        return false;
+    }
+
+    JSString* str = JS::ToString(cx, args[0]);
+    if (!str)
+        return false;
+
+    JSAutoByteString command(cx, str);
+    if (!command)
+        return false;
+
+    int32_t childPid = fork();
+    if (childPid == -1) {
+        ReportSysError(cx, "fork failed");
+        return false;
+    }
+
+    if (childPid) {
+        args.rval().setInt32(childPid);
+        return true;
+    }
+
+    // We are in the child
+
+    const char* cmd[] = {"sh", "-c", nullptr, nullptr};
+    cmd[2] = command.ptr();
+
+    execvp("sh", (char * const*)cmd);
+    exit(1);
+}
+
+static bool
+os_kill(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    int32_t pid;
+    if (args.length() < 1) {
+        JS_ReportErrorASCII(cx, "os.kill requires 1 argument");
+        return false;
+    }
+    if (!JS::ToInt32(cx, args[0], &pid))
+        return false;
+
+    // It is too easy to kill yourself accidentally with os.kill("goose").
+    if (pid == 0 && !args[0].isInt32()) {
+        JS_ReportErrorASCII(cx, "os.kill requires numeric pid");
+        return false;
+    }
+
+    int signal = SIGINT;
+    if (args.length() > 1) {
+        if (!JS::ToInt32(cx, args[1], &signal))
+            return false;
+    }
+
+    int status = kill(pid, signal);
+    if (status == -1) {
+        ReportSysError(cx, "kill failed");
+        return false;
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+os_waitpid(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    int32_t pid;
+    if (args.length() == 0) {
+        pid = -1;
+    } else {
+        if (!JS::ToInt32(cx, args[0], &pid))
+            return false;
+    }
+
+    bool nohang = false;
+    if (args.length() >= 2)
+        nohang = JS::ToBoolean(args[1]);
+
+    int status = 0;
+    pid_t result = waitpid(pid, &status, nohang ? WNOHANG : 0);
+    if (result == -1) {
+        ReportSysError(cx, "os.waitpid failed");
+        return false;
+    }
+
+    RootedObject info(cx, JS_NewPlainObject(cx));
+    if (!info)
+        return false;
+
+    RootedValue v(cx);
+    if (result != 0) {
+        v.setInt32(result);
+        if (!JS_DefineProperty(cx, info, "pid", v, JSPROP_ENUMERATE))
+            return false;
+        if (WIFEXITED(status)) {
+            v.setInt32(WEXITSTATUS(status));
+            if (!JS_DefineProperty(cx, info, "exitStatus", v, JSPROP_ENUMERATE))
+                return false;
+        }
+    }
+
+    args.rval().setObject(*info);
+    return true;
+}
+#endif
+
+static const JSFunctionSpecWithHelp os_functions[] = {
+    JS_FN_HELP("getenv", os_getenv, 1, 0,
+"getenv(variable)",
+"  Get the value of an environment variable."),
+
+    JS_FN_HELP("getpid", os_getpid, 0, 0,
+"getpid()",
+"  Return the current process id."),
+
+    JS_FN_HELP("system", os_system, 1, 0,
+"system(command)",
+"  Execute command on the current host, returning result code or throwing an\n"
+"  exception on failure."),
+
+#ifndef XP_WIN
+    JS_FN_HELP("spawn", os_spawn, 1, 0,
+"spawn(command)",
+"  Start up a separate process running the given command. Returns the pid."),
+
+    JS_FN_HELP("kill", os_kill, 1, 0,
+"kill(pid[, signal])",
+"  Send a signal to the given pid. The default signal is SIGINT. The signal\n"
+"  passed in must be numeric, if given."),
+
+    JS_FN_HELP("waitpid", os_waitpid, 1, 0,
+"waitpid(pid[, nohang])",
+"  Calls waitpid(). 'nohang' is a boolean indicating whether to pass WNOHANG.\n"
+"  The return value is an object containing a 'pid' field, if a process was waitable\n"
+"  and an 'exitStatus' field if a pid exited."),
+#endif
+
+    JS_FS_HELP_END
+};
+
+bool
+DefineOS(JSContext* cx, HandleObject global,
+         bool fuzzingSafe,
+         RCFile** shellOut, RCFile** shellErr)
+{
+    RootedObject obj(cx, JS_NewPlainObject(cx));
+    if (!obj || !JS_DefineProperty(cx, global, "os", obj, 0))
+        return false;
+
+    if (!fuzzingSafe) {
+        if (!JS_DefineFunctionsWithHelp(cx, obj, os_functions))
+            return false;
+    }
+
+    RootedObject osfile(cx, JS_NewPlainObject(cx));
+    if (!osfile ||
+        !JS_DefineFunctionsWithHelp(cx, osfile, osfile_functions) ||
+        !JS_DefineProperty(cx, obj, "file", osfile, 0))
+    {
+        return false;
+    }
+
+    if (!fuzzingSafe) {
+        if (!JS_DefineFunctionsWithHelp(cx, osfile, osfile_unsafe_functions))
+            return false;
+    }
+
+    if (!GenerateInterfaceHelp(cx, osfile, "os.file"))
+        return false;
+
+    RootedObject ospath(cx, JS_NewPlainObject(cx));
+    if (!ospath ||
+        !JS_DefineFunctionsWithHelp(cx, ospath, ospath_functions) ||
+        !JS_DefineProperty(cx, obj, "path", ospath, 0) ||
+        !GenerateInterfaceHelp(cx, ospath, "os.path"))
+    {
+        return false;
+    }
+
+    if (!GenerateInterfaceHelp(cx, obj, "os"))
+        return false;
+
+    gOutFilePtr = shellOut;
+    gErrFilePtr = shellErr;
+
+    // For backwards compatibility, expose various os.file.* functions as
+    // direct methods on the global.
+    RootedValue val(cx);
+
+    struct {
+        const char* src;
+        const char* dst;
+    } osfile_exports[] = {
+        { "readFile", "read" },
+        { "readFile", "snarf" },
+        { "readRelativeToScript", "readRelativeToScript" },
+        { "redirect", "redirect" },
+        { "redirectErr", "redirectErr" }
+    };
+
+    for (auto pair : osfile_exports) {
+        if (!JS_GetProperty(cx, osfile, pair.src, &val))
+            return false;
+        if (val.isObject()) {
+            RootedObject function(cx, &val.toObject());
+            if (!JS_DefineProperty(cx, global, pair.dst, function, 0))
+                return false;
+        }
+    }
+
+    return true;
+}
+
+} // namespace shell
+} // namespace js
diff --git a/js/src/shell/OSObject.h b/js/src/shell/OSObject.h
new file mode 100644
index 0000000000..6df7005da6
--- /dev/null
+++ b/js/src/shell/OSObject.h
@@ -0,0 +1,39 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// OSObject.h - os object for exposing posix system calls in the JS shell
+
+#ifndef shell_OSObject_h
+#define shell_OSObject_h
+
+#include "jsapi.h"
+
+namespace js {
+namespace shell {
+
+struct RCFile;
+
+/* Define an os object on the given global object. */
+bool
+DefineOS(JSContext* cx, JS::HandleObject global,
+         bool fuzzingSafe,
+         RCFile** shellOut, RCFile** shellErr);
+
+enum PathResolutionMode {
+    RootRelative,
+    ScriptRelative
+};
+
+JSString*
+ResolvePath(JSContext* cx, JS::HandleString filenameStr, PathResolutionMode resolveMode);
+
+JSObject*
+FileAsTypedArray(JSContext* cx, JS::HandleString pathnameStr);
+
+} // namespace shell
+} // namespace js
+
+#endif /* shell_OSObject_h */
diff --git a/js/src/shell/js-gdb.py.in b/js/src/shell/js-gdb.py.in
new file mode 100644
index 0000000000..16199bb4cc
--- /dev/null
+++ b/js/src/shell/js-gdb.py.in
@@ -0,0 +1,11 @@
+""" GDB Python customization auto-loader for js shell """
+#filter substitution
+
+import os.path
+sys.path[0:0] = [os.path.join('@topsrcdir@', 'gdb')]
+
+import mozilla.autoload
+mozilla.autoload.register(gdb.current_objfile())
+
+import mozilla.asmjs
+mozilla.asmjs.install()
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
new file mode 100644
index 0000000000..00a4a503ce
--- /dev/null
+++ b/js/src/shell/js.cpp
@@ -0,0 +1,7997 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* JS shell. */
+
+#include "mozilla/ArrayUtils.h"
+#include "mozilla/Atomics.h"
+#include "mozilla/Attributes.h"
+#include "mozilla/DebugOnly.h"
+#include "mozilla/GuardObjects.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "mozilla/mozalloc.h"
+#include "mozilla/PodOperations.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/SizePrintfMacros.h"
+#include "mozilla/Sprintf.h"
+#include "mozilla/TimeStamp.h"
+
+#ifdef XP_WIN
+# include <direct.h>
+# include <process.h>
+#endif
+#include <errno.h>
+#include <fcntl.h>
+#if defined(XP_WIN)
+# include <io.h>     /* for isatty() */
+#endif
+#include <locale.h>
+#if defined(MALLOC_H)
+# include MALLOC_H    /* for malloc_usable_size, malloc_size, _msize */
+#endif
+#include <math.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#ifdef XP_UNIX
+# include <sys/mman.h>
+# include <sys/stat.h>
+# include <sys/wait.h>
+# include <unistd.h>
+#endif
+
+#include "jsapi.h"
+#include "jsarray.h"
+#include "jsatom.h"
+#include "jscntxt.h"
+#include "jsfun.h"
+#include "jsobj.h"
+#include "jsprf.h"
+#include "jsscript.h"
+#include "jstypes.h"
+#include "jsutil.h"
+#ifdef XP_WIN
+# include "jswin.h"
+#endif
+#include "jswrapper.h"
+#include "shellmoduleloader.out.h"
+
+#include "builtin/ModuleObject.h"
+#include "builtin/TestingFunctions.h"
+#include "frontend/Parser.h"
+#include "gc/GCInternals.h"
+#include "jit/arm/Simulator-arm.h"
+#include "jit/InlinableNatives.h"
+#include "jit/Ion.h"
+#include "jit/JitcodeMap.h"
+#include "jit/OptimizationTracking.h"
+#include "js/Debug.h"
+#include "js/GCAPI.h"
+#include "js/Initialization.h"
+#include "js/StructuredClone.h"
+#include "js/TrackedOptimizationInfo.h"
+#include "perf/jsperf.h"
+#include "shell/jsoptparse.h"
+#include "shell/jsshell.h"
+#include "shell/OSObject.h"
+#include "threading/ConditionVariable.h"
+#include "threading/LockGuard.h"
+#include "threading/Thread.h"
+#include "vm/ArgumentsObject.h"
+#include "vm/AsyncFunction.h"
+#include "vm/Compression.h"
+#include "vm/Debugger.h"
+#include "vm/HelperThreads.h"
+#include "vm/Monitor.h"
+#include "vm/MutexIDs.h"
+#include "vm/Shape.h"
+#include "vm/SharedArrayObject.h"
+#include "vm/StringBuffer.h"
+#include "vm/Time.h"
+#include "vm/TypedArrayObject.h"
+#include "vm/WrapperObject.h"
+#include "wasm/WasmJS.h"
+
+#include "jscompartmentinlines.h"
+#include "jsobjinlines.h"
+
+#include "vm/ErrorObject-inl.h"
+#include "vm/Interpreter-inl.h"
+#include "vm/Stack-inl.h"
+
+using namespace js;
+using namespace js::cli;
+using namespace js::shell;
+
+using mozilla::ArrayLength;
+using mozilla::Atomic;
+using mozilla::MakeScopeExit;
+using mozilla::Maybe;
+using mozilla::Nothing;
+using mozilla::NumberEqualsInt32;
+using mozilla::PodCopy;
+using mozilla::PodEqual;
+using mozilla::TimeDuration;
+using mozilla::TimeStamp;
+
+enum JSShellExitCode {
+    EXITCODE_RUNTIME_ERROR      = 3,
+    EXITCODE_FILE_NOT_FOUND     = 4,
+    EXITCODE_OUT_OF_MEMORY      = 5,
+    EXITCODE_TIMEOUT            = 6
+};
+
+static const size_t gStackChunkSize = 8192;
+
+/*
+ * Note: This limit should match the stack limit set by the browser in
+ *       js/xpconnect/src/XPCJSContext.cpp
+ */
+#if defined(MOZ_ASAN) || (defined(DEBUG) && !defined(XP_WIN))
+static const size_t gMaxStackSize = 2 * 128 * sizeof(size_t) * 1024;
+#else
+static const size_t gMaxStackSize = 128 * sizeof(size_t) * 1024;
+#endif
+
+/*
+ * Limit the timeout to 30 minutes to prevent an overflow on platfoms
+ * that represent the time internally in microseconds using 32-bit int.
+ */
+static const double MAX_TIMEOUT_SECONDS = 1800.0;
+
+// SharedArrayBuffer and Atomics settings track Firefox.  Choose a custom setting
+// with --shared-memory={on,off}.
+#ifndef RELEASE_OR_BETA
+# define SHARED_MEMORY_DEFAULT 1
+#else
+# define SHARED_MEMORY_DEFAULT 0
+#endif
+
+#ifdef SPIDERMONKEY_PROMISE
+using JobQueue = GCVector<JSObject*, 0, SystemAllocPolicy>;
+
+struct ShellAsyncTasks
+{
+    explicit ShellAsyncTasks(JSContext* cx)
+      : outstanding(0),
+        finished(cx)
+    {}
+
+    size_t outstanding;
+    Vector<JS::AsyncTask*> finished;
+};
+#endif // SPIDERMONKEY_PROMISE
+
+enum class ScriptKind
+{
+    Script,
+    Module
+};
+
+class OffThreadState {
+    enum State {
+        IDLE,           /* ready to work; no token, no source */
+        COMPILING,      /* working; no token, have source */
+        DONE            /* compilation done: have token and source */
+    };
+
+  public:
+    OffThreadState()
+      : monitor(mutexid::ShellOffThreadState),
+        state(IDLE),
+        token(),
+        source(nullptr)
+    { }
+
+    bool startIfIdle(JSContext* cx, ScriptKind kind,
+                     ScopedJSFreePtr<char16_t>& newSource)
+    {
+        AutoLockMonitor alm(monitor);
+        if (state != IDLE)
+            return false;
+
+        MOZ_ASSERT(!token);
+
+        source = newSource.forget();
+
+        scriptKind = kind;
+        state = COMPILING;
+        return true;
+    }
+
+    void abandon(JSContext* cx) {
+        AutoLockMonitor alm(monitor);
+        MOZ_ASSERT(state == COMPILING);
+        MOZ_ASSERT(!token);
+        MOZ_ASSERT(source);
+
+        js_free(source);
+        source = nullptr;
+
+        state = IDLE;
+    }
+
+    void markDone(void* newToken) {
+        AutoLockMonitor alm(monitor);
+        MOZ_ASSERT(state == COMPILING);
+        MOZ_ASSERT(!token);
+        MOZ_ASSERT(source);
+        MOZ_ASSERT(newToken);
+
+        token = newToken;
+        state = DONE;
+        alm.notify();
+    }
+
+    void* waitUntilDone(JSContext* cx, ScriptKind kind) {
+        AutoLockMonitor alm(monitor);
+        if (state == IDLE || scriptKind != kind)
+            return nullptr;
+
+        if (state == COMPILING) {
+            while (state != DONE)
+                alm.wait();
+        }
+
+        MOZ_ASSERT(source);
+        js_free(source);
+        source = nullptr;
+
+        MOZ_ASSERT(token);
+        void* holdToken = token;
+        token = nullptr;
+        state = IDLE;
+        return holdToken;
+    }
+
+  private:
+    Monitor monitor;
+    ScriptKind scriptKind;
+    State state;
+    void* token;
+    char16_t* source;
+};
+
+// Per-context shell state.
+struct ShellContext
+{
+    explicit ShellContext(JSContext* cx);
+
+    bool isWorker;
+    double timeoutInterval;
+    double startTime;
+    Atomic<bool> serviceInterrupt;
+    Atomic<bool> haveInterruptFunc;
+    JS::PersistentRootedValue interruptFunc;
+    bool lastWarningEnabled;
+    JS::PersistentRootedValue lastWarning;
+#ifdef SPIDERMONKEY_PROMISE
+    JS::PersistentRootedValue promiseRejectionTrackerCallback;
+    JS::PersistentRooted<JobQueue> jobQueue;
+    ExclusiveData<ShellAsyncTasks> asyncTasks;
+    bool drainingJobQueue;
+#endif // SPIDERMONKEY_PROMISE
+
+    /*
+     * Watchdog thread state.
+     */
+    Mutex watchdogLock;
+    ConditionVariable watchdogWakeup;
+    Maybe<Thread> watchdogThread;
+    Maybe<TimeStamp> watchdogTimeout;
+
+    ConditionVariable sleepWakeup;
+
+    int exitCode;
+    bool quitting;
+
+    UniqueChars readLineBuf;
+    size_t readLineBufPos;
+
+    static const uint32_t SpsProfilingMaxStackSize = 1000;
+    ProfileEntry spsProfilingStack[SpsProfilingMaxStackSize];
+    uint32_t spsProfilingStackSize;
+
+    OffThreadState offThreadState;
+};
+
+struct MOZ_STACK_CLASS EnvironmentPreparer : public js::ScriptEnvironmentPreparer {
+    JSContext* cx;
+    explicit EnvironmentPreparer(JSContext* cx)
+      : cx(cx)
+    {
+        js::SetScriptEnvironmentPreparer(cx, this);
+    }
+    void invoke(JS::HandleObject scope, Closure& closure) override;
+};
+
+// Shell state set once at startup.
+static bool enableCodeCoverage = false;
+static bool enableDisassemblyDumps = false;
+static bool offthreadCompilation = false;
+static bool enableBaseline = false;
+static bool enableIon = false;
+static bool enableAsmJS = false;
+static bool enableWasm = false;
+static bool enableNativeRegExp = false;
+static bool enableUnboxedArrays = false;
+static bool enableSharedMemory = SHARED_MEMORY_DEFAULT;
+static bool enableWasmAlwaysBaseline = false;
+#ifdef JS_GC_ZEAL
+static uint32_t gZealBits = 0;
+static uint32_t gZealFrequency = 0;
+#endif
+static bool printTiming = false;
+static const char* jsCacheDir = nullptr;
+static const char* jsCacheAsmJSPath = nullptr;
+static RCFile* gErrFile = nullptr;
+static RCFile* gOutFile = nullptr;
+static bool reportWarnings = true;
+static bool compileOnly = false;
+static bool fuzzingSafe = false;
+static bool disableOOMFunctions = false;
+static const char* moduleLoadPath = ".";
+
+#ifdef DEBUG
+static bool dumpEntrainedVariables = false;
+static bool OOM_printAllocationCount = false;
+#endif
+
+// Shell state this is only accessed on the main thread.
+bool jsCachingEnabled = false;
+mozilla::Atomic<bool> jsCacheOpened(false);
+
+static bool
+SetTimeoutValue(JSContext* cx, double t);
+
+static void
+KillWatchdog(JSContext* cx);
+
+static bool
+ScheduleWatchdog(JSContext* cx, double t);
+
+static void
+CancelExecution(JSContext* cx);
+
+static JSObject*
+NewGlobalObject(JSContext* cx, JS::CompartmentOptions& options,
+                JSPrincipals* principals);
+
+/*
+ * A toy principals type for the shell.
+ *
+ * In the shell, a principal is simply a 32-bit mask: P subsumes Q if the
+ * set bits in P are a superset of those in Q. Thus, the principal 0 is
+ * subsumed by everything, and the principal ~0 subsumes everything.
+ *
+ * As a special case, a null pointer as a principal is treated like 0xffff.
+ *
+ * The 'newGlobal' function takes an option indicating which principal the
+ * new global should have; 'evaluate' does for the new code.
+ */
+class ShellPrincipals final : public JSPrincipals {
+    uint32_t bits;
+
+    static uint32_t getBits(JSPrincipals* p) {
+        if (!p)
+            return 0xffff;
+        return static_cast<ShellPrincipals*>(p)->bits;
+    }
+
+  public:
+    explicit ShellPrincipals(uint32_t bits, int32_t refcount = 0) : bits(bits) {
+        this->refcount = refcount;
+    }
+
+    bool write(JSContext* cx, JSStructuredCloneWriter* writer) override {
+        // The shell doesn't have a read principals hook, so it doesn't really
+        // matter what we write here, but we have to write something so the
+        // fuzzer is happy.
+        return JS_WriteUint32Pair(writer, bits, 0);
+    }
+
+    static void destroy(JSPrincipals* principals) {
+        MOZ_ASSERT(principals != &fullyTrusted);
+        MOZ_ASSERT(principals->refcount == 0);
+        js_delete(static_cast<const ShellPrincipals*>(principals));
+    }
+
+    static bool subsumes(JSPrincipals* first, JSPrincipals* second) {
+        uint32_t firstBits  = getBits(first);
+        uint32_t secondBits = getBits(second);
+        return (firstBits | secondBits) == firstBits;
+    }
+
+    static JSSecurityCallbacks securityCallbacks;
+
+    // Fully-trusted principals singleton.
+    static ShellPrincipals fullyTrusted;
+};
+
+JSSecurityCallbacks ShellPrincipals::securityCallbacks = {
+    nullptr, // contentSecurityPolicyAllows
+    subsumes
+};
+
+// The fully-trusted principal subsumes all other principals.
+ShellPrincipals ShellPrincipals::fullyTrusted(-1, 1);
+
+#ifdef EDITLINE
+extern "C" {
+extern JS_EXPORT_API(char*) readline(const char* prompt);
+extern JS_EXPORT_API(void)   add_history(char* line);
+} // extern "C"
+#endif
+
+ShellContext::ShellContext(JSContext* cx)
+  : isWorker(false),
+    timeoutInterval(-1.0),
+    startTime(PRMJ_Now()),
+    serviceInterrupt(false),
+    haveInterruptFunc(false),
+    interruptFunc(cx, NullValue()),
+    lastWarningEnabled(false),
+    lastWarning(cx, NullValue()),
+#ifdef SPIDERMONKEY_PROMISE
+    promiseRejectionTrackerCallback(cx, NullValue()),
+    asyncTasks(mutexid::ShellAsyncTasks, cx),
+    drainingJobQueue(false),
+#endif // SPIDERMONKEY_PROMISE
+    watchdogLock(mutexid::ShellContextWatchdog),
+    exitCode(0),
+    quitting(false),
+    readLineBufPos(0),
+    spsProfilingStackSize(0)
+{}
+
+static ShellContext*
+GetShellContext(JSContext* cx)
+{
+    ShellContext* sc = static_cast<ShellContext*>(JS_GetContextPrivate(cx));
+    MOZ_ASSERT(sc);
+    return sc;
+}
+
+static char*
+GetLine(FILE* file, const char * prompt)
+{
+#ifdef EDITLINE
+    /*
+     * Use readline only if file is stdin, because there's no way to specify
+     * another handle.  Are other filehandles interactive?
+     */
+    if (file == stdin) {
+        char* linep = readline(prompt);
+        /*
+         * We set it to zero to avoid complaining about inappropriate ioctl
+         * for device in the case of EOF. Looks like errno == 251 if line is
+         * finished with EOF and errno == 25 (EINVAL on Mac) if there is
+         * nothing left to read.
+         */
+        if (errno == 251 || errno == 25 || errno == EINVAL)
+            errno = 0;
+        if (!linep)
+            return nullptr;
+        if (linep[0] != '\0')
+            add_history(linep);
+        return linep;
+    }
+#endif
+
+    size_t len = 0;
+    if (*prompt != '\0' && gOutFile->isOpen()) {
+        fprintf(gOutFile->fp, "%s", prompt);
+        fflush(gOutFile->fp);
+    }
+
+    size_t size = 80;
+    char* buffer = static_cast<char*>(malloc(size));
+    if (!buffer)
+        return nullptr;
+
+    char* current = buffer;
+    do {
+        while (true) {
+            if (fgets(current, size - len, file))
+                break;
+            if (errno != EINTR) {
+                free(buffer);
+                return nullptr;
+            }
+        }
+
+        len += strlen(current);
+        char* t = buffer + len - 1;
+        if (*t == '\n') {
+            /* Line was read. We remove '\n' and exit. */
+            *t = '\0';
+            return buffer;
+        }
+
+        if (len + 1 == size) {
+            size = size * 2;
+            char* tmp = static_cast<char*>(realloc(buffer, size));
+            if (!tmp) {
+                free(buffer);
+                return nullptr;
+            }
+            buffer = tmp;
+        }
+        current = buffer + len;
+    } while (true);
+    return nullptr;
+}
+
+static bool
+ShellInterruptCallback(JSContext* cx)
+{
+    ShellContext* sc = GetShellContext(cx);
+    if (!sc->serviceInterrupt)
+        return true;
+
+    // Reset serviceInterrupt. CancelExecution or InterruptIf will set it to
+    // true to distinguish watchdog or user triggered interrupts.
+    // Do this first to prevent other interrupts that may occur while the
+    // user-supplied callback is executing from re-entering the handler.
+    sc->serviceInterrupt = false;
+
+    bool result;
+    if (sc->haveInterruptFunc) {
+        bool wasAlreadyThrowing = cx->isExceptionPending();
+        JS::AutoSaveExceptionState savedExc(cx);
+        JSAutoCompartment ac(cx, &sc->interruptFunc.toObject());
+        RootedValue rval(cx);
+
+        // Report any exceptions thrown by the JS interrupt callback, but do
+        // *not* keep it on the cx. The interrupt handler is invoked at points
+        // that are not expected to throw catchable exceptions, like at
+        // JSOP_RETRVAL.
+        //
+        // If the interrupted JS code was already throwing, any exceptions
+        // thrown by the interrupt handler are silently swallowed.
+        {
+            Maybe<AutoReportException> are;
+            if (!wasAlreadyThrowing)
+                are.emplace(cx);
+            result = JS_CallFunctionValue(cx, nullptr, sc->interruptFunc,
+                                          JS::HandleValueArray::empty(), &rval);
+        }
+        savedExc.restore();
+
+        if (rval.isBoolean())
+            result = rval.toBoolean();
+        else
+            result = false;
+    } else {
+        result = false;
+    }
+
+    if (!result && sc->exitCode == 0)
+        sc->exitCode = EXITCODE_TIMEOUT;
+
+    return result;
+}
+
+/*
+ * Some UTF-8 files, notably those written using Notepad, have a Unicode
+ * Byte-Order-Mark (BOM) as their first character. This is useless (byte-order
+ * is meaningless for UTF-8) but causes a syntax error unless we skip it.
+ */
+static void
+SkipUTF8BOM(FILE* file)
+{
+    int ch1 = fgetc(file);
+    int ch2 = fgetc(file);
+    int ch3 = fgetc(file);
+
+    // Skip the BOM
+    if (ch1 == 0xEF && ch2 == 0xBB && ch3 == 0xBF)
+        return;
+
+    // No BOM - revert
+    if (ch3 != EOF)
+        ungetc(ch3, file);
+    if (ch2 != EOF)
+        ungetc(ch2, file);
+    if (ch1 != EOF)
+        ungetc(ch1, file);
+}
+
+void
+EnvironmentPreparer::invoke(HandleObject scope, Closure& closure)
+{
+    MOZ_ASSERT(!JS_IsExceptionPending(cx));
+
+    AutoCompartment ac(cx, scope);
+    AutoReportException are(cx);
+    if (!closure(cx))
+        return;
+}
+
+static MOZ_MUST_USE bool
+RunFile(JSContext* cx, const char* filename, FILE* file, bool compileOnly)
+{
+    SkipUTF8BOM(file);
+
+    // To support the UNIX #! shell hack, gobble the first line if it starts
+    // with '#'.
+    int ch = fgetc(file);
+    if (ch == '#') {
+        while ((ch = fgetc(file)) != EOF) {
+            if (ch == '\n' || ch == '\r')
+                break;
+        }
+    }
+    ungetc(ch, file);
+
+    int64_t t1 = PRMJ_Now();
+    RootedScript script(cx);
+
+    {
+        CompileOptions options(cx);
+        options.setIntroductionType("js shell file")
+               .setUTF8(true)
+               .setFileAndLine(filename, 1)
+               .setIsRunOnce(true)
+               .setNoScriptRval(true);
+
+        if (!JS::Compile(cx, options, file, &script))
+            return false;
+        MOZ_ASSERT(script);
+    }
+
+    #ifdef DEBUG
+        if (dumpEntrainedVariables)
+            AnalyzeEntrainedVariables(cx, script);
+    #endif
+    if (!compileOnly) {
+        if (!JS_ExecuteScript(cx, script))
+            return false;
+        int64_t t2 = PRMJ_Now() - t1;
+        if (printTiming)
+            printf("runtime = %.3f ms\n", double(t2) / PRMJ_USEC_PER_MSEC);
+    }
+    return true;
+}
+
+static bool
+InitModuleLoader(JSContext* cx)
+{
+    // Decompress and evaluate the embedded module loader source to initialize
+    // the module loader for the current compartment.
+
+    uint32_t srcLen = moduleloader::GetRawScriptsSize();
+    ScopedJSFreePtr<char> src(cx->pod_malloc<char>(srcLen));
+    if (!src || !DecompressString(moduleloader::compressedSources, moduleloader::GetCompressedSize(),
+                                  reinterpret_cast<unsigned char*>(src.get()), srcLen))
+    {
+        return false;
+    }
+
+    CompileOptions options(cx);
+    options.setIntroductionType("shell module loader");
+    options.setFileAndLine("shell/ModuleLoader.js", 1);
+    options.setSelfHostingMode(false);
+    options.setCanLazilyParse(false);
+    options.setVersion(JSVERSION_LATEST);
+    options.werrorOption = true;
+    options.strictOption = true;
+
+    RootedValue rv(cx);
+    return Evaluate(cx, options, src, srcLen, &rv);
+}
+
+static bool
+GetLoaderObject(JSContext* cx, MutableHandleObject resultOut)
+{
+    // Look up the |Reflect.Loader| object that has been defined by the module
+    // loader.
+
+    RootedObject object(cx, cx->global());
+    RootedValue value(cx);
+    if (!JS_GetProperty(cx, object, "Reflect", &value) || !value.isObject())
+        return false;
+
+    object = &value.toObject();
+    if (!JS_GetProperty(cx, object, "Loader", &value) || !value.isObject())
+        return false;
+
+    resultOut.set(&value.toObject());
+    return true;
+}
+
+static bool
+GetImportMethod(JSContext* cx, HandleObject loader, MutableHandleFunction resultOut)
+{
+    // Look up the module loader's |import| method.
+
+    RootedValue value(cx);
+    if (!JS_GetProperty(cx, loader, "import", &value) || !value.isObject())
+        return false;
+
+    RootedObject object(cx, &value.toObject());
+    if (!object->is<JSFunction>())
+        return false;
+
+    resultOut.set(&object->as<JSFunction>());
+    return true;
+}
+
+static MOZ_MUST_USE bool
+RunModule(JSContext* cx, const char* filename, FILE* file, bool compileOnly)
+{
+    // Execute a module by calling |Reflect.Loader.import(filename)|.
+
+    RootedObject loaderObj(cx);
+    MOZ_ALWAYS_TRUE(GetLoaderObject(cx, &loaderObj));
+
+    RootedFunction importFun(cx);
+    MOZ_ALWAYS_TRUE(GetImportMethod(cx, loaderObj, &importFun));
+
+    JS::AutoValueArray<2> args(cx);
+    args[0].setString(JS_NewStringCopyZ(cx, filename));
+    args[1].setUndefined();
+
+    RootedValue value(cx);
+    return JS_CallFunction(cx, loaderObj, importFun, args, &value);
+}
+
+#ifdef SPIDERMONKEY_PROMISE
+static JSObject*
+ShellGetIncumbentGlobalCallback(JSContext* cx)
+{
+    return JS::CurrentGlobalOrNull(cx);
+}
+
+static bool
+ShellEnqueuePromiseJobCallback(JSContext* cx, JS::HandleObject job, JS::HandleObject allocationSite,
+                               JS::HandleObject incumbentGlobal, void* data)
+{
+    ShellContext* sc = GetShellContext(cx);
+    MOZ_ASSERT(job);
+    return sc->jobQueue.append(job);
+}
+
+static bool
+ShellStartAsyncTaskCallback(JSContext* cx, JS::AsyncTask* task)
+{
+    ShellContext* sc = GetShellContext(cx);
+    task->user = sc;
+
+    ExclusiveData<ShellAsyncTasks>::Guard asyncTasks = sc->asyncTasks.lock();
+    asyncTasks->outstanding++;
+    return true;
+}
+
+static bool
+ShellFinishAsyncTaskCallback(JS::AsyncTask* task)
+{
+    ShellContext* sc = (ShellContext*)task->user;
+
+    ExclusiveData<ShellAsyncTasks>::Guard asyncTasks = sc->asyncTasks.lock();
+    MOZ_ASSERT(asyncTasks->outstanding > 0);
+    asyncTasks->outstanding--;
+    return asyncTasks->finished.append(task);
+}
+#endif // SPIDERMONKEY_PROMISE
+
+static bool
+DrainJobQueue(JSContext* cx)
+{
+#ifdef SPIDERMONKEY_PROMISE
+    ShellContext* sc = GetShellContext(cx);
+    if (sc->quitting || sc->drainingJobQueue)
+        return true;
+
+    // Wait for any outstanding async tasks to finish so that the
+    // finishedAsyncTasks list is fixed.
+    while (true) {
+        AutoLockHelperThreadState lock;
+        if (!sc->asyncTasks.lock()->outstanding)
+            break;
+        HelperThreadState().wait(lock, GlobalHelperThreadState::CONSUMER);
+    }
+
+    // Lock the whole time while copying back the asyncTasks finished queue so
+    // that any new tasks created during finish() cannot racily join the job
+    // queue.  Call finish() only thereafter, to avoid a circular mutex
+    // dependency (see also bug 1297901).
+    Vector<JS::AsyncTask*> finished(cx);
+    {
+        ExclusiveData<ShellAsyncTasks>::Guard asyncTasks = sc->asyncTasks.lock();
+        finished = Move(asyncTasks->finished);
+        asyncTasks->finished.clear();
+    }
+
+    for (JS::AsyncTask* task : finished)
+        task->finish(cx);
+
+    // It doesn't make sense for job queue draining to be reentrant. At the
+    // same time we don't want to assert against it, because that'd make
+    // drainJobQueue unsafe for fuzzers. We do want fuzzers to test this, so
+    // we simply ignore nested calls of drainJobQueue.
+    sc->drainingJobQueue = true;
+
+    RootedObject job(cx);
+    JS::HandleValueArray args(JS::HandleValueArray::empty());
+    RootedValue rval(cx);
+    // Execute jobs in a loop until we've reached the end of the queue.
+    // Since executing a job can trigger enqueuing of additional jobs,
+    // it's crucial to re-check the queue length during each iteration.
+    for (size_t i = 0; i < sc->jobQueue.length(); i++) {
+        job = sc->jobQueue[i];
+        AutoCompartment ac(cx, job);
+        {
+            AutoReportException are(cx);
+            JS::Call(cx, UndefinedHandleValue, job, args, &rval);
+        }
+        sc->jobQueue[i].set(nullptr);
+    }
+    sc->jobQueue.clear();
+    sc->drainingJobQueue = false;
+#endif // SPIDERMONKEY_PROMISE
+    return true;
+}
+
+static bool
+DrainJobQueue(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (!DrainJobQueue(cx))
+        return false;
+    args.rval().setUndefined();
+    return true;
+}
+
+#ifdef SPIDERMONKEY_PROMISE
+static void
+ForwardingPromiseRejectionTrackerCallback(JSContext* cx, JS::HandleObject promise,
+                                          PromiseRejectionHandlingState state, void* data)
+{
+    RootedValue callback(cx, GetShellContext(cx)->promiseRejectionTrackerCallback);
+    if (callback.isNull()) {
+        return;
+    }
+
+    AutoCompartment ac(cx, &callback.toObject());
+
+    FixedInvokeArgs<2> args(cx);
+    args[0].setObject(*promise);
+    args[1].setInt32(static_cast<int32_t>(state));
+
+    if (!JS_WrapValue(cx, args[0]))
+        return;
+
+    RootedValue rval(cx);
+    if (!Call(cx, callback, UndefinedHandleValue, args, &rval))
+        JS_ClearPendingException(cx);
+}
+#endif // SPIDERMONKEY_PROMISE
+
+static bool
+SetPromiseRejectionTrackerCallback(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+#ifdef SPIDERMONKEY_PROMISE
+    if (!IsCallable(args.get(0))) {
+        JS_ReportErrorASCII(cx,
+                            "setPromiseRejectionTrackerCallback expects a function as its sole "
+                            "argument");
+        return false;
+    }
+
+    GetShellContext(cx)->promiseRejectionTrackerCallback = args[0];
+    JS::SetPromiseRejectionTrackerCallback(cx, ForwardingPromiseRejectionTrackerCallback);
+
+#endif // SPIDERMONKEY_PROMISE
+    args.rval().setUndefined();
+    return true;
+}
+
+#ifdef ENABLE_INTL_API
+static bool
+AddIntlExtras(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!args.get(0).isObject()) {
+        JS_ReportErrorASCII(cx, "addIntlExtras must be passed an object");
+        return false;
+    }
+    JS::RootedObject intl(cx, &args[0].toObject());
+
+    static const JSFunctionSpec funcs[] = {
+        JS_SELF_HOSTED_FN("getCalendarInfo", "Intl_getCalendarInfo", 1, 0),
+        JS_FS_END
+    };
+
+    if (!JS_DefineFunctions(cx, intl, funcs))
+        return false;
+
+    args.rval().setUndefined();
+    return true;
+}
+#endif // ENABLE_INTL_API
+
+static bool
+EvalAndPrint(JSContext* cx, const char* bytes, size_t length,
+             int lineno, bool compileOnly)
+{
+    // Eval.
+    JS::CompileOptions options(cx);
+    options.setIntroductionType("js shell interactive")
+           .setUTF8(true)
+           .setIsRunOnce(true)
+           .setFileAndLine("typein", lineno);
+    RootedScript script(cx);
+    if (!JS::Compile(cx, options, bytes, length, &script))
+        return false;
+    if (compileOnly)
+        return true;
+    RootedValue result(cx);
+    if (!JS_ExecuteScript(cx, script, &result))
+        return false;
+
+    if (!result.isUndefined() && gOutFile->isOpen()) {
+        // Print.
