https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105080
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jakub at gcc dot gnu.org,
| |rguenth at gcc dot gnu.org
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #1)
> Confirmed. The issue is that at -O0 we do not use SCEV and thus range
> analysis is limited, just using i < 16.
>
> static unsigned int
> printf_strlen_execute (function *fun, bool warn_only)
> {
> strlen_optimize = !warn_only;
>
> calculate_dominance_info (CDI_DOMINATORS);
>
> bool use_scev = optimize > 0 && flag_printf_return_value;
> if (use_scev)
> {
> loop_optimizer_init (LOOPS_NORMAL);
> scev_initialize ();
> }
>
> at -O0 we call this when warn_format_overflow > 0 || warn_format_trunc > 0 so
> to improve we could maybe do || warn_only above. That would fix the bogus
> diagnostic.
Or rather always do this, even the late pass as otherwise I see a bogus
diagnostic with -fno-printf-return-value even when optimizing:
> ./cc1 -quiet t.c -Wall -O -fno-printf-return-value
t.c:1:6: warning: return type of 'main' is not 'int' [-Wmain]
1 | void main(void)
| ^~~~
t.c: In function 'main':
t.c:7:55: warning: '%d' directive output may be truncated writing between 1 and
11 bytes into a region of size 3 [-Wformat-truncation=]
7 | __builtin_snprintf(foo, sizeof(foo), "%d", i);
| ^~
t.c:7:54: note: directive argument in the range [-2147483647, 2147483647]
7 | __builtin_snprintf(foo, sizeof(foo), "%d", i);
| ^~~~
t.c:7:17: note: '__builtin_snprintf' output between 2 and 12 bytes into a
destination of size 3
7 | __builtin_snprintf(foo, sizeof(foo), "%d", i);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
