See also: https://internals.rust-lang.org/t/can-the-standard-library-shrink-option-file/12768 https://internals.rust-lang.org/t/can-the-standard-library-s... A

See also: https://internals.rust-lang.org/t/can-the-standard-library-shrink-option-file/12768 https://internals.rust-lang.org/t/can-the-standard-library-s... A file descriptor can't be -1 but it's not 100% clear whether POSIX bans other negative numbers. So Rust's stdlib only bans -1 (for a space optimization) while still allowing for e.g. -2.