+        RootedString str(cx);
+        str = JS_ValueToSource(cx, result);
+        if (!str)
+            return false;
+
+        char* utf8chars = JS_EncodeStringToUTF8(cx, str);
+        if (!utf8chars)
+            return false;
+        fprintf(gOutFile->fp, "%s\n", utf8chars);
+        JS_free(cx, utf8chars);
+    }
+    return true;
+}
+
+static MOZ_MUST_USE bool
+ReadEvalPrintLoop(JSContext* cx, FILE* in, bool compileOnly)
+{
+    ShellContext* sc = GetShellContext(cx);
+    int lineno = 1;
+    bool hitEOF = false;
+
+    do {
+        /*
+         * Accumulate lines until we get a 'compilable unit' - one that either
+         * generates an error (before running out of source) or that compiles
+         * cleanly.  This should be whenever we get a complete statement that
+         * coincides with the end of a line.
+         */
+        int startline = lineno;
+        typedef Vector<char, 32> CharBuffer;
+        RootedObject globalLexical(cx, &cx->global()->lexicalEnvironment());
+        CharBuffer buffer(cx);
+        do {
+            ScheduleWatchdog(cx, -1);
+            sc->serviceInterrupt = false;
+            errno = 0;
+
+            char* line = GetLine(in, startline == lineno ? "js> " : "");
+            if (!line) {
+                if (errno) {
+                    /*
+                     * Use Latin1 variant here because strerror(errno)'s
+                     * encoding depends on the user's C locale.
+                     */
+                    JS_ReportErrorLatin1(cx, "%s", strerror(errno));
+                    return false;
+                }
+                hitEOF = true;
+                break;
+            }
+
+            if (!buffer.append(line, strlen(line)) || !buffer.append('\n'))
+                return false;
+
+            lineno++;
+            if (!ScheduleWatchdog(cx, sc->timeoutInterval)) {
+                hitEOF = true;
+                break;
+            }
+        } while (!JS_BufferIsCompilableUnit(cx, cx->global(), buffer.begin(), buffer.length()));
+
+        if (hitEOF && buffer.empty())
+            break;
+
+        {
+            // Report exceptions but keep going.
+            AutoReportException are(cx);
+            (void) EvalAndPrint(cx, buffer.begin(), buffer.length(), startline, compileOnly);
+        }
+
+        // If a let or const fail to initialize they will remain in an unusable
+        // without further intervention. This call cleans up the global scope,
+        // setting uninitialized lexicals to undefined so that they may still
+        // be used. This behavior is _only_ acceptable in the context of the repl.
+        if (JS::ForceLexicalInitialization(cx, globalLexical) && gErrFile->isOpen()) {
+            fputs("Warning: According to the standard, after the above exception,\n"
+                  "Warning: the global bindings should be permanently uninitialized.\n"
+                  "Warning: We have non-standard-ly initialized them to `undefined`"
+                  "for you.\nWarning: This nicety only happens in the JS shell.\n",
+                  stderr);
+        }
+
+        DrainJobQueue(cx);
+
+    } while (!hitEOF && !sc->quitting);
+
+    if (gOutFile->isOpen())
+        fprintf(gOutFile->fp, "\n");
+
+    return true;
+}
+
+enum FileKind
+{
+    FileScript,
+    FileModule
+};
+
+static void
+ReportCantOpenErrorUnknownEncoding(JSContext* cx, const char* filename)
+{
+    /*
+     * Filenames are in some random system encoding.  *Probably* it's UTF-8,
+     * but no guarantees.
+     *
+     * strerror(errno)'s encoding, in contrast, depends on the user's C locale.
+     *
+     * Latin-1 is possibly wrong for both of these -- but at least if it's
+     * wrong it'll produce mojibake *safely*.  Run with Latin-1 til someone
+     * complains.
+     */
+    JS_ReportErrorNumberLatin1(cx, my_GetErrorMessage, nullptr, JSSMSG_CANT_OPEN,
+                               filename, strerror(errno));
+}
+
+static MOZ_MUST_USE bool
+Process(JSContext* cx, const char* filename, bool forceTTY, FileKind kind = FileScript)
+{
+    FILE* file;
+    if (forceTTY || !filename || strcmp(filename, "-") == 0) {
+        file = stdin;
+    } else {
+        file = fopen(filename, "r");
+        if (!file) {
+            ReportCantOpenErrorUnknownEncoding(cx, filename);
+            return false;
+        }
+    }
+    AutoCloseFile autoClose(file);
+
+    if (!forceTTY && !isatty(fileno(file))) {
+        // It's not interactive - just execute it.
+        if (kind == FileScript) {
+            if (!RunFile(cx, filename, file, compileOnly))
+                return false;
+        } else {
+            if (!RunModule(cx, filename, file, compileOnly))
+                return false;
+        }
+    } else {
+        // It's an interactive filehandle; drop into read-eval-print loop.
+        MOZ_ASSERT(kind == FileScript);
+        if (!ReadEvalPrintLoop(cx, file, compileOnly))
+            return false;
+    }
+    return true;
+}
+
+static bool
+Version(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    JSVersion origVersion = JS_GetVersion(cx);
+    if (args.length() == 0 || args[0].isUndefined()) {
+        /* Get version. */
+        args.rval().setInt32(origVersion);
+    } else {
+        /* Set version. */
+        int32_t v = -1;
+        if (args[0].isInt32()) {
+            v = args[0].toInt32();
+        } else if (args[0].isDouble()) {
+            double fv = args[0].toDouble();
+            int32_t fvi;
+            if (NumberEqualsInt32(fv, &fvi))
+                v = fvi;
+        }
+        if (v < 0 || v > JSVERSION_LATEST) {
+            JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                      "version");
+            return false;
+        }
+        JS_SetVersionForCompartment(js::GetContextCompartment(cx), JSVersion(v));
+        args.rval().setInt32(origVersion);
+    }
+    return true;
+}
+
+#ifdef XP_WIN
+#  define GET_FD_FROM_FILE(a) int(_get_osfhandle(fileno(a)))
+#else
+#  define GET_FD_FROM_FILE(a) fileno(a)
+#endif
+
+static bool
+CreateMappedArrayBuffer(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() < 1 || args.length() > 3) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                  args.length() < 1 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
+                                  "createMappedArrayBuffer");
+        return false;
+    }
+
+    RootedString rawFilenameStr(cx, JS::ToString(cx, args[0]));
+    if (!rawFilenameStr)
+        return false;
+    // It's a little bizarre to resolve relative to the script, but for testing
+    // I need a file at a known location, and the only good way I know of to do
+    // that right now is to include it in the repo alongside the test script.
+    // Bug 944164 would introduce an alternative.
+    JSString* filenameStr = ResolvePath(cx, rawFilenameStr, ScriptRelative);
+    if (!filenameStr)
+        return false;
+    JSAutoByteString filename(cx, filenameStr);
+    if (!filename)
+        return false;
+
+    uint32_t offset = 0;
+    if (args.length() >= 2) {
+        if (!JS::ToUint32(cx, args[1], &offset))
+            return false;
+    }
+
+    bool sizeGiven = false;
+    uint32_t size;
+    if (args.length() >= 3) {
+        if (!JS::ToUint32(cx, args[2], &size))
+            return false;
+        sizeGiven = true;
+        if (size == 0) {
+            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_ARRAY_LENGTH);
+            return false;
+        }
+    }
+
+    FILE* file = fopen(filename.ptr(), "r");
+    if (!file) {
+        ReportCantOpenErrorUnknownEncoding(cx, filename.ptr());
+        return false;
+    }
+    AutoCloseFile autoClose(file);
+
+    if (!sizeGiven) {
+        struct stat st;
+        if (fstat(fileno(file), &st) < 0) {
+            JS_ReportErrorASCII(cx, "Unable to stat file");
+            return false;
+        }
+        if (off_t(offset) >= st.st_size) {
+            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
+                                      JSMSG_ARG_INDEX_OUT_OF_RANGE, "2");
+            return false;
+        }
+        size = st.st_size - offset;
+    }
+
+    void* contents = JS_CreateMappedArrayBufferContents(GET_FD_FROM_FILE(file), offset, size);
+    if (!contents) {
+        JS_ReportErrorASCII(cx, "failed to allocate mapped array buffer contents (possibly due to bad alignment)");
+        return false;
+    }
+
+    RootedObject obj(cx, JS_NewMappedArrayBufferWithContents(cx, size, contents));
+    if (!obj)
+        return false;
+
+    args.rval().setObject(*obj);
+    return true;
+}
+
+#undef GET_FD_FROM_FILE
+
+static bool
+AddPromiseReactions(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 3) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                  args.length() < 3 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
+                                  "addPromiseReactions");
+        return false;
+    }
+
+    RootedObject promise(cx);
+    if (args[0].isObject())
+        promise = &args[0].toObject();
+
+    if (!promise || !JS::IsPromiseObject(promise)) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "addPromiseReactions");
+        return false;
+    }
+
+    RootedObject onResolve(cx);
+    if (args[1].isObject())
+        onResolve = &args[1].toObject();
+
+    RootedObject onReject(cx);
+    if (args[2].isObject())
+        onReject = &args[2].toObject();
+
+    if (!onResolve || !onResolve->is<JSFunction>() || !onReject || !onReject->is<JSFunction>()) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "addPromiseReactions");
+        return false;
+    }
+
+    return JS::AddPromiseReactions(cx, promise, onResolve, onReject);
+}
+
+static bool
+Options(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    JS::ContextOptions oldContextOptions = JS::ContextOptionsRef(cx);
+    for (unsigned i = 0; i < args.length(); i++) {
+        RootedString str(cx, JS::ToString(cx, args[i]));
+        if (!str)
+            return false;
+        args[i].setString(str);
+
+        JSAutoByteString opt;
+        if (!opt.encodeUtf8(cx, str))
+            return false;
+
+        if (strcmp(opt.ptr(), "strict") == 0)
+            JS::ContextOptionsRef(cx).toggleExtraWarnings();
+        else if (strcmp(opt.ptr(), "werror") == 0)
+            JS::ContextOptionsRef(cx).toggleWerror();
+        else if (strcmp(opt.ptr(), "throw_on_asmjs_validation_failure") == 0)
+            JS::ContextOptionsRef(cx).toggleThrowOnAsmJSValidationFailure();
+        else if (strcmp(opt.ptr(), "strict_mode") == 0)
+            JS::ContextOptionsRef(cx).toggleStrictMode();
+        else {
+            JS_ReportErrorUTF8(cx,
+                               "unknown option name '%s'."
+                               " The valid names are strict,"
+                               " werror, and strict_mode.",
+                               opt.ptr());
+            return false;
+        }
+    }
+
+    char* names = strdup("");
+    bool found = false;
+    if (names && oldContextOptions.extraWarnings()) {
+        names = JS_sprintf_append(names, "%s%s", found ? "," : "", "strict");
+        found = true;
+    }
+    if (names && oldContextOptions.werror()) {
+        names = JS_sprintf_append(names, "%s%s", found ? "," : "", "werror");
+        found = true;
+    }
+    if (names && oldContextOptions.throwOnAsmJSValidationFailure()) {
+        names = JS_sprintf_append(names, "%s%s", found ? "," : "", "throw_on_asmjs_validation_failure");
+        found = true;
+    }
+    if (names && oldContextOptions.strictMode()) {
+        names = JS_sprintf_append(names, "%s%s", found ? "," : "", "strict_mode");
+        found = true;
+    }
+    if (!names) {
+        JS_ReportOutOfMemory(cx);
+        return false;
+    }
+
+    JSString* str = JS_NewStringCopyZ(cx, names);
+    free(names);
+    if (!str)
+        return false;
+    args.rval().setString(str);
+    return true;
+}
+
+static bool
+LoadScript(JSContext* cx, unsigned argc, Value* vp, bool scriptRelative)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    RootedString str(cx);
+    for (unsigned i = 0; i < args.length(); i++) {
+        str = JS::ToString(cx, args[i]);
+        if (!str) {
+            JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                      "load");
+            return false;
+        }
+        str = ResolvePath(cx, str, scriptRelative ? ScriptRelative : RootRelative);
+        if (!str) {
+            JS_ReportErrorASCII(cx, "unable to resolve path");
+            return false;
+        }
+        JSAutoByteString filename(cx, str);
+        if (!filename)
+            return false;
+        errno = 0;
+        CompileOptions opts(cx);
+        opts.setIntroductionType("js shell load")
+            .setUTF8(true)
+            .setIsRunOnce(true)
+            .setNoScriptRval(true);
+        RootedScript script(cx);
+        RootedValue unused(cx);
+        if ((compileOnly && !Compile(cx, opts, filename.ptr(), &script)) ||
+            !Evaluate(cx, opts, filename.ptr(), &unused))
+        {
+            return false;
+        }
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+Load(JSContext* cx, unsigned argc, Value* vp)
+{
+    return LoadScript(cx, argc, vp, false);
+}
+
+static bool
+LoadScriptRelativeToScript(JSContext* cx, unsigned argc, Value* vp)
+{
+    return LoadScript(cx, argc, vp, true);
+}
+
+// Populate |options| with the options given by |opts|'s properties. If we
+// need to convert a filename to a C string, let fileNameBytes own the
+// bytes.
+static bool
+ParseCompileOptions(JSContext* cx, CompileOptions& options, HandleObject opts,
+                    JSAutoByteString& fileNameBytes)
+{
+    RootedValue v(cx);
+    RootedString s(cx);
+
+    if (!JS_GetProperty(cx, opts, "isRunOnce", &v))
+        return false;
+    if (!v.isUndefined())
+        options.setIsRunOnce(ToBoolean(v));
+
+    if (!JS_GetProperty(cx, opts, "noScriptRval", &v))
+        return false;
+    if (!v.isUndefined())
+        options.setNoScriptRval(ToBoolean(v));
+
+    if (!JS_GetProperty(cx, opts, "fileName", &v))
+        return false;
+    if (v.isNull()) {
+        options.setFile(nullptr);
+    } else if (!v.isUndefined()) {
+        s = ToString(cx, v);
+        if (!s)
+            return false;
+        char* fileName = fileNameBytes.encodeLatin1(cx, s);
+        if (!fileName)
+            return false;
+        options.setFile(fileName);
+    }
+
+    if (!JS_GetProperty(cx, opts, "element", &v))
+        return false;
+    if (v.isObject())
+        options.setElement(&v.toObject());
+
+    if (!JS_GetProperty(cx, opts, "elementAttributeName", &v))
+        return false;
+    if (!v.isUndefined()) {
+        s = ToString(cx, v);
+        if (!s)
+            return false;
+        options.setElementAttributeName(s);
+    }
+
+    if (!JS_GetProperty(cx, opts, "lineNumber", &v))
+        return false;
+    if (!v.isUndefined()) {
+        uint32_t u;
+        if (!ToUint32(cx, v, &u))
+            return false;
+        options.setLine(u);
+    }
+
+    if (!JS_GetProperty(cx, opts, "columnNumber", &v))
+        return false;
+    if (!v.isUndefined()) {
+        int32_t c;
+        if (!ToInt32(cx, v, &c))
+            return false;
+        options.setColumn(c);
+    }
+
+    if (!JS_GetProperty(cx, opts, "sourceIsLazy", &v))
+        return false;
+    if (v.isBoolean())
+        options.setSourceIsLazy(v.toBoolean());
+
+    return true;
+}
+
+static void
+my_LargeAllocFailCallback(void* data)
+{
+    JSContext* cx = (JSContext*)data;
+    JSRuntime* rt = cx->runtime();
+
+    if (!cx->isJSContext())
+        return;
+
+    MOZ_ASSERT(!rt->isHeapBusy());
+
+    JS::PrepareForFullGC(cx);
+    AutoKeepAtoms keepAtoms(cx->perThreadData);
+    rt->gc.gc(GC_NORMAL, JS::gcreason::SHARED_MEMORY_LIMIT);
+}
+
+static const uint32_t CacheEntry_SOURCE = 0;
+static const uint32_t CacheEntry_BYTECODE = 1;
+
+static const JSClass CacheEntry_class = {
+    "CacheEntryObject", JSCLASS_HAS_RESERVED_SLOTS(2)
+};
+
+static bool
+CacheEntry(JSContext* cx, unsigned argc, JS::Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 1 || !args[0].isString()) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "CacheEntry");
+        return false;
+    }
+
+    RootedObject obj(cx, JS_NewObject(cx, &CacheEntry_class));
+    if (!obj)
+        return false;
+
+    SetReservedSlot(obj, CacheEntry_SOURCE, args[0]);
+    SetReservedSlot(obj, CacheEntry_BYTECODE, UndefinedValue());
+    args.rval().setObject(*obj);
+    return true;
+}
+
+static bool
+CacheEntry_isCacheEntry(JSObject* cache)
+{
+    return JS_GetClass(cache) == &CacheEntry_class;
+}
+
+static JSString*
+CacheEntry_getSource(HandleObject cache)
+{
+    MOZ_ASSERT(CacheEntry_isCacheEntry(cache));
+    Value v = JS_GetReservedSlot(cache, CacheEntry_SOURCE);
+    if (!v.isString())
+        return nullptr;
+
+    return v.toString();
+}
+
+static uint8_t*
+CacheEntry_getBytecode(HandleObject cache, uint32_t* length)
+{
+    MOZ_ASSERT(CacheEntry_isCacheEntry(cache));
+    Value v = JS_GetReservedSlot(cache, CacheEntry_BYTECODE);
+    if (!v.isObject() || !v.toObject().is<ArrayBufferObject>())
+        return nullptr;
+
+    ArrayBufferObject* arrayBuffer = &v.toObject().as<ArrayBufferObject>();
+    *length = arrayBuffer->byteLength();
+    return arrayBuffer->dataPointer();
+}
+
+static bool
+CacheEntry_setBytecode(JSContext* cx, HandleObject cache, uint8_t* buffer, uint32_t length)
+{
+    MOZ_ASSERT(CacheEntry_isCacheEntry(cache));
+
+    ArrayBufferObject::BufferContents contents =
+        ArrayBufferObject::BufferContents::create<ArrayBufferObject::PLAIN>(buffer);
+    Rooted<ArrayBufferObject*> arrayBuffer(cx, ArrayBufferObject::create(cx, length, contents));
+    if (!arrayBuffer)
+        return false;
+
+    SetReservedSlot(cache, CacheEntry_BYTECODE, ObjectValue(*arrayBuffer));
+    return true;
+}
+
+static bool
+ConvertTranscodeResultToJSException(JSContext* cx, JS::TranscodeResult rv)
+{
+    switch (rv) {
+      case JS::TranscodeResult_Ok:
+        return true;
+
+      default:
+        MOZ_FALLTHROUGH;
+      case JS::TranscodeResult_Failure:
+        MOZ_ASSERT(!cx->isExceptionPending());
+        JS_ReportErrorASCII(cx, "generic warning");
+        return false;
+      case JS::TranscodeResult_Failure_BadBuildId:
+        MOZ_ASSERT(!cx->isExceptionPending());
+        JS_ReportErrorASCII(cx, "the build-id does not match");
+        return false;
+      case JS::TranscodeResult_Failure_RunOnceNotSupported:
+        MOZ_ASSERT(!cx->isExceptionPending());
+        JS_ReportErrorASCII(cx, "run-once script are not supported by XDR");
+        return false;
+      case JS::TranscodeResult_Failure_AsmJSNotSupported:
+        MOZ_ASSERT(!cx->isExceptionPending());
+        JS_ReportErrorASCII(cx, "Asm.js is not supported by XDR");
+        return false;
+      case JS::TranscodeResult_Failure_UnknownClassKind:
+        MOZ_ASSERT(!cx->isExceptionPending());
+        JS_ReportErrorASCII(cx, "Unknown class kind, go fix it.");
+        return false;
+
+      case JS::TranscodeResult_Throw:
+        MOZ_ASSERT(cx->isExceptionPending());
+        return false;
+    }
+}
+
+static bool
+Evaluate(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() < 1 || args.length() > 2) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                  args.length() < 1 ? JSSMSG_NOT_ENOUGH_ARGS : JSSMSG_TOO_MANY_ARGS,
+                                  "evaluate");
+        return false;
+    }
+
+    RootedString code(cx, nullptr);
+    RootedObject cacheEntry(cx, nullptr);
+    if (args[0].isString()) {
+        code = args[0].toString();
+    } else if (args[0].isObject() && CacheEntry_isCacheEntry(&args[0].toObject())) {
+        cacheEntry = &args[0].toObject();
+        code = CacheEntry_getSource(cacheEntry);
+    }
+
+    if (!code || (args.length() == 2 && args[1].isPrimitive())) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS, "evaluate");
+        return false;
+    }
+
+    CompileOptions options(cx);
+    JSAutoByteString fileNameBytes;
+    RootedString displayURL(cx);
+    RootedString sourceMapURL(cx);
+    RootedObject global(cx, nullptr);
+    bool catchTermination = false;
+    bool loadBytecode = false;
+    bool saveBytecode = false;
+    bool assertEqBytecode = false;
+    RootedObject callerGlobal(cx, cx->global());
+
+    options.setIntroductionType("js shell evaluate")
+           .setFileAndLine("@evaluate", 1);
+
+    global = JS_GetGlobalForObject(cx, &args.callee());
+    if (!global)
+        return false;
+
+    if (args.length() == 2) {
+        RootedObject opts(cx, &args[1].toObject());
+        RootedValue v(cx);
+
+        if (!ParseCompileOptions(cx, options, opts, fileNameBytes))
+            return false;
+
+        if (!JS_GetProperty(cx, opts, "displayURL", &v))
+            return false;
+        if (!v.isUndefined()) {
+            displayURL = ToString(cx, v);
+            if (!displayURL)
+                return false;
+        }
+
+        if (!JS_GetProperty(cx, opts, "sourceMapURL", &v))
+            return false;
+        if (!v.isUndefined()) {
+            sourceMapURL = ToString(cx, v);
+            if (!sourceMapURL)
+                return false;
+        }
+
+        if (!JS_GetProperty(cx, opts, "global", &v))
+            return false;
+        if (!v.isUndefined()) {
+            if (v.isObject()) {
+                global = js::UncheckedUnwrap(&v.toObject());
+                if (!global)
+                    return false;
+            }
+            if (!global || !(JS_GetClass(global)->flags & JSCLASS_IS_GLOBAL)) {
+                JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_UNEXPECTED_TYPE,
+                                          "\"global\" passed to evaluate()", "not a global object");
+                return false;
+            }
+        }
+
+        if (!JS_GetProperty(cx, opts, "catchTermination", &v))
+            return false;
+        if (!v.isUndefined())
+            catchTermination = ToBoolean(v);
+
+        if (!JS_GetProperty(cx, opts, "loadBytecode", &v))
+            return false;
+        if (!v.isUndefined())
+            loadBytecode = ToBoolean(v);
+
+        if (!JS_GetProperty(cx, opts, "saveBytecode", &v))
+            return false;
+        if (!v.isUndefined())
+            saveBytecode = ToBoolean(v);
+
+        if (!JS_GetProperty(cx, opts, "assertEqBytecode", &v))
+            return false;
+        if (!v.isUndefined())
+            assertEqBytecode = ToBoolean(v);
+
+        // We cannot load or save the bytecode if we have no object where the
+        // bytecode cache is stored.
+        if (loadBytecode || saveBytecode) {
+            if (!cacheEntry) {
+                JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                          "evaluate");
+                return false;
+            }
+        }
+    }
+
+    AutoStableStringChars codeChars(cx);
+    if (!codeChars.initTwoByte(cx, code))
+        return false;
+
+    JS::TranscodeBuffer loadBuffer;
+    JS::TranscodeBuffer saveBuffer;
+
+    if (loadBytecode) {
+        uint32_t loadLength = 0;
+        uint8_t* loadData = nullptr;
+        loadData = CacheEntry_getBytecode(cacheEntry, &loadLength);
+        if (!loadData)
+            return false;
+        if (!loadBuffer.append(loadData, loadLength)) {
+            JS_ReportOutOfMemory(cx);
+            return false;
+        }
+    }
+
+    {
+        JSAutoCompartment ac(cx, global);
+        RootedScript script(cx);
+
+        {
+            if (saveBytecode) {
+                if (!JS::CompartmentCreationOptionsRef(cx).cloneSingletons()) {
+                    JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                              JSSMSG_CACHE_SINGLETON_FAILED);
+                    return false;
+                }
+
+                // cloneSingletons implies that singletons are used as template objects.
+                MOZ_ASSERT(JS::CompartmentBehaviorsRef(cx).getSingletonsAsTemplates());
+            }
+
+            if (loadBytecode) {
+                JS::TranscodeResult rv = JS::DecodeScript(cx, loadBuffer, &script);
+                if (!ConvertTranscodeResultToJSException(cx, rv))
+                    return false;
+            } else {
+                mozilla::Range<const char16_t> chars = codeChars.twoByteRange();
+                (void) JS::Compile(cx, options, chars.begin().get(), chars.length(), &script);
+            }
+
+            if (!script)
+                return false;
+        }
+
+        if (displayURL && !script->scriptSource()->hasDisplayURL()) {
+            JSFlatString* flat = displayURL->ensureFlat(cx);
+            if (!flat)
+                return false;
+
+            AutoStableStringChars chars(cx);
+            if (!chars.initTwoByte(cx, flat))
+                return false;
+
+            const char16_t* durl = chars.twoByteRange().begin().get();
+            if (!script->scriptSource()->setDisplayURL(cx, durl))
+                return false;
+        }
+        if (sourceMapURL && !script->scriptSource()->hasSourceMapURL()) {
+            JSFlatString* flat = sourceMapURL->ensureFlat(cx);
+            if (!flat)
+                return false;
+
+            AutoStableStringChars chars(cx);
+            if (!chars.initTwoByte(cx, flat))
+                return false;
+
+            const char16_t* smurl = chars.twoByteRange().begin().get();
+            if (!script->scriptSource()->setSourceMapURL(cx, smurl))
+                return false;
+        }
+        if (!JS_ExecuteScript(cx, script, args.rval())) {
+            if (catchTermination && !JS_IsExceptionPending(cx)) {
+                JSAutoCompartment ac1(cx, callerGlobal);
+                JSString* str = JS_NewStringCopyZ(cx, "terminated");
+                if (!str)
+                    return false;
+                args.rval().setString(str);
+                return true;
+            }
+            return false;
+        }
+
+        if (saveBytecode) {
+            JS::TranscodeResult rv = JS::EncodeScript(cx, saveBuffer, script);
+            if (!ConvertTranscodeResultToJSException(cx, rv))
+                return false;
+        }
+    }
+
+    if (saveBytecode) {
+        // If we are both loading and saving, we assert that we are going to
+        // replace the current bytecode by the same stream of bytes.
+        if (loadBytecode && assertEqBytecode) {
+            if (saveBuffer.length() != loadBuffer.length()) {
+                char loadLengthStr[16];
+                SprintfLiteral(loadLengthStr, "%" PRIuSIZE, loadBuffer.length());
+                char saveLengthStr[16];
+                SprintfLiteral(saveLengthStr,"%" PRIuSIZE, saveBuffer.length());
+
+                JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_CACHE_EQ_SIZE_FAILED,
+                                          loadLengthStr, saveLengthStr);
+                return false;
+            }
+
+            if (!PodEqual(loadBuffer.begin(), saveBuffer.begin(), loadBuffer.length())) {
+                JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                          JSSMSG_CACHE_EQ_CONTENT_FAILED);
+                return false;
+            }
+        }
+
+        size_t saveLength = saveBuffer.length();
+        if (saveLength >= INT32_MAX) {
+            JS_ReportErrorASCII(cx, "Cannot save large cache entry content");
+            return false;
+        }
+        uint8_t* saveData = saveBuffer.extractOrCopyRawBuffer();
+        if (!CacheEntry_setBytecode(cx, cacheEntry, saveData, saveLength)) {
+            js_free(saveData);
+            return false;
+        }
+    }
+
+    return JS_WrapValue(cx, args.rval());
+}
+
+JSString*
+js::shell::FileAsString(JSContext* cx, JS::HandleString pathnameStr)
+{
+    JSAutoByteString pathname(cx, pathnameStr);
+    if (!pathname)
+        return nullptr;
+
+    FILE* file;
+
+    file = fopen(pathname.ptr(), "rb");
+    if (!file) {
+        ReportCantOpenErrorUnknownEncoding(cx, pathname.ptr());
+        return nullptr;
+    }
+
+    AutoCloseFile autoClose(file);
+
+    if (fseek(file, 0, SEEK_END) != 0) {
+        pathname.clear();
+        if (!pathname.encodeUtf8(cx, pathnameStr))
+            return nullptr;
+        JS_ReportErrorUTF8(cx, "can't seek end of %s", pathname.ptr());
+        return nullptr;
+    }
+
+    size_t len = ftell(file);
+    if (fseek(file, 0, SEEK_SET) != 0) {
+        pathname.clear();
+        if (!pathname.encodeUtf8(cx, pathnameStr))
+            return nullptr;
+        JS_ReportErrorUTF8(cx, "can't seek start of %s", pathname.ptr());
+        return nullptr;
+    }
+
+    UniqueChars buf(static_cast<char*>(js_malloc(len + 1)));
+    if (!buf)
+        return nullptr;
+
+    size_t cc = fread(buf.get(), 1, len, file);
+    if (cc != len) {
+        if (ptrdiff_t(cc) < 0) {
+            ReportCantOpenErrorUnknownEncoding(cx, pathname.ptr());
+        } else {
+            pathname.clear();
+            if (!pathname.encodeUtf8(cx, pathnameStr))
+                return nullptr;
+            JS_ReportErrorUTF8(cx, "can't read %s: short read", pathname.ptr());
+        }
+        return nullptr;
+    }
+
+    UniqueTwoByteChars ucbuf(
+        JS::LossyUTF8CharsToNewTwoByteCharsZ(cx, JS::UTF8Chars(buf.get(), len), &len).get()
+    );
+    if (!ucbuf) {
+        pathname.clear();
+        if (!pathname.encodeUtf8(cx, pathnameStr))
+            return nullptr;
+        JS_ReportErrorUTF8(cx, "Invalid UTF-8 in file '%s'", pathname.ptr());
+        return nullptr;
+    }
+
+    return JS_NewUCStringCopyN(cx, ucbuf.get(), len);
+}
+
+/*
+ * Function to run scripts and return compilation + execution time. Semantics
+ * are closely modelled after the equivalent function in WebKit, as this is used
+ * to produce benchmark timings by SunSpider.
+ */
+static bool
+Run(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() != 1) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS, "run");
+        return false;
+    }
+
+    RootedString str(cx, JS::ToString(cx, args[0]));
+    if (!str)
+        return false;
+    args[0].setString(str);
+
+    str = FileAsString(cx, str);
+    if (!str)
+        return false;
+
+    AutoStableStringChars chars(cx);
+    if (!chars.initTwoByte(cx, str))
+        return false;
+
+    const char16_t* ucbuf = chars.twoByteRange().begin().get();
+    size_t buflen = str->length();
+
+    RootedScript script(cx);
+    int64_t startClock = PRMJ_Now();
+    {
+        /* FIXME: This should use UTF-8 (bug 987069). */
+        JSAutoByteString filename(cx, str);
+        if (!filename)
+            return false;
+
+        JS::CompileOptions options(cx);
+        options.setIntroductionType("js shell run")
+               .setFileAndLine(filename.ptr(), 1)
+               .setIsRunOnce(true)
+               .setNoScriptRval(true);
+        if (!JS_CompileUCScript(cx, ucbuf, buflen, options, &script))
+            return false;
+    }
+
+    if (!JS_ExecuteScript(cx, script))
+        return false;
+
+    int64_t endClock = PRMJ_Now();
+
+    args.rval().setDouble((endClock - startClock) / double(PRMJ_USEC_PER_MSEC));
+    return true;
+}
+
+/*
+ * function readline()
+ * Provides a hook for scripts to read a line from stdin.
+ */
+static bool
+ReadLine(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+#define BUFSIZE 256
+    FILE* from = stdin;
+    size_t buflength = 0;
+    size_t bufsize = BUFSIZE;
+    char* buf = (char*) JS_malloc(cx, bufsize);
+    if (!buf)
+        return false;
+
+    bool sawNewline = false;
+    size_t gotlength;
+    while ((gotlength = js_fgets(buf + buflength, bufsize - buflength, from)) > 0) {
+        buflength += gotlength;
+
+        /* Are we done? */
+        if (buf[buflength - 1] == '\n') {
+            buf[buflength - 1] = '\0';
+            sawNewline = true;
+            break;
+        } else if (buflength < bufsize - 1) {
+            break;
+        }
+
+        /* Else, grow our buffer for another pass. */
+        char* tmp;
+        bufsize *= 2;
+        if (bufsize > buflength) {
+            tmp = static_cast<char*>(JS_realloc(cx, buf, bufsize / 2, bufsize));
+        } else {
+            JS_ReportOutOfMemory(cx);
+            tmp = nullptr;
+        }
+
+        if (!tmp) {
+            JS_free(cx, buf);
+            return false;
+        }
+
+        buf = tmp;
+    }
+
+    /* Treat the empty string specially. */
+    if (buflength == 0) {
+        args.rval().set(feof(from) ? NullValue() : JS_GetEmptyStringValue(cx));
+        JS_free(cx, buf);
+        return true;
+    }
+
+    /* Shrink the buffer to the real size. */
+    char* tmp = static_cast<char*>(JS_realloc(cx, buf, bufsize, buflength));
+    if (!tmp) {
+        JS_free(cx, buf);
+        return false;
+    }
+
+    buf = tmp;
+
+    /*
+     * Turn buf into a JSString. Note that buflength includes the trailing null
+     * character.
+     */
+    JSString* str = JS_NewStringCopyN(cx, buf, sawNewline ? buflength - 1 : buflength);
+    JS_free(cx, buf);
+    if (!str)
+        return false;
+
+    args.rval().setString(str);
+    return true;
+}
+
+/*
+ * function readlineBuf()
+ * Provides a hook for scripts to emulate readline() using a string object.
+ */
+static bool
+ReadLineBuf(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    ShellContext* sc = GetShellContext(cx);
+
+    if (!args.length()) {
+        if (!sc->readLineBuf) {
+            JS_ReportErrorASCII(cx, "No source buffer set. You must initially "
+                                "call readlineBuf with an argument.");
+            return false;
+        }
+
+        char* currentBuf = sc->readLineBuf.get() + sc->readLineBufPos;
+        size_t buflen = strlen(currentBuf);
+
+        if (!buflen) {
+            args.rval().setNull();
+            return true;
+        }
+
+        size_t len = 0;
+        while(len < buflen) {
+            if (currentBuf[len] == '\n')
+                break;
+            len++;
+        }
+
+        JSString* str = JS_NewStringCopyN(cx, currentBuf, len);
+        if (!str)
+            return false;
+
+        if (currentBuf[len] == '\0')
+            sc->readLineBufPos += len;
+        else
+            sc->readLineBufPos += len + 1;
+
+        args.rval().setString(str);
+        return true;
+    }
+
+    if (args.length() == 1) {
+        if (sc->readLineBuf)
+            sc->readLineBuf.reset();
+
+        RootedString str(cx, JS::ToString(cx, args[0]));
+        if (!str)
+            return false;
+        sc->readLineBuf = UniqueChars(JS_EncodeStringToUTF8(cx, str));
+        if (!sc->readLineBuf)
+            return false;
+
+        sc->readLineBufPos = 0;
+        return true;
+    }
+
+    JS_ReportErrorASCII(cx, "Must specify at most one argument");
+    return false;
+}
+
+static bool
+PutStr(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 0) {
+        if (!gOutFile->isOpen()) {
+            JS_ReportErrorASCII(cx, "output file is closed");
+            return false;
+        }
+
+        RootedString str(cx, JS::ToString(cx, args[0]));
+        if (!str)
+            return false;
+        char* bytes = JS_EncodeStringToUTF8(cx, str);
+        if (!bytes)
+            return false;
+        fputs(bytes, gOutFile->fp);
+        JS_free(cx, bytes);
+        fflush(gOutFile->fp);
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+Now(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    double now = PRMJ_Now() / double(PRMJ_USEC_PER_MSEC);
+    args.rval().setDouble(now);
+    return true;
+}
+
+static bool
+PrintInternal(JSContext* cx, const CallArgs& args, RCFile* file)
+{
+    if (!file->isOpen()) {
+        JS_ReportErrorASCII(cx, "output file is closed");
+        return false;
+    }
+
+    for (unsigned i = 0; i < args.length(); i++) {
+        RootedString str(cx, JS::ToString(cx, args[i]));
+        if (!str)
+            return false;
+        char* bytes = JS_EncodeStringToUTF8(cx, str);
+        if (!bytes)
+            return false;
+        fprintf(file->fp, "%s%s", i ? " " : "", bytes);
+        JS_free(cx, bytes);
+    }
+
+    fputc('\n', file->fp);
+    fflush(file->fp);
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+Print(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return PrintInternal(cx, args, gOutFile);
+}
+
+static bool
+PrintErr(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    return PrintInternal(cx, args, gErrFile);
+}
+
+static bool
+Help(JSContext* cx, unsigned argc, Value* vp);
+
+static bool
+Quit(JSContext* cx, unsigned argc, Value* vp)
+{
+    ShellContext* sc = GetShellContext(cx);
+
+#ifdef JS_MORE_DETERMINISTIC
+    // Print a message to stderr in more-deterministic builds to help jsfunfuzz
+    // find uncatchable-exception bugs.
+    fprintf(stderr, "quit called\n");
+#endif
+
+    CallArgs args = CallArgsFromVp(argc, vp);
+    int32_t code;
+    if (!ToInt32(cx, args.get(0), &code))
+        return false;
+
+    // The fuzzers check the shell's exit code and assume a value >= 128 means
+    // the process crashed (for instance, SIGSEGV will result in code 139). On
+    // POSIX platforms, the exit code is 8-bit and negative values can also
+    // result in an exit code >= 128. We restrict the value to range [0, 127] to
+    // avoid false positives.
