Fatal error while attempting to enter context

[Zinglish]

Hi guys

I have an issue when attempting to embed a very simple V8 flow into my application. Basically I have a wrapper class that holds a global Isolate (Which I will use everywhere) and also holds the context (Since I want all events to share any global variables). When I try entering the context I create in my wrapper class in main, I get this error:

#
# Fatal error in ../src/api.h, line 402
# CHECK(that == __null || !(*reinterpret_cast<v8::internal::Context**>( const_cast<v8::Context*>(that)))->IsFailure()) failed
#
==== C stack trace ===============================
 1: V8_Fatal
 2: v8::Utils::OpenHandle(v8::Context const*, bool)
 3: v8::Context::Enter()
 4: init(int, char**)
 5: ??
 6: ??
 7: ??

Here's my wrapper class (JSEngine.cpp):

JSEngine::Engine()

{

printf("Script | DEBUG | Constructing engine\n");

V8::Initialize();

this->isolate = Isolate::GetCurrent();

HandleScope scope(this->isolate);

this->context = Context::New(this->isolate);

Persistent<Context> persistent_context(this->isolate, this->context);

printf("Script | DEBUG | Done constructing engine, context: %lu\n", this->context);

}

 All I wanted this to do is initalize the V8 engine and create a single Isolate and Context.

Here's my Init (Which throws the error shown in the first quote block when it hits the second line):

HandleScope handleScope(Server::asEngine->isolate);

printf("Set scope to isolate\n");

Server::asEngine->context->Enter();

printf("Set scope to context\n");

Handle<String> source = String::NewFromUtf8(Server::asEngine->isolate, "var test = 5;");

Handle<Script> script = Script::Compile(source);

Handle<Value> result = script->Run();

I feel like I am doing something really dumb that it doesn't work as I expect. All I essentially did was attempt to split up the most basic example into a class so I could grasp the concept and idea of embedding V8.

Thank you ahead of time if you do post a reply. 

[Ben Noordhuis]

I suspect that you need to change this->context from Local<Context> or
Handle<Context> to a Persistent<Context>. You can rematerialize the
handle in your Init() function with `Local<Context> context =
Local<Context>::New(this->isolate, this->context)`.

By the way, you can use `Context::Scope context_scope(context)`
instead of manually entering and exiting the context. The
Context::Scope destructor will automatically exit the context when the
context_scope variable goes out of scope.

[Terence-Lee Davis]

Hey Ben

Thanks a lot for the reply to the topic!

I went back to my code and made the appropriate changes but still no change to the error I get. Also, for some reason the compiler errors out when I attempt to adjust this->context to type "v8::Persistent<v8::Context>" with:

error: no match for ‘operator=’ in ‘((ASEngine::Engine*)this)->ASEngine::Engine::context = v8::Context::New(((ASEngine::Engine*)this)->ASEngine::Engine::isolate, 0u, v8::Handle<v8::ObjectTemplate>(), v8::Handle<v8::Value>())’

If it helps I am using V8 version 3.22 (I checked out to this version from master because I had a feeling master had a few issues).

I did however adjust my class to look like this now:

ASEngine::Engine::Engine()

{

printf("eScript | DEBUG | Constructing engine\n");

V8::Initialize();

this->isolate = Isolate::GetCurrent();

HandleScope scope(this->isolate);

this->context = Context::New(this->isolate);

Persistent<Context> persistent_context(this->isolate, this->context);

printf("Script | DEBUG | Done constructing engine\n");

}

v8::Local<v8::Context> ASEngine::Engine::GetContext()

{

return Local<Context>::New(this->isolate, this->context);

}

As I adjusted the class above, I adjusted the code in Init() to:

Server::asEngine = new ASEngine::Engine();

HandleScope handleScope(Server::asEngine->isolate);

Context::Scope scope(Server::asEngine->GetContext());

Handle<String> source2 = String::NewFromUtf8(Server::asEngine->isolate, "test;");

Handle<Script> script2 = Script::Compile(source2);

Handle<Value> result2 = script2->Run();

I still get the exact same error.

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[Ben Noordhuis]

That's because the Context object is still wrapped in a Local and that
Local gets zeroed when the HandleScope it was created in goes out of
scope. Turn it into a Persistent<Context>, assign it with
this->context.Reset(isolate, context) and all should be well.

[Terence-Lee Davis]

Ahhhh thanks so much Ben, you're bloody awesome! Problem solved.

Thanks again.