[Bug c/106119] Bogus use-after-free warning triggered by optimizer

[tom.cosgrove at arm dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106119

--- Comment #2 from Tom Cosgrove <tom.cosgrove at arm dot com> ---
Further addendum:

If you use a `void *` to save the value of the pointer, you don't get the
warning!

See https://gcc.godbolt.org/z/fof8a747z


i.e. this code does not generate the warning:

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

void calloc_self_test( __attribute__ ((unused)) int verbose )
{
    void *buffer1 = calloc( 1, 1 );
    void *old_buffer1 = buffer1;
    free( buffer1 );
    buffer1 = calloc( 1, 1 );
    int same = ( old_buffer1 == buffer1 );
    if( verbose )
        printf( "  CALLOC(1 again): passed (%s address)\n",
                same ? "same" : "different" );
    free( buffer1 );
}