Build failure due to missing _Py_SINGLETON in static-extension-modules build (3.13 only)

[kpfleming]

Bug report

Bug description:

While attempting to upgrade python-build-standalone to support Python 3.13 beta releases, we've run into a build failure which may be caused by Argument Clinic failing to ensure that all necessary #include directives are emitted into the source files it generates.

The failure can be seen here. Granted this is a very unusual way to build CPython, but given some of the discussions at the recent Packaging Summit it may become more valuable soon :-)

It was suggested that @vstinner might have the knowledge needed to understand what is happening here, so apologies in advance for the direct ping :-)

I'm happy to include patches into that build tree to see if we can overcome the problem before the next beta release, and I'm also happy to make that branch writable by others who want to try to help troubleshoot.

CPython versions tested on:

3.13

Operating systems tested on:

Linux, macOS, Windows

Linked PRs

• gh-119661: Add _Py_SINGLETON() include in Argumenet Clinic #119712
• [3.13] gh-119661: Add _Py_SINGLETON() include in Argumenet Clinic (#119712) #119716

[vstinner]

The failure can be seen here.

cpython-3.13> ./Modules/clinic/_curses_panel.c.h: In function '_curses_panel_panel_move':
cpython-3.13> ./Modules/clinic/_curses_panel.c.h:169:36: error: implicit declaration of function '_Py_SINGLETON' [-Werror=implicit-function-declaration]
cpython-3.13>      #  define KWTUPLE (PyObject *)&_Py_SINGLETON(tuple_empty)
cpython-3.13>                                     ^
cpython-3.13> ./Modules/clinic/_curses_panel.c.h:178:20: note: in expansion of macro 'KWTUPLE'
cpython-3.13>          .kwtuple = KWTUPLE,
cpython-3.13>                     ^~~~~~~

_Py_SINGLETON() cannot and must not be used outside CPython internals.

If you use Argument Clinic, you can try to generate code using the limited C API instead.

[vstinner]

See also Removed private _PyArg_Parser API has no replacement in Python 3.13.

[kpfleming]

We are building CPython 3.13.0b1, the failure happens in the curses_panel module which is part of the standard extensions. It appears that somehow this code in the tree isn't aware that it is being built as 'internals', so we may be missing some sort of macro definition. This is no doubt an artifact of the somewhat ugly build system used in the python-build-standalone project.

[vstinner]

Can you attach generated Modules/clinic/_curses_panel.c.h file?

[vstinner]

Build command: cpython-3.13> /usr/bin/aarch64-linux-gnu-gcc -I/tools/deps/include/ncursesw -fno-strict-overflow -Wsign-compare -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -g -Og -Wall -fPIC -I/tools/deps/include -I/tools/deps/include/ncursesw -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden -I./Include/internal -I./Include/internal/mimalloc -I. -I./Include -fPIC -I/tools/deps/include -I/tools/deps/include/ncursesw -fPIC -DHAVE_NCURSESW=1 -DPy_BUILD_CORE_BUILTIN -c ./Modules/_curses_panel.c -o Modules/_curses_panel.o

[kpfleming]

We're building from the 3.13.0b1 tarball downloaded from python.org, which has that file (and presumably all of the other 'clinic' files) already generated and present in Modules/clinic.

[vstinner]

I wrote PR gh-119712 to add an explicit include to get the _Py_SINGLETON() macro. You can see that the PR changes Modules/clinic/_curses_panel.c.h to add:

#if defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_MODULE)
#  include "pycore_runtime.h"     // _Py_SINGLETON()
#endif

[kpfleming]

Thank you! We'll apply a local patch with the contents of that PR.