typeobject.c includes<stddef.h> and<stdalign.h>, which should definemax_align_t andalignof in C11. Yet, the Windows build complains:

D:\a\cpython\cpython\Objects\typeobject.c(3558,34): warning C4013: 'alignof' undefined; assuming extern returning int [D:\a\cpython\cpython\PCbuild\_freeze_module.vcxproj]D:\a\cpython\cpython\Objects\typeobject.c(3558,53): error C2065: 'max_align_t': undeclared identifier [D:\a\cpython\cpython\PCbuild\_freeze_module.vcxproj]

What am I missing?
@zooba, could you help?

(The reference I linked to listsalignof as removed in C23, which is a bit misleading. Themacro will be removed because it willbecome a keyword.)

Looks like you needstdalign.h foralignof (defines thealignof macro to_Alignof), andmax_align_t only seems to exist for C++ viacstddef, where it's mapped todouble.

That means I can't usemax_align_t in CPython? Well, I can work around it.
But I was under the impression that MSVC did support C11. I can start the discussion to addmax_align_t (and possiblyalignof?) as exceptions to PEP 7. Do you know of any other C11 required features MSVC (or our configuration of it) doesn't support?

🤖 New build scheduled with the buildbot fleet by@encukou for commitec9d5a8 🤖

If you want to schedule another build, you need to add the🔨 test-with-buildbots label again.

The TraceRefs buildbot failure:

Modules/gcmodule.c:450: visit_decref: Assertion "!_PyObject_IsFreed(op)" failed
Enable tracemalloc to get the memory block allocation traceback

is likely caused bygh-103621.

🤖 New build scheduled with the buildbot fleet by@encukou for commit402ecc6 🤖

If you want to schedule another build, you need to add the🔨 test-with-buildbots label again.

🤖 New build scheduled with the buildbot fleet by@encukou for commitdb5d49b 🤖

If you want to schedule another build, you need to add the🔨 test-with-buildbots label again.

Thank you for the thorough review!
This should address the remaining comments.

Thanks! I've got some more comments, but we can deal with those in a follow-up PR if you think it's worth it. Let's land this before the feature freeze kicks in.

(I'm on mobile now; I won't be able to check the changes until tomorrow.)

Thanks for the reviews!

I'll merge, and leave the issues open for other PRs.

Thanks for the reviews!

I'll merge, and leave the issues open for other PRs.

Good job! This is a very nice feature.

Thank you!

FWIW, here's a follow-up on thealignof(max_align_t):https://discuss.python.org/t/requiring-compilers-c11-standard-mode-to-build-cpython/26481