From 23d49d3e7e386bb2b26d5b944fc123f0f21ce0a6 Mon Sep 17 00:00:00 2001
From: Benjamin Peterson <benjamin@python.org>
Date: Tue, 28 Aug 2012 17:55:35 -0400
Subject: [PATCH] use the stricter PyMapping_Check (closes #15801)

---
 Lib/test/string_tests.py | 3 +++
 Misc/NEWS                | 3 +++
 Objects/stringobject.c   | 2 +-
 Objects/unicodeobject.c  | 2 +-
 4 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/Lib/test/string_tests.py b/Lib/test/string_tests.py
index 5931f3d88b..a161512634 100644
--- a/Lib/test/string_tests.py
+++ b/Lib/test/string_tests.py
@@ -1113,6 +1113,9 @@ class MixinStrUnicodeUserStringTest:
         self.checkraises(TypeError, '%10.*f', '__mod__', ('foo', 42.))
         self.checkraises(ValueError, '%10', '__mod__', (42,))
 
+        class X(object): pass
+        self.checkraises(TypeError, 'abc', '__mod__', X())
+
     def test_floatformatting(self):
         # float formatting
         for prec in xrange(100):
diff --git a/Misc/NEWS b/Misc/NEWS
index 71a858eb53..54c260c660 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -9,6 +9,9 @@ What's New in Python 2.7.4
 Core and Builtins
 -----------------
 
+- Issue #15801: Make sure mappings passed to '%' formatting are actually
+  subscriptable.
+
 - Issue #15604: Update uses of PyObject_IsTrue() to check for and handle
   errors correctly.  Patch by Serhiy Storchaka.
 
diff --git a/Objects/stringobject.c b/Objects/stringobject.c
index fd2f63001d..7c4a86b5e6 100644
--- a/Objects/stringobject.c
+++ b/Objects/stringobject.c
@@ -4254,7 +4254,7 @@ PyString_Format(PyObject *format, PyObject *args)
         arglen = -1;
         argidx = -2;
     }
-    if (Py_TYPE(args)->tp_as_mapping && !PyTuple_Check(args) &&
+    if (PyMapping_Check(args) && !PyTuple_Check(args) &&
         !PyObject_TypeCheck(args, &PyBaseString_Type))
         dict = args;
     while (--fmtcnt >= 0) {
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 59b138a21f..d40f2e46b2 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -8275,7 +8275,7 @@ PyObject *PyUnicode_Format(PyObject *format,
         arglen = -1;
         argidx = -2;
     }
-    if (Py_TYPE(args)->tp_as_mapping && !PyTuple_Check(args) &&
+    if (PyMapping_Check(args) && !PyTuple_Check(args) &&
         !PyObject_TypeCheck(args, &PyBaseString_Type))
         dict = args;
 
-- 
2.49.0