Fix:

Michael W. Hudson · Michael W. Hudson · commit 0edc7a03e250 · 2005-07-12T10:21:19.000Z
[ 1229429 ] missing Py_DECREF in PyObject_CallMethod

Add a test in test_enumerate, which is a bit random, but suffices
(reversed_new calls PyObject_CallMethod under some circumstances).
diff --git a/Lib/test/test_enumerate.py b/Lib/test/test_enumerate.py
@@ -1,4 +1,5 @@
 import unittest
+import sys
 
 from test import test_support
 
@@ -175,6 +176,25 @@ def test_args(self):
         self.assertRaises(TypeError, reversed)
         self.assertRaises(TypeError, reversed, [], 'extra')
 
+    def test_bug1229429(self):
+        # this bug was never in reversed, it was in
+        # PyObject_CallMethod, and reversed_new calls that sometimes.
+        if not hasattr(sys, "getrefcount"):
+            return
+        def f():
+            pass
+        r = f.__reversed__ = object()
+        rc = sys.getrefcount(r)
+        for i in range(10):
+            try:
+                reversed(f)
+            except TypeError:
+                pass
+            else:
+                self.fail("non-callable __reversed__ didn't raise!")
+        self.assertEqual(rc, sys.getrefcount(r))
+            
+
 def test_main(verbose=None):
     testclasses = (EnumerateTestCase, SubclassTestCase, TestEmpty, TestBig,
                    TestReversed)
diff --git a/Misc/NEWS b/Misc/NEWS
@@ -12,6 +12,9 @@ What's New in Python 2.5 alpha 1?
 Core and builtins
 -----------------
 
+- SF bug #1229429: PyObject_CallMethod failed to decrement some
+  reference counts in some error exit cases.
+
 - SF bug #1185883:  Python's small-object memory allocator took over
   a block managed by the platform C library whenever a realloc specified
   a small new size.  However, there's no portable way to know then how
diff --git a/Objects/abstract.c b/Objects/abstract.c
@@ -1797,7 +1797,9 @@ PyObject *
 PyObject_CallMethod(PyObject *o, char *name, char *format, ...)
 {
 	va_list va;
-	PyObject *args, *func = 0, *retval;
+	PyObject *args = NULL;
+	PyObject *func = NULL;
+	PyObject *retval = NULL;
 
 	if (o == NULL || name == NULL)
 		return null_error();
@@ -1808,8 +1810,10 @@ PyObject_CallMethod(PyObject *o, char *name, char *format, ...)
 		return 0;
 	}
 
-	if (!PyCallable_Check(func))
-		return type_error("call of non-callable attribute");
+	if (!PyCallable_Check(func)) {
+		type_error("call of non-callable attribute"); 
+		goto exit;
+	}
 
 	if (format && *format) {
 		va_start(va, format);
@@ -1820,23 +1824,24 @@ PyObject_CallMethod(PyObject *o, char *name, char *format, ...)
 		args = PyTuple_New(0);
 
 	if (!args)
-		return NULL;
+		goto exit;
 
 	if (!PyTuple_Check(args)) {
 		PyObject *a;
 
 		a = PyTuple_New(1);
 		if (a == NULL)
-			return NULL;
+			goto exit;
 		if (PyTuple_SetItem(a, 0, args) < 0)
-			return NULL;
+			goto exit;
 		args = a;
 	}
 
 	retval = PyObject_Call(func, args, NULL);
 
-	Py_DECREF(args);
-	Py_DECREF(func);
+  exit:
+	Py_XDECREF(args);
+	Py_XDECREF(func);
 
 	return retval;
 }
