From e012b8baed796615cc92c2785361e7a12a601f96 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Sat, 9 Jul 2022 11:10:41 -0600
Subject: [PATCH 1/7] Store tp_weaklist on the interpreter state for static
builtin types.
---
Include/cpython/object.h | 2 +-
Include/internal/pycore_object.h | 6 ++++++
Include/internal/pycore_typeobject.h | 5 +++++
Objects/typeobject.c | 5 +++++
4 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/Include/cpython/object.h b/Include/cpython/object.h
index 1ca1a576fb2329..026803320a11b2 100644
--- a/Include/cpython/object.h
+++ b/Include/cpython/object.h
@@ -219,7 +219,7 @@ struct _typeobject {
PyObject *tp_mro; /* method resolution order */
PyObject *tp_cache;
PyObject *tp_subclasses;
- PyObject *tp_weaklist;
+ PyObject *tp_weaklist; /* not used for static builtin types */
destructor tp_del;
/* Type attribute cache version tag. Added in version 2.6 */
diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
index c7490799d816af..198486c9451814 100644
--- a/Include/internal/pycore_object.h
+++ b/Include/internal/pycore_object.h
@@ -220,6 +220,12 @@ extern void _Py_PrintReferenceAddresses(FILE *);
static inline PyObject **
_PyObject_GET_WEAKREFS_LISTPTR(PyObject *op)
{
+ if (PyType_Check(op) &&
+ ((PyTypeObject *)op)->tp_flags & _Py_TPFLAGS_STATIC_BUILTIN) {
+ static_builtin_state *state = _PyStaticType_GetState(
+ (PyTypeObject *)op);
+ return &state->tp_weaklist;
+ }
Py_ssize_t offset = Py_TYPE(op)->tp_weaklistoffset;
return (PyObject **)((char *)op + offset);
}
diff --git a/Include/internal/pycore_typeobject.h b/Include/internal/pycore_typeobject.h
index dc1c02ba412809..abea8727a1cbdc 100644
--- a/Include/internal/pycore_typeobject.h
+++ b/Include/internal/pycore_typeobject.h
@@ -45,6 +45,11 @@ struct type_cache {
typedef struct {
PyTypeObject *type;
+ /* We never clean up weakrefs for static builtin types since
+ they will effectively never get triggered. However, there
+ are also some diagnostic uses for the list of weakrefs,
+ so we still keep it. */
+ PyObject *tp_weaklist;
} static_builtin_state;
struct types_state {
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 9eb2390118d097..bd69c32cc71dbd 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -127,6 +127,8 @@ static_builtin_state_init(PyTypeObject *self)
static_builtin_state *state = static_builtin_state_get(interp, self);
state->type = self;
+ /* state->tp_weaklist is left NULL until insert_head() or insert_after()
+ (in weakrefobject.c) sets it. */
}
static void
@@ -138,6 +140,7 @@ static_builtin_state_clear(PyTypeObject *self)
static_builtin_state *state = static_builtin_state_get(interp, self);
state->type = NULL;
+ /* state->tp_weaklist should already have been cleared out. */
static_builtin_index_clear(self);
assert(interp->types.num_builtins_initialized > 0);
@@ -502,6 +505,8 @@ static PyMemberDef type_members[] = {
{"__basicsize__", T_PYSSIZET, offsetof(PyTypeObject,tp_basicsize),READONLY},
{"__itemsize__", T_PYSSIZET, offsetof(PyTypeObject, tp_itemsize), READONLY},
{"__flags__", T_ULONG, offsetof(PyTypeObject, tp_flags), READONLY},
+ /* Note that this value is misleading for static builtin types,
+ since the memory at this offset will always be NULL. */
{"__weakrefoffset__", T_PYSSIZET,
offsetof(PyTypeObject, tp_weaklistoffset), READONLY},
{"__base__", T_OBJECT, offsetof(PyTypeObject, tp_base), READONLY},
From 8116dde0dafed1b486fdea12081519d5bdaffa75 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 26 Jul 2022 16:08:07 -0600
Subject: [PATCH 2/7] Factor out _PyStaticType_GET_WEAKREFS_LISTPTR().
