diff -r 000000000000 -r 6474c204b198 js/examples/jorendb.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/examples/jorendb.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,510 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sw=4 et tw=78:
+ *
+ * jorendb - A toy command-line debugger for shell-js programs.
+ *
+ * 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/.
+ */
+
+/*
+ * jorendb is a simple command-line debugger for shell-js programs. It is
+ * intended as a demo of the Debugger object (as there are no shell js programs
+ * to speak of).
+ *
+ * To run it: $JS -d path/to/this/file/jorendb.js
+ * To run some JS code under it, try:
+ *    (jorendb) print load("my-script-to-debug.js")
+ * Execution will stop at debugger statements and you'll get a jorendb prompt.
+ */
+
+// Debugger state.
+var focusedFrame = null;
+var topFrame = null;
+var debuggeeValues = {};
+var nextDebuggeeValueIndex = 1;
+var lastExc = null;
+
+// Cleanup functions to run when we next re-enter the repl.
+var replCleanups = [];
+
+// Convert a debuggee value v to a string.
+function dvToString(v) {
+    return (typeof v !== 'object' || v === null) ? uneval(v) : "[object " + v.class + "]";
+}
+
+function showDebuggeeValue(dv) {
+    var dvrepr = dvToString(dv);
+    var i = nextDebuggeeValueIndex++;
+    debuggeeValues["$" + i] = dv;
+    print("$" + i + " = " + dvrepr);
+}
+
+Object.defineProperty(Debugger.Frame.prototype, "num", {
+    configurable: true,
+    enumerable: false,
+    get: function () {
+            var i = 0;
+            for (var f = topFrame; f && f !== this; f = f.older)
+                i++;
+            return f === null ? undefined : i;
+        }
+    });
+
+Debugger.Frame.prototype.frameDescription = function frameDescription() {
+    if (this.type == "call")
+        return ((this.callee.name || '<anonymous>') +
+                "(" + this.arguments.map(dvToString).join(", ") + ")");
+    else
+        return this.type + " code";
+}
+
+Debugger.Frame.prototype.positionDescription = function positionDescription() {
+    if (this.script) {
+        var line = this.script.getOffsetLine(this.offset);
+        if (this.script.url)
+            return this.script.url + ":" + line;
+        return "line " + line;
+    }
+    return null;
+}
+
+Debugger.Frame.prototype.fullDescription = function fullDescription() {
+    var fr = this.frameDescription();
+    var pos = this.positionDescription();
+    if (pos)
+        return fr + ", " + pos;
+    return fr;
+}
+
+Object.defineProperty(Debugger.Frame.prototype, "line", {
+        configurable: true,
+        enumerable: false,
+        get: function() {
+            if (this.script)
+                return this.script.getOffsetLine(this.offset);
+            else
+                return null;
+        }
+    });
+
+function callDescription(f) {
+    return ((f.callee.name || '<anonymous>') +
+            "(" + f.arguments.map(dvToString).join(", ") + ")");
+}
+
+function showFrame(f, n) {
+    if (f === undefined || f === null) {
+        f = focusedFrame;
+        if (f === null) {
+            print("No stack.");
+            return;
+        }
+    }
+    if (n === undefined) {
+        n = f.num;
+        if (n === undefined)
+            throw new Error("Internal error: frame not on stack");
+    }
+
+    print('#' + n + " " + f.fullDescription());
+}
+
+function saveExcursion(fn) {
+    var tf = topFrame, ff = focusedFrame;
+    try {
+        return fn();
+    } finally {
+        topFrame = tf;
+        focusedFrame = ff;
+    }
+}
+
+// Evaluate an expression in the Debugger global
+function evalCommand(expr) {
+    eval(expr);
+}
+
+function quitCommand() {
+    dbg.enabled = false;
+    quit(0);
+}
+
+function backtraceCommand() {
+    if (topFrame === null)
+        print("No stack.");
+    for (var i = 0, f = topFrame; f; i++, f = f.older)
+        showFrame(f, i);
+}
+
+function printCommand(rest) {
+    // This is the real deal.
