Expose cfg(futures_no_atomic_cas) as unstable public API

futures-channel/build.rs

@@ -2,9 +2,20 @@ use std::env;
 
 include!("no_atomic_cas.rs");
 
-// The rustc-cfg strings below are *not* public API. Please let us know by
-// opening a GitHub issue if your build environment requires some way to enable
-// these cfgs other than by executing our build script.
+// The rustc-cfg listed below are considered public API, but it is *unstable*
+// and outside of the normal semver guarantees:
+//
+// - `futures_no_atomic_cas`
+//      Assume the target does not have atomic CAS (compare-and-swap).
+//      The target that does not have atomic CAS is usually detected
+//      automatically by the build script, but you may need to enable it
+//      manually when building for custom targets or using non-cargo build
+//      systems that don't run the build script.
+//
+// With the exceptions mentioned above, the rustc-cfg strings below are
+// *not* public API. Please let us know by opening a GitHub issue if your build
+// environment requires some way to enable these cfgs other than by executing
+// our build script.
 fn main() {
     let target = match env::var("TARGET") {
         Ok(target) => target,
@@ -18,12 +29,12 @@ fn main() {
         }
     };
 
-    // Note that this is `no_atomic_cas`, not `has_atomic_cas`. This allows
-    // treating `cfg(target_has_atomic = "ptr")` as true when the build script
-    // doesn't run. This is needed for compatibility with non-cargo build
-    // systems that don't run build scripts.
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
     if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
-        println!("cargo:rustc-cfg=no_atomic_cas");
+        println!("cargo:rustc-cfg=futures_no_atomic_cas");
     }
 
     println!("cargo:rerun-if-changed=no_atomic_cas.rs");

futures-channel/src/lib.rs

@@ -20,7 +20,7 @@
 
 macro_rules! cfg_target_has_atomic {
     ($($item:item)*) => {$(
-        #[cfg(not(no_atomic_cas))]
+        #[cfg(not(futures_no_atomic_cas))]
         $item
     )*};
 }

futures-core/build.rs

@@ -2,9 +2,20 @@ use std::env;
 
 include!("no_atomic_cas.rs");
 
-// The rustc-cfg strings below are *not* public API. Please let us know by
-// opening a GitHub issue if your build environment requires some way to enable
-// these cfgs other than by executing our build script.
+// The rustc-cfg listed below are considered public API, but it is *unstable*
+// and outside of the normal semver guarantees:
+//
+// - `futures_no_atomic_cas`
+//      Assume the target does not have atomic CAS (compare-and-swap).
+//      The target that does not have atomic CAS is usually detected
+//      automatically by the build script, but you may need to enable it
+//      manually when building for custom targets or using non-cargo build
+//      systems that don't run the build script.
+//
+// With the exceptions mentioned above, the rustc-cfg strings below are
+// *not* public API. Please let us know by opening a GitHub issue if your build
+// environment requires some way to enable these cfgs other than by executing
+// our build script.
 fn main() {
     let target = match env::var("TARGET") {
         Ok(target) => target,
@@ -18,12 +29,12 @@ fn main() {
         }
     };
 
-    // Note that this is `no_atomic_cas`, not `has_atomic_cas`. This allows
-    // treating `cfg(target_has_atomic = "ptr")` as true when the build script
-    // doesn't run. This is needed for compatibility with non-cargo build
-    // systems that don't run build scripts.
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
     if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
-        println!("cargo:rustc-cfg=no_atomic_cas");
+        println!("cargo:rustc-cfg=futures_no_atomic_cas");
     }
 
     println!("cargo:rerun-if-changed=no_atomic_cas.rs");

futures-core/src/task/__internal/mod.rs

@@ -1,4 +1,4 @@
-#[cfg(not(no_atomic_cas))]
+#[cfg(not(futures_no_atomic_cas))]
 mod atomic_waker;
-#[cfg(not(no_atomic_cas))]
+#[cfg(not(futures_no_atomic_cas))]
 pub use self::atomic_waker::AtomicWaker;

futures-task/build.rs

@@ -2,9 +2,20 @@ use std::env;
 
 include!("no_atomic_cas.rs");
 
