gecko-dev/dom/bindings/Exceptions.cpp

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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 "mozilla/dom/Exceptions.h"
#include "js/GCAPI.h"
#include "js/TypeDecls.h"
#include "jsapi.h"
#include "jsprf.h"
#include "mozilla/CycleCollectedJSContext.h"
#include "mozilla/dom/BindingUtils.h"
#include "mozilla/dom/DOMException.h"
#include "mozilla/dom/ScriptSettings.h"
#include "nsPIDOMWindow.h"
#include "nsServiceManagerUtils.h"
#include "nsThreadUtils.h"
#include "XPCWrapper.h"
#include "WorkerPrivate.h"
#include "nsContentUtils.h"
namespace mozilla {
namespace dom {
// Throw the given exception value if it's safe. If it's not safe, then
// synthesize and throw a new exception value for NS_ERROR_UNEXPECTED. The
// incoming value must be in the compartment of aCx. This function guarantees
// that an exception is pending on aCx when it returns.
static void
ThrowExceptionValueIfSafe(JSContext* aCx, JS::Handle<JS::Value> exnVal,
nsIException* aOriginalException)
{
MOZ_ASSERT(aOriginalException);
if (!exnVal.isObject()) {
JS_SetPendingException(aCx, exnVal);
return;
}
JS::Rooted<JSObject*> exnObj(aCx, &exnVal.toObject());
MOZ_ASSERT(js::IsObjectInContextCompartment(exnObj, aCx),
"exnObj needs to be in the right compartment for the "
"CheckedUnwrap thing to make sense");
if (js::CheckedUnwrap(exnObj)) {
// This is an object we're allowed to work with, so just go ahead and throw
// it.
JS_SetPendingException(aCx, exnVal);
return;
}
// We could probably Throw(aCx, NS_ERROR_UNEXPECTED) here, and it would do the
// right thing due to there not being an existing exception on the runtime at
// this point, but it's clearer to explicitly do the thing we want done. This
// is also why we don't just call ThrowExceptionObject on the Exception we
// create: it would do the right thing, but that fact is not obvious.
RefPtr<Exception> syntheticException =
CreateException(NS_ERROR_UNEXPECTED);
JS::Rooted<JS::Value> syntheticVal(aCx);
if (!GetOrCreateDOMReflector(aCx, syntheticException, &syntheticVal)) {
return;
}
MOZ_ASSERT(syntheticVal.isObject() &&
!js::IsWrapper(&syntheticVal.toObject()),
"Must have a reflector here, not a wrapper");
JS_SetPendingException(aCx, syntheticVal);
}
void
ThrowExceptionObject(JSContext* aCx, nsIException* aException)
{
// See if we really have an Exception.
nsCOMPtr<Exception> exception = do_QueryInterface(aException);
if (exception) {
ThrowExceptionObject(aCx, exception);
return;
}
// We only have an nsIException (probably an XPCWrappedJS). Fall back on old
// wrapping.
MOZ_ASSERT(NS_IsMainThread());
JS::Rooted<JS::Value> val(aCx);
if (!WrapObject(aCx, aException, &NS_GET_IID(nsIException), &val)) {
return;
}
ThrowExceptionValueIfSafe(aCx, val, aException);
}
void
ThrowExceptionObject(JSContext* aCx, Exception* aException)
{
JS::Rooted<JS::Value> thrown(aCx);
// If we stored the original thrown JS value in the exception
// (see XPCConvert::ConstructException) and we are in a web context
// (i.e., not chrome), rethrow the original value. This only applies to JS
// implemented components so we only need to check for this on the main
// thread.
if (NS_IsMainThread() && !nsContentUtils::IsCallerChrome() &&
aException->StealJSVal(thrown.address())) {
// Now check for the case when thrown is a number which matches
// aException->GetResult(). This would indicate that what actually got
// thrown was an nsresult value. In that situation, we should go back
// through dom::Throw with that nsresult value, because it will make sure to
// create the right sort of Exception or DOMException, with the right
// global.
