Re: [Chicken-users] SWIG and callbacks

[felix winkelmann]

On 3/3/07, Tony Sidaway <address@hidden> wrote:
> I'm trying to write a callback in Scheme.  The unusual thing about
> this callback is that it's intended to be invoked during the course of
> a Swig call.
>
> I know that our native FFI has foreign-lambda and foreign-safe-lambda,
> the latter intended for this kind of circumstance.  My question is:
> does Chicken Swig also permit this, or would I have to rewrite the
> swig code to make it safe for callbacks?
>
> Examining the Scheme code for "create-foreign-stub", which generates
> all foreign calls in the Chicken ffi, it seems that what needs to be
> done before a "safe"  or what was formerly known as a "callback" call,
> boils down to the following:
>
> * make 24 bytes more space for the result type
> * perform a minor garbage collection.
>
> I suppose I could add these to my swig-generated stubs and see what
> happens, but I thought I'd ask first in case somebody knows.

You also have to save the callback-continuation (see "generate-foreign-stubs"
in c-backend.scm). For the swig-specific information, you should contact
John Lenz (who wrote the swig backend).


cheers,
felix