From: Richard Dawe <rich AT phekda DOT freeserve DOT co DOT uk>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: __builtin_va_list bug?
Date: Sun, 20 Apr 2003 16:12:17 +0100
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

Hello.

Eric Sosman wrote:
> 
> Gisle Vanem wrote:
> >
> > I'm porting some code from Watcom to gcc/djgpp and encountered
> > tons of warnings on illegal use of va_arg(). So I cooked up a little
> > test:
> >
> > #include <stdarg.h>
> > char x;
> > void foo (va_list arg)
> 
>     Hold on; stop right there.  You've included <stdarg.h>, but you're
> using the argument list declaration from the pre-Standard <varargs.h>
> (or <vararg.h> with some compilers).  The two are not the same, they
> are not interchangeable, and they are *definitely* not miscible.
[snip]

Are you sure that's happening? What if some function calls foo like this:

void
myfunc (int someval, ...)
{
  va_list arg;

  va_start(arg, someval);
  foo(arg);
  va_end(arg);
}

I think this is legal according to the C99 standard. From section 7.15
"Variable arguments <stdarg.h>":

"The object ap may be passed as an argument to
another function; if that function invokes the va_arg macro with parameter ap,
the
value of ap in the calling function is indeterminate and shall be passed to
the va_end
macro prior to any further reference to ap."

ap is the va_list - i.e.: arg in the function myfunc above.

Regards,

-- 
Richard Dawe [ http://www.phekda.freeserve.co.uk/richdawe/ ]