Rustix's current design is to transparently always set LARGEFILE internally, rather than have it be a flag that users have to set. Could you say more about what motivates this PR?

Rustix's current design is to transparently always set LARGEFILE internally

The motivation is to define it, so users can use it when they really want (when you are writing a FUSE server that process users' LARGEFILE flag, or if the user is rustix itself), and they can see its existence from fcntl_getfl rather than a magic hexadecimal number. Passing them transparently does not mean to hide their existence from all users.

Thinking about this more, I think you're right. We should add OFlags::LARGEFILE. It'd be good to document that it's not necessary for most users, as rustix functions set it automatically.

It'd be good to document that it's not necessary for most users, as rustix functions set it automatically.

Added.

Thanks!