+    if (code < 0 || code >= 128) {
+        JS_ReportErrorASCII(cx, "quit exit code should be in range 0-127");
+        return false;
+    }
+
+    sc->exitCode = code;
+    sc->quitting = true;
+    return false;
+}
+
+static bool
+StartTimingMutator(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() > 0) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_TOO_MANY_ARGS,
+                                  "startTimingMutator");
+        return false;
+    }
+
+    if (!cx->runtime()->gc.stats.startTimingMutator()) {
+        JS_ReportErrorASCII(cx, "StartTimingMutator should only be called from outside of GC");
+        return false;
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+StopTimingMutator(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() > 0) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_TOO_MANY_ARGS,
+                                  "stopTimingMutator");
+        return false;
+    }
+
+    double mutator_ms, gc_ms;
+    if (!cx->runtime()->gc.stats.stopTimingMutator(mutator_ms, gc_ms)) {
+        JS_ReportErrorASCII(cx, "stopTimingMutator called when not timing the mutator");
+        return false;
+    }
+    double total_ms = mutator_ms + gc_ms;
+    if (total_ms > 0 && gOutFile->isOpen()) {
+        fprintf(gOutFile->fp, "Mutator: %.3fms (%.1f%%), GC: %.3fms (%.1f%%)\n",
+                mutator_ms, mutator_ms / total_ms * 100.0, gc_ms, gc_ms / total_ms * 100.0);
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static const char*
+ToSource(JSContext* cx, MutableHandleValue vp, JSAutoByteString* bytes)
+{
+    JSString* str = JS_ValueToSource(cx, vp);
+    if (str) {
+        vp.setString(str);
+        if (bytes->encodeLatin1(cx, str))
+            return bytes->ptr();
+    }
+    JS_ClearPendingException(cx);
+    return "<<error converting value to string>>";
+}
+
+static bool
+AssertEq(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!(args.length() == 2 || (args.length() == 3 && args[2].isString()))) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr,
+                                  (args.length() < 2)
+                                  ? JSSMSG_NOT_ENOUGH_ARGS
+                                  : (args.length() == 3)
+                                  ? JSSMSG_INVALID_ARGS
+                                  : JSSMSG_TOO_MANY_ARGS,
+                                  "assertEq");
+        return false;
+    }
+
+    bool same;
+    if (!JS_SameValue(cx, args[0], args[1], &same))
+        return false;
+    if (!same) {
+        JSAutoByteString bytes0, bytes1;
+        const char* actual = ToSource(cx, args[0], &bytes0);
+        const char* expected = ToSource(cx, args[1], &bytes1);
+        if (args.length() == 2) {
+            JS_ReportErrorNumberLatin1(cx, my_GetErrorMessage, nullptr, JSSMSG_ASSERT_EQ_FAILED,
+                                       actual, expected);
+        } else {
+            JSAutoByteString bytes2(cx, args[2].toString());
+            if (!bytes2)
+                return false;
+            JS_ReportErrorNumberLatin1(cx, my_GetErrorMessage, nullptr,
+                                       JSSMSG_ASSERT_EQ_FAILED_MSG,
+                                       actual, expected, bytes2.ptr());
+        }
+        return false;
+    }
+    args.rval().setUndefined();
+    return true;
+}
+
+static JSScript*
+ValueToScript(JSContext* cx, HandleValue v, JSFunction** funp = nullptr)
+{
+    if (v.isString()) {
+        // To convert a string to a script, compile it. Parse it as an ES6 Program.
+        RootedLinearString linearStr(cx, StringToLinearString(cx, v.toString()));
+        if (!linearStr)
+            return nullptr;
+        size_t len = GetLinearStringLength(linearStr);
+        AutoStableStringChars linearChars(cx);
+        if (!linearChars.initTwoByte(cx, linearStr))
+            return nullptr;
+        const char16_t* chars = linearChars.twoByteRange().begin().get();
+
+        RootedScript script(cx);
+        CompileOptions options(cx);
+        if (!JS::Compile(cx, options, chars, len, &script))
+            return nullptr;
+        return script;
+    }
+
+    RootedFunction fun(cx, JS_ValueToFunction(cx, v));
+    if (!fun)
+        return nullptr;
+
+    // Unwrap bound functions.
+    while (fun->isBoundFunction()) {
+        JSObject* target = fun->getBoundFunctionTarget();
+        if (target && target->is<JSFunction>())
+            fun = &target->as<JSFunction>();
+        else
+            break;
+    }
+
+    // Get unwrapped async function.
+    if (IsWrappedAsyncFunction(fun))
+        fun = GetUnwrappedAsyncFunction(fun);
+
+    if (!fun->isInterpreted()) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_SCRIPTS_ONLY);
+        return nullptr;
+    }
+
+    JSScript* script = fun->getOrCreateScript(cx);
+    if (!script)
+        return nullptr;
+
+    if (funp)
+        *funp = fun;
+
+    return script;
+}
+
+static JSScript*
+GetTopScript(JSContext* cx)
+{
+    NonBuiltinScriptFrameIter iter(cx);
+    return iter.done() ? nullptr : iter.script();
+}
+
+static bool
+GetScriptAndPCArgs(JSContext* cx, CallArgs& args, MutableHandleScript scriptp,
+                   int32_t* ip)
+{
+    RootedScript script(cx, GetTopScript(cx));
+    *ip = 0;
+    if (!args.get(0).isUndefined()) {
+        HandleValue v = args[0];
+        unsigned intarg = 0;
+        if (v.isObject() &&
+            JS_GetClass(&v.toObject()) == Jsvalify(&JSFunction::class_)) {
+            script = ValueToScript(cx, v);
+            if (!script)
+                return false;
+            intarg++;
+        }
+        if (!args.get(intarg).isUndefined()) {
+            if (!JS::ToInt32(cx, args[intarg], ip))
+                return false;
+            if ((uint32_t)*ip >= script->length()) {
+                JS_ReportErrorASCII(cx, "Invalid PC");
+                return false;
+            }
+        }
+    }
+
+    scriptp.set(script);
+
+    return true;
+}
+
+static bool
+LineToPC(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() == 0) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_LINE2PC_USAGE);
+        return false;
+    }
+
+    RootedScript script(cx, GetTopScript(cx));
+    int32_t lineArg = 0;
+    if (args[0].isObject() && args[0].toObject().is<JSFunction>()) {
+        script = ValueToScript(cx, args[0]);
+        if (!script)
+            return false;
+        lineArg++;
+    }
+
+    uint32_t lineno;
+    if (!ToUint32(cx, args.get(lineArg), &lineno))
+         return false;
+
+    jsbytecode* pc = LineNumberToPC(script, lineno);
+    if (!pc)
+        return false;
+    args.rval().setInt32(script->pcToOffset(pc));
+    return true;
+}
+
+static bool
+PCToLine(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedScript script(cx);
+    int32_t i;
+    unsigned lineno;
+
+    if (!GetScriptAndPCArgs(cx, args, &script, &i))
+        return false;
+    lineno = PCToLineNumber(script, script->offsetToPC(i));
+    if (!lineno)
+        return false;
+    args.rval().setInt32(lineno);
+    return true;
+}
+
+#ifdef DEBUG
+
+static void
+UpdateSwitchTableBounds(JSContext* cx, HandleScript script, unsigned offset,
+                        unsigned* start, unsigned* end)
+{
+    jsbytecode* pc;
+    JSOp op;
+    ptrdiff_t jmplen;
+    int32_t low, high, n;
+
+    pc = script->offsetToPC(offset);
+    op = JSOp(*pc);
+    switch (op) {
+      case JSOP_TABLESWITCH:
+        jmplen = JUMP_OFFSET_LEN;
+        pc += jmplen;
+        low = GET_JUMP_OFFSET(pc);
+        pc += JUMP_OFFSET_LEN;
+        high = GET_JUMP_OFFSET(pc);
+        pc += JUMP_OFFSET_LEN;
+        n = high - low + 1;
+        break;
+
+      default:
+        /* [condswitch] switch does not have any jump or lookup tables. */
+        MOZ_ASSERT(op == JSOP_CONDSWITCH);
+        return;
+    }
+
+    *start = script->pcToOffset(pc);
+    *end = *start + (unsigned)(n * jmplen);
+}
+
+static MOZ_MUST_USE bool
+SrcNotes(JSContext* cx, HandleScript script, Sprinter* sp)
+{
+    if (sp->put("\nSource notes:\n") < 0 ||
+        !sp->jsprintf("%4s %4s %5s %6s %-8s %s\n",
+                      "ofs", "line", "pc", "delta", "desc", "args") ||
+        sp->put("---- ---- ----- ------ -------- ------\n") < 0)
+    {
+        return false;
+    }
+
+    unsigned offset = 0;
+    unsigned colspan = 0;
+    unsigned lineno = script->lineno();
+    jssrcnote* notes = script->notes();
+    unsigned switchTableEnd = 0, switchTableStart = 0;
+    for (jssrcnote* sn = notes; !SN_IS_TERMINATOR(sn); sn = SN_NEXT(sn)) {
+        unsigned delta = SN_DELTA(sn);
+        offset += delta;
+        SrcNoteType type = (SrcNoteType) SN_TYPE(sn);
+        const char* name = js_SrcNoteSpec[type].name;
+        if (!sp->jsprintf("%3u: %4u %5u [%4u] %-8s",
+                          unsigned(sn - notes), lineno, offset, delta, name))
+        {
+            return false;
+        }
+
+        switch (type) {
+          case SRC_NULL:
+          case SRC_IF:
+          case SRC_CONTINUE:
+          case SRC_BREAK:
+          case SRC_BREAK2LABEL:
+          case SRC_SWITCHBREAK:
+          case SRC_ASSIGNOP:
+          case SRC_XDELTA:
+            break;
+
+          case SRC_COLSPAN:
+            colspan = SN_OFFSET_TO_COLSPAN(GetSrcNoteOffset(sn, 0));
+            if (!sp->jsprintf("%d", colspan))
+                return false;
+            break;
+
+          case SRC_SETLINE:
+            lineno = GetSrcNoteOffset(sn, 0);
+            if (!sp->jsprintf(" lineno %u", lineno))
+                return false;
+            break;
+
+          case SRC_NEWLINE:
+            ++lineno;
+            break;
+
+          case SRC_FOR:
+            if (!sp->jsprintf(" cond %u update %u tail %u",
+                              unsigned(GetSrcNoteOffset(sn, 0)),
+                              unsigned(GetSrcNoteOffset(sn, 1)),
+                              unsigned(GetSrcNoteOffset(sn, 2))))
+            {
+                return false;
+            }
+            break;
+
+          case SRC_IF_ELSE:
+            if (!sp->jsprintf(" else %u", unsigned(GetSrcNoteOffset(sn, 0))))
+                return false;
+            break;
+
+          case SRC_FOR_IN:
+          case SRC_FOR_OF:
+            if (!sp->jsprintf(" closingjump %u", unsigned(GetSrcNoteOffset(sn, 0))))
+                return false;
+            break;
+
+          case SRC_COND:
+          case SRC_WHILE:
+          case SRC_NEXTCASE:
+            if (!sp->jsprintf(" offset %u", unsigned(GetSrcNoteOffset(sn, 0))))
+                return false;
+            break;
+
+          case SRC_TABLESWITCH: {
+            JSOp op = JSOp(script->code()[offset]);
+            MOZ_ASSERT(op == JSOP_TABLESWITCH);
+            if (!sp->jsprintf(" length %u", unsigned(GetSrcNoteOffset(sn, 0))))
+                return false;
+            UpdateSwitchTableBounds(cx, script, offset,
+                                    &switchTableStart, &switchTableEnd);
+            break;
+          }
+          case SRC_CONDSWITCH: {
+            JSOp op = JSOp(script->code()[offset]);
+            MOZ_ASSERT(op == JSOP_CONDSWITCH);
+            if (!sp->jsprintf(" length %u", unsigned(GetSrcNoteOffset(sn, 0))))
+                return false;
+            if (unsigned caseOff = (unsigned) GetSrcNoteOffset(sn, 1)) {
+                if (!sp->jsprintf(" first case offset %u", caseOff))
+                    return false;
+            }
+            UpdateSwitchTableBounds(cx, script, offset,
+                                    &switchTableStart, &switchTableEnd);
+            break;
+          }
+
+          case SRC_TRY:
+            MOZ_ASSERT(JSOp(script->code()[offset]) == JSOP_TRY);
+            if (!sp->jsprintf(" offset to jump %u", unsigned(GetSrcNoteOffset(sn, 0))))
+                return false;
+            break;
+
+          default:
+            MOZ_ASSERT_UNREACHABLE("unrecognized srcnote");
+        }
+        if (sp->put("\n") < 0)
+            return false;
+    }
+
+    return true;
+}
+
+static bool
+Notes(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    Sprinter sprinter(cx);
+    if (!sprinter.init())
+        return false;
+
+    for (unsigned i = 0; i < args.length(); i++) {
+        RootedScript script (cx, ValueToScript(cx, args[i]));
+        if (!script)
+            return false;
+
+        if (!SrcNotes(cx, script, &sprinter))
+            return false;
+    }
+
+    JSString* str = JS_NewStringCopyZ(cx, sprinter.string());
+    if (!str)
+        return false;
+    args.rval().setString(str);
+    return true;
+}
+
+JS_STATIC_ASSERT(JSTRY_CATCH == 0);
+JS_STATIC_ASSERT(JSTRY_FINALLY == 1);
+JS_STATIC_ASSERT(JSTRY_FOR_IN == 2);
+
+static const char* const TryNoteNames[] = { "catch", "finally", "for-in", "for-of", "loop" };
+
+static MOZ_MUST_USE bool
+TryNotes(JSContext* cx, HandleScript script, Sprinter* sp)
+{
+    if (!script->hasTrynotes())
+        return true;
+
+    if (sp->put("\nException table:\nkind      stack    start      end\n") < 0)
+        return false;
+
+    JSTryNote* tn = script->trynotes()->vector;
+    JSTryNote* tnlimit = tn + script->trynotes()->length;
+    do {
+        MOZ_ASSERT(tn->kind < ArrayLength(TryNoteNames));
+        uint8_t startOff = script->pcToOffset(script->main()) + tn->start;
+        if (!sp->jsprintf(" %-7s %6u %8u %8u\n",
+                          TryNoteNames[tn->kind], tn->stackDepth,
+                          startOff, startOff + tn->length))
+        {
+            return false;
+        }
+    } while (++tn != tnlimit);
+    return true;
+}
+
+static MOZ_MUST_USE bool
+ScopeNotes(JSContext* cx, HandleScript script, Sprinter* sp)
+{
+    if (!script->hasScopeNotes())
+        return true;
+
+    if (sp->put("\nScope notes:\n   index   parent    start      end\n") < 0)
+        return false;
+
+    ScopeNoteArray* notes = script->scopeNotes();
+    for (uint32_t i = 0; i < notes->length; i++) {
+        const ScopeNote* note = &notes->vector[i];
+        if (note->index == ScopeNote::NoScopeIndex) {
+            if (!sp->jsprintf("%8s ", "(none)"))
+                return false;
+        } else {
+            if (!sp->jsprintf("%8u ", note->index))
+                return false;
+        }
+        if (note->parent == ScopeNote::NoScopeIndex) {
+            if (!sp->jsprintf("%8s ", "(none)"))
+                return false;
+        } else {
+            if (!sp->jsprintf("%8u ", note->parent))
+                return false;
+        }
+        if (!sp->jsprintf("%8u %8u\n", note->start, note->start + note->length))
+            return false;
+    }
+    return true;
+}
+
+static MOZ_MUST_USE bool
+DisassembleScript(JSContext* cx, HandleScript script, HandleFunction fun,
+                  bool lines, bool recursive, bool sourceNotes, Sprinter* sp)
+{
+    if (fun) {
+        if (sp->put("flags:") < 0)
+            return false;
+        if (fun->isLambda()) {
+            if (sp->put(" LAMBDA") < 0)
+                return false;
+        }
+        if (fun->needsCallObject()) {
+            if (sp->put(" NEEDS_CALLOBJECT") < 0)
+                return false;
+        }
+        if (fun->needsExtraBodyVarEnvironment()) {
+            if (sp->put(" NEEDS_EXTRABODYVARENV") < 0)
+                return false;
+        }
+        if (fun->needsNamedLambdaEnvironment()) {
+            if (sp->put(" NEEDS_NAMEDLAMBDAENV") < 0)
+                return false;
+        }
+        if (fun->isConstructor()) {
+            if (sp->put(" CONSTRUCTOR") < 0)
+                return false;
+        }
+        if (fun->isExprBody()) {
+            if (sp->put(" EXPRESSION_CLOSURE") < 0)
+                return false;
+        }
+        if (fun->isSelfHostedBuiltin()) {
+            if (sp->put(" SELF_HOSTED") < 0)
+                return false;
+        }
+        if (fun->isArrow()) {
+            if (sp->put(" ARROW") < 0)
+                return false;
+        }
+        if (sp->put("\n") < 0)
+            return false;
+    }
+
+    if (!Disassemble(cx, script, lines, sp))
+        return false;
+    if (sourceNotes) {
+        if (!SrcNotes(cx, script, sp))
+            return false;
+    }
+    if (!TryNotes(cx, script, sp))
+        return false;
+    if (!ScopeNotes(cx, script, sp))
+        return false;
+
+    if (recursive && script->hasObjects()) {
+        ObjectArray* objects = script->objects();
+        for (unsigned i = 0; i != objects->length; ++i) {
+            JSObject* obj = objects->vector[i];
+            if (obj->is<JSFunction>()) {
+                if (sp->put("\n") < 0)
+                    return false;
+
+                RootedFunction fun(cx, &obj->as<JSFunction>());
+                if (fun->isInterpreted()) {
+                    RootedScript script(cx, fun->getOrCreateScript(cx));
+                    if (script) {
+                        if (!DisassembleScript(cx, script, fun, lines, recursive, sourceNotes, sp))
+                            return false;
+                    }
+                } else {
+                    if (sp->put("[native code]\n") < 0)
+                        return false;
+                }
+            }
+        }
+    }
+
+    return true;
+}
+
+namespace {
+
+struct DisassembleOptionParser {
+    unsigned argc;
+    Value* argv;
+    bool lines;
+    bool recursive;
+    bool sourceNotes;
+
+    DisassembleOptionParser(unsigned argc, Value* argv)
+      : argc(argc), argv(argv), lines(false), recursive(false), sourceNotes(true) {}
+
+    bool parse(JSContext* cx) {
+        /* Read options off early arguments */
+        while (argc > 0 && argv[0].isString()) {
+            JSString* str = argv[0].toString();
+            JSFlatString* flatStr = JS_FlattenString(cx, str);
+            if (!flatStr)
+                return false;
+            if (JS_FlatStringEqualsAscii(flatStr, "-l"))
+                lines = true;
+            else if (JS_FlatStringEqualsAscii(flatStr, "-r"))
+                recursive = true;
+            else if (JS_FlatStringEqualsAscii(flatStr, "-S"))
+                sourceNotes = false;
+            else
+                break;
+            argv++, argc--;
+        }
+        return true;
+    }
+};
+
+} /* anonymous namespace */
+
+static bool
+DisassembleToSprinter(JSContext* cx, unsigned argc, Value* vp, Sprinter* sprinter)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    DisassembleOptionParser p(args.length(), args.array());
+    if (!p.parse(cx))
+        return false;
+
+    if (p.argc == 0) {
+        /* Without arguments, disassemble the current script. */
+        RootedScript script(cx, GetTopScript(cx));
+        if (script) {
+            JSAutoCompartment ac(cx, script);
+            if (!Disassemble(cx, script, p.lines, sprinter))
+                return false;
+            if (!SrcNotes(cx, script, sprinter))
+                return false;
+            if (!TryNotes(cx, script, sprinter))
+                return false;
+            if (!ScopeNotes(cx, script, sprinter))
+                return false;
+        }
+    } else {
+        for (unsigned i = 0; i < p.argc; i++) {
+            RootedFunction fun(cx);
+            RootedScript script(cx);
+            RootedValue value(cx, p.argv[i]);
+            if (value.isObject() && value.toObject().is<ModuleObject>())
+                script = value.toObject().as<ModuleObject>().script();
+            else
+                script = ValueToScript(cx, value, fun.address());
+            if (!script)
+                return false;
+            if (!DisassembleScript(cx, script, fun, p.lines, p.recursive, p.sourceNotes, sprinter))
+                return false;
+        }
+    }
+
+    return !sprinter->hadOutOfMemory();
+}
+
+static bool
+DisassembleToString(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    Sprinter sprinter(cx);
+    if (!sprinter.init())
+        return false;
+    if (!DisassembleToSprinter(cx, args.length(), vp, &sprinter))
+        return false;
+
+    JSString* str = JS_NewStringCopyZ(cx, sprinter.string());
+    if (!str)
+        return false;
+    args.rval().setString(str);
+    return true;
+}
+
+static bool
+Disassemble(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (!gOutFile->isOpen()) {
+        JS_ReportErrorASCII(cx, "output file is closed");
+        return false;
+    }
+
+    Sprinter sprinter(cx);
+    if (!sprinter.init())
+        return false;
+    if (!DisassembleToSprinter(cx, args.length(), vp, &sprinter))
+        return false;
+
+    fprintf(gOutFile->fp, "%s\n", sprinter.string());
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+DisassFile(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (!gOutFile->isOpen()) {
+        JS_ReportErrorASCII(cx, "output file is closed");
+        return false;
+    }
+
+    /* Support extra options at the start, just like Disassemble. */
+    DisassembleOptionParser p(args.length(), args.array());
+    if (!p.parse(cx))
+        return false;
+
+    if (!p.argc) {
+        args.rval().setUndefined();
+        return true;
+    }
+
+    // We should change DisassembleOptionParser to store CallArgs.
+    JSString* str = JS::ToString(cx, HandleValue::fromMarkedLocation(&p.argv[0]));
+    if (!str)
+        return false;
+    JSAutoByteString filename(cx, str);
+    if (!filename)
+        return false;
+    RootedScript script(cx);
+
+    {
+        CompileOptions options(cx);
+        options.setIntroductionType("js shell disFile")
+               .setUTF8(true)
+               .setFileAndLine(filename.ptr(), 1)
+               .setIsRunOnce(true)
+               .setNoScriptRval(true);
+
+        if (!JS::Compile(cx, options, filename.ptr(), &script))
+            return false;
+    }
+
+    Sprinter sprinter(cx);
+    if (!sprinter.init())
+        return false;
+    bool ok = DisassembleScript(cx, script, nullptr, p.lines, p.recursive, p.sourceNotes, &sprinter);
+    if (ok)
+        fprintf(gOutFile->fp, "%s\n", sprinter.string());
+    if (!ok)
+        return false;
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+DisassWithSrc(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (!gOutFile->isOpen()) {
+        JS_ReportErrorASCII(cx, "output file is closed");
+        return false;
+    }
+
+    const size_t lineBufLen = 512;
+    unsigned len, line1, line2, bupline;
+    char linebuf[lineBufLen];
+    static const char sep[] = ";-------------------------";
+
+    RootedScript script(cx);
+    for (unsigned i = 0; i < args.length(); i++) {
+        script = ValueToScript(cx, args[i]);
+        if (!script)
+           return false;
+
+        if (!script->filename()) {
+            JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_FILE_SCRIPTS_ONLY);
+            return false;
+        }
+
+        FILE* file = fopen(script->filename(), "r");
+        if (!file) {
+            /* FIXME: script->filename() should become UTF-8 (bug 987069). */
+            ReportCantOpenErrorUnknownEncoding(cx, script->filename());
+            return false;
+        }
+        auto closeFile = MakeScopeExit([file]() { fclose(file); });
+
+        jsbytecode* pc = script->code();
+        jsbytecode* end = script->codeEnd();
+
+        Sprinter sprinter(cx);
+        if (!sprinter.init())
+            return false;
+
+        /* burn the leading lines */
+        line2 = PCToLineNumber(script, pc);
+        for (line1 = 0; line1 < line2 - 1; line1++) {
+            char* tmp = fgets(linebuf, lineBufLen, file);
+            if (!tmp) {
+                /* FIXME: This should use UTF-8 (bug 987069). */
+                JS_ReportErrorLatin1(cx, "failed to read %s fully", script->filename());
+                return false;
+            }
+        }
+
+        bupline = 0;
+        while (pc < end) {
+            line2 = PCToLineNumber(script, pc);
+
+            if (line2 < line1) {
+                if (bupline != line2) {
+                    bupline = line2;
+                    if (!sprinter.jsprintf("%s %3u: BACKUP\n", sep, line2))
+                        return false;
+                }
+            } else {
+                if (bupline && line1 == line2) {
+                    if (!sprinter.jsprintf("%s %3u: RESTORE\n", sep, line2))
+                        return false;
+                }
+                bupline = 0;
+                while (line1 < line2) {
+                    if (!fgets(linebuf, lineBufLen, file)) {
+                        /*
+                         * FIXME: script->filename() should become UTF-8
+                         *        (bug 987069).
+                         */
+                        JS_ReportErrorNumberLatin1(cx, my_GetErrorMessage, nullptr,
+                                                   JSSMSG_UNEXPECTED_EOF,
+                                                   script->filename());
+                        return false;
+                    }
+                    line1++;
+                    if (!sprinter.jsprintf("%s %3u: %s", sep, line1, linebuf))
+                        return false;
+                }
+            }
+
+            len = Disassemble1(cx, script, pc, script->pcToOffset(pc), true, &sprinter);
+            if (!len)
+                return false;
+
+            pc += len;
+        }
+
+        fprintf(gOutFile->fp, "%s\n", sprinter.string());
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+#endif /* DEBUG */
+
+/* Pretend we can always preserve wrappers for dummy DOM objects. */
+static bool
+DummyPreserveWrapperCallback(JSContext* cx, JSObject* obj)
+{
+    return true;
+}
+
+static bool
+Intern(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    JSString* str = JS::ToString(cx, args.get(0));
+    if (!str)
+        return false;
+
+    AutoStableStringChars strChars(cx);
+    if (!strChars.initTwoByte(cx, str))
+        return false;
+
+    mozilla::Range<const char16_t> chars = strChars.twoByteRange();
+
+    if (!JS_AtomizeAndPinUCStringN(cx, chars.begin().get(), chars.length()))
+        return false;
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+Clone(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedObject parent(cx);
+    RootedObject funobj(cx);
+
+    if (!args.length()) {
+        JS_ReportErrorASCII(cx, "Invalid arguments to clone");
+        return false;
+    }
+
+    {
+        Maybe<JSAutoCompartment> ac;
+        RootedObject obj(cx, args[0].isPrimitive() ? nullptr : &args[0].toObject());
+
+        if (obj && obj->is<CrossCompartmentWrapperObject>()) {
+            obj = UncheckedUnwrap(obj);
+            ac.emplace(cx, obj);
+            args[0].setObject(*obj);
+        }
+        if (obj && obj->is<JSFunction>()) {
+            funobj = obj;
+        } else {
+            JSFunction* fun = JS_ValueToFunction(cx, args[0]);
+            if (!fun)
+                return false;
+            funobj = JS_GetFunctionObject(fun);
+        }
+    }
+
+    if (args.length() > 1) {
+        if (!JS_ValueToObject(cx, args[1], &parent))
+            return false;
+    } else {
+        parent = js::GetGlobalForObjectCrossCompartment(&args.callee());
+    }
+
+    // Should it worry us that we might be getting with wrappers
+    // around with wrappers here?
+    JS::AutoObjectVector scopeChain(cx);
+    if (!parent->is<GlobalObject>() && !scopeChain.append(parent))
+        return false;
+    JSObject* clone = JS::CloneFunctionObject(cx, funobj, scopeChain);
+    if (!clone)
+        return false;
+    args.rval().setObject(*clone);
+    return true;
+}
+
+static bool
+Crash(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() == 0)
+        MOZ_CRASH("forced crash");
+    RootedString message(cx, JS::ToString(cx, args[0]));
+    if (!message)
+        return false;
+    char* utf8chars = JS_EncodeStringToUTF8(cx, message);
+    if (!utf8chars)
+        return false;
+#ifndef DEBUG
+    MOZ_ReportCrash(utf8chars, __FILE__, __LINE__);
+#endif
+    MOZ_CRASH_UNSAFE_OOL(utf8chars);
+}
+
+static bool
+GetSLX(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedScript script(cx);
+
+    script = ValueToScript(cx, args.get(0));
+    if (!script)
+        return false;
+    args.rval().setInt32(GetScriptLineExtent(script));
+    return true;
+}
+
+static bool
+ThrowError(JSContext* cx, unsigned argc, Value* vp)
+{
+    JS_ReportErrorASCII(cx, "This is an error");
+    return false;
+}
+
+#define LAZY_STANDARD_CLASSES
+
+/* A class for easily testing the inner/outer object callbacks. */
+typedef struct ComplexObject {
+    bool isInner;
+    bool frozen;
+    JSObject* inner;
+    JSObject* outer;
+} ComplexObject;
+
+static bool
+sandbox_enumerate(JSContext* cx, HandleObject obj)
+{
+    RootedValue v(cx);
+
+    if (!JS_GetProperty(cx, obj, "lazy", &v))
+        return false;
+
+    if (!ToBoolean(v))
+        return true;
+
+    return JS_EnumerateStandardClasses(cx, obj);
+}
+
+static bool
+sandbox_resolve(JSContext* cx, HandleObject obj, HandleId id, bool* resolvedp)
+{
+    RootedValue v(cx);
+    if (!JS_GetProperty(cx, obj, "lazy", &v))
+        return false;
+
+    if (ToBoolean(v))
+        return JS_ResolveStandardClass(cx, obj, id, resolvedp);
+    return true;
+}
+
+static const JSClassOps sandbox_classOps = {
+    nullptr, nullptr, nullptr, nullptr,
+    sandbox_enumerate, sandbox_resolve,
+    nullptr, nullptr,
+    nullptr, nullptr, nullptr,
+    JS_GlobalObjectTraceHook
+};
+
+static const JSClass sandbox_class = {
+    "sandbox",
+    JSCLASS_GLOBAL_FLAGS,
+    &sandbox_classOps
+};
+
+static void
+SetStandardCompartmentOptions(JS::CompartmentOptions& options)
+{
+    options.behaviors().setVersion(JSVERSION_DEFAULT);
+    options.creationOptions().setSharedMemoryAndAtomicsEnabled(enableSharedMemory);
+}
+
+static JSObject*
+NewSandbox(JSContext* cx, bool lazy)
+{
+    JS::CompartmentOptions options;
+    SetStandardCompartmentOptions(options);
+    RootedObject obj(cx, JS_NewGlobalObject(cx, &sandbox_class, nullptr,
+                                            JS::DontFireOnNewGlobalHook, options));
+    if (!obj)
+        return nullptr;
+
+    {
+        JSAutoCompartment ac(cx, obj);
+        if (!lazy && !JS_InitStandardClasses(cx, obj))
+            return nullptr;
+
+        RootedValue value(cx, BooleanValue(lazy));
+        if (!JS_SetProperty(cx, obj, "lazy", value))
+            return nullptr;
+    }
+
+    JS_FireOnNewGlobalObject(cx, obj);
+
+    if (!cx->compartment()->wrap(cx, &obj))
+        return nullptr;
+    return obj;
+}
+
+static bool
+EvalInContext(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!args.requireAtLeast(cx, "evalcx", 1))
+        return false;
+
+    RootedString str(cx, ToString(cx, args[0]));
+    if (!str)
+        return false;
+
+    RootedObject sobj(cx);
+    if (args.hasDefined(1)) {
+        sobj = ToObject(cx, args[1]);
+        if (!sobj)
+            return false;
+    }
+
+    AutoStableStringChars strChars(cx);
+    if (!strChars.initTwoByte(cx, str))
+        return false;
+
+    mozilla::Range<const char16_t> chars = strChars.twoByteRange();
+    size_t srclen = chars.length();
+    const char16_t* src = chars.begin().get();
+
+    bool lazy = false;
+    if (srclen == 4) {
+        if (src[0] == 'l' && src[1] == 'a' && src[2] == 'z' && src[3] == 'y') {
+            lazy = true;
+            srclen = 0;
+        }
+    }
+
+    if (!sobj) {
+        sobj = NewSandbox(cx, lazy);
+        if (!sobj)
+            return false;
+    }
+
+    if (srclen == 0) {
+        args.rval().setObject(*sobj);
+        return true;
+    }
+
+    JS::AutoFilename filename;
+    unsigned lineno;
+
+    DescribeScriptedCaller(cx, &filename, &lineno);
+    {
+        Maybe<JSAutoCompartment> ac;
+        unsigned flags;
+        JSObject* unwrapped = UncheckedUnwrap(sobj, true, &flags);
+        if (flags & Wrapper::CROSS_COMPARTMENT) {
+            sobj = unwrapped;
+            ac.emplace(cx, sobj);
+        }
+
+        sobj = ToWindowIfWindowProxy(sobj);
+
+        if (!(sobj->getClass()->flags & JSCLASS_IS_GLOBAL)) {
+            JS_ReportErrorASCII(cx, "Invalid scope argument to evalcx");
+            return false;
+        }
+        JS::CompileOptions opts(cx);
+        opts.setFileAndLine(filename.get(), lineno);
+        if (!JS::Evaluate(cx, opts, src, srclen, args.rval())) {
+            return false;
+        }
+    }
+
+    if (!cx->compartment()->wrap(cx, args.rval()))
+        return false;
+
+    return true;
+}
+
+struct WorkerInput
+{
+    JSContext* context;
+    char16_t* chars;
+    size_t length;
+
+    WorkerInput(JSContext* context, char16_t* chars, size_t length)
+      : context(context), chars(chars), length(length)
+    {}
+
+    ~WorkerInput() {
+        js_free(chars);
+    }
+};
+
+static void SetWorkerContextOptions(JSContext* cx);
+
+static void
+WorkerMain(void* arg)
+{
+    WorkerInput* input = (WorkerInput*) arg;
+
+    JSContext* cx = JS_NewContext(8L * 1024L * 1024L, 2L * 1024L * 1024L, input->context);
+    if (!cx) {
+        js_delete(input);
+        return;
+    }
+
+    UniquePtr<ShellContext> sc = MakeUnique<ShellContext>(cx);
+    if (!sc) {
+        JS_DestroyContext(cx);
+        js_delete(input);
+        return;
+    }
+
+    sc->isWorker = true;
+    JS_SetContextPrivate(cx, sc.get());
+    JS_SetFutexCanWait(cx);
+    JS::SetWarningReporter(cx, WarningReporter);
+    js::SetPreserveWrapperCallback(cx, DummyPreserveWrapperCallback);
+    JS_InitDestroyPrincipalsCallback(cx, ShellPrincipals::destroy);
+    SetWorkerContextOptions(cx);
+
+    if (!JS::InitSelfHostedCode(cx)) {
+        JS_DestroyContext(cx);
+        js_delete(input);
+        return;
+    }
+
+#ifdef SPIDERMONKEY_PROMISE
+    sc->jobQueue.init(cx, JobQueue(SystemAllocPolicy()));
+    JS::SetEnqueuePromiseJobCallback(cx, ShellEnqueuePromiseJobCallback);
+    JS::SetGetIncumbentGlobalCallback(cx, ShellGetIncumbentGlobalCallback);
+    JS::SetAsyncTaskCallbacks(cx, ShellStartAsyncTaskCallback, ShellFinishAsyncTaskCallback);
+#endif // SPIDERMONKEY_PROMISE
+
+    EnvironmentPreparer environmentPreparer(cx);
+
+    JS::SetLargeAllocationFailureCallback(cx, my_LargeAllocFailCallback, (void*)cx);
+
+    do {
+        JSAutoRequest ar(cx);
+
+        JS::CompartmentOptions compartmentOptions;
+        SetStandardCompartmentOptions(compartmentOptions);
+        RootedObject global(cx, NewGlobalObject(cx, compartmentOptions, nullptr));
+        if (!global)
+            break;
+
+        JSAutoCompartment ac(cx, global);
+
+        JS::CompileOptions options(cx);
+        options.setFileAndLine("<string>", 1)
+               .setIsRunOnce(true);
+
+        AutoReportException are(cx);
+        RootedScript script(cx);
+        if (!JS::Compile(cx, options, input->chars, input->length, &script))
+            break;
+        RootedValue result(cx);
+        JS_ExecuteScript(cx, script, &result);
+    } while (0);
+
+    JS::SetLargeAllocationFailureCallback(cx, nullptr, nullptr);
+
+#ifdef SPIDERMONKEY_PROMISE
+    JS::SetGetIncumbentGlobalCallback(cx, nullptr);
+    JS::SetEnqueuePromiseJobCallback(cx, nullptr);
+    sc->jobQueue.reset();
+#endif // SPIDERMONKEY_PROMISE
+
+    KillWatchdog(cx);
+
+    JS_DestroyContext(cx);
+
+    js_delete(input);
+}
+
+// Workers can spawn other workers, so we need a lock to access workerThreads.
+static Mutex* workerThreadsLock = nullptr;
+static Vector<js::Thread*, 0, SystemAllocPolicy> workerThreads;
+
+class MOZ_RAII AutoLockWorkerThreads : public LockGuard<Mutex>
+{
+    using Base = LockGuard<Mutex>;
+  public:
+    AutoLockWorkerThreads()
+      : Base(*workerThreadsLock)
+    {
+        MOZ_ASSERT(workerThreadsLock);
+    }
+};
+
+static bool
+EvalInWorker(JSContext* cx, unsigned argc, Value* vp)
+{
+    if (!CanUseExtraThreads()) {
+        JS_ReportErrorASCII(cx, "Can't create worker threads with --no-threads");
+        return false;
+    }
+
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!args.get(0).isString()) {
+        JS_ReportErrorASCII(cx, "Invalid arguments to evalInWorker");
+        return false;
+    }
+
+#if defined(DEBUG) || defined(JS_OOM_BREAKPOINT)
+    if (cx->runtime()->runningOOMTest) {
+        JS_ReportErrorASCII(cx, "Can't create workers while running simulated OOM test");
+        return false;
+    }
+#endif
+
+    if (!args[0].toString()->ensureLinear(cx))
+        return false;
+
+    if (!workerThreadsLock) {
+        workerThreadsLock = js_new<Mutex>(mutexid::ShellWorkerThreads);
+        if (!workerThreadsLock) {
+            ReportOutOfMemory(cx);
+            return false;
+        }
+    }
+
+    JSLinearString* str = &args[0].toString()->asLinear();
+
+    char16_t* chars = (char16_t*) js_malloc(str->length() * sizeof(char16_t));
+    if (!chars) {
+        ReportOutOfMemory(cx);
+        return false;
+    }
+
+    CopyChars(chars, *str);
+
+    WorkerInput* input = js_new<WorkerInput>(JS_GetParentContext(cx), chars, str->length());
+    if (!input) {
+        ReportOutOfMemory(cx);
+        return false;
+    }
+
+    auto thread = js_new<Thread>(Thread::Options().setStackSize(gMaxStackSize + 128 * 1024));
+    if (!thread || !thread->init(WorkerMain, input)) {
+        ReportOutOfMemory(cx);
+        return false;
+    }
+
+    AutoLockWorkerThreads alwt;
+    if (!workerThreads.append(thread)) {
+        ReportOutOfMemory(cx);
+        thread->join();
+        return false;
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+ShapeOf(JSContext* cx, unsigned argc, JS::Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!args.get(0).isObject()) {
+        JS_ReportErrorASCII(cx, "shapeOf: object expected");
+        return false;
+    }
+    JSObject* obj = &args[0].toObject();
+    args.rval().set(JS_NumberValue(double(uintptr_t(obj->maybeShape()) >> 3)));
+    return true;
+}
+
+static bool
+GroupOf(JSContext* cx, unsigned argc, JS::Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!args.get(0).isObject()) {
+        JS_ReportErrorASCII(cx, "groupOf: object expected");
+        return false;
+    }
+    JSObject* obj = &args[0].toObject();
+    ObjectGroup* group = obj->getGroup(cx);
+    if (!group)
+        return false;
+    args.rval().set(JS_NumberValue(double(uintptr_t(group) >> 3)));
+    return true;
+}
+
+static bool
+UnwrappedObjectsHaveSameShape(JSContext* cx, unsigned argc, JS::Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (!args.get(0).isObject() || !args.get(1).isObject()) {
+        JS_ReportErrorASCII(cx, "2 objects expected");
+        return false;
+    }
+
+    RootedObject obj1(cx, UncheckedUnwrap(&args[0].toObject()));
+    RootedObject obj2(cx, UncheckedUnwrap(&args[1].toObject()));
+
+    if (!obj1->is<ShapedObject>() || !obj2->is<ShapedObject>()) {
+        JS_ReportErrorASCII(cx, "object does not have a Shape");
+        return false;
+    }
+
+    args.rval().setBoolean(obj1->as<ShapedObject>().shape() == obj2->as<ShapedObject>().shape());
+    return true;
+}
+
+static bool
+Sleep_fn(JSContext* cx, unsigned argc, Value* vp)
+{
+    ShellContext* sc = GetShellContext(cx);
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    TimeDuration duration = TimeDuration::FromSeconds(0.0);
+    if (args.length() > 0) {
+        double t_secs;
+        if (!ToNumber(cx, args[0], &t_secs))
+            return false;
+        if (mozilla::IsNaN(t_secs)) {
+            JS_ReportErrorASCII(cx, "sleep interval is not a number");
+            return false;
+        }
+
+        duration = TimeDuration::FromSeconds(Max(0.0, t_secs));
+        const TimeDuration MAX_TIMEOUT_INTERVAL = TimeDuration::FromSeconds(MAX_TIMEOUT_SECONDS);
+        if (duration > MAX_TIMEOUT_INTERVAL) {
+            JS_ReportErrorASCII(cx, "Excessive sleep interval");
+            return false;
+        }
+    }
+    {
+        LockGuard<Mutex> guard(sc->watchdogLock);
+        TimeStamp toWakeup = TimeStamp::Now() + duration;
+        for (;;) {
+            sc->sleepWakeup.wait_for(guard, duration);
+            if (sc->serviceInterrupt)
+                break;
+            auto now = TimeStamp::Now();
+            if (now >= toWakeup)
+                break;
+            duration = toWakeup - now;
+        }
+    }
+    args.rval().setUndefined();
+    return !sc->serviceInterrupt;
+}
+
+static void
+KillWatchdog(JSContext* cx)
+{
+    ShellContext* sc = GetShellContext(cx);
+    Maybe<Thread> thread;
+
+    {
+        LockGuard<Mutex> guard(sc->watchdogLock);
+        Swap(sc->watchdogThread, thread);
+        if (thread) {
+            // The watchdog thread becoming Nothing is its signal to exit.
