[Python-Dev] Procedure for adding new public C API (original) (raw)

Paul Moore p.f.moore at gmail.com
Mon May 21 09:27:49 EDT 2018

On 21 May 2018 at 13:41, Serhiy Storchaka <storchaka at gmail.com> wrote:

Please don't forgot to perform the following steps when add a new public C API:

* Document it in Doc/c-api/. * Add an entry in the What's New document. * Add it in Doc/data/refcounts.dat. * Add it in PC/python3.def.

I thought python3.def should only contain symbols in the limited ABI (it defines the API of python3.dll, doesn't it?)

If you want to include it in the limited API, wrap its declaration with:

#if !defined(PyLIMITEDAPI) || PyLIMITEDAPI+0 >= 0x03080000 #endif (use the correct Python version of introducing a feature in the comparison) If you don't want to include it in the limited API, wrap its declaration with: #ifndef PyLIMITEDAPI #endif

Is it even acceptable to add a symbol into the limited ABI? I thought the idea was that if I linked with python3.dll, my code would work with any version of Python 3? By introducing new symbols, code linked with the python3.dll shipped with (say) Python 3.8 would fail to run if executed with the python3.dll from Python 3.5.

I have code that links with python3.dll, which is expected to run with any version of Python 3, so this isn't theoretical. (I'm not 100% sure whether, if I build with a Python 3.5 version of the headers, my code will link with a python3.dll with extra symbols - but even if that's the case, requiring cross-version binaries to be built with the oldest version of Python that they support seems restrictive at best.

You are free of adding private C API, but its name should start with Py or PY and its declaration should be wrapped with:

#ifndef PyLIMITEDAPI #endif

Paul

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