http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55513
--- Comment #6 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-11-28
15:51:21 UTC ---
Reduced testcase:
void
f1 ()
{
char s[10];
const int t = __builtin_snprintf (s, 10, "Hello");
__builtin_printf ("%d %s\n", t, s);
}
void
f2 ()
{
char s[10];
const int t = (__builtin_memcpy (s, "Hello", 6), 5);
__builtin_printf ("%d %s\n", t, s);
}
int
main ()
{
f1 ();
f2 ();
}
Even f2 fails to call memcpy, so it isn't related to folding the snprintf into
what it folds to, but about handling COMPOUND_EXPRs with side-effects on the
LHS where the only side-effects are builtin calls. If the LHS of the
COMPOUND_EXPR is a non-builtin, potential_rvalue_constant_expression returns
false and it is handled correctly, but even if it is say __builtin_exit (0) or
similar, it is optimized away.
