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bpo-32388: Remove cross-version binary compatibility requirement in tp_flags
It is now allowed to add new fields at the end of the PyTypeObject struct (and even in the middle, if we are so inclined) in feature releases without having to allocate a dedicated compatibility flag in tp_flags. This will reduce the risk of running out of bits in the 32-bit tp_flags value.
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-52
lines changed

18 files changed

+52
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lines changed

‎Doc/c-api/typeobj.rst‎

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@@ -1073,6 +1073,11 @@ and :c:type:`PyType_Type` effectively act as defaults.)
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.. versionadded:: 3.4
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.. deprecated:: 3.8
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This flag isn't necessary anymore, as the interpreter assumes the
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:c:member:`~PyTypeObject.tp_finalize` slot is always present in the
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type structure.
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.. c:member:: const char* PyTypeObject.tp_doc
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‎Doc/whatsnew/3.8.rst‎

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@@ -1019,6 +1019,13 @@ Changes in the C API
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(Contributed by Eddie Elizondo in :issue:`35810`.)
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* The interpreter does not pretend to support binary compatibility of
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extension types accross feature releases, anymore. A :c:type:`PyTypeObject`
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exported by a third-party extension module is supposed to have all the
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slots expected in the current Python version, including
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:c:member:`~PyTypeObject.tp_finalize` (:const:`Py_TPFLAGS_HAVE_FINALIZE`
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is not checked anymore before reading :c:member:`~PyTypeObject.tp_finalize`).
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CPython bytecode changes
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------------------------

‎Include/object.h‎

Lines changed: 12 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -263,17 +263,14 @@ PyAPI_FUNC(void) Py_ReprLeave(PyObject *);
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#define Py_PRINT_RAW 1 /* No string quotes etc. */
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/*
266-
`Type flags (tp_flags)
266+
Type flags (tp_flags)
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268-
These flags are used to extend the type structure in a backwards-compatible
269-
fashion. Extensions can use the flags to indicate (and test) when a given
270-
type structure contains a new feature. The Python core will use these when
271-
introducing new functionality between major revisions (to avoid mid-version
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changes in the PYTHON_API_VERSION).
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These flags are used to change expected features and behavior for a
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particular type.
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Arbitration of the flag bit positions will need to be coordinated among
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all extension writers who publicly release their extensions (this will
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be fewer than you might expect!)..
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be fewer than you might expect!).
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Most flags were removed as of Python 3.0 to make room for new flags. (Some
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flags are not for backwards compatibility but to indicate the presence of an
@@ -297,7 +294,7 @@ given type object has a specified feature.
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/* Set while the type is being 'readied', to prevent recursive ready calls */
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#define Py_TPFLAGS_READYING (1UL << 13)
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/* Objects support garbage collection (see objimp.h) */
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/* Objects support garbage collection (see objimpl.h) */
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#define Py_TPFLAGS_HAVE_GC (1UL << 14)
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/* These two bits are preserved for Stackless Python, next after this is 17 */
@@ -332,8 +329,14 @@ given type object has a specified feature.
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/* NOTE: The following flags reuse lower bits (removed as part of the
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* Python 3.0 transition). */
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332+
/* The following flags are kept for compatibility, but all types are
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* supposed to support the given functionality. Starting with 3.8,
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* binary compatibility of C extensions accross feature releases of
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* Python is not supported anymore, except when using the stable ABI.
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*/
337+
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/* Type structure has tp_finalize member (3.4) */
336-
#define Py_TPFLAGS_HAVE_FINALIZE (1UL << 0)
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#define Py_TPFLAGS_HAVE_FINALIZE Py_TPFLAGS_DEFAULT
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#ifdef Py_LIMITED_API
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# define PyType_HasFeature(t,f) ((PyType_GetFlags(t) & (f)) != 0)

‎Misc/NEWS.d/next/Core and Builtins/2017-12-21-20-37-40.bpo-32388.6w-i5t.rst‎

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@@ -0,0 +1 @@
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Remove cross-version binary compatibility requirement in tp_flags.

‎Modules/_asynciomodule.c‎

Lines changed: 2 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1431,8 +1431,7 @@ static PyTypeObject FutureType = {
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.tp_dealloc = FutureObj_dealloc,
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.tp_as_async = &FutureType_as_async,
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.tp_repr = (reprfunc)FutureObj_repr,
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.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_FINALIZE,
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.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE,
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.tp_doc = _asyncio_Future___init____doc__,
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.tp_traverse = (traverseproc)FutureObj_traverse,
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.tp_clear = (inquiry)FutureObj_clear,
@@ -2462,8 +2461,7 @@ static PyTypeObject TaskType = {
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.tp_dealloc = TaskObj_dealloc,
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.tp_as_async = &FutureType_as_async,
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.tp_repr = (reprfunc)FutureObj_repr,
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.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_FINALIZE,
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.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_BASETYPE,
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.tp_doc = _asyncio_Task___init____doc__,
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.tp_traverse = (traverseproc)TaskObj_traverse,
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.tp_clear = (inquiry)TaskObj_clear,

