public inbox for gcc-bugs@sourceware.org
help / color / mirror / Atom feed
* [Bug c/105319] New: Unexpected warning with zero-length sized array using -std=gnu99 and -O2
@ 2022-04-20 15:24 piannetta at kalrayinc dot com
2022-04-21 7:17 ` [Bug c/105319] " rguenth at gcc dot gnu.org
0 siblings, 1 reply; 2+ messages in thread
From: piannetta at kalrayinc dot com @ 2022-04-20 15:24 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105319
Bug ID: 105319
Summary: Unexpected warning with zero-length sized array using
-std=gnu99 and -O2
Product: gcc
Version: 10.3.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: piannetta at kalrayinc dot com
Target Milestone: ---
// main.c
#define LEN 0
static volatile int tab[LEN];
int main (int argc, char * argv[]) {
tab[argc] = 0;
}
The code above builds fine with:
gcc -Wall -std=gnu99
but reports a warning when compiled with -O2:
gcc -Wall -std=gnu99 -O2
main.c: In function ‘main’:
main.c:4:12: warning: array subscript argc is outside array bounds of ‘volatile
int[0]’ [-Warray-bounds]
4 | tab[argc] = 0;
| ~~~^~~~~~
main.c:2:21: note: while referencing ‘tab’
2 | static volatile int tab[LEN];
| ^~~
I've observed this behavior on gcc 10.3.1 and on gcc 12.0.1 (I have not tested
other versions).
I would have expected that the snippet would compile the same way in both cases
and not produce a warning since gnu99 supports zero-length arrays.
^ permalink raw reply [flat|nested] 2+ messages in thread
* [Bug c/105319] Unexpected warning with zero-length sized array using -std=gnu99 and -O2
2022-04-20 15:24 [Bug c/105319] New: Unexpected warning with zero-length sized array using -std=gnu99 and -O2 piannetta at kalrayinc dot com
@ 2022-04-21 7:17 ` rguenth at gcc dot gnu.org
0 siblings, 0 replies; 2+ messages in thread
From: rguenth at gcc dot gnu.org @ 2022-04-21 7:17 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105319
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |INVALID
Status|UNCONFIRMED |RESOLVED
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
There is no value of argc that is not an out-of-bound access so the warning is
accurate. Note that array bound diagnostics require -O2.
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2022-04-21 7:17 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-04-20 15:24 [Bug c/105319] New: Unexpected warning with zero-length sized array using -std=gnu99 and -O2 piannetta at kalrayinc dot com
2022-04-21 7:17 ` [Bug c/105319] " rguenth at gcc dot gnu.org
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).