path: root/js/src/vm/ErrorObject.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * 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 "vm/ErrorObject-inl.h"

#include "mozilla/Range.h"

#include "jsexn.h"

#include "js/CallArgs.h"
#include "js/CharacterEncoding.h"
#include "vm/GlobalObject.h"
#include "vm/String.h"

#include "jsobjinlines.h"

#include "vm/NativeObject-inl.h"
#include "vm/SavedStacks-inl.h"
#include "vm/Shape-inl.h"

using namespace js;

/* static */ Shape*
js::ErrorObject::assignInitialShape(ExclusiveContext* cx, Handle<ErrorObject*> obj)
{
    MOZ_ASSERT(obj->empty());

    if (!obj->addDataProperty(cx, cx->names().fileName, FILENAME_SLOT, 0))
        return nullptr;
    if (!obj->addDataProperty(cx, cx->names().lineNumber, LINENUMBER_SLOT, 0))
        return nullptr;
    return obj->addDataProperty(cx, cx->names().columnNumber, COLUMNNUMBER_SLOT, 0);
}

/* static */ bool
js::ErrorObject::init(JSContext* cx, Handle<ErrorObject*> obj, JSExnType type,
                      ScopedJSFreePtr<JSErrorReport>* errorReport, HandleString fileName,
                      HandleObject stack, uint32_t lineNumber, uint32_t columnNumber,
                      HandleString message)
{
    AssertObjectIsSavedFrameOrWrapper(cx, stack);
    assertSameCompartment(cx, obj, stack);

    // Null out early in case of error, for exn_finalize's sake.
    obj->initReservedSlot(ERROR_REPORT_SLOT, PrivateValue(nullptr));

    if (!EmptyShape::ensureInitialCustomShape<ErrorObject>(cx, obj))
        return false;

    // The .message property isn't part of the initial shape because it's
    // present in some error objects -- |Error.prototype|, |new Error("f")|,
    // |new Error("")| -- but not in others -- |new Error(undefined)|,
    // |new Error()|.
    RootedShape messageShape(cx);
    if (message) {
        messageShape = obj->addDataProperty(cx, cx->names().message, MESSAGE_SLOT, 0);
        if (!messageShape)
            return false;
        MOZ_ASSERT(messageShape->slot() == MESSAGE_SLOT);
    }

    MOZ_ASSERT(obj->lookupPure(NameToId(cx->names().fileName))->slot() == FILENAME_SLOT);
    MOZ_ASSERT(obj->lookupPure(NameToId(cx->names().lineNumber))->slot() == LINENUMBER_SLOT);
    MOZ_ASSERT(obj->lookupPure(NameToId(cx->names().columnNumber))->slot() ==
               COLUMNNUMBER_SLOT);
    MOZ_ASSERT_IF(message,
                  obj->lookupPure(NameToId(cx->names().message))->slot() == MESSAGE_SLOT);

    MOZ_ASSERT(JSEXN_ERR <= type && type < JSEXN_LIMIT);

    JSErrorReport* report = errorReport ? errorReport->forget() : nullptr;
    obj->initReservedSlot(EXNTYPE_SLOT, Int32Value(type));
    obj->initReservedSlot(STACK_SLOT, ObjectOrNullValue(stack));
    obj->setReservedSlot(ERROR_REPORT_SLOT, PrivateValue(report));
    obj->initReservedSlot(FILENAME_SLOT, StringValue(fileName));
    obj->initReservedSlot(LINENUMBER_SLOT, Int32Value(lineNumber));
    obj->initReservedSlot(COLUMNNUMBER_SLOT, Int32Value(columnNumber));
    if (message)
        obj->setSlotWithType(cx, messageShape, StringValue(message));

    return true;
}

/* static */ ErrorObject*
js::ErrorObject::create(JSContext* cx, JSExnType errorType, HandleObject stack,
                        HandleString fileName, uint32_t lineNumber, uint32_t columnNumber,
                        ScopedJSFreePtr<JSErrorReport>* report, HandleString message,
                        HandleObject protoArg /* = nullptr */)
{
    AssertObjectIsSavedFrameOrWrapper(cx, stack);

    RootedObject proto(cx, protoArg);
    if (!proto) {
        proto = GlobalObject::getOrCreateCustomErrorPrototype(cx, cx->global(), errorType);
        if (!proto)
            return nullptr;
    }

    Rooted<ErrorObject*> errObject(cx);
    {
        const Class* clasp = ErrorObject::classForType(errorType);
        JSObject* obj = NewObjectWithGivenProto(cx, clasp, proto);
        if (!obj)
            return nullptr;
        errObject = &obj->as<ErrorObject>();
    }

    if (!ErrorObject::init(cx, errObject, errorType, report, fileName, stack,
                           lineNumber, columnNumber, message))
    {
        return nullptr;
    }

    return errObject;
}

JSErrorReport*
js::ErrorObject::getOrCreateErrorReport(JSContext* cx)
{
    if (JSErrorReport* r = getErrorReport())
        return r;

