https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81958
Bug ID: 81958
Summary: spurious -Wmaybe-uninitialized warning in gcc-8, or
with -O1
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: arnd at linaro dot org
Target Milestone: ---
building many random configurations of the linux kernel using a gcc-8.0.0
snapshot (20170821) found a couple of bugs with -Wmaybe-uninitialized, but also
added one warning for code that does not appear to have any uninitialized use,
reduced test case follows:
__attribute__ ((__cold__)) int printk();
struct lpfc_queue {
int queue_id;
struct lpfc_queue *hba_eq;
} *cq_phba;
void lpfc_debug_dump_all_queues(unsigned maxidx)
{
struct lpfc_queue *eq;
unsigned eqidx;
printk();
for (eqidx = 0; eqidx < maxidx; eqidx++) {
eq = &cq_phba->hba_eq[eqidx];
if (eq->queue_id)
break;
}
if (eqidx == maxidx)
eq = &cq_phba->hba_eq[0];
printk(eq);
}
$ x86_64-linux-gcc-8.0.0 -Wall -Werror=maybe-uninitialized -Werror -O2 -c
lpfc_debugfs.c
lpfc_debugfs-e-21.i: In function 'lpfc_debug_dump_all_queues':
lpfc_debugfs-e-21.i:22:10: error: 'eq' may be used uninitialized in this
function [-Werror=maybe-uninitialized]
printk(eq);
^~~~~~~~~~
Older versions warn for -O1 and -Os but not for -O2, while gcc-8.0.0 currently
warns for all optimization levels.
