Re: libffi GCC vs. end user development

[Anthony Green <green at redhat dot com>]

David Ayers wrote:
> Hello folks,
>
> Anthony Green mentioned that libffi as shipped with GCC is currently for
> use in gcj.  The GNU ObjC runtime which also comes with GCC could also
> use libffi to implement it's forwarding which currently based on
> builtin_apply.  Currently this is hardly used as far as I'm aware.
> GNUstep for example builds on top of libffi (or ffcall for older
> platforms and architectures that libffi doesn't support).
>
> I've been on and off on looking at how ObjC forwarding could be
> implemented with libffi by libobjc which would enable some long standing
> PR's to be fixed.  The first candidate would be to use the version that
> currently already resides in GCC to avoid an external dependency.
>
> So my questions are:
> 1) What exactly is the relation between GCC's libffi and gcj?
>   
I merge patches between the two so they are roughly equivalent.  Most of 
the deltas relate to configuration/build changes.

> 2) Is GCC's libffi only needed for the compiler or also for libjava
> runtime?
>   
It's only used for the runtime, so please go ahead and use GCC's libffi 
for ObjC.

> 3) Has it been modified in a way that it can only be useful for gcj?
>   
No. 
> 4) If it is used by the runtime, would you expect issues if it was also
> used by the libobjc runtime and a third party ObjC Programm/Library also
> used the stock libffi?
>   
No, I don't think there would be any problems.  We link libffi 
statically into libgcj and recommend that you do the same.

Anthony Green

> Thank you for your time.
> Cheers,
> David Ayers
>
>
>