Null pointers are optional

Author: oli-obk

src/libstd/ffi/c_str.rs

@@ -137,7 +137,8 @@ pub struct CString {
 ///
 /// Note that this structure is `repr(C)` and is can be
 /// placed in the signatures of FFI functions. A `&CStr` is equivalent to `*const c_char`,
-/// but offers a richer API.
+/// but offers a richer API. If you want to handle null pointers, too, using an
+/// `Option<&CStr>` will work.
 ///
 /// # Examples
 ///