It might be good to mention how to free the memory. By passing the pointer back to a rust function like #[no_mangle] pub extern fn free_string(p: *mut c_ch

It might be good to mention how to free the memory. By passing the pointer back to a rust function like #[no_mangle] pub extern fn free_string(p: *mut c_char) { unsafe { let _ = CString::from_raw(p); // optionally you could explicitly call drop, but // that is unnecessary, since it is automatically dropped // at end of scope } } Also the `into_raw` method on CString gives you a pointer while simultaneously taking ownership of the CString, so mem::forget isn't necessary if you use `into_raw` rather than `as_ptr`.