+            sc->watchdogWakeup.notify_one();
+        }
+    }
+    if (thread)
+        thread->join();
+
+    MOZ_ASSERT(!sc->watchdogThread);
+}
+
+static void
+WatchdogMain(JSContext* cx)
+{
+    ThisThread::SetName("JS Watchdog");
+
+    ShellContext* sc = GetShellContext(cx);
+
+    LockGuard<Mutex> guard(sc->watchdogLock);
+    while (sc->watchdogThread) {
+        auto now = TimeStamp::Now();
+        if (sc->watchdogTimeout && now >= sc->watchdogTimeout.value()) {
+            /*
+             * The timeout has just expired. Request an interrupt callback
+             * outside the lock.
+             */
+            sc->watchdogTimeout = Nothing();
+            {
+                UnlockGuard<Mutex> unlock(guard);
+                CancelExecution(cx);
+            }
+
+            /* Wake up any threads doing sleep. */
+            sc->sleepWakeup.notify_all();
+        } else {
+            if (sc->watchdogTimeout) {
+                /*
+                 * Time hasn't expired yet. Simulate an interrupt callback
+                 * which doesn't abort execution.
+                 */
+                JS_RequestInterruptCallback(cx);
+            }
+
+            TimeDuration sleepDuration = sc->watchdogTimeout
+                                         ? TimeDuration::FromSeconds(0.1)
+                                         : TimeDuration::Forever();
+            sc->watchdogWakeup.wait_for(guard, sleepDuration);
+        }
+    }
+}
+
+static bool
+ScheduleWatchdog(JSContext* cx, double t)
+{
+    ShellContext* sc = GetShellContext(cx);
+
+    if (t <= 0) {
+        LockGuard<Mutex> guard(sc->watchdogLock);
+        sc->watchdogTimeout = Nothing();
+        return true;
+    }
+
+    auto interval = TimeDuration::FromSeconds(t);
+    auto timeout = TimeStamp::Now() + interval;
+    LockGuard<Mutex> guard(sc->watchdogLock);
+    if (!sc->watchdogThread) {
+        MOZ_ASSERT(!sc->watchdogTimeout);
+        sc->watchdogThread.emplace();
+        AutoEnterOOMUnsafeRegion oomUnsafe;
+        if (!sc->watchdogThread->init(WatchdogMain, cx))
+            oomUnsafe.crash("watchdogThread.init");
+    } else if (!sc->watchdogTimeout || timeout < sc->watchdogTimeout.value()) {
+        sc->watchdogWakeup.notify_one();
+    }
+    sc->watchdogTimeout = Some(timeout);
+    return true;
+}
+
+static void
+KillWorkerThreads()
+{
+    MOZ_ASSERT_IF(!CanUseExtraThreads(), workerThreads.empty());
+
+    if (!workerThreadsLock) {
+        MOZ_ASSERT(workerThreads.empty());
+        return;
+    }
+
+    while (true) {
+        // We need to leave the AutoLockWorkerThreads scope before we call
+        // js::Thread::join, to avoid deadlocks when AutoLockWorkerThreads is
+        // used by the worker thread.
+        Thread* thread;
+        {
+            AutoLockWorkerThreads alwt;
+            if (workerThreads.empty())
+                break;
+            thread = workerThreads.popCopy();
+        }
+        thread->join();
+    }
+
+    js_delete(workerThreadsLock);
+    workerThreadsLock = nullptr;
+}
+
+static void
+CancelExecution(JSContext* cx)
+{
+    ShellContext* sc = GetShellContext(cx);
+    sc->serviceInterrupt = true;
+    JS_RequestInterruptCallback(cx);
+
+    if (sc->haveInterruptFunc) {
+        static const char msg[] = "Script runs for too long, terminating.\n";
+        fputs(msg, stderr);
+    }
+}
+
+static bool
+SetTimeoutValue(JSContext* cx, double t)
+{
+    if (mozilla::IsNaN(t)) {
+        JS_ReportErrorASCII(cx, "timeout is not a number");
+        return false;
+    }
+    const TimeDuration MAX_TIMEOUT_INTERVAL = TimeDuration::FromSeconds(MAX_TIMEOUT_SECONDS);
+    if (TimeDuration::FromSeconds(t) > MAX_TIMEOUT_INTERVAL) {
+        JS_ReportErrorASCII(cx, "Excessive timeout value");
+        return false;
+    }
+    GetShellContext(cx)->timeoutInterval = t;
+    if (!ScheduleWatchdog(cx, t)) {
+        JS_ReportErrorASCII(cx, "Failed to create the watchdog");
+        return false;
+    }
+    return true;
+}
+
+static bool
+Timeout(JSContext* cx, unsigned argc, Value* vp)
+{
+    ShellContext* sc = GetShellContext(cx);
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() == 0) {
+        args.rval().setNumber(sc->timeoutInterval);
+        return true;
+    }
+
+    if (args.length() > 2) {
+        JS_ReportErrorASCII(cx, "Wrong number of arguments");
+        return false;
+    }
+
+    double t;
+    if (!ToNumber(cx, args[0], &t))
+        return false;
+
+    if (args.length() > 1) {
+        RootedValue value(cx, args[1]);
+        if (!value.isObject() || !value.toObject().is<JSFunction>()) {
+            JS_ReportErrorASCII(cx, "Second argument must be a timeout function");
+            return false;
+        }
+        sc->interruptFunc = value;
+        sc->haveInterruptFunc = true;
+    }
+
+    args.rval().setUndefined();
+    return SetTimeoutValue(cx, t);
+}
+
+static bool
+InterruptIf(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 1) {
+        JS_ReportErrorASCII(cx, "Wrong number of arguments");
+        return false;
+    }
+
+    if (ToBoolean(args[0])) {
+        GetShellContext(cx)->serviceInterrupt = true;
+        JS_RequestInterruptCallback(cx);
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+InvokeInterruptCallbackWrapper(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() != 1) {
+        JS_ReportErrorASCII(cx, "Wrong number of arguments");
+        return false;
+    }
+
+    GetShellContext(cx)->serviceInterrupt = true;
+    JS_RequestInterruptCallback(cx);
+    bool interruptRv = CheckForInterrupt(cx);
+
+    // The interrupt handler could have set a pending exception. Since we call
+    // back into JS, don't have it see the pending exception. If we have an
+    // uncatchable exception that's not propagating a debug mode forced
+    // return, return.
+    if (!interruptRv && !cx->isExceptionPending() && !cx->isPropagatingForcedReturn())
+        return false;
+
+    JS::AutoSaveExceptionState savedExc(cx);
+
+    FixedInvokeArgs<1> iargs(cx);
+
+    iargs[0].setBoolean(interruptRv);
+
+    RootedValue rv(cx);
+    if (!js::Call(cx, args[0], UndefinedHandleValue, iargs, &rv))
+        return false;
+
+    args.rval().setUndefined();
+    return interruptRv;
+}
+
+static bool
+SetInterruptCallback(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 1) {
+        JS_ReportErrorASCII(cx, "Wrong number of arguments");
+        return false;
+    }
+
+    RootedValue value(cx, args[0]);
+    if (!value.isObject() || !value.toObject().is<JSFunction>()) {
+        JS_ReportErrorASCII(cx, "Argument must be a function");
+        return false;
+    }
+    GetShellContext(cx)->interruptFunc = value;
+    GetShellContext(cx)->haveInterruptFunc = true;
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+EnableLastWarning(JSContext* cx, unsigned argc, Value* vp)
+{
+    ShellContext* sc = GetShellContext(cx);
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    sc->lastWarningEnabled = true;
+    sc->lastWarning.setNull();
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+DisableLastWarning(JSContext* cx, unsigned argc, Value* vp)
+{
+    ShellContext* sc = GetShellContext(cx);
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    sc->lastWarningEnabled = false;
+    sc->lastWarning.setNull();
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+GetLastWarning(JSContext* cx, unsigned argc, Value* vp)
+{
+    ShellContext* sc = GetShellContext(cx);
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (!sc->lastWarningEnabled) {
+        JS_ReportErrorASCII(cx, "Call enableLastWarning first.");
+        return false;
+    }
+
+    if (!JS_WrapValue(cx, &sc->lastWarning))
+        return false;
+
+    args.rval().set(sc->lastWarning);
+    return true;
+}
+
+static bool
+ClearLastWarning(JSContext* cx, unsigned argc, Value* vp)
+{
+    ShellContext* sc = GetShellContext(cx);
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (!sc->lastWarningEnabled) {
+        JS_ReportErrorASCII(cx, "Call enableLastWarning first.");
+        return false;
+    }
+
+    sc->lastWarning.setNull();
+
+    args.rval().setUndefined();
+    return true;
+}
+
+#ifdef DEBUG
+static bool
+StackDump(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (!gOutFile->isOpen()) {
+        JS_ReportErrorASCII(cx, "output file is closed");
+        return false;
+    }
+
+    bool showArgs = ToBoolean(args.get(0));
+    bool showLocals = ToBoolean(args.get(1));
+    bool showThisProps = ToBoolean(args.get(2));
+
+    char* buf = JS::FormatStackDump(cx, nullptr, showArgs, showLocals, showThisProps);
+    if (!buf) {
+        fputs("Failed to format JavaScript stack for dump\n", gOutFile->fp);
+        JS_ClearPendingException(cx);
+    } else {
+        fputs(buf, gOutFile->fp);
+        JS_smprintf_free(buf);
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+#endif
+
+static bool
+StackPointerInfo(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    // Copy the truncated stack pointer to the result.  This value is not used
+    // as a pointer but as a way to measure frame-size from JS.
+    args.rval().setInt32(int32_t(reinterpret_cast<size_t>(&args) & 0xfffffff));
+    return true;
+}
+
+
+static bool
+Elapsed(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() == 0) {
+        double d = PRMJ_Now() - GetShellContext(cx)->startTime;
+        args.rval().setDouble(d);
+        return true;
+    }
+    JS_ReportErrorASCII(cx, "Wrong number of arguments");
+    return false;
+}
+
+static bool
+Compile(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() < 1) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_MORE_ARGS_NEEDED,
+                                  "compile", "0", "s");
+        return false;
+    }
+    if (!args[0].isString()) {
+        const char* typeName = InformalValueTypeName(args[0]);
+        JS_ReportErrorASCII(cx, "expected string to compile, got %s", typeName);
+        return false;
+    }
+
+    RootedObject global(cx, JS::CurrentGlobalOrNull(cx));
+    JSFlatString* scriptContents = args[0].toString()->ensureFlat(cx);
+    if (!scriptContents)
+        return false;
+
+    AutoStableStringChars stableChars(cx);
+    if (!stableChars.initTwoByte(cx, scriptContents))
+        return false;
+
+    JS::CompileOptions options(cx);
+    options.setIntroductionType("js shell compile")
+           .setFileAndLine("<string>", 1)
+           .setIsRunOnce(true)
+           .setNoScriptRval(true);
+    RootedScript script(cx);
+    const char16_t* chars = stableChars.twoByteRange().begin().get();
+    bool ok = JS_CompileUCScript(cx, chars, scriptContents->length(), options, &script);
+    args.rval().setUndefined();
+    return ok;
+}
+
+static bool
+ParseModule(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() == 0) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_MORE_ARGS_NEEDED,
+                                  "parseModule", "0", "s");
+        return false;
+    }
+
+    if (!args[0].isString()) {
+        const char* typeName = InformalValueTypeName(args[0]);
+        JS_ReportErrorASCII(cx, "expected string to compile, got %s", typeName);
+        return false;
+    }
+
+    JSFlatString* scriptContents = args[0].toString()->ensureFlat(cx);
+    if (!scriptContents)
+        return false;
+
+    UniqueChars filename;
+    CompileOptions options(cx);
+    if (args.length() > 1) {
+        if (!args[1].isString()) {
+            const char* typeName = InformalValueTypeName(args[1]);
+            JS_ReportErrorASCII(cx, "expected filename string, got %s", typeName);
+            return false;
+        }
+
+        RootedString str(cx, args[1].toString());
+        filename.reset(JS_EncodeString(cx, str));
+        if (!filename)
+            return false;
+
+        options.setFileAndLine(filename.get(), 1);
+    } else {
+        options.setFileAndLine("<string>", 1);
+    }
+
+    AutoStableStringChars stableChars(cx);
+    if (!stableChars.initTwoByte(cx, scriptContents))
+        return false;
+
+    const char16_t* chars = stableChars.twoByteRange().begin().get();
+    SourceBufferHolder srcBuf(chars, scriptContents->length(),
+                              SourceBufferHolder::NoOwnership);
+
+    RootedObject module(cx, frontend::CompileModule(cx, options, srcBuf));
+    if (!module)
+        return false;
+
+    args.rval().setObject(*module);
+    return true;
+}
+
+static bool
+SetModuleResolveHook(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() != 1) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_MORE_ARGS_NEEDED,
+                                  "setModuleResolveHook", "0", "s");
+        return false;
+    }
+
+    if (!args[0].isObject() || !args[0].toObject().is<JSFunction>()) {
+        const char* typeName = InformalValueTypeName(args[0]);
+        JS_ReportErrorASCII(cx, "expected hook function, got %s", typeName);
+        return false;
+    }
+
+    RootedFunction hook(cx, &args[0].toObject().as<JSFunction>());
+    Rooted<GlobalObject*> global(cx, cx->global());
+    global->setModuleResolveHook(hook);
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+GetModuleLoadPath(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    args.rval().setString(JS_NewStringCopyZ(cx, moduleLoadPath));
+    return true;
+}
+
+static bool
+Parse(JSContext* cx, unsigned argc, Value* vp)
+{
+    using namespace js::frontend;
+
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() < 1) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_MORE_ARGS_NEEDED,
+                                  "parse", "0", "s");
+        return false;
+    }
+    if (!args[0].isString()) {
+        const char* typeName = InformalValueTypeName(args[0]);
+        JS_ReportErrorASCII(cx, "expected string to parse, got %s", typeName);
+        return false;
+    }
+
+    JSFlatString* scriptContents = args[0].toString()->ensureFlat(cx);
+    if (!scriptContents)
+        return false;
+
+    AutoStableStringChars stableChars(cx);
+    if (!stableChars.initTwoByte(cx, scriptContents))
+        return false;
+
+    size_t length = scriptContents->length();
+    const char16_t* chars = stableChars.twoByteRange().begin().get();
+
+    CompileOptions options(cx);
+    options.setIntroductionType("js shell parse")
+           .setFileAndLine("<string>", 1);
+    UsedNameTracker usedNames(cx);
+    if (!usedNames.init())
+        return false;
+    Parser<FullParseHandler> parser(cx, cx->tempLifoAlloc(), options, chars, length,
+                                    /* foldConstants = */ true, usedNames, nullptr, nullptr);
+    if (!parser.checkOptions())
+        return false;
+
+    ParseNode* pn = parser.parse();
+    if (!pn)
+        return false;
+#ifdef DEBUG
+    DumpParseTree(pn);
+    fputc('\n', stderr);
+#endif
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+SyntaxParse(JSContext* cx, unsigned argc, Value* vp)
+{
+    using namespace js::frontend;
+
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() < 1) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_MORE_ARGS_NEEDED,
+                                  "parse", "0", "s");
+        return false;
+    }
+    if (!args[0].isString()) {
+        const char* typeName = InformalValueTypeName(args[0]);
+        JS_ReportErrorASCII(cx, "expected string to parse, got %s", typeName);
+        return false;
+    }
+
+    JSFlatString* scriptContents = args[0].toString()->ensureFlat(cx);
+    if (!scriptContents)
+        return false;
+    CompileOptions options(cx);
+    options.setIntroductionType("js shell syntaxParse")
+           .setFileAndLine("<string>", 1);
+
+    AutoStableStringChars stableChars(cx);
+    if (!stableChars.initTwoByte(cx, scriptContents))
+        return false;
+
+    const char16_t* chars = stableChars.twoByteRange().begin().get();
+    size_t length = scriptContents->length();
+    UsedNameTracker usedNames(cx);
+    if (!usedNames.init())
+        return false;
+    Parser<frontend::SyntaxParseHandler> parser(cx, cx->tempLifoAlloc(),
+                                                options, chars, length, false,
+                                                usedNames, nullptr, nullptr);
+    if (!parser.checkOptions())
+        return false;
+
+    bool succeeded = parser.parse();
+    if (cx->isExceptionPending())
+        return false;
+
+    if (!succeeded && !parser.hadAbortedSyntaxParse()) {
+        // If no exception is posted, either there was an OOM or a language
+        // feature unhandled by the syntax parser was encountered.
+        MOZ_ASSERT(cx->runtime()->hadOutOfMemory);
+        return false;
+    }
+
+    args.rval().setBoolean(succeeded);
+    return true;
+}
+
+static void
+OffThreadCompileScriptCallback(void* token, void* callbackData)
+{
+    ShellContext* sc = static_cast<ShellContext*>(callbackData);
+    sc->offThreadState.markDone(token);
+}
+
+static bool
+OffThreadCompileScript(JSContext* cx, unsigned argc, Value* vp)
+{
+    if (!CanUseExtraThreads()) {
+        JS_ReportErrorASCII(cx, "Can't use offThreadCompileScript with --no-threads");
+        return false;
+    }
+
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() < 1) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_MORE_ARGS_NEEDED,
+                                  "offThreadCompileScript", "0", "s");
+        return false;
+    }
+    if (!args[0].isString()) {
+        const char* typeName = InformalValueTypeName(args[0]);
+        JS_ReportErrorASCII(cx, "expected string to parse, got %s", typeName);
+        return false;
+    }
+
+    JSAutoByteString fileNameBytes;
+    CompileOptions options(cx);
+    options.setIntroductionType("js shell offThreadCompileScript")
+           .setFileAndLine("<string>", 1);
+
+    if (args.length() >= 2) {
+        if (args[1].isPrimitive()) {
+            JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                      "evaluate");
+            return false;
+        }
+
+        RootedObject opts(cx, &args[1].toObject());
+        if (!ParseCompileOptions(cx, options, opts, fileNameBytes))
+            return false;
+    }
+
+    // These option settings must override whatever the caller requested.
+    options.setIsRunOnce(true)
+           .setSourceIsLazy(false);
+
+    // We assume the caller wants caching if at all possible, ignoring
+    // heuristics that make sense for a real browser.
+    options.forceAsync = true;
+
+    JSString* scriptContents = args[0].toString();
+    AutoStableStringChars stableChars(cx);
+    if (!stableChars.initTwoByte(cx, scriptContents))
+        return false;
+
+    size_t length = scriptContents->length();
+    const char16_t* chars = stableChars.twoByteRange().begin().get();
+
+    // Make sure we own the string's chars, so that they are not freed before
+    // the compilation is finished.
+    ScopedJSFreePtr<char16_t> ownedChars;
+    if (stableChars.maybeGiveOwnershipToCaller()) {
+        ownedChars = const_cast<char16_t*>(chars);
+    } else {
+        char16_t* copy = cx->pod_malloc<char16_t>(length);
+        if (!copy)
+            return false;
+
+        mozilla::PodCopy(copy, chars, length);
+        ownedChars = copy;
+        chars = copy;
+    }
+
+    if (!JS::CanCompileOffThread(cx, options, length)) {
+        JS_ReportErrorASCII(cx, "cannot compile code on worker thread");
+        return false;
+    }
+
+    ShellContext* sc = GetShellContext(cx);
+    if (!sc->offThreadState.startIfIdle(cx, ScriptKind::Script, ownedChars)) {
+        JS_ReportErrorASCII(cx, "called offThreadCompileScript without calling runOffThreadScript"
+                            " to receive prior off-thread compilation");
+        return false;
+    }
+
+    if (!JS::CompileOffThread(cx, options, chars, length,
+                              OffThreadCompileScriptCallback, sc))
+    {
+        sc->offThreadState.abandon(cx);
+        return false;
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+runOffThreadScript(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (OffThreadParsingMustWaitForGC(cx))
+        gc::FinishGC(cx);
+
+    ShellContext* sc = GetShellContext(cx);
+    void* token = sc->offThreadState.waitUntilDone(cx, ScriptKind::Script);
+    if (!token) {
+        JS_ReportErrorASCII(cx, "called runOffThreadScript when no compilation is pending");
+        return false;
+    }
+
+    RootedScript script(cx, JS::FinishOffThreadScript(cx, token));
+    if (!script)
+        return false;
+
+    return JS_ExecuteScript(cx, script, args.rval());
+}
+
+static bool
+OffThreadCompileModule(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 1 || !args[0].isString()) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "offThreadCompileModule");
+        return false;
+    }
+
+    JSAutoByteString fileNameBytes;
+    CompileOptions options(cx);
+    options.setIntroductionType("js shell offThreadCompileModule")
+           .setFileAndLine("<string>", 1);
+    options.setIsRunOnce(true)
+           .setSourceIsLazy(false);
+    options.forceAsync = true;
+
+    JSString* scriptContents = args[0].toString();
+    AutoStableStringChars stableChars(cx);
+    if (!stableChars.initTwoByte(cx, scriptContents))
+        return false;
+
+    size_t length = scriptContents->length();
+    const char16_t* chars = stableChars.twoByteRange().begin().get();
+
+    // Make sure we own the string's chars, so that they are not freed before
+    // the compilation is finished.
+    ScopedJSFreePtr<char16_t> ownedChars;
+    if (stableChars.maybeGiveOwnershipToCaller()) {
+        ownedChars = const_cast<char16_t*>(chars);
+    } else {
+        char16_t* copy = cx->pod_malloc<char16_t>(length);
+        if (!copy)
+            return false;
+
+        mozilla::PodCopy(copy, chars, length);
+        ownedChars = copy;
+        chars = copy;
+    }
+
+    if (!JS::CanCompileOffThread(cx, options, length)) {
+        JS_ReportErrorASCII(cx, "cannot compile code on worker thread");
+        return false;
+    }
+
+    ShellContext* sc = GetShellContext(cx);
+    if (!sc->offThreadState.startIfIdle(cx, ScriptKind::Module, ownedChars)) {
+        JS_ReportErrorASCII(cx, "called offThreadCompileModule without receiving prior off-thread "
+                            "compilation");
+        return false;
+    }
+
+    if (!JS::CompileOffThreadModule(cx, options, chars, length,
+                                    OffThreadCompileScriptCallback, sc))
+    {
+        sc->offThreadState.abandon(cx);
+        return false;
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+FinishOffThreadModule(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (OffThreadParsingMustWaitForGC(cx))
+        gc::FinishGC(cx);
+
+    ShellContext* sc = GetShellContext(cx);
+    void* token = sc->offThreadState.waitUntilDone(cx, ScriptKind::Module);
+    if (!token) {
+        JS_ReportErrorASCII(cx, "called finishOffThreadModule when no compilation is pending");
+        return false;
+    }
+
+    RootedObject module(cx, JS::FinishOffThreadModule(cx, token));
+    if (!module)
+        return false;
+
+    args.rval().setObject(*module);
+    return true;
+}
+
+struct MOZ_RAII FreeOnReturn
+{
+    JSContext* cx;
+    const char* ptr;
+    MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
+
+    explicit FreeOnReturn(JSContext* cx, const char* ptr = nullptr
+                 MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+      : cx(cx), ptr(ptr)
+    {
+        MOZ_GUARD_OBJECT_NOTIFIER_INIT;
+    }
+
+    void init(const char* ptr) {
+        MOZ_ASSERT(!this->ptr);
+        this->ptr = ptr;
+    }
+
+    ~FreeOnReturn() {
+        JS_free(cx, (void*)ptr);
+    }
+};
+
+static int sArgc;
+static char** sArgv;
+
+class AutoCStringVector
+{
+    Vector<char*> argv_;
+  public:
+    explicit AutoCStringVector(JSContext* cx) : argv_(cx) {}
+    ~AutoCStringVector() {
+        for (size_t i = 0; i < argv_.length(); i++)
+            js_free(argv_[i]);
+    }
+    bool append(char* arg) {
+        if (!argv_.append(arg)) {
+            js_free(arg);
+            return false;
+        }
+        return true;
+    }
+    char* const* get() const {
+        return argv_.begin();
+    }
+    size_t length() const {
+        return argv_.length();
+    }
+    char* operator[](size_t i) const {
+        return argv_[i];
+    }
+    void replace(size_t i, char* arg) {
+        js_free(argv_[i]);
+        argv_[i] = arg;
+    }
+    char* back() const {
+        return argv_.back();
+    }
+    void replaceBack(char* arg) {
+        js_free(argv_.back());
+        argv_.back() = arg;
+    }
+};
+
+#if defined(XP_WIN)
+static bool
+EscapeForShell(AutoCStringVector& argv)
+{
+    // Windows will break arguments in argv by various spaces, so we wrap each
+    // argument in quotes and escape quotes within. Even with quotes, \ will be
+    // treated like an escape character, so inflate each \ to \\.
+
+    for (size_t i = 0; i < argv.length(); i++) {
+        if (!argv[i])
+            continue;
+
+        size_t newLen = 3;  // quotes before and after and null-terminator
+        for (char* p = argv[i]; *p; p++) {
+            newLen++;
+            if (*p == '\"' || *p == '\\')
+                newLen++;
+        }
+
+        char* escaped = (char*)js_malloc(newLen);
+        if (!escaped)
+            return false;
+
+        char* src = argv[i];
+        char* dst = escaped;
+        *dst++ = '\"';
+        while (*src) {
+            if (*src == '\"' || *src == '\\')
+                *dst++ = '\\';
+            *dst++ = *src++;
+        }
+        *dst++ = '\"';
+        *dst++ = '\0';
+        MOZ_ASSERT(escaped + newLen == dst);
+
+        argv.replace(i, escaped);
+    }
+    return true;
+}
+#endif
+
+static Vector<const char*, 4, js::SystemAllocPolicy> sPropagatedFlags;
+
+#if defined(JS_CODEGEN_X86) || defined(JS_CODEGEN_X64)
+static bool
+PropagateFlagToNestedShells(const char* flag)
+{
+    return sPropagatedFlags.append(flag);
+}
+#endif
+
+static bool
+NestedShell(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    AutoCStringVector argv(cx);
+
+    // The first argument to the shell is its path, which we assume is our own
+    // argv[0].
+    if (sArgc < 1) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_NESTED_FAIL);
+        return false;
+    }
+    if (!argv.append(strdup(sArgv[0])))
+        return false;
+
+    // Propagate selected flags from the current shell
+    for (unsigned i = 0; i < sPropagatedFlags.length(); i++) {
+        char* cstr = strdup(sPropagatedFlags[i]);
+        if (!cstr || !argv.append(cstr))
+            return false;
+    }
+
+    // The arguments to nestedShell are stringified and append to argv.
+    RootedString str(cx);
+    for (unsigned i = 0; i < args.length(); i++) {
+        str = ToString(cx, args[i]);
+        if (!str || !argv.append(JS_EncodeString(cx, str)))
+            return false;
+
+        // As a special case, if the caller passes "--js-cache", replace that
+        // with "--js-cache=$(jsCacheDir)"
+        if (!strcmp(argv.back(), "--js-cache") && jsCacheDir) {
+            char* newArg = JS_smprintf("--js-cache=%s", jsCacheDir);
+            if (!newArg)
+                return false;
+            argv.replaceBack(newArg);
+        }
+    }
+
+    // execv assumes argv is null-terminated
+    if (!argv.append(nullptr))
+        return false;
+
+    int status = 0;
+#if defined(XP_WIN)
+    if (!EscapeForShell(argv))
+        return false;
+    status = _spawnv(_P_WAIT, sArgv[0], argv.get());
+#else
+    pid_t pid = fork();
+    switch (pid) {
+      case -1:
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_NESTED_FAIL);
+        return false;
+      case 0:
+        (void)execv(sArgv[0], argv.get());
+        exit(-1);
+      default: {
+        while (waitpid(pid, &status, 0) < 0 && errno == EINTR)
+            continue;
+        break;
+      }
+    }
+#endif
+
+    if (status != 0) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_NESTED_FAIL);
+        return false;
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+DecompileFunction(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() < 1 || !args[0].isObject() || !args[0].toObject().is<JSFunction>()) {
+        args.rval().setUndefined();
+        return true;
+    }
+    RootedFunction fun(cx, &args[0].toObject().as<JSFunction>());
+    JSString* result = JS_DecompileFunction(cx, fun, 0);
+    if (!result)
+        return false;
+    args.rval().setString(result);
+    return true;
+}
+
+static bool
+DecompileThisScript(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    NonBuiltinScriptFrameIter iter(cx);
+    if (iter.done()) {
+        args.rval().setString(cx->runtime()->emptyString);
+        return true;
+    }
+
+    {
+        JSAutoCompartment ac(cx, iter.script());
+
+        RootedScript script(cx, iter.script());
+        JSString* result = JS_DecompileScript(cx, script, "test", 0);
+        if (!result)
+            return false;
+
+        args.rval().setString(result);
+    }
+
+    return JS_WrapValue(cx, args.rval());
+}
+
+static bool
+ThisFilename(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    JS::AutoFilename filename;
+    if (!DescribeScriptedCaller(cx, &filename) || !filename.get()) {
+        args.rval().setString(cx->runtime()->emptyString);
+        return true;
+    }
+
+    JSString* str = JS_NewStringCopyZ(cx, filename.get());
+    if (!str)
+        return false;
+
+    args.rval().setString(str);
+    return true;
+}
+
+static bool
+WrapWithProto(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    Value obj = UndefinedValue(), proto = UndefinedValue();
+    if (args.length() == 2) {
+        obj = args[0];
+        proto = args[1];
+    }
+    if (!obj.isObject() || !proto.isObjectOrNull()) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "wrapWithProto");
+        return false;
+    }
+
+    WrapperOptions options(cx);
+    options.setProto(proto.toObjectOrNull());
+    JSObject* wrapped = Wrapper::New(cx, &obj.toObject(),
+                                     &Wrapper::singletonWithPrototype, options);
+    if (!wrapped)
+        return false;
+
+    args.rval().setObject(*wrapped);
+    return true;
+}
+
+static bool
+NewGlobal(JSContext* cx, unsigned argc, Value* vp)
+{
+    JSPrincipals* principals = nullptr;
+
+    JS::CompartmentOptions options;
+    JS::CompartmentCreationOptions& creationOptions = options.creationOptions();
+    JS::CompartmentBehaviors& behaviors = options.behaviors();
+
+    SetStandardCompartmentOptions(options);
+
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (args.length() == 1 && args[0].isObject()) {
+        RootedObject opts(cx, &args[0].toObject());
+        RootedValue v(cx);
+
+        if (!JS_GetProperty(cx, opts, "invisibleToDebugger", &v))
+            return false;
+        if (v.isBoolean())
+            creationOptions.setInvisibleToDebugger(v.toBoolean());
+
+        if (!JS_GetProperty(cx, opts, "cloneSingletons", &v))
+            return false;
+        if (v.isBoolean())
+            creationOptions.setCloneSingletons(v.toBoolean());
+
+        if (!JS_GetProperty(cx, opts, "sameZoneAs", &v))
+            return false;
+        if (v.isObject())
+            creationOptions.setSameZoneAs(UncheckedUnwrap(&v.toObject()));
+
+        if (!JS_GetProperty(cx, opts, "disableLazyParsing", &v))
+            return false;
+        if (v.isBoolean())
+            behaviors.setDisableLazyParsing(v.toBoolean());
+
+        if (!JS_GetProperty(cx, opts, "principal", &v))
+            return false;
+        if (!v.isUndefined()) {
+            uint32_t bits;
+            if (!ToUint32(cx, v, &bits))
+                return false;
+            principals = cx->new_<ShellPrincipals>(bits);
+            if (!principals)
+                return false;
+            JS_HoldPrincipals(principals);
+        }
+    }
+
+    RootedObject global(cx, NewGlobalObject(cx, options, principals));
+    if (principals)
+        JS_DropPrincipals(cx, principals);
+    if (!global)
+        return false;
+
+    if (!JS_WrapObject(cx, &global))
+        return false;
+
+    args.rval().setObject(*global);
+    return true;
+}
+
+static bool
+NukeCCW(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 1 || !args[0].isObject() ||
+        !IsCrossCompartmentWrapper(&args[0].toObject()))
+    {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "nukeCCW");
+        return false;
+    }
+
+    NukeCrossCompartmentWrapper(cx, &args[0].toObject());
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+GetMaxArgs(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    args.rval().setInt32(ARGS_LENGTH_MAX);
+    return true;
+}
+
+static bool
+ObjectEmulatingUndefined(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    static const JSClass cls = {
+        "ObjectEmulatingUndefined",
+        JSCLASS_EMULATES_UNDEFINED
+    };
+
+    RootedObject obj(cx, JS_NewObject(cx, &cls));
+    if (!obj)
+        return false;
+    args.rval().setObject(*obj);
+    return true;
+}
+
+static bool
+GetSelfHostedValue(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 1 || !args[0].isString()) {
+        JS_ReportErrorNumberASCII(cx, my_GetErrorMessage, nullptr, JSSMSG_INVALID_ARGS,
+                                  "getSelfHostedValue");
+        return false;
+    }
+    RootedAtom srcAtom(cx, ToAtom<CanGC>(cx, args[0]));
+    if (!srcAtom)
+        return false;
+    RootedPropertyName srcName(cx, srcAtom->asPropertyName());
+    return cx->runtime()->cloneSelfHostedValue(cx, srcName, args.rval());
+}
+
+class ShellSourceHook: public SourceHook {
+    // The function we should call to lazily retrieve source code.
+    PersistentRootedFunction fun;
+
+  public:
+    ShellSourceHook(JSContext* cx, JSFunction& fun) : fun(cx, &fun) {}
+
+    bool load(JSContext* cx, const char* filename, char16_t** src, size_t* length) {
+        RootedString str(cx, JS_NewStringCopyZ(cx, filename));
+        if (!str)
+            return false;
+        RootedValue filenameValue(cx, StringValue(str));
+
+        RootedValue result(cx);
+        if (!Call(cx, UndefinedHandleValue, fun, HandleValueArray(filenameValue), &result))
+            return false;
+
+        str = JS::ToString(cx, result);
+        if (!str)
+            return false;
+
+        *length = JS_GetStringLength(str);
+        *src = cx->pod_malloc<char16_t>(*length);
+        if (!*src)
+            return false;
+
+        JSLinearString* linear = str->ensureLinear(cx);
+        if (!linear)
+            return false;
+
+        CopyChars(*src, *linear);
+        return true;
+    }
+};
+
+static bool
+WithSourceHook(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedObject callee(cx, &args.callee());
+
+    if (args.length() != 2) {
+        ReportUsageErrorASCII(cx, callee, "Wrong number of arguments.");
+        return false;
+    }
+
+    if (!args[0].isObject() || !args[0].toObject().is<JSFunction>()
+        || !args[1].isObject() || !args[1].toObject().is<JSFunction>()) {
+        ReportUsageErrorASCII(cx, callee, "First and second arguments must be functions.");
+        return false;
+    }
+
+    mozilla::UniquePtr<ShellSourceHook> hook =
+        mozilla::MakeUnique<ShellSourceHook>(cx, args[0].toObject().as<JSFunction>());
+    if (!hook)
+        return false;
+
+    mozilla::UniquePtr<SourceHook> savedHook = js::ForgetSourceHook(cx);
+    js::SetSourceHook(cx, Move(hook));
+
+    RootedObject fun(cx, &args[1].toObject());
+    bool result = Call(cx, UndefinedHandleValue, fun, JS::HandleValueArray::empty(), args.rval());
+    js::SetSourceHook(cx, Move(savedHook));
+    return result;
+}
+
+static bool
+IsCachingEnabled(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    args.rval().setBoolean(jsCachingEnabled && jsCacheAsmJSPath != nullptr);
+    return true;
+}
+
+static bool
+SetCachingEnabled(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (GetShellContext(cx)->isWorker) {
+        JS_ReportErrorASCII(cx, "Caching is not supported in workers");
+        return false;
+    }
+
+    jsCachingEnabled = ToBoolean(args.get(0));
+    args.rval().setUndefined();
+    return true;
+}
+
+static void
+PrintProfilerEvents_Callback(const char* msg)
+{
+    fprintf(stderr, "PROFILER EVENT: %s\n", msg);
+}
+
+static bool
+PrintProfilerEvents(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (cx->runtime()->spsProfiler.enabled())
+        js::RegisterContextProfilingEventMarker(cx, &PrintProfilerEvents_Callback);
+    args.rval().setUndefined();
+    return true;
+}
+
+#if defined(JS_SIMULATOR_ARM) || defined(JS_SIMULATOR_MIPS64)
+typedef Vector<char16_t, 0, SystemAllocPolicy> StackChars;
+Vector<StackChars, 0, SystemAllocPolicy> stacks;
+
+static void
+SingleStepCallback(void* arg, jit::Simulator* sim, void* pc)
+{
+    JSContext* cx = reinterpret_cast<JSContext*>(arg);
+
+    // If profiling is not enabled, don't do anything.
