This macro creates a zero-overhead &CStr by adding a NUL terminator to the string literal passed into it at compile-time. Use it like:
let some_const_cstr = const_cstr!("abc");
The above is roughly equivalent to:
let some_const_cstr = CStr::from_bytes_with_nul(b"abc\0").unwrap()
Note that macro only checks the string literal for internal NULs if debug-assertions are enabled in order to avoid runtime overhead in release builds.