    // We build an error report on the stack and then use CopyErrorReport to do
    // the nitty-gritty malloc stuff.
    JSErrorReport report;

    // Type.
    JSExnType type_ = type();
    report.exnType = type_;

    // Filename.
    JSAutoByteString filenameStr;
    if (!filenameStr.encodeLatin1(cx, fileName(cx)))
        return nullptr;
    report.filename = filenameStr.ptr();

    // Coordinates.
    report.lineno = lineNumber();
    report.column = columnNumber();

    // Message. Note that |new Error()| will result in an undefined |message|
    // slot, so we need to explicitly substitute the empty string in that case.
    RootedString message(cx, getMessage());
    if (!message)
        message = cx->runtime()->emptyString;
    if (!message->ensureFlat(cx))
        return nullptr;

    UniquePtr<char[], JS::FreePolicy> utf8 = StringToNewUTF8CharsZ(cx, *message);
    if (!utf8)
        return nullptr;
    report.initOwnedMessage(utf8.release());

    // Cache and return.
    JSErrorReport* copy = CopyErrorReport(cx, &report);
    if (!copy)
        return nullptr;
    setReservedSlot(ERROR_REPORT_SLOT, PrivateValue(copy));
    return copy;
}

static bool
FindErrorInstanceOrPrototype(JSContext* cx, HandleObject obj, MutableHandleObject result)
{
    // Walk up the prototype chain until we find an error object instance or
    // prototype object. This allows code like:
    //  Object.create(Error.prototype).stack
    // or
    //   function NYI() { }
    //   NYI.prototype = new Error;
    //   (new NYI).stack
    // to continue returning stacks that are useless, but at least don't throw.

    RootedObject target(cx, CheckedUnwrap(obj));
    if (!target) {
        JS_ReportErrorASCII(cx, "Permission denied to access object");
        return false;
    }

    RootedObject proto(cx);
    while (!IsErrorProtoKey(StandardProtoKeyOrNull(target))) {
        if (!GetPrototype(cx, target, &proto))
            return false;

        if (!proto) {
            // We walked the whole prototype chain and did not find an Error
            // object.
            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_INCOMPATIBLE_PROTO,
                                      js_Error_str, "(get stack)", obj->getClass()->name);
            return false;
        }

        target = CheckedUnwrap(proto);
        if (!target) {
            JS_ReportErrorASCII(cx, "Permission denied to access object");
            return false;
        }
    }

    result.set(target);
    return true;
}


static MOZ_ALWAYS_INLINE bool
IsObject(HandleValue v)
{
    return v.isObject();
}

/* static */ bool
js::ErrorObject::getStack(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);
    // We accept any object here, because of poor-man's subclassing of Error.
    return CallNonGenericMethod<IsObject, getStack_impl>(cx, args);
}

/* static */ bool
js::ErrorObject::getStack_impl(JSContext* cx, const CallArgs& args)
{
    RootedObject thisObj(cx, &args.thisv().toObject());

    RootedObject obj(cx);
    if (!FindErrorInstanceOrPrototype(cx, thisObj, &obj))
        return false;

    if (!obj->is<ErrorObject>()) {
        args.rval().setString(cx->runtime()->emptyString);
        return true;
    }

    RootedObject savedFrameObj(cx, obj->as<ErrorObject>().stack());
    RootedString stackString(cx);
    if (!BuildStackString(cx, savedFrameObj, &stackString))
        return false;

    if (cx->stackFormat() == js::StackFormat::V8) {
        // When emulating V8 stack frames, we also need to prepend the
        // stringified Error to the stack string.
        HandlePropertyName name = cx->names().ErrorToStringWithTrailingNewline;
        RootedValue val(cx);
        if (!GlobalObject::getSelfHostedFunction(cx, cx->global(), name, name, 0, &val))
            return false;

        RootedValue rval(cx);
        if (!js::Call(cx, val, args.thisv(), &rval))
            return false;

        if (!rval.isString())
            return false;

        RootedString stringified(cx, rval.toString());
        stackString = ConcatStrings<CanGC>(cx, stringified, stackString);
    }

    args.rval().setString(stackString);
    return true;
}

/* static */ bool
js::ErrorObject::setStack(JSContext* cx, unsigned argc, Value* vp)
{
    CallArgs args = CallArgsFromVp(argc, vp);
    // We accept any object here, because of poor-man's subclassing of Error.
    return CallNonGenericMethod<IsObject, setStack_impl>(cx, args);
}

/* static */ bool
js::ErrorObject::setStack_impl(JSContext* cx, const CallArgs& args)
{
    RootedObject thisObj(cx, &args.thisv().toObject());

    if (!args.requireAtLeast(cx, "(set stack)", 1))
        return false;
    RootedValue val(cx, args[0]);

    return DefineProperty(cx, thisObj, cx->names().stack, val);
}