On Sun, Nov 13, 2022 at 10:40 AM Andrew Pinski <pins...@gmail.com> wrote: > > 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."
I should note the main reason why I Know about this is because I fixed this feature years ago (at least for C front-end) and added the option to disable the feature. > > 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/>