https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128469
Bug ID: 128469
Summary: wrong code at -O1: modref drops a store in a nested
function that exits by non-local goto since r12-5126
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Keywords: wrong-code
Severity: normal
Priority: P3
Component: ipa
Assignee: unassigned at gcc dot gnu.org
Reporter: jeffchen006 at gmail dot com
Target Milestone: ---
Target: x86_64-pc-linux-gnu
int printf(const char *, ...);
void test(int *p)
{
{
__label__ out;
void nf(void) { *p = 0; goto out; }
nf();
out:;
}
}
int main(void)
{
int i = 1;
test(&i);
printf("%d\n", i);
return 0;
}
$ gcc -O0 t.c && ./a.out
0
$ gcc -O1 t.c && ./a.out
1
-O1, -O2, -O3 all fail.
Expected: 0. nf stores 0 through p and then jumps to out, so i is 0.
modref marks nf "looping pure" because its only exit is the non-local goto, and
the store is dropped.
Avoided by: -fno-ipa-modref, -fno-ipa-pure-const.
Bisected to r12-5126-g992644c3511.
Correct on 8.5.0, 10.5.0.
Wrong on 12.5.0, 13.4.0, 14.3.0, 15.2.0, 16.2.0, trunk.
-O0 -fsanitize=undefined,address is clean.
gcc version 17.0.0 20261029 (experimental), r17-5747-g85867b0c935,
x86_64-pc-linux-gnu
Configured with: --enable-languages=c,c++ --disable-multilib
--disable-bootstrap --enable-checking=release
