diff -up Python-2.7.3/Lib/test/test_gc.py.gc-assertions Python-2.7.3/Lib/test/test_gc.py

--- Python-2.7.3/Lib/test/test_gc.py.gc-assertions	2013-02-20 16:28:20.890536607 -0500

+++ Python-2.7.3/Lib/test/test_gc.py	2013-02-20 16:39:52.720489297 -0500

@@ -1,6 +1,7 @@

 import unittest

-from test.test_support import verbose, run_unittest

+from test.test_support import verbose, run_unittest, import_module

 import sys

+import sysconfig

 import time

 import gc

 import weakref

@@ -32,6 +33,8 @@ class GC_Detector(object):

         self.wr = weakref.ref(C1055820(666), it_happened)

+BUILT_WITH_NDEBUG = ('-DNDEBUG' in sysconfig.get_config_vars()['PY_CFLAGS'])

+

 ### Tests

 ###############################################################################

@@ -476,6 +479,49 @@ class GCTests(unittest.TestCase):

             # would be damaged, with an empty __dict__.

             self.assertEqual(x, None)

+    @unittest.skipIf(BUILT_WITH_NDEBUG,

+                     'built with -NDEBUG')

+    def test_refcount_errors(self):

+        # Verify the "handling" of objects with broken refcounts

+ 

+        import_module("ctypes") #skip if not supported

+

+        import subprocess

+        code = '''if 1:

+        a = []

+        b = [a]

+

+        # Simulate the refcount of "a" being too low (compared to the

+        # references held on it by live data), but keeping it above zero

+        # (to avoid deallocating it):

+        import ctypes

+        ctypes.pythonapi.Py_DecRef(ctypes.py_object(a))

+

+        # The garbage collector should now have a fatal error when it reaches

+        # the broken object:

+        import gc

+        gc.collect()

+        '''

+        p = subprocess.Popen([sys.executable, "-c", code],

+                             stdout=subprocess.PIPE,

+                             stderr=subprocess.PIPE)

+        stdout, stderr = p.communicate()

+        p.stdout.close()

+        p.stderr.close()

+        # Verify that stderr has a useful error message:

+        self.assertRegexpMatches(stderr,

+            b'Modules/gcmodule.c:[0-9]+: visit_decref: Assertion "gc->gc.gc_refs != 0" failed.')

+        self.assertRegexpMatches(stderr,

+            b'refcount was too small')

+        self.assertRegexpMatches(stderr,

+            b'object  : \[\]')

+        self.assertRegexpMatches(stderr,

+            b'type    : list')

+        self.assertRegexpMatches(stderr,

+            b'refcount: 1')

+        self.assertRegexpMatches(stderr,

+            b'address : 0x[0-9a-f]+')

+

 class GCTogglingTests(unittest.TestCase):

     def setUp(self):

         gc.enable()

diff -up Python-2.7.3/Modules/gcmodule.c.gc-assertions Python-2.7.3/Modules/gcmodule.c

--- Python-2.7.3/Modules/gcmodule.c.gc-assertions	2012-04-09 19:07:34.000000000 -0400

+++ Python-2.7.3/Modules/gcmodule.c	2013-02-20 16:28:21.029536600 -0500

@@ -21,6 +21,73 @@

 #include "Python.h"

 #include "frameobject.h"        /* for PyFrame_ClearFreeList */

+/* 

+   Define a pair of assertion macros.

+

+   These work like the regular C assert(), in that they will abort the

+   process with a message on stderr if the given condition fails to hold,

+   but compile away to nothing if NDEBUG is defined.

+

+   However, before aborting, Python will also try to call _PyObject_Dump() on

+   the given object.  This may be of use when investigating bugs in which a

+   particular object is corrupt (e.g. buggy a tp_visit method in an extension

+   module breaking the garbage collector), to help locate the broken objects.

+

+   The WITH_MSG variant allows you to supply an additional message that Python

+   will attempt to print to stderr, after the object dump.

