[Bug middle-end/50460] [4.7 Regression] __builtin___strcpy_chk/__builtin_object_size don't work

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50460

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-09-23 07:26:10 UTC ---
Looking at:
const char *str1 = "JIHGFEDCBA";
#define strcpy(x,y) __builtin___strcpy_chk (x, y, __builtin_object_size (x, 1))

int
f1 (void)
{
  struct A { char buf1[9]; char buf2[1]; } a;
  strcpy (a.buf1 + (0 + 4), str1 + 5);
  return 0;
}

int
f2 (void)
{
  struct A { char buf1[9]; char buf2[1]; } a;
  strcpy ((char *) &a + (0 + 4), str1 + 5);
  return 0;
}

int
f3 (void)
{
  struct A { char buf1[9]; char buf2[1]; } a;
  char *p = (char *) &a;
  strcpy (p + (0 + 4), str1 + 5);
  return 0;
}

int
f4 (void)
{
  struct A { char buf0; char buf1[9]; char buf2[1]; } a;
  char *p = (char *) &a;
  strcpy (p + (0 + 5), str1 + 5);
  return 0;
}

int
f5 (void)
{
  struct A { char buf0; char buf1[9]; char buf2[1]; } a;
  strcpy ((char *) &a + (0 + 5), str1 + 5);
  return 0;
}

with GCC 4.4, seems we have always reconstructed it into &a.buf1[4].
So likely we want to reconstruct it from the MEM_REF in the *.objsz pass then.
If there is union involved, we probably want to reconstruct it to the
alternative with the largest possible __builtin_object_size (X, 1) resp.
smallest possible __builtin_object_size (X, 3).