+    if (!cx->spsProfiler.enabled())
+        return;
+
+    JS::ProfilingFrameIterator::RegisterState state;
+    state.pc = pc;
+#if defined(JS_SIMULATOR_ARM)
+    state.sp = (void*)sim->get_register(jit::Simulator::sp);
+    state.lr = (void*)sim->get_register(jit::Simulator::lr);
+#elif defined(JS_SIMULATOR_MIPS64)
+    state.sp = (void*)sim->getRegister(jit::Simulator::sp);
+    state.lr = (void*)sim->getRegister(jit::Simulator::ra);
+#endif
+
+    mozilla::DebugOnly<void*> lastStackAddress = nullptr;
+    StackChars stack;
+    uint32_t frameNo = 0;
+    AutoEnterOOMUnsafeRegion oomUnsafe;
+    for (JS::ProfilingFrameIterator i(cx, state); !i.done(); ++i) {
+        MOZ_ASSERT(i.stackAddress() != nullptr);
+        MOZ_ASSERT(lastStackAddress <= i.stackAddress());
+        lastStackAddress = i.stackAddress();
+        JS::ProfilingFrameIterator::Frame frames[16];
+        uint32_t nframes = i.extractStack(frames, 0, 16);
+        for (uint32_t i = 0; i < nframes; i++) {
+            if (frameNo > 0) {
+                if (!stack.append(",", 1))
+                    oomUnsafe.crash("stack.append");
+            }
+            auto chars = frames[i].label.get();
+            if (!stack.append(chars, strlen(chars)))
+                oomUnsafe.crash("stack.append");
+            frameNo++;
+        }
+    }
+
+    // Only append the stack if it differs from the last stack.
+    if (stacks.empty() ||
+        stacks.back().length() != stack.length() ||
+        !PodEqual(stacks.back().begin(), stack.begin(), stack.length()))
+    {
+        if (!stacks.append(Move(stack)))
+            oomUnsafe.crash("stacks.append");
+    }
+}
+#endif
+
+static bool
+EnableSingleStepProfiling(JSContext* cx, unsigned argc, Value* vp)
+{
+#if defined(JS_SIMULATOR_ARM) || defined(JS_SIMULATOR_MIPS64)
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    jit::Simulator* sim = cx->runtime()->simulator();
+    sim->enable_single_stepping(SingleStepCallback, cx);
+
+    args.rval().setUndefined();
+    return true;
+#else
+    JS_ReportErrorASCII(cx, "single-step profiling not enabled on this platform");
+    return false;
+#endif
+}
+
+static bool
+DisableSingleStepProfiling(JSContext* cx, unsigned argc, Value* vp)
+{
+#if defined(JS_SIMULATOR_ARM) || defined(JS_SIMULATOR_MIPS64)
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    jit::Simulator* sim = cx->runtime()->simulator();
+    sim->disable_single_stepping();
+
+    AutoValueVector elems(cx);
+    for (size_t i = 0; i < stacks.length(); i++) {
+        JSString* stack = JS_NewUCStringCopyN(cx, stacks[i].begin(), stacks[i].length());
+        if (!stack)
+            return false;
+        if (!elems.append(StringValue(stack)))
+            return false;
+    }
+
+    JSObject* array = JS_NewArrayObject(cx, elems);
+    if (!array)
+        return false;
+
+    stacks.clear();
+    args.rval().setObject(*array);
+    return true;
+#else
+    JS_ReportErrorASCII(cx, "single-step profiling not enabled on this platform");
+    return false;
+#endif
+}
+
+static bool
+IsLatin1(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    bool isLatin1 = args.get(0).isString() && args[0].toString()->hasLatin1Chars();
+    args.rval().setBoolean(isLatin1);
+    return true;
+}
+
+static bool
+EnableSPSProfiling(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    ShellContext* sc = GetShellContext(cx);
+
+    // Disable before re-enabling; see the assertion in |SPSProfiler::setProfilingStack|.
+    if (cx->spsProfiler.installed())
+        cx->spsProfiler.enable(false);
+
+    SetContextProfilingStack(cx, sc->spsProfilingStack, &sc->spsProfilingStackSize,
+                             ShellContext::SpsProfilingMaxStackSize);
+    cx->spsProfiler.enableSlowAssertions(false);
+    cx->spsProfiler.enable(true);
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static bool
+EnableSPSProfilingWithSlowAssertions(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    args.rval().setUndefined();
+
+    ShellContext* sc = GetShellContext(cx);
+
+    if (cx->spsProfiler.enabled()) {
+        // If profiling already enabled with slow assertions disabled,
+        // this is a no-op.
+        if (cx->spsProfiler.slowAssertionsEnabled())
+            return true;
+
+        // Slow assertions are off.  Disable profiling before re-enabling
+        // with slow assertions on.
+        cx->spsProfiler.enable(false);
+    }
+
+    // Disable before re-enabling; see the assertion in |SPSProfiler::setProfilingStack|.
+    if (cx->spsProfiler.installed())
+        cx->spsProfiler.enable(false);
+
+    SetContextProfilingStack(cx, sc->spsProfilingStack, &sc->spsProfilingStackSize,
+                             ShellContext::SpsProfilingMaxStackSize);
+    cx->spsProfiler.enableSlowAssertions(true);
+    cx->spsProfiler.enable(true);
+
+    return true;
+}
+
+static bool
+DisableSPSProfiling(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    if (cx->runtime()->spsProfiler.installed())
+        cx->runtime()->spsProfiler.enable(false);
+    args.rval().setUndefined();
+    return true;
+}
+
+// Global mailbox that is used to communicate a SharedArrayBuffer
+// value from one worker to another.
+//
+// For simplicity we store only the SharedArrayRawBuffer; retaining
+// the SAB object would require per-runtime storage, and would have no
+// real benefits.
+//
+// Invariant: when a SARB is in the mailbox its reference count is at
+// least 1, accounting for the reference from the mailbox.
+//
+// The lock guards the mailbox variable and prevents a race where two
+// workers try to set the mailbox at the same time to replace a SARB
+// that is only referenced from the mailbox: the workers will both
+// decrement the reference count on the old SARB, and one of those
+// decrements will be on a garbage object.  We could implement this
+// with atomics and a CAS loop but it's not worth the bother.
+
+static Mutex* sharedArrayBufferMailboxLock;
+static SharedArrayRawBuffer* sharedArrayBufferMailbox;
+
+static bool
+InitSharedArrayBufferMailbox()
+{
+    sharedArrayBufferMailboxLock = js_new<Mutex>(mutexid::ShellArrayBufferMailbox);
+    return sharedArrayBufferMailboxLock != nullptr;
+}
+
+static void
+DestructSharedArrayBufferMailbox()
+{
+    // All workers need to have terminated at this point.
+    if (sharedArrayBufferMailbox)
+        sharedArrayBufferMailbox->dropReference();
+    js_delete(sharedArrayBufferMailboxLock);
+}
+
+static bool
+GetSharedArrayBuffer(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    JSObject* newObj = nullptr;
+    bool rval = true;
+
+    sharedArrayBufferMailboxLock->lock();
+    SharedArrayRawBuffer* buf = sharedArrayBufferMailbox;
+    if (buf) {
+        buf->addReference();
+        // Shared memory is enabled globally in the shell: there can't be a worker
+        // that does not enable it if the main thread has it.
+        MOZ_ASSERT(cx->compartment()->creationOptions().getSharedMemoryAndAtomicsEnabled());
+        newObj = SharedArrayBufferObject::New(cx, buf);
+        if (!newObj) {
+            buf->dropReference();
+            rval = false;
+        }
+    }
+    sharedArrayBufferMailboxLock->unlock();
+
+    args.rval().setObjectOrNull(newObj);
+    return rval;
+}
+
+static bool
+SetSharedArrayBuffer(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    SharedArrayRawBuffer* newBuffer = nullptr;
+
+    if (argc == 0 || args.get(0).isNullOrUndefined()) {
+        // Clear out the mailbox
+    }
+    else if (args.get(0).isObject() && args[0].toObject().is<SharedArrayBufferObject>()) {
+        newBuffer = args[0].toObject().as<SharedArrayBufferObject>().rawBufferObject();
+        newBuffer->addReference();
+    } else {
+        JS_ReportErrorASCII(cx, "Only a SharedArrayBuffer can be installed in the global mailbox");
+        return false;
+    }
+
+    sharedArrayBufferMailboxLock->lock();
+    SharedArrayRawBuffer* oldBuffer = sharedArrayBufferMailbox;
+    if (oldBuffer)
+        oldBuffer->dropReference();
+    sharedArrayBufferMailbox = newBuffer;
+    sharedArrayBufferMailboxLock->unlock();
+
+    args.rval().setUndefined();
+    return true;
+}
+
+class SprintOptimizationTypeInfoOp : public JS::ForEachTrackedOptimizationTypeInfoOp
+{
+    Sprinter* sp;
+    bool startedTypes_;
+    bool hadError_;
+
+  public:
+    explicit SprintOptimizationTypeInfoOp(Sprinter* sp)
+      : sp(sp),
+        startedTypes_(false),
+        hadError_(false)
+    { }
+
+    void readType(const char* keyedBy, const char* name,
+                  const char* location, Maybe<unsigned> lineno) override
+    {
+        if (hadError_)
+            return;
+
+        do {
+            if (!startedTypes_) {
+                startedTypes_ = true;
+                if (sp->put("{\"typeset\": [") < 0)
+                    break;
+            }
+
+            if (!sp->jsprintf("{\"keyedBy\":\"%s\"", keyedBy))
+                break;
+
+            if (name) {
+                if (!sp->jsprintf(",\"name\":\"%s\"", name))
+                    break;
+            }
+
+            if (location) {
+                char buf[512];
+                PutEscapedString(buf, mozilla::ArrayLength(buf), location, strlen(location), '"');
+                if (!sp->jsprintf(",\"location\":%s", buf))
+                    break;
+            }
+            if (lineno.isSome()) {
+                if (!sp->jsprintf(",\"line\":%u", *lineno))
+                    break;
+            }
+            if (sp->put("},") < 0)
+                break;
+
+            return;
+        } while (false);
+
+        hadError_ = true;
+    }
+
+    void operator()(JS::TrackedTypeSite site, const char* mirType) override {
+        if (hadError_)
+            return;
+
+        do {
+            if (startedTypes_) {
+                // Clear trailing ,
+                if ((*sp)[sp->getOffset() - 1] == ',')
+                    (*sp)[sp->getOffset() - 1] = ' ';
+                if (sp->put("],") < 0)
+                    break;
+
+                startedTypes_ = false;
+            } else {
+                if (sp->put("{") < 0)
+                    break;
+            }
+
+            if (!sp->jsprintf("\"site\":\"%s\",\"mirType\":\"%s\"},",
+                              TrackedTypeSiteString(site), mirType))
+            {
+                break;
+            }
+
+            return;
+        } while (false);
+
+        hadError_ = true;
+    }
+
+    bool hadError() const {
+        return hadError_;
+    }
+};
+
+class SprintOptimizationAttemptsOp : public JS::ForEachTrackedOptimizationAttemptOp
+{
+    Sprinter* sp;
+    bool hadError_;
+
+  public:
+    explicit SprintOptimizationAttemptsOp(Sprinter* sp)
+      : sp(sp), hadError_(false)
+    { }
+
+    void operator()(JS::TrackedStrategy strategy, JS::TrackedOutcome outcome) override {
+        if (hadError_)
+            return;
+
+        hadError_ = !sp->jsprintf("{\"strategy\":\"%s\",\"outcome\":\"%s\"},",
+                                  TrackedStrategyString(strategy), TrackedOutcomeString(outcome));
+    }
+
+    bool hadError() const {
+        return hadError_;
+    }
+};
+
+static bool
+ReflectTrackedOptimizations(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedObject callee(cx, &args.callee());
+    JSRuntime* rt = cx->runtime();
+
+    if (!rt->hasJitRuntime() || !rt->jitRuntime()->isOptimizationTrackingEnabled(rt)) {
+        JS_ReportErrorASCII(cx, "Optimization tracking is off.");
+        return false;
+    }
+
+    if (args.length() != 1) {
+        ReportUsageErrorASCII(cx, callee, "Wrong number of arguments");
+        return false;
+    }
+
+    if (!args[0].isObject() || !args[0].toObject().is<JSFunction>()) {
+        ReportUsageErrorASCII(cx, callee, "Argument must be a function");
+        return false;
+    }
+
+    RootedFunction fun(cx, &args[0].toObject().as<JSFunction>());
+    if (!fun->hasScript() || !fun->nonLazyScript()->hasIonScript()) {
+        args.rval().setNull();
+        return true;
+    }
+
+    // Suppress GC for the unrooted JitcodeGlobalEntry below.
+    gc::AutoSuppressGC suppress(cx);
+
+    jit::JitcodeGlobalTable* table = rt->jitRuntime()->getJitcodeGlobalTable();
+    jit::IonScript* ion = fun->nonLazyScript()->ionScript();
+    jit::JitcodeGlobalEntry& entry = table->lookupInfallible(ion->method()->raw());
+
+    if (!entry.hasTrackedOptimizations()) {
+        JSObject* obj = JS_NewPlainObject(cx);
+        if (!obj)
+            return false;
+        args.rval().setObject(*obj);
+        return true;
+    }
+
+    Sprinter sp(cx);
+    if (!sp.init())
+        return false;
+
+    const jit::IonTrackedOptimizationsRegionTable* regions =
+        entry.ionEntry().trackedOptimizationsRegionTable();
+
+    if (sp.put("{\"regions\": [") < 0)
+        return false;
+
+    for (uint32_t i = 0; i < regions->numEntries(); i++) {
+        jit::IonTrackedOptimizationsRegion region = regions->entry(i);
+        jit::IonTrackedOptimizationsRegion::RangeIterator iter = region.ranges();
+        while (iter.more()) {
+            uint32_t startOffset, endOffset;
+            uint8_t index;
+            iter.readNext(&startOffset, &endOffset, &index);
+
+            JSScript* script;
+            jsbytecode* pc;
+            // Use endOffset, as startOffset may be associated with a
+            // previous, adjacent region ending exactly at startOffset. That
+            // is, suppose we have two regions [0, startOffset], [startOffset,
+            // endOffset]. Since we are not querying a return address, we want
+            // the second region and not the first.
+            uint8_t* addr = ion->method()->raw() + endOffset;
+            entry.youngestFrameLocationAtAddr(rt, addr, &script, &pc);
+
+            if (!sp.jsprintf("{\"location\":\"%s:%" PRIuSIZE "\",\"offset\":%" PRIuSIZE ",\"index\":%u}%s",
+                             script->filename(), script->lineno(), script->pcToOffset(pc), index,
+                             iter.more() ? "," : ""))
+            {
+                return false;
+            }
+        }
+    }
+
+    if (sp.put("],") < 0)
+        return false;
+
+    if (sp.put("\"opts\": [") < 0)
+        return false;
+
+    for (uint8_t i = 0; i < entry.ionEntry().numOptimizationAttempts(); i++) {
+        if (!sp.jsprintf("%s{\"typeinfo\":[", i == 0 ? "" : ","))
+            return false;
+
+        SprintOptimizationTypeInfoOp top(&sp);
+        jit::IonTrackedOptimizationsTypeInfo::ForEachOpAdapter adapter(top);
+        entry.trackedOptimizationTypeInfo(i).forEach(adapter, entry.allTrackedTypes());
+        if (top.hadError())
+            return false;
+
+        // Clear the trailing ,
+        if (sp[sp.getOffset() - 1] == ',')
+            sp[sp.getOffset() - 1] = ' ';
+
+        if (sp.put("],\"attempts\":[") < 0)
+            return false;
+
+        SprintOptimizationAttemptsOp aop(&sp);
+        entry.trackedOptimizationAttempts(i).forEach(aop);
+        if (aop.hadError())
+            return false;
+
+        // Clear the trailing ,
+        if (sp[sp.getOffset() - 1] == ',')
+            sp[sp.getOffset() - 1] = ' ';
+
+        if (sp.put("]}") < 0)
+            return false;
+    }
+
+    if (sp.put("]}") < 0)
+        return false;
+
+    if (sp.hadOutOfMemory())
+        return false;
+
+    RootedString str(cx, JS_NewStringCopyZ(cx, sp.string()));
+    if (!str)
+        return false;
+    RootedValue jsonVal(cx);
+    if (!JS_ParseJSON(cx, str, &jsonVal))
+        return false;
+
+    args.rval().set(jsonVal);
+    return true;
+}
+
+static bool
+DumpScopeChain(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedObject callee(cx, &args.callee());
+
+    if (args.length() != 1) {
+        ReportUsageErrorASCII(cx, callee, "Wrong number of arguments");
+        return false;
+    }
+
+    if (!args[0].isObject() ||
+        !(args[0].toObject().is<JSFunction>() || args[0].toObject().is<ModuleObject>()))
+    {
+        ReportUsageErrorASCII(cx, callee, "Argument must be an interpreted function or a module");
+        return false;
+    }
+
+    RootedObject obj(cx, &args[0].toObject());
+    RootedScript script(cx);
+
+    if (obj->is<JSFunction>()) {
+        RootedFunction fun(cx, &obj->as<JSFunction>());
+        if (!fun->isInterpreted()) {
+            ReportUsageErrorASCII(cx, callee, "Argument must be an interpreted function");
+            return false;
+        }
+        script = fun->getOrCreateScript(cx);
+    } else {
+        script = obj->as<ModuleObject>().script();
+    }
+
+    script->bodyScope()->dump();
+
+    args.rval().setUndefined();
+    return true;
+}
+
+namespace js {
+namespace shell {
+
+class ShellAutoEntryMonitor : JS::dbg::AutoEntryMonitor {
+    Vector<UniqueChars, 1, js::SystemAllocPolicy> log;
+    bool oom;
+    bool enteredWithoutExit;
+
+  public:
+    explicit ShellAutoEntryMonitor(JSContext *cx)
+      : AutoEntryMonitor(cx),
+        oom(false),
+        enteredWithoutExit(false)
+    { }
+
+    ~ShellAutoEntryMonitor() {
+        MOZ_ASSERT(!enteredWithoutExit);
+    }
+
+    void Entry(JSContext* cx, JSFunction* function, JS::HandleValue asyncStack,
+               const char* asyncCause) override {
+        MOZ_ASSERT(!enteredWithoutExit);
+        enteredWithoutExit = true;
+
+        RootedString displayId(cx, JS_GetFunctionDisplayId(function));
+        if (displayId) {
+            UniqueChars displayIdStr(JS_EncodeStringToUTF8(cx, displayId));
+            if (!displayIdStr) {
+                // We report OOM in buildResult.
+                cx->recoverFromOutOfMemory();
+                oom = true;
+                return;
+            }
+            oom = !log.append(mozilla::Move(displayIdStr));
+            return;
+        }
+
+        oom = !log.append(DuplicateString("anonymous"));
+    }
+
+    void Entry(JSContext* cx, JSScript* script, JS::HandleValue asyncStack,
+               const char* asyncCause) override {
+        MOZ_ASSERT(!enteredWithoutExit);
+        enteredWithoutExit = true;
+
+        UniqueChars label(JS_smprintf("eval:%s", JS_GetScriptFilename(script)));
+        oom = !label || !log.append(mozilla::Move(label));
+    }
+
+    void Exit(JSContext* cx) override {
+        MOZ_ASSERT(enteredWithoutExit);
+        enteredWithoutExit = false;
+    }
+
+    bool buildResult(JSContext *cx, MutableHandleValue resultValue) {
+        if (oom) {
+            JS_ReportOutOfMemory(cx);
+            return false;
+        }
+
+        RootedObject result(cx, JS_NewArrayObject(cx, log.length()));
+        if (!result)
+            return false;
+
+        for (size_t i = 0; i < log.length(); i++) {
+            char *name = log[i].get();
+            RootedString string(cx, Atomize(cx, name, strlen(name)));
+            if (!string)
+                return false;
+            RootedValue value(cx, StringValue(string));
+            if (!JS_SetElement(cx, result, i, value))
+                return false;
+        }
+
+        resultValue.setObject(*result.get());
+        return true;
+    }
+};
+
+} // namespace shell
+} // namespace js
+
+static bool
+EntryPoints(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 1) {
+        JS_ReportErrorASCII(cx, "Wrong number of arguments");
+        return false;
+    }
+
+    RootedObject opts(cx, ToObject(cx, args[0]));
+    if (!opts)
+        return false;
+
+    // { function: f } --- Call f.
+    {
+        RootedValue fun(cx), dummy(cx);
+
+        if (!JS_GetProperty(cx, opts, "function", &fun))
+            return false;
+        if (!fun.isUndefined()) {
+            js::shell::ShellAutoEntryMonitor sarep(cx);
+            if (!Call(cx, UndefinedHandleValue, fun, JS::HandleValueArray::empty(), &dummy))
+                return false;
+            return sarep.buildResult(cx, args.rval());
+        }
+    }
+
+    // { object: o, property: p, value: v } --- Fetch o[p], or if
+    // v is present, assign o[p] = v.
+    {
+        RootedValue objectv(cx), propv(cx), valuev(cx);
+
+        if (!JS_GetProperty(cx, opts, "object", &objectv) ||
+            !JS_GetProperty(cx, opts, "property", &propv))
+            return false;
+        if (!objectv.isUndefined() && !propv.isUndefined()) {
+            RootedObject object(cx, ToObject(cx, objectv));
+            if (!object)
+                return false;
+
+            RootedString string(cx, ToString(cx, propv));
+            if (!string)
+                return false;
+            RootedId id(cx);
+            if (!JS_StringToId(cx, string, &id))
+                return false;
+
+            if (!JS_GetProperty(cx, opts, "value", &valuev))
+                return false;
+
+            js::shell::ShellAutoEntryMonitor sarep(cx);
+
+            if (!valuev.isUndefined()) {
+                if (!JS_SetPropertyById(cx, object, id, valuev))
+                    return false;
+            } else {
+                if (!JS_GetPropertyById(cx, object, id, &valuev))
+                    return false;
+            }
+
+            return sarep.buildResult(cx, args.rval());
+        }
+    }
+
+    // { ToString: v } --- Apply JS::ToString to v.
+    {
+        RootedValue v(cx);
+
+        if (!JS_GetProperty(cx, opts, "ToString", &v))
+            return false;
+        if (!v.isUndefined()) {
+            js::shell::ShellAutoEntryMonitor sarep(cx);
+            if (!JS::ToString(cx, v))
+                return false;
+            return sarep.buildResult(cx, args.rval());
+        }
+    }
+
+    // { ToNumber: v } --- Apply JS::ToNumber to v.
+    {
+        RootedValue v(cx);
+        double dummy;
+
+        if (!JS_GetProperty(cx, opts, "ToNumber", &v))
+            return false;
+        if (!v.isUndefined()) {
+            js::shell::ShellAutoEntryMonitor sarep(cx);
+            if (!JS::ToNumber(cx, v, &dummy))
+                return false;
+            return sarep.buildResult(cx, args.rval());
+        }
+    }
+
+    // { eval: code } --- Apply ToString and then Evaluate to code.
+    {
+        RootedValue code(cx), dummy(cx);
+
+        if (!JS_GetProperty(cx, opts, "eval", &code))
+            return false;
+        if (!code.isUndefined()) {
+            RootedString codeString(cx, ToString(cx, code));
+            if (!codeString || !codeString->ensureFlat(cx))
+                return false;
+
+            AutoStableStringChars stableChars(cx);
+            if (!stableChars.initTwoByte(cx, codeString))
+                return false;
+            const char16_t* chars = stableChars.twoByteRange().begin().get();
+            size_t length = codeString->length();
+
+            CompileOptions options(cx);
+            options.setIntroductionType("entryPoint eval")
+                   .setFileAndLine("entryPoint eval", 1);
+
+            js::shell::ShellAutoEntryMonitor sarep(cx);
+            if (!JS::Evaluate(cx, options, chars, length, &dummy))
+                return false;
+            return sarep.buildResult(cx, args.rval());
+        }
+    }
+
+    JS_ReportErrorASCII(cx, "bad 'params' object");
+    return false;
+}
+
+static bool
+SetARMHwCapFlags(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    if (args.length() != 1) {
+        JS_ReportErrorASCII(cx, "Wrong number of arguments");
+        return false;
+    }
+
+    RootedString flagsListString(cx, JS::ToString(cx, args.get(0)));
+    if (!flagsListString)
+        return false;
+
+#if defined(JS_CODEGEN_ARM)
+    JSAutoByteString flagsList(cx, flagsListString);
+    if (!flagsList)
+        return false;
+
+    jit::ParseARMHwCapFlags(flagsList.ptr());
+#endif
+
+    args.rval().setUndefined();
+    return true;
+}
+
+#ifndef __AFL_HAVE_MANUAL_CONTROL
+# define __AFL_LOOP(x) true
+#endif
+
+static bool
+WasmLoop(JSContext* cx, unsigned argc, Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedObject callee(cx, &args.callee());
+
+    if (args.length() < 1 || args.length() > 2) {
+        ReportUsageErrorASCII(cx, callee, "Wrong number of arguments");
+        return false;
+    }
+
+    if (!args[0].isString()) {
+        ReportUsageErrorASCII(cx, callee, "First argument must be a String");
+        return false;
+    }
+
+    RootedObject importObj(cx);
+    if (!args.get(1).isUndefined()) {
+        if (!args.get(1).isObject()) {
+            ReportUsageErrorASCII(cx, callee, "Second argument, if present, must be an Object");
+            return false;
+        }
+        importObj = &args[1].toObject();
+    }
+
+    RootedString givenPath(cx, args[0].toString());
+    RootedString filename(cx, ResolvePath(cx, givenPath, RootRelative));
+    if (!filename)
+        return false;
+
+    while (__AFL_LOOP(1000)) {
+        Rooted<JSObject*> ret(cx, FileAsTypedArray(cx, filename));
+        if (!ret)
+            return false;
+
+        Rooted<TypedArrayObject*> typedArray(cx, &ret->as<TypedArrayObject>());
+        RootedWasmInstanceObject instanceObj(cx);
+        if (!wasm::Eval(cx, typedArray, importObj, &instanceObj)) {
+            // Clear any pending exceptions, we don't care about them
+            cx->clearPendingException();
+        }
+    }
+
+    return true;
+}
+
+static const JSFunctionSpecWithHelp shell_functions[] = {
+    JS_FN_HELP("version", Version, 0, 0,
+"version([number])",
+"  Get or force a script compilation version number."),
+
+    JS_FN_HELP("options", Options, 0, 0,
+"options([option ...])",
+"  Get or toggle JavaScript options."),
+
+    JS_FN_HELP("load", Load, 1, 0,
+"load(['foo.js' ...])",
+"  Load files named by string arguments. Filename is relative to the\n"
+"      current working directory."),
+
+    JS_FN_HELP("loadRelativeToScript", LoadScriptRelativeToScript, 1, 0,
+"loadRelativeToScript(['foo.js' ...])",
+"  Load files named by string arguments. Filename is relative to the\n"
+"      calling script."),
+
+    JS_FN_HELP("evaluate", Evaluate, 2, 0,
+"evaluate(code[, options])",
+"  Evaluate code as though it were the contents of a file.\n"
+"  options is an optional object that may have these properties:\n"
+"      isRunOnce: use the isRunOnce compiler option (default: false)\n"
+"      noScriptRval: use the no-script-rval compiler option (default: false)\n"
+"      fileName: filename for error messages and debug info\n"
+"      lineNumber: starting line number for error messages and debug info\n"
+"      columnNumber: starting column number for error messages and debug info\n"
+"      global: global in which to execute the code\n"
+"      newContext: if true, create and use a new cx (default: false)\n"
+"      catchTermination: if true, catch termination (failure without\n"
+"         an exception value, as for slow scripts or out-of-memory)\n"
+"         and return 'terminated'\n"
+"      element: if present with value |v|, convert |v| to an object |o| and\n"
+"         mark the source as being attached to the DOM element |o|. If the\n"
+"         property is omitted or |v| is null, don't attribute the source to\n"
+"         any DOM element.\n"
+"      elementAttributeName: if present and not undefined, the name of\n"
+"         property of 'element' that holds this code. This is what\n"
+"         Debugger.Source.prototype.elementAttributeName returns.\n"
+"      sourceMapURL: if present with value |v|, convert |v| to a string, and\n"
+"         provide that as the code's source map URL. If omitted, attach no\n"
+"         source map URL to the code (although the code may provide one itself,\n"
+"         via a //#sourceMappingURL comment).\n"
+"      sourceIsLazy: if present and true, indicates that, after compilation, \n"
+          "script source should not be cached by the JS engine and should be \n"
+          "lazily loaded from the embedding as-needed.\n"
+"      loadBytecode: if true, and if the source is a CacheEntryObject,\n"
+"         the bytecode would be loaded and decoded from the cache entry instead\n"
+"         of being parsed, then it would be executed as usual.\n"
+"      saveBytecode: if true, and if the source is a CacheEntryObject,\n"
+"         the bytecode would be encoded and saved into the cache entry after\n"
+"         the script execution.\n"
+"      assertEqBytecode: if true, and if both loadBytecode and saveBytecode are \n"
+"         true, then the loaded bytecode and the encoded bytecode are compared.\n"
+"         and an assertion is raised if they differ.\n"
+),
+
+    JS_FN_HELP("run", Run, 1, 0,
+"run('foo.js')",
+"  Run the file named by the first argument, returning the number of\n"
+"  of milliseconds spent compiling and executing it."),
+
+    JS_FN_HELP("readline", ReadLine, 0, 0,
+"readline()",
+"  Read a single line from stdin."),
+
+    JS_FN_HELP("readlineBuf", ReadLineBuf, 1, 0,
+"readlineBuf([ buf ])",
+"  Emulate readline() on the specified string. The first call with a string\n"
+"  argument sets the source buffer. Subsequent calls without an argument\n"
+"  then read from this buffer line by line.\n"),
+
+    JS_FN_HELP("print", Print, 0, 0,
+"print([exp ...])",
+"  Evaluate and print expressions to stdout."),
+
+    JS_FN_HELP("printErr", PrintErr, 0, 0,
+"printErr([exp ...])",
+"  Evaluate and print expressions to stderr."),
+
+    JS_FN_HELP("putstr", PutStr, 0, 0,
+"putstr([exp])",
+"  Evaluate and print expression without newline."),
+
+    JS_FN_HELP("dateNow", Now, 0, 0,
+"dateNow()",
+"  Return the current time with sub-ms precision."),
+
+    JS_FN_HELP("help", Help, 0, 0,
+"help([name ...])",
+"  Display usage and help messages."),
+
+    JS_FN_HELP("quit", Quit, 0, 0,
+"quit()",
+"  Quit the shell."),
+
+    JS_FN_HELP("assertEq", AssertEq, 2, 0,
+"assertEq(actual, expected[, msg])",
+"  Throw if the first two arguments are not the same (both +0 or both -0,\n"
+"  both NaN, or non-zero and ===)."),
+
+    JS_FN_HELP("startTimingMutator", StartTimingMutator, 0, 0,
+"startTimingMutator()",
+"  Start accounting time to mutator vs GC."),
+
+    JS_FN_HELP("stopTimingMutator", StopTimingMutator, 0, 0,
+"stopTimingMutator()",
+"  Stop accounting time to mutator vs GC and dump the results."),
+
+    JS_FN_HELP("throwError", ThrowError, 0, 0,
+"throwError()",
+"  Throw an error from JS_ReportError."),
+
+#ifdef DEBUG
+    JS_FN_HELP("disassemble", DisassembleToString, 1, 0,
+"disassemble([fun/code])",
+"  Return the disassembly for the given function or code.\n"
+"  All disassembly functions take these options as leading string arguments:\n"
+"    \"-r\" (disassemble recursively)\n"
+"    \"-l\" (show line numbers)\n"
+"    \"-S\" (omit source notes)"),
+
+    JS_FN_HELP("dis", Disassemble, 1, 0,
+"dis([fun/code])",
+"  Disassemble functions into bytecodes."),
+
+    JS_FN_HELP("disfile", DisassFile, 1, 0,
+"disfile('foo.js')",
+"  Disassemble script file into bytecodes.\n"),
+
+    JS_FN_HELP("dissrc", DisassWithSrc, 1, 0,
+"dissrc([fun/code])",
+"  Disassemble functions with source lines."),
+
+    JS_FN_HELP("notes", Notes, 1, 0,
+"notes([fun])",
+"  Show source notes for functions."),
+
+    JS_FN_HELP("stackDump", StackDump, 3, 0,
+"stackDump(showArgs, showLocals, showThisProps)",
+"  Tries to print a lot of information about the current stack. \n"
+"  Similar to the DumpJSStack() function in the browser."),
+
+#endif
+    JS_FN_HELP("intern", Intern, 1, 0,
+"intern(str)",
+"  Internalize str in the atom table."),
+
+    JS_FN_HELP("getslx", GetSLX, 1, 0,
+"getslx(obj)",
+"  Get script line extent."),
+
+    JS_FN_HELP("evalcx", EvalInContext, 1, 0,
+"evalcx(s[, o])",
+"  Evaluate s in optional sandbox object o.\n"
+"  if (s == '' && !o) return new o with eager standard classes\n"
+"  if (s == 'lazy' && !o) return new o with lazy standard classes"),
+
+    JS_FN_HELP("evalInWorker", EvalInWorker, 1, 0,
+"evalInWorker(str)",
+"  Evaluate 'str' in a separate thread with its own runtime.\n"),
+
+    JS_FN_HELP("getSharedArrayBuffer", GetSharedArrayBuffer, 0, 0,
+"getSharedArrayBuffer()",
+"  Retrieve the SharedArrayBuffer object from the cross-worker mailbox.\n"
+"  The object retrieved may not be identical to the object that was\n"
+"  installed, but it references the same shared memory.\n"
+"  getSharedArrayBuffer performs an ordering memory barrier.\n"),
+
+    JS_FN_HELP("setSharedArrayBuffer", SetSharedArrayBuffer, 0, 0,
+"setSharedArrayBuffer()",
+"  Install the SharedArrayBuffer object in the cross-worker mailbox.\n"
+"  setSharedArrayBuffer performs an ordering memory barrier.\n"),
+
+    JS_FN_HELP("shapeOf", ShapeOf, 1, 0,
+"shapeOf(obj)",
+"  Get the shape of obj (an implementation detail)."),
+
+    JS_FN_HELP("groupOf", GroupOf, 1, 0,
+"groupOf(obj)",
+"  Get the group of obj (an implementation detail)."),
+
+    JS_FN_HELP("unwrappedObjectsHaveSameShape", UnwrappedObjectsHaveSameShape, 2, 0,
+"unwrappedObjectsHaveSameShape(obj1, obj2)",
+"  Returns true iff obj1 and obj2 have the same shape, false otherwise. Both\n"
+"  objects are unwrapped first, so this can be used on objects from different\n"
+"  globals."),
+
+#ifdef DEBUG
+    JS_FN_HELP("arrayInfo", ArrayInfo, 1, 0,
+"arrayInfo(a1, a2, ...)",
+"  Report statistics about arrays."),
+#endif
+
+    JS_FN_HELP("sleep", Sleep_fn, 1, 0,
+"sleep(dt)",
+"  Sleep for dt seconds."),
+
+    JS_FN_HELP("compile", Compile, 1, 0,
+"compile(code)",
+"  Compiles a string to bytecode, potentially throwing."),
+
+    JS_FN_HELP("parseModule", ParseModule, 1, 0,
+"parseModule(code)",
+"  Parses source text as a module and returns a Module object."),
+
+    JS_FN_HELP("setModuleResolveHook", SetModuleResolveHook, 1, 0,
+"setModuleResolveHook(function(module, specifier) {})",
+"  Set the HostResolveImportedModule hook to |function|.\n"
+"  This hook is used to look up a previously loaded module object.  It should\n"
+"  be implemented by the module loader."),
+
+    JS_FN_HELP("getModuleLoadPath", GetModuleLoadPath, 0, 0,
+"getModuleLoadPath()",
+"  Return any --module-load-path argument passed to the shell.  Used by the\n"
+"  module loader.\n"),
+
+    JS_FN_HELP("parse", Parse, 1, 0,
+"parse(code)",
+"  Parses a string, potentially throwing."),
+
+    JS_FN_HELP("syntaxParse", SyntaxParse, 1, 0,
+"syntaxParse(code)",
+"  Check the syntax of a string, returning success value"),
+
+    JS_FN_HELP("offThreadCompileScript", OffThreadCompileScript, 1, 0,
+"offThreadCompileScript(code[, options])",
+"  Compile |code| on a helper thread. To wait for the compilation to finish\n"
+"  and run the code, call |runOffThreadScript|. If present, |options| may\n"
+"  have properties saying how the code should be compiled:\n"
+"      noScriptRval: use the no-script-rval compiler option (default: false)\n"
+"      fileName: filename for error messages and debug info\n"
+"      lineNumber: starting line number for error messages and debug info\n"
