Add check for rust version

serde/build.rs

@@ -114,6 +114,11 @@ fn main() {
             println!("cargo:rustc-cfg=no_std_atomic");
         }
     }
+
+    // Support for core::ffi::CStr and alloc::ffi::CString stabilized in Rust 1.64.
+    if minor < 64 {
+        println!("cargo:rustc-cfg=no_core_cstr");
+    }
 }
 
 fn rustc_minor_version() -> Option<u32> {

serde/src/de/impls.rs

@@ -666,10 +666,10 @@ impl<'de: 'a, 'a> Deserialize<'de> for &'a [u8] {
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", all(not(no_core_cstr), feature = "alloc")))]
 struct CStringVisitor;
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", all(not(no_core_cstr), feature = "alloc")))]
 impl<'de> Visitor<'de> for CStringVisitor {
     type Value = CString;
 
@@ -720,7 +720,7 @@ impl<'de> Visitor<'de> for CStringVisitor {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", all(not(no_core_cstr), feature = "alloc")))]
 impl<'de> Deserialize<'de> for CString {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where
@@ -747,7 +747,7 @@ macro_rules! forwarded_impl {
     }
 }
 
-#[cfg(all(feature = "std", not(no_de_boxed_c_str)))]
+#[cfg(all(any(feature = "std", all(not(no_core_cstr), feature = "alloc")), not(no_de_boxed_c_str)))]
 forwarded_impl!((), Box<CStr>, CString::into_boxed_c_str);
 
 #[cfg(not(no_core_reverse))]

serde/src/lib.rs

@@ -176,7 +176,6 @@ mod lib {
     pub use self::core::clone::{self, Clone};
     pub use self::core::convert::{self, From, Into};
     pub use self::core::default::{self, Default};
-    pub use self::core::ffi::CStr;
     pub use self::core::fmt::{self, Debug, Display};
     pub use self::core::marker::{self, PhantomData};
     pub use self::core::num::Wrapping;
@@ -219,10 +218,15 @@ mod lib {
     #[cfg(feature = "std")]
     pub use std::collections::{BTreeMap, BTreeSet, BinaryHeap, LinkedList, VecDeque};
 
-    #[cfg(all(feature = "alloc", not(feature = "std")))]
+    #[cfg(all(not(no_core_cstr), not(feature = "std")))]
+    pub use core::ffi::CStr;
+    #[cfg(feature = "std")]
+    pub use std::ffi::CStr;
+
+    #[cfg(all(not(no_core_cstr), feature = "alloc", not(feature = "std")))]
     pub use alloc::ffi::{CString};
     #[cfg(feature = "std")]
-    pub use std::ffi::{CString};
+    pub use std::ffi::CString;
 
     #[cfg(feature = "std")]
     pub use std::{error, net};

serde/src/ser/impls.rs

@@ -72,7 +72,7 @@ impl<'a> Serialize for fmt::Arguments<'a> {
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", not(no_core_cstr)))]
 impl Serialize for CStr {
     #[inline]
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
@@ -83,7 +83,7 @@ impl Serialize for CStr {
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", all(not(no_core_cstr), feature = "alloc")))]
 impl Serialize for CString {
     #[inline]
     fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>