Provide 64 bit atomics on x86 and x86_64 only

serde/build.rs

@@ -13,6 +13,8 @@ fn main() {
 
     let target = env::var("TARGET").unwrap();
     let emscripten = target == "asmjs-unknown-emscripten" || target == "wasm32-unknown-emscripten";
+    let x86 = target.starts_with("x86-");
+    let x86_64 = target.starts_with("x86_64-");
 
     // std::collections::Bound was stabilized in Rust 1.17
     // but it was moved to core::ops later in Rust 1.26:
@@ -69,8 +71,15 @@ fn main() {
         println!("cargo:rustc-cfg=num_nonzero");
     }
 
-    if minor >= 34 {
+    // Whitelist of archs that support std::sync::atomic module. Ideally we
+    // would use #[cfg(target_has_atomic = "...")] but it is not stable yet.
+    let has_atomic = x86 || x86_64 || emscripten;
+    let has_atomic_64 = x86 || x86_64;
+    if minor >= 34 && has_atomic {
         println!("cargo:rustc-cfg=std_integer_atomics");
+        if has_atomic_64 {
+            println!("cargo:rustc-cfg=std_integer_atomics_64");
+        }
     }
 }
 

serde/src/de/impls.rs

@@ -2569,7 +2569,7 @@ atomic_impl! {
     AtomicU8 AtomicU16 AtomicU32 AtomicUsize
 }
 
-#[cfg(all(feature = "std", std_integer_atomics, not(target_os = "emscripten")))]
+#[cfg(all(feature = "std", std_integer_atomics_64))]
 atomic_impl! {
     AtomicI64 AtomicU64
 }

serde/src/lib.rs

@@ -217,7 +217,7 @@ mod lib {
         AtomicBool, AtomicI16, AtomicI32, AtomicI8, AtomicIsize, AtomicU16, AtomicU32, AtomicU8,
         AtomicUsize, Ordering,
     };
-    #[cfg(all(feature = "std", std_integer_atomics, not(target_os = "emscripten")))]
+    #[cfg(all(feature = "std", std_integer_atomics_64))]
     pub use std::sync::atomic::{AtomicI64, AtomicU64};
 
     #[cfg(any(core_duration, feature = "std"))]

serde/src/ser/impls.rs

@@ -865,7 +865,7 @@ atomic_impl! {
     AtomicU8 AtomicU16 AtomicU32 AtomicUsize
 }
 
-#[cfg(all(feature = "std", std_integer_atomics, not(target_os = "emscripten")))]
+#[cfg(all(feature = "std", std_integer_atomics_64))]
 atomic_impl! {
     AtomicI64 AtomicU64
 }

test_suite/tests/test_de.rs

@@ -17,7 +17,7 @@ use std::sync::atomic::{
 use std::sync::{Arc, Weak as ArcWeak};
 use std::time::{Duration, UNIX_EPOCH};
 
-#[cfg(not(target_os = "emscripten"))]
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 use std::sync::atomic::{AtomicI64, AtomicU64};
 
 use fnv::FnvHasher;
@@ -1181,7 +1181,7 @@ fn test_atomics() {
     test(AtomicU32::load, 131072u32, Token::U32(131072u32));
     test(AtomicUsize::load, 131072usize, Token::U32(131072));
 
-    #[cfg(not(target_os = "emscripten"))]
+    #[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
     {
         test(AtomicI64::load, -8589934592, Token::I64(-8589934592));
         test(AtomicU64::load, 8589934592u64, Token::U64(8589934592));

test_suite/tests/test_ser.rs

@@ -19,7 +19,7 @@ use std::time::{Duration, UNIX_EPOCH};
 
 #[cfg(unix)]
 use std::str;
-#[cfg(not(target_os = "emscripten"))]
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 use std::sync::atomic::{AtomicI64, AtomicU64};
 
 use fnv::FnvHasher;
@@ -504,7 +504,7 @@ declare_tests! {
     }
 }
 
-#[cfg(not(target_os = "emscripten"))]
+#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
 declare_tests! {
     test_atomic64 {
         AtomicI64::new(-4295032832i64) => &[Token::I64(-4295032832i64)],