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From: "jwzeng at nuaa dot edu.cn" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/110761] New: No warning for an uninitialized
 variable when used within its own initialization
Date: Fri, 21 Jul 2023 08:04:22 +0000
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X-Bugzilla-Version: 14.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D110761

            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)=20
{
    int a =3D 1, b =3D 2;
    int g =3D (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 =3D (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.=