[Bug tree-optimization/31227] [4.3 Regression] -Warray-bounds doesn't play together with loop optimizations

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

------- Comment #1 from jakub at gcc dot gnu dot org  2007-03-16 19:17 -------
Another testcase, this time from glibc's malloc.c:
struct malloc_chunk {
  long prev_size;
  long size;
  struct malloc_chunk* fd;
  struct malloc_chunk* bk;
};
typedef struct malloc_chunk* mchunkptr;
struct malloc_state {
  mchunkptr        top;
  mchunkptr        last_remainder;
  mchunkptr        bins[128 * 2 - 2];
};
#define bin_at(m, i) \
  (mchunkptr) (((char *) &((m)->bins[((i) - 1) * 2]))                         \
             - __builtin_offsetof (struct malloc_chunk, fd))

void malloc_init_state(struct malloc_state *av)
{
  int     i;
  mchunkptr bin;

  for (i = 1; i < 128; ++i) {
    bin = bin_at(av,i);
    bin->fd = bin->bk = bin;
  }
}
at -O2 -Wall this warns:
warning: array subscript is below array bounds


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31227