dom/bindings/Exceptions.cpp
author James Teh <jteh@mozilla.com>
Thu, 07 Mar 2019 18:10:13 +0000
changeset 520910 c26d4a8d43c4d0d6f6e13135b8f35924123fe99e
parent 518729 3538cdbdb9441fb764722113a42cfe7169ab2026
child 521903 d55401632cea92b6b2775ba278274b5490275876
permissions -rw-r--r--
Bug 1527922: Ensure the Reload button is disabled when testing against blank tabs in the browser toolbar key nav tests. r=Gijs For a blank tab, the Reload button should be disabled. These tests depend on this. This seems to be true when setting the new tab page to blank in Firefox Options. However, when we open about:blank with BrowserTestUtils.withNewTab, this is unreliable. That is, sometimes the Reload button is enabled, sometimes it isn't. I don't understand why this happens. For the purposes of these tests, just force the Reload button to be disabled for new, blank tabs so we get consistent results. Differential Revision: https://phabricator.services.mozilla.com/D22449

/* -*- 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/RootingAPI.h"
#include "js/TypeDecls.h"
#include "jsapi.h"
#include "js/SavedFrameAPI.h"
#include "xpcpublic.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,
                                      Exception* 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 "
             "CheckedUnwrapDynamic thing to make sense");

  // aCx's current Realm is where we're throwing, so using it in the
  // CheckedUnwrapDynamic check makes sense.
  if (js::CheckedUnwrapDynamic(exnObj, aCx)) {
    // 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, 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 = aException->GetResult();
      if (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();
  RefPtr<Exception> 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) {
    if (aRv == existingException->GetResult()) {
      // 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::GetCurrentJSContext();

  if (!cx || !js::GetContextRealm(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, std::move(captureMode));
}

namespace exceptions {

class JSStackFrame final : public nsIStackFrame, public xpc::JSStackFrameBase {
 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);

 private:
  virtual ~JSStackFrame();

  void Clear() override { mStack = nullptr; }

  // Remove this frame from the per-realm list of live frames,
  // and clear out the stack pointer.
  void UnregisterAndClear();

  JS::Heap<JSObject*> mStack;
  nsString mFormattedStack;

  nsCOMPtr<nsIStackFrame> mCaller;
  nsCOMPtr<nsIStackFrame> mAsyncCaller;
  nsString mFilename;
  nsString mFunname;
  nsString mAsyncCause;
  int32_t mSourceId;
  int32_t mLineno;
  int32_t mColNo;

  bool mFilenameInitialized;
  bool mFunnameInitialized;
  bool mSourceIdInitialized;
  bool mLinenoInitialized;
  bool mColNoInitialized;
  bool mAsyncCauseInitialized;
  bool mAsyncCallerInitialized;
  bool mCallerInitialized;
  bool mFormattedStackInitialized;
};

JSStackFrame::JSStackFrame(JS::Handle<JSObject*> aStack)
    : mStack(aStack),
      mSourceId(0),
      mLineno(0),
      mColNo(0),
      mFilenameInitialized(false),
      mFunnameInitialized(false),
      mSourceIdInitialized(false),
      mLinenoInitialized(false),
      mColNoInitialized(false),
      mAsyncCauseInitialized(false),
      mAsyncCallerInitialized(false),
      mCallerInitialized(false),
      mFormattedStackInitialized(false) {
  MOZ_ASSERT(mStack);
  MOZ_ASSERT(JS::IsUnwrappedSavedFrame(mStack));

  mozilla::HoldJSObjects(this);

  xpc::RegisterJSStackFrame(js::GetNonCCWObjectRealm(aStack), this);
}

JSStackFrame::~JSStackFrame() {
  UnregisterAndClear();
  mozilla::DropJSObjects(this);
}

void JSStackFrame::UnregisterAndClear() {
  if (!mStack) {
    return;
  }

  xpc::UnregisterJSStackFrame(js::GetNonCCWObjectRealm(mStack), this);
  Clear();
}

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->UnregisterAndClear();
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 determine the JSPrincipals* to pass to JS SavedFrame APIs.
//
// @argument aStack the stack we're working with; must be non-null.
// @argument [out] aCanCache whether we can use cached JSStackFrame values.
static JSPrincipals* GetPrincipalsForStackGetter(JSContext* aCx,
                                                 JS::Handle<JSObject*> aStack,
                                                 bool* aCanCache) {
  MOZ_ASSERT(JS::IsUnwrappedSavedFrame(aStack));

  JSPrincipals* currentPrincipals =
      JS::GetRealmPrincipals(js::GetContextRealm(aCx));
  JSPrincipals* stackPrincipals =
      JS::GetRealmPrincipals(js::GetNonCCWObjectRealm(aStack));

  // Fast path for when the principals are equal. This check is also necessary
  // for workers: no nsIPrincipal there so we can't use the code below.
  if (currentPrincipals == stackPrincipals) {
    *aCanCache = true;
    return stackPrincipals;
  }

  MOZ_ASSERT(NS_IsMainThread());

  if (nsJSPrincipals::get(currentPrincipals)
          ->Subsumes(nsJSPrincipals::get(stackPrincipals))) {
    // The current principals subsume the stack's principals. In this case use
    // the stack's principals: the idea is that this way devtools code that's
    // asking an exception object for a stack to display will end up with the
    // stack the web developer would see via doing .stack in a web page, with
    // Firefox implementation details excluded.

    // Because we use the stack's principals and don't rely on the current
    // context realm, we can use cached values.
    *aCanCache = true;
    return stackPrincipals;
  }

  // The stack was captured in more-privileged code, so use the less privileged
  // principals. Don't use cached values because we don't want these values to
  // depend on the current realm/principals.
  *aCanCache = false;
  return currentPrincipals;
}

// 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 property value depends
// on the (current) context's realm/principals.
//
// @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*, JSPrincipals*,
                                        JS::Handle<JSObject*>,
                                        GetterOutParamType,
                                        JS::SavedFrameSelfHosted),
    bool aIsCached, bool* aCanCache, bool* aUseCachedValue, ReturnType aValue) {
  MOZ_ASSERT(aStack);
  MOZ_ASSERT(JS::IsUnwrappedSavedFrame(aStack));

  JS::Rooted<JSObject*> stack(aCx, aStack);

  JSPrincipals* principals = GetPrincipalsForStackGetter(aCx, stack, aCanCache);
  if (*aCanCache && aIsCached) {
    *aUseCachedValue = true;
    return;
  }

  *aUseCachedValue = false;

  aPropGetter(aCx, principals, stack, aValue,
              JS::SavedFrameSelfHosted::Exclude);
}

NS_IMETHODIMP JSStackFrame::GetFilenameXPCOM(JSContext* aCx,
                                             nsAString& aFilename) {
  GetFilename(aCx, aFilename);
  return NS_OK;
}

void JSStackFrame::GetFilename(JSContext* aCx, nsAString& aFilename) {
  if (!mStack) {
    aFilename.Truncate();
    return;
  }

  JS::Rooted<JSString*> filename(aCx);
  bool canCache = false, useCachedValue = false;
  GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameSource,
                      mFilenameInitialized, &canCache, &useCachedValue,
                      &filename);
  if (useCachedValue) {
    aFilename = mFilename;
    return;
  }

  nsAutoJSString str;
  if (!str.init(aCx, filename)) {
    JS_ClearPendingException(aCx);
    aFilename.Truncate();
    return;
  }
  aFilename = str;

  if (canCache) {
    mFilename = str;
    mFilenameInitialized = true;
  }
}

NS_IMETHODIMP
JSStackFrame::GetNameXPCOM(JSContext* aCx, nsAString& aFunction) {
  GetName(aCx, aFunction);
  return NS_OK;
}

void JSStackFrame::GetName(JSContext* aCx, nsAString& aFunction) {
  if (!mStack) {
    aFunction.Truncate();
    return;
  }

  JS::Rooted<JSString*> name(aCx);
  bool canCache = false, useCachedValue = false;
  GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameFunctionDisplayName,
                      mFunnameInitialized, &canCache, &useCachedValue, &name);

  if (useCachedValue) {
    aFunction = mFunname;
    return;
  }

  if (name) {
    nsAutoJSString str;
    if (!str.init(aCx, name)) {
      JS_ClearPendingException(aCx);
      aFunction.Truncate();
      return;
    }
    aFunction = str;
  } else {
    aFunction.SetIsVoid(true);
  }

  if (canCache) {
    mFunname = aFunction;
    mFunnameInitialized = true;
  }
}

int32_t JSStackFrame::GetSourceId(JSContext* aCx) {
  if (!mStack) {
    return 0;
  }

  uint32_t id;
  bool canCache = false, useCachedValue = false;
  GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameSourceId, mSourceIdInitialized,
                      &canCache, &useCachedValue, &id);

  if (useCachedValue) {
    return mSourceId;
  }

  if (canCache) {
    mSourceId = id;
    mSourceIdInitialized = true;
  }

  return id;
}

NS_IMETHODIMP
JSStackFrame::GetSourceIdXPCOM(JSContext* aCx, int32_t* aSourceId) {
  *aSourceId = GetSourceId(aCx);
  return NS_OK;
}

int32_t JSStackFrame::GetLineNumber(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::GetLineNumberXPCOM(JSContext* aCx, int32_t* aLineNumber) {
  *aLineNumber = GetLineNumber(aCx);
  return NS_OK;
}

int32_t JSStackFrame::GetColumnNumber(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::GetColumnNumberXPCOM(JSContext* aCx, int32_t* aColumnNumber) {
  *aColumnNumber = GetColumnNumber(aCx);
  return NS_OK;
}

NS_IMETHODIMP JSStackFrame::GetSourceLine(nsACString& aSourceLine) {
  aSourceLine.Truncate();
  return NS_OK;
}

NS_IMETHODIMP
JSStackFrame::GetAsyncCauseXPCOM(JSContext* aCx, nsAString& aAsyncCause) {
  GetAsyncCause(aCx, aAsyncCause);
  return NS_OK;
}

void JSStackFrame::GetAsyncCause(JSContext* aCx, nsAString& aAsyncCause) {
  if (!mStack) {
    aAsyncCause.Truncate();
    return;
  }

  JS::Rooted<JSString*> asyncCause(aCx);
  bool canCache = false, useCachedValue = false;
  GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameAsyncCause,
                      mAsyncCauseInitialized, &canCache, &useCachedValue,
                      &asyncCause);

  if (useCachedValue) {
    aAsyncCause = mAsyncCause;
    return;
  }

  if (asyncCause) {
    nsAutoJSString str;
    if (!str.init(aCx, asyncCause)) {
      JS_ClearPendingException(aCx);
      aAsyncCause.Truncate();
      return;
    }
    aAsyncCause = str;
  } else {
    aAsyncCause.SetIsVoid(true);
  }

  if (canCache) {
    mAsyncCause = aAsyncCause;
    mAsyncCauseInitialized = true;
  }
}

NS_IMETHODIMP
JSStackFrame::GetAsyncCallerXPCOM(JSContext* aCx,
                                  nsIStackFrame** aAsyncCaller) {
  *aAsyncCaller = GetAsyncCaller(aCx).take();
  return NS_OK;
}

already_AddRefed<nsIStackFrame> JSStackFrame::GetAsyncCaller(JSContext* aCx) {
  if (!mStack) {
    return nullptr;
  }

  JS::Rooted<JSObject*> asyncCallerObj(aCx);
  bool canCache = false, useCachedValue = false;
  GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameAsyncParent,
                      mAsyncCallerInitialized, &canCache, &useCachedValue,
                      &asyncCallerObj);

  if (useCachedValue) {
    nsCOMPtr<nsIStackFrame> asyncCaller = mAsyncCaller;
    return asyncCaller.forget();
  }

  nsCOMPtr<nsIStackFrame> asyncCaller =
      asyncCallerObj ? new JSStackFrame(asyncCallerObj) : nullptr;

  if (canCache) {
    mAsyncCaller = asyncCaller;
    mAsyncCallerInitialized = true;
  }

  return asyncCaller.forget();
}

NS_IMETHODIMP
JSStackFrame::GetCallerXPCOM(JSContext* aCx, nsIStackFrame** aCaller) {
  *aCaller = GetCaller(aCx).take();
  return NS_OK;
}

already_AddRefed<nsIStackFrame> JSStackFrame::GetCaller(JSContext* aCx) {
  if (!mStack) {
    return nullptr;
  }

  JS::Rooted<JSObject*> callerObj(aCx);
  bool canCache = false, useCachedValue = false;
  GetValueIfNotCached(aCx, mStack, JS::GetSavedFrameParent, mCallerInitialized,
                      &canCache, &useCachedValue, &callerObj);

  if (useCachedValue) {
    nsCOMPtr<nsIStackFrame> caller = mCaller;
    return caller.forget();
  }

  nsCOMPtr<nsIStackFrame> caller =
      callerObj ? new JSStackFrame(callerObj) : nullptr;

  if (canCache) {
    mCaller = caller;
    mCallerInitialized = true;
  }

  return caller.forget();
}

NS_IMETHODIMP
JSStackFrame::GetFormattedStackXPCOM(JSContext* aCx, nsAString& aStack) {
  GetFormattedStack(aCx, aStack);
  return NS_OK;
}

void JSStackFrame::GetFormattedStack(JSContext* aCx, nsAString& aStack) {
  if (!mStack) {
    aStack.Truncate();
    return;
  }

  // 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.

  JS::Rooted<JSObject*> stack(aCx, mStack);

  bool canCache;
  JSPrincipals* principals = GetPrincipalsForStackGetter(aCx, stack, &canCache);
  if (canCache && mFormattedStackInitialized) {
    aStack = mFormattedStack;
    return;
  }

  JS::Rooted<JSString*> formattedStack(aCx);
  if (!JS::BuildStackString(aCx, principals, stack, &formattedStack)) {
    JS_ClearPendingException(aCx);
    aStack.Truncate();
    return;
  }

  nsAutoJSString str;
  if (!str.init(aCx, formattedStack)) {
    JS_ClearPendingException(aCx);
    aStack.Truncate();
    return;
  }

  aStack = str;

  if (canCache) {
    mFormattedStack = str;
    mFormattedStackInitialized = true;
  }
}

NS_IMETHODIMP JSStackFrame::GetNativeSavedFrame(
    JS::MutableHandle<JS::Value> aSavedFrame) {
  aSavedFrame.setObjectOrNull(mStack);
  return NS_OK;
}

NS_IMETHODIMP
JSStackFrame::ToStringXPCOM(JSContext* aCx, nsACString& _retval) {
  ToString(aCx, _retval);
  return NS_OK;
}

void JSStackFrame::ToString(JSContext* aCx, nsACString& _retval) {
  _retval.Truncate();

  nsString filename;
  GetFilename(aCx, filename);

  if (filename.IsEmpty()) {
    filename.AssignLiteral("<unknown filename>");
  }

  nsString funname;
  GetName(aCx, funname);

  if (funname.IsEmpty()) {
    funname.AssignLiteral("<TOP_LEVEL>");
  }

  int32_t lineno = GetLineNumber(aCx);

  static const char format[] = "JS frame :: %s :: %s :: line %d";
  _retval.AppendPrintf(format, NS_ConvertUTF16toUTF8(filename).get(),
                       NS_ConvertUTF16toUTF8(funname).get(), lineno);
}

already_AddRefed<nsIStackFrame> CreateStack(JSContext* aCx,
                                            JS::StackCapture&& aCaptureMode) {
  JS::Rooted<JSObject*> stack(aCx);
  if (!JS::CaptureCurrentStack(aCx, &stack, std::move(aCaptureMode))) {
    return nullptr;
  }

  if (!stack) {
    return nullptr;
  }

  nsCOMPtr<nsIStackFrame> frame = new JSStackFrame(stack);
  return frame.forget();
}

}  // namespace exceptions
}  // namespace dom
}  // namespace mozilla