[Bug c/18426] New: -Wstrict-aliasing fails to report simple case of breaking strict aliasing rules

[torger at ludd dot luth dot se]

/* 
 
x86 platform. 
 
This simple program with the obvious breaking of strict aliasing  
rules does not generate a warning with -Wstrict-aliasing 
 
gcc -Wall -Wstrict-aliasing test.c 
 
tested on Pentium 4 
 
gcc 3.4.2, gcc 3.3.5 and gcc 3.2.3, as built for debian unstable 
2004 Nov 9 
 
*/ 
 
#include <stdio.h> 
 
unsigned long 
hash(void *key) 
{ 
    unsigned long long u[1]; 
    u[0] = *(unsigned long long *)key; 
    return ((unsigned long *)u)[0] ^ ((unsigned long *)u)[1]; 
} 
 
int 
main(void) 
{ 
    unsigned long long ull; 
 
    ull = 0xDEADBEAF; 
     
    fprintf(stderr, "%08lX\n", hash(&ull)); 
    return 0; 
}

-- 
           Summary: -Wstrict-aliasing fails to report simple case of
                    breaking strict aliasing rules
           Product: gcc
           Version: 3.4.2
            Status: UNCONFIRMED
          Severity: minor
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: torger at ludd dot luth dot se
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18426