511 lines
14 KiB
JavaScript
511 lines
14 KiB
JavaScript
/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*-
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* vim: set ts=8 sw=4 et tw=78:
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*
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* jorendb - A toy command-line debugger for shell-js programs.
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*/
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/*
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* jorendb is a simple command-line debugger for shell-js programs. It is
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* intended as a demo of the Debugger object (as there are no shell js programs
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* to speak of).
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*
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* To run it: $JS -d path/to/this/file/jorendb.js
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* To run some JS code under it, try:
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* (jorendb) print load("my-script-to-debug.js")
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* Execution will stop at debugger statements and you'll get a jorendb prompt.
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*/
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// Debugger state.
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var focusedFrame = null;
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var topFrame = null;
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var debuggeeValues = {};
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var nextDebuggeeValueIndex = 1;
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var lastExc = null;
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// Cleanup functions to run when we next re-enter the repl.
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var replCleanups = [];
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// Convert a debuggee value v to a string.
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function dvToString(v) {
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return (typeof v !== 'object' || v === null) ? uneval(v) : "[object " + v.class + "]";
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}
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function showDebuggeeValue(dv) {
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var dvrepr = dvToString(dv);
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var i = nextDebuggeeValueIndex++;
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debuggeeValues["$" + i] = dv;
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print("$" + i + " = " + dvrepr);
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}
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Object.defineProperty(Debugger.Frame.prototype, "num", {
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configurable: true,
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enumerable: false,
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get: function () {
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var i = 0;
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for (var f = topFrame; f && f !== this; f = f.older)
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i++;
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return f === null ? undefined : i;
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}
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});
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Debugger.Frame.prototype.frameDescription = function frameDescription() {
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if (this.type == "call")
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return ((this.callee.name || '<anonymous>') +
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"(" + this.arguments.map(dvToString).join(", ") + ")");
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else
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return this.type + " code";
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}
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Debugger.Frame.prototype.positionDescription = function positionDescription() {
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if (this.script) {
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var line = this.script.getOffsetLocation(this.offset).lineNumber;
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if (this.script.url)
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return this.script.url + ":" + line;
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return "line " + line;
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}
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return null;
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}
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Debugger.Frame.prototype.fullDescription = function fullDescription() {
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var fr = this.frameDescription();
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var pos = this.positionDescription();
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if (pos)
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return fr + ", " + pos;
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return fr;
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}
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Object.defineProperty(Debugger.Frame.prototype, "line", {
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configurable: true,
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enumerable: false,
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get: function() {
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if (this.script)
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return this.script.getOffsetLocation(this.offset).lineNumber;
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else
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return null;
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}
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});
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function callDescription(f) {
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return ((f.callee.name || '<anonymous>') +
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"(" + f.arguments.map(dvToString).join(", ") + ")");
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}
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function showFrame(f, n) {
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if (f === undefined || f === null) {
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f = focusedFrame;
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if (f === null) {
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print("No stack.");
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return;
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}
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}
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if (n === undefined) {
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n = f.num;
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if (n === undefined)
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throw new Error("Internal error: frame not on stack");
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}
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print('#' + n + " " + f.fullDescription());
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}
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function saveExcursion(fn) {
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var tf = topFrame, ff = focusedFrame;
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try {
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return fn();
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} finally {
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topFrame = tf;
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focusedFrame = ff;
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}
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}
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// Evaluate an expression in the Debugger global
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function evalCommand(expr) {
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eval(expr);
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}
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function quitCommand() {
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dbg.enabled = false;
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quit(0);
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}
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function backtraceCommand() {
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if (topFrame === null)
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print("No stack.");
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for (var i = 0, f = topFrame; f; i++, f = f.older)
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showFrame(f, i);
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}
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function printCommand(rest) {
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// This is the real deal.
