symbol.c: make dsym_fstrs an identity hash

* symbol.c (Init_sym): make dsym_fstrs a hash compared by identity
  as the keys are unique fstrings, to get rid of running hash and
  compare methods and causing new object allocation during garbage
  collection phase.  [ruby-dev:48891] [Bug #10933]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@49842 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,10 @@
+Wed Mar  4 11:52:30 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* symbol.c (Init_sym): make dsym_fstrs a hash compared by identity
+	  as the keys are unique fstrings, to get rid of running hash and
+	  compare methods and causing new object allocation during garbage
+	  collection phase.  [ruby-dev:48891] [Bug #10933]
+
 Wed Mar  4 10:16:57 2015  SHIBATA Hiroshi  <shibata.hiroshi@gmail.com>
 
 	* enum.c: Fix typo in slice_after's exception message.

symbol.c

@@ -122,7 +122,7 @@ static const struct st_hash_type symhash = {
 void
 Init_sym(void)
 {
-    VALUE dsym_fstrs = rb_hash_new();
+    VALUE dsym_fstrs = rb_ident_hash_new();
     global_symbols.dsymbol_fstr_hash = dsym_fstrs;
     rb_gc_register_mark_object(dsym_fstrs);
     rb_obj_hide(dsym_fstrs);