---
Include/internal/pycore_object.h | 2 +-
Include/internal/pycore_typeobject.h | 7 +++++++
2 files changed, 8 insertions(+), 1 deletion(-)
diff --git a/Include/internal/pycore_object.h b/Include/internal/pycore_object.h
index 198486c9451814..9f061d8b08772c 100644
--- a/Include/internal/pycore_object.h
+++ b/Include/internal/pycore_object.h
@@ -224,7 +224,7 @@ _PyObject_GET_WEAKREFS_LISTPTR(PyObject *op)
((PyTypeObject *)op)->tp_flags & _Py_TPFLAGS_STATIC_BUILTIN) {
static_builtin_state *state = _PyStaticType_GetState(
(PyTypeObject *)op);
- return &state->tp_weaklist;
+ return _PyStaticType_GET_WEAKREFS_LISTPTR(state);
}
Py_ssize_t offset = Py_TYPE(op)->tp_weaklistoffset;
return (PyObject **)((char *)op + offset);
diff --git a/Include/internal/pycore_typeobject.h b/Include/internal/pycore_typeobject.h
index abea8727a1cbdc..a6c6304d51179b 100644
--- a/Include/internal/pycore_typeobject.h
+++ b/Include/internal/pycore_typeobject.h
@@ -52,6 +52,13 @@ typedef struct {
PyObject *tp_weaklist;
} static_builtin_state;
+static inline PyObject **
+_PyStaticType_GET_WEAKREFS_LISTPTR(static_builtin_state *state)
+{
+ assert(state != NULL);
+ return &state->tp_weaklist;
+}
+
struct types_state {
struct type_cache type_cache;
size_t num_builtins_initialized;
From f7d27feb02156d6238e629333f2b1bd64008e146 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Tue, 26 Jul 2022 16:19:15 -0600
Subject: [PATCH 3/7] Add _PyStaticType_ClearWeakRefs().
---
Include/internal/pycore_typeobject.h | 1 +
Objects/typeobject.c | 3 ++-
Objects/weakrefobject.c | 16 ++++++++++++++++
3 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/Include/internal/pycore_typeobject.h b/Include/internal/pycore_typeobject.h
index a6c6304d51179b..4f9d6b1c4d4ba2 100644
--- a/Include/internal/pycore_typeobject.h
+++ b/Include/internal/pycore_typeobject.h
@@ -70,6 +70,7 @@ extern PyStatus _PyTypes_InitSlotDefs(void);
extern int _PyStaticType_InitBuiltin(PyTypeObject *type);
extern static_builtin_state * _PyStaticType_GetState(PyTypeObject *);
+extern void _PyStaticType_ClearWeakRefs(PyTypeObject *type);
extern void _PyStaticType_Dealloc(PyTypeObject *type);
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index bd69c32cc71dbd..e4adf1c4e12f8c 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -140,7 +140,7 @@ static_builtin_state_clear(PyTypeObject *self)
static_builtin_state *state = static_builtin_state_get(interp, self);
state->type = NULL;
- /* state->tp_weaklist should already have been cleared out. */
+ assert(state->tp_weaklist == NULL); // It was already cleared out.
static_builtin_index_clear(self);
assert(interp->types.num_builtins_initialized > 0);
@@ -4358,6 +4358,7 @@ _PyStaticType_Dealloc(PyTypeObject *type)
type->tp_flags &= ~Py_TPFLAGS_READY;
if (type->tp_flags & _Py_TPFLAGS_STATIC_BUILTIN) {
+ _PyStaticType_ClearWeakRefs(type);
static_builtin_state_clear(type);
/* We leave _Py_TPFLAGS_STATIC_BUILTIN set on tp_flags. */
}
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index 2b4361e63ca413..e15c8f4fabbb9a 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -1018,3 +1018,19 @@ PyObject_ClearWeakRefs(PyObject *object)
PyErr_Restore(err_type, err_value, err_tb);
}
}
+
+/* This function is called by _PyStaticType_Dealloc() to clear weak references.
+ *
+ * This is called at the end of runtime finalization, so we can just
+ * wipe out the type's weaklist. We don't bother with callbacks
+ * or anything else.
+ */
+void
+_PyStaticType_ClearWeakRefs(PyTypeObject *type)
+{
+ static_builtin_state *state = _PyStaticType_GetState(type);
+ PyObject **list = _PyStaticType_GET_WEAKREFS_LISTPTR(state);
+ while (*list != NULL) {
+ clear_weakref((PyWeakReference *)*list);
+ }
+}
From 8a5b5bcb81ec4c06fa3cccd135a0f60c5041a250 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Wed, 27 Jul 2022 14:46:11 -0600
Subject: [PATCH 4/7] Add a comment about how _PyStaticType_ClearWeakRefs()
loops.
---
Objects/weakrefobject.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index e15c8f4fabbb9a..17e1e9cdc814fa 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -1031,6 +1031,9 @@ _PyStaticType_ClearWeakRefs(PyTypeObject *type)
static_builtin_state *state = _PyStaticType_GetState(type);
PyObject **list = _PyStaticType_GET_WEAKREFS_LISTPTR(state);
while (*list != NULL) {
+ /* Note that clear_weakref() pops the first ref off the type's
+ weaklist before clearing its wr_object and wr_callback.
