I just tried to compile package libgdiplus-1.1.13-2 with a prerelease of
the GNU C compiler version 4.2.

It said

testbits.c:101: warning: operation on "cptr" may be undefined

The source code is

        for (i = 0; i < 5; i++) {
            printf ("%02x%02x%02x ", *cptr++, *cptr++, *cptr++);
        }

I agree with the compiler.  Suggest new code

        for (i = 0; i < 5; i++) {
            printf ("%02x%02x%02x ", cptr[ 0], cptr[ 1], cptr[ 2]);
            cptr += 3;
        }