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https://github.com/python/cpython/commit/241ed5f2cdd525de0e136d0e3ce70d5487721c10
commit: 241ed5f2cdd525de0e136d0e3ce70d5487721c10
branch: main
author: Sam Gross <colesbury@gmail.com>
committer: colesbury <colesbury@gmail.com>
date: 2024-04-16T12:42:53-04:00
summary:

gh-117376: Make code objects use deferred reference counting (#117823)

We want code objects to use deferred reference counting in the
free-threaded build. This requires them to be tracked by the GC, so we
set `Py_TPFLAGS_HAVE_GC` in the free-threaded build, but not the default
build.

files:
M Lib/test/test_capi/test_watchers.py
M Lib/test/test_gc.py
M Objects/codeobject.c

diff --git a/Lib/test/test_capi/test_watchers.py b/Lib/test/test_capi/test_watchers.py
index ae062b1bda26b7..8e84d0077c7573 100644
--- a/Lib/test/test_capi/test_watchers.py
+++ b/Lib/test/test_capi/test_watchers.py
@@ -1,7 +1,7 @@
import unittest

from contextlib import contextmanager, ExitStack
-from test.support import catch_unraisable_exception, import_helper
+from test.support import catch_unraisable_exception, import_helper, gc_collect


# Skip this test if the _testcapi module isn't available.
@@ -372,6 +372,7 @@ def code_watcher(self, which_watcher):

def assert_event_counts(self, exp_created_0, exp_destroyed_0,
exp_created_1, exp_destroyed_1):
+ gc_collect() # code objects are collected by GC in free-threaded build
self.assertEqual(
exp_created_0, _testcapi.get_code_watcher_num_created_events(0))
self.assertEqual(
@@ -432,6 +433,7 @@ def test_dealloc_error(self):
with self.code_watcher(2):
with catch_unraisable_exception() as cm:
del co
+ gc_collect()

self.assertEqual(str(cm.unraisable.exc_value), "boom!")

diff --git a/Lib/test/test_gc.py b/Lib/test/test_gc.py
index 71c7fb0edebaa5..52681dc18cfb86 100644
--- a/Lib/test/test_gc.py
+++ b/Lib/test/test_gc.py
@@ -226,7 +226,9 @@ def test_function(self):
exec("def f(): pass\n", d)
gc.collect()
del d
- self.assertEqual(gc.collect(), 2)
+ # In the free-threaded build, the count returned by `gc.collect()`
+ # is 3 because it includes f's code object.
+ self.assertIn(gc.collect(), (2, 3))

def test_function_tp_clear_leaves_consistent_state(self):
# https://github.com/python/cpython/issues/91636
diff --git a/Objects/codeobject.c b/Objects/codeobject.c
index 825f521b439235..014632962bfcf3 100644
--- a/Objects/codeobject.c
+++ b/Objects/codeobject.c
@@ -6,6 +6,7 @@
#include "pycore_code.h" // _PyCodeConstructor
#include "pycore_frame.h" // FRAME_SPECIALS_SIZE
#include "pycore_interp.h" // PyInterpreterState.co_extra_freefuncs
+#include "pycore_object.h" // _PyObject_SetDeferredRefcount
#include "pycore_opcode_metadata.h" // _PyOpcode_Deopt, _PyOpcode_Caches
#include "pycore_opcode_utils.h" // RESUME_AT_FUNC_START
#include "pycore_pystate.h" // _PyInterpreterState_GET()
@@ -557,13 +558,22 @@ _PyCode_New(struct _PyCodeConstructor *con)
}

Py_ssize_t size = PyBytes_GET_SIZE(con->code) / sizeof(_Py_CODEUNIT);
- PyCodeObject *co = PyObject_NewVar(PyCodeObject, &PyCode_Type, size);
+ PyCodeObject *co;
+#ifdef Py_GIL_DISABLED
+ co = PyObject_GC_NewVar(PyCodeObject, &PyCode_Type, size);
+#else
+ co = PyObject_NewVar(PyCodeObject, &PyCode_Type, size);
+#endif
if (co == NULL) {
Py_XDECREF(replacement_locations);
PyErr_NoMemory();
return NULL;
}
init_code(co, con);
+#ifdef Py_GIL_DISABLED
+ _PyObject_SetDeferredRefcount((PyObject *)co);
+ _PyObject_GC_TRACK(co);
+#endif
Py_XDECREF(replacement_locations);
return co;
}
@@ -1710,6 +1720,10 @@ code_dealloc(PyCodeObject *co)
}
Py_SET_REFCNT(co, 0);

+#ifdef Py_GIL_DISABLED
+ PyObject_GC_UnTrack(co);
+#endif
+
_PyFunction_ClearCodeByVersion(co->co_version);
if (co->co_extra != NULL) {
PyInterpreterState *interp = _PyInterpreterState_GET();
@@ -1752,6 +1766,15 @@ code_dealloc(PyCodeObject *co)
PyObject_Free(co);
}

+#ifdef Py_GIL_DISABLED
+static int
+code_traverse(PyCodeObject *co, visitproc visit, void *arg)
+{
+ Py_VISIT(co->co_consts);
+ return 0;
+}
+#endif
+
static PyObject *
code_repr(PyCodeObject *co)
{
@@ -2196,9 +2219,17 @@ PyTypeObject PyCode_Type = {
PyObject_GenericGetAttr, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
+#ifdef Py_GIL_DISABLED
+ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC, /* tp_flags */
+#else
Py_TPFLAGS_DEFAULT, /* tp_flags */
+#endif
code_new__doc__, /* tp_doc */
+#ifdef Py_GIL_DISABLED
+ (traverseproc)code_traverse, /* tp_traverse */
+#else
0, /* tp_traverse */
+#endif
0, /* tp_clear */
code_richcompare, /* tp_richcompare */
offsetof(PyCodeObject, co_weakreflist), /* tp_weaklistoffset */

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