vm_method.c: fix infinite recursion

* vm_method.c (rb_method_entry_get_without_cache): get rid of
  infinite recursion at aliases in a subclass and a superclass.
  return actually defined class for other than singleton class.
  [ruby-core:60431] [Bug #9475]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45367 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,10 @@
+Thu Mar 20 12:31:26 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* vm_method.c (rb_method_entry_get_without_cache): get rid of
+	  infinite recursion at aliases in a subclass and a superclass.
+	  return actually defined class for other than singleton class.
+	  [ruby-core:60431] [Bug #9475]
+
 Wed Mar 19 17:13:06 2014  Eric Wong  <e@80x24.org>
 
 	* time.c (time_mload): freeze and preserve marshal-loaded time zone

test/ruby/test_alias.rb

@@ -132,4 +132,51 @@ class TestAlias < Test::Unit::TestCase
       GC.verify_internal_consistency
     }
   end
+
+  def test_cyclic_zsuper
+    bug9475 = '[ruby-core:60431] [Bug #9475]'
+
+    a = Module.new do
+      def foo
+        "A"
+      end
+    end
+
+    b = Class.new do
+      include a
+      attr_reader :b
+
+      def foo
+        @b ||= 0
+        raise SystemStackError if (@b += 1) > 1
+        # "foo from B"
+        super + "B"
+      end
+    end
+
+    c = Class.new(b) do
+      alias orig_foo foo
+
+      def foo
+        # "foo from C"
+        orig_foo + "C"
+      end
+    end
+
+    b.class_eval do
+      alias orig_foo foo
+      attr_reader :b2
+
+      def foo
+        @b2 ||= 0
+        raise SystemStackError if (@b2 += 1) > 1
+        # "foo from B (again)"
+        orig_foo + "B2"
+      end
+    end
+
+    assert_nothing_raised(SystemStackError, bug9475) do
+      assert_equal("ABC", c.new.foo, bug9475)
+    end
+  end
 end

vm_method.c

@@ -578,8 +578,15 @@ rb_method_entry_get_without_cache(VALUE klass, ID id,
     VALUE defined_class;
     rb_method_entry_t *me = search_method(klass, id, &defined_class);
 
-    if (me && RB_TYPE_P(me->klass, T_ICLASS))
-	defined_class = me->klass;
+    if (me) {
+	switch (BUILTIN_TYPE(me->klass)) {
+	  case T_CLASS:
+	    if (RBASIC(klass)->flags & FL_SINGLETON) break;
+	    /* fall through */
+	  case T_ICLASS:
+	    defined_class = me->klass;
+	}
+    }
 
     if (ruby_running) {
 	if (OPT_GLOBAL_METHOD_CACHE) {