Use a managed weakref list for the _io types

Replace the explicit weakreflist field of the _io types with
Py_TPFLAGS_MANAGED_WEAKREF, inherited from _IOBase, so the weakref
list lives in the pre-header like the managed dict.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

Author: eendebakpt

Lib/test/test_io/test_memoryio.py

@@ -1038,12 +1038,12 @@ def test_setstate(self):
     @support.cpython_only
     def test_sizeof(self):
         if support.Py_GIL_DISABLED:
-            basesize = support.calcobjsize('P2nPni')
+            basesize = support.calcobjsize('P2nni')
         else:
-            basesize = support.calcobjsize('P2nPn')
+            basesize = support.calcobjsize('P2nn')
         check = self.check_sizeof
         self.assertEqual(object.__sizeof__(io.BytesIO()), basesize)
-        # sys.getsizeof() includes the managed dict pre-header
+        # sys.getsizeof() includes the managed dict and weakref pre-header
         basesize += 2 * struct.calcsize('P')
         check(io.BytesIO(), basesize )
         n = 1000  # use a variable to prevent constant folding

Modules/_io/bufferedio.c

@@ -9,11 +9,11 @@
 
 #include "Python.h"
 #include "pycore_call.h"                // _PyObject_CallNoArgs()
+#include "pycore_critical_section.h"    // _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED()
 #include "pycore_fileutils.h"           // _PyFile_Flush
 #include "pycore_object.h"              // _PyObject_GC_UNTRACK()
 #include "pycore_pyerrors.h"            // _Py_FatalErrorFormat()
 #include "pycore_pylifecycle.h"         // _Py_IsInterpreterFinalizing()
-#include "pycore_weakref.h"             // FT_CLEAR_WEAKREFS()
 
 #include "_iomodule.h"
 
@@ -260,7 +260,6 @@ typedef struct {
     Py_ssize_t buffer_size;
     Py_ssize_t buffer_mask;
 
-    PyObject *weakreflist;
 } buffered;
 
 #define buffered_CAST(op)   ((buffered *)(op))
@@ -430,7 +429,7 @@ buffered_dealloc(PyObject *op)
         return;
     _PyObject_GC_UNTRACK(self);
     self->ok = 0;
-    FT_CLEAR_WEAKREFS(op, self->weakreflist);
+    PyObject_ClearWeakRefs(op);
     if (self->buffer) {
         PyMem_Free(self->buffer);
         self->buffer = NULL;
@@ -2248,7 +2247,6 @@ typedef struct {
     PyObject_HEAD
     buffered *reader;
     buffered *writer;
-    PyObject *weakreflist;
 } rwpair;
 
 #define rwpair_CAST(op) ((rwpair *)(op))
@@ -2327,7 +2325,7 @@ bufferedrwpair_dealloc(PyObject *op)
     rwpair *self = rwpair_CAST(op);
     PyTypeObject *tp = Py_TYPE(self);
     _PyObject_GC_UNTRACK(self);
-    FT_CLEAR_WEAKREFS(op, self->weakreflist);
+    PyObject_ClearWeakRefs(op);
     (void)bufferedrwpair_clear(op);
     tp->tp_free(self);
     Py_DECREF(tp);
@@ -2634,7 +2632,6 @@ static PyMethodDef bufferedreader_methods[] = {
 static PyMemberDef bufferedreader_members[] = {
     {"raw", _Py_T_OBJECT, offsetof(buffered, raw), Py_READONLY},
     {"_finalizing", Py_T_BOOL, offsetof(buffered, finalizing), 0},
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(buffered, weakreflist), Py_READONLY},
     {NULL}
 };
 
@@ -2692,7 +2689,6 @@ static PyMethodDef bufferedwriter_methods[] = {
 static PyMemberDef bufferedwriter_members[] = {
     {"raw", _Py_T_OBJECT, offsetof(buffered, raw), Py_READONLY},
     {"_finalizing", Py_T_BOOL, offsetof(buffered, finalizing), 0},
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(buffered, weakreflist), Py_READONLY},
     {NULL}
 };
 
@@ -2745,7 +2741,6 @@ static PyMethodDef bufferedrwpair_methods[] = {
 };
 
 static PyMemberDef bufferedrwpair_members[] = {
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(rwpair, weakreflist), Py_READONLY},
     {NULL}
 };
 
@@ -2807,7 +2802,6 @@ static PyMethodDef bufferedrandom_methods[] = {
 static PyMemberDef bufferedrandom_members[] = {
     {"raw", _Py_T_OBJECT, offsetof(buffered, raw), Py_READONLY},
     {"_finalizing", Py_T_BOOL, offsetof(buffered, finalizing), 0},
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(buffered, weakreflist), Py_READONLY},
     {NULL}
 };
 