+ That is how we're able to loop over the list. */
clear_weakref((PyWeakReference *)*list);
}
}
From 69f9be87d6cac95c4c34690332fb7eadf46cd664 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Thu, 28 Jul 2022 18:10:48 -0600
Subject: [PATCH 5/7] Document the change.
---
Doc/c-api/typeobj.rst | 7 +++++++
Doc/whatsnew/3.12.rst | 7 +++++++
2 files changed, 14 insertions(+)
diff --git a/Doc/c-api/typeobj.rst b/Doc/c-api/typeobj.rst
index a331e9c1885092..7514801f2d4d59 100644
--- a/Doc/c-api/typeobj.rst
+++ b/Doc/c-api/typeobj.rst
@@ -1942,6 +1942,13 @@ and :c:type:`PyType_Type` effectively act as defaults.)
Weak reference list head, for weak references to this type object. Not
inherited. Internal use only.
+ .. versionchanged:: 3.12
+
+ Internals detail: For the static builtin types this is always ``NULL``,
+ even if weakrefs are added. Instead, the weakrefs for each are stored
+ on ``PyInterpreterState``. Use the public C-API or the internal
+ ``_PyObject_GET_WEAKREFS_LISTPTR()`` macro to avoid the distinction.
+
**Inheritance:**
This field is not inherited.
diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst
index 03020559362b1d..40f721ae2765cb 100644
--- a/Doc/whatsnew/3.12.rst
+++ b/Doc/whatsnew/3.12.rst
@@ -413,6 +413,13 @@ Porting to Python 3.12
``Py_UNICODE*`` based format (e.g. ``u``, ``Z``) anymore. Please migrate
to other formats for Unicode like ``s``, ``z``, ``es``, and ``U``.
+* ``tp_weaklist`` for ``PyType_Type`` is always ``NULL`` for all static
+ builtin types. This is an internal-only field on ``PyTypeObject``
+ but we're pointing out the change in case someone happens to be
+ accessing the field directly anyway. To avoid breakage, consider
+ using the existing public C-API instead, or, if necessary, the
+ (internal-only) ``_PyObject_GET_WEAKREFS_LISTPTR()`` macro.
+
Deprecated
----------
From d63e1662442a030cce336c8aa3675d3978e90ad9 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Thu, 28 Jul 2022 18:22:48 -0600
Subject: [PATCH 6/7] Update Doc/whatsnew/3.12.rst
---
Doc/whatsnew/3.12.rst | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst
index 40f721ae2765cb..67cf32b99bb56e 100644
--- a/Doc/whatsnew/3.12.rst
+++ b/Doc/whatsnew/3.12.rst
@@ -413,8 +413,8 @@ Porting to Python 3.12
``Py_UNICODE*`` based format (e.g. ``u``, ``Z``) anymore. Please migrate
to other formats for Unicode like ``s``, ``z``, ``es``, and ``U``.
-* ``tp_weaklist`` for ``PyType_Type`` is always ``NULL`` for all static
- builtin types. This is an internal-only field on ``PyTypeObject``
+* ``tp_weaklist`` for all static builtin types is always ``NULL``.
+ This is an internal-only field on ``PyTypeObject``
but we're pointing out the change in case someone happens to be
accessing the field directly anyway. To avoid breakage, consider
using the existing public C-API instead, or, if necessary, the
From 7af915fd39ee0fb6343404132081f761ade1d504 Mon Sep 17 00:00:00 2001
From: Eric Snow <ericsnowcurrently@gmail.com>
Date: Thu, 28 Jul 2022 18:31:02 -0600
Subject: [PATCH 7/7] Fix a typo.
---
Doc/whatsnew/3.12.rst | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst
index 67cf32b99bb56e..0c53bc0c1111d7 100644
--- a/Doc/whatsnew/3.12.rst
+++ b/Doc/whatsnew/3.12.rst
@@ -414,7 +414,7 @@ Porting to Python 3.12
to other formats for Unicode like ``s``, ``z``, ``es``, and ``U``.
* ``tp_weaklist`` for all static builtin types is always ``NULL``.
- This is an internal-only field on ``PyTypeObject``
+ This is an internal-only field on ``PyTypeObject``
but we're pointing out the change in case someone happens to be
accessing the field directly anyway. To avoid breakage, consider
using the existing public C-API instead, or, if necessary, the