On Tue, Aug 16, 2011 at 08:18:48PM +0400, Dmitry Bely wrote:
> On Tue, Aug 16, 2011 at 8:10 PM, Richard W.M. Jones <[email protected]> wrote:
>
> > Well it would certainly help if we had a piece of runnable code to
> > look at. The code supplied in the original email contains an infinite
> > loop.
>
> Yes, that was my mistake that I corrected later. The loop should be
>
> for (; *s != NULL; s++) {
> list = wrp_ml_cons(caml_copy_string(*s), list); /* bug! */
> }
Well, contrary to what I said earlier, it really does seem
like this is undefined C behaviour.
Try the attached program, which distills the problem down to something
simple. gcc with -O0 and -O2 produces completely different answers,
and the assembler output confirms it.
Rich.
--
Richard Jones
Red Hat
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#include <stdio.h>
#include <stdlib.h>
void f (int a, int b);
int g (void);
int *global = NULL;
int
main (void)
{
int x = 1;
global = &x;
f (g (), x);
exit (0);
}
void
f (int a, int b)
{
printf ("a = %d, b = %d\n", a, b);
}
int
g (void)
{
if (global) {
global++;
return *global;
}
else
return 42;
}
