Fix overflow issue in bitset_last_p (see #81)

m-bitset.h

@@ -536,7 +536,9 @@ static inline bool
 bitset_last_p(const bitset_it_t it)
 {
   M_ASSERT (it != NULL && it->set != NULL);
-  return (it->index) >= (it->set->size)-1;
+  /* NOTE: Can not compute 'size-1' due to potential overflow
+     if size is 0 */
+  return (it->index+1) >= (it->set->size);
 }
 
 /* Test if both iterators reference the same bit */

tests/test-mbitset.c

@@ -202,7 +202,12 @@ static void test1(void)
   assert (bitset_end_p(it));
 
   assert (bitset_hash(set) != 0);
-  
+
+  bitset_clean(set);
+  bitset_it(it, set);
+  assert(bitset_end_p(it));
+  assert(bitset_last_p(it));
+
   bitset_clear(set);
   bitset_clear(set2);
 }