https://bz.mercurial-scm.org/show_bug.cgi?id=6451
Bug ID: 6451
Summary: Py_SET_TYPE() should be used to support Python 3.10
Product: Mercurial
Version: default branch
Hardware: PC
OS: Linux
Status: UNCONFIRMED
Severity: feature
Priority: wish
Component: Mercurial
Assignee: bugzi...@mercurial-scm.org
Reporter: victor.stin...@gmail.com
CC: mercurial-devel@mercurial-scm.org
Python Version: ---
Created attachment 2090
--> https://bz.mercurial-scm.org/attachment.cgi?id=2090&action=edit
Patch adding pythoncapi_compat.h and replace Py_TYPE() assignments with
Py_SET_TYPE() calls.
In Python 3.10, "Py_SET_TYPE(obj, type)" should now be used instead of using
absuing the Py_TYPE() macro: "Py_TYPE(obj) = type;".
See https://www.python.org/dev/peps/pep-0620/ and
https://bugs.python.org/issue39573 for the rationale.
Py_TYPE() was converted to a static inline macro in Python 3.10 to raise a
compiler error on "Py_TYPE(obj) = type;". But since this change broke too many
C extensions, I reverted it.
So I'm now proposing patches to every broken C extensions before considering to
re-apply the change in the Python C API.
Attached patch replaces "Py_TYPE(obj) = type;" with "Py_SET_TYPE(obj, type);".
It adds a copy of the pythoncapi_compat.h header file coming from my project:
https://github.com/pythoncapi/pythoncapi_compat
The initial version of the patch was created by upgrade_pythoncapi.py tool
which is also part of pythoncapi_compat project.
Sadly, I had to copy pythoncapi_compat.h in two directories: mercurial/ and
contrib/python-zstandard/zstd/common/. I didn't know if a contrib/ extension
can add mercurial/ to its include directory list (-I compiler flag).
Feel free to rewrite my patch and steal the patch, I'm not sure to the
Mercurial code base.
There is no need to update pythoncapi_compat.h unless tomorrow you will need a
new function if a newer version of this header file. IMO it's a good practice
to vendor a copy of the header file (which is less than 300 lines of C code).
The pythoncapi_compat project is new and I'm not sure that it's going to be
packaged widely on Windows, macOS and very single Linux distribution (for
example).
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