+*/

+#ifdef NDEBUG

+/* No debugging: compile away the assertions: */

+#define PyObject_ASSERT_WITH_MSG(obj, expr, msg) ((void)0)

+#else

+/* With debugging: generate checks: */

+#define PyObject_ASSERT_WITH_MSG(obj, expr, msg) \

+  ((expr)                                           \

+   ? (void)(0)                                      \

+   : _PyObject_AssertFailed((obj),                  \

+                            (msg),                  \

+                            (__STRING(expr)),       \

+                            (__FILE__),             \

+                            (__LINE__),             \

+                            (__PRETTY_FUNCTION__)))

+#endif

+

+#define PyObject_ASSERT(obj, expr) \

+  PyObject_ASSERT_WITH_MSG(obj, expr, NULL)

+

+static void _PyObject_AssertFailed(PyObject *,  const char *,

+				   const char *, const char *, int,

+				   const char *);

+

+static void

+_PyObject_AssertFailed(PyObject *obj, const char *msg, const char *expr,

+		       const char *file, int line, const char *function)

+{

+    fprintf(stderr,

+            "%s:%d: %s: Assertion \"%s\" failed.\n",

+            file, line, function, expr);

+    if (msg) {

+        fprintf(stderr, "%s\n", msg);

+    }

+

+    fflush(stderr);

+

+    if (obj) {

+        /* This might succeed or fail, but we're about to abort, so at least

+           try to provide any extra info we can: */

+        _PyObject_Dump(obj);

+    }

+    else {

+        fprintf(stderr, "NULL object\n");

+    }

+

+    fflush(stdout);

+    fflush(stderr);

+

+    /* Terminate the process: */

+    abort();

+}

+

 /* Get an object's GC head */

 #define AS_GC(o) ((PyGC_Head *)(o)-1)

@@ -288,7 +355,8 @@ update_refs(PyGC_Head *containers)

 {

     PyGC_Head *gc = containers->gc.gc_next;

     for (; gc != containers; gc = gc->gc.gc_next) {

-        assert(gc->gc.gc_refs == GC_REACHABLE);

+        PyObject_ASSERT(FROM_GC(gc),

+                        gc->gc.gc_refs == GC_REACHABLE);

         gc->gc.gc_refs = Py_REFCNT(FROM_GC(gc));

         /* Python's cyclic gc should never see an incoming refcount

          * of 0:  if something decref'ed to 0, it should have been

@@ -308,7 +376,8 @@ update_refs(PyGC_Head *containers)

          * so serious that maybe this should be a release-build

          * check instead of an assert?

          */

-        assert(gc->gc.gc_refs != 0);

+        PyObject_ASSERT(FROM_GC(gc),

+                        gc->gc.gc_refs != 0);

     }

 }

@@ -323,7 +392,9 @@ visit_decref(PyObject *op, void *data)

          * generation being collected, which can be recognized

          * because only they have positive gc_refs.

          */

-        assert(gc->gc.gc_refs != 0); /* else refcount was too small */

+        PyObject_ASSERT_WITH_MSG(FROM_GC(gc),

+                                 gc->gc.gc_refs != 0,

+                                 "refcount was too small");

         if (gc->gc.gc_refs > 0)

             gc->gc.gc_refs--;

     }

@@ -383,9 +454,10 @@ visit_reachable(PyObject *op, PyGC_Head

          * If gc_refs == GC_UNTRACKED, it must be ignored.

