https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109789
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It also seems to depend on array-to-pointer decay from float[nframes] to float*
across the function boundary, because if the loop using the size_t index is
moved into the same function as the array initialization, the analyzer doesn't
complain.
In any case, the value of size_t size should be assumed to positive.
Further reduced:
void sink(float);
void dsp_abs_max(float *buf, unsigned size) {
sink(buf[size - 1]);
}
void export_audio(int nframes, float init, int count) {
do {
float tmp_l[nframes];
for (int i = 0; i < nframes; i++)
tmp_l[i] = init;
dsp_abs_max(tmp_l, nframes);
} while (--count);
}
$ gcc -fanalyzer -Werror=analyzer-use-of-uninitialized-value -c a.c
a.c: In function ‘dsp_abs_max’:
a.c:4:3: error: use of uninitialized value ‘*buf_7(D) + _3’ [CWE-457]
[-Werror=analyzer-use-of-uninitialized-value]
4 | sink(buf[size - 1]);
| ^~~~~~~~~~~~~~~~~~~
‘export_audio’: events 1-5
|
| 6 | void export_audio(int nframes, float init, int count) {
| | ^~~~~~~~~~~~
| | |
| | (1) entry to ‘export_audio’
| 7 | do {
| 8 | float tmp_l[nframes];
| | ~~~~~
| | |
| | (2) region created on stack here
| 9 | for (int i = 0; i < nframes; i++)
| | ~~~~~~~~~~~
| | |
| | (3) following ‘false’ branch (when ‘i >=
nframes’)...
| 10 | tmp_l[i] = init;
| 11 | dsp_abs_max(tmp_l, nframes);
| | ~~~~~~~~~~~~~~~~~~~~~~~~~~~
| | |
| | (4) ...to here
| | (5) calling ‘dsp_abs_max’ from ‘export_audio’
|
+--> ‘dsp_abs_max’: events 6-7
|
| 3 | void dsp_abs_max(float *buf, unsigned size) {
| | ^~~~~~~~~~~
| | |
| | (6) entry to ‘dsp_abs_max’
| 4 | sink(buf[size - 1]);
| | ~~~~~~~~~~~~~~~~~~~
| | |
| | (7) use of uninitialized value ‘*buf_7(D) + _3’ here
|
cc1: some warnings being treated as errors
