https://gcc.gnu.org/bugzilla/show_bug.cgi?id=128587
Bug ID: 128587
Summary: Errant warning -Wmaybe-uninitialized at -O3 - but
shows proper initialization
Product: gcc
Version: 16.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: drankinatty at gmail dot com
Target Milestone: ---
This bug is filed as a separate bug per the request in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114592 (a similar bug affecting
C++ instead of C)
I see an errant warning in C gcc (SUSE Linux) 16.2.1 20260929 with basic
plane-old arrays and -O3, but frustratingly random. There is no warning at -O2.
The warning is actually a bit ironic, because it does a great job showing the
poa is initialized while warning it may not be with:
$ gcc -Wall -Wextra -pedantic -Wshadow -march=native -std=c23 -O3 -o ptrarrneur
ptrarrneur.c layers.c -lm
In function ‘err_total’,
inlined from ‘main’ at ptrarrneur.c:229:12:
ptrarrneur.c:130:19: warning: ‘target’ may be used uninitialized
[-Wmaybe-uninitialized]
130 | l->error[i] = erf (target[i], l->output[i], l->nneur);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
ptrarrneur.c: In function ‘main’:
ptrarrneur.c:199:9: note: ‘target’ declared here
199 | float target[] = { .05, .95 },
| ^~~~~~
The function and initialization involved:
float err_total (layer_t *l, float *target, float (*erf)(float, float,
unsigned))
{
float etotal = 0.;
for (unsigned i = 0; i < l->nneur; i++) {
l->error[i] = erf (target[i], l->output[i], l->nneur);
etotal += l->error[i];
}
return etotal;
}
int main (void) {
float target[] = { .05, .95 },
etotal = 0.;
/* compute total error */
etotal = err_total (&l[NLAYERS - 1], target, err_mse);
}
This likely is a related issue in optimization as in the cited C++ bug.
