`Includes/internal/pycore_code.h` uses `static_assert()` but does not inlcude `pymacro.h`

[dnicolodi]

Bug report

Bug description:

Includes/internal/pycore_code.h uses static_assert() but does not inlcude pymacro.h, should it?

AFAIU pymacro.h makes sure that static_assert() is correctly defined for all supported compilers and platforms. Not including it in Includes/internal/pycore_code.h implicitly relies on pymacro.h being included before or via transitive includes.

I've found this while investigating a Cython extension module build failure. Cython includes the private header and thus requires static_macro() to be defined.

CPython versions tested on:

3.13, CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-123747: Avoid static_assert() in internal header files #123779
• [3.13] gh-123747: Avoid static_assert() in internal header files (#123779) #123785

[vstinner]

In general, I would suggest to only include <pycore_xxx.h> headers after including <Python.h>.

[dnicolodi]

Sure, the compilation error is unrelated (Cython requires only C99 which does not have static_assert()). This report is more about a question of principle: should CPython internal headers be independent or can they rely on #include order for the definitions they use?

[vstinner]

Do you get the error if you include <Python.h> first?

[dnicolodi]

Yes. But the error is unrelated to what I am trying to say.

[vstinner]

This report is more about a question of principle: should CPython internal headers be independent or can they rely on #include order for the definitions they use?

They are not independent. <Python.h> must always be included first.

[dnicolodi]

Thanks. There is nothing wrong then.

[scoder]

It turns out that this is an issue, even after #include "Python.h":
cython/cython#6385 (comment)
This issue was found in Cython generated code, which always includes Python.h but then also needs pycore_frame.h later, which includes pycore_code.h.

Since Cython code is not commonly compiled with C11 (we currently require C99), there are platforms where the resulting code does not compile