Implement Ruby2.7's frozen strings from `Symbol#to_s`.

2 files changed, 8 insertions, 3 deletions

diff --git a/src/class.c b/src/class.c
index 745e0a72c..9803e7662 100644
--- a/src/class.c
+++ b/src/class.c
@@ -72,6 +72,7 @@ mrb_class_name_class(mrb_state *mrb, struct RClass *outer, struct RClass *c, mrb
       }
       return;
     }
+    name = mrb_str_dup(mrb, name);
     mrb_str_cat_cstr(mrb, name, "::");
     mrb_str_cat_cstr(mrb, name, mrb_sym_name(mrb, id));
   }
diff --git a/src/symbol.c b/src/symbol.c
index a4c453d32..2696b5210 100644
--- a/src/symbol.c
+++ b/src/symbol.c
@@ -517,14 +517,18 @@ mrb_sym_str(mrb_state *mrb, mrb_sym sym)
 {
   mrb_int len;
   const char *name = mrb_sym_name_len(mrb, sym, &len);
+  mrb_value str;
 
   if (!name) return mrb_undef_value(); /* can't happen */
   if (SYMBOL_INLINE_P(sym)) {
-    mrb_value str = mrb_str_new(mrb, name, len);
+    str = mrb_str_new(mrb, name, len);
     RSTR_SET_ASCII_FLAG(mrb_str_ptr(str));
-    return str;
   }
-  return mrb_str_new_static(mrb, name, len);
+  else {
+    str = mrb_str_new_static(mrb, name, len);
+  }
+  MRB_SET_FROZEN_FLAG(mrb_str_ptr(str));
+  return str;
 }
 
 static const char*