Add support for weak references to code objects. This will be used by an optimization in the incoming Python 3 JIT.
Patch by Reid Kleckner!
diff --git a/Doc/library/weakref.rst b/Doc/library/weakref.rst
index 96036e9..46bfc9d 100644
--- a/Doc/library/weakref.rst
+++ b/Doc/library/weakref.rst
@@ -59,13 +59,13 @@
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 260c5f0..38b2958 100644
--- a/Include/code.h
+++ b/Include/code.h
@@ -26,6 +26,7 @@
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 4a88e60..e83a919 100644
--- a/Lib/test/test_code.py
+++ b/Lib/test/test_code.py
@@ -81,8 +81,10 @@
"""
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 @@
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 4014325..58a860c 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -552,7 +552,7 @@
# 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 03aa62d..6adc89d 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -19,6 +19,8 @@
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 6d6775a..340cef0 100644
--- a/Objects/codeobject.c
+++ b/Objects/codeobject.c
@@ -103,6 +103,7 @@
Py_INCREF(lnotab);
co->co_lnotab = lnotab;
co->co_zombieframe = NULL;
+ co->co_weakreflist = NULL;
}
return co;
}
@@ -314,6 +315,8 @@
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 @@
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 */