As part of the PEP-652 implementation, I'll tighten the CI check
for functions/data defined with `Py_LIMITED_API`.
Discussion in https://discuss.python.org/t/pep-652-maintaining-the-stable-abi/6986
suggests that parsing C headers is OK (though personally I'd rather generate it...),
but writing a full C parser is a monumental task and adding an existing one as a
dependency brings too many vendoring/bootstraping issues.
So, for the check I'll use a "simple" regex on preprocessor output, and adapt
the few trivial places where the regex won't work.
- Keep declarations in the limited API to one item per line
- Make it possible to override `_Py_NO_RETURN`, so the annotation can be
removed from preprocessor output.
https://bugs.python.org/issue43795
The Python C API
================
The C API is divided into three sections:
1. ``Include/``
2. ``Include/cpython/``
3. ``Include/internal/``
Include: Limited API
====================
``Include/``, excluding the ``cpython`` and ``internal`` subdirectories,
contains the public Limited API (Application Programming Interface).
The Limited API is a subset of the C API, designed to guarantee ABI
stability across Python 3 versions, and is defined in :pep:`384`.
Guidelines for expanding the Limited API:
- Functions *must not* steal references
- Functions *must not* return borrowed references
- Functions returning references *must* return a strong reference
- Macros should not expose implementation details
- Please start a public discussion before expanding the API
- Functions or macros with a ``_Py`` prefix do not belong in ``Include/``.
It is possible to add a function or macro to the Limited API from a
given Python version. For example, to add a function to the Limited API
from Python 3.10 and onwards, wrap it with
``#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030A0000``.
Include/cpython: CPython implementation details
===============================================
``Include/cpython/`` contains the public API that is excluded from the
Limited API and the Stable ABI.
Guidelines for expanding the public API:
- Functions *must not* steal references
- Functions *must not* return borrowed references
- Functions returning references *must* return a strong reference
Include/internal: The internal API
==================================
With PyAPI_FUNC or PyAPI_DATA
-----------------------------
Functions or structures in ``Include/internal/`` defined with
``PyAPI_FUNC`` or ``PyAPI_DATA`` are internal functions which are
exposed only for specific use cases like debuggers and profilers.
With the extern keyword
-----------------------
Functions in ``Include/internal/`` defined with the ``extern`` keyword
*must not and can not* be used outside the CPython code base. Only
built-in stdlib extensions (built with the ``Py_BUILD_CORE_BUILTIN``
macro defined) can use such functions.
When in doubt, new internal C functions should be defined in
``Include/internal`` using the ``extern`` keyword.
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