Use cfg(target_has_atomic) on no-std targets

Author: taiki-e

.github/workflows/ci.yml

@@ -230,42 +230,6 @@ jobs:
             --workspace --exclude futures-test \
             --features unstable --ignore-unknown-features
 
-  # When this job failed, run ci/no_atomic_cas.sh and commit result changes.
-  codegen:
-    runs-on: ubuntu-latest
-    permissions:
-      contents: write
-      pull-requests: write
-    steps:
-      - uses: actions/checkout@v4
-      - name: Install Rust
-        run: rustup update nightly && rustup default nightly
-      - run: ci/no_atomic_cas.sh
-      - run: git add -N . && git diff --exit-code
-        if: github.repository_owner != 'rust-lang' || github.event_name != 'schedule'
-      - id: diff
-        run: |
-          git config user.name "Taiki Endo"
-          git config user.email "[email protected]"
-          git add -N .
-          if ! git diff --exit-code; then
-              git add .
-              git commit -m "Update no_atomic_cas.rs"
-              echo "::set-output name=success::false"
-          fi
-        if: github.repository_owner == 'rust-lang' && github.event_name == 'schedule'
-      - uses: peter-evans/create-pull-request@v5
-        with:
-          title: Update no_atomic_cas.rs
-          body: |
-            Auto-generated by [create-pull-request][1]
-            [Please close and immediately reopen this pull request to run CI.][2]
-
-            [1]: https://github.com/peter-evans/create-pull-request
-            [2]: https://github.com/peter-evans/create-pull-request/blob/HEAD/docs/concepts-guidelines.md#workarounds-to-trigger-further-workflow-runs
-          branch: update-no-atomic-cas-rs
-        if: github.repository_owner == 'rust-lang' && github.event_name == 'schedule' && steps.diff.outputs.success == 'false'
-
   miri:
     name: cargo miri test
     runs-on: ubuntu-latest

ci/no_atomic_cas.sh

@@ -29,16 +29,16 @@
 #![allow(clippy::arc_with_non_send_sync)] // false positive https://github.com/rust-lang/rust-clippy/issues/11076
 #![allow(clippy::needless_pass_by_ref_mut)]
 
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "alloc")]
 extern crate alloc;
 
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "alloc")]
 mod lock;
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "std")]
 pub mod mpsc;
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "alloc")]
 pub mod oneshot;

futures-channel/build.rs

@@ -1,4 +1,7 @@
-#[cfg(any(not(futures_no_atomic_cas), feature = "portable-atomic"))]
+#[cfg_attr(target_os = "none", cfg(any(target_has_atomic = "ptr", feature = "portable-atomic")))]
 mod atomic_waker;
-#[cfg(any(not(futures_no_atomic_cas), feature = "portable-atomic"))]
+#[cfg_attr(
+    target_os = "none",
+    cfg(any(target_has_atomic = "ptr", feature = "portable-atomic"))
+)]
 pub use self::atomic_waker::AtomicWaker;

futures-channel/no_atomic_cas.rs

@@ -18,24 +18,24 @@ extern crate alloc;
 mod spawn;
 pub use crate::spawn::{LocalSpawn, Spawn, SpawnError};
 
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "alloc")]
 mod arc_wake;
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "alloc")]
 pub use crate::arc_wake::ArcWake;
 
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "alloc")]
 mod waker;
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "alloc")]
 pub use crate::waker::waker;
 
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "alloc")]
 mod waker_ref;
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 #[cfg(feature = "alloc")]
 pub use crate::waker_ref::{waker_ref, WakerRef};
 

futures-channel/src/lib.rs

@@ -168,7 +168,7 @@ mod if_alloc {
         }
     }
 
-    #[cfg(not(futures_no_atomic_cas))]
+    #[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
     impl<Sp: ?Sized + Spawn> Spawn for alloc::sync::Arc<Sp> {
         fn spawn_obj(&self, future: FutureObj<'static, ()>) -> Result<(), SpawnError> {
             (**self).spawn_obj(future)
@@ -179,7 +179,7 @@ mod if_alloc {
         }
     }
 
-    #[cfg(not(futures_no_atomic_cas))]
+    #[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
     impl<Sp: ?Sized + LocalSpawn> LocalSpawn for alloc::sync::Arc<Sp> {
         fn spawn_local_obj(&self, future: LocalFutureObj<'static, ()>) -> Result<(), SpawnError> {
             (**self).spawn_local_obj(future)

futures-core/build.rs

@@ -12,7 +12,7 @@ use core::task::{Context, Poll};
 
 use super::{assert_future, MaybeDone};
 
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 use crate::stream::{Collect, FuturesOrdered, StreamExt};
 
 pub(crate) fn iter_pin_mut<T>(slice: Pin<&mut [T]>) -> impl Iterator<Item = Pin<&mut T>> {
@@ -31,7 +31,7 @@ where
     kind: JoinAllKind<F>,
 }
 
-#[cfg(not(futures_no_atomic_cas))]
+#[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
 pub(crate) const SMALL: usize = 30;
 
 enum JoinAllKind<F>
@@ -41,7 +41,7 @@ where
     Small {
         elems: Pin<Box<[MaybeDone<F>]>>,
     },
-    #[cfg(not(futures_no_atomic_cas))]
+    #[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
     Big {
         fut: Collect<FuturesOrdered<F>, Vec<F::Output>>,
     },
@@ -57,7 +57,7 @@ where
             JoinAllKind::Small { ref elems } => {
                 f.debug_struct("JoinAll").field("elems", elems).finish()
             }
-            #[cfg(not(futures_no_atomic_cas))]
+            #[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
             JoinAllKind::Big { ref fut, .. } => fmt::Debug::fmt(fut, f),
         }
     }
@@ -106,15 +106,16 @@ where
 {
     let iter = iter.into_iter();
 
-    #[cfg(futures_no_atomic_cas)]
+    #[cfg(target_os = "none")]
+    #[cfg_attr(target_os = "none", cfg(not(target_has_atomic = "ptr")))]
     {
         let kind =
             JoinAllKind::Small { elems: iter.map(MaybeDone::Future).collect::<Box<[_]>>().into() };
 
         assert_future::<Vec<<I::Item as Future>::Output>, _>(JoinAll { kind })
     }
 
-    #[cfg(not(futures_no_atomic_cas))]
+    #[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
     {
         let kind = match iter.size_hint().1 {
             Some(max) if max <= SMALL => JoinAllKind::Small {
@@ -153,7 +154,7 @@ where
                     Poll::Pending
                 }
             }
-            #[cfg(not(futures_no_atomic_cas))]
+            #[cfg_attr(target_os = "none", cfg(target_has_atomic = "ptr"))]
             JoinAllKind::Big { fut } => Pin::new(fut).poll(cx),
         }
     }