std.os.access doesn't handle EPERM errno about zig HOT 4 OPEN

I took a cursory look through some man pages for access(2) and found that OpenBSD and man7 lists EPERM as possible errors. Debian and Arch Linux don't list EPERM.

In both OpenBSD and man7, EPERM is related to the immutable flag of a file (set by chflags or ioctl_iflags).

Maybe error.FileImmutable should be added to os.AccessError. Although, since EPERM is a permission error, error.PermissionDenied could be sufficient.

from zig.

Adding error.FileImmutable seems like a sensible approach if nothing else can trigger the EPERM errno. Looking at the linux kernel sources, this seems to be the case.

The do_faccessat function invokes inode_permission which returns the permission error
https://github.com/torvalds/linux/blob/90d35da658da8cff0d4ecbb5113f5fac9d00eb72/fs/open.c#L504C8-L504C24

https://github.com/torvalds/linux/blob/90d35da658da8cff0d4ecbb5113f5fac9d00eb72/fs/namei.c#L517

Maybe we could check where else inode_permission is called from to discover other places where a FileImmutable error should be returned.

from zig.

AccessError.PermissionDenied corresponds to EACCESS:

EACCES The requested access would be denied to the file, or
search permission is denied for one of the directories in
the path prefix of pathname. (See also
path_resolution(7).

I think this is distinct enough from the semantics of EPERM to demand a separate error

from zig.

Actually, looking at functions like mmap, EACCES corresponds to MMapError.AccessDenied while EPERM corresponds to MMAPError.PermissionDenied. It would be more consistent to make AccessError match the set precedent

from zig.