[Bug c/113769] New: GCC fails to warn of integer being used uninitialized

[Bug c/113769] New: GCC fails to warn of integer being used uninitialized

[symbioticfemale at cumallover dot me]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113769

            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 with is
13.2.1.

// Version 1: With printf

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

pthread_rwlock_t necessary_lock = 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) 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 printf in do_nothing, and GCC catches the lack of
initialization
        uint32_t pos;
        pos += 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 = 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 catch
it.
        uint32_t pos;
        pos += 1;
        do_nothing(&pos);
}

[Bug c/113769] GCC fails to warn of integer being used uninitialized

[symbioticfemale at cumallover dot me]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113769

--- Comment #1 from SymbioticFemale <symbioticfemale at cumallover dot me> ---
Notably, it occurs with -Wall -Wextra -O2, etc. Integer size is irrelevant.
Changing the function do_nothing to 'static inline' does not make a difference.

It occurs with either pthread_mutex_t or pthread_rwlock_t.

[Bug c/113769] GCC fails to warn of integer being used uninitialized

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113769

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2024-02-05
           Keywords|                            |diagnostic
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW

[Bug tree-optimization/113769] GCC fails to warn of integer being used uninitialized

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113769

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 81809.

*** This bug has been marked as a duplicate of bug 81809 ***