kern/58640: alignof is not available in kernel code

[campbell+netbsd%mumble.net@localhost]

>Number:         58640
>Category:       kern
>Synopsis:       alignof is not available in kernel code
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun Aug 25 14:35:00 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current, 10, 9, ...
>Organization:
The AlignedBSD Kernelation
>Environment:
>Description:
The alignof macro, which was introduced in C11, is defined in the <stdalign.h> header file, which is not available in the kernel build environment.

Instead, kernel code has to use the ugly _Alignof builtin.
>How-To-Repeat:
reach for alignof, stub toe on the sharp edge of _Alignof
>Fix:
Yes, please!

Maybe add sys/stdalign.h?