Problem Accessing C++ Object From AngelScript

Hello,

I have a line in AngleScript:

WeakHandle weakGridHandle = gridworld.GetGrid(gridworld.RealToGrid(node.position));
	currentGrid = weakGridHandle.Get();

The function GetGrid returns a WeakPtr.

However whenever these lines are run, i get an assert error in ReCounted::AddRef() on the c++ side.

Both gridWorld and grid objects are registered in c++:

RegisterObject<GridWorld>(engine, "GridWorld");
RegisterObject<Grid>(engine, "Grid");

And the registration for the function that causes the issue:

engine->RegisterObjectMethod(“GridWorld”, “Grid& GetGrid(Vector3 globalPos)”, asMETHODPR(GridWorld, GetGrid, (Vector3), WeakPtr<Grid>), asCALL_THISCALL);

Grid is directly derived from Object.

Any Ideas of what i could be missing?

Thanks, Trevor

I see that you are lying here

Grid& GetGrid(Vector3 globalPos)
GetGrid, (Vector3), WeakPtr

What’s actual GetGrid signature?

Sorry did not notice the signature got messed up when I pasted in:

Here is the full signature for GetGrid:

engine->RegisterObjectMethod(“GridWorld”, “Grid& GetGrid(Vector3 globalPos)”, asMETHODPR(GridWorld, GetGrid, (Vector3), WeakPtr<Grid>), asCALL_THISCALL);

Updating Original Post.

Signature of AngelScript function should match the signature of C++ function. If you tell AS that Grid& is returned, Grid& shall be returned.
You probably cannot expose template things to AS including WeakPtr<Grid> (I may be wrong here), so you should return something like Grid* in both C++ and AS signatures. Urho usually use wrappes to not disturb public interface.

You could also try to use WeakHandle return value in AS signature, but it’s a bit hacky.

The problem seems to be with AngleScript attempting to delete the GridWorld Object after the following call in the API:

static SharedPtr<GridWorld> GetGridWorld()
{
return SharedPtr<GridWorld>(GetScriptContext()->GetSubsystem<GridWorld>());
}

On the C++ side, 1 new GridWorld is created and registered as a subsystem in the global context.
A SharedPtr to the GridWorld also exists as a member in my Application class just to make sure I don’t run out of references.

I put a break point in the destructor of GridWorld and that is never called. However I keep getting crashes in ReleaseRef()

I’ve not used AngleScript before, however that does look odd the way it’s written. If GridWorld is already created as a Subsystem singleton, couldn’t you do something like:

SharedPtr<GridWorld> GetGridWorld() { 
        return GetScriptContext()->GetSubsystem<GridWorld>();
}

Again, I’ve not used AngleScript, but your return statement looks like you’re creating a new object that deletes itself once it’s outside of the scope of the function.

Does casting a pointer to a shared pointer result in a new object? I thought perhaps that cast would simply temporarily increase the reference of the GridWorld Itself.

If I do what you suggest - I get a compiler error because there is no implicit conversion from raw pointer to SharedPtr.

I did try simply this:

static GridWorld* GetGridWorld()
{
return GetScriptContext()->GetSubsystem<GridWorld>();
}

Which interestingly now does result in the GridWorld destructor being invoked. which of course still crashes…

There must be a way to keep Angel-script from taking control of singleton subsystems like this.

Again the AngelScript code:

WeakHandle weakGridHandle = gridworld;

Results in the crash.

If you have a problem with AngelScript, always share both C++ signature and binding code, it really helps.
Keep in mind that AngelScrpt has no signature validation in any form (except simple syntax errors). So, incorrect signature usually lead to crash during function call.

In my Application::Start():

RegisterGridWorldAPI(GetSubsystem()->GetScriptEngine());
context_->RegisterSubsystem(new GridWorld(scene_, cache, camera, cameraPivot, 4, context_));

In my GridWorldAPI.cpp:

void RegisterGridWorldAPI(asIScriptEngine* engine)
{
RegisterGridWorld(engine);
}

static void RegisterGridWorld(asIScriptEngine* engine)
{
RegisterObject(engine, “GridWorld”);

engine->RegisterGlobalFunction(“GridWorld@ get_gridworld()”, asFUNCTION(GetGridWorld), asCALL_CDECL);
}

static GridWorld* GetGridWorld()
{
return GetScriptContext()->GetSubsystem<GridWorld>();
}

Edited

Try GridWorld@+ get_gridworld()

Thanks Eugene, this worked. Also adding @+ to the member method signatures worked for the GetGrid functions.

Closing

I recommend you to read a bit about AS bindings, they are quite sophisticated sometimes.
The main usage of @ references is to give new object to AS (you should AddRef here)
I suggest to always use @+ references because they behave as native pointers in bindings.