Merge pull request #2337 from badboy/use-target_has_atomic-when-available

Use `target_has_atomic` on Rust 1.60+ to enable atomic (de)serialization

Author: dtolnay

serde/build.rs

@@ -95,19 +95,23 @@ fn main() {
     // Whitelist of archs that support std::sync::atomic module. Ideally we
     // would use #[cfg(target_has_atomic = "...")] but it is not stable yet.
     // Instead this is based on rustc's compiler/rustc_target/src/spec/*.rs.
-    let has_atomic64 = target.starts_with("x86_64")
-        || target.starts_with("i686")
-        || target.starts_with("aarch64")
-        || target.starts_with("powerpc64")
-        || target.starts_with("sparc64")
-        || target.starts_with("mips64el")
-        || target.starts_with("riscv64");
-    let has_atomic32 = has_atomic64 || emscripten;
-    if minor < 34 || !has_atomic64 {
-        println!("cargo:rustc-cfg=no_std_atomic64");
-    }
-    if minor < 34 || !has_atomic32 {
-        println!("cargo:rustc-cfg=no_std_atomic");
+    if minor >= 60 {
+        println!("cargo:rustc-cfg=use_target_has_atomic");
+    } else {
+        let has_atomic64 = target.starts_with("x86_64")
+            || target.starts_with("i686")
+            || target.starts_with("aarch64")
+            || target.starts_with("powerpc64")
+            || target.starts_with("sparc64")
+            || target.starts_with("mips64el")
+            || target.starts_with("riscv64");
+        let has_atomic32 = has_atomic64 || emscripten;
+        if minor < 34 || !has_atomic64 {
+            println!("cargo:rustc-cfg=no_std_atomic64");
+        }
+        if minor < 34 || !has_atomic32 {
+            println!("cargo:rustc-cfg=no_std_atomic");
+        }
     }
 }
 

serde/src/de/impls.rs

@@ -2660,7 +2660,7 @@ where
     }
 }
 
-#[cfg(all(feature = "std", not(no_std_atomic)))]
+#[cfg(all(feature = "std", not(use_target_has_atomic), not(no_std_atomic)))]
 macro_rules! atomic_impl {
     ($($ty:ident)*) => {
         $(
@@ -2676,18 +2676,50 @@ macro_rules! atomic_impl {
     };
 }
 
-#[cfg(all(feature = "std", not(no_std_atomic)))]
+#[cfg(all(feature = "std", use_target_has_atomic))]
+macro_rules! atomic_impl {
+    ( $( $ty:ident $size:expr ),* ) => {
+        $(
+            #[cfg(target_has_atomic = $size)]
+            impl<'de> Deserialize<'de> for $ty {
+                fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+                where
+                    D: Deserializer<'de>,
+                {
+                    Deserialize::deserialize(deserializer).map(Self::new)
+                }
+            }
+        )*
+    };
+}
+
+#[cfg(all(feature = "std", not(use_target_has_atomic), not(no_std_atomic)))]
 atomic_impl! {
     AtomicBool
     AtomicI8 AtomicI16 AtomicI32 AtomicIsize
     AtomicU8 AtomicU16 AtomicU32 AtomicUsize
 }
 
-#[cfg(all(feature = "std", not(no_std_atomic64)))]
+#[cfg(all(feature = "std", not(use_target_has_atomic), not(no_std_atomic64)))]
 atomic_impl! {
     AtomicI64 AtomicU64
 }
 
+#[cfg(all(feature = "std", use_target_has_atomic))]
+atomic_impl! {
+    AtomicBool "8",
+    AtomicI8 "8",
+    AtomicI16 "16",
+    AtomicI32 "32",
+    AtomicI64 "64",
+    AtomicIsize "ptr",
+    AtomicU8 "8",
+    AtomicU16 "16",
+    AtomicU32 "32",
+    AtomicU64 "64",
+    AtomicUsize "ptr"
+}
+
 #[cfg(feature = "std")]
 struct FromStrVisitor<T> {
     expecting: &'static str,

serde/src/lib.rs

@@ -236,14 +236,27 @@ mod lib {
     #[cfg(not(no_range_inclusive))]
     pub use self::core::ops::RangeInclusive;
 
