Prevent exception in constructor of GValueArray

[lafoletc]

Add check with null pointer
Due to method Structure.validate(), an exception was raised when JNA try to invoke constructor of GValueArray with "new Pointer(0)"

[neilcsmith-net]

Thanks. But why should we protect against this? Is there a particular concern you're trying to address?

Also, JNA already has Pointer.NULL and/or Pointer.nativeValue(Pointer p)

[lafoletc]

I have tried to use interface Decodebin.AUTOPLUG_FACTORIES and JNA instanciate a default result using a Pointer(0), that raise an exception

[neilcsmith-net]

That sounds like our problem not JNA. More likely the type mapper needs updating to handle null (Pointer.NULL) results?

[lafoletc]

In case of function, JNA try to create a default instance of the result to check the callback.
As GValueArray is a Structure, CallbackReference.getNativeType(cls) invoke Structure.validate(cls) which instanciates a new instance of GValueArray with Pointer(0) as argument to verify if JNA will be able to convert the C result in Java object.

[lafoletc]

"type mapper" can not help us : it is use to convert object between Java and C.
Here, we are in full Java
See method Structure.validate() => Structure.newInstance(cls, PLACEHOLDER_MEMORY)

[neilcsmith-net]

Ah, OK, thanks. Missed the context of where this was coming from. Confused by the fact that we're registering this class in our type mapper - that needs looking at, but it's nothing to do with this then. Couple that with the fact I'd misread from the JavaDoc that Pointer.NULL was new Pointer(0) when it's just null. Sorry, I failed all around on this one! 😞

I'll pull this in ASAP.