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Includes/internal/pycore_code.h uses static_assert() but does not inlcude pymacro.h #123747
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In general, I would suggest to only include
<pycore_xxx.h>headers after including<Python.h>.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#includeorder for the definitions they use?Do you get the error if you include
<Python.h>first?Yes. But the error is unrelated to what I am trying to say.
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.
Thanks. There is nothing wrong then.
Reacted by Victor StinnerIt 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 includesPython.hbut then also needspycore_frame.hlater, which includespycore_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
Since it is really just an assertion that gets in the way here, I propose to comment it out for the final release.
1 remaining item
FTR, here's the comment concerning
static_assert(it may help people that are too lazy to find it in the codebase):// gh-91782: On FreeBSD 12, if the _POSIX_C_SOURCE and _XOPEN_SOURCE macros are // defined, <sys/cdefs.h> disables C11 support and <assert.h> does not define // the static_assert() macro. // https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=255290 // // macOS <= 10.10 doesn't define static_assert in assert.h at all despite // having C11 compiler support. // // static_assert is defined in glibc from version 2.16. Compiler support for // the C11 _Static_assert keyword is in gcc >= 4.6. // // MSVC makes static_assert a keyword in C11-17, contrary to the standards. // // In C++11 and C2x, static_assert is a keyword, redefining is undefined // behaviour. So only define if building as C, not C++ (if __cplusplus is // not defined), and only for C11-17.
I don't understand how to reproduce the issue. Can somone provide a reproducer? Does the issue only affect macOS? With which C compiler and which compiler options?
I can reproduce the issue compiling the most simple Cython extension module:
def foo(): return 42
with Cython 3.0.11 with clang from Xtools:
$ cc --version Apple clang version 14.0.0 (clang-1400.0.29.202)
using an explicit
-std=c99compilation option.A more synthetic reproducer is trying to compile something like:
#include "Python.h" #include "internal/pycore_frame.h" int main() { }
In this way:
$ cc foo.c -o foo.o -DPy_BUILD_CORE=1 $(python3.13-config --cflags) -std=c99Omitting the
-std=c99or setting it to-std=c11or higher the snippet compiles.As pointed out before, the issue is that
static_assert()is a C11 concept. CPython requires C11 thus it is fine. However, Cython requires only C99 and it includes internal CPython headers which assume C11 features.For some reason that I have not investigated,
static_assert()is defined when compiling with GCC on Linux or MSVC on Windows when requesting C99 compliance.Apple clang version 14.0.0 (clang-1400.0.29.202)
I cannot reproduce the issue on Linux (Fedora 40) with clang 18.1.6.
See also discussion capi-workgroup/decisions#30
Could Cython re-
#define static_assert(EXPR, MSG)to nothing if compiling in C99 mode?- added a commit that references this issue
on Sep 6, 2024 - moved this from Todo to Done in Release and Deferred blockers 🚫
on Sep 6, 2024 Thanks for your bug report @dnicolodi!
Bug report
Bug description:
Includes/internal/pycore_code.husesstatic_assert()but does not inlcudepymacro.h, should it?AFAIU
pymacro.hmakes sure thatstatic_assert()is correctly defined for all supported compilers and platforms. Not including it inIncludes/internal/pycore_code.himplicitly relies onpymacro.hbeing 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
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