5 files changed, 35 insertions, 1 deletions
diff --git a/ChangeLog b/ChangeLog
index 512428878d..0e05b9e058 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Wed Oct  9 13:53:14 2013  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* compar.c (cmp_eq): fail if recursion.  [ruby-core:57736] [Bug #9003]
+
+	* thread.c (rb_exec_recursive_paired_outer): new function which is
+	  combinnation of paired and outer variants.
+
 Wed Oct  9 09:18:14 2013  Koichi Sasada  <ko1@atdot.net>
 
 	* include/ruby/debug.h,
diff --git a/compar.c b/compar.c
index eea76cb637..2f4db291a4 100644
--- a/compar.c
+++ b/compar.c
@@ -52,9 +52,16 @@ rb_invcmp(VALUE x, VALUE y)
 }
 
 static VALUE
+cmp_eq_recursive(VALUE arg1, VALUE arg2, int recursive)
+{
+    if (recursive) return Qfalse;
+    return rb_funcallv(arg1, cmp, 1, &arg2);
+}
+
+static VALUE
 cmp_eq(VALUE *a)
 {
-    VALUE c = rb_funcall(a[0], cmp, 1, a[1]);
+    VALUE c = rb_exec_recursive_paired_outer(cmp_eq_recursive, a[0], a[1], a[1]);
 
     if (NIL_P(c)) return Qfalse;
     if (rb_cmpint(c, a[0], a[1]) == 0) return Qtrue;
diff --git a/include/ruby/intern.h b/include/ruby/intern.h
index 757699bd91..fa0c075b83 100644
--- a/include/ruby/intern.h
+++ b/include/ruby/intern.h
@@ -448,6 +448,7 @@ void rb_thread_atfork_before_exec(void);
 VALUE rb_exec_recursive(VALUE(*)(VALUE, VALUE, int),VALUE,VALUE);
 VALUE rb_exec_recursive_paired(VALUE(*)(VALUE, VALUE, int),VALUE,VALUE,VALUE);
 VALUE rb_exec_recursive_outer(VALUE(*)(VALUE, VALUE, int),VALUE,VALUE);
+VALUE rb_exec_recursive_paired_outer(VALUE(*)(VALUE, VALUE, int),VALUE,VALUE,VALUE);
 /* dir.c */
 VALUE rb_dir_getwd(void);
 /* file.c */
diff --git a/test/ruby/test_comparable.rb b/test/ruby/test_comparable.rb
index c686adeceb..747f1e29a7 100644
--- a/test/ruby/test_comparable.rb
+++ b/test/ruby/test_comparable.rb
@@ -76,4 +76,11 @@ class TestComparable < Test::Unit::TestCase
       assert_nil(Time.new <=> "")
     }
   end
+
+  def test_no_cmp
+    bug9003 = '[ruby-core:57736] [Bug #9003]'
+    assert_nothing_raised(SystemStackError, bug9003) {
+      @o <=> @o.dup
+    }
+  end
 end
diff --git a/thread.c b/thread.c
index 463f5d3b0e..4789dfa0e8 100644
--- a/thread.c
+++ b/thread.c
@@ -4954,6 +4954,18 @@ rb_exec_recursive_outer(VALUE (*func) (VALUE, VALUE, int), VALUE obj, VALUE arg)
 }
 
 /*
+ * If recursion is detected on the current method, obj and paired_obj,
+ * the outermost func will be called with (obj, arg, Qtrue). All inner
+ * func will be short-circuited using throw.
+ */
+
+VALUE
+rb_exec_recursive_paired_outer(VALUE (*func) (VALUE, VALUE, int), VALUE obj, VALUE paired_obj, VALUE arg)
+{
+    return exec_recursive(func, obj, rb_obj_id(paired_obj), arg, 1);
+}
+
+/*
  *  call-seq:
  *     thread.backtrace    -> array
  *