if (thrown.isNumber()) {
nsresult exceptionResult;
if (NS_SUCCEEDED(aException->GetResult(&exceptionResult)) &&
double(exceptionResult) == thrown.toNumber()) {
Throw(aCx, exceptionResult);
return;
}
}
if (!JS_WrapValue(aCx, &thrown)) {
return;
}
ThrowExceptionValueIfSafe(aCx, thrown, aException);
return;
}
if (!GetOrCreateDOMReflector(aCx, aException, &thrown)) {
return;
}
ThrowExceptionValueIfSafe(aCx, thrown, aException);
}
bool
Throw(JSContext* aCx, nsresult aRv, const nsACString& aMessage)
{
if (aRv == NS_ERROR_UNCATCHABLE_EXCEPTION) {
// Nuke any existing exception on aCx, to make sure we're uncatchable.
JS_ClearPendingException(aCx);
return false;
}
if (JS_IsExceptionPending(aCx)) {
// Don't clobber the existing exception.
return false;
}
CycleCollectedJSContext* context = CycleCollectedJSContext::Get();
nsCOMPtr<nsIException> existingException = context->GetPendingException();
// Make sure to clear the pending exception now. Either we're going to reuse
// it (and we already grabbed it), or we plan to throw something else and this
// pending exception is no longer relevant.
context->SetPendingException(nullptr);
// Ignore the pending exception if we have a non-default message passed in.
if (aMessage.IsEmpty() && existingException) {
nsresult nr;
if (NS_SUCCEEDED(existingException->GetResult(&nr)) &&
aRv == nr) {
// Reuse the existing exception.
ThrowExceptionObject(aCx, existingException);
return false;
}
}
RefPtr<Exception> finalException = CreateException(aRv, aMessage);
MOZ_ASSERT(finalException);
ThrowExceptionObject(aCx, finalException);
return false;
}
void
ThrowAndReport(nsPIDOMWindowInner* aWindow, nsresult aRv)
{
MOZ_ASSERT(aRv != NS_ERROR_UNCATCHABLE_EXCEPTION,
"Doesn't make sense to report uncatchable exceptions!");
AutoJSAPI jsapi;
if (NS_WARN_IF(!jsapi.Init(aWindow))) {
return;
}
Throw(jsapi.cx(), aRv);
}
already_AddRefed<Exception>
CreateException(nsresult aRv, const nsACString& aMessage)
{
// Do we use DOM exceptions for this error code?
switch (NS_ERROR_GET_MODULE(aRv)) {
case NS_ERROR_MODULE_DOM:
case NS_ERROR_MODULE_SVG:
case NS_ERROR_MODULE_DOM_XPATH:
case NS_ERROR_MODULE_DOM_INDEXEDDB:
case NS_ERROR_MODULE_DOM_FILEHANDLE:
case NS_ERROR_MODULE_DOM_ANIM:
case NS_ERROR_MODULE_DOM_PUSH:
case NS_ERROR_MODULE_DOM_MEDIA:
if (aMessage.IsEmpty()) {
return DOMException::Create(aRv);
}
return DOMException::Create(aRv, aMessage);
default:
break;
}
// If not, use the default.
RefPtr<Exception> exception =
new Exception(aMessage, aRv, EmptyCString(), nullptr, nullptr);
return exception.forget();
}
already_AddRefed<nsIStackFrame>
GetCurrentJSStack(int32_t aMaxDepth)
{
// is there a current context available?
JSContext* cx = nsContentUtils::GetCurrentJSContextForThread();
if (!cx || !js::GetContextCompartment(cx)) {
return nullptr;
}
static const unsigned MAX_FRAMES = 100;
if (aMaxDepth < 0) {
aMaxDepth = MAX_FRAMES;
}
JS::StackCapture captureMode = aMaxDepth == 0
? JS::StackCapture(JS::AllFrames())
: JS::StackCapture(JS::MaxFrames(aMaxDepth));
return dom::exceptions::CreateStack(cx, mozilla::Move(captureMode));
}
namespace exceptions {
class JSStackFrame : public nsIStackFrame
{
public:
NS_DECL_CYCLE_COLLECTING_ISUPPORTS
NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_CLASS(JSStackFrame)
NS_DECL_NSISTACKFRAME
// aStack must not be null.
