Merge pull request #2049 from ksss/str-dup

mrb_str_dup return shared string instead of new string

src/state.c

@@ -134,9 +134,7 @@ mrb_irep_free(mrb_state *mrb, mrb_irep *irep)
     mrb_free(mrb, irep->iseq);
   for (i=0; i<irep->plen; i++) {
     if (mrb_type(irep->pool[i]) == MRB_TT_STRING) {
-      if ((mrb_str_ptr(irep->pool[i])->flags & (MRB_STR_NOFREE|MRB_STR_EMBED)) == 0) {
-        mrb_free(mrb, RSTRING_PTR(irep->pool[i]));
-      }
+      mrb_gc_free_str(mrb, RSTRING(irep->pool[i]));
       mrb_free(mrb, mrb_obj_ptr(irep->pool[i]));
     }
 #ifdef MRB_WORD_BOXING

src/string.c

@@ -796,10 +796,11 @@ mrb_str_index(mrb_state *mrb, mrb_value str, mrb_value sub, mrb_int offset)
 mrb_value
 mrb_str_dup(mrb_state *mrb, mrb_value str)
 {
-  /* should return shared string */
   struct RString *s = mrb_str_ptr(str);
+  struct RString *dup = str_new(mrb, 0, 0);
 
-  return mrb_str_new(mrb, STR_PTR(s), STR_LEN(s));
+  str_with_class(mrb, dup, str);
+  return str_replace(mrb, dup, s);
 }
 
 static mrb_value