-    #[cfg(all(feature = "std", not(no_std_atomic)))]
+    #[cfg(all(feature = "std", not(use_target_has_atomic), not(no_std_atomic)))]
     pub use std::sync::atomic::{
         AtomicBool, AtomicI16, AtomicI32, AtomicI8, AtomicIsize, AtomicU16, AtomicU32, AtomicU8,
         AtomicUsize, Ordering,
     };
-    #[cfg(all(feature = "std", not(no_std_atomic64)))]
+    #[cfg(all(feature = "std", not(use_target_has_atomic), not(no_std_atomic64)))]
     pub use std::sync::atomic::{AtomicI64, AtomicU64};
 
+    #[cfg(all(feature = "std", use_target_has_atomic))]
+    pub use std::sync::atomic::Ordering;
+    #[cfg(all(feature = "std", use_target_has_atomic, target_has_atomic = "8"))]
+    pub use std::sync::atomic::{AtomicBool, AtomicI8, AtomicU8};
+    #[cfg(all(feature = "std", use_target_has_atomic, target_has_atomic = "16"))]
+    pub use std::sync::atomic::{AtomicI16, AtomicU16};
+    #[cfg(all(feature = "std", use_target_has_atomic, target_has_atomic = "32"))]
+    pub use std::sync::atomic::{AtomicI32, AtomicU32};
+    #[cfg(all(feature = "std", use_target_has_atomic, target_has_atomic = "64"))]
+    pub use std::sync::atomic::{AtomicI64, AtomicU64};
+    #[cfg(all(feature = "std", use_target_has_atomic, target_has_atomic = "ptr"))]
+    pub use std::sync::atomic::{AtomicUsize, AtomicIsize};
+
     #[cfg(any(feature = "std", not(no_core_duration)))]
     pub use self::core::time::Duration;
 }

serde/src/ser/impls.rs

@@ -945,7 +945,7 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(all(feature = "std", not(no_std_atomic)))]
+#[cfg(all(feature = "std", not(use_target_has_atomic), not(no_std_atomic)))]
 macro_rules! atomic_impl {
     ($($ty:ident)*) => {
         $(
@@ -962,14 +962,47 @@ macro_rules! atomic_impl {
     }
 }
 
-#[cfg(all(feature = "std", not(no_std_atomic)))]
+#[cfg(all(feature = "std", use_target_has_atomic))]
+macro_rules! atomic_impl {
+    ( $( $ty:ident $size:expr ),* ) => {
+        $(
+            #[cfg(target_has_atomic = $size)]
+            impl Serialize for $ty {
+                fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+                where
+                    S: Serializer,
+                {
+                    // Matches the atomic ordering used in libcore for the Debug impl
+                    self.load(Ordering::Relaxed).serialize(serializer)
+                }
+            }
+        )*
+    }
+}
+
+#[cfg(all(feature = "std", not(use_target_has_atomic), not(no_std_atomic)))]
 atomic_impl! {
     AtomicBool
     AtomicI8 AtomicI16 AtomicI32 AtomicIsize
     AtomicU8 AtomicU16 AtomicU32 AtomicUsize
 }
 
-#[cfg(all(feature = "std", not(no_std_atomic64)))]
+#[cfg(all(feature = "std", not(use_target_has_atomic), not(no_std_atomic64)))]
 atomic_impl! {
     AtomicI64 AtomicU64
 }
+
+#[cfg(all(feature = "std", use_target_has_atomic))]
+atomic_impl! {
+    AtomicBool "8",
+    AtomicI8 "8",
+    AtomicI16 "16",
+    AtomicI32 "32",
+    AtomicI64 "64",
+    AtomicIsize "ptr",
+    AtomicU8 "8",
+    AtomicU16 "16",
+    AtomicU32 "32",
+    AtomicU64 "64",
+    AtomicUsize "ptr"
+}