bpo-42171: Add PEP573-related items to the limited API

[encukou]

https://bugs.python.org/issue42171

Automerge-Triggered-By: GH:encukou

[vstinner]

Since PEP 590 has been approved, is there still a reason to exclude METH_FASTCALL from the limited C API? The limited C API is supposed to hide implementation details. Do we still consider that "fastcall" and "vectorcall" are implementation details?

Why not adding METH_FASTCALL to the limited C API, rather than adding a new METH_METHOD_ARGS_KWD macro?

[encukou]

OK! If you're fine adding METH_FASTCALL, I have nothing against it :)

[vstinner]

LGTM, thanks.

@markshannon wrote that "FASTCALL" is a bad name, since there will be faster calling conventions tomorow, but the ship has sailed. Cython uses METH_FASTCALL. It's too late to change it.

When I added METH_FASTCALL, I tried to keep it secret, but Cython started to use the private C API, and here we are :-)

[encukou]

I wouldn't worry that we can't come up with faster-sounding names. Like VictorCall, but that's already taken :)

[vstinner]

METH_VICTORCALL sounds like a good name :-D

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot x86 Gentoo Non-Debug with X 3.x has failed when building commit 0b9c4c6.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/58/builds/340) and take a look at the build logs.
4. Check if the failure is related to this commit (0b9c4c6) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/58/builds/340

Failed tests:

• test_peg_generator

Summary of the results of the build (if available):

==

Click to see traceback logs

remote: Enumerating objects: 1        
remote: Enumerating objects: 14, done.        
remote: Counting objects:   7% (1/14)        
remote: Counting objects:  14% (2/14)        
remote: Counting objects:  21% (3/14)        
remote: Counting objects:  28% (4/14)        
remote: Counting objects:  35% (5/14)        
remote: Counting objects:  42% (6/14)        
remote: Counting objects:  50% (7/14)        
remote: Counting objects:  57% (8/14)        
remote: Counting objects:  64% (9/14)        
remote: Counting objects:  71% (10/14)        
remote: Counting objects:  78% (11/14)        
remote: Counting objects:  85% (12/14)        
remote: Counting objects:  92% (13/14)        
remote: Counting objects: 100% (14/14)        
remote: Counting objects: 100% (14/14), done.        
remote: Compressing objects:   9% (1/11)        
remote: Compressing objects:  18% (2/11)        
remote: Compressing objects:  27% (3/11)        
remote: Compressing objects:  36% (4/11)        
remote: Compressing objects:  45% (5/11)        
remote: Compressing objects:  54% (6/11)        
remote: Compressing objects:  63% (7/11)        
remote: Compressing objects:  72% (8/11)        
remote: Compressing objects:  81% (9/11)        
remote: Compressing objects:  90% (10/11)        
remote: Compressing objects: 100% (11/11)        
remote: Compressing objects: 100% (11/11), done.        
remote: Total 14 (delta 3), reused 3 (delta 3), pack-reused 0        
From /~https://github.com/python/cpython
 * branch                  master     -> FETCH_HEAD
Reset branch 'master'

	not a dynamic executable
/buildbot/buildarea/cpython/3.x.ware-gentoo-x86.nondebug/build/Modules/_ctypes/callbacks.c: In function ‘_ctypes_alloc_callback’:
/buildbot/buildarea/cpython/3.x.ware-gentoo-x86.nondebug/build/Modules/_ctypes/callbacks.c:434:9: warning: ‘ffi_prep_closure’ is deprecated: use ffi_prep_closure_loc instead [-Wdeprecated-declarations]
  434 |         result = ffi_prep_closure(p->pcl_write, &p->cif, closure_fcn, p);
      |         ^~~~~~
In file included from /buildbot/buildarea/cpython/3.x.ware-gentoo-x86.nondebug/build/Modules/_ctypes/callbacks.c:6:
/usr/lib/libffi/include/ffi.h:334:1: note: declared here
  334 | ffi_prep_closure (ffi_closure*,
      | ^~~~~~~~~~~~~~~~

	not a dynamic executable

Cannot open file '/buildbot/buildarea/cpython/3.x.ware-gentoo-x86.nondebug/build/test-results.xml' for upload

[encukou]

The Timeout in test_peg_generator doesn't look related. Will check the next build, https://buildbot.python.org/all/#/builders/58/builds/341

[encukou]

That build first failed (Timeout after 35 minutes), then passed.