Any news on this issue?
On Tuesday, December 11, 2012 at 11:06:05 AM UTC+2, Paul Harris wrote:
>
> Hello again,
>
> I have a new question, this has been causing my host app to crash
> regularly.
>
> I use the V8 engine in multiple threads concurrently using Isolates -
> works great.
>
> However, I often need to terminate a script early due to some change in
> the host app. The termination must come from another thread, obviously,
> because the JS thread is busy doing JS things.
>
> So, when I start a JS execution, I keep the handle of the Isolate in a
> mutex-protected variable that can be used from other threads.
> The mutex is locked during the Terminate call, and at the point of
> creating and Dispose()ing of the isolate, to prevent Terminate calls on an
> isolate that has been Disposed.
>
>
> So, in a separate thread, I call:
> V8::TerminateExecution(running_isolate);
>
>
> And that usually works well, UNLESS the script is currently in the middle
> of some of my C++ native functions.
>
> In which case, some very strange things happen, example:
> For the first half of the C++ function, everything works fine.
> For the second half, suddenly calls to eg handle->ToString() start to
> return empty handles. That is fine, I can handle that.
> But what I can't handle is when the C++ function in question is in the
> middle of building an Exception report,
>
> This is what I see when the debugger catches an OS::DebugBreak():
>
> static string GenerateExceptionReport( TryCatch const& try_catch )
> {
> HandleScope handle_scope;
> bool y = V8::IsExecutionTerminating(); // --> false
>
> String::Value exception(try_catch.Exception());
> bool x = V8::IsExecutionTerminating(); // --> TRUE
>
> Handle<v8::Message> message = try_catch.Message(); // --> returns
> empty handle
> if (message.IsEmpty())
> {
> // etc etc, not executed as message is empty
> }
>
> int start = message->GetStartColumn(); // --> CRASH
> int end = message->GetEndColumn();
>
>
>
> It crashes/aborts on this line:
>
> int Message::GetStartColumn() const {
> i::Isolate* isolate = Utils::OpenHandle(this)->GetIsolate();
> if (IsDeadCheck(isolate, "v8::Message::GetStartColumn()")) {
> return kNoColumnInfo;
> }
> ENTER_V8(isolate);
> i::HandleScope scope(isolate);
> i::Handle<i::JSObject> data_obj = Utils::OpenHandle(this);
> EXCEPTION_PREAMBLE(isolate); // <-------------- a test fails in here
>
>
> So, my question is, how SHOULD I be using TerminateExecution() ?
>
> My first thought is that I could use a mutex to ensure that I don't call
> Terminate during one of my C++ functions, but what about functions that I
> did not write myself ?
> And, I also need to test IsExecutionTerminating() at the start of all my
> functions, which would be annoying.
>
> I did try using a Locker with the Terminate, but because JS is busy
> running, it usually doesn't ever terminate early.
>
> I sense that I'm Doing It Wrong.
>
> What is the trick? Can anyone please tell me?
>
> thanks,
> Paul
>
>
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