Add Deserialize impl for CStr

Fixes #810

serde/src/de/impls.rs

@@ -27,6 +27,8 @@ use std::path;
 use core::str;
 #[cfg(feature = "std")]
 use std::ffi::CString;
+#[cfg(all(feature = "std", feature="unstable"))]
+use std::ffi::CStr;
 
 #[cfg(feature = "std")]
 use std::rc::Rc;
@@ -300,6 +302,16 @@ impl Deserialize for String {
 
 ///////////////////////////////////////////////////////////////////////////////
 
+#[cfg(all(feature = "std", feature="unstable"))]
+impl Deserialize for Box<CStr> {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+        where D: Deserializer
+    {
+        let s = try!(CString::deserialize(deserializer));
+        Ok(s.into_boxed_c_str())
+    }
+}
+
 #[cfg(feature = "std")]
 impl Deserialize for CString {
     fn deserialize<D>(deserializer: D) -> Result<CString, D::Error>

serde/src/lib.rs

@@ -61,7 +61,7 @@
 
 #![doc(html_root_url="https://docs.serde.rs")]
 #![cfg_attr(not(feature = "std"), no_std)]
-#![cfg_attr(feature = "unstable", feature(inclusive_range, nonzero, specialization, zero_one))]
+#![cfg_attr(feature = "unstable", feature(inclusive_range, nonzero, specialization, zero_one, into_boxed_c_str))]
 #![cfg_attr(feature = "alloc", feature(alloc))]
 #![cfg_attr(feature = "collections", feature(collections))]
 #![cfg_attr(feature = "cargo-clippy", allow(linkedlist, type_complexity, doc_markdown))]