Modules/_io/bytesio.c

@@ -5,7 +5,6 @@
 #include "pycore_object.h"
 #include "pycore_pyatomic_ft_wrappers.h"
 #include "pycore_sysmodule.h"         // _PySys_GetSizeOf()
-#include "pycore_weakref.h"           // FT_CLEAR_WEAKREFS()
 
 #include <stddef.h>                   // offsetof()
 #include "_iomodule.h"
@@ -21,7 +20,6 @@ typedef struct {
     PyObject *buf;
     Py_ssize_t pos;
     Py_ssize_t string_size;
-    PyObject *weakreflist;
     Py_ssize_t exports;
 #ifdef Py_GIL_DISABLED
     int buf_shared;
@@ -1094,7 +1092,7 @@ bytesio_dealloc(PyObject *op)
     }
     Py_CLEAR(self->buf);
     PyObject_ClearManagedDict(op);
-    FT_CLEAR_WEAKREFS(op, self->weakreflist);
+    PyObject_ClearWeakRefs(op);
     tp->tp_free(self);
     Py_DECREF(tp);
 }
@@ -1242,7 +1240,6 @@ static struct PyMethodDef bytesio_methods[] = {
 };
 
 static PyMemberDef bytesio_members[] = {
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(bytesio, weakreflist), Py_READONLY},
     {NULL}
 };
 

Modules/_io/fileio.c

@@ -4,7 +4,6 @@
 #include "pycore_fileutils.h"     // _Py_BEGIN_SUPPRESS_IPH
 #include "pycore_object.h"        // _PyObject_GC_UNTRACK()
 #include "pycore_pyerrors.h"      // _PyErr_ChainExceptions1()
-#include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
 
 #include <stdbool.h>              // bool
 #ifdef HAVE_UNISTD_H
@@ -80,7 +79,6 @@ typedef struct {
        modified outside of the fileio object / Python (ex. gh-90102, GH-121941,
        gh-109523). */
     struct _Py_stat_struct *stat_atopen;
-    PyObject *weakreflist;
 } fileio;
 
 #define PyFileIO_Check(state, op) (PyObject_TypeCheck((op), state->PyFileIO_Type))
@@ -219,7 +217,6 @@ fileio_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     self->truncate = 0;
     self->stat_atopen = NULL;
     self->closefd = 1;
-    self->weakreflist = NULL;
     return (PyObject *) self;
 }
 
@@ -581,7 +578,7 @@ fileio_dealloc(PyObject *op)
         PyMem_Free(self->stat_atopen);
         self->stat_atopen = NULL;
     }
-    FT_CLEAR_WEAKREFS(op, self->weakreflist);
+    PyObject_ClearWeakRefs(op);
     (void)fileio_clear(op);
 
     PyTypeObject *tp = Py_TYPE(op);
@@ -1363,7 +1360,6 @@ static PyGetSetDef fileio_getsetlist[] = {
 
 static PyMemberDef fileio_members[] = {
     {"_finalizing", Py_T_BOOL, offsetof(fileio, finalizing), 0},
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(fileio, weakreflist), Py_READONLY},
     {NULL}
 };
 

Modules/_io/iobase.c

@@ -14,7 +14,6 @@
 #include "pycore_long.h"          // _PyLong_GetOne()
 #include "pycore_object.h"        // _PyType_HasFeature()
 #include "pycore_pyerrors.h"      // _PyErr_ChainExceptions1()
-#include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
 
 #include <stddef.h>               // offsetof()
 #include "_iomodule.h"
@@ -33,7 +32,6 @@ class _io._RawIOBase "PyObject *" "clinic_state()->PyRawIOBase_Type"
 typedef struct {
     PyObject_HEAD
 
-    PyObject *weakreflist;
 } iobase;
 
 #define iobase_CAST(op) ((iobase *)(op))
@@ -413,7 +411,7 @@ iobase_dealloc(PyObject *op)
     }
     PyTypeObject *tp = Py_TYPE(self);
     _PyObject_GC_UNTRACK(self);
-    FT_CLEAR_WEAKREFS(op, self->weakreflist);
+    PyObject_ClearWeakRefs(op);
     PyObject_ClearManagedDict(op);
     tp->tp_free(self);
     Py_DECREF(tp);
@@ -905,7 +903,6 @@ static PyGetSetDef iobase_getset[] = {
 };
 
 static struct PyMemberDef iobase_members[] = {
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(iobase, weakreflist), Py_READONLY},
     {NULL},
 };
 
@@ -928,7 +925,8 @@ PyType_Spec _Py_iobase_spec = {
     .name = "_io._IOBase",
     .basicsize = sizeof(iobase),
     .flags = (Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC |
-              Py_TPFLAGS_IMMUTABLETYPE | Py_TPFLAGS_MANAGED_DICT),
+              Py_TPFLAGS_IMMUTABLETYPE | Py_TPFLAGS_MANAGED_DICT |
+              Py_TPFLAGS_MANAGED_WEAKREF),
     .slots = iobase_slots,
 };
 

