* Luís Oliveira <luis...@gmail.com> <cab-hnlqje9y0+kyq3-cojck-gd3mzooe+h2f+7upkdkcgu9...@mail.gmail.com> Wrote on Wed, 15 Jul 2020 14:50:27 +0100
> On Wed, 15 Jul 2020 at 06:16, Madhu <enom...@meer.net> wrote: >> one of the cffi/TODO items has >> -> Handle va_list. For now it's treated as any other argument. >> >> Maybe someone has thought deeply about how to do this? Please let me >> know if you have any suggestions. >> >> [It seems borodust/claw tries to handle this by converting va_list >> args to variadic lisp arguments - but it still seems to blow up at a >> cffi:parse-type. Or maybe it is a defect with my Clang-7.0 stdarg >> vs. what is included with gcc] > The TODO item should probably be removed. DEFCFUN has syntax for > varargs and that's implemented on top of FOREIGN-FUNCALL-VARARGS and > FOREIGN-FUNCALL-VARARGS-POINTER. The implementation so far is simple, > it only takes care of promoting floats to doubles, and chars/short to > ints. The test suite tracks whether this works and it seems to work so > far. The TODO entry was about specifically va_list. Now I'm not sure how the "new" stdargs API can be manipulated through CFFI - AFAIK it is purely a C compiler thing - you cannot foreign funcall to va_start and va_copy. The only way I could use it is through lisp implementations that support a form of c-inline, or through "grovelled" code which would be loaded through a shared library. > Not sure about what c2ffi needs to do, though. In order to "treat va_list as any other argument" I tried adding an opaque (cffi:defcstruct (:builtin-va-list :size 192)) -- 192 being sizeof(va_list) with x86_64-pc-linux-gnu-gcc -- having %json-type-to-cffi-type return that when it comes across a cffi tag "__builtin_va_list". cffi/c2ffi can generate defcfns for functions which use va_list in the signature. I think the user would still be hardpressed to find a way to use them. Unless I'm missing something... ??
