[Bug middle-end/110761] New: No warning for an uninitialized variable when used within its own initialization

[Bug middle-end/110761] New: No warning for an uninitialized variable when used within its own initialization

[jwzeng at nuaa dot edu.cn]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110761

            Bug ID: 110761
           Summary: No warning for an uninitialized variable when used
                    within its own initialization
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jwzeng at nuaa dot edu.cn
  Target Milestone: ---

Link to the Compiler Explorer: https://godbolt.org/z/ra7P3EcMn

There is no warning for a variable is uninitialized when used within its own
initialization.

$ cat test.c
int main(void) 
{
    int a = 1, b = 2;
    int g = (a % ((~0) && b)) && g;
}
$ gcc-trunk -Wall -Wextra -pedantic -c test.c
$
$ clang-16.0.0 -Weverything -pedantic -c test.c
test.c:4:34: warning: variable 'g' is uninitialized when used within its own
initialization [-Wuninitialized]
    int g = (a % ((~0) && b)) && g;
        ~                        ^
1 warning generated.
$
$ gcc-trunk -v
gcc (GCC) 14.0.0 20230619 (experimental) [master r14-1917-gf8e0270272]
$ clang-16.0.0 -v
clang version 16.0.0
Target: x86_64-unknown-linux-gnu

Would it be better to output warning information like clang? In gcc-11.4 and
earlier versions, there will be corresponding warnings.

[Bug middle-end/110761] No warning for an uninitialized variable when used within its own initialization

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110761

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> ---
Because g is only used conditionally and that condition is false.  Does
clang diagnose

int g = 0 && g;

?

if you write

int g = 1 && g;

we diagnose the use.