PEP 674: Address Petr's review

pep-0674.rst

@@ -1,5 +1,5 @@
 PEP: 674
-Title: Disallow using Py_TYPE() and Py_SIZE() macros as l-values
+Title: Disallow using macros as l-values
 Author: Victor Stinner <[email protected]>
 Status: Draft
 Type: Standards Track
@@ -10,16 +10,8 @@ Python-Version: 3.11
 Abstract
 ========
 
-Incompatible C API change disallowing using macros, especially
-``Py_TYPE()`` and ``Py_SIZE()``, as l-values to:
-
-* Allow evolving CPython internals (change the ``PyObject`` structure);
-* Ease the C API implementation on other Python implementation;
-* Help migrating existing C extensions to the HPy API.
-
-Only 7 out of the top 5000 PyPI projects (0.1%) are affected by this
-PEP. An additional 23 projects just have to regenerate their Cython
-code.
+Disallow using macros as l-values. For example,
+``Py_TYPE(obj) = new_type`` now fails with a compiler error.
 
 In practice, the majority of affected projects only have to make two
 changes:
@@ -301,6 +293,9 @@ Backwards Compatibility
 
 The proposed C API changes are backward incompatible on purpose.
 
+In practice, only ``Py_TYPE()`` and ``Py_SIZE()`` macros are used as
+l-values.
+
 This change does not follow the :pep:`387` deprecation process. There is
 no known way to emit a deprecation warning only when a macro is used as
 an l-value, but not when it's used differently (ex: as a r-value).
@@ -309,46 +304,44 @@ The following 4 macros are left unchanged to reduce the number of
 affected projects: ``PyDescr_NAME()``, ``PyDescr_TYPE()``,
 ``PyList_GET_ITEM()`` and ``PyTuple_GET_ITEM()``.
 
+Statistics
+----------
+
+In total (projects on PyPI and not on PyPI), 41 projects are affected by
+this PEP:
+
+* 14 projects (34%) are already fixed
+* 27 projects (66%) are not fixed yet
+  (pending fix or generated Cython code)
+
+On January 27, 2022, the PEP affects 27 projects (0.5%) of the top 5000
+PyPI projects:
+
+* 22 projects (0.4%) have to regenerate their Cython code
+* 5 projects (0.1%) have a pending fix
+
 Top 5000 PyPI
 -------------
 
-On January 27, 2022, a code search on the top 5000 PyPI projects found
-that only 7 projects are affected (0.1%):
+Projects with a pending fix (5):
 
 * datatable (1.0.0):
   `pending PR <https://github.com/h2oai/datatable/pull/3231>`__
-* guppy3 (3.1.2): `fixed <https://github.com/zhuyifei1999/guppy3/commit/4cb9fcb5d75327544a6875b6caabfdffb70a7e29>`__
-* pickle5 (0.0.12): backport for Python <= 3.7
-* pysha3 (1.0.2): backport for Python <= 3.5
+* guppy3 (3.1.2):
+  `fixed <https://github.com/zhuyifei1999/guppy3/commit/4cb9fcb5d75327544a6875b6caabfdffb70a7e29>`__
 * python-snappy (0.6.0):
   `fixed <https://github.com/andrix/python-snappy/commit/1a539d71d5b1ceaf9a2291f21f686cf53a46d707>`__
 * recordclass (0.17.1):
   `fixed <https://bitbucket.org/intellimath/recordclass/commits/d20d72fa3cdbdcf96c72941560041460adeecff1>`__
 * scipy (1.7.3): fixed (need to update boost)
 
-All of those projects are fixed (but not released), have a pending fix,
-or should not be fixed (backports).
-
-An additional 23 projects only have to regenerate their Cython code to
-use ``Py_SET_TYPE()`` and ``Py_SET_SIZE()``.
-
-Only 2 macros are used as an l-value: ``Py_TYPE()`` and ``Py_SIZE()``.
+Moreover, 22 projects have to regenerate their Cython code.
 
-Projects released with a fix
-----------------------------
-
-Projects released with a fix (14):
+Projects released with a fix (10):
 
 * bitarray (1.6.2):
   `commit <https://github.com/ilanschnell/bitarray/commit/a0cca9f2986ec796df74ca8f42aff56c4c7103ba>`__
-* boost (1.78.0): `commit
-  <https://github.com/boostorg/python/commit/500194edb7833d0627ce7a2595fec49d0aae2484>`__
-* breezy (3.2.1): `bug report <https://bugs.launchpad.net/brz/+bug/1904868>`__
 * Cython (0.29.20): `commit <https://github.com/cython/cython/commit/d8e93b332fe7d15459433ea74cd29178c03186bd>`__
-* duplicity (0.8.18):
-  `commit <https://git.launchpad.net/duplicity/commit/duplicity/_librsyncmodule.c?id=bbaae91b5ac6ef7e295968e508522884609fbf84>`__
-* gobject-introspection (1.70.0):
-  `MR <https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/243>`__
 * immutables (0.15):
   `commit <https://github.com/MagicStack/immutables/commit/45105ecd8b56a4d88dbcb380fcb8ff4b9cc7b19c>`__
 * mercurial (5.7):
@@ -364,9 +357,30 @@ Projects released with a fix (14):
 * PyGObject (3.42.0)
 * pyside2 (5.15.1):
   `bug report <https://bugreports.qt.io/browse/PYSIDE-1436>`__
-* python-zstd (1.5.0.3):
+* zstd (1.5.0.3):
   `commit <https://github.com/sergey-dryabzhinsky/python-zstd/commit/8aa6d7a4b250e1f0a4e27b4107c39dc516c87f96>`__
 
+There are also two backport projects which are affected by this PEP:
+
+* pickle5 (0.0.12): backport for Python <= 3.7
+* pysha3 (1.0.2): backport for Python <= 3.5
+
+They must not be used and cannot be used on Python 3.11.
+
+Other affected projects
+-----------------------
+
+Other projects released with a fix (4):
+
+* boost (1.78.0):
+  `commit <https://github.com/boostorg/python/commit/500194edb7833d0627ce7a2595fec49d0aae2484>`__
+* breezy (3.2.1):
+  `bug report <https://bugs.launchpad.net/brz/+bug/1904868>`__
+* duplicity (0.8.18):
+  `commit <https://git.launchpad.net/duplicity/commit/duplicity/_librsyncmodule.c?id=bbaae91b5ac6ef7e295968e508522884609fbf84>`__
+* gobject-introspection (1.70.0):
+  `MR <https://gitlab.gnome.org/GNOME/gobject-introspection/-/merge_requests/243>`__
+
 
 Relationship with the HPy project
 =================================