x86 64 bit function argument bug?

[Falk Hueffner]

Stephen Biggs <xyzzy@hotpop.com> writes:

> On Sun, 2003-05-04 at 11:54, Falk Hueffner wrote:
> > Stephen Biggs <xyzzy@hotpop.com> writes:
> > > I want to take an address of an argument and dereference it to
> > > access the value that is passed to a function on the stack.
> > 
> > That should work just fine. If it doesn't, it's a bug.
> 
> Ah, now we understand each other.  I am saying that the x86 behavior
> for 64 bit value arguments is a bug.

Maybe you can provide a test case without undefined behaviour that
shows this?

#include <stdio.h>
void f(unsigned long long *p) {
    printf("%llx\n", *p);
}
void g(unsigned long long x) {
    f(&x);
}
int main(void) {
    g(0x1122334455667788ULL);
}

works for me.

> > > Basically I am trying to do varargs/stdarg without using varargs or
> > > any built-in functions.
> > 
> > That is impossible to do portably.
> 
> Granted.  I would be satisfied with it working in GCC, and it does on
> the x86 except for 64 bit values.

I'm pretty sure that is still impossible, unless you also restrict
yourself to the x86 architecture.

-- 
	Falk