On Sun, Nov 13, 2022 at 10:36 AM Alejandro Colomar via Gcc
<gcc@gcc.gnu.org> wrote:
>
> Hi,
>
> While discussing some idea for a new feature, I tested the following example
> program:
>
>
> int main(void)
> {
> int i = i;
> return i;
> }
This is NOT a bug but a documented way of having the warning not being there.
See
https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/Warning-Options.html#index-Winit-self
https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/Warning-Options.html#index-Wuninitialized
"If you want to warn about code that uses the uninitialized value of
the variable in its own initializer, use the -Winit-self option."
Thanks,
Andrew Pinski
>
>
> It seems obvious that it should give a warning, and in Clang it does:
>
>
> $ clang --version | head -n1
> Debian clang version 14.0.6
>
> $ clang -Wall -Wextra foo.c
> foo.c:3:10: warning: variable 'i' is uninitialized when used within its
> own
> initialization [-Wuninitialized]
> int i = i;
> ~ ^
> 1 warning generated.
>
>
> But for GCC it looks fine:
>
> $ gcc --version | head -n1
> gcc (Debian 12.2.0-9) 12.2.0
>
> $ gcc -Wall -Wextra foo.c
> $
>
>
> Until you enable the analyzer, which catches the uninitialized use:
>
>
> $ gcc -fanalyzer foo.c
> foo.c: In function ‘main’:
> foo.c:3:13: warning: use of uninitialized value ‘i’ [CWE-457]
> [-Wanalyzer-use-of-uninitialized-value]
> 3 | int i = i;
> | ^
> ‘main’: events 1-2
> |
> | 3 | int i = i;
> | | ^
> | | |
> | | (1) region created on stack here
> | | (2) use of uninitialized value ‘i’ here
> |
>
>
>
> I expect that GCC should be able to detect this bug with a simple warning.
> The
> analyzer is quite unreadable compared to normal warnings.
>
> Cheers,
> Alex
>
> --
> <http://www.alejandro-colomar.es/>