+"      columnNumber: starting column number for error messages and debug info\n"
+"      element: if present with value |v|, convert |v| to an object |o| and\n"
+"         mark the source as being attached to the DOM element |o|. If the\n"
+"         property is omitted or |v| is null, don't attribute the source to\n"
+"         any DOM element.\n"
+"      elementAttributeName: if present and not undefined, the name of\n"
+"         property of 'element' that holds this code. This is what\n"
+"         Debugger.Source.prototype.elementAttributeName returns.\n"),
+
+    JS_FN_HELP("runOffThreadScript", runOffThreadScript, 0, 0,
+"runOffThreadScript()",
+"  Wait for off-thread compilation to complete. If an error occurred,\n"
+"  throw the appropriate exception; otherwise, run the script and return\n"
+"  its value."),
+
+    JS_FN_HELP("offThreadCompileModule", OffThreadCompileModule, 1, 0,
+"offThreadCompileModule(code)",
+"  Compile |code| on a helper thread. To wait for the compilation to finish\n"
+"  and get the module object, call |finishOffThreadModule|."),
+
+    JS_FN_HELP("finishOffThreadModule", FinishOffThreadModule, 0, 0,
+"finishOffThreadModule()",
+"  Wait for off-thread compilation to complete. If an error occurred,\n"
+"  throw the appropriate exception; otherwise, return the module object"),
+
+    JS_FN_HELP("timeout", Timeout, 1, 0,
+"timeout([seconds], [func])",
+"  Get/Set the limit in seconds for the execution time for the current context.\n"
+"  A negative value (default) means that the execution time is unlimited.\n"
+"  If a second argument is provided, it will be invoked when the timer elapses.\n"
+"  Calling this function will replace any callback set by |setInterruptCallback|.\n"),
+
+    JS_FN_HELP("interruptIf", InterruptIf, 1, 0,
+"interruptIf(cond)",
+"  Requests interrupt callback if cond is true. If a callback function is set via\n"
+"  |timeout| or |setInterruptCallback|, it will be called. No-op otherwise."),
+
+    JS_FN_HELP("invokeInterruptCallback", InvokeInterruptCallbackWrapper, 0, 0,
+"invokeInterruptCallback(fun)",
+"  Forcefully set the interrupt flag and invoke the interrupt handler. If a\n"
+"  callback function is set via |timeout| or |setInterruptCallback|, it will\n"
+"  be called. Before returning, fun is called with the return value of the\n"
+"  interrupt handler."),
+
+    JS_FN_HELP("setInterruptCallback", SetInterruptCallback, 1, 0,
+"setInterruptCallback(func)",
+"  Sets func as the interrupt callback function.\n"
+"  Calling this function will replace any callback set by |timeout|.\n"),
+
+    JS_FN_HELP("enableLastWarning", EnableLastWarning, 0, 0,
+"enableLastWarning()",
+"  Enable storing the last warning."),
+
+    JS_FN_HELP("disableLastWarning", DisableLastWarning, 0, 0,
+"disableLastWarning()",
+"  Disable storing the last warning."),
+
+    JS_FN_HELP("getLastWarning", GetLastWarning, 0, 0,
+"getLastWarning()",
+"  Returns an object that represents the last warning."),
+
+    JS_FN_HELP("clearLastWarning", ClearLastWarning, 0, 0,
+"clearLastWarning()",
+"  Clear the last warning."),
+
+    JS_FN_HELP("elapsed", Elapsed, 0, 0,
+"elapsed()",
+"  Execution time elapsed for the current thread."),
+
+    JS_FN_HELP("decompileFunction", DecompileFunction, 1, 0,
+"decompileFunction(func)",
+"  Decompile a function."),
+
+    JS_FN_HELP("decompileThis", DecompileThisScript, 0, 0,
+"decompileThis()",
+"  Decompile the currently executing script."),
+
+    JS_FN_HELP("thisFilename", ThisFilename, 0, 0,
+"thisFilename()",
+"  Return the filename of the current script"),
+
+    JS_FN_HELP("newGlobal", NewGlobal, 1, 0,
+"newGlobal([options])",
+"  Return a new global object in a new compartment. If options\n"
+"  is given, it may have any of the following properties:\n"
+"      sameZoneAs: the compartment will be in the same zone as the given object (defaults to a new zone)\n"
+"      invisibleToDebugger: the global will be invisible to the debugger (default false)\n"
+"      principal: if present, its value converted to a number must be an\n"
+"         integer that fits in 32 bits; use that as the new compartment's\n"
+"         principal. Shell principals are toys, meant only for testing; one\n"
+"         shell principal subsumes another if its set bits are a superset of\n"
+"         the other's. Thus, a principal of 0 subsumes nothing, while a\n"
+"         principals of ~0 subsumes all other principals. The absence of a\n"
+"         principal is treated as if its bits were 0xffff, for subsumption\n"
+"         purposes. If this property is omitted, supply no principal."),
+
+    JS_FN_HELP("nukeCCW", NukeCCW, 1, 0,
+"nukeCCW(wrapper)",
+"  Nuke a CrossCompartmentWrapper, which turns it into a DeadProxyObject."),
+
+    JS_FN_HELP("createMappedArrayBuffer", CreateMappedArrayBuffer, 1, 0,
+"createMappedArrayBuffer(filename, [offset, [size]])",
+"  Create an array buffer that mmaps the given file."),
+
+    JS_FN_HELP("addPromiseReactions", AddPromiseReactions, 3, 0,
+"addPromiseReactions(promise, onResolve, onReject)",
+"  Calls the JS::AddPromiseReactions JSAPI function with the given arguments."),
+
+    JS_FN_HELP("getMaxArgs", GetMaxArgs, 0, 0,
+"getMaxArgs()",
+"  Return the maximum number of supported args for a call."),
+
+    JS_FN_HELP("objectEmulatingUndefined", ObjectEmulatingUndefined, 0, 0,
+"objectEmulatingUndefined()",
+"  Return a new object obj for which typeof obj === \"undefined\", obj == null\n"
+"  and obj == undefined (and vice versa for !=), and ToBoolean(obj) === false.\n"),
+
+    JS_FN_HELP("isCachingEnabled", IsCachingEnabled, 0, 0,
+"isCachingEnabled()",
+"  Return whether JS caching is enabled."),
+
+    JS_FN_HELP("setCachingEnabled", SetCachingEnabled, 1, 0,
+"setCachingEnabled(b)",
+"  Enable or disable JS caching."),
+
+    JS_FN_HELP("cacheEntry", CacheEntry, 1, 0,
+"cacheEntry(code)",
+"  Return a new opaque object which emulates a cache entry of a script.  This\n"
+"  object encapsulates the code and its cached content. The cache entry is filled\n"
+"  and read by the \"evaluate\" function by using it in place of the source, and\n"
+"  by setting \"saveBytecode\" and \"loadBytecode\" options."),
+
+    JS_FN_HELP("printProfilerEvents", PrintProfilerEvents, 0, 0,
+"printProfilerEvents()",
+"  Register a callback with the profiler that prints javascript profiler events\n"
+"  to stderr.  Callback is only registered if profiling is enabled."),
+
+    JS_FN_HELP("enableSingleStepProfiling", EnableSingleStepProfiling, 0, 0,
+"enableSingleStepProfiling()",
+"  This function will fail on platforms that don't support single-step profiling\n"
+"  (currently everything but ARM-simulator). When enabled, at every instruction a\n"
+"  backtrace will be recorded and stored in an array. Adjacent duplicate backtraces\n"
+"  are discarded."),
+
+    JS_FN_HELP("disableSingleStepProfiling", DisableSingleStepProfiling, 0, 0,
+"disableSingleStepProfiling()",
+"  Return the array of backtraces recorded by enableSingleStepProfiling."),
+
+    JS_FN_HELP("enableSPSProfiling", EnableSPSProfiling, 0, 0,
+"enableSPSProfiling()",
+"  Enables SPS instrumentation and corresponding assertions, with slow\n"
+"  assertions disabled.\n"),
+
+    JS_FN_HELP("enableSPSProfilingWithSlowAssertions", EnableSPSProfilingWithSlowAssertions, 0, 0,
+"enableSPSProfilingWithSlowAssertions()",
+"  Enables SPS instrumentation and corresponding assertions, with slow\n"
+"  assertions enabled.\n"),
+
+    JS_FN_HELP("disableSPSProfiling", DisableSPSProfiling, 0, 0,
+"disableSPSProfiling()",
+"  Disables SPS instrumentation"),
+
+    JS_FN_HELP("isLatin1", IsLatin1, 1, 0,
+"isLatin1(s)",
+"  Return true iff the string's characters are stored as Latin1."),
+
+    JS_FN_HELP("stackPointerInfo", StackPointerInfo, 0, 0,
+"stackPointerInfo()",
+"  Return an int32 value which corresponds to the offset of the latest stack\n"
+"  pointer, such that one can take the differences of 2 to estimate a frame-size."),
+
+    JS_FN_HELP("entryPoints", EntryPoints, 1, 0,
+"entryPoints(params)",
+"Carry out some JSAPI operation as directed by |params|, and return an array of\n"
+"objects describing which JavaScript entry points were invoked as a result.\n"
+"|params| is an object whose properties indicate what operation to perform. Here\n"
+"are the recognized groups of properties:\n"
+"\n"
+"{ function }: Call the object |params.function| with no arguments.\n"
+"\n"
+"{ object, property }: Fetch the property named |params.property| of\n"
+"|params.object|.\n"
+"\n"
+"{ ToString }: Apply JS::ToString to |params.toString|.\n"
+"\n"
+"{ ToNumber }: Apply JS::ToNumber to |params.toNumber|.\n"
+"\n"
+"{ eval }: Apply JS::Evaluate to |params.eval|.\n"
+"\n"
+"The return value is an array of strings, with one element for each\n"
+"JavaScript invocation that occurred as a result of the given\n"
+"operation. Each element is the name of the function invoked, or the\n"
+"string 'eval:FILENAME' if the code was invoked by 'eval' or something\n"
+"similar.\n"),
+
+    JS_FN_HELP("drainJobQueue", DrainJobQueue, 0, 0,
+"drainJobQueue()",
+"Take jobs from the shell's job queue in FIFO order and run them until the\n"
+"queue is empty.\n"),
+
+    JS_FN_HELP("setPromiseRejectionTrackerCallback", SetPromiseRejectionTrackerCallback, 1, 0,
+"setPromiseRejectionTrackerCallback()",
+"Sets the callback to be invoked whenever a Promise rejection is unhandled\n"
+"or a previously-unhandled rejection becomes handled."),
+
+#ifdef ENABLE_INTL_API
+    JS_FN_HELP("addIntlExtras", AddIntlExtras, 1, 0,
+"addIntlExtras(obj)",
+"Adds various not-yet-standardized Intl functions as properties on the\n"
+"provided object (this should generally be Intl itself).  The added\n"
+"functions and their behavior are experimental: don't depend upon them\n"
+"unless you're willing to update your code if these experimental APIs change\n"
+"underneath you."),
+#endif // ENABLE_INTL_API
+
+    JS_FS_HELP_END
+};
+
+static const JSFunctionSpecWithHelp fuzzing_unsafe_functions[] = {
+    JS_FN_HELP("clone", Clone, 1, 0,
+"clone(fun[, scope])",
+"  Clone function object."),
+
+    JS_FN_HELP("getSelfHostedValue", GetSelfHostedValue, 1, 0,
+"getSelfHostedValue()",
+"  Get a self-hosted value by its name. Note that these values don't get \n"
+"  cached, so repeatedly getting the same value creates multiple distinct clones."),
+
+    JS_FN_HELP("line2pc", LineToPC, 0, 0,
+"line2pc([fun,] line)",
+"  Map line number to PC."),
+
+    JS_FN_HELP("pc2line", PCToLine, 0, 0,
+"pc2line(fun[, pc])",
+"  Map PC to line number."),
+
+    JS_FN_HELP("nestedShell", NestedShell, 0, 0,
+"nestedShell(shellArgs...)",
+"  Execute the given code in a new JS shell process, passing this nested shell\n"
+"  the arguments passed to nestedShell. argv[0] of the nested shell will be argv[0]\n"
+"  of the current shell (which is assumed to be the actual path to the shell.\n"
+"  arguments[0] (of the call to nestedShell) will be argv[1], arguments[1] will\n"
+"  be argv[2], etc."),
+
+    JS_INLINABLE_FN_HELP("assertFloat32", testingFunc_assertFloat32, 2, 0, TestAssertFloat32,
+"assertFloat32(value, isFloat32)",
+"  In IonMonkey only, asserts that value has (resp. hasn't) the MIRType::Float32 if isFloat32 is true (resp. false)."),
+
+    JS_INLINABLE_FN_HELP("assertRecoveredOnBailout", testingFunc_assertRecoveredOnBailout, 2, 0,
+TestAssertRecoveredOnBailout,
+"assertRecoveredOnBailout(var)",
+"  In IonMonkey only, asserts that variable has RecoveredOnBailout flag."),
+
+    JS_FN_HELP("withSourceHook", WithSourceHook, 1, 0,
+"withSourceHook(hook, fun)",
+"  Set this JS runtime's lazy source retrieval hook (that is, the hook\n"
+"  used to find sources compiled with |CompileOptions::LAZY_SOURCE|) to\n"
+"  |hook|; call |fun| with no arguments; and then restore the runtime's\n"
+"  original hook. Return or throw whatever |fun| did. |hook| gets\n"
+"  passed the requested code's URL, and should return a string.\n"
+"\n"
+"  Notes:\n"
+"\n"
+"  1) SpiderMonkey may assert if the returned code isn't close enough\n"
+"  to the script's real code, so this function is not fuzzer-safe.\n"
+"\n"
+"  2) The runtime can have only one source retrieval hook active at a\n"
+"  time. If |fun| is not careful, |hook| could be asked to retrieve the\n"
+"  source code for compilations that occurred long before it was set,\n"
+"  and that it knows nothing about. The reverse applies as well: the\n"
+"  original hook, that we reinstate after the call to |fun| completes,\n"
+"  might be asked for the source code of compilations that |fun|\n"
+"  performed, and which, presumably, only |hook| knows how to find.\n"),
+
+    JS_FN_HELP("wrapWithProto", WrapWithProto, 2, 0,
+"wrapWithProto(obj)",
+"  Wrap an object into a noop wrapper with prototype semantics.\n"
+"  Note: This is not fuzzing safe because it can be used to construct\n"
+"        deeply nested wrapper chains that cannot exist in the wild."),
+
+    JS_FN_HELP("trackedOpts", ReflectTrackedOptimizations, 1, 0,
+"trackedOpts(fun)",
+"  Returns an object describing the tracked optimizations of |fun|, if\n"
+"  any. If |fun| is not a scripted function or has not been compiled by\n"
+"  Ion, null is returned."),
+
+    JS_FN_HELP("dumpScopeChain", DumpScopeChain, 1, 0,
+"dumpScopeChain(obj)",
+"  Prints the scope chain of an interpreted function or a module."),
+
+    JS_FN_HELP("crash", Crash, 0, 0,
+"crash([message])",
+"  Crashes the process with a MOZ_CRASH."),
+
+    JS_FN_HELP("setARMHwCapFlags", SetARMHwCapFlags, 1, 0,
+"setARMHwCapFlags(\"flag1,flag2 flag3\")",
+"  On non-ARM, no-op. On ARM, set the hardware capabilities. The list of \n"
+"  flags is available by calling this function with \"help\" as the flag's name"),
+
+    JS_FN_HELP("wasmLoop", WasmLoop, 2, 0,
+"wasmLoop(filename, imports)",
+"  Performs an AFL-style persistent loop reading data from the given file and passing it\n"
+"  to the 'wasmEval' function together with the specified imports object."),
+
+    JS_FS_HELP_END
+};
+
+static const JSFunctionSpecWithHelp console_functions[] = {
+    JS_FN_HELP("log", Print, 0, 0,
+"log([exp ...])",
+"  Evaluate and print expressions to stdout.\n"
+"  This function is an alias of the print() function."),
+    JS_FS_HELP_END
+};
+
+bool
+DefineConsole(JSContext* cx, HandleObject global)
+{
+    RootedObject obj(cx, JS_NewPlainObject(cx));
+    return obj &&
+           JS_DefineFunctionsWithHelp(cx, obj, console_functions) &&
+           JS_DefineProperty(cx, global, "console", obj, 0);
+}
+
+#ifdef MOZ_PROFILING
+# define PROFILING_FUNCTION_COUNT 5
+# ifdef MOZ_CALLGRIND
+#  define CALLGRIND_FUNCTION_COUNT 3
+# else
+#  define CALLGRIND_FUNCTION_COUNT 0
+# endif
+# ifdef MOZ_VTUNE
+#  define VTUNE_FUNCTION_COUNT 4
+# else
+#  define VTUNE_FUNCTION_COUNT 0
+# endif
+# define EXTERNAL_FUNCTION_COUNT (PROFILING_FUNCTION_COUNT + CALLGRIND_FUNCTION_COUNT + VTUNE_FUNCTION_COUNT)
+#else
+# define EXTERNAL_FUNCTION_COUNT 0
+#endif
+
+#undef PROFILING_FUNCTION_COUNT
+#undef CALLGRIND_FUNCTION_COUNT
+#undef VTUNE_FUNCTION_COUNT
+#undef EXTERNAL_FUNCTION_COUNT
+
+static bool
+PrintHelpString(JSContext* cx, HandleValue v)
+{
+    JSString* str = v.toString();
+    MOZ_ASSERT(gOutFile->isOpen());
+
+    JSLinearString* linear = str->ensureLinear(cx);
+    if (!linear)
+        return false;
+
+    JS::AutoCheckCannotGC nogc;
+    if (linear->hasLatin1Chars()) {
+        for (const Latin1Char* p = linear->latin1Chars(nogc); *p; p++)
+            fprintf(gOutFile->fp, "%c", char(*p));
+    } else {
+        for (const char16_t* p = linear->twoByteChars(nogc); *p; p++)
+            fprintf(gOutFile->fp, "%c", char(*p));
+    }
+    fprintf(gOutFile->fp, "\n");
+
+    return true;
+}
+
+static bool
+PrintHelp(JSContext* cx, HandleObject obj)
+{
+    RootedValue usage(cx);
+    if (!JS_GetProperty(cx, obj, "usage", &usage))
+        return false;
+    RootedValue help(cx);
+    if (!JS_GetProperty(cx, obj, "help", &help))
+        return false;
+
+    if (!usage.isString() || !help.isString())
+        return true;
+
+    return PrintHelpString(cx, usage) && PrintHelpString(cx, help);
+}
+
+static bool
+PrintEnumeratedHelp(JSContext* cx, HandleObject obj, bool brief)
+{
+    AutoIdVector idv(cx);
+    if (!GetPropertyKeys(cx, obj, JSITER_OWNONLY | JSITER_HIDDEN, &idv))
+        return false;
+
+    for (size_t i = 0; i < idv.length(); i++) {
+        RootedValue v(cx);
+        RootedId id(cx, idv[i]);
+        if (!JS_GetPropertyById(cx, obj, id, &v))
+            return false;
+        if (v.isObject()) {
+            RootedObject funcObj(cx, &v.toObject());
+            if (!PrintHelp(cx, funcObj))
+                return false;
+        }
+    }
+
+    return true;
+}
+
+static bool
+Help(JSContext* cx, unsigned argc, Value* vp)
+{
+    if (!gOutFile->isOpen()) {
+        JS_ReportErrorASCII(cx, "output file is closed");
+        return false;
+    }
+
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    RootedObject obj(cx);
+    if (args.length() == 0) {
+        fprintf(gOutFile->fp, "%s\n", JS_GetImplementationVersion());
+
+        RootedObject global(cx, JS::CurrentGlobalOrNull(cx));
+        if (!PrintEnumeratedHelp(cx, global, false))
+            return false;
+    } else {
+        for (unsigned i = 0; i < args.length(); i++) {
+            if (args[i].isPrimitive()) {
+                JS_ReportErrorASCII(cx, "primitive arg");
+                return false;
+            }
+            obj = args[i].toObjectOrNull();
+            if (!PrintHelp(cx, obj))
+                return false;
+        }
+    }
+
+    args.rval().setUndefined();
+    return true;
+}
+
+static const JSErrorFormatString jsShell_ErrorFormatString[JSShellErr_Limit] = {
+#define MSG_DEF(name, count, exception, format) \
+    { #name, format, count, JSEXN_ERR } ,
+#include "jsshell.msg"
+#undef MSG_DEF
+};
+
+const JSErrorFormatString*
+js::shell::my_GetErrorMessage(void* userRef, const unsigned errorNumber)
+{
+    if (errorNumber == 0 || errorNumber >= JSShellErr_Limit)
+        return nullptr;
+
+    return &jsShell_ErrorFormatString[errorNumber];
+}
+
+static bool
+CreateLastWarningObject(JSContext* cx, JSErrorReport* report)
+{
+    RootedObject warningObj(cx, JS_NewObject(cx, nullptr));
+    if (!warningObj)
+        return false;
+
+    RootedString nameStr(cx);
+    if (report->exnType == JSEXN_WARN)
+        nameStr = JS_NewStringCopyZ(cx, "Warning");
+    else
+        nameStr = GetErrorTypeName(cx, report->exnType);
+    if (!nameStr)
+        return false;
+    RootedValue nameVal(cx, StringValue(nameStr));
+    if (!DefineProperty(cx, warningObj, cx->names().name, nameVal))
+        return false;
+
+    RootedString messageStr(cx, report->newMessageString(cx));
+    if (!messageStr)
+        return false;
+    RootedValue messageVal(cx, StringValue(messageStr));
+    if (!DefineProperty(cx, warningObj, cx->names().message, messageVal))
+        return false;
+
+    RootedValue linenoVal(cx, Int32Value(report->lineno));
+    if (!DefineProperty(cx, warningObj, cx->names().lineNumber, linenoVal))
+        return false;
+
+    RootedValue columnVal(cx, Int32Value(report->column));
+    if (!DefineProperty(cx, warningObj, cx->names().columnNumber, columnVal))
+        return false;
+
+    GetShellContext(cx)->lastWarning.setObject(*warningObj);
+    return true;
+}
+
+static FILE*
+ErrorFilePointer()
+{
+    if (gErrFile->isOpen())
+        return gErrFile->fp;
+
+    fprintf(stderr, "error file is closed; falling back to stderr\n");
+    return stderr;
+}
+
+static bool
+PrintStackTrace(JSContext* cx, HandleValue exn)
+{
+    if (!exn.isObject())
+        return false;
+
+    Maybe<JSAutoCompartment> ac;
+    RootedObject exnObj(cx, &exn.toObject());
+    if (IsCrossCompartmentWrapper(exnObj)) {
+        exnObj = UncheckedUnwrap(exnObj);
+        ac.emplace(cx, exnObj);
+    }
+
+    // Ignore non-ErrorObject thrown by |throw| statement.
+    if (!exnObj->is<ErrorObject>())
+        return true;
+
+    // Exceptions thrown while compiling top-level script have no stack.
+    RootedObject stackObj(cx, exnObj->as<ErrorObject>().stack());
+    if (!stackObj)
+        return true;
+
+    RootedString stackStr(cx);
+    if (!BuildStackString(cx, stackObj, &stackStr, 2))
+        return false;
+
+    UniqueChars stack(JS_EncodeStringToUTF8(cx, stackStr));
+    if (!stack)
+        return false;
+
+    FILE* fp = ErrorFilePointer();
+    fputs("Stack:\n", fp);
+    fputs(stack.get(), fp);
+
+    return true;
+}
+
+js::shell::AutoReportException::~AutoReportException()
+{
+    if (!JS_IsExceptionPending(cx))
+        return;
+
+    // Get exception object before printing and clearing exception.
+    RootedValue exn(cx);
+    (void) JS_GetPendingException(cx, &exn);
+
+    JS_ClearPendingException(cx);
+
+    ShellContext* sc = GetShellContext(cx);
+    js::ErrorReport report(cx);
+    if (!report.init(cx, exn, js::ErrorReport::WithSideEffects)) {
+        fprintf(stderr, "out of memory initializing ErrorReport\n");
+        fflush(stderr);
+        JS_ClearPendingException(cx);
+        return;
+    }
+
+    MOZ_ASSERT(!JSREPORT_IS_WARNING(report.report()->flags));
+
+    FILE* fp = ErrorFilePointer();
+    PrintError(cx, fp, report.toStringResult(), report.report(), reportWarnings);
+
+    {
+        JS::AutoSaveExceptionState savedExc(cx);
+        if (!PrintStackTrace(cx, exn))
+            fputs("(Unable to print stack trace)\n", fp);
+        savedExc.restore();
+    }
+
+    if (report.report()->errorNumber == JSMSG_OUT_OF_MEMORY)
+        sc->exitCode = EXITCODE_OUT_OF_MEMORY;
+    else
+        sc->exitCode = EXITCODE_RUNTIME_ERROR;
+
+    JS_ClearPendingException(cx);
+}
+
+void
+js::shell::WarningReporter(JSContext* cx, JSErrorReport* report)
+{
+    ShellContext* sc = GetShellContext(cx);
+    FILE* fp = ErrorFilePointer();
+
+    MOZ_ASSERT(report);
+    MOZ_ASSERT(JSREPORT_IS_WARNING(report->flags));
+
+    if (sc->lastWarningEnabled) {
+        JS::AutoSaveExceptionState savedExc(cx);
+        if (!CreateLastWarningObject(cx, report)) {
+            fputs("Unhandled error happened while creating last warning object.\n", fp);
+            fflush(fp);
+        }
+        savedExc.restore();
+    }
+
+    // Print the warning.
+    PrintError(cx, fp, JS::ConstUTF8CharsZ(), report, reportWarnings);
+}
+
+static bool
+global_enumerate(JSContext* cx, HandleObject obj)
+{
+#ifdef LAZY_STANDARD_CLASSES
+    return JS_EnumerateStandardClasses(cx, obj);
+#else
+    return true;
+#endif
+}
+
+static bool
+global_resolve(JSContext* cx, HandleObject obj, HandleId id, bool* resolvedp)
+{
+#ifdef LAZY_STANDARD_CLASSES
+    if (!JS_ResolveStandardClass(cx, obj, id, resolvedp))
+        return false;
+#endif
+    return true;
+}
+
+static bool
+global_mayResolve(const JSAtomState& names, jsid id, JSObject* maybeObj)
+{
+    return JS_MayResolveStandardClass(names, id, maybeObj);
+}
+
+static const JSClassOps global_classOps = {
+    nullptr, nullptr, nullptr, nullptr,
+    global_enumerate, global_resolve, global_mayResolve,
+    nullptr,
+    nullptr, nullptr, nullptr,
+    JS_GlobalObjectTraceHook
+};
+
+static const JSClass global_class = {
+    "global", JSCLASS_GLOBAL_FLAGS,
+    &global_classOps
+};
+
+/*
+ * Define a FakeDOMObject constructor. It returns an object with a getter,
+ * setter and method with attached JitInfo. This object can be used to test
+ * IonMonkey DOM optimizations in the shell.
+ */
+static const uint32_t DOM_OBJECT_SLOT = 0;
+
+static bool
+dom_genericGetter(JSContext* cx, unsigned argc, JS::Value* vp);
+
+static bool
+dom_genericSetter(JSContext* cx, unsigned argc, JS::Value* vp);
+
+static bool
+dom_genericMethod(JSContext* cx, unsigned argc, JS::Value* vp);
+
+#ifdef DEBUG
+static const JSClass* GetDomClass();
+#endif
+
+static bool
+dom_get_x(JSContext* cx, HandleObject obj, void* self, JSJitGetterCallArgs args)
+{
+    MOZ_ASSERT(JS_GetClass(obj) == GetDomClass());
+    MOZ_ASSERT(self == (void*)0x1234);
+    args.rval().set(JS_NumberValue(double(3.14)));
+    return true;
+}
+
+static bool
+dom_set_x(JSContext* cx, HandleObject obj, void* self, JSJitSetterCallArgs args)
+{
+    MOZ_ASSERT(JS_GetClass(obj) == GetDomClass());
+    MOZ_ASSERT(self == (void*)0x1234);
+    return true;
+}
+
+static bool
+dom_doFoo(JSContext* cx, HandleObject obj, void* self, const JSJitMethodCallArgs& args)
+{
+    MOZ_ASSERT(JS_GetClass(obj) == GetDomClass());
+    MOZ_ASSERT(self == (void*)0x1234);
+
+    /* Just return args.length(). */
+    args.rval().setInt32(args.length());
+    return true;
+}
+
+static const JSJitInfo dom_x_getterinfo = {
+    { (JSJitGetterOp)dom_get_x },
+    { 0 },    /* protoID */
+    { 0 },    /* depth */
+    JSJitInfo::AliasNone, /* aliasSet */
+    JSJitInfo::Getter,
+    JSVAL_TYPE_UNKNOWN, /* returnType */
+    true,     /* isInfallible. False in setters. */
+    true,     /* isMovable */
+    true,     /* isEliminatable */
+    false,    /* isAlwaysInSlot */
+    false,    /* isLazilyCachedInSlot */
+    false,    /* isTypedMethod */
+    0         /* slotIndex */
+};
+
+static const JSJitInfo dom_x_setterinfo = {
+    { (JSJitGetterOp)dom_set_x },
+    { 0 },    /* protoID */
+    { 0 },    /* depth */
+    JSJitInfo::Setter,
+    JSJitInfo::AliasEverything, /* aliasSet */
+    JSVAL_TYPE_UNKNOWN, /* returnType */
+    false,    /* isInfallible. False in setters. */
+    false,    /* isMovable. */
+    false,    /* isEliminatable. */
+    false,    /* isAlwaysInSlot */
+    false,    /* isLazilyCachedInSlot */
+    false,    /* isTypedMethod */
+    0         /* slotIndex */
+};
+
+static const JSJitInfo doFoo_methodinfo = {
+    { (JSJitGetterOp)dom_doFoo },
+    { 0 },    /* protoID */
+    { 0 },    /* depth */
+    JSJitInfo::Method,
+    JSJitInfo::AliasEverything, /* aliasSet */
+    JSVAL_TYPE_UNKNOWN, /* returnType */
+    false,    /* isInfallible. False in setters. */
+    false,    /* isMovable */
+    false,    /* isEliminatable */
+    false,    /* isAlwaysInSlot */
+    false,    /* isLazilyCachedInSlot */
+    false,    /* isTypedMethod */
+    0         /* slotIndex */
+};
+
+static const JSPropertySpec dom_props[] = {
+    {"x",
+     JSPROP_SHARED | JSPROP_ENUMERATE,
+     { {
+        { { dom_genericGetter, &dom_x_getterinfo } },
+        { { dom_genericSetter, &dom_x_setterinfo } }
+     } },
+    },
+    JS_PS_END
+};
+
+static const JSFunctionSpec dom_methods[] = {
+    JS_FNINFO("doFoo", dom_genericMethod, &doFoo_methodinfo, 3, JSPROP_ENUMERATE),
+    JS_FS_END
+};
+
+static const JSClass dom_class = {
+    "FakeDOMObject", JSCLASS_IS_DOMJSCLASS | JSCLASS_HAS_RESERVED_SLOTS(2)
+};
+
+#ifdef DEBUG
+static const JSClass* GetDomClass() {
+    return &dom_class;
+}
+#endif
+
+static bool
+dom_genericGetter(JSContext* cx, unsigned argc, JS::Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedObject obj(cx, JS_THIS_OBJECT(cx, vp));
+    if (!obj)
+        return false;
+
+    if (JS_GetClass(obj) != &dom_class) {
+        args.rval().set(UndefinedValue());
+        return true;
+    }
+
+    JS::Value val = js::GetReservedSlot(obj, DOM_OBJECT_SLOT);
+
+    const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+    MOZ_ASSERT(info->type() == JSJitInfo::Getter);
+    JSJitGetterOp getter = info->getter;
+    return getter(cx, obj, val.toPrivate(), JSJitGetterCallArgs(args));
+}
+
+static bool
+dom_genericSetter(JSContext* cx, unsigned argc, JS::Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedObject obj(cx, JS_THIS_OBJECT(cx, vp));
+    if (!obj)
+        return false;
+
+    MOZ_ASSERT(args.length() == 1);
+
+    if (JS_GetClass(obj) != &dom_class) {
+        args.rval().set(UndefinedValue());
+        return true;
+    }
+
+    JS::Value val = js::GetReservedSlot(obj, DOM_OBJECT_SLOT);
+
+    const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+    MOZ_ASSERT(info->type() == JSJitInfo::Setter);
+    JSJitSetterOp setter = info->setter;
+    if (!setter(cx, obj, val.toPrivate(), JSJitSetterCallArgs(args)))
+        return false;
+    args.rval().set(UndefinedValue());
+    return true;
+}
+
+static bool
+dom_genericMethod(JSContext* cx, unsigned argc, JS::Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+    RootedObject obj(cx, JS_THIS_OBJECT(cx, vp));
+    if (!obj)
+        return false;
+
+    if (JS_GetClass(obj) != &dom_class) {
+        args.rval().set(UndefinedValue());
+        return true;
+    }
+
+    JS::Value val = js::GetReservedSlot(obj, DOM_OBJECT_SLOT);
+
+    const JSJitInfo* info = FUNCTION_VALUE_TO_JITINFO(args.calleev());
+    MOZ_ASSERT(info->type() == JSJitInfo::Method);
+    JSJitMethodOp method = info->method;
+    return method(cx, obj, val.toPrivate(), JSJitMethodCallArgs(args));
+}
+
+static void
+InitDOMObject(HandleObject obj)
+{
+    /* Fow now just initialize to a constant we can check. */
+    SetReservedSlot(obj, DOM_OBJECT_SLOT, PrivateValue((void*)0x1234));
+}
+
+static bool
+dom_constructor(JSContext* cx, unsigned argc, JS::Value* vp)
+{
+    CallArgs args = CallArgsFromVp(argc, vp);
+
+    RootedObject callee(cx, &args.callee());
+    RootedValue protov(cx);
+    if (!GetProperty(cx, callee, callee, cx->names().prototype, &protov))
+        return false;
+
+    if (!protov.isObject()) {
+        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_BAD_PROTOTYPE,
+                                  "FakeDOMObject");
+        return false;
+    }
+
+    RootedObject proto(cx, &protov.toObject());
+    RootedObject domObj(cx, JS_NewObjectWithGivenProto(cx, &dom_class, proto));
+    if (!domObj)
+        return false;
+
+    InitDOMObject(domObj);
+
+    args.rval().setObject(*domObj);
+    return true;
+}
+
+static bool
+InstanceClassHasProtoAtDepth(const Class* clasp, uint32_t protoID, uint32_t depth)
+{
+    /* There's only a single (fake) DOM object in the shell, so just return true. */
+    return true;
+}
+
+class ScopedFileDesc
+{
+    intptr_t fd_;
+  public:
+    enum LockType { READ_LOCK, WRITE_LOCK };
+    ScopedFileDesc(int fd, LockType lockType)
+      : fd_(fd)
+    {
+        if (fd == -1)
+            return;
+        if (!jsCacheOpened.compareExchange(false, true)) {
+            close(fd_);
+            fd_ = -1;
+            return;
+        }
+    }
+    ~ScopedFileDesc() {
+        if (fd_ == -1)
+            return;
+        MOZ_ASSERT(jsCacheOpened == true);
+        jsCacheOpened = false;
+        close(fd_);
+    }
+    operator intptr_t() const {
+        return fd_;
+    }
+    intptr_t forget() {
+        intptr_t ret = fd_;
+        fd_ = -1;
+        return ret;
+    }
+};
+
+// To guard against corrupted cache files generated by previous crashes, write
+// asmJSCacheCookie to the first uint32_t of the file only after the file is
+// fully serialized and flushed to disk.
+static const uint32_t asmJSCacheCookie = 0xabbadaba;
+
+static bool
+ShellOpenAsmJSCacheEntryForRead(HandleObject global, const char16_t* begin, const char16_t* limit,
+                                size_t* serializedSizeOut, const uint8_t** memoryOut,
+                                intptr_t* handleOut)
+{
+    if (!jsCachingEnabled || !jsCacheAsmJSPath)
+        return false;
+
+    ScopedFileDesc fd(open(jsCacheAsmJSPath, O_RDWR), ScopedFileDesc::READ_LOCK);
+    if (fd == -1)
+        return false;
+
+    // Get the size and make sure we can dereference at least one uint32_t.
+    off_t off = lseek(fd, 0, SEEK_END);
+    if (off == -1 || off < (off_t)sizeof(uint32_t))
+        return false;
+
+    // Map the file into memory.
+    void* memory;
+#ifdef XP_WIN
+    HANDLE fdOsHandle = (HANDLE)_get_osfhandle(fd);
+    HANDLE fileMapping = CreateFileMapping(fdOsHandle, nullptr, PAGE_READWRITE, 0, 0, nullptr);
+    if (!fileMapping)
+        return false;
+
+    memory = MapViewOfFile(fileMapping, FILE_MAP_READ, 0, 0, 0);
+    CloseHandle(fileMapping);
+    if (!memory)
+        return false;
+#else
+    memory = mmap(nullptr, off, PROT_READ, MAP_SHARED, fd, 0);
+    if (memory == MAP_FAILED)
+        return false;
+#endif
+
+    // Perform check described by asmJSCacheCookie comment.
+    if (*(uint32_t*)memory != asmJSCacheCookie) {
+#ifdef XP_WIN
+        UnmapViewOfFile(memory);
+#else
+        munmap(memory, off);
+#endif
+        return false;
+    }
+
+    // The embedding added the cookie so strip it off of the buffer returned to
+    // the JS engine.
+    *serializedSizeOut = off - sizeof(uint32_t);
+    *memoryOut = (uint8_t*)memory + sizeof(uint32_t);
+    *handleOut = fd.forget();
+    return true;
+}
+
+static void
+ShellCloseAsmJSCacheEntryForRead(size_t serializedSize, const uint8_t* memory, intptr_t handle)
+{
+    // Undo the cookie adjustment done when opening the file.
+    memory -= sizeof(uint32_t);
+    serializedSize += sizeof(uint32_t);
+
+    // Release the memory mapping and file.
+#ifdef XP_WIN
+    UnmapViewOfFile(const_cast<uint8_t*>(memory));
+#else
+    munmap(const_cast<uint8_t*>(memory), serializedSize);
+#endif
+
+    MOZ_ASSERT(jsCacheOpened == true);
+    jsCacheOpened = false;
+    close(handle);
+}
+
+static JS::AsmJSCacheResult
+ShellOpenAsmJSCacheEntryForWrite(HandleObject global, bool installed,
+                                 const char16_t* begin, const char16_t* end,
+                                 size_t serializedSize, uint8_t** memoryOut, intptr_t* handleOut)
+{
+    if (!jsCachingEnabled || !jsCacheAsmJSPath)
+        return JS::AsmJSCache_Disabled_ShellFlags;
+
+    // Create the cache directory if it doesn't already exist.
+    struct stat dirStat;
+    if (stat(jsCacheDir, &dirStat) == 0) {
+        if (!(dirStat.st_mode & S_IFDIR))
+            return JS::AsmJSCache_InternalError;
+    } else {
+#ifdef XP_WIN
+        if (mkdir(jsCacheDir) != 0)
+            return JS::AsmJSCache_InternalError;
+#else
+        if (mkdir(jsCacheDir, 0777) != 0)
+            return JS::AsmJSCache_InternalError;
+#endif
+    }
+
+    ScopedFileDesc fd(open(jsCacheAsmJSPath, O_CREAT|O_RDWR, 0660), ScopedFileDesc::WRITE_LOCK);
+    if (fd == -1)
+        return JS::AsmJSCache_InternalError;
+
+    // Include extra space for the asmJSCacheCookie.
+    serializedSize += sizeof(uint32_t);
+
+    // Resize the file to the appropriate size after zeroing their contents.
+#ifdef XP_WIN
+    if (chsize(fd, 0))
+        return JS::AsmJSCache_InternalError;
+    if (chsize(fd, serializedSize))
+        return JS::AsmJSCache_InternalError;
+#else
+    if (ftruncate(fd, 0))
+        return JS::AsmJSCache_InternalError;
+    if (ftruncate(fd, serializedSize))
+        return JS::AsmJSCache_InternalError;
+#endif
+
+    // Map the file into memory.
