- Check for overflow, so that N * S stays in size_t range.
- The check may be slightly conservative, but an exact check isn't
- worth the trouble. */
- if ((size_t) -1 / 3 * 2 / s <= n)
+ Check for overflow, so that N * S stays in both ptrdiff_t and
+ size_t range. The check may be slightly conservative, but an
+ exact check isn't worth the trouble. */
+ if ((PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX) / 3 * 2 / s
+ <= n)