Segmentation fault while trying to wrap an object

[Andre Oliveira]

I am trying to embed a C++ program to v8, and after trying to follow the official embedder's guide and some other old (ancient, I'd say) guides all over the web, I came to the following program:

void testing()
{   // Initialize V8.
  V8::InitializeICU();
  Platform* platform = platform::CreateDefaultPlatform();
  V8::InitializePlatform(platform);
  V8::Initialize();
 
  // Create a new Isolate and make it the current one.
  Isolate* isolate = Isolate::New();
  {
    Isolate::Scope isolate_scope(isolate);

    // Create a stack-allocated handle scope.
    HandleScope handle_scope(isolate);
    scripthelper* sh = new scripthelper();

    // Create a new context with a global template
    Handle<ObjectTemplate> global = ObjectTemplate::New(isolate);
   
    Local<ObjectTemplate> design_templ = ObjectTemplate::New(isolate);
    design_templ->SetInternalFieldCount(1);
    Rsyn::Design* d = new Rsyn::Design();

    //this line causes a segmentation fault:
    Local<Object> obj = design_templ->NewInstance();
   
    obj->SetInternalField(0, External::New(isolate, d));    
    global->Set(String::NewFromUtf8(isolate, "Design"), FunctionTemplate::New(isolate, designConstructor));  
    global->Set(String::NewFromUtf8(isolate, "print"), FunctionTemplate::New(isolate, jsprint));    
    Local<Context> context = Context::New(isolate, NULL, global);
       
    // Enter the context for compiling and running the hello world script.
    Context::Scope context_scope(context);    
   
    // Create a string containing the JavaScript source code.
    Local<String> source = String::NewFromUtf8(isolate, sh->getSourceFromFile("/home/andreoliv/uplace2/project/src/script/test.js").c_str());
   
    // Compile the source code.
    Local<Script> script = Script::Compile(source);
   
    //run script
    script->Run();

    // Run the desired function
    Handle<Value> args[2];
    sh->addStringToArguments("HAHA ", args, 0);
    sh->addNumberToArguments(5.0, args, 1);    
    Handle<Value> result = sh->callJSFunction(context->Global(), "JSrepeat", args, 2);          
    // Convert the result to an UTF8 string and print it.
    String::Utf8Value utf8(result);
    printf("result: %s\n", *utf8);
   
    sh->callJSFunction(context->Global(), "useCppFunc", args, 2);
}


    Local<Object> obj = design_templ->NewInstance();

This line causes a segmentation fault that I could not fix.
Can someone explain what's going on?
While I'm on topic, is there any good and working guides on embedding? All guides I come across are either shallow or won't work anymore because of updates.