[Bug c/23106] New: -Wstrict-aliasing=2 doesn't warn for all aliasing problems

["fn_x at hotmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

Hi,

This program:

int main() {
    int a = 1;

    * (short *) (char *) &a = 2;

    char *p = (char *) &a;
    * (short *) p = 3;

    return a;
}

returns 1 when compiled with gcc 4.0.1 (nothing more is necessary than gcc -O2
test.c). However, adding -Wstrict-aliasing=2 does not make any warning for this
show up. This happens with void * as well.

I first asked about the first case on gcc-help, and Ian Lance Taylor followed up
with a patch to show a warning:
http://gcc.gnu.org/ml/gcc-help/2005-07/msg00292.html
For the second case, he asked to open a bug here.

-- 
           Summary: -Wstrict-aliasing=2 doesn't warn for all aliasing
                    problems
           Product: gcc
           Version: 4.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: fn_x at hotmail dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23106