Re: va_arg *, and why not.

[Franz Sirl <Franz dot Sirl-kernel at lauterbach dot com>]

At 16:14 17.07.00, Kaveh R. Ghazi wrote:
>  > From: Mark Mitchell <mark@codesourcery.com>
>  >
>  > >>>>> "Gabriel" == Gabriel Dos Reis <gdr@codesourcery.com> writes:
>  >
>  >     Gabriel> Hmm, I'm confused there.  I was under the impression that
>  >     Gabriel> it was taking the address of a va_list function argument
>  >     Gabriel> that was not portable.  Furthermore, in his proposed
>  >     Gabriel> resolution using va_copy was one option.
>  >
>  > But with the caveat that there be a libiberty/system.h equivalent to
>  > handle systems that do not define va_copy.
>
>
>FYI, system.h already defines a backup va_copy.  I don't know if it's
>*correct*, but it does exist.  You may wish to verify it DTRT.

No, it is not correct in system.h. It should look like this:

#ifdef HAVE_VA_LIST_AS_ARRAY
#define va_copy(d,s)  (*(d) = *(s))
#else
#define va_copy(d,s)  ((d) = (s))
#endif

This is the autoconf test that mozilla uses:

dnl Does this platform require array notation to assign to a va_list?
dnl If cross-compiling, we assume va_list is "normal".  If this breaks
dnl you, set ac_cv_valistisarray=true and maybe define HAVE_VA_LIST_AS_ARRAY
dnl also just to be sure.
AC_MSG_CHECKING(whether va_list assignments need array notation)
AC_CACHE_VAL(ac_cv_valistisarray,
         [AC_TRY_RUN([#include <stdlib.h>
                      #include <stdarg.h>
                      void foo(int i, ...) {
                         va_list ap1, ap2;
                         va_start(ap1, i);
                         ap2 = ap1;
                         if (va_arg(ap2, int) != 123 || va_arg(ap1, int) != 
123) { exit(1); }
                         va_end(ap1); va_end(ap2);
                      }
                      int main() { foo(0, 123); return(0); }],
                     [ac_cv_valistisarray=false],
                     [ac_cv_valistisarray=true],
                     [ac_cv_valistisarray=false])])

if test "$ac_cv_valistisarray" = true ; then
         AC_DEFINE(HAVE_VA_LIST_AS_ARRAY)
         AC_MSG_RESULT(yes)
else
         AC_MSG_RESULT(no)
fi

Franz.