[Bug middle-end/24178] GCC 4.0/4.1 generates code that produces unaligned access exceptions

["falk at debian dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #4 from falk at debian dot org  2005-10-04 07:32 -------
(In reply to comment #3)

> Correct me if I wrong, but loading long from passed pointer to char minus 4
> is not correct too.

You are right, I misread the example, the pointer that is cast to Foo* is
actually correctly aligned. Here is a slightly clearer test case:

typedef struct {
    long l;
    char p4;
} Foo;

void foo(char *fn) {
    Foo *p = (Foo *) (fn - 9);
    p->p4 = 1;
}

int main(int argc, char **argv)
{
#if defined(__alpha__) && defined(__linux__)
# include <asm/sysinfo.h>
# include <asm/unistd.h>
   syscall(__NR_osf_setsysinfo, SSI_NVPAIRS,
           (int[]){SSIN_UACPROC, UAC_SIGBUS | UAC_NOPRINT}, 1, 0, 0, 0);
#endif

   Foo p;
   foo(((char *) &p) + 9);
   return 0;
}

This is very similar to a gcc 3.3 bug that disappeared in 3.4:
http://bugs.debian.org/301983


-- 

falk at debian dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24178