add an API to the standard library to learn the system page size

[gpanders]

Zig Version

0.10.0-dev.1434+676652865

Steps to Reproduce

I am running Linux on a MacBook Pro which uses 16 KiB pages; however, Zig's std lib always assumes 4 KiB pages on Linux running on aarch64.

Expected Behavior

Zig should infer/detect the correct page size.

Actual Behavior

Zig assumes 4 KiB pages, which results in errors in calls to msync or mmap (e.g. in std.debug.captureStackTrace).

#4082 is mentioned in the source code, so I'm guessing that is the long term solution. That issue also mentions a "hacky" solution of using madvise to check for a valid page size. A short term solution could be to check madvise at compile time when running Linux on aarch64 to check between all possible page sizes (ARM64 can also support 64 KiB pages). If this is acceptable I can open a PR. EDIT: It looks like syscalls can't run at comptime so I don't think this would work.

[vielmetti]

I've added this to the @AsahiLinux list of code that is known to have problems with a 16K page size, at

https://github.com/AsahiLinux/docs/wiki/Software-known-to-have-issues-with-16k-page-size

As a reference point, this particular issue was addressed in Go (golang) at golang/go#10180 by determining system page size at runtime. The side effect is to improve compatibility on a variety of platforms with non-4K page sizes.

[dkwo]

@Vexu Why does this issue have an os-macos label, while it is specific of linux? also, any chance it could be assigned to an earlier milestone?

[Vexu]

I can put it on 0.11.0 but it doesn't mean much since it could be resolved earlier or later anyways.

[dkwo]

Would it be feasible to adopt for linux whatever solution zig already adopts for macos?