object.c (rb_class_real): do not dereference 0 VALUE

* test/ruby/test_module.rb (test_inspect_segfault):
  Test case and bug report by Thomas Stratmann.
  [ruby-core:65214] [Bug #10282]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47715 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,11 @@
+Fri Sep 26 05:21:01 2014  Eric Wong  <e@80x24.org>
+
+	* object.c (rb_class_real): do not dereference 0 VALUE
+
+	* test/ruby/test_module.rb (test_inspect_segfault):
+	  Test case and bug report by Thomas Stratmann.
+	  [ruby-core:65214] [Bug #10282]
+
 Fri Sep 26 05:12:10 2014  Eric Wong  <e@80x24.org>
 
 	* man/ruby.1: document stack size env variables

object.c

@@ -206,9 +206,8 @@ rb_obj_not_equal(VALUE obj1, VALUE obj2)
 VALUE
 rb_class_real(VALUE cl)
 {
-    if (cl == 0)
-        return 0;
-    while ((RBASIC(cl)->flags & FL_SINGLETON) || BUILTIN_TYPE(cl) == T_ICLASS) {
+    while (cl &&
+        ((RBASIC(cl)->flags & FL_SINGLETON) || BUILTIN_TYPE(cl) == T_ICLASS)) {
 	cl = RCLASS_SUPER(cl);
     }
     return cl;

test/ruby/test_module.rb

@@ -1971,6 +1971,30 @@ class TestModule < Test::Unit::TestCase
     }
   end
 
+  def test_inspect_segfault
+    bug_10282 = '[ruby-core:65214] [Bug #10282]'
+    assert_separately [], <<-RUBY
+      module ShallowInspect
+        def shallow_inspect
+          "foo"
+        end
+      end
+
+      module InspectIsShallow
+        include ShallowInspect
+        alias_method :inspect, :shallow_inspect
+      end
+
+      class A
+      end
+
+      A.prepend InspectIsShallow
+
+      expect = "#<Method: A(Object)#inspect(shallow_inspect)>"
+      assert_equal expect, A.new.method(:inspect).inspect, "#{bug_10282}"
+    RUBY
+  end
+
   private
 
   def assert_top_method_is_private(method)