explicit JSStackFrame(JS::Handle<JSObject*> aStack);
protected:
int32_t GetLineno(JSContext* aCx);
int32_t GetColNo(JSContext* aCx);
private:
virtual ~JSStackFrame();
JS::Heap<JSObject*> mStack;
nsString mFormattedStack;
nsCOMPtr<nsIStackFrame> mCaller;
nsCOMPtr<nsIStackFrame> mAsyncCaller;
nsString mFilename;
nsString mFunname;
nsString mAsyncCause;
int32_t mLineno;
int32_t mColNo;
bool mFilenameInitialized;
bool mFunnameInitialized;
bool mLinenoInitialized;
bool mColNoInitialized;
bool mAsyncCauseInitialized;
bool mAsyncCallerInitialized;
bool mCallerInitialized;
bool mFormattedStackInitialized;
};
JSStackFrame::JSStackFrame(JS::Handle<JSObject*> aStack)
: mStack(aStack)
, mLineno(0)
, mColNo(0)
, mFilenameInitialized(false)
, mFunnameInitialized(false)
, mLinenoInitialized(false)
, mColNoInitialized(false)
, mAsyncCauseInitialized(false)
, mAsyncCallerInitialized(false)
, mCallerInitialized(false)
, mFormattedStackInitialized(false)
{
MOZ_ASSERT(mStack);
mozilla::HoldJSObjects(this);
}
JSStackFrame::~JSStackFrame()
{
mozilla::DropJSObjects(this);
}
NS_IMPL_CYCLE_COLLECTION_CLASS(JSStackFrame)
NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(JSStackFrame)
NS_IMPL_CYCLE_COLLECTION_UNLINK(mCaller)
NS_IMPL_CYCLE_COLLECTION_UNLINK(mAsyncCaller)
tmp->mStack = nullptr;
NS_IMPL_CYCLE_COLLECTION_UNLINK_END
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(JSStackFrame)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mCaller)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mAsyncCaller)
NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(JSStackFrame)
NS_IMPL_CYCLE_COLLECTION_TRACE_JS_MEMBER_CALLBACK(mStack)
NS_IMPL_CYCLE_COLLECTION_TRACE_END
NS_IMPL_CYCLE_COLLECTING_ADDREF(JSStackFrame)
NS_IMPL_CYCLE_COLLECTING_RELEASE(JSStackFrame)
NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(JSStackFrame)
NS_INTERFACE_MAP_ENTRY(nsIStackFrame)
NS_INTERFACE_MAP_ENTRY(nsISupports)
NS_INTERFACE_MAP_END
// Helper method to get the value of a stack property, if it's not already
// cached. This will make sure we skip the cache if the access is happening
// over Xrays.
//
// @argument aStack the stack we're working with; must be non-null.
// @argument aPropGetter the getter function to call.
// @argument aIsCached whether we've cached this property's value before.
//
// @argument [out] aCanCache whether the value can get cached.
// @argument [out] aUseCachedValue if true, just use the cached value.
// @argument [out] aValue the value we got from the stack.
template<typename ReturnType, typename GetterOutParamType>
static void
GetValueIfNotCached(JSContext* aCx, const JS::Heap<JSObject*>& aStack,
JS::SavedFrameResult (*aPropGetter)(JSContext*,
JS::Handle<JSObject*>,
GetterOutParamType,
JS::SavedFrameSelfHosted),
bool aIsCached, bool* aCanCache, bool* aUseCachedValue,
ReturnType aValue)
{
MOZ_ASSERT(aStack);
JS::Rooted<JSObject*> stack(aCx, aStack);
// Allow caching if aCx and stack are same-compartment. Otherwise take the
// slow path.
