[Mono-list] passing and returning structs in native calls

[Robert Jordan]

On 07.01.2011 16:19, Edd Barrett wrote:
> Why is this? Myself and a colleague have spent a number of hours trying
> to work this out.

Because returning structs by value from functions is problematic
in general. Try to stay away from such signatures if you want
portability.

> Changing the function to return the integer within the struct instead of
> the struct itself works as expected, but that is not really what I want.
>
> I am using an amd64 machine on OpenBSD (which uses fastcall by default,
> is this the issue? I know microsoft mono does not support fastcall.
> Having said that, openbsd has working packages of gtk#, for example.)

GTK avoids returning structs by value.

>
> Or perhaps this is a mono bug... I'm completely stuck at this point.

Maybe. IIRC, Mono on amd64 doesn't handle correctly structs of
sizeof < 8 as return values.

Robert