-// The rustc-cfg strings below are *not* public API. Please let us know by
-// opening a GitHub issue if your build environment requires some way to enable
-// these cfgs other than by executing our build script.
+// The rustc-cfg listed below are considered public API, but it is *unstable*
+// and outside of the normal semver guarantees:
+//
+// - `futures_no_atomic_cas`
+//      Assume the target does not have atomic CAS (compare-and-swap).
+//      The target that does not have atomic CAS is usually detected
+//      automatically by the build script, but you may need to enable it
+//      manually when building for custom targets or using non-cargo build
+//      systems that don't run the build script.
+//
+// With the exceptions mentioned above, the rustc-cfg strings below are
+// *not* public API. Please let us know by opening a GitHub issue if your build
+// environment requires some way to enable these cfgs other than by executing
+// our build script.
 fn main() {
     let target = match env::var("TARGET") {
         Ok(target) => target,
@@ -18,12 +29,12 @@ fn main() {
         }
     };
 
-    // Note that this is `no_atomic_cas`, not `has_atomic_cas`. This allows
-    // treating `cfg(target_has_atomic = "ptr")` as true when the build script
-    // doesn't run. This is needed for compatibility with non-cargo build
-    // systems that don't run build scripts.
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
     if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
-        println!("cargo:rustc-cfg=no_atomic_cas");
+        println!("cargo:rustc-cfg=futures_no_atomic_cas");
     }
 
     println!("cargo:rerun-if-changed=no_atomic_cas.rs");

futures-task/src/lib.rs

@@ -12,7 +12,7 @@ extern crate alloc;
 
 macro_rules! cfg_target_has_atomic {
     ($($item:item)*) => {$(
-        #[cfg(not(no_atomic_cas))]
+        #[cfg(not(futures_no_atomic_cas))]
         $item
     )*};
 }

futures-util/build.rs

@@ -2,9 +2,20 @@ use std::env;
 
 include!("no_atomic_cas.rs");
 
-// The rustc-cfg strings below are *not* public API. Please let us know by
-// opening a GitHub issue if your build environment requires some way to enable
-// these cfgs other than by executing our build script.
+// The rustc-cfg listed below are considered public API, but it is *unstable*
+// and outside of the normal semver guarantees:
+//
+// - `futures_no_atomic_cas`
+//      Assume the target does not have atomic CAS (compare-and-swap).
+//      The target that does not have atomic CAS is usually detected
+//      automatically by the build script, but you may need to enable it
+//      manually when building for custom targets or using non-cargo build
+//      systems that don't run the build script.
+//
+// With the exceptions mentioned above, the rustc-cfg strings below are
+// *not* public API. Please let us know by opening a GitHub issue if your build
+// environment requires some way to enable these cfgs other than by executing
+// our build script.
 fn main() {
     let target = match env::var("TARGET") {
         Ok(target) => target,
@@ -18,12 +29,12 @@ fn main() {
         }
     };
 
-    // Note that this is `no_atomic_cas`, not `has_atomic_cas`. This allows
-    // treating `cfg(target_has_atomic = "ptr")` as true when the build script
-    // doesn't run. This is needed for compatibility with non-cargo build
-    // systems that don't run build scripts.
+    // Note that this is `no_*`, not `has_*`. This allows treating
+    // `cfg(target_has_atomic = "ptr")` as true when the build script doesn't
+    // run. This is needed for compatibility with non-cargo build systems that
+    // don't run the build script.
     if NO_ATOMIC_CAS_TARGETS.contains(&&*target) {
-        println!("cargo:rustc-cfg=no_atomic_cas");
+        println!("cargo:rustc-cfg=futures_no_atomic_cas");
     }
 
     println!("cargo:rerun-if-changed=no_atomic_cas.rs");

futures-util/src/lib.rs

@@ -49,7 +49,7 @@ pub mod __private {
 
 macro_rules! cfg_target_has_atomic {
     ($($item:item)*) => {$(
-        #[cfg(not(no_atomic_cas))]
+        #[cfg(not(futures_no_atomic_cas))]
         $item
     )*};
 }

futures-util/src/stream/mod.rs

@@ -37,11 +37,11 @@ pub use self::stream::ReadyChunks;
 #[cfg_attr(docsrs, doc(cfg(feature = "sink")))]
 pub use self::stream::Forward;
 
