proc.c: fix symbol proc mark

* proc.c (proc_mark): block.ep of Proc from Symbol is now NULL.
  [ruby-core:70961] [Bug #11560]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@51996 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Fri Oct  2 00:18:39 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* proc.c (proc_mark): block.ep of Proc from Symbol is now NULL.
+	  [ruby-core:70961] [Bug #11560]
+
 Wed Sep 30 15:47:13 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* vm_args.c (vm_caller_setup_arg_block): bypass Symbol#to_proc

proc.c

@@ -48,7 +48,9 @@ proc_mark(void *ptr)
     rb_proc_t *proc = ptr;
     RUBY_MARK_UNLESS_NULL(proc->block.proc);
     RUBY_MARK_UNLESS_NULL(proc->block.self);
-    RUBY_MARK_UNLESS_NULL(rb_vm_proc_envval(proc));
+    if (proc->block.ep) {
+	RUBY_MARK_UNLESS_NULL(rb_vm_proc_envval(proc));
+    }
     if (proc->block.iseq && RUBY_VM_IFUNC_P(proc->block.iseq)) {
 	rb_gc_mark((VALUE)(proc->block.iseq));
     }

test/ruby/test_symbol.rb

@@ -122,6 +122,11 @@ class TestSymbol < Test::Unit::TestCase
       GC.stress = true
       true.tap(&:itself)
     end;
+
+    assert_ruby_status([], <<-"end;", timeout: 0.1)
+      GC.stress = true
+      100.times {Proc.new(&:itself)}
+    end;
   end
 
   def test_call