Move mrb_assert() position.

src/string.c

@@ -121,6 +121,9 @@ mrb_str_buf_new(mrb_state *mrb, size_t capa)
 static void
 resize_capa(mrb_state *mrb, struct RString *s, size_t capacity)
 {
+#if SIZE_MAX > MRB_INT_MAX
+    mrb_assert(capacity < MRB_INT_MAX);
+#endif
   if (RSTR_EMBED_P(s)) {
     if (RSTRING_EMBED_LEN_MAX < capacity) {
       char *const tmp = (char *)mrb_malloc(mrb, capacity+1);
@@ -133,9 +136,6 @@ resize_capa(mrb_state *mrb, struct RString *s, size_t capacity)
     }
   }
   else {
-#if SIZE_MAX > MRB_INT_MAX
-    mrb_assert(capacity <= MRB_INT_MAX);
-#endif
     s->as.heap.ptr = (char *)mrb_realloc(mrb, RSTR_PTR(s), capacity+1);
     s->as.heap.aux.capa = capacity;
   }