+    var cv = saveExcursion(
+        () => focusedFrame == null
+              ? debuggeeGlobalWrapper.evalInGlobalWithBindings(rest, debuggeeValues)
+              : focusedFrame.evalWithBindings(rest, debuggeeValues));
+    if (cv === null) {
+        if (!dbg.enabled)
+            return [cv];
+        print("Debuggee died.");
+    } else if ('return' in cv) {
+        if (!dbg.enabled)
+            return [undefined];
+        showDebuggeeValue(cv.return);
+    } else {
+        if (!dbg.enabled)
+            return [cv];
+        print("Exception caught. (To rethrow it, type 'throw'.)");
+        lastExc = cv.throw;
+        showDebuggeeValue(lastExc);
+    }
+}
+
+function detachCommand() {
+    dbg.enabled = false;
+    return [undefined];
+}
+
+function continueCommand() {
+    if (focusedFrame === null) {
+        print("No stack.");
+        return;
+    }
+    return [undefined];
+}
+
+function throwCommand(rest) {
+    var v;
+    if (focusedFrame !== topFrame) {
+        print("To throw, you must select the newest frame (use 'frame 0').");
+        return;
+    } else if (focusedFrame === null) {
+        print("No stack.");
+        return;
+    } else if (rest === '') {
+        return [{throw: lastExc}];
+    } else {
+        var cv = saveExcursion(function () { return focusedFrame.eval(rest); });
+        if (cv === null) {
+            if (!dbg.enabled)
+                return [cv];
+            print("Debuggee died while determining what to throw. Stopped.");
+        } else if ('return' in cv) {
+            return [{throw: cv.return}];
+        } else {
+            if (!dbg.enabled)
+                return [cv];
+            print("Exception determining what to throw. Stopped.");
+            showDebuggeeValue(cv.throw);
+        }
+        return;
+    }
+}
+
+function frameCommand(rest) {
+    var n, f;
+    if (rest.match(/[0-9]+/)) {
+        n = +rest;
+        f = topFrame;
+        if (f === null) {
+            print("No stack.");
+            return;
+        }
+        for (var i = 0; i < n && f; i++) {
+            if (!f.older) {
+                print("There is no frame " + rest + ".");
+                return;
+            }
+            f.older.younger = f;
+            f = f.older;
+        }
+        focusedFrame = f;
+        showFrame(f, n);
+    } else if (rest !== '') {
+        if (topFrame === null)
+            print("No stack.");
+        else
+            showFrame();
+    } else {
+        print("do what now?");
+    }
+}
+
+function upCommand() {
+    if (focusedFrame === null)
+        print("No stack.");
+    else if (focusedFrame.older === null)
+        print("Initial frame selected; you cannot go up.");
+    else {
+        focusedFrame.older.younger = focusedFrame;
+        focusedFrame = focusedFrame.older;
+        showFrame();
+    }
+}
+
+function downCommand() {
+    if (focusedFrame === null)
+        print("No stack.");
+    else if (!focusedFrame.younger)
+        print("Youngest frame selected; you cannot go down.");
+    else {
+        focusedFrame = focusedFrame.younger;
+        showFrame();
+    }
+}
+
+function forcereturnCommand(rest) {
+    var v;
+    var f = focusedFrame;
+    if (f !== topFrame) {
+        print("To forcereturn, you must select the newest frame (use 'frame 0').");
+    } else if (f === null) {
+        print("Nothing on the stack.");
+    } else if (rest === '') {
+        return [{return: undefined}];
+    } else {
+        var cv = saveExcursion(function () { return f.eval(rest); });
+        if (cv === null) {
+            if (!dbg.enabled)
+                return [cv];
+            print("Debuggee died while determining what to forcereturn. Stopped.");
+        } else if ('return' in cv) {
+            return [{return: cv.return}];
+        } else {
+            if (!dbg.enabled)
+                return [cv];
+            print("Error determining what to forcereturn. Stopped.");
+            showDebuggeeValue(cv.throw);
+        }
+    }
+}
+
+function printPop(f, c) {
+    var fdesc = f.fullDescription();
+    if (c.return) {
+        print("frame returning (still selected): " + fdesc);
+        showDebuggeeValue(c.return);
+    } else if (c.throw) {
+        print("frame threw exception: " + fdesc);
+        showDebuggeeValue(c.throw);
+        print("(To rethrow it, type 'throw'.)");
+        lastExc = c.throw;
+    } else {
+        print("frame was terminated: " + fdesc);
+    }
+}
+
+// Set |prop| on |obj| to |value|, but then restore its current value
+// when we next enter the repl.
+function setUntilRepl(obj, prop, value) {
+    var saved = obj[prop];
+    obj[prop] = value;
+    replCleanups.push(function () { obj[prop] = saved; });
+}
+
+function doStepOrNext(kind) {
+    var startFrame = topFrame;
+    var startLine = startFrame.line;
+    print("stepping in:   " + startFrame.fullDescription());
+    print("starting line: " + uneval(startLine));
+
+    function stepPopped(completion) {
+        // Note that we're popping this frame; we need to watch for
+        // subsequent step events on its caller.
+        this.reportedPop = true;
+        printPop(this, completion);
+        topFrame = focusedFrame = this;
+        return repl();
+    }
+
+    function stepEntered(newFrame) {
+        print("entered frame: " + newFrame.fullDescription());
+        topFrame = focusedFrame = newFrame;
+        return repl();
+    }
+
+    function stepStepped() {
+        print("stepStepped: " + this.fullDescription());
+        // If we've changed frame or line, then report that.
+        if (this !== startFrame || this.line != startLine) {
+            topFrame = focusedFrame = this;
+            if (focusedFrame != startFrame)
+                print(focusedFrame.fullDescription());
+            return repl();
+        }
+
+        // Otherwise, let execution continue.
+        return undefined;
+    }
+
+    if (kind.step)
+        setUntilRepl(dbg, 'onEnterFrame', stepEntered);
+
+    // If we're stepping after an onPop, watch for steps and pops in the
+    // next-older frame; this one is done.