          */

          else {

-            assert(gc_refs > 0

-                   || gc_refs == GC_REACHABLE

-                   || gc_refs == GC_UNTRACKED);

+             PyObject_ASSERT(FROM_GC(gc),

+                             gc_refs > 0

+                             || gc_refs == GC_REACHABLE

+                             || gc_refs == GC_UNTRACKED);

          }

     }

     return 0;

@@ -427,7 +499,7 @@ move_unreachable(PyGC_Head *young, PyGC_

              */

             PyObject *op = FROM_GC(gc);

             traverseproc traverse = Py_TYPE(op)->tp_traverse;

-            assert(gc->gc.gc_refs > 0);

+            PyObject_ASSERT(op, gc->gc.gc_refs > 0);

             gc->gc.gc_refs = GC_REACHABLE;

             (void) traverse(op,

                             (visitproc)visit_reachable,

@@ -494,7 +566,8 @@ move_finalizers(PyGC_Head *unreachable,

     for (gc = unreachable->gc.gc_next; gc != unreachable; gc = next) {

         PyObject *op = FROM_GC(gc);

-        assert(IS_TENTATIVELY_UNREACHABLE(op));

+        PyObject_ASSERT(op, IS_TENTATIVELY_UNREACHABLE(op));

+

         next = gc->gc.gc_next;

         if (has_finalizer(op)) {

@@ -570,7 +643,7 @@ handle_weakrefs(PyGC_Head *unreachable,

         PyWeakReference **wrlist;

         op = FROM_GC(gc);

-        assert(IS_TENTATIVELY_UNREACHABLE(op));

+        PyObject_ASSERT(op, IS_TENTATIVELY_UNREACHABLE(op));

         next = gc->gc.gc_next;

         if (! PyType_SUPPORTS_WEAKREFS(Py_TYPE(op)))

@@ -591,9 +664,9 @@ handle_weakrefs(PyGC_Head *unreachable,

              * the callback pointer intact.  Obscure:  it also

              * changes *wrlist.

              */

-            assert(wr->wr_object == op);

+            PyObject_ASSERT(wr->wr_object, wr->wr_object == op);

             _PyWeakref_ClearRef(wr);

-            assert(wr->wr_object == Py_None);

+            PyObject_ASSERT(wr->wr_object, wr->wr_object == Py_None);

             if (wr->wr_callback == NULL)

                 continue;                       /* no callback */

@@ -627,7 +700,7 @@ handle_weakrefs(PyGC_Head *unreachable,

      */

             if (IS_TENTATIVELY_UNREACHABLE(wr))

                 continue;

-            assert(IS_REACHABLE(wr));

+            PyObject_ASSERT(op, IS_REACHABLE(wr));

             /* Create a new reference so that wr can't go away

              * before we can process it again.

@@ -636,7 +709,8 @@ handle_weakrefs(PyGC_Head *unreachable,

             /* Move wr to wrcb_to_call, for the next pass. */

             wrasgc = AS_GC(wr);

-            assert(wrasgc != next); /* wrasgc is reachable, but

+            PyObject_ASSERT(op, wrasgc != next);

+                                    /* wrasgc is reachable, but

                                        next isn't, so they can't

                                        be the same */

             gc_list_move(wrasgc, &wrcb_to_call);

@@ -652,11 +726,11 @@ handle_weakrefs(PyGC_Head *unreachable,

         gc = wrcb_to_call.gc.gc_next;

         op = FROM_GC(gc);

-        assert(IS_REACHABLE(op));

-        assert(PyWeakref_Check(op));

+        PyObject_ASSERT(op, IS_REACHABLE(op));

+        PyObject_ASSERT(op, PyWeakref_Check(op));

         wr = (PyWeakReference *)op;

         callback = wr->wr_callback;

-        assert(callback != NULL);

+        PyObject_ASSERT(op, callback != NULL);

         /* copy-paste of weakrefobject.c's handle_callback() */

         temp = PyObject_CallFunctionObjArgs(callback, wr, NULL);

@@ -759,7 +833,7 @@ delete_garbage(PyGC_Head *collectable, P

         PyGC_Head *gc = collectable->gc.gc_next;

         PyObject *op = FROM_GC(gc);

-        assert(IS_TENTATIVELY_UNREACHABLE(op));

+        PyObject_ASSERT(op, IS_TENTATIVELY_UNREACHABLE(op));

         if (debug & DEBUG_SAVEALL) {

             PyList_Append(garbage, op);

         }