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From: "symbioticfemale at cumallover dot me" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/113769] New: GCC fails to warn of integer being used
 uninitialized
Date: Mon, 05 Feb 2024 14:07:17 +0000
X-Bugzilla-Reason: CC
X-Bugzilla-Type: new
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X-Bugzilla-Product: gcc
X-Bugzilla-Component: c
X-Bugzilla-Version: 13.2.1
X-Bugzilla-Keywords: 
X-Bugzilla-Severity: normal
X-Bugzilla-Who: symbioticfemale at cumallover dot me
X-Bugzilla-Status: UNCONFIRMED
X-Bugzilla-Resolution: 
X-Bugzilla-Priority: P3
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D113769

            Bug ID: 113769
           Summary: GCC fails to warn of integer being used uninitialized
           Product: gcc
           Version: 13.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: symbioticfemale at cumallover dot me
  Target Milestone: ---

// The "used uninitialized" warning is not produced on both GCC and Tiny
Compiler. Clang recognizes the error. (-Wall on all compilers). See line
comments for further explanation. The latest version of GCC I've tested wit=
h is
13.2.1.

// Version 1: With printf

#include <stdio.h>
#include <stdint.h>
#include <pthread.h>

pthread_rwlock_t necessary_lock =3D PTHREAD_RWLOCK_INITIALIZER;
void do_nothing(const void *value);
void do_nothing(const void *value)
{
        printf("%p\n",value); // do anything on value other than (void) val=
ue
}

int main(void) {
        pthread_rwlock_rdlock(&necessary_lock);
        pthread_rwlock_unlock(&necessary_lock);
        // Fun fact: remove either the pthread_rwlock_rdlock +
pthread_rwlock_unlock, or the printf in do_nothing, and GCC catches the lac=
k of
initialization
        uint32_t pos;
        pos +=3D 1;
        do_nothing(&pos);
        printf("%u\n",pos);
}

// Version 2: Without printf

#include <stdio.h>
#include <stdint.h>
#include <pthread.h>

pthread_rwlock_t necessary_lock =3D PTHREAD_RWLOCK_INITIALIZER;
void do_nothing(const void *value);
void do_nothing(const void *value)
{
        (void) value;
}

int main(void) {


        pthread_rwlock_rdlock(&necessary_lock);
        pthread_rwlock_unlock(&necessary_lock);
        // Fun fact: remove either the pthread_rwlock_rdlock +
pthread_rwlock_unlock, or the do_nothing function call, and GCC catches the
lack of initialization. Add a printf after do_nothing and GCC will also cat=
ch
it.
        uint32_t pos;
        pos +=3D 1;
        do_nothing(&pos);
}=