[set] Fix undefined-behavior shift in _previous()

harfbuzz/src/hb-set.hh:138:43: runtime error: shift exponent 64 is too large for 64-bit type 'hb_set_t::page_t::elt_t' (aka 'unsigned long long')
5 years ago · e5c7ee9f75
parent 5fddc5f169
commit e5c7ee9f75
1 changed files with 5 additions and 1 deletions
--- a/src/hb-set.hh
+++ b/src/hb-set.hh
@ -135,7 +135,11 @@ struct hb_set_t
      unsigned int i = m / ELT_BITS;
      unsigned int j = m & ELT_MASK;

-      const elt_t vv = v[i] & ((elt_t (1) << (j + 1)) - 1);
+      /* Fancy mask to avoid shifting by elt_t bitsize, which is undefined. */
+      const elt_t mask = j < 8 * sizeof (elt_t) - 1 ?
+			 ((elt_t (1) << (j + 1)) - 1) :
+			 (elt_t) -1;
+      const elt_t vv = v[i] & mask;
      const elt_t *p = &vv;
      while (true)
      {