https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89723
Bug ID: 89723
Summary: Bogus maybe-uninitialized warning with -Og
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: bunk at stusta dot de
Target Milestone: ---
gcc seems to disable this warning when building without optimization, but it is
enabled with -Og:
$ cat test.c
typedef struct node234_Tag node234;
struct node234_Tag {
node234 *parent;
node234 *kids[4];
int counts[4];
};
int add234_internal(node234 *r, void *e, int index) {
node234 *n;
int ki;
if (r == 0) {
return 0;
}
n = r;
while (n) {
if (index <= n->counts[0]) {
ki = 0;
} else if (index -= n->counts[0] + 1, index <= n->counts[1]) {
ki = 1;
} else
return 0;
if (!n->kids[ki])
break;
n = n->kids[ki];
}
return ki;
}
$ gcc -c -O0 -Wall -Werror test.c
$ gcc -c -O1 -Wall -Werror test.c
$ gcc -c -Og -Wall -Werror test.c
test.c: In function ‘add234_internal’:
test.c:11:9: error: ‘ki’ may be used uninitialized in this function
[-Werror=maybe-uninitialized]
int ki;
^~
cc1: all warnings being treated as errors
$
Some upstream software builds with -Werror, which makes this a real problem
when building a whole distribution like Yocto with -Og for debugging purposes.
This can be reproduced on amd64 with all gcc versions supporting -Og from 4.8
to a recent gcc 9 snapshot.
