I’m glad there is more clarity here. And thanks to Erlend Egeberg Aasland for championing the PR! —Guido On Thu, Mar 25, 2021 at 09:30 Victor Stinner <vstinner@python.org> wrote:
Hi,
A new Include/README.rst file was just added to document the 3 C API provided by CPython:
* Include/: Limited C API * Include/cpython/: CPython implementation details * Include/internal/: The internal API
I would like to note that *new* public C API functions must no longer steal references or return borrowed references.
Don't worry, there is no plan to deprecate or remove existing functions which do that, like PyModule_AddObject() (streal a reference) or PyDict_GetItem() (return a borrowed reference). The policy is only to *add* new functions.
IMO for the *internal* C API, it's fine to continue doing that for best performances.
Moreover, the limited C API must not expose "implementation details". For example, structure members must not be accessed directly, because most structures are excluded from the limited C API. A function call hiding implementation details is usually better.
Here is a copy of the current Include/README.rst file:
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.
Victor -- Night gathers, and now my watch begins. It shall not end until my death. _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/QKFDGIAF... Code of Conduct: http://python.org/psf/codeofconduct/
-- --Guido (mobile)