GCC-2.96: va_arg is ignored when its result is not used

[Gaël Quéri <gael at baoule dot dyndns dot org>]

In current gcc snapshots when the return value of va_arg is not used the
instruction is ignored and the va_list stays pointing the same arg.

I have included an example: in previous versions gcc returned 'arg2',
which is not the case anymore; moreover if the (void) is removed and the
compilation is made with -Wall gcc says that this statement has no effect.

This breaks at last glib, and certainly some more v*printf
implementations.

I don't know if these kind of things are allowed by the ISO standard, and
this could be easily fixed in the source by adding a temporary variable to
hold the result of va_arg, so this isn't a very grave problem, but there
is always a little source incompatibility.

I saw this problem on gcc-2.96 since 199909xx to 19991004 on ix86
architecture.

	Good luck, gael
#include <stdarg.h>
#include <stdio.h>

void test (char *fmt, ...)
{
	va_list args;

	va_start (args, fmt);

	(void) va_arg (args, char *);
	puts (va_arg (args, char *));
}

int main ()
{
	test ("%s %s", "arg1", "arg2");

	return 0;
}