GeezerVison

typeobject.c includes <stddef.h> and <stdalign.h>, which should define max_align_t and alignof 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 lists alignof as removed in C23, which is a bit misleading. The macro will be removed because it will become a keyword.)

Looks like you need stdalign.h for alignof (defines the alignof macro to _Alignof), and max_align_t only seems to exist for C++ via cstddef, where it's mapped to double.

That means I can't use max_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 add max_align_t (and possibly alignof?) 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 commit ec9d5a8 🤖

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 by gh-103621.

🤖 New build scheduled with the buildbot fleet by @encukou for commit 402ecc6 🤖

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 commit db5d49b 🤖

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 the alignof(max_align_t): https://discuss.python.org/t/requiring-compilers-c11-standard-mode-to-build-cpython/26481