[Bug c/56391] New: variable set but unused isn't reported. if it has been used prior to setting it to a new value.

[begnoc at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56391

             Bug #: 56391
           Summary: variable set but unused isn't reported. if it has been
                    used prior to setting it to a new value.
    Classification: Unclassified
           Product: gcc
           Version: 4.6.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: begnoc@gmail.com


#include <stdio.h>
#include <stdlib.h>

void release(void*);

void
release(void *ptr)
{
    free(ptr);
    ptr = NULL;
}

int
main(void)
{
    int    *a;

    a = malloc(sizeof(int));
    if(a == NULL){
        perror("malloc");
        return 1;
    }
    *a = 42;
    printf("*a == %d\n", *a);
    release(a);
    if(a)
        printf("*a == %d\n", *a);

    return 0;
}

-------------------------------

Compiling this with "gcc -Wall -Wextra" doesn't report anything (should
be varible set but unused at line 10). This is clearly isn't what the
programmer intended and is easy to catch. Just reset the unused flag
after setting the variable.

This is also the case with g++.