cpython/Doc/c-api/apiabiversion.rst
Petr Viktorin b05955d6f5
bpo-43795: PEP 652 user documentation (GH-25668)
- Reformat the C API and ABI Versioning page (and extend/clarify a bit)
- Rewrite the stable ABI docs into a general text on C API Compatibility
- Add a list of Limited API contents, and notes for the individual items. 
- Replace `Include/README.rst` with a link to a devguide page with the same info
2021-05-11 07:04:33 -07:00

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.. highlight:: c
.. _apiabiversion:
***********************
API and ABI Versioning
***********************
CPython exposes its version number in the following macros.
Note that these correspond to the version code is **built** with,
not necessarily the version used at **run time**.
See :ref:`stable` for a discussion of API and ABI stability across versions.
.. c:macro:: PY_MAJOR_VERSION
The ``3`` in ``3.4.1a2``.
.. c:macro:: PY_MINOR_VERSION
The ``4`` in ``3.4.1a2``.
.. c:macro:: PY_MICRO_VERSION
The ``1`` in ``3.4.1a2``.
.. c:macro:: PY_RELEASE_LEVEL
The ``a`` in ``3.4.1a2``.
This can be ``0xA`` for alpha, ``0xB`` for beta, ``0xC`` for release
candidate or ``0xF`` for final.
.. c:macro:: PY_RELEASE_SERIAL
The ``2`` in ``3.4.1a2``. Zero for final releases.
.. c:macro:: PY_VERSION_HEX
The Python version number encoded in a single integer.
The underlying version information can be found by treating it as a 32 bit
number in the following manner:
+-------+-------------------------+-------------------------+--------------------------+
| Bytes | Bits (big endian order) | Meaning | Value for ``3.4.1a2`` |
+=======+=========================+=========================+==========================+
| 1 | 1-8 | ``PY_MAJOR_VERSION`` | ``0x03`` |
+-------+-------------------------+-------------------------+--------------------------+
| 2 | 9-16 | ``PY_MINOR_VERSION`` | ``0x04`` |
+-------+-------------------------+-------------------------+--------------------------+
| 3 | 17-24 | ``PY_MICRO_VERSION`` | ``0x01`` |
+-------+-------------------------+-------------------------+--------------------------+
| 4 | 25-28 | ``PY_RELEASE_LEVEL`` | ``0xA`` |
+ +-------------------------+-------------------------+--------------------------+
| | 29-32 | ``PY_RELEASE_SERIAL`` | ``0x2`` |
+-------+-------------------------+-------------------------+--------------------------+
Thus ``3.4.1a2`` is hexversion ``0x030401a2`` and ``3.10.0`` is
hexversion ``0x030a00f0``.
All the given macros are defined in :source:`Include/patchlevel.h`.