*aCanCache = js::GetContextCompartment(aCx) == js::GetObjectCompartment(stack);
if (*aCanCache && aIsCached) {
*aUseCachedValue = true;
return;
}
*aUseCachedValue = false;
aPropGetter(aCx, stack, aValue, JS::SavedFrameSelfHosted::Exclude);
}
NS_IMETHODIMP JSStackFrame::GetFilename(JSContext* aCx, nsAString& aFilename)
{
if (!mStack) {
aFilename.Truncate();
return NS_OK;
}
JS::Rooted<JSString*> filename(aCx);
bool canCache = false, useCachedValue = false;
GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameSource,
mFilenameInitialized,
&canCache, &useCachedValue, &filename);
if (useCachedValue) {
aFilename = mFilename;
return NS_OK;
}
nsAutoJSString str;
if (!str.init(aCx, filename)) {
JS_ClearPendingException(aCx);
aFilename.Truncate();
return NS_OK;
}
aFilename = str;
if (canCache) {
mFilename = str;
mFilenameInitialized = true;
}
return NS_OK;
}
NS_IMETHODIMP JSStackFrame::GetName(JSContext* aCx, nsAString& aFunction)
{
if (!mStack) {
aFunction.Truncate();
return NS_OK;
}
JS::Rooted<JSString*> name(aCx);
bool canCache = false, useCachedValue = false;
GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameFunctionDisplayName,
mFunnameInitialized, &canCache, &useCachedValue,
&name);
if (useCachedValue) {
aFunction = mFunname;
return NS_OK;
}
if (name) {
nsAutoJSString str;
if (!str.init(aCx, name)) {
JS_ClearPendingException(aCx);
aFunction.Truncate();
return NS_OK;
}
aFunction = str;
} else {
aFunction.SetIsVoid(true);
}
if (canCache) {
mFunname = aFunction;
mFunnameInitialized = true;
}
return NS_OK;
}
int32_t
JSStackFrame::GetLineno(JSContext* aCx)
{
if (!mStack) {
return 0;
}
uint32_t line;
bool canCache = false, useCachedValue = false;
GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameLine, mLinenoInitialized,
&canCache, &useCachedValue, &line);
if (useCachedValue) {
return mLineno;
}
if (canCache) {
mLineno = line;
mLinenoInitialized = true;
}
return line;
}
NS_IMETHODIMP JSStackFrame::GetLineNumber(JSContext* aCx, int32_t* aLineNumber)
{
*aLineNumber = GetLineno(aCx);
return NS_OK;
}
int32_t
JSStackFrame::GetColNo(JSContext* aCx)
{
if (!mStack) {
return 0;
}
uint32_t col;
bool canCache = false, useCachedValue = false;
GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameColumn, mColNoInitialized,
&canCache, &useCachedValue, &col);
if (useCachedValue) {
return mColNo;
}
if (canCache) {
mColNo = col;
mColNoInitialized = true;
}
return col;
}
NS_IMETHODIMP JSStackFrame::GetColumnNumber(JSContext* aCx,
int32_t* aColumnNumber)
{
*aColumnNumber = GetColNo(aCx);
return NS_OK;
}
NS_IMETHODIMP JSStackFrame::GetSourceLine(nsACString& aSourceLine)
{
aSourceLine.Truncate();
return NS_OK;
}
NS_IMETHODIMP JSStackFrame::GetAsyncCause(JSContext* aCx,
nsAString& aAsyncCause)
{
if (!mStack) {
aAsyncCause.Truncate();
return NS_OK;
}
JS::Rooted<JSString*> asyncCause(aCx);
bool canCache = false, useCachedValue = false;
GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameAsyncCause,
mAsyncCauseInitialized, &canCache, &useCachedValue,
&asyncCause);
if (useCachedValue) {
aAsyncCause = mAsyncCause;
return NS_OK;
}
if (asyncCause) {
nsAutoJSString str;
if (!str.init(aCx, asyncCause)) {
JS_ClearPendingException(aCx);
aAsyncCause.Truncate();
return NS_OK;
}
aAsyncCause = str;
} else {
aAsyncCause.SetIsVoid(true);
}
if (canCache) {
mAsyncCause = aAsyncCause;
mAsyncCauseInitialized = true;
}
return NS_OK;
}
NS_IMETHODIMP JSStackFrame::GetAsyncCaller(JSContext* aCx,
nsIStackFrame** aAsyncCaller)
{
if (!mStack) {
*aAsyncCaller = nullptr;
return NS_OK;
}
JS::Rooted<JSObject*> asyncCallerObj(aCx);
bool canCache = false, useCachedValue = false;
GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameAsyncParent,
mAsyncCallerInitialized, &canCache, &useCachedValue,
&asyncCallerObj);
if (useCachedValue) {
NS_IF_ADDREF(*aAsyncCaller = mAsyncCaller);
return NS_OK;
}
nsCOMPtr<nsIStackFrame> asyncCaller =
asyncCallerObj ? new JSStackFrame(asyncCallerObj) : nullptr;
asyncCaller.forget(aAsyncCaller);
if (canCache) {
mAsyncCaller = *aAsyncCaller;
mAsyncCallerInitialized = true;
}
return NS_OK;
}
NS_IMETHODIMP JSStackFrame::GetCaller(JSContext* aCx, nsIStackFrame** aCaller)
{
if (!mStack) {
*aCaller = nullptr;
return NS_OK;
}
JS::Rooted<JSObject*> callerObj(aCx);
bool canCache = false, useCachedValue = false;
GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameParent, mCallerInitialized,
&canCache, &useCachedValue, &callerObj);
if (useCachedValue) {
NS_IF_ADDREF(*aCaller = mCaller);
return NS_OK;
}
nsCOMPtr<nsIStackFrame> caller =
callerObj ? new JSStackFrame(callerObj) : nullptr;
caller.forget(aCaller);
if (canCache) {
mCaller = *aCaller;
mCallerInitialized = true;
}
return NS_OK;
}
NS_IMETHODIMP JSStackFrame::GetFormattedStack(JSContext* aCx, nsAString& aStack)
{
if (!mStack) {
aStack.Truncate();
return NS_OK;
}
// Sadly we can't use GetValueIfNotCached here, because our getter
// returns bool, not JS::SavedFrameResult. Maybe it's possible to
// make the templates more complicated to deal, but in the meantime
// let's just inline GetValueIfNotCached here.
// Allow caching if aCx and stack are same-compartment. Otherwise take the
// slow path.
bool canCache =
js::GetContextCompartment(aCx) == js::GetObjectCompartment(mStack);
if (canCache && mFormattedStackInitialized) {
aStack = mFormattedStack;
return NS_OK;
}
JS::Rooted<JSObject*> stack(aCx, mStack);
JS::Rooted<JSString*> formattedStack(aCx);
if (!JS::BuildStackString(aCx, stack, &formattedStack)) {
JS_ClearPendingException(aCx);
aStack.Truncate();
return NS_OK;
}
nsAutoJSString str;
if (!str.init(aCx, formattedStack)) {
JS_ClearPendingException(aCx);
aStack.Truncate();
return NS_OK;
}
aStack = str;
if (canCache) {
mFormattedStack = str;
mFormattedStackInitialized = true;
}
return NS_OK;
}
NS_IMETHODIMP JSStackFrame::GetNativeSavedFrame(JS::MutableHandle<JS::Value> aSavedFrame)
{
aSavedFrame.setObjectOrNull(mStack);
return NS_OK;
}
NS_IMETHODIMP JSStackFrame::ToString(JSContext* aCx, nsACString& _retval)
{
_retval.Truncate();
nsString filename;
nsresult rv = GetFilename(aCx, filename);
NS_ENSURE_SUCCESS(rv, rv);
if (filename.IsEmpty()) {
filename.AssignLiteral("<unknown filename>");
}
nsString funname;
rv = GetName(aCx, funname);
NS_ENSURE_SUCCESS(rv, rv);
if (funname.IsEmpty()) {
funname.AssignLiteral("<TOP_LEVEL>");
}
int32_t lineno = GetLineno(aCx);
static const char format[] = "JS frame :: %s :: %s :: line %d";
_retval.AppendPrintf(format,
NS_ConvertUTF16toUTF8(filename).get(),
NS_ConvertUTF16toUTF8(funname).get(),
lineno);
return NS_OK;
}
already_AddRefed<nsIStackFrame>
CreateStack(JSContext* aCx, JS::StackCapture&& aCaptureMode)
{
JS::Rooted<JSObject*> stack(aCx);
if (!JS::CaptureCurrentStack(aCx, &stack, mozilla::Move(aCaptureMode))) {
return nullptr;
}
if (!stack) {
return nullptr;
}
nsCOMPtr<nsIStackFrame> frame = new JSStackFrame(stack);
return frame.forget();
}
} // namespace exceptions
} // namespace dom
} // namespace mozilla