gh-92898: Make _Py_Cast C++ version compatible with cast operator

[serge-sans-paille]

Use the adequate kind of cast based on the macro argument: const ref, cont
pointer, ref or pointer.

This should be compatible with C++ overloads.

Fix#92898

[serge-sans-paille]

cc @vstinner

[corona10]

Would you like to add NEWS.d about compatible?

[bedevere-bot]

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[serge-sans-paille]

@corona10 I'm not sure, there's already an entry

.. date: 2022-04-26-16-51-31
.. gh-issue: 91320
.. nonce: QDHmTv
.. section: C API
Fix C++ compiler warnings about "old-style cast" (``g++ -Wold-style-cast``)
in the Python C API. Use C++ ``reinterpret_cast<>`` and ``static_cast<>``
casts when the Python C API is used in C++. Patch by Victor Stinner.

And this is just patching that entry

[tacaswell]

I am now seeing errors compiling numpy with this branch:

 In file included from /home/tcaswell/.pybuild/bleeding/include/python3.12/Python.h:38,
from numpy/core/include/numpy/npy_common.h:5,
from numpy/core/include/numpy/npy_math.h:8,
from numpy/core/src/npysort/selection.cpp:18:
/home/tcaswell/.pybuild/bleeding/include/python3.12/pyport.h:31:1: error: template with C linkage
31 | template <typename type, typename expr_type>
| ^~~~~~~~
numpy/core/include/numpy/npy_math.h:5:1: note: ‘extern "C"’ linkage started here
5 | extern "C" {
| ^~~~~~~~~~
/home/tcaswell/.pybuild/bleeding/include/python3.12/pyport.h:36:1: error: template with C linkage
36 | template <typename type, typename expr_type>
| ^~~~~~~~
numpy/core/include/numpy/npy_math.h:5:1: note: ‘extern "C"’ linkage started here
5 | extern "C" {
| ^~~~~~~~~~
/home/tcaswell/.pybuild/bleeding/include/python3.12/pyport.h:41:1: error: template with C linkage
41 | template <typename type, typename expr_type>
| ^~~~~~~~
numpy/core/include/numpy/npy_math.h:5:1: note: ‘extern "C"’ linkage started here
5 | extern "C" {
| ^~~~~~~~~~
/home/tcaswell/.pybuild/bleeding/include/python3.12/pyport.h:46:1: error: template with C linkage
46 | template <typename type, typename expr_type>
| ^~~~~~~~
numpy/core/include/numpy/npy_math.h:5:1: note: ‘extern "C"’ linkage started here
5 | extern "C" {
| ^~~~~~~~~~

g++ -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -fPIC -DNPY_INTERNAL_BUILD=1 -DHAVE_NPY_CONFIG_H=1 -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE=1 -D_LARGEFILE64_SOURCE=1 -DNO_ATLAS_INFO=1 -DHAVE_CBLAS -I/usr/local/include -I/home/tcaswell/.virtualenvs/bleeding/include -Ibuild/src.linux-x86_64-3.12/numpy/core/src/multiarray -Ibuild/src.linux-x86_64-3.12/numpy/core/src/common -Ibuild/src.linux-x86_64-3.12/numpy/core/src/umath -Inumpy/core/include -Ibuild/src.linux-x86_64-3.12/numpy/core/include/numpy -Ibuild/src.linux-x86_64-3.12/numpy/distutils/include -Ibuild/src.linux-x86_64-3.12/numpy/core/src/npysort -Inumpy/core/src/common -Inumpy/core/src -Inumpy/core -Inumpy/core/src/npymath -Inumpy/core/src/multiarray -Inumpy/core/src/umath -Inumpy/core/src/npysort -Inumpy/core/src/_simd -I/home/tcaswell/.virtualenvs/bleeding/include -I/home/tcaswell/.pybuild/bleeding/include/python3.12 -Ibuild/src.linux-x86_64-3.12/numpy/core/src/common -Ibuild/src.linux-x86_64-3.12/numpy/core/src/npymath -c numpy/core/src/npysort/selection.cpp -o build/temp.linux-x86_64-3.12/numpy/core/src/npysort/selection.o -MMD -MF build/temp.linux-x86_64-3.12/numpy/core/src/npysort/selection.o.d -msse -msse2 -msse3 -std=c++11 -D__STDC_VERSION__=0 -fno-exceptions -fno-rtti

[serge-sans-paille]

@tacaswell indeed. I can work around this :-)

[tacaswell]

@serge-sans-paille I should note this is with numpy main, I have not gone back to see if released versions work or not.

[serge-sans-paille]

@tacaswell should be good now?

[tacaswell]

Through numpy, starting scipy. Will update if the whole environment builds cleanly (including greenlet main).

[tacaswell]

It built clean including master-branch greenlet 👍🏻

[miss-islington]

Thanks @serge-sans-paille for the PR, and @corona10 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

[miss-islington]

Sorry @serge-sans-paille and @corona10, I had trouble checking out the 3.11 backport branch.
Please backport using cherry_picker on command line.
cherry_picker 5b71b519f966e1017c868ea2b27c61a5eac38c1f 3.11

[vstinner]

I created a follow-up PR: #93111

[miss-islington]

Thanks @serge-sans-paille for the PR, and @corona10 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.11.
🐍🍒⛏🤖

[miss-islington]

Sorry, @serge-sans-paille and @corona10, I could not cleanly backport this to 3.11 due to a conflict.
Please backport using cherry_picker on command line.
cherry_picker 5b71b519f966e1017c868ea2b27c61a5eac38c1f 3.11