Mapping beyond 4GB offset if broken on 32 bit glibc (Linux)

[lvella]

This is a direct consequence of this rust's libc issue. In rust targeting 32 bits glibc, libc::off_t is 32 bits, which breaks this code if you are trying to map beyond 4 GB in a file:

            let ptr = libc::mmap(
                ptr::null_mut(),
                map_len as libc::size_t,
                prot,
                flags,
                file,
                aligned_offset as libc::off_t,
            );

I had a similar issue with nix crate, where posix_fallocate() also relied on libc::off_t for file sizes. The fix was to use rustix crate, that calls the system-call directly. Maybe a similar workaround could be applied here?

[RazrFalcon]

Switching to rustix seems like a pretty extreme solution. Will wait for libc fix.

[lvella]

Then I suggest at least doing aligned_offset.try_into().unwrap() instead of aligned_offset as libc::off_t, or an assert like assert!(aligned_offset <= libc::off_t::MAX);. That would have saved me a lot of debugging time.

[RazrFalcon]

Feel free to send a pull request.