Add support for weak references to code objects. This will be used by an optimization...

Patch by Reid Kleckner!

diff --git a/Doc/library/weakref.rst b/Doc/library/weakref.rst
index 96036e99c1a96db2a05ab08f1e00769c7071e5b4..46bfc9d5a5d200c5260182e7ae1454d7e4ea2bcf 100644 (file)
--- a/Doc/library/weakref.rst
+++ b/Doc/library/weakref.rst
@@ -59,13 +59,13 @@ Not all objects can be weakly referenced; those objects which can include class
 instances, functions written in Python (but not in C), methods (both bound and
 unbound), sets, frozensets, file objects, :term:`generator`\s, type objects,
 :class:`DBcursor` objects from the :mod:`bsddb` module, sockets, arrays, deques,
-and regular expression pattern objects.
+regular expression pattern objects, and code objects.
 
 .. versionchanged:: 2.4
    Added support for files, sockets, arrays, and patterns.
 
 .. versionchanged:: 2.7
-   Added support for thread.lock and threading.Lock.
+   Added support for thread.lock, threading.Lock, and code objects.
 
 Several built-in types such as :class:`list` and :class:`dict` do not directly
 support weak references but can add support through subclassing::

diff --git a/Include/code.h b/Include/code.h
index 260c5f05f7d1c5cabc498dd02a1445729a64d219..38b2958046af1571b207eb97e2dfb5a69b56a28e 100644 (file)
--- a/Include/code.h
+++ b/Include/code.h
@@ -26,6 +26,7 @@ typedef struct {
     PyObject *co_lnotab;       /* string (encoding addr<->lineno mapping) See
                                   Objects/lnotab_notes.txt for details. */
     void *co_zombieframe;     /* for optimization only (see frameobject.c) */
+    PyObject *co_weakreflist;   /* to support weakrefs to code objects */
 } PyCodeObject;
 
 /* Masks for co_flags above */

diff --git a/Lib/test/test_code.py b/Lib/test/test_code.py
index 4a88e60d1d91ee054470c674a18dbb2ded242738..e83a919bcf5b960157d2ba93bb46a876fff74fd3 100644 (file)
--- a/Lib/test/test_code.py
+++ b/Lib/test/test_code.py
@@ -81,8 +81,10 @@ consts: ("'doc string'", 'None')
 """
 
 import unittest
+import weakref
 import _testcapi
 
+
 def consts(t):
     """Yield a doctest-safe sequence of object reprs."""
     for elt in t:
@@ -109,12 +111,37 @@ class CodeTest(unittest.TestCase):
         self.assertEquals(co.co_firstlineno, 15)
 
 
+class CodeWeakRefTest(unittest.TestCase):
+
+    def test_basic(self):
+        # Create a code object in a clean environment so that we know we have
+        # the only reference to it left.
+        namespace = {}
+        exec "def f(): pass" in globals(), namespace
+        f = namespace["f"]
+        del namespace
+
+        self.called = False
+        def callback(code):
+            self.called = True
+
+        # f is now the last reference to the function, and through it, the code
+        # object.  While we hold it, check that we can create a weakref and
+        # deref it.  Then delete it, and check that the callback gets called and
+        # the reference dies.
+        coderef = weakref.ref(f.__code__, callback)
+        self.assertTrue(bool(coderef()))
+        del f
+        self.assertFalse(bool(coderef()))
+        self.assertTrue(self.called)
+
+
 def test_main(verbose=None):
     from test.test_support import run_doctest, run_unittest
     from test import test_code
     run_doctest(test_code, verbose)
-    run_unittest(CodeTest)
+    run_unittest(CodeTest, CodeWeakRefTest)
 
 
-if __name__ == '__main__':
+if __name__ == "__main__":
     test_main()

diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 40143254d525e4635fbe48148cfe9bd2c577707f..58a860c3ee31595b836f30835f4c91e740b83f95 100644 (file)
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -552,7 +552,7 @@ class SizeofTest(unittest.TestCase):
         # complex
         check(complex(0,1), size(h + '2d'))
         # code
-        check(get_cell().func_code, size(h + '4i8Pi2P'))
+        check(get_cell().func_code, size(h + '4i8Pi3P'))
         # BaseException
         check(BaseException(), size(h + '3P'))
         # UnicodeEncodeError

diff --git a/Misc/NEWS b/Misc/NEWS
index 03aa62d12a28406a9b8c053bc5d0c5c6c1569ac1..6adc89d7a29c00c4ce845f1e2acb116858f246d9 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -19,6 +19,8 @@ Core and Builtins
   printed and Python exits.  Initialize the GIL before importing the site
   module.
 
+- Code objects now support weak references.
+
 Library
 -------
 

diff --git a/Objects/codeobject.c b/Objects/codeobject.c
index 6d6775a48dbbcf5000b51d98e0734ce09e671914..340cef01da821babb0344992d6edc0d12f14afd2 100644 (file)
--- a/Objects/codeobject.c
+++ b/Objects/codeobject.c
@@ -103,6 +103,7 @@ PyCode_New(int argcount, int nlocals, int stacksize, int flags,
                Py_INCREF(lnotab);
                co->co_lnotab = lnotab;
                 co->co_zombieframe = NULL;
+               co->co_weakreflist = NULL;
        }
        return co;
 }
@@ -314,6 +315,8 @@ code_dealloc(PyCodeObject *co)
        Py_XDECREF(co->co_lnotab);
         if (co->co_zombieframe != NULL)
                 PyObject_GC_Del(co->co_zombieframe);
+       if (co->co_weakreflist != NULL)
+               PyObject_ClearWeakRefs((PyObject*)co);
        PyObject_DEL(co);
 }
 
@@ -490,8 +493,8 @@ PyTypeObject PyCode_Type = {
        code_doc,                       /* tp_doc */
        0,                              /* tp_traverse */
        0,                              /* tp_clear */
-       code_richcompare,                               /* tp_richcompare */
-       0,                              /* tp_weaklistoffset */
+       code_richcompare,               /* tp_richcompare */
+       offsetof(PyCodeObject, co_weakreflist), /* tp_weaklistoffset */
        0,                              /* tp_iter */
        0,                              /* tp_iternext */
        0,                              /* tp_methods */