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var cv = saveExcursion(
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() => focusedFrame == null
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? debuggeeGlobalWrapper.executeInGlobalWithBindings(rest, debuggeeValues)
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: focusedFrame.evalWithBindings(rest, debuggeeValues));
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if (cv === null) {
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if (!dbg.enabled)
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return [cv];
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print("Debuggee died.");
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} else if ('return' in cv) {
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if (!dbg.enabled)
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return [undefined];
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showDebuggeeValue(cv.return);
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} else {
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if (!dbg.enabled)
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return [cv];
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print("Exception caught. (To rethrow it, type 'throw'.)");
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lastExc = cv.throw;
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showDebuggeeValue(lastExc);
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}
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}
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function detachCommand() {
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dbg.enabled = false;
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return [undefined];
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}
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function continueCommand() {
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if (focusedFrame === null) {
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print("No stack.");
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return;
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}
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return [undefined];
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}
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function throwCommand(rest) {
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var v;
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if (focusedFrame !== topFrame) {
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print("To throw, you must select the newest frame (use 'frame 0').");
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return;
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} else if (focusedFrame === null) {
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print("No stack.");
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return;
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} else if (rest === '') {
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return [{throw: lastExc}];
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} else {
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var cv = saveExcursion(function () { return focusedFrame.eval(rest); });
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if (cv === null) {
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if (!dbg.enabled)
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return [cv];
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print("Debuggee died while determining what to throw. Stopped.");
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} else if ('return' in cv) {
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return [{throw: cv.return}];
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} else {
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if (!dbg.enabled)
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return [cv];
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print("Exception determining what to throw. Stopped.");
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showDebuggeeValue(cv.throw);
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}
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return;
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}
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}
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function frameCommand(rest) {
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var n, f;
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if (rest.match(/[0-9]+/)) {
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n = +rest;
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f = topFrame;
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if (f === null) {
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print("No stack.");
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return;
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}
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for (var i = 0; i < n && f; i++) {
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if (!f.older) {
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print("There is no frame " + rest + ".");
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return;
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}
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f.older.younger = f;
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f = f.older;
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}
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focusedFrame = f;
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showFrame(f, n);
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} else if (rest !== '') {
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if (topFrame === null)
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print("No stack.");
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else
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showFrame();
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} else {
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print("do what now?");
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}
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}
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function upCommand() {
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if (focusedFrame === null)
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print("No stack.");
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else if (focusedFrame.older === null)
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print("Initial frame selected; you cannot go up.");
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else {
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focusedFrame.older.younger = focusedFrame;
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focusedFrame = focusedFrame.older;
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showFrame();
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}
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}
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function downCommand() {
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if (focusedFrame === null)
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print("No stack.");
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else if (!focusedFrame.younger)
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print("Youngest frame selected; you cannot go down.");
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else {
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focusedFrame = focusedFrame.younger;
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showFrame();
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}
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}
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function forcereturnCommand(rest) {
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var v;
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var f = focusedFrame;
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if (f !== topFrame) {
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print("To forcereturn, you must select the newest frame (use 'frame 0').");
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} else if (f === null) {
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print("Nothing on the stack.");
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} else if (rest === '') {
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return [{return: undefined}];
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} else {
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var cv = saveExcursion(function () { return f.eval(rest); });
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if (cv === null) {
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if (!dbg.enabled)
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return [cv];
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print("Debuggee died while determining what to forcereturn. Stopped.");
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} else if ('return' in cv) {
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return [{return: cv.return}];
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} else {
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if (!dbg.enabled)
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return [cv];
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print("Error determining what to forcereturn. Stopped.");
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showDebuggeeValue(cv.throw);
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}
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}
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}
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function printPop(f, c) {
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var fdesc = f.fullDescription();
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if (c.return) {
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print("frame returning (still selected): " + fdesc);
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showDebuggeeValue(c.return);
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} else if (c.throw) {
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print("frame threw exception: " + fdesc);
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showDebuggeeValue(c.throw);
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print("(To rethrow it, type 'throw'.)");
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lastExc = c.throw;
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} else {
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print("frame was terminated: " + fdesc);
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}
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}
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// Set |prop| on |obj| to |value|, but then restore its current value
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// when we next enter the repl.
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function setUntilRepl(obj, prop, value) {
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var saved = obj[prop];
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obj[prop] = value;
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replCleanups.push(function () { obj[prop] = saved; });
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}
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function doStepOrNext(kind) {
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var startFrame = topFrame;
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var startLine = startFrame.line;
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print("stepping in: " + startFrame.fullDescription());
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print("starting line: " + uneval(startLine));
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function stepPopped(completion) {
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// Note that we're popping this frame; we need to watch for
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// subsequent step events on its caller.
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this.reportedPop = true;
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printPop(this, completion);
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topFrame = focusedFrame = this;
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return repl();
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}
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function stepEntered(newFrame) {
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print("entered frame: " + newFrame.fullDescription());
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topFrame = focusedFrame = newFrame;
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return repl();
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}
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function stepStepped() {
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print("stepStepped: " + this.fullDescription());
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// If we've changed frame or line, then report that.
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if (this !== startFrame || this.line != startLine) {
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topFrame = focusedFrame = this;
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if (focusedFrame != startFrame)
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print(focusedFrame.fullDescription());
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return repl();
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}
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// Otherwise, let execution continue.
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return undefined;
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}
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if (kind.step)
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setUntilRepl(dbg, 'onEnterFrame', stepEntered);
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// If we're stepping after an onPop, watch for steps and pops in the
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// next-older frame; this one is done.
