nix: No conversion between Errno and std::io::Error/i32

There are situation where you want to have the raw error value of an error, e.g. for passing back into C code. Also, there is already a perfectly good type for holding errno in Rust, std::io::Error. It does support getting the raw error value. I suggest deprecating Errno in favor of std::io::Error or at least adding the necessary conversions.

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Original URL
State: open
Created 7 years ago
Reactions: 1
Comments: 19 (9 by maintainers)

Commits related to this issue

Change nix dependency to ioctl_sys Due to nix ways to handle errors, errno is a big enum instead of an i32, and due to https://github.com/nix-rust/nix/issues/613 we must do our own error handling any... — committed to diwic/kernel-asound-sys by diwic 3 years ago

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Here’s a related issue that doesn’t work right now

fn io_func() -> io::Result<()> {
    std::fs::some_function()?;
    nix::some_other_function()?;
}

kahing on Jul 26, 2017

Also, I’d like to make a case for why that impl should be added again: nix::Error is basically a subset of io::Error. While io::Error can hold an arbitrary user error of any ErrorKind or an errno, nix::Error can hold a user error of kind UnsupportedOperation, InvalidPath, InvalidUtf8 or an errno. IMO there’s a very clear mapping between the latter and the former, and I don’t think it makes sense to have to make a custom error type just because you have code that does both stdlib io and unix-specific io. Obviously it’s a good idea to have nix::Error as its own separate type, since it vastly reduces the set of errors that can exist and it makes it much easier to handle, but if you do need to “widen” the error type, I think converting to io::Error makes more sense than having an enum Error { Nix(nix::Error), Io(io::Error) }

coolreader18 on Feb 23, 2021