Provide 32 bit atomic impls for emscripten

serde/build.rs

@@ -14,8 +14,6 @@ fn main() {
     let target = env::var("TARGET").unwrap();
     let emscripten = target == "asmjs-unknown-emscripten" || target == "wasm32-unknown-emscripten";
 
-    let has_atomic_integers = target_has_at_least_atomic_u64(&target);
-
     // std::collections::Bound was stabilized in Rust 1.17
     // but it was moved to core::ops later in Rust 1.26:
     // https://doc.rust-lang.org/core/ops/enum.Bound.html
@@ -71,8 +69,23 @@ fn main() {
         println!("cargo:rustc-cfg=num_nonzero");
     }
 
-    if minor >= 34 && has_atomic_integers {
+    if minor >= 34 {
-        println!("cargo:rustc-cfg=std_integer_atomics");
+        // 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 src/librustc_target/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");
+        let has_atomic32 = has_atomic64 || emscripten;
+        if has_atomic64 {
+            println!("cargo:rustc-cfg=std_atomic64");
+        }
+        if has_atomic32 {
+            println!("cargo:rustc-cfg=std_atomic");
+        }
     }
 }
 
@@ -104,17 +117,3 @@ fn rustc_minor_version() -> Option<u32> {
 
     u32::from_str(next).ok()
 }
-
-fn target_has_at_least_atomic_u64(target: &str) -> bool {
-    // The cfg variable target_has_atomic is unstable
-    // so this data comes from the  src/librustc_target/spec/*.rs
-    // files in the rust source. Generally, it's 64-bit platforms
-    // plus i686.
-    if 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") {
-        true
-    } else {
-        false
-    }
-}

serde/src/de/impls.rs

@@ -2546,7 +2546,7 @@ where
     }
 }
 
-#[cfg(all(feature = "std", std_integer_atomics))]
+#[cfg(all(feature = "std", std_atomic))]
 macro_rules! atomic_impl {
     ($($ty:ident)*) => {
         $(
@@ -2562,14 +2562,14 @@ macro_rules! atomic_impl {
     };
 }
 
-#[cfg(all(feature = "std", std_integer_atomics))]
+#[cfg(all(feature = "std", std_atomic))]
 atomic_impl! {
     AtomicBool
     AtomicI8 AtomicI16 AtomicI32 AtomicIsize
     AtomicU8 AtomicU16 AtomicU32 AtomicUsize
 }
 
-#[cfg(all(feature = "std", std_integer_atomics, not(target_os = "emscripten")))]
+#[cfg(all(feature = "std", std_atomic64))]
 atomic_impl! {
     AtomicI64 AtomicU64
 }

serde/src/lib.rs

@@ -212,12 +212,12 @@ mod lib {
     #[cfg(range_inclusive)]
     pub use self::core::ops::RangeInclusive;
 
-    #[cfg(all(feature = "std", std_integer_atomics))]
+    #[cfg(all(feature = "std", std_atomic))]
     pub use std::sync::atomic::{
         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_atomic64))]
     pub use std::sync::atomic::{AtomicI64, AtomicU64};
 
     #[cfg(any(core_duration, feature = "std"))]

serde/src/ser/impls.rs

@@ -842,7 +842,7 @@ where
 
 ////////////////////////////////////////////////////////////////////////////////
 
-#[cfg(all(feature = "std", std_integer_atomics))]
+#[cfg(all(feature = "std", std_atomic))]
 macro_rules! atomic_impl {
     ($($ty:ident)*) => {
         $(
@@ -858,14 +858,14 @@ macro_rules! atomic_impl {
     }
 }
 
-#[cfg(all(feature = "std", std_integer_atomics))]
+#[cfg(all(feature = "std", std_atomic))]
 atomic_impl! {
     AtomicBool
     AtomicI8 AtomicI16 AtomicI32 AtomicIsize
     AtomicU8 AtomicU16 AtomicU32 AtomicUsize
 }
 
-#[cfg(all(feature = "std", std_integer_atomics, not(target_os = "emscripten")))]
+#[cfg(all(feature = "std", std_atomic64))]
 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(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(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(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(target_arch = "x86_64")]
 declare_tests! {
     test_atomic64 {
         AtomicI64::new(-4295032832i64) => &[Token::I64(-4295032832i64)],