va_arg regression from 2.95.2 to 3.1

[Nathan Sidwell]

"Joseph S. Myers" wrote:

> I think the argument is correct, and that this call to va_arg should be
> considered the same as a call where the types turn out to be incompatible
> at runtime (except here, the runtime type cannot be compatible).  It ought
> to be a mandatory warning (not pedwarn, not error); and should either be
> compiled into a call to abort() or be treated as a call to va_arg with the
> promoted type followed by conversion to the type specified.
I agree. IMO it is the same as something like
	if (c >= BITS_PER_INT)
		v = 0;
	else
		v = v >> c;
if 'c' is a constant, we'll warn on the 'v >> c', even though
control will never pass through there. We should handle the varargs
case in a similar manner

nathan

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