[generator] Incorrectly generated code inside Trampolines.g.cs

[spouliot]

Looking into the generated Trampolines.g.cs files we can spot some code patterns that looks like:

return NSArray.FromNSObjects(retval).Handle;

This is incorrect as the GC can dispose of the managed NSArray before the Handle is used again.

If unlucky (the window of opportunity is small but exist) that can dealloc the native NSArray before the Handle is used again.

See also: #10146

[rolfbjarne]

One potential solution would be to retain/autorelease the return value:

var retobj = NSArray.FromNSObjects(retval);
retobj.DangerousRetain ();
retobj.DangerousAutorelease ();
return retobj.Handle;

[spouliot]

That's simpler than what I had in mind [0] but I'd be worried about a tight-loop calling that trampoline.

[0] ideally we would avoid a managed NSArray to be created since we're returning an handle anyway