Modules/_io/stringio.c

@@ -1,8 +1,8 @@
 #include "Python.h"
 #include <stddef.h>               // offsetof()
+#include "pycore_critical_section.h"  // _Py_CRITICAL_SECTION_ASSERT_OBJECT_LOCKED()
 #include "pycore_object.h"
 #include "pycore_unicodeobject.h" // _PyUnicode_ResizeCompact()
-#include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
 #include "_iomodule.h"
 
 /* Implementation note: the buffer is always at least one character longer
@@ -42,7 +42,6 @@ typedef struct {
     PyObject *readnl;
     PyObject *writenl;
 
-    PyObject *weakreflist;
     _PyIO_State *module_state;
 } stringio;
 
@@ -701,7 +700,7 @@ stringio_dealloc(PyObject *op)
     }
     PyUnicodeWriter_Discard(self->writer);
     (void)stringio_clear(op);
-    FT_CLEAR_WEAKREFS(op, self->weakreflist);
+    PyObject_ClearWeakRefs(op);
     tp->tp_free(self);
     Py_DECREF(tp);
 }
@@ -1144,7 +1143,6 @@ static PyGetSetDef stringio_getset[] = {
 };
 
 static struct PyMemberDef stringio_members[] = {
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(stringio, weakreflist), Py_READONLY},
     {NULL},
 };
 

Modules/_io/textio.c

@@ -16,7 +16,6 @@
 #include "pycore_pyerrors.h"      // _PyErr_ChainExceptions1()
 #include "pycore_pystate.h"       // _PyInterpreterState_GET()
 #include "pycore_unicodeobject.h" // _PyUnicode_AsASCIIString()
-#include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
 
 #include "_iomodule.h"
 
@@ -731,7 +730,6 @@ struct textio
     /* Cache raw object if it's a FileIO object */
     PyObject *raw;
 
-    PyObject *weakreflist;
 
     _PyIO_State *state;
 };
@@ -1555,7 +1553,7 @@ textiowrapper_dealloc(PyObject *op)
         return;
     self->ok = 0;
     _PyObject_GC_UNTRACK(self);
-    FT_CLEAR_WEAKREFS(op, self->weakreflist);
+    PyObject_ClearWeakRefs(op);
     (void)textiowrapper_clear(op);
     tp->tp_free(self);
     Py_DECREF(tp);
@@ -3536,7 +3534,6 @@ static PyMemberDef textiowrapper_members[] = {
     {"line_buffering", Py_T_BOOL, offsetof(textio, line_buffering), Py_READONLY},
     {"write_through", Py_T_BOOL, offsetof(textio, write_through), Py_READONLY},
     {"_finalizing", Py_T_BOOL, offsetof(textio, finalizing), 0},
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(textio, weakreflist), Py_READONLY},
     {NULL}
 };
 

Modules/_io/winconsoleio.c

@@ -10,7 +10,6 @@
 #include "pycore_fileutils.h"     // _Py_BEGIN_SUPPRESS_IPH
 #include "pycore_object.h"        // _PyObject_GC_UNTRACK()
 #include "pycore_pyerrors.h"      // _PyErr_ChainExceptions1()
-#include "pycore_weakref.h"       // FT_CLEAR_WEAKREFS()
 
 #ifdef HAVE_WINDOWS_CONSOLE_IO
 
@@ -216,7 +215,6 @@ typedef struct {
     unsigned int closefd : 1;
     char finalizing;
     unsigned int blksize;
-    PyObject *weakreflist;
     char buf[SMALLBUF];
     wchar_t wbuf;
 } winconsoleio;
@@ -299,7 +297,6 @@ winconsoleio_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         self->writable = 0;
         self->closefd = 0;
         self->blksize = 0;
-        self->weakreflist = NULL;
     }
 
     return (PyObject *) self;
@@ -516,7 +513,7 @@ winconsoleio_dealloc(PyObject *op)
     if (_PyIOBase_finalize(op) < 0)
         return;
     _PyObject_GC_UNTRACK(self);
-    FT_CLEAR_WEAKREFS(op, self->weakreflist);
+    PyObject_ClearWeakRefs(op);
     PyObject_ClearManagedDict(op);
     tp->tp_free(self);
     Py_DECREF(tp);
@@ -1255,7 +1252,6 @@ static PyGetSetDef winconsoleio_getsetlist[] = {
 static PyMemberDef winconsoleio_members[] = {
     {"_blksize", Py_T_UINT, offsetof(winconsoleio, blksize), 0},
     {"_finalizing", Py_T_BOOL, offsetof(winconsoleio, finalizing), 0},
-    {"__weaklistoffset__", Py_T_PYSSIZET, offsetof(winconsoleio, weakreflist), Py_READONLY},
     {NULL}
 };