libnative/io/net, file_unix: fix offset parameters.

[nodakai]

Fixes#17791

[rust-highfive]

Warning

• These commits modify unsafe code. Please review it carefully!

[alexcrichton]

I think for now this may want to wait until #18557 is merged, and in the meantime is there any way that we can test this functionality? This all seems incredibly subtle and very easy to mess up, and it would be very nice to have regression tests making sure that we're not going too far into the weeds here.

I'm also a little uncomfortable with how these functions are turning out generically, there's a growing number of functions in libnative to deal with errors (check_error, check_error_unit, keep_going, mkerr_libc, ...). Isn't check_error_unit the same as mkerr_libc, and isn't the nonzero case of check_error the same as mkerr_libc?

[nodakai]

@alexcrichton I wasn't aware The Great I/O Reorganization was in progress when I submitted this patch. I'll wait for its completion and will work on regression tests meantime.

I'll also address the issue of prolification of error check utilites.

[alexcrichton]

Aha! It has now landed. Feel free to ping me when this is rebased and I'll take another look. Thanks @nodakai!

[steveklabnik]

@nodakai what's up with this PR?

[nodakai]

@steveklabnik I've never forget this but checking consistency of error code handling for tons of system calls takes me long...

[alexcrichton]

Closing due to inactivity, but feel free to reopen with a rebase!