+    var stepFrame = startFrame.reportedPop ? startFrame.older : startFrame;
+    if (!stepFrame || !stepFrame.script)
+        stepFrame = null;
+    if (stepFrame) {
+        setUntilRepl(stepFrame, 'onStep', stepStepped);
+        setUntilRepl(stepFrame, 'onPop',  stepPopped);
+    }
+
+    // Let the program continue!
+    return [undefined];
+}
+
+function stepCommand() { return doStepOrNext({step:true}); }
+function nextCommand() { return doStepOrNext({next:true}); }
+
+// Build the table of commands.
+var commands = {};
+var commandArray = [
+    backtraceCommand, "bt", "where",
+    continueCommand, "c",
+    detachCommand,
+    downCommand, "d",
+    forcereturnCommand,
+    frameCommand, "f",
+    nextCommand, "n",
+    printCommand, "p",
+    quitCommand, "q",
+    stepCommand, "s",
+    throwCommand, "t",
+    upCommand, "u",
+    helpCommand, "h",
+    evalCommand, "!",
+    ];
+var last = null;
+for (var i = 0; i < commandArray.length; i++) {
+    var cmd = commandArray[i];
+    if (typeof cmd === "string")
+        commands[cmd] = last;
+    else
+        last = commands[cmd.name.replace(/Command$/, '')] = cmd;
+}
+
+function helpCommand(rest) {
+    print("Available commands:");
+    var printcmd = function(group) {
+        print("  " + group.join(", "));
+    }
+
+    var group = [];
+    for (var cmd of commandArray) {
+        if (typeof cmd === "string") {
+            group.push(cmd);
+        } else {
+            if (group.length) printcmd(group);
+            group = [ cmd.name.replace(/Command$/, '') ];
+        }
+    }
+    printcmd(group);
+}
+
+// Break cmd into two parts: its first word and everything else. If it begins
+// with punctuation, treat that as a separate word.
+function breakcmd(cmd) {
+    cmd = cmd.trimLeft();
+    if ("!@#$%^&*_+=/?.,<>:;'\"".indexOf(cmd.substr(0, 1)) != -1)
+        return [cmd.substr(0, 1), cmd.substr(1).trimLeft()];
+    var m = /\s/.exec(cmd);
+    if (m === null)
+        return [cmd, ''];
+    return [cmd.slice(0, m.index), cmd.slice(m.index).trimLeft()];
+}
+
+function runcmd(cmd) {
+    var pieces = breakcmd(cmd);
+    if (pieces[0] === "")
+        return undefined;
+
+    var first = pieces[0], rest = pieces[1];
+    if (!commands.hasOwnProperty(first)) {
+        print("unrecognized command '" + first + "'");
+        return undefined;
+    }
+
+    var cmd = commands[first];
+    if (cmd.length === 0 && rest !== '') {
+        print("this command cannot take an argument");
+        return undefined;
+    }
+
+    return cmd(rest);
+}
+
+function repl() {
+    while (replCleanups.length > 0)
+        replCleanups.pop()();
+
+    var cmd;
+    for (;;) {
+        putstr("\n" + prompt);
+        cmd = readline();
+        if (cmd === null)
+            return null;
+
+        try {
+            var result = runcmd(cmd);
+            if (result === undefined)
+                ; // do nothing
+            else if (Array.isArray(result))
+                return result[0];
+            else
+                throw new Error("Internal error: result of runcmd wasn't array or undefined");
+        } catch (exc) {
+            print("*** Internal error: exception in the debugger code.");
+            print("    " + exc);
+            print(exc.stack);
+        }
+    }
+}
+
+var dbg = new Debugger();
+dbg.onDebuggerStatement = function (frame) {
+    return saveExcursion(function () {
+            topFrame = focusedFrame = frame;
+            print("'debugger' statement hit.");
+            showFrame();
+            return repl();
+        });
+};
+dbg.onThrow = function (frame, exc) {
+    return saveExcursion(function () {
+            topFrame = focusedFrame = frame;
+            print("Unwinding due to exception. (Type 'c' to continue unwinding.)");
+            showFrame();
+            print("Exception value is:");
+            showDebuggeeValue(exc);
+            return repl();
+        });
+};
+
+// The depth of jorendb nesting.
+var jorendbDepth;
+if (typeof jorendbDepth == 'undefined') jorendbDepth = 0;
+
+var debuggeeGlobal = newGlobal("new-compartment");
+debuggeeGlobal.jorendbDepth = jorendbDepth + 1;
+var debuggeeGlobalWrapper = dbg.addDebuggee(debuggeeGlobal);
+
+print("jorendb version -0.0");
+prompt = '(' + Array(jorendbDepth+1).join('meta-') + 'jorendb) ';
+
+var args = arguments;
+while(args.length > 0) {
+    var arg = args.shift();
+    if (arg == '-f') {
+        arg = args.shift();
+        debuggeeGlobal.evaluate(read(arg), { fileName: arg, lineNumber: 1 });
+    } else if (arg == '-e') {
+        arg = args.shift();
+        debuggeeGlobal.eval(arg);
+    } else {
+        throw("jorendb does not implement command-line argument '" + arg + "'");
+    }
+}
+
+repl();