mrb_str_new(mrb, "", len) creates an unmodifiable string object; ref #2674

mrbgems/mruby-string-ext/src/string.c

@@ -356,7 +356,7 @@ mrb_str_prepend(mrb_state *mrb, mrb_value self)
   }
   s2 = mrb_str_ptr(other);
   len = RSTR_LEN(s1) + RSTR_LEN(s2);
-  temp_str = mrb_str_new(mrb, "", RSTR_LEN(s1));
+  temp_str = mrb_str_new(mrb, NULL, RSTR_LEN(s1));
   temp_s = mrb_str_ptr(temp_str);
   memcpy(RSTR_PTR(temp_s), RSTR_PTR(s1), RSTR_LEN(s1));
   if (RSTRING_CAPA(self) < len) {

src/string.c

@@ -163,7 +163,7 @@ str_new(mrb_state *mrb, const char *p, size_t len)
 {
   struct RString *s;
 
-  if (mrb_ro_data_p(p)) {
+  if (p && mrb_ro_data_p(p)) {
     return str_new_static(mrb, p, len);
   }
   s = mrb_obj_alloc_string(mrb);