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var stepFrame = startFrame.reportedPop ? startFrame.older : startFrame;
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if (!stepFrame || !stepFrame.script)
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stepFrame = null;
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if (stepFrame) {
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setUntilRepl(stepFrame, 'onStep', stepStepped);
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setUntilRepl(stepFrame, 'onPop', stepPopped);
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}
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// Let the program continue!
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return [undefined];
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}
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function stepCommand() { return doStepOrNext({step:true}); }
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function nextCommand() { return doStepOrNext({next:true}); }
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// Build the table of commands.
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var commands = {};
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var commandArray = [
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backtraceCommand, "bt", "where",
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continueCommand, "c",
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detachCommand,
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downCommand, "d",
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forcereturnCommand,
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frameCommand, "f",
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nextCommand, "n",
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printCommand, "p",
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quitCommand, "q",
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stepCommand, "s",
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throwCommand, "t",
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upCommand, "u",
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helpCommand, "h",
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evalCommand, "!",
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];
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var last = null;
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for (var i = 0; i < commandArray.length; i++) {
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var cmd = commandArray[i];
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if (typeof cmd === "string")
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commands[cmd] = last;
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else
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last = commands[cmd.name.replace(/Command$/, '')] = cmd;
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}
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function helpCommand(rest) {
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print("Available commands:");
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var printcmd = function(group) {
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print(" " + group.join(", "));
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}
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var group = [];
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for (var cmd of commandArray) {
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if (typeof cmd === "string") {
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group.push(cmd);
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} else {
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if (group.length) printcmd(group);
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group = [ cmd.name.replace(/Command$/, '') ];
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}
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}
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printcmd(group);
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}
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// Break cmd into two parts: its first word and everything else. If it begins
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// with punctuation, treat that as a separate word.
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function breakcmd(cmd) {
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cmd = cmd.trimLeft();
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if ("!@#$%^&*_+=/?.,<>:;'\"".indexOf(cmd.substr(0, 1)) != -1)
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return [cmd.substr(0, 1), cmd.substr(1).trimLeft()];
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var m = /\s/.exec(cmd);
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if (m === null)
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return [cmd, ''];
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return [cmd.slice(0, m.index), cmd.slice(m.index).trimLeft()];
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}
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function runcmd(cmd) {
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var pieces = breakcmd(cmd);
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if (pieces[0] === "")
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return undefined;
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var first = pieces[0], rest = pieces[1];
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if (!commands.hasOwnProperty(first)) {
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print("unrecognized command '" + first + "'");
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return undefined;
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}
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var cmd = commands[first];
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if (cmd.length === 0 && rest !== '') {
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print("this command cannot take an argument");
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return undefined;
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}
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return cmd(rest);
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}
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function repl() {
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while (replCleanups.length > 0)
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replCleanups.pop()();
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var cmd;
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for (;;) {
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putstr("\n" + prompt);
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cmd = readline();
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if (cmd === null)
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return null;
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try {
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var result = runcmd(cmd);
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if (result === undefined)
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; // do nothing
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else if (Array.isArray(result))
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return result[0];
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else
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throw new Error("Internal error: result of runcmd wasn't array or undefined");
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} catch (exc) {
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print("*** Internal error: exception in the debugger code.");
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print(" " + exc);
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print(exc.stack);
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}
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}
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}
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var dbg = new Debugger();
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dbg.onDebuggerStatement = function (frame) {
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return saveExcursion(function () {
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topFrame = focusedFrame = frame;
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print("'debugger' statement hit.");
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showFrame();
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return repl();
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});
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};
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dbg.onThrow = function (frame, exc) {
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return saveExcursion(function () {
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topFrame = focusedFrame = frame;
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print("Unwinding due to exception. (Type 'c' to continue unwinding.)");
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showFrame();
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print("Exception value is:");
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showDebuggeeValue(exc);
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return repl();
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});
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};
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// The depth of jorendb nesting.
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var jorendbDepth;
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if (typeof jorendbDepth == 'undefined') jorendbDepth = 0;
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var debuggeeGlobal = newGlobal("new-compartment");
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debuggeeGlobal.jorendbDepth = jorendbDepth + 1;
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var debuggeeGlobalWrapper = dbg.addDebuggee(debuggeeGlobal);
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print("jorendb version -0.0");
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prompt = '(' + Array(jorendbDepth+1).join('meta-') + 'jorendb) ';
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var args = arguments;
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while(args.length > 0) {
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var arg = args.shift();
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if (arg == '-f') {
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arg = args.shift();
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debuggeeGlobal.evaluate(read(arg), { fileName: arg, lineNumber: 1 });
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} else if (arg == '-e') {
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arg = args.shift();
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debuggeeGlobal.eval(arg);
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} else {
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throw("jorendb does not implement command-line argument '" + arg + "'");
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}
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}
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repl();
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