When is creation of the ```std::io::Error``` instance async-signal-safe?

Hello everyone! In the Rust standard library, a lot of fallible functions interacting with the operating system use std::io::Error as their error type -- it's flexible and allows both reporting errors from an operating system and wrapping a custom error type if it implements std::error::Error trait. One of such facilities is the std::process::Command type, which is a builder type used to configure spawning of the child process. In some operating systems, such as GNU/Linux, the child process is ...