‎Modules/_io/bufferedio.c‎

Lines changed: 5 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -2342,8 +2342,7 @@ PyTypeObject PyBufferedIOBase_Type = {
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0, /*tp_getattro*/
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0, /*tp_setattro*/
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0, /*tp_as_buffer*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
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bufferediobase_doc, /* tp_doc */
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0, /* tp_traverse */
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0, /* tp_clear */
@@ -2434,7 +2433,7 @@ PyTypeObject PyBufferedReader_Type = {
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0, /*tp_setattro*/
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0, /*tp_as_buffer*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
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| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
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_io_BufferedReader___init____doc__, /* tp_doc */
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(traverseproc)buffered_traverse, /* tp_traverse */
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(inquiry)buffered_clear, /* tp_clear */
@@ -2520,7 +2519,7 @@ PyTypeObject PyBufferedWriter_Type = {
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0, /*tp_setattro*/
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0, /*tp_as_buffer*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
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| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
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_io_BufferedWriter___init____doc__, /* tp_doc */
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(traverseproc)buffered_traverse, /* tp_traverse */
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(inquiry)buffered_clear, /* tp_clear */
@@ -2597,7 +2596,7 @@ PyTypeObject PyBufferedRWPair_Type = {
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0, /*tp_setattro*/
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0, /*tp_as_buffer*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /* tp_flags */
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| Py_TPFLAGS_HAVE_GC, /* tp_flags */
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_io_BufferedRWPair___init____doc__, /* tp_doc */
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(traverseproc)bufferedrwpair_traverse, /* tp_traverse */
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(inquiry)bufferedrwpair_clear, /* tp_clear */
@@ -2691,7 +2690,7 @@ PyTypeObject PyBufferedRandom_Type = {
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0, /*tp_setattro*/
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0, /*tp_as_buffer*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
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| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
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_io_BufferedRandom___init____doc__, /* tp_doc */
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(traverseproc)buffered_traverse, /* tp_traverse */
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(inquiry)buffered_clear, /* tp_clear */

‎Modules/_io/fileio.c‎

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Original file line numberDiff line numberDiff line change
@@ -1196,12 +1196,12 @@ PyTypeObject PyFileIO_Type = {
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0, /* tp_setattro */
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0, /* tp_as_buffer */
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /* tp_flags */
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| Py_TPFLAGS_HAVE_GC, /* tp_flags */
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_io_FileIO___init____doc__, /* tp_doc */
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(traverseproc)fileio_traverse, /* tp_traverse */
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(inquiry)fileio_clear, /* tp_clear */
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0, /* tp_richcompare */
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offsetof(fileio, weakreflist), /* tp_weaklistoffset */
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offsetof(fileio, weakreflist), /* tp_weaklistoffset */
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0, /* tp_iter */
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0, /* tp_iternext */
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fileio_methods, /* tp_methods */
@@ -1211,7 +1211,7 @@ PyTypeObject PyFileIO_Type = {
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0, /* tp_dict */
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0, /* tp_descr_get */
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0, /* tp_descr_set */
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offsetof(fileio, dict), /* tp_dictoffset */
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offsetof(fileio, dict), /* tp_dictoffset */
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_io_FileIO___init__, /* tp_init */
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PyType_GenericAlloc, /* tp_alloc */
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fileio_new, /* tp_new */

‎Modules/_io/iobase.c‎

Lines changed: 2 additions & 2 deletions
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@@ -856,7 +856,7 @@ PyTypeObject PyIOBase_Type = {
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0, /*tp_setattro*/
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0, /*tp_as_buffer*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
859+
| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
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iobase_doc, /* tp_doc */
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(traverseproc)iobase_traverse, /* tp_traverse */
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(inquiry)iobase_clear, /* tp_clear */
@@ -1051,7 +1051,7 @@ PyTypeObject PyRawIOBase_Type = {
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0, /*tp_getattro*/
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0, /*tp_setattro*/
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0, /*tp_as_buffer*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
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rawiobase_doc, /* tp_doc */
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0, /* tp_traverse */
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0, /* tp_clear */

‎Modules/_io/textio.c‎

Lines changed: 2 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -183,8 +183,7 @@ PyTypeObject PyTextIOBase_Type = {
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0, /*tp_getattro*/
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0, /*tp_setattro*/
185185
0, /*tp_as_buffer*/
186-
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
187-
| Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
186+
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
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textiobase_doc, /* tp_doc */
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0, /* tp_traverse */
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0, /* tp_clear */
@@ -3184,7 +3183,7 @@ PyTypeObject PyTextIOWrapper_Type = {
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0, /*tp_setattro*/
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0, /*tp_as_buffer*/
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Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
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| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
3186+
| Py_TPFLAGS_HAVE_GC, /*tp_flags*/
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_io_TextIOWrapper___init____doc__, /* tp_doc */
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(traverseproc)textiowrapper_traverse, /* tp_traverse */
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(inquiry)textiowrapper_clear, /* tp_clear */

‎Modules/_io/winconsoleio.c‎

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@@ -1133,7 +1133,7 @@ PyTypeObject PyWindowsConsoleIO_Type = {
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0, /* tp_setattro */
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0, /* tp_as_buffer */
11351135
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
1136-
| Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /* tp_flags */
1136+
| Py_TPFLAGS_HAVE_GC, /* tp_flags */
11371137
_io__WindowsConsoleIO___init____doc__, /* tp_doc */
11381138
(traverseproc)winconsoleio_traverse, /* tp_traverse */
11391139
(inquiry)winconsoleio_clear, /* tp_clear */

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