[cffi-devel] Next release of CFFI with cffi-libffi

[Liam Healy]

On Thu, Apr 19, 2012 at 9:50 AM, Stelian Ionescu <sionescu at cddr.org> wrote:

> On Thu, 2012-04-19 at 14:37 +0100, Luís Oliveira wrote:
> > On Thu, Apr 19, 2012 at 11:34 AM, Stelian Ionescu <sionescu at cddr.org>
> wrote:
> > > IMO the change to mem-aref is bad and will break a lot of code. Until
> > > now the contract of mem-aref was that it received a pointer to an array
> > > of the referenced type and returned a pointer offset into the array.
> > > The fact that it now returns a list is a gratuitous change, with no
> > > utility. If we actually want these semantics(not sure about it), it
> > > should be mem-aptr to implement them
> >
> > If it's not too difficult, can you extract a self-contained test case
> > that has been broken?
>
> (defcstruct timespec (sec :int64) (usec :int64))
>
> (with-foreign-object (p '(:struct timespec) 2)
>  (mem-aref p '(:struct timespec) 1))
>
> In order not to break existing code, I think that mem-aref should
> continue to return a pointer in this case instead of a plist. That would
> allow cffi-using code to work as it is and not have to be rewritten(an
> example that was brought to my attention is
> https://gitorious.org/commonqt/commonqt/blobs/master/info.lisp#line312).
>
> Since both functionalities will continue to be present in CFFI, it's
> better not to force users to review their code to decide, for each use
> of mem-aref, whether it needs to be converted to mem-aptr or not.
>
> --
> Stelian Ionescu a.k.a. fe[nl]ix
> Quidquid latine dictum sit, altum videtur.
> http://common-lisp.net/project/iolib
>
>
As Luis pointed out, no code should be broken because '(:struct foo) wasn't
used before.  The example you point to has a symbol representing the
type '|struct MethodMap| which I guess is being interpreted as if it
were'(:struct MethodMap).  I'm not sure, but that's the only way I can see
this not being interpreted as a bare structure.  If it were interpreted as
a bare structure, everything should work as before.

Liam
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