+1

I merged 2 PRs:

• #91733
• #91730

I close the issue.

What about Windows? @zooba are we already building with C11 there?

What about Windows? @zooba are we already building with C11 there?

Apparently, or CI would have broken. I guess we'll find out when people start using new language features.

What about Windows? @zooba are we already building with C11 there?

When the PEP 7 change was discussed on python-dev, it was said that MSVC supports C11 without optional features.

• https://mail.python.org/archives/list/python-dev@python.org/thread/J5FSP6J4EITPY5C2UJI7HSL2GQCTCUWN/
• https://devblogs.microsoft.com/cppblog/c11-and-c17-standard-support-arriving-in-msvc/ <= mentions _Static_assert and has an example using static_assert() of <assert.h>

My PR got merged and the CI is fine. Do you have remaining concerns about MSVC?

The blog post mentions the /std:c11 option: https://docs.microsoft.com/en-us/cpp/build/reference/std-specify-language-standard-version?view=msvc-170 It doesn't seem to be used by Python currently.

I only these /std options:

PCbuild/python_uwp.vcxproj:93:      <AdditionalOptions>/EHsc /std:c++17 %(AdditionalOptions)</AdditionalOptions>
PCbuild/pythonw_uwp.vcxproj:93:      <AdditionalOptions>/EHsc /std:c++17 %(AdditionalOptions)</AdditionalOptions>

The blog post also mentions the /Zc:preprocessor option to switch the preprocessor to C11 mode ("conformant preprocessor"): https://docs.microsoft.com/en-us/cpp/build/reference/zc-preprocessor?view=msvc-170 This option doesn't seem to be currently used by Python.

My remaining concern is that I tried to use static_assert() in #32387 and it broke on Windows. I've merged the latest main and it still breaks. I'll just assume that that is a different problem so I'll move on. (If you want to look into it, details are in that issue.)

The blog post mentions the /std:c11 option: https://docs.microsoft.com/en-us/cpp/build/reference/std-specify-language-standard-version?view=msvc-170 It doesn't seem to be used by Python currently.

Yeah, this probably needs to be added (in pyproject.props). I don't think it will matter if it's included twice in the C++ projects, but that would be the biggest issue.

I reopen the issue.

It looks like AMD64 FreeBSD Non-Debug 3.x is now failing like this:

-- Objects/longobject.o ---
cc -pthread -c  -DNDEBUG -g -fwrapv -O3 -Wall -UNDEBUG -O2 -pipe  -std=c11 -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal  -I. -I./Include    -DPy_BUILD_CORE -o Objects/longobject.o Objects/longobject.c
Objects/longobject.c:776:5: error: implicit declaration of function 'static_assert' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    static_assert(PyLong_SHIFT <= sizeof(unsigned long) * 8,
    ^

@sweeneyde

'static_assert' is invalid in C99

Is config regenerated in a commit pulled by the buildbot?

It looks like AMD64 FreeBSD Non-Debug 3.x is now failing like this:

Right, I just noticed that: I created #91782 to track this issue.

Sadly, this specific FreeBSD buildbot worker failed on the Git step but the CI job was marked as successful on my PR :-(

_Py_NO_RETURN macro can also be changed to use noreturn from stdnoreturn.h.
See https://www.gnu.org/software/gnulib/manual/html_node/stdnoreturn_002eh.html

_Py_NO_RETURN macro can also be changed to use noreturn from stdnoreturn.h.

If you consider that it's worth it, please open a separated issue.

I already got enough issues with static_assert(), so I prefer to restrict this issue to that :-)

Seems that Python 3.11.0 beta 1 doesn't build with gcc 8 in RHEL 6:

/tmp/python3.11-3.11.0~beta1-0/Objects/longobject.c: In function 'bit_length_digit':
 /tmp/python3.11-3.11.0~beta1-0/Objects/longobject.c:776:5: error: implicit declaration of function 'static_assert' [-Werror=implicit-function-declaration]
  776 |     static_assert(PyLong_SHIFT <= sizeof(unsigned long) * 8,
          |     ^~~~~~~~~~~~~

I'm marking this as release blocker as there may be multiple systems affected

Seems that the C11 symbol is _Static_assert not static_assert. The later is a C++ symbol:

https://gcc.gnu.org/wiki/C11Status

static_assert requires glibc 2.16 or newer.

For instance, in RHEL 6 /usr/include/assert.h doesn't provide static_assert. This means that manylinux2010 won't be able to compile Python 3.11.

Opened #92559

Seems that muslc has the macro as well https://github.com/seL4/musllibc/blob/c7aa943a2ad4fccaccf52a1f957bf8860f57f5b0/include/assert.h

Seems that the C11 symbol is _Static_assert not static_assert.

static_assert should be valid in standard C11, too. It's a macro in assert.h. See C11 §7.2p3, which says:

The macro static_assert expands to _Static_assert.

static_assert should be valid in standard C11, too. It's a macro in assert.h. See C11 §7.2p3, which says:

That's only on glibc 2.16 or newer. GCC itself only provides _Static_assert

Agreed that the C11 requirement apparently mandates glibc >= 2.16. But static_assert is a C11 feature, not just a C++ feature.

static_assert should be valid in standard C11, too. It's a macro in assert.h. See C11 §7.2p3, which says:

There is the theory, and the practice. Did you see the FreeBSD issue about the practice? :-) #91782

macOS 10.10 and older also don't have static_assert defined even when using a C11 compiler.

macOS 10.10 and older also don't have static_assert defined even when using a C11 compiler.

What is your C compiler? What is your error message?

Can you try to add this code at the top of pymacro.h? Does it fix your build issue?

#ifndef static_assert
#  define static_assert _Static_assert
#endif

What is your C compiler? What is your error message?

Apple clang-700.1.81 and clang 11 from llvm.org both produce the same error:

Objects/longobject.c:776:5: error: implicit declaration of function 'static_assert' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    static_assert(PyLong_SHIFT <= sizeof(unsigned long) * 8,
    ^

Can you try to add this code at the top of pymacro.h? Does it fix your build issue?

Yes, that does fix the build. (Technically I just deleted defined(__FreeBSD__) && from the existing check.)

We probably need to add another case. I will prepare a PR. Alternatively, given that this is a macro, we can check if is defined and redefine it ourselves.

Oh, clang 11 didn't support calling static_assert() in the function scope. It was fixed at 2021-01-29 (only in clang 12): https://bugs.llvm.org/show_bug.cgi?id=48904