hxcpp: null function pointer when using __unsafe_get/__unsafe_set

[Michael Baczynski]

Hi,

I just stumbled upon this code, which throws an exception when targeting cpp:

class Foo<T> {

    private var data:Array<T>;

    public function new(size:Int) {

        data = new Array<T>();

        for (i in 0...size) data[i] = null; //allocate to prevent crash

        untyped data.__unsafe_get(0); //Error : Null Function Pointer

    }

}

I can avoid this problem by implementing haxe.rtti.Generic so is this a bug or normal behavior?

best,

Michael

[Hugh]

Hi,

Yes, an array of <T> becomes an Array<Dynamic>, and Array<Dynamic> becomes Dynamic, so data is "Dynamic".  So this is the problem.

Consider that you would need completely different implementations for Array<Bool> and Array<SomeObject>, since the  "sizeof element" would be different.

Generic (dynamic) code is never going to be fast, so the "unsafe" option is not going to save anything.

If you knew that you were only dealing with objects, not Bool/Int/etc, then you may be able to use some @:functionCode to inject a static_cast, but you would have to really really want to.

Hugh

[Michael Baczynski]

Thanks Hugh, this is what I have expected. I'm just playing around with generic code + unsafe access and results are astonishing (20-25x faster!).