-#[cfg(not(no_atomic_cas))]
+#[cfg(not(futures_no_atomic_cas))]
 #[cfg(feature = "alloc")]
 pub use self::stream::{BufferUnordered, Buffered, ForEachConcurrent, TryForEachConcurrent};
 
-#[cfg(not(no_atomic_cas))]
+#[cfg(not(futures_no_atomic_cas))]
 #[cfg(feature = "sink")]
 #[cfg_attr(docsrs, doc(cfg(feature = "sink")))]
 #[cfg(feature = "alloc")]
@@ -59,7 +59,7 @@ pub use self::try_stream::{
 #[cfg(feature = "std")]
 pub use self::try_stream::IntoAsyncRead;
 
-#[cfg(not(no_atomic_cas))]
+#[cfg(not(futures_no_atomic_cas))]
 #[cfg(feature = "alloc")]
 pub use self::try_stream::{TryBufferUnordered, TryBuffered};
 

futures-util/src/stream/stream/mod.rs

@@ -933,7 +933,7 @@ pub trait StreamExt: Stream {
     /// fut.await;
     /// # })
     /// ```
-    #[cfg(not(no_atomic_cas))]
+    #[cfg(not(futures_no_atomic_cas))]
     #[cfg(feature = "alloc")]
     fn for_each_concurrent<Fut, F>(
         self,
@@ -1066,7 +1066,7 @@ pub trait StreamExt: Stream {
     /// assert_eq!(Err(oneshot::Canceled), fut.await);
     /// # })
     /// ```
-    #[cfg(not(no_atomic_cas))]
+    #[cfg(not(futures_no_atomic_cas))]
     #[cfg(feature = "alloc")]
     fn try_for_each_concurrent<Fut, F, E>(
         self,
@@ -1293,7 +1293,7 @@ pub trait StreamExt: Stream {
     /// # Panics
     ///
     /// This method will panic if `n` is zero.
-    #[cfg(not(no_atomic_cas))]
+    #[cfg(not(futures_no_atomic_cas))]
     #[cfg(feature = "alloc")]
     fn buffered(self, n: usize) -> Buffered<Self>
     where
@@ -1342,7 +1342,7 @@ pub trait StreamExt: Stream {
     /// assert_eq!(buffered.next().await, None);
     /// # Ok::<(), i32>(()) }).unwrap();
     /// ```
-    #[cfg(not(no_atomic_cas))]
+    #[cfg(not(futures_no_atomic_cas))]
     #[cfg(feature = "alloc")]
     fn buffer_unordered(self, n: usize) -> BufferUnordered<Self>
     where
@@ -1509,7 +1509,7 @@ pub trait StreamExt: Stream {
     /// library is activated, and it is activated by default.
     #[cfg(feature = "sink")]
     #[cfg_attr(docsrs, doc(cfg(feature = "sink")))]
-    #[cfg(not(no_atomic_cas))]
+    #[cfg(not(futures_no_atomic_cas))]
     #[cfg(feature = "alloc")]
     fn split<Item>(self) -> (SplitSink<Self, Item>, SplitStream<Self>)
     where

futures-util/src/stream/try_stream/mod.rs

@@ -684,7 +684,7 @@ pub trait TryStreamExt: TryStream {
     /// assert_eq!(buffered.next().await, Some(Err("error in the stream")));
     /// # Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap();
     /// ```
-    #[cfg(not(no_atomic_cas))]
+    #[cfg(not(futures_no_atomic_cas))]
     #[cfg(feature = "alloc")]
     fn try_buffer_unordered(self, n: usize) -> TryBufferUnordered<Self>
     where
@@ -760,