[Pyrex] how to declare and use variable length argument lists

[Greg Ewing]

Victor Ng wrote:

> On 2/3/05, *Parzival Herzog* < parzp at shaw.ca <mailto:parzp at shaw.ca>> wrote:
> 
>     Pyrex accepts C variable length argument list syntax, e.g .
> 
>     cdef object _tuple(char *fmt, ...):
>         return ()
> 
>     but what can I tell pyrex to cover the macros va_list, va_start,
>     va_end, and va_arg from stdarg.h?

Pyrex currently supports the varargs declaration syntax so
that you can call externally-defined varargs functions from
Pyrex code, but there isn't yet any support for writing
functions in Pyrex that accept varargs. That's one of the
things on my ever-growing todo list.

You can probably get most of the way with something like

   cdef extern from "stdarg.h":
     ctypedef void *va_list
     void va_start(va_list ap, void *last)
     void va_end(va_list ap)

Then you would probably have to deal with the various
argument types you want to use individually, e.g.

   cdef extern from "myargs.h":
     int va_int(va_list ap)
     char *va_charptr(va_list ap)

etc, where myargs.h looks like

   #define va_int(ap) va_arg(ap, int)
   #define va_charptr(ap) va_arg(ap, char *)

Warning: I haven't tested any of this. Use it at your
own risk.

-- 
Greg Ewing, Computer Science Dept, +--------------------------------------+
University of Canterbury,	   | Carpe post meridiam!          	  |
Christchurch, New Zealand	   | (I'm not a morning person.)          |
greg.ewing at canterbury.ac.nz	   +--------------------------------------+