change arena_next overflow check to an assert

Author: nascheme

Objects/obmalloc.c

@@ -2962,7 +2962,11 @@ arena_map_mark_used(uintptr_t arena_base, int is_used)
          */
         n_hi->arenas[i3].tail_hi = is_used ? tail : 0;
         uintptr_t arena_next = arena_base + ARENA_SIZE;
-        /* check for overflow of arena_next */
+        /* If arena_base is a legit arena address, so is arena_next - 1
+         * (last address in arena).  If arena_next overflows then it
+         * must overflow to 0.  However, that would mean arena_base was
+         * "ideal" and we should not be in this case. */
+        assert(arena_base < arena_next);
         if (arena_next > arena_base) {
             arena_map3_t *n_lo = arena_map_get((block *)arena_next, is_used);
             if (n_lo == NULL) {