+    void* memory;
+#ifdef XP_WIN
+    HANDLE fdOsHandle = (HANDLE)_get_osfhandle(fd);
+    HANDLE fileMapping = CreateFileMapping(fdOsHandle, nullptr, PAGE_READWRITE, 0, 0, nullptr);
+    if (!fileMapping)
+        return JS::AsmJSCache_InternalError;
+
+    memory = MapViewOfFile(fileMapping, FILE_MAP_WRITE, 0, 0, 0);
+    CloseHandle(fileMapping);
+    if (!memory)
+        return JS::AsmJSCache_InternalError;
+    MOZ_ASSERT(*(uint32_t*)memory == 0);
+#else
+    memory = mmap(nullptr, serializedSize, PROT_READ, MAP_SHARED, fd, 0);
+    if (memory == MAP_FAILED)
+        return JS::AsmJSCache_InternalError;
+    MOZ_ASSERT(*(uint32_t*)memory == 0);
+    if (mprotect(memory, serializedSize, PROT_WRITE))
+        return JS::AsmJSCache_InternalError;
+#endif
+
+    // The embedding added the cookie so strip it off of the buffer returned to
+    // the JS engine. The asmJSCacheCookie will be written on close, below.
+    *memoryOut = (uint8_t*)memory + sizeof(uint32_t);
+    *handleOut = fd.forget();
+    return JS::AsmJSCache_Success;
+}
+
+static void
+ShellCloseAsmJSCacheEntryForWrite(size_t serializedSize, uint8_t* memory, intptr_t handle)
+{
+    // Undo the cookie adjustment done when opening the file.
+    memory -= sizeof(uint32_t);
+    serializedSize += sizeof(uint32_t);
+
+    // Write the magic cookie value after flushing the entire cache entry.
+#ifdef XP_WIN
+    FlushViewOfFile(memory, serializedSize);
+    FlushFileBuffers(HANDLE(_get_osfhandle(handle)));
+#else
+    msync(memory, serializedSize, MS_SYNC);
+#endif
+
+    MOZ_ASSERT(*(uint32_t*)memory == 0);
+    *(uint32_t*)memory = asmJSCacheCookie;
+
+    // Free the memory mapping and file.
+#ifdef XP_WIN
+    UnmapViewOfFile(const_cast<uint8_t*>(memory));
+#else
+    munmap(memory, serializedSize);
+#endif
+
+    MOZ_ASSERT(jsCacheOpened == true);
+    jsCacheOpened = false;
+    close(handle);
+}
+
+static bool
+ShellBuildId(JS::BuildIdCharVector* buildId)
+{
+    // The browser embeds the date into the buildid and the buildid is embedded
+    // in the binary, so every 'make' necessarily builds a new firefox binary.
+    // Fortunately, the actual firefox executable is tiny -- all the code is in
+    // libxul.so and other shared modules -- so this isn't a big deal. Not so
+    // for the statically-linked JS shell. To avoid recompiling js.cpp and
+    // re-linking 'js' on every 'make', we use a constant buildid and rely on
+    // the shell user to manually clear the cache (deleting the dir passed to
+    // --js-cache) between cache-breaking updates. Note: jit_tests.py does this
+    // on every run).
+    const char buildid[] = "JS-shell";
+    return buildId->append(buildid, sizeof(buildid));
+}
+
+static const JS::AsmJSCacheOps asmJSCacheOps = {
+    ShellOpenAsmJSCacheEntryForRead,
+    ShellCloseAsmJSCacheEntryForRead,
+    ShellOpenAsmJSCacheEntryForWrite,
+    ShellCloseAsmJSCacheEntryForWrite
+};
+
+static JSObject*
+NewGlobalObject(JSContext* cx, JS::CompartmentOptions& options,
+                JSPrincipals* principals)
+{
+    RootedObject glob(cx, JS_NewGlobalObject(cx, &global_class, principals,
+                                             JS::DontFireOnNewGlobalHook, options));
+    if (!glob)
+        return nullptr;
+
+    {
+        JSAutoCompartment ac(cx, glob);
+
+#ifndef LAZY_STANDARD_CLASSES
+        if (!JS_InitStandardClasses(cx, glob))
+            return nullptr;
+#endif
+
+        bool succeeded;
+        if (!JS_SetImmutablePrototype(cx, glob, &succeeded))
+            return nullptr;
+        MOZ_ASSERT(succeeded,
+                   "a fresh, unexposed global object is always capable of "
+                   "having its [[Prototype]] be immutable");
+
+#ifdef JS_HAS_CTYPES
+        if (!JS_InitCTypesClass(cx, glob))
+            return nullptr;
+#endif
+        if (!JS_InitReflectParse(cx, glob))
+            return nullptr;
+        if (!JS_DefineDebuggerObject(cx, glob))
+            return nullptr;
+        if (!JS::RegisterPerfMeasurement(cx, glob))
+            return nullptr;
+        if (!JS_DefineFunctionsWithHelp(cx, glob, shell_functions) ||
+            !JS_DefineProfilingFunctions(cx, glob))
+        {
+            return nullptr;
+        }
+        if (!js::DefineTestingFunctions(cx, glob, fuzzingSafe, disableOOMFunctions))
+            return nullptr;
+
+        if (!fuzzingSafe) {
+            if (!JS_DefineFunctionsWithHelp(cx, glob, fuzzing_unsafe_functions))
+                return nullptr;
+            if (!DefineConsole(cx, glob))
+                return nullptr;
+        }
+
+        if (!DefineOS(cx, glob, fuzzingSafe, &gOutFile, &gErrFile))
+            return nullptr;
+
+        RootedObject performanceObj(cx, JS_NewObject(cx, nullptr));
+        if (!performanceObj)
+            return nullptr;
+        RootedObject mozMemoryObj(cx, JS_NewObject(cx, nullptr));
+        if (!mozMemoryObj)
+            return nullptr;
+        RootedObject gcObj(cx, gc::NewMemoryInfoObject(cx));
+        if (!gcObj)
+            return nullptr;
+        if (!JS_DefineProperty(cx, glob, "performance", performanceObj, JSPROP_ENUMERATE))
+            return nullptr;
+        if (!JS_DefineProperty(cx, performanceObj, "mozMemory", mozMemoryObj, JSPROP_ENUMERATE))
+            return nullptr;
+        if (!JS_DefineProperty(cx, mozMemoryObj, "gc", gcObj, JSPROP_ENUMERATE))
+            return nullptr;
+
+        /* Initialize FakeDOMObject. */
+        static const js::DOMCallbacks DOMcallbacks = {
+            InstanceClassHasProtoAtDepth
+        };
+        SetDOMCallbacks(cx, &DOMcallbacks);
+
+        RootedObject domProto(cx, JS_InitClass(cx, glob, nullptr, &dom_class, dom_constructor,
+                                               0, dom_props, dom_methods, nullptr, nullptr));
+        if (!domProto)
+            return nullptr;
+
+        /* Initialize FakeDOMObject.prototype */
+        InitDOMObject(domProto);
+    }
+
+    JS_FireOnNewGlobalObject(cx, glob);
+
+    return glob;
+}
+
+static bool
+BindScriptArgs(JSContext* cx, OptionParser* op)
+{
+    AutoReportException are(cx);
+
+    MultiStringRange msr = op->getMultiStringArg("scriptArgs");
+    RootedObject scriptArgs(cx);
+    scriptArgs = JS_NewArrayObject(cx, 0);
+    if (!scriptArgs)
+        return false;
+
+    if (!JS_DefineProperty(cx, cx->global(), "scriptArgs", scriptArgs, 0))
+        return false;
+
+    for (size_t i = 0; !msr.empty(); msr.popFront(), ++i) {
+        const char* scriptArg = msr.front();
+        JS::RootedString str(cx, JS_NewStringCopyZ(cx, scriptArg));
+        if (!str ||
+            !JS_DefineElement(cx, scriptArgs, i, str, JSPROP_ENUMERATE))
+        {
+            return false;
+        }
+    }
+
+    const char* scriptPath = op->getStringArg("script");
+    RootedValue scriptPathValue(cx);
+    if (scriptPath) {
+        RootedString scriptPathString(cx, JS_NewStringCopyZ(cx, scriptPath));
+        if (!scriptPathString)
+            return false;
+        scriptPathValue = StringValue(scriptPathString);
+    } else {
+        scriptPathValue = UndefinedValue();
+    }
+
+    if (!JS_DefineProperty(cx, cx->global(), "scriptPath", scriptPathValue, 0))
+        return false;
+
+    return true;
+}
+
+static bool
+OptionFailure(const char* option, const char* str)
+{
+    fprintf(stderr, "Unrecognized option for %s: %s\n", option, str);
+    return false;
+}
+
+static MOZ_MUST_USE bool
+ProcessArgs(JSContext* cx, OptionParser* op)
+{
+    ShellContext* sc = GetShellContext(cx);
+
+    if (op->getBoolOption('s'))
+        JS::ContextOptionsRef(cx).toggleExtraWarnings();
+
+    /* |scriptArgs| gets bound on the global before any code is run. */
+    if (!BindScriptArgs(cx, op))
+        return false;
+
+    MultiStringRange filePaths = op->getMultiStringOption('f');
+    MultiStringRange codeChunks = op->getMultiStringOption('e');
+    MultiStringRange modulePaths = op->getMultiStringOption('m');
+
+    if (filePaths.empty() &&
+        codeChunks.empty() &&
+        modulePaths.empty() &&
+        !op->getStringArg("script"))
+    {
+        return Process(cx, nullptr, true); /* Interactive. */
+    }
+
+    if (const char* path = op->getStringOption("module-load-path"))
+        moduleLoadPath = path;
+
+    if (!modulePaths.empty() && !InitModuleLoader(cx))
+        return false;
+
+    while (!filePaths.empty() || !codeChunks.empty() || !modulePaths.empty()) {
+        size_t fpArgno = filePaths.empty() ? SIZE_MAX : filePaths.argno();
+        size_t ccArgno = codeChunks.empty() ? SIZE_MAX : codeChunks.argno();
+        size_t mpArgno = modulePaths.empty() ? SIZE_MAX : modulePaths.argno();
+
+        if (fpArgno < ccArgno && fpArgno < mpArgno) {
+            char* path = filePaths.front();
+            if (!Process(cx, path, false, FileScript))
+                return false;
+            filePaths.popFront();
+        } else if (ccArgno < fpArgno && ccArgno < mpArgno) {
+            const char* code = codeChunks.front();
+            RootedValue rval(cx);
+            JS::CompileOptions opts(cx);
+            opts.setFileAndLine("-e", 1);
+            if (!JS::Evaluate(cx, opts, code, strlen(code), &rval))
+                return false;
+            codeChunks.popFront();
+            if (sc->quitting)
+                break;
+        } else {
+            MOZ_ASSERT(mpArgno < fpArgno && mpArgno < ccArgno);
+            char* path = modulePaths.front();
+            if (!Process(cx, path, false, FileModule))
+                return false;
+            modulePaths.popFront();
+        }
+    }
+
+    if (sc->quitting)
+        return false;
+
+    /* The |script| argument is processed after all options. */
+    if (const char* path = op->getStringArg("script")) {
+        if (!Process(cx, path, false))
+            return false;
+    }
+
+    DrainJobQueue(cx);
+
+    if (op->getBoolOption('i')) {
+        if (!Process(cx, nullptr, true))
+            return false;
+    }
+
+    return true;
+}
+
+static bool
+SetContextOptions(JSContext* cx, const OptionParser& op)
+{
+    enableBaseline = !op.getBoolOption("no-baseline");
+    enableIon = !op.getBoolOption("no-ion");
+    enableAsmJS = !op.getBoolOption("no-asmjs");
+    enableWasm = !op.getBoolOption("no-wasm");
+    enableNativeRegExp = !op.getBoolOption("no-native-regexp");
+    enableUnboxedArrays = op.getBoolOption("unboxed-arrays");
+    enableWasmAlwaysBaseline = op.getBoolOption("wasm-always-baseline");
+
+    JS::ContextOptionsRef(cx).setBaseline(enableBaseline)
+                             .setIon(enableIon)
+                             .setAsmJS(enableAsmJS)
+                             .setWasm(enableWasm)
+                             .setWasmAlwaysBaseline(enableWasmAlwaysBaseline)
+                             .setNativeRegExp(enableNativeRegExp)
+                             .setUnboxedArrays(enableUnboxedArrays);
+
+    if (op.getBoolOption("wasm-check-bce"))
+        jit::JitOptions.wasmAlwaysCheckBounds = true;
+
+    if (op.getBoolOption("no-unboxed-objects"))
+        jit::JitOptions.disableUnboxedObjects = true;
+
+    if (const char* str = op.getStringOption("cache-ir-stubs")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableCacheIR = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableCacheIR = true;
+        else
+            return OptionFailure("cache-ir-stubs", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-scalar-replacement")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableScalarReplacement = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableScalarReplacement = true;
+        else
+            return OptionFailure("ion-scalar-replacement", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-shared-stubs")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableSharedStubs = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableSharedStubs = true;
+        else
+            return OptionFailure("ion-shared-stubs", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-gvn")) {
+        if (strcmp(str, "off") == 0) {
+            jit::JitOptions.disableGvn = true;
+        } else if (strcmp(str, "on") != 0 &&
+                   strcmp(str, "optimistic") != 0 &&
+                   strcmp(str, "pessimistic") != 0)
+        {
+            // We accept "pessimistic" and "optimistic" as synonyms for "on"
+            // for backwards compatibility.
+            return OptionFailure("ion-gvn", str);
+        }
+    }
+
+    if (const char* str = op.getStringOption("ion-aa")) {
+        if (strcmp(str, "flow-sensitive") == 0)
+            jit::JitOptions.disableFlowAA = false;
+        else if (strcmp(str, "flow-insensitive") == 0)
+            jit::JitOptions.disableFlowAA = true;
+        else
+            return OptionFailure("ion-aa", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-licm")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableLicm = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableLicm = true;
+        else
+            return OptionFailure("ion-licm", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-edgecase-analysis")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableEdgeCaseAnalysis = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableEdgeCaseAnalysis = true;
+        else
+            return OptionFailure("ion-edgecase-analysis", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-pgo")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disablePgo = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disablePgo = true;
+        else
+            return OptionFailure("ion-pgo", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-range-analysis")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableRangeAnalysis = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableRangeAnalysis = true;
+        else
+            return OptionFailure("ion-range-analysis", str);
+    }
+
+    if (const char *str = op.getStringOption("ion-sincos")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableSincos = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableSincos = true;
+        else
+            return OptionFailure("ion-sincos", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-sink")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableSink = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableSink = true;
+        else
+            return OptionFailure("ion-sink", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-loop-unrolling")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableLoopUnrolling = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableLoopUnrolling = true;
+        else
+            return OptionFailure("ion-loop-unrolling", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-instruction-reordering")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableInstructionReordering = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableInstructionReordering = true;
+        else
+            return OptionFailure("ion-instruction-reordering", str);
+    }
+
+    if (op.getBoolOption("ion-check-range-analysis"))
+        jit::JitOptions.checkRangeAnalysis = true;
+
+    if (op.getBoolOption("ion-extra-checks"))
+        jit::JitOptions.runExtraChecks = true;
+
+    if (const char* str = op.getStringOption("ion-inlining")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.disableInlining = false;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.disableInlining = true;
+        else
+            return OptionFailure("ion-inlining", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-osr")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.osr = true;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.osr = false;
+        else
+            return OptionFailure("ion-osr", str);
+    }
+
+    if (const char* str = op.getStringOption("ion-limit-script-size")) {
+        if (strcmp(str, "on") == 0)
+            jit::JitOptions.limitScriptSize = true;
+        else if (strcmp(str, "off") == 0)
+            jit::JitOptions.limitScriptSize = false;
+        else
+            return OptionFailure("ion-limit-script-size", str);
+    }
+
+    int32_t warmUpThreshold = op.getIntOption("ion-warmup-threshold");
+    if (warmUpThreshold >= 0)
+        jit::JitOptions.setCompilerWarmUpThreshold(warmUpThreshold);
+
+    warmUpThreshold = op.getIntOption("baseline-warmup-threshold");
+    if (warmUpThreshold >= 0)
+        jit::JitOptions.baselineWarmUpThreshold = warmUpThreshold;
+
+    if (op.getBoolOption("baseline-eager"))
+        jit::JitOptions.baselineWarmUpThreshold = 0;
+
+    if (const char* str = op.getStringOption("ion-regalloc")) {
+        jit::JitOptions.forcedRegisterAllocator = jit::LookupRegisterAllocator(str);
+        if (!jit::JitOptions.forcedRegisterAllocator.isSome())
+            return OptionFailure("ion-regalloc", str);
+    }
+
+    if (op.getBoolOption("ion-eager"))
+        jit::JitOptions.setEagerCompilation();
+
+    offthreadCompilation = true;
+    if (const char* str = op.getStringOption("ion-offthread-compile")) {
+        if (strcmp(str, "off") == 0)
+            offthreadCompilation = false;
+        else if (strcmp(str, "on") != 0)
+            return OptionFailure("ion-offthread-compile", str);
+    }
+    cx->setOffthreadIonCompilationEnabled(offthreadCompilation);
+
+    if (op.getStringOption("ion-parallel-compile")) {
+        fprintf(stderr, "--ion-parallel-compile is deprecated. Please use --ion-offthread-compile instead.\n");
+        return false;
+    }
+
+#ifdef ENABLE_SHARED_ARRAY_BUFFER
+    if (const char* str = op.getStringOption("shared-memory")) {
+        if (strcmp(str, "off") == 0)
+            enableSharedMemory = false;
+        else if (strcmp(str, "on") == 0)
+            enableSharedMemory = true;
+        else
+            return OptionFailure("shared-memory", str);
+    }
+#endif
+
+#if defined(JS_CODEGEN_ARM)
+    if (const char* str = op.getStringOption("arm-hwcap"))
+        jit::ParseARMHwCapFlags(str);
+
+    int32_t fill = op.getIntOption("arm-asm-nop-fill");
+    if (fill >= 0)
+        jit::Assembler::NopFill = fill;
+
+    int32_t poolMaxOffset = op.getIntOption("asm-pool-max-offset");
+    if (poolMaxOffset >= 5 && poolMaxOffset <= 1024)
+        jit::Assembler::AsmPoolMaxOffset = poolMaxOffset;
+#endif
+
+#if defined(JS_SIMULATOR_ARM)
+    if (op.getBoolOption("arm-sim-icache-checks"))
+        jit::Simulator::ICacheCheckingEnabled = true;
+
+    int32_t stopAt = op.getIntOption("arm-sim-stop-at");
+    if (stopAt >= 0)
+        jit::Simulator::StopSimAt = stopAt;
+#elif defined(JS_SIMULATOR_MIPS32) || defined(JS_SIMULATOR_MIPS64)
+    if (op.getBoolOption("mips-sim-icache-checks"))
+        jit::Simulator::ICacheCheckingEnabled = true;
+
+    int32_t stopAt = op.getIntOption("mips-sim-stop-at");
+    if (stopAt >= 0)
+        jit::Simulator::StopSimAt = stopAt;
+#endif
+
+    reportWarnings = op.getBoolOption('w');
+    compileOnly = op.getBoolOption('c');
+    printTiming = op.getBoolOption('b');
+    enableCodeCoverage = op.getBoolOption("code-coverage");
+    enableDisassemblyDumps = op.getBoolOption('D');
+    cx->profilingScripts = enableCodeCoverage || enableDisassemblyDumps;
+
+    jsCacheDir = op.getStringOption("js-cache");
+    if (jsCacheDir) {
+        if (!op.getBoolOption("no-js-cache-per-process"))
+            jsCacheDir = JS_smprintf("%s/%u", jsCacheDir, (unsigned)getpid());
+        else
+            jsCacheDir = JS_strdup(cx, jsCacheDir);
+        if (!jsCacheDir)
+            return false;
+        jsCacheAsmJSPath = JS_smprintf("%s/asmjs.cache", jsCacheDir);
+    }
+
+#ifdef DEBUG
+    dumpEntrainedVariables = op.getBoolOption("dump-entrained-variables");
+#endif
+
+#ifdef JS_GC_ZEAL
+    const char* zealStr = op.getStringOption("gc-zeal");
+    if (zealStr) {
+        if (!cx->gc.parseAndSetZeal(zealStr))
+            return false;
+        uint32_t nextScheduled;
+        cx->gc.getZealBits(&gZealBits, &gZealFrequency, &nextScheduled);
+    }
+#endif
+
+    return true;
+}
+
+static void
+SetWorkerContextOptions(JSContext* cx)
+{
+    // Copy option values from the main thread.
+    JS::ContextOptionsRef(cx).setBaseline(enableBaseline)
+                             .setIon(enableIon)
+                             .setAsmJS(enableAsmJS)
+                             .setWasm(enableWasm)
+                             .setWasmAlwaysBaseline(enableWasmAlwaysBaseline)
+                             .setNativeRegExp(enableNativeRegExp)
+                             .setUnboxedArrays(enableUnboxedArrays);
+    cx->setOffthreadIonCompilationEnabled(offthreadCompilation);
+    cx->profilingScripts = enableCodeCoverage || enableDisassemblyDumps;
+
+#ifdef JS_GC_ZEAL
+    if (gZealBits && gZealFrequency) {
+#define ZEAL_MODE(_, value)                        \
+        if (gZealBits & (1 << value))              \
+            cx->gc.setZeal(value, gZealFrequency);
+        JS_FOR_EACH_ZEAL_MODE(ZEAL_MODE)
+#undef ZEAL_MODE
+    }
+#endif
+
+    JS_SetNativeStackQuota(cx, gMaxStackSize);
+}
+
+static int
+Shell(JSContext* cx, OptionParser* op, char** envp)
+{
+    Maybe<JS::AutoDisableGenerationalGC> noggc;
+    if (op->getBoolOption("no-ggc"))
+        noggc.emplace(cx->runtime());
+
+    Maybe<AutoDisableCompactingGC> nocgc;
+    if (op->getBoolOption("no-cgc"))
+        nocgc.emplace(cx);
+
+    JSAutoRequest ar(cx);
+
+    if (op->getBoolOption("fuzzing-safe"))
+        fuzzingSafe = true;
+    else
+        fuzzingSafe = (getenv("MOZ_FUZZING_SAFE") && getenv("MOZ_FUZZING_SAFE")[0] != '0');
+
+    if (op->getBoolOption("disable-oom-functions"))
+        disableOOMFunctions = true;
+
+    JS::CompartmentOptions options;
+    SetStandardCompartmentOptions(options);
+    RootedObject glob(cx, NewGlobalObject(cx, options, nullptr));
+    if (!glob)
+        return 1;
+
+    JSAutoCompartment ac(cx, glob);
+
+    ShellContext* sc = GetShellContext(cx);
+    int result = EXIT_SUCCESS;
+    {
+        AutoReportException are(cx);
+        if (!ProcessArgs(cx, op) && !sc->quitting)
+            result = EXITCODE_RUNTIME_ERROR;
+    }
+
+    if (sc->exitCode)
+        result = sc->exitCode;
+
+    if (enableDisassemblyDumps) {
+        AutoReportException are(cx);
+        if (!js::DumpCompartmentPCCounts(cx))
+            result = EXITCODE_OUT_OF_MEMORY;
+    }
+
+    if (!op->getBoolOption("no-js-cache-per-process")) {
+        if (jsCacheAsmJSPath) {
+            unlink(jsCacheAsmJSPath);
+            JS_free(cx, const_cast<char*>(jsCacheAsmJSPath));
+        }
+        if (jsCacheDir) {
+            rmdir(jsCacheDir);
+            JS_free(cx, const_cast<char*>(jsCacheDir));
+        }
+    }
+
+    return result;
+}
+
+static void
+SetOutputFile(const char* const envVar,
+              RCFile* defaultOut,
+              RCFile** outFileP)
+{
+    RCFile* outFile;
+
+    const char* outPath = getenv(envVar);
+    FILE* newfp;
+    if (outPath && *outPath && (newfp = fopen(outPath, "w")))
+        outFile = js_new<RCFile>(newfp);
+    else
+        outFile = defaultOut;
+
+    outFile->acquire();
+    *outFileP = outFile;
+}
+
+static void
+PreInit()
+{
+#ifdef XP_WIN
+    const char* crash_option = getenv("XRE_NO_WINDOWS_CRASH_DIALOG");
+    if (crash_option && crash_option[0] == '1') {
+        // Disable the segfault dialog. We want to fail the tests immediately
+        // instead of hanging automation.
+        UINT newMode = SEM_NOGPFAULTERRORBOX | SEM_NOOPENFILEERRORBOX;
+        UINT prevMode = SetErrorMode(newMode);
+        SetErrorMode(prevMode | newMode);
+    }
+#endif
+}
+
+int
+main(int argc, char** argv, char** envp)
+{
+    PreInit();
+
+    sArgc = argc;
+    sArgv = argv;
+
+    int result;
+
+#ifdef HAVE_SETLOCALE
+    setlocale(LC_ALL, "");
+#endif
+
+    // Special-case stdout and stderr. We bump their refcounts to prevent them
+    // from getting closed and then having some printf fail somewhere.
+    RCFile rcStdout(stdout);
+    rcStdout.acquire();
+    RCFile rcStderr(stderr);
+    rcStderr.acquire();
+
+    SetOutputFile("JS_STDOUT", &rcStdout, &gOutFile);
+    SetOutputFile("JS_STDERR", &rcStderr, &gErrFile);
+
+    OptionParser op("Usage: {progname} [options] [[script] scriptArgs*]");
+
+    op.setDescription("The SpiderMonkey shell provides a command line interface to the "
+        "JavaScript engine. Code and file options provided via the command line are "
+        "run left to right. If provided, the optional script argument is run after "
+        "all options have been processed. Just-In-Time compilation modes may be enabled via "
+        "command line options.");
+    op.setDescriptionWidth(72);
+    op.setHelpWidth(80);
+    op.setVersion(JS_GetImplementationVersion());
+
+    if (!op.addMultiStringOption('f', "file", "PATH", "File path to run")
+        || !op.addMultiStringOption('m', "module", "PATH", "Module path to run")
+        || !op.addMultiStringOption('e', "execute", "CODE", "Inline code to run")
+        || !op.addBoolOption('i', "shell", "Enter prompt after running code")
+        || !op.addBoolOption('c', "compileonly", "Only compile, don't run (syntax checking mode)")
+        || !op.addBoolOption('w', "warnings", "Emit warnings")
+        || !op.addBoolOption('W', "nowarnings", "Don't emit warnings")
+        || !op.addBoolOption('s', "strict", "Check strictness")
+        || !op.addBoolOption('D', "dump-bytecode", "Dump bytecode with exec count for all scripts")
+        || !op.addBoolOption('b', "print-timing", "Print sub-ms runtime for each file that's run")
+        || !op.addStringOption('\0', "js-cache", "[path]",
+                               "Enable the JS cache by specifying the path of the directory to use "
+                               "to hold cache files")
+        || !op.addBoolOption('\0', "no-js-cache-per-process",
+                               "Deactivates cache per process. Otherwise, generate a separate cache"
+                               "sub-directory for this process inside the cache directory"
+                               "specified by --js-cache. This cache directory will be removed"
+                               "when the js shell exits. This is useful for running tests in"
+                               "parallel.")
+        || !op.addBoolOption('\0', "code-coverage", "Enable code coverage instrumentation.")
+#ifdef DEBUG
+        || !op.addBoolOption('O', "print-alloc", "Print the number of allocations at exit")
+#endif
+        || !op.addOptionalStringArg("script", "A script to execute (after all options)")
+        || !op.addOptionalMultiStringArg("scriptArgs",
+                                         "String arguments to bind as |scriptArgs| in the "
+                                         "shell's global")
+        || !op.addIntOption('\0', "thread-count", "COUNT", "Use COUNT auxiliary threads "
+                            "(default: # of cores - 1)", -1)
+        || !op.addBoolOption('\0', "ion", "Enable IonMonkey (default)")
+        || !op.addBoolOption('\0', "no-ion", "Disable IonMonkey")
+        || !op.addBoolOption('\0', "no-asmjs", "Disable asm.js compilation")
+        || !op.addBoolOption('\0', "no-wasm", "Disable WebAssembly compilation")
+        || !op.addBoolOption('\0', "no-native-regexp", "Disable native regexp compilation")
+        || !op.addBoolOption('\0', "no-unboxed-objects", "Disable creating unboxed plain objects")
+        || !op.addBoolOption('\0', "unboxed-arrays", "Allow creating unboxed arrays")
+        || !op.addBoolOption('\0', "wasm-always-baseline", "Enable wasm baseline compiler when possible")
+        || !op.addBoolOption('\0', "wasm-check-bce", "Always generate wasm bounds check, even redundant ones.")
+#ifdef ENABLE_SHARED_ARRAY_BUFFER
+        || !op.addStringOption('\0', "shared-memory", "on/off",
+                               "SharedArrayBuffer and Atomics "
+#  if SHARED_MEMORY_DEFAULT
+                               "(default: on, off to disable)"
+#  else
+                               "(default: off, on to enable)"
+#  endif
+            )
+#endif
+        || !op.addStringOption('\0', "cache-ir-stubs", "on/off",
+                               "Use CacheIR stubs (default: on, off to disable)")
+        || !op.addStringOption('\0', "ion-shared-stubs", "on/off",
+                               "Use shared stubs (default: on, off to disable)")
+        || !op.addStringOption('\0', "ion-scalar-replacement", "on/off",
+                               "Scalar Replacement (default: on, off to disable)")
+        || !op.addStringOption('\0', "ion-gvn", "[mode]",
+                               "Specify Ion global value numbering:\n"
+                               "  off: disable GVN\n"
+                               "  on:  enable GVN (default)\n")
+        || !op.addStringOption('\0', "ion-licm", "on/off",
+                               "Loop invariant code motion (default: on, off to disable)")
+        || !op.addStringOption('\0', "ion-aa", "flow-sensitive/flow-insensitive",
+                               "Specify wheter or not to use flow sensitive Alias Analysis"
+                               "(default: flow-insensitive)")
+        || !op.addStringOption('\0', "ion-edgecase-analysis", "on/off",
+                               "Find edge cases where Ion can avoid bailouts (default: on, off to disable)")
+        || !op.addStringOption('\0', "ion-pgo", "on/off",
+                               "Profile guided optimization (default: on, off to disable)")
+        || !op.addStringOption('\0', "ion-range-analysis", "on/off",
+                               "Range analysis (default: on, off to disable)")
+#if defined(__APPLE__)
+        || !op.addStringOption('\0', "ion-sincos", "on/off",
+                               "Replace sin(x)/cos(x) to sincos(x) (default: on, off to disable)")
+#else
+        || !op.addStringOption('\0', "ion-sincos", "on/off",
+                               "Replace sin(x)/cos(x) to sincos(x) (default: off, on to enable)")
+#endif
+        || !op.addStringOption('\0', "ion-sink", "on/off",
+                               "Sink code motion (default: off, on to enable)")
+        || !op.addStringOption('\0', "ion-loop-unrolling", "on/off",
+                               "Loop unrolling (default: off, on to enable)")
+        || !op.addStringOption('\0', "ion-instruction-reordering", "on/off",
+                               "Instruction reordering (default: off, on to enable)")
+        || !op.addBoolOption('\0', "ion-check-range-analysis",
+                               "Range analysis checking")
+        || !op.addBoolOption('\0', "ion-extra-checks",
+                               "Perform extra dynamic validation checks")
+        || !op.addStringOption('\0', "ion-inlining", "on/off",
+                               "Inline methods where possible (default: on, off to disable)")
+        || !op.addStringOption('\0', "ion-osr", "on/off",
+                               "On-Stack Replacement (default: on, off to disable)")
+        || !op.addStringOption('\0', "ion-limit-script-size", "on/off",
+                               "Don't compile very large scripts (default: on, off to disable)")
+        || !op.addIntOption('\0', "ion-warmup-threshold", "COUNT",
+                            "Wait for COUNT calls or iterations before compiling "
+                            "(default: 1000)", -1)
+        || !op.addStringOption('\0', "ion-regalloc", "[mode]",
+                               "Specify Ion register allocation:\n"
+                               "  backtracking: Priority based backtracking register allocation (default)\n"
+                               "  testbed: Backtracking allocator with experimental features\n"
+                               "  stupid: Simple block local register allocation")
+        || !op.addBoolOption('\0', "ion-eager", "Always ion-compile methods (implies --baseline-eager)")
+        || !op.addStringOption('\0', "ion-offthread-compile", "on/off",
+                               "Compile scripts off thread (default: on)")
+        || !op.addStringOption('\0', "ion-parallel-compile", "on/off",
+                               "--ion-parallel compile is deprecated. Use --ion-offthread-compile.")
+        || !op.addBoolOption('\0', "baseline", "Enable baseline compiler (default)")
+        || !op.addBoolOption('\0', "no-baseline", "Disable baseline compiler")
+        || !op.addBoolOption('\0', "baseline-eager", "Always baseline-compile methods")
+        || !op.addIntOption('\0', "baseline-warmup-threshold", "COUNT",
+                            "Wait for COUNT calls or iterations before baseline-compiling "
+                            "(default: 10)", -1)
+        || !op.addBoolOption('\0', "non-writable-jitcode", "(NOP for fuzzers) Allocate JIT code as non-writable memory.")
+        || !op.addBoolOption('\0', "no-sse3", "Pretend CPU does not support SSE3 instructions and above "
+                             "to test JIT codegen (no-op on platforms other than x86 and x64).")
+        || !op.addBoolOption('\0', "no-sse4", "Pretend CPU does not support SSE4 instructions"
+                             "to test JIT codegen (no-op on platforms other than x86 and x64).")
+        || !op.addBoolOption('\0', "enable-avx", "AVX is disabled by default. Enable AVX. "
+                             "(no-op on platforms other than x86 and x64).")
+        || !op.addBoolOption('\0', "no-avx", "No-op. AVX is currently disabled by default.")
+        || !op.addBoolOption('\0', "fuzzing-safe", "Don't expose functions that aren't safe for "
+                             "fuzzers to call")
+        || !op.addBoolOption('\0', "disable-oom-functions", "Disable functions that cause "
+                            "artificial OOMs")
+        || !op.addBoolOption('\0', "no-threads", "Disable helper threads")
+#ifdef DEBUG
+        || !op.addBoolOption('\0', "dump-entrained-variables", "Print variables which are "
+                             "unnecessarily entrained by inner functions")
+#endif
+        || !op.addBoolOption('\0', "no-ggc", "Disable Generational GC")
+        || !op.addBoolOption('\0', "no-cgc", "Disable Compacting GC")
+        || !op.addBoolOption('\0', "no-incremental-gc", "Disable Incremental GC")
+        || !op.addIntOption('\0', "available-memory", "SIZE",
+                            "Select GC settings based on available memory (MB)", 0)
+#if defined(JS_CODEGEN_ARM)
+        || !op.addStringOption('\0', "arm-hwcap", "[features]",
+                               "Specify ARM code generation features, or 'help' to list all features.")
+        || !op.addIntOption('\0', "arm-asm-nop-fill", "SIZE",
+                            "Insert the given number of NOP instructions at all possible pool locations.", 0)
+        || !op.addIntOption('\0', "asm-pool-max-offset", "OFFSET",
+                            "The maximum pc relative OFFSET permitted in pool reference instructions.", 1024)
+#endif
+#if defined(JS_SIMULATOR_ARM)
+        || !op.addBoolOption('\0', "arm-sim-icache-checks", "Enable icache flush checks in the ARM "
+                             "simulator.")
+        || !op.addIntOption('\0', "arm-sim-stop-at", "NUMBER", "Stop the ARM simulator after the given "
+                            "NUMBER of instructions.", -1)
+#elif defined(JS_SIMULATOR_MIPS32) || defined(JS_SIMULATOR_MIPS64)
+	|| !op.addBoolOption('\0', "mips-sim-icache-checks", "Enable icache flush checks in the MIPS "
+                             "simulator.")
+        || !op.addIntOption('\0', "mips-sim-stop-at", "NUMBER", "Stop the MIPS simulator after the given "
+                            "NUMBER of instructions.", -1)
+#endif
+        || !op.addIntOption('\0', "nursery-size", "SIZE-MB", "Set the maximum nursery size in MB", 16)
+#ifdef JS_GC_ZEAL
+        || !op.addStringOption('z', "gc-zeal", "LEVEL(;LEVEL)*[,N]", gc::ZealModeHelpText)
+#endif
+        || !op.addStringOption('\0', "module-load-path", "DIR", "Set directory to load modules from")
+    )
+    {
+        return EXIT_FAILURE;
+    }
+
+    op.setArgTerminatesOptions("script", true);
+    op.setArgCapturesRest("scriptArgs");
+
+    switch (op.parseArgs(argc, argv)) {
+      case OptionParser::EarlyExit:
+        return EXIT_SUCCESS;
+      case OptionParser::ParseError:
+        op.printHelp(argv[0]);
+        return EXIT_FAILURE;
+      case OptionParser::Fail:
+        return EXIT_FAILURE;
+      case OptionParser::Okay:
+        break;
+    }
+
+    if (op.getHelpOption())
+        return EXIT_SUCCESS;
+
+#ifdef DEBUG
+    /*
+     * Process OOM options as early as possible so that we can observe as many
+     * allocations as possible.
+     */
+    OOM_printAllocationCount = op.getBoolOption('O');
+#endif
+
+#if defined(JS_CODEGEN_X86) || defined(JS_CODEGEN_X64)
+    if (op.getBoolOption("no-sse3")) {
+        js::jit::CPUInfo::SetSSE3Disabled();
+        PropagateFlagToNestedShells("--no-sse3");
+    }
+    if (op.getBoolOption("no-sse4")) {
+        js::jit::CPUInfo::SetSSE4Disabled();
+        PropagateFlagToNestedShells("--no-sse4");
+    }
+    if (op.getBoolOption("enable-avx")) {
+        js::jit::CPUInfo::SetAVXEnabled();
+        PropagateFlagToNestedShells("--enable-avx");
+    }
+#endif
+
+    if (op.getBoolOption("no-threads"))
+        js::DisableExtraThreads();
+
+    // Start the engine.
+    if (!JS_Init())
+        return 1;
+
+    if (!InitSharedArrayBufferMailbox())
+        return 1;
+
+    // The fake thread count must be set before initializing the Runtime,
+    // which spins up the thread pool.
+    int32_t threadCount = op.getIntOption("thread-count");
+    if (threadCount >= 0)
+        SetFakeCPUCount(threadCount);
+
+    size_t nurseryBytes = JS::DefaultNurseryBytes;
+    nurseryBytes = op.getIntOption("nursery-size") * 1024L * 1024L;
+
+    /* Use the same parameters as the browser in xpcjsruntime.cpp. */
+    JSContext* cx = JS_NewContext(JS::DefaultHeapMaxBytes, nurseryBytes);
+    if (!cx)
+        return 1;
+
+    UniquePtr<ShellContext> sc = MakeUnique<ShellContext>(cx);
+    if (!sc)
+        return 1;
+
+    JS_SetContextPrivate(cx, sc.get());
+    // Waiting is allowed on the shell's main thread, for now.
+    JS_SetFutexCanWait(cx);
+    JS::SetWarningReporter(cx, WarningReporter);
+    if (!SetContextOptions(cx, op))
+        return 1;
+
+    JS_SetGCParameter(cx, JSGC_MAX_BYTES, 0xffffffff);
+
+    size_t availMem = op.getIntOption("available-memory");
+    if (availMem > 0)
+        JS_SetGCParametersBasedOnAvailableMemory(cx, availMem);
+
+    JS_SetTrustedPrincipals(cx, &ShellPrincipals::fullyTrusted);
+    JS_SetSecurityCallbacks(cx, &ShellPrincipals::securityCallbacks);
+    JS_InitDestroyPrincipalsCallback(cx, ShellPrincipals::destroy);
+
+    JS_AddInterruptCallback(cx, ShellInterruptCallback);
+    JS::SetBuildIdOp(cx, ShellBuildId);
+    JS::SetAsmJSCacheOps(cx, &asmJSCacheOps);
+
+    JS_SetNativeStackQuota(cx, gMaxStackSize);
+
+    JS::dbg::SetDebuggerMallocSizeOf(cx, moz_malloc_size_of);
+
+    if (!JS::InitSelfHostedCode(cx))
+        return 1;
+
+#ifdef SPIDERMONKEY_PROMISE
+    sc->jobQueue.init(cx, JobQueue(SystemAllocPolicy()));
+    JS::SetEnqueuePromiseJobCallback(cx, ShellEnqueuePromiseJobCallback);
+    JS::SetGetIncumbentGlobalCallback(cx, ShellGetIncumbentGlobalCallback);
+    JS::SetAsyncTaskCallbacks(cx, ShellStartAsyncTaskCallback, ShellFinishAsyncTaskCallback);
+#endif // SPIDERMONKEY_PROMISE
+
+    EnvironmentPreparer environmentPreparer(cx);
+
+    JS_SetGCParameter(cx, JSGC_MODE, JSGC_MODE_INCREMENTAL);
+
+    JS::SetLargeAllocationFailureCallback(cx, my_LargeAllocFailCallback, (void*)cx);
+
+    // Set some parameters to allow incremental GC in low memory conditions,
+    // as is done for the browser, except in more-deterministic builds or when
+    // disabled by command line options.
+#ifndef JS_MORE_DETERMINISTIC
+    if (!op.getBoolOption("no-incremental-gc")) {
+        JS_SetGCParameter(cx, JSGC_DYNAMIC_HEAP_GROWTH, 1);
+        JS_SetGCParameter(cx, JSGC_DYNAMIC_MARK_SLICE, 1);
+        JS_SetGCParameter(cx, JSGC_SLICE_TIME_BUDGET, 10);
+    }
+#endif
+
+    js::SetPreserveWrapperCallback(cx, DummyPreserveWrapperCallback);
+
+    result = Shell(cx, &op, envp);
+
+#ifdef DEBUG
+    if (OOM_printAllocationCount)
+        printf("OOM max count: %" PRIu64 "\n", js::oom::counter);
+#endif
+
+    JS::SetLargeAllocationFailureCallback(cx, nullptr, nullptr);
+
+#ifdef SPIDERMONKEY_PROMISE
+    JS::SetGetIncumbentGlobalCallback(cx, nullptr);
+    JS::SetEnqueuePromiseJobCallback(cx, nullptr);
+    sc->jobQueue.reset();
+#endif // SPIDERMONKEY_PROMISE
+
+    KillWatchdog(cx);
+
+    KillWorkerThreads();
+
+    DestructSharedArrayBufferMailbox();
+
+    JS_DestroyContext(cx);
+    JS_ShutDown();
+    return result;
+}
diff --git a/js/src/shell/jsoptparse.cpp b/js/src/shell/jsoptparse.cpp
new file mode 100644
index 0000000000..eaf4042d3b
--- /dev/null
+++ b/js/src/shell/jsoptparse.cpp
@@ -0,0 +1,644 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "shell/jsoptparse.h"
+
+#include <ctype.h>
+#include <stdarg.h>
+
+#include "jsutil.h"
+
+using namespace js;
+using namespace js::cli;
+using namespace js::cli::detail;
+
+const char OptionParser::prognameMeta[] = "{progname}";
+
+#define OPTION_CONVERT_IMPL(__cls) \
+    bool \
+    Option::is##__cls##Option() const \
+    { \
+        return kind == OptionKind##__cls; \
+    } \
+    __cls##Option * \
+    Option::as##__cls##Option() \
+    { \
+        MOZ_ASSERT(is##__cls##Option()); \
+        return static_cast<__cls##Option*>(this); \
+    } \
+    const __cls##Option * \
+    Option::as##__cls##Option() const \
+    { \
+        return const_cast<Option*>(this)->as##__cls##Option(); \
+    }
+
+ValuedOption*
+Option::asValued()
+{
+    MOZ_ASSERT(isValued());
+    return static_cast<ValuedOption*>(this);
+}
+
+const ValuedOption*
+Option::asValued() const
+{
+    return const_cast<Option*>(this)->asValued();
+}
+
+OPTION_CONVERT_IMPL(Bool)
+OPTION_CONVERT_IMPL(String)
+OPTION_CONVERT_IMPL(Int)
+OPTION_CONVERT_IMPL(MultiString)
+
+void
+OptionParser::setArgTerminatesOptions(const char* name, bool enabled)
+{
+    findArgument(name)->setTerminatesOptions(enabled);
+}
+
+void
+OptionParser::setArgCapturesRest(const char* name)
+{
+    MOZ_ASSERT(restArgument == -1, "only one argument may be set to capture the rest");
+    restArgument = findArgumentIndex(name);
+    MOZ_ASSERT(restArgument != -1, "unknown argument name passed to setArgCapturesRest");
+}
+
+OptionParser::Result
+OptionParser::error(const char* fmt, ...)
+{
+    va_list args;
+    va_start(args, fmt);
+    fprintf(stderr, "Error: ");
+    vfprintf(stderr, fmt, args);
+    va_end(args);
+    fputs("\n\n", stderr);
+    return ParseError;
+}
+
+/* Quick and dirty paragraph printer. */
+static void
+PrintParagraph(const char* text, unsigned startColno, const unsigned limitColno, bool padFirstLine)
+{
+    unsigned colno = startColno;
+    unsigned indent = 0;
+    const char* it = text;
+
+    if (padFirstLine)
+        printf("%*s", startColno, "");
+
+    /* Skip any leading spaces. */
+    while (*it != '\0' && isspace(*it))
+        ++it;
+
+    while (*it != '\0') {
+        MOZ_ASSERT(!isspace(*it) || *it == '\n');
+
+        /* Delimit the current token. */
+        const char* limit = it;
+        while (!isspace(*limit) && *limit != '\0')
+            ++limit;
+
+        /*
+         * If the current token is longer than the available number of columns,
+         * then make a line break before printing the token.
+         */
+        size_t tokLen = limit - it;
+        if (tokLen + colno >= limitColno) {
+            printf("\n%*s%.*s", startColno + indent, "", int(tokLen), it);
+            colno = startColno + tokLen;
+        } else {
+            printf("%.*s", int(tokLen), it);
+            colno += tokLen;
+        }
+
+        switch (*limit) {
+          case '\0':
+            return;
+          case ' ':
+            putchar(' ');
+            colno += 1;
+            it = limit;
+            while (*it == ' ')
+                ++it;
+            break;
+          case '\n':
+            /* |text| wants to force a newline here. */
+            printf("\n%*s", startColno, "");
+            colno = startColno;
+            it = limit + 1;
+            /* Could also have line-leading spaces. */
+            indent = 0;
+            while (*it == ' ') {
+                putchar(' ');
+                ++colno;
+                ++indent;
+                ++it;
+            }
+            break;
+          default:
+            MOZ_CRASH("unhandled token splitting character in text");
+        }
+    }
+}
+
+static const char*
+OptionFlagsToFormatInfo(char shortflag, bool isValued, size_t* length)
+{
+    static const char * const fmt[4] = { "  -%c --%s ",
+                                         "  --%s ",
+                                         "  -%c --%s=%s ",
+                                         "  --%s=%s " };
+
+    /* How mny chars w/o longflag? */
+    size_t lengths[4] = { strlen(fmt[0]) - 3,
+                          strlen(fmt[1]) - 3,
+                          strlen(fmt[2]) - 5,
+                          strlen(fmt[3]) - 5 };
+    int index = isValued ? 2 : 0;
+    if (!shortflag)
+        index++;
+
+    *length = lengths[index];
+    return fmt[index];
+}
+
+OptionParser::Result
+OptionParser::printHelp(const char* progname)
+{
+    const char* prefixEnd = strstr(usage, prognameMeta);
+    if (prefixEnd) {
+        printf("%.*s%s%s\n", int(prefixEnd - usage), usage, progname,
+               prefixEnd + sizeof(prognameMeta) - 1);
+    } else {
+        puts(usage);
+    }
+
+    if (descr) {
+        putchar('\n');
+        PrintParagraph(descr, 2, descrWidth, true);
+        putchar('\n');
+    }
+
+    if (version)
+        printf("\nVersion: %s\n\n", version);
+
+    if (!arguments.empty()) {
+        printf("Arguments:\n");
+
+        static const char fmt[] = "  %s ";
+        size_t fmtChars = sizeof(fmt) - 2;
+        size_t lhsLen = 0;
+        for (Option* arg : arguments)
+            lhsLen = Max(lhsLen, strlen(arg->longflag) + fmtChars);
+
+        for (Option* arg : arguments) {
+            size_t chars = printf(fmt, arg->longflag);
+            for (; chars < lhsLen; ++chars)
+                putchar(' ');
+            PrintParagraph(arg->help, lhsLen, helpWidth, false);
+            putchar('\n');
+        }
+        putchar('\n');
+    }
+
+    if (!options.empty()) {
+        printf("Options:\n");
+
+        /* Calculate sizes for column alignment. */
+        size_t lhsLen = 0;
+        for (Option* opt : options) {
+            size_t longflagLen = strlen(opt->longflag);
+
+            size_t fmtLen;
+            OptionFlagsToFormatInfo(opt->shortflag, opt->isValued(), &fmtLen);
+
+            size_t len = fmtLen + longflagLen;
+            if (opt->isValued())
+                len += strlen(opt->asValued()->metavar);
+            lhsLen = Max(lhsLen, len);
+        }
+
+        /* Print option help text. */
+        for (Option* opt : options) {
+            size_t fmtLen;
+            const char* fmt = OptionFlagsToFormatInfo(opt->shortflag, opt->isValued(), &fmtLen);
+            size_t chars;
+            if (opt->isValued()) {
+                if (opt->shortflag)
+                    chars = printf(fmt, opt->shortflag, opt->longflag, opt->asValued()->metavar);
+                else
+                    chars = printf(fmt, opt->longflag, opt->asValued()->metavar);
+            } else {
+                if (opt->shortflag)
+                    chars = printf(fmt, opt->shortflag, opt->longflag);
+                else
+                    chars = printf(fmt, opt->longflag);
+            }
+            for (; chars < lhsLen; ++chars)
+                putchar(' ');
+            PrintParagraph(opt->help, lhsLen, helpWidth, false);
+            putchar('\n');
+        }
+    }
+
+    return EarlyExit;
+}
+
+OptionParser::Result
+OptionParser::printVersion()
+{
+    MOZ_ASSERT(version);
+    printf("%s\n", version);
+    return EarlyExit;
+}
+
+OptionParser::Result
+OptionParser::extractValue(size_t argc, char** argv, size_t* i, char** value)
+{
+    MOZ_ASSERT(*i < argc);
+    char* eq = strchr(argv[*i], '=');
+    if (eq) {
+        *value = eq + 1;
+        if (*value[0] == '\0')
+            return error("A value is required for option %.*s", (int) (eq - argv[*i]), argv[*i]);
+        return Okay;
+    }
+
+    if (argc == *i + 1)
+        return error("Expected a value for option %s", argv[*i]);
+
+    *i += 1;
+    *value = argv[*i];
+    return Okay;
+}
+
+OptionParser::Result
+OptionParser::handleOption(Option* opt, size_t argc, char** argv, size_t* i, bool* optionsAllowed)
+{
+    if (opt->getTerminatesOptions())
+        *optionsAllowed = false;
+
+    switch (opt->kind) {
+      case OptionKindBool:
+      {
+        if (opt == &helpOption)
+            return printHelp(argv[0]);
+        if (opt == &versionOption)
+            return printVersion();
+        opt->asBoolOption()->value = true;
+        return Okay;
+      }
+      /*
+       * Valued options are allowed to specify their values either via
+       * successive arguments or a single --longflag=value argument.
+       */
+      case OptionKindString:
+      {
+        char* value = nullptr;
+        if (Result r = extractValue(argc, argv, i, &value))
+            return r;
+        opt->asStringOption()->value = value;
+        return Okay;
+      }
+      case OptionKindInt:
+      {
+        char* value = nullptr;
+        if (Result r = extractValue(argc, argv, i, &value))
+            return r;
+        opt->asIntOption()->value = atoi(value);
+        return Okay;
+      }
+      case OptionKindMultiString:
+      {
+        char* value = nullptr;
+        if (Result r = extractValue(argc, argv, i, &value))
+            return r;
+        StringArg arg(value, *i);
+        return opt->asMultiStringOption()->strings.append(arg) ? Okay : Fail;
+      }
+      default:
+        MOZ_CRASH("unhandled option kind");
+    }
+}
+
+OptionParser::Result
+OptionParser::handleArg(size_t argc, char** argv, size_t* i, bool* optionsAllowed)
+{
+    if (nextArgument >= arguments.length())
+        return error("Too many arguments provided");
+
+    Option* arg = arguments[nextArgument];
+
+    if (arg->getTerminatesOptions())
+        *optionsAllowed = false;
+
+    switch (arg->kind) {
+      case OptionKindString:
+        arg->asStringOption()->value = argv[*i];
+        nextArgument += 1;
+        return Okay;
+      case OptionKindMultiString:
+      {
+        /* Don't advance the next argument -- there can only be one (final) variadic argument. */
+        StringArg value(argv[*i], *i);
+        return arg->asMultiStringOption()->strings.append(value) ? Okay : Fail;
+      }
+      default:
+        MOZ_CRASH("unhandled argument kind");
+    }
+}
+
+OptionParser::Result
+OptionParser::parseArgs(int inputArgc, char** argv)
+{
+    MOZ_ASSERT(inputArgc >= 0);
+    size_t argc = inputArgc;
+    /* Permit a "no more options" capability, like |--| offers in many shell interfaces. */
+    bool optionsAllowed = true;
+
+    for (size_t i = 1; i < argc; ++i) {
+        char* arg = argv[i];
+        Result r;
+        /* Note: solo dash option is actually a 'stdin' argument. */
+        if (arg[0] == '-' && arg[1] != '\0' && optionsAllowed) {
+            /* Option. */
+            Option* opt;
+            if (arg[1] == '-') {
+                if (arg[2] == '\0') {
+                    /* End of options */
+                    optionsAllowed = false;
+                    nextArgument = restArgument;
+                    continue;
+                } else {
+                    /* Long option. */
+                    opt = findOption(arg + 2);
+                    if (!opt)
+                        return error("Invalid long option: %s", arg);
+                }
+            } else {
+                /* Short option */
+                if (arg[2] != '\0')
+                    return error("Short option followed by junk: %s", arg);
+                opt = findOption(arg[1]);
+                if (!opt)
+                    return error("Invalid short option: %s", arg);
+            }
+
+            r = handleOption(opt, argc, argv, &i, &optionsAllowed);
+        } else {
+            /* Argument. */
+            r = handleArg(argc, argv, &i, &optionsAllowed);
+        }
+
+        if (r != Okay)
+            return r;
+    }
+    return Okay;
+}
+
+void
+OptionParser::setHelpOption(char shortflag, const char* longflag, const char* help)
+{
+    helpOption.setFlagInfo(shortflag, longflag, help);
+}
+
+bool
+OptionParser::getHelpOption() const
+{
+    return helpOption.value;
+}
+
+bool
+OptionParser::getBoolOption(char shortflag) const
+{
+    return findOption(shortflag)->asBoolOption()->value;
+}
+
+int
+OptionParser::getIntOption(char shortflag) const
+{
+    return findOption(shortflag)->asIntOption()->value;
+}
+
+const char*
+OptionParser::getStringOption(char shortflag) const
+{
+    return findOption(shortflag)->asStringOption()->value;
+}
+
+MultiStringRange
+OptionParser::getMultiStringOption(char shortflag) const
+{
+    const MultiStringOption* mso = findOption(shortflag)->asMultiStringOption();
+    return MultiStringRange(mso->strings.begin(), mso->strings.end());
+}
+
+bool
+OptionParser::getBoolOption(const char* longflag) const
+{
+    return findOption(longflag)->asBoolOption()->value;
+}
+
+int
+OptionParser::getIntOption(const char* longflag) const
+{
+    return findOption(longflag)->asIntOption()->value;
+}
+
+const char*
+OptionParser::getStringOption(const char* longflag) const
+{
+    return findOption(longflag)->asStringOption()->value;
+}
+
+MultiStringRange
+OptionParser::getMultiStringOption(const char* longflag) const
+{
+    const MultiStringOption* mso = findOption(longflag)->asMultiStringOption();
+    return MultiStringRange(mso->strings.begin(), mso->strings.end());
+}
+
+OptionParser::~OptionParser()
+{
+    for (Option* opt : options)
+        js_delete<Option>(opt);
+    for (Option* arg : arguments)
+        js_delete<Option>(arg);
+}
+
+Option*
+OptionParser::findOption(char shortflag)
+{
+    for (Option* opt : options) {
+        if (opt->shortflag == shortflag)
+            return opt;
+    }
+
+    if (versionOption.shortflag == shortflag)
+        return &versionOption;
+
+    return helpOption.shortflag == shortflag ? &helpOption : nullptr;
+}
+
+const Option*
+OptionParser::findOption(char shortflag) const
+{
+    return const_cast<OptionParser*>(this)->findOption(shortflag);
+}
+
+Option*
+OptionParser::findOption(const char* longflag)
+{
+    for (Option* opt : options) {
+        const char* target = opt->longflag;
+        if (opt->isValued()) {
+            size_t targetLen = strlen(target);
+            /* Permit a trailing equals sign on the longflag argument. */
+            for (size_t i = 0; i < targetLen; ++i) {
+                if (longflag[i] == '\0' || longflag[i] != target[i])
+                    goto no_match;
+            }
+            if (longflag[targetLen] == '\0' || longflag[targetLen] == '=')
+                return opt;
+        } else {
+            if (strcmp(target, longflag) == 0)
+                return opt;
+        }
+  no_match:;
+    }
+
+    if (strcmp(versionOption.longflag, longflag) == 0)
+        return &versionOption;
+
+    return strcmp(helpOption.longflag, longflag) ? nullptr : &helpOption;
+}
+
+const Option*
+OptionParser::findOption(const char* longflag) const
+{
+    return const_cast<OptionParser*>(this)->findOption(longflag);
+}
+
+/* Argument accessors */
+
+int
+OptionParser::findArgumentIndex(const char* name) const
+{
+    for (Option * const* it = arguments.begin(); it != arguments.end(); ++it) {
+        const char* target = (*it)->longflag;
+        if (strcmp(target, name) == 0)
+            return it - arguments.begin();
+    }
+    return -1;
+}
+
+Option*
+OptionParser::findArgument(const char* name)
+{
+    int index = findArgumentIndex(name);
+    return (index == -1) ? nullptr : arguments[index];
+}
+
+const Option*
+OptionParser::findArgument(const char* name) const
+{
+    int index = findArgumentIndex(name);
+    return (index == -1) ? nullptr : arguments[index];
+}
+
+const char*
+OptionParser::getStringArg(const char* name) const
+{
+    return findArgument(name)->asStringOption()->value;
+}
+
+MultiStringRange
+OptionParser::getMultiStringArg(const char* name) const
+{
+    const MultiStringOption* mso = findArgument(name)->asMultiStringOption();
+    return MultiStringRange(mso->strings.begin(), mso->strings.end());
+}
+
+/* Option builders */
+
+bool
+OptionParser::addIntOption(char shortflag, const char* longflag, const char* metavar,
+                           const char* help, int defaultValue)
+{
+    if (!options.reserve(options.length() + 1))
+        return false;
+    IntOption* io = js_new<IntOption>(shortflag, longflag, help, metavar, defaultValue);
+    if (!io)
+        return false;
+    options.infallibleAppend(io);
+    return true;
+}
+
+bool
+OptionParser::addBoolOption(char shortflag, const char* longflag, const char* help)
+{
+    if (!options.reserve(options.length() + 1))
+        return false;
+    BoolOption* bo = js_new<BoolOption>(shortflag, longflag, help);
+    if (!bo)
+        return false;
+    options.infallibleAppend(bo);
+    return true;
+}
+
+bool
+OptionParser::addStringOption(char shortflag, const char* longflag, const char* metavar,
+                              const char* help)
+{
+    if (!options.reserve(options.length() + 1))
+        return false;
+    StringOption* so = js_new<StringOption>(shortflag, longflag, help, metavar);
+    if (!so)
+        return false;
+    options.infallibleAppend(so);
+    return true;
+}
+
+bool
+OptionParser::addMultiStringOption(char shortflag, const char* longflag, const char* metavar,
+                                   const char* help)
+{
+    if (!options.reserve(options.length() + 1))
+        return false;
+    MultiStringOption* mso = js_new<MultiStringOption>(shortflag, longflag, help, metavar);
+    if (!mso)
+        return false;
+    options.infallibleAppend(mso);
+    return true;
+}
+
+/* Argument builders */
+
+bool
+OptionParser::addOptionalStringArg(const char* name, const char* help)
+{
+    if (!arguments.reserve(arguments.length() + 1))
+        return false;
+    StringOption* so = js_new<StringOption>(1, name, help, (const char*) nullptr);
+    if (!so)
+        return false;
+    arguments.infallibleAppend(so);
+    return true;
+}
+
+bool
+OptionParser::addOptionalMultiStringArg(const char* name, const char* help)
+{
+    MOZ_ASSERT_IF(!arguments.empty(), !arguments.back()->isVariadic());
+    if (!arguments.reserve(arguments.length() + 1))
+        return false;
+    MultiStringOption* mso = js_new<MultiStringOption>(1, name, help, (const char*) nullptr);
+    if (!mso)
+        return false;
+    arguments.infallibleAppend(mso);
+    return true;
+}
diff --git a/js/src/shell/jsoptparse.h b/js/src/shell/jsoptparse.h
new file mode 100644
index 0000000000..274978130e
--- /dev/null
+++ b/js/src/shell/jsoptparse.h
@@ -0,0 +1,298 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef shell_jsoptparse_h
+#define shell_jsoptparse_h
+
+#include <stdio.h>
+
+#include "jsalloc.h"
+#include "jsutil.h"
+
+#include "js/Vector.h"
+
+namespace js {
+namespace cli {
+
+namespace detail {
+
+struct BoolOption;
+struct MultiStringOption;
+struct ValuedOption;
+struct StringOption;
+struct IntOption;
+
+enum OptionKind
+{
+    OptionKindBool,
+    OptionKindString,
+    OptionKindInt,
+    OptionKindMultiString,
+    OptionKindInvalid
+};
+
+struct Option
+{
+    const char* longflag;
+    const char* help;
+    OptionKind  kind;
+    char        shortflag;
+    bool        terminatesOptions;
+
+    Option(OptionKind kind, char shortflag, const char* longflag, const char* help)
+      : longflag(longflag), help(help), kind(kind), shortflag(shortflag), terminatesOptions(false)
+    {}
+
+    virtual ~Option() = 0;
+
+    void setTerminatesOptions(bool enabled) { terminatesOptions = enabled; }
+    bool getTerminatesOptions() const { return terminatesOptions; }
+
+    virtual bool isValued() const { return false; }
+
+    /* Only some valued options are variadic (like MultiStringOptions). */
+    virtual bool isVariadic() const { return false; }
+
+    /*
+     * For arguments, the shortflag field is used to indicate whether the
+     * argument is optional.
+     */
+    bool isOptional() { return shortflag; }
+
+    void setFlagInfo(char shortflag, const char* longflag, const char* help) {
+        this->shortflag = shortflag;
+        this->longflag = longflag;
+        this->help = help;
+    }
+
+    ValuedOption* asValued();
+    const ValuedOption* asValued() const;
+
+#define OPTION_CONVERT_DECL(__cls) \
+    bool is##__cls##Option() const; \
+    __cls##Option* as##__cls##Option(); \
+    const __cls##Option* as##__cls##Option() const;
+
+    OPTION_CONVERT_DECL(Bool)
+    OPTION_CONVERT_DECL(String)
+    OPTION_CONVERT_DECL(Int)
+    OPTION_CONVERT_DECL(MultiString)
+};
+
+inline Option::~Option() {}
+
+struct BoolOption : public Option
+{
+    size_t  argno;
+    bool    value;
+
+    BoolOption(char shortflag, const char* longflag, const char* help)
+      : Option(OptionKindBool, shortflag, longflag, help), value(false)
+    {}
+
+    virtual ~BoolOption() {}
+};
+
+struct ValuedOption : public Option
+{
+    const char* metavar;
+
+    ValuedOption(OptionKind kind, char shortflag, const char* longflag, const char* help,
+                 const char* metavar)
+      : Option(kind, shortflag, longflag, help), metavar(metavar)
+    {}
+
+    virtual ~ValuedOption() = 0;
+    virtual bool isValued() const { return true; }
+};
+
+inline ValuedOption::~ValuedOption() {}
+
+struct StringOption : public ValuedOption
+{
+    const char* value;
+
+    StringOption(char shortflag, const char* longflag, const char* help, const char* metavar)
+      : ValuedOption(OptionKindString, shortflag, longflag, help, metavar), value(nullptr)
+    {}
+
+    virtual ~StringOption() {}
+};
+
+struct IntOption : public ValuedOption
+{
+    int value;
+
+    IntOption(char shortflag, const char* longflag, const char* help, const char* metavar,
+              int defaultValue)
+      : ValuedOption(OptionKindInt, shortflag, longflag, help, metavar), value(defaultValue)
+    {}
+
+    virtual ~IntOption() {}
+};
+
+struct StringArg
+{
+    char*   value;
+    size_t  argno;
+
+    StringArg(char* value, size_t argno) : value(value), argno(argno) {}
+};
+
+struct MultiStringOption : public ValuedOption
+{
+    Vector<StringArg, 0, SystemAllocPolicy> strings;
+
+    MultiStringOption(char shortflag, const char* longflag, const char* help, const char* metavar)
+      : ValuedOption(OptionKindMultiString, shortflag, longflag, help, metavar)
+    {}
+
+    virtual ~MultiStringOption() {}
+
+    virtual bool isVariadic() const { return true; }
+};
+
+} /* namespace detail */
+
+class MultiStringRange
+{
+    typedef detail::StringArg StringArg;
+    const StringArg* cur;
+    const StringArg* end;
+
+  public:
+    explicit MultiStringRange(const StringArg* cur, const StringArg* end)
+      : cur(cur), end(end) {
+        MOZ_ASSERT(end - cur >= 0);
+    }
+
+    bool empty() const { return cur == end; }
+    void popFront() { MOZ_ASSERT(!empty()); ++cur; }
+    char* front() const { MOZ_ASSERT(!empty()); return cur->value; }
+    size_t argno() const { MOZ_ASSERT(!empty()); return cur->argno; }
+};
+
+/*
+ * Builder for describing a command line interface and parsing the resulting
+ * specification.
+ *
+ * - A multi-option is an option that can appear multiple times and still
+ *   parse as valid command line arguments.
+ * - An "optional argument" is supported for backwards compatibility with prior
+ *   command line interface usage. Once one optional argument has been added,
+ *   *only* optional arguments may be added.
+ */
+class OptionParser
+{
+  public:
+    enum Result
+    {
+        Okay = 0,
+        Fail,       /* As in, allocation fail. */
+        ParseError, /* Successfully parsed but with an error. */
+        EarlyExit   /* Successfully parsed but exits the program,
+                     * for example with --help and --version. */
+    };
+
+  private:
+    typedef Vector<detail::Option*, 0, SystemAllocPolicy> Options;
+    typedef detail::Option Option;
+    typedef detail::BoolOption BoolOption;
+
+    Options     options;
+    Options     arguments;
+    BoolOption  helpOption;
+    BoolOption  versionOption;
+    const char* usage;
+    const char* version;
+    const char* descr;
+    size_t      descrWidth;
+    size_t      helpWidth;
+    size_t      nextArgument;
+
+    // If '--' is passed, all remaining arguments should be interpreted as the
+    // argument at index 'restArgument'. Defaults to the next unassigned
+    // argument.
+    int         restArgument;
+
+    static const char prognameMeta[];
+
+    Option* findOption(char shortflag);
+    const Option* findOption(char shortflag) const;
+    Option* findOption(const char* longflag);
+    const Option* findOption(const char* longflag) const;
+    int findArgumentIndex(const char* name) const;
+    Option* findArgument(const char* name);
+    const Option* findArgument(const char* name) const;
+
+    Result error(const char* fmt, ...) MOZ_FORMAT_PRINTF(2, 3);
+    Result extractValue(size_t argc, char** argv, size_t* i, char** value);
+    Result handleArg(size_t argc, char** argv, size_t* i, bool* optsAllowed);
+    Result handleOption(Option* opt, size_t argc, char** argv, size_t* i, bool* optsAllowed);
+
+  public:
+    explicit OptionParser(const char* usage)
+      : helpOption('h', "help", "Display help information"),
+        versionOption('v', "version", "Display version information and exit"),
+        usage(usage), version(nullptr), descr(nullptr), descrWidth(80), helpWidth(80),
+        nextArgument(0), restArgument(-1)
+    {}
+
+    ~OptionParser();
+
+    Result parseArgs(int argc, char** argv);
+    Result printHelp(const char* progname);
+    Result printVersion();
+
+    /* Metadata */
+
+    void setVersion(const char* v) { version = v; }
+    void setHelpWidth(size_t width) { helpWidth = width; }
+    void setDescriptionWidth(size_t width) { descrWidth = width; }
+    void setDescription(const char* description) { descr = description; }
+    void setHelpOption(char shortflag, const char* longflag, const char* help);
+    void setArgTerminatesOptions(const char* name, bool enabled);
+    void setArgCapturesRest(const char* name);
+
+    /* Arguments: no further arguments may be added after a variadic argument. */
+
+    bool addOptionalStringArg(const char* name, const char* help);
+    bool addOptionalMultiStringArg(const char* name, const char* help);
+
+    const char* getStringArg(const char* name) const;
+    MultiStringRange getMultiStringArg(const char* name) const;
+
+    /* Options */
+
+    bool addBoolOption(char shortflag, const char* longflag, const char* help);
+    bool addStringOption(char shortflag, const char* longflag, const char* help,
+                         const char* metavar);
+    bool addIntOption(char shortflag, const char* longflag, const char* help,
+                      const char* metavar, int defaultValue);
+    bool addMultiStringOption(char shortflag, const char* longflag, const char* help,
+                              const char* metavar);
+    bool addOptionalVariadicArg(const char* name);
+
+    int getIntOption(char shortflag) const;
+    int getIntOption(const char* longflag) const;
+    const char* getStringOption(char shortflag) const;
+    const char* getStringOption(const char* longflag) const;
+    bool getBoolOption(char shortflag) const;
+    bool getBoolOption(const char* longflag) const;
+    MultiStringRange getMultiStringOption(char shortflag) const;
+    MultiStringRange getMultiStringOption(const char* longflag) const;
+
+    /*
+     * Return whether the help option was present (and thus help was already
+     * displayed during parse_args).
+     */
+    bool getHelpOption() const;
+};
+
+} /* namespace cli */
+} /* namespace js */
+
+#endif /* shell_jsoptparse_h */
diff --git a/js/src/shell/jsshell.cpp b/js/src/shell/jsshell.cpp
new file mode 100644
index 0000000000..7f8e53b9a4
--- /dev/null
+++ b/js/src/shell/jsshell.cpp
@@ -0,0 +1,74 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// jsshell.cpp - Utilities for the JS shell
+
+#include "shell/jsshell.h"
+
+#include "jsapi.h"
+#include "jsfriendapi.h"
+
+#include "vm/StringBuffer.h"
+
+using namespace JS;
+
+namespace js {
+namespace shell {
+
+bool
+GenerateInterfaceHelp(JSContext* cx, HandleObject obj, const char* name)
+{
+    AutoIdVector idv(cx);
+    if (!GetPropertyKeys(cx, obj, JSITER_OWNONLY | JSITER_HIDDEN, &idv))
+        return false;
+
+    StringBuffer buf(cx);
+    if (!buf.append(' '))
+        return false;
+
+    for (size_t i = 0; i < idv.length(); i++) {
+        RootedValue v(cx);
+        RootedId id(cx, idv[i]);
+        if (!JS_GetPropertyById(cx, obj, id, &v))
+            return false;
+        if (!v.isObject())
+            continue;
+        bool hasHelp = false;
+        RootedObject prop(cx, &v.toObject());
+        if (!JS_GetProperty(cx, prop, "usage", &v))
+            return false;
+        if (v.isString())
+            hasHelp = true;
+        if (!JS_GetProperty(cx, prop, "help", &v))
+            return false;
+        if (v.isString())
+            hasHelp = true;
+        if (hasHelp) {
+            if (!buf.append(' ') ||
+                !buf.append(name, strlen(name)) ||
+                !buf.append('.') ||
+                !buf.append(JSID_TO_FLAT_STRING(id)))
+            {
+                return false;
+            }
+        }
+    }
+
+    RootedString s(cx, buf.finishString());
+    if (!s || !JS_DefineProperty(cx, obj, "help", s, 0))
+        return false;
+
+    if (!buf.append(name, strlen(name)) || !buf.append(" - interface object", 20))
+        return false;
+    s = buf.finishString();
+    if (!s || !JS_DefineProperty(cx, obj, "usage", s, 0))
+        return false;
+
+    return true;
+}
+
+} // namespace shell
+} // namespace js
diff --git a/js/src/shell/jsshell.h b/js/src/shell/jsshell.h
new file mode 100644
index 0000000000..a3ecbef999
--- /dev/null
+++ b/js/src/shell/jsshell.h
@@ -0,0 +1,84 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef jsshell_js_h
+#define jsshell_js_h
+
+#include "jsapi.h"
+
+namespace js {
+namespace shell {
+
+enum JSShellErrNum {
+#define MSG_DEF(name, count, exception, format) \
+    name,
+#include "jsshell.msg"
+#undef MSG_DEF
+    JSShellErr_Limit
+};
+
+const JSErrorFormatString*
+my_GetErrorMessage(void* userRef, const unsigned errorNumber);
+
+void
+WarningReporter(JSContext* cx, JSErrorReport* report);
+
+class MOZ_STACK_CLASS AutoReportException
+{
+    JSContext* cx;
+  public:
+    explicit AutoReportException(JSContext* cx)
+      : cx(cx)
+    {}
+    ~AutoReportException();
+};
+
+bool
+GenerateInterfaceHelp(JSContext* cx, JS::HandleObject obj, const char* name);
+
+JSString*
+FileAsString(JSContext* cx, JS::HandleString pathnameStr);
+
+class AutoCloseFile
+{
+  private:
+    FILE* f_;
+  public:
+    explicit AutoCloseFile(FILE* f) : f_(f) {}
+    ~AutoCloseFile() {
+        (void) release();
+    }
+    bool release() {
+        bool success = true;
+        if (f_ && f_ != stdin && f_ != stdout && f_ != stderr)
+            success = !fclose(f_);
+        f_ = nullptr;
+        return success;
+    }
+};
+
+// Reference counted file.
+struct RCFile {
+    FILE* fp;
+    uint32_t numRefs;
+
+    RCFile() : fp(nullptr), numRefs(0) {}
+    explicit RCFile(FILE* fp) : fp(fp), numRefs(0) {}
+
+    void acquire() { numRefs++; }
+
+    // Starts out with a ref count of zero.
+    static RCFile* create(JSContext* cx, const char* filename, const char* mode);
+
+    void close();
+    bool isOpen() const { return fp; }
+    bool release();
+};
+
+} /* namespace shell */
+} /* namespace js */
+
+#endif
diff --git a/js/src/shell/moz.build b/js/src/shell/moz.build
new file mode 100644
index 0000000000..72ea8145cc
--- /dev/null
+++ b/js/src/shell/moz.build
@@ -0,0 +1,67 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+if CONFIG['JS_SHELL_NAME']:
+    GeckoProgram(CONFIG['JS_SHELL_NAME'], linkage=None)
+    if CONFIG['JS_BUNDLED_EDITLINE']:
+        USE_LIBS += ['editline']
+    USE_LIBS += ['static:js']
+
+UNIFIED_SOURCES += [
+    'js.cpp',
+    'jsoptparse.cpp',
+    'jsshell.cpp',
+    'OSObject.cpp'
+]
+
+DEFINES['EXPORT_JS_API'] = True
+
+# Also set in ../moz.build
+DEFINES['ENABLE_SHARED_ARRAY_BUFFER'] = True
+
+if CONFIG['_MSC_VER']:
+    # unnecessary PGO for js shell.  But gcc cannot turn off pgo because it is
+    # necessary to link PGO lib on gcc when a object/static lib are compiled
+    # for PGO.
+    NO_PGO = True
+
+LOCAL_INCLUDES += [
+    '!..',
+    '..',
+]
+
+OS_LIBS += CONFIG['EDITLINE_LIBS']
+OS_LIBS += CONFIG['MOZ_ZLIB_LIBS']
+
+if CONFIG['ENABLE_INTL_API'] and CONFIG['MOZ_ICU_DATA_ARCHIVE']:
+    # The ICU libraries linked into libmozjs will not include the ICU data,
+    # so link it directly.
+    USE_LIBS += ['icudata']
+
+# Prepare module loader JS code for embedding
+GENERATED_FILES += ['shellmoduleloader.out.h']
+shellmoduleloader = GENERATED_FILES['shellmoduleloader.out.h']
+shellmoduleloader.script = '../builtin/embedjs.py:generate_shellmoduleloader'
+shellmoduleloader.inputs = [
+    '../js.msg',
+    'ModuleLoader.js',
+]
+
+if CONFIG['GNU_CXX']:
+    CXXFLAGS += ['-Wno-shadow', '-Werror=format']
+
+# This is intended as a temporary workaround to enable VS2015.
+if CONFIG['_MSC_VER']:
+    CXXFLAGS += ['-wd4312']
+
+# Place a GDB Python auto-load file next to the shell executable, both in
+# the build directory and in the dist/bin directory.
+DEFINES['topsrcdir'] = '%s/js/src' % TOPSRCDIR
+FINAL_TARGET_PP_FILES += ['js-gdb.py.in']
+OBJDIR_FILES.js.src.shell += ['!/dist/bin/js-gdb.py']
+
+# People expect the js shell to wind up in the top-level JS dir.
+OBJDIR_FILES.js.src += ['!js%s' % CONFIG['BIN_SUFFIX']]