merge revision(s) r45350: [Backport ruby#9645]

	* variable.c (rb_const_set): delete existing entry on redefinition
	  [Bug ruby#9645]

	* test/ruby/test_const.rb (test_redefinition): test for leak

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_1@46301 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

Conflicts:
	ChangeLog
	version.h

Author: nagachika

test/ruby/test_const.rb

@@ -1,5 +1,6 @@
 # -*- coding: us-ascii -*-
 require 'test/unit'
+require_relative 'envutil'
 
 class TestConst < Test::Unit::TestCase
   TEST1 = 1
@@ -54,5 +55,12 @@ def test_redefinition
 #{__FILE__}:#{__LINE__-1}: warning: already initialized constant #{c}::X
 #{__FILE__}:#{__LINE__-3}: warning: previous definition of X was here
 WARNING
+    code = <<-PRE
+olderr = $stderr.dup
+$stderr.reopen(File::NULL, "wb")
+350000.times { FOO = :BAR }
+$stderr.reopen(olderr)
+PRE
+    assert_no_memory_leak([], '', code, 'redefined constant')
   end
 end

variable.c

@@ -2203,6 +2203,8 @@ rb_const_set(VALUE klass, ID id, VALUE val)
 		    rb_compile_warn(RSTRING_PTR(ce->file), ce->line,
 				    "previous definition of %"PRIsVALUE" was here", name);
 		}
+		st_delete(RCLASS_CONST_TBL(klass), &id, 0);
+		xfree(ce);
 	    }
 	}
     }