v8::TryCatch should cancel the scheduled exception on Reset.

v8::TryCatch cancels the scheduled exception on destruction if |Rethrow|
was never called.
It is reasonable to do the same in |Reset|.

BUG=362388, 359386
LOG=
R=mstarzinger@chromium.org

Review URL: https://codereview.chromium.org/443853002

Patch from Yutaka Hirano <yhirano@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22963 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

include/v8.h

@@ -5114,7 +5114,8 @@ class V8_EXPORT TryCatch {
 
   /**
    * Clears any exceptions that may have been caught by this try/catch block.
-   * After this method has been called, HasCaught() will return false.
+   * After this method has been called, HasCaught() will return false. Cancels
+   * the scheduled exception if it is caught and ReThrow() is not called before.
    *
    * It is not necessary to clear a try/catch block before using it again; if
    * another exception is thrown the previously caught exception will just be
@@ -5157,6 +5158,8 @@ class V8_EXPORT TryCatch {
   }
 
  private:
+  void ResetInternal();
+
   // Make it hard to create heap-allocated TryCatch blocks.
   TryCatch(const TryCatch&);
   void operator=(const TryCatch&);

src/api.cc

@@ -1823,7 +1823,7 @@ v8::TryCatch::TryCatch()
       capture_message_(true),
       rethrow_(false),
       has_terminated_(false) {
-  Reset();
+  ResetInternal();
   // Special handling for simulators which have a separate JS stack.
   js_stack_comparable_address_ =
       reinterpret_cast<void*>(v8::internal::SimulatorStack::RegisterCTryCatch(
@@ -1935,6 +1935,17 @@ v8::Local<v8::Message> v8::TryCatch::Message() const {
 
 void v8::TryCatch::Reset() {
   DCHECK(isolate_ == i::Isolate::Current());
+  if (!rethrow_ && HasCaught() && isolate_->has_scheduled_exception()) {
+    // If an exception was caught but is still scheduled because no API call
+    // promoted it, then it is canceled to prevent it from being propagated.
+    // Note that this will not cancel termination exceptions.
+    isolate_->CancelScheduledExceptionFromTryCatch(this);
+  }
+  ResetInternal();
+}
+
+
+void v8::TryCatch::ResetInternal() {
   i::Object* the_hole = isolate_->heap()->the_hole_value();
   exception_ = the_hole;
   message_obj_ = the_hole;

test/cctest/test-api.cc

@@ -5421,6 +5421,31 @@ TEST(TryCatchNative) {
 }
 
 
+void TryCatchNativeResetHelper(
+    const v8::FunctionCallbackInfo<v8::Value>& args) {
+  ApiTestFuzzer::Fuzz();
+  v8::TryCatch try_catch;
+  args.GetIsolate()->ThrowException(v8_str("boom"));
+  CHECK(try_catch.HasCaught());
+  try_catch.Reset();
+  CHECK(!try_catch.HasCaught());
+}
+
+
+TEST(TryCatchNativeReset) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope scope(isolate);
+  v8::V8::Initialize();
+  v8::TryCatch try_catch;
+  Local<ObjectTemplate> templ = ObjectTemplate::New(isolate);
+  templ->Set(v8_str("TryCatchNativeResetHelper"),
+             v8::FunctionTemplate::New(isolate, TryCatchNativeResetHelper));
+  LocalContext context(0, templ);
+  CompileRun("TryCatchNativeResetHelper();");
+  CHECK(!try_catch.HasCaught());
+}
+
+
 THREADED_TEST(Equality) {
   LocalContext context;
   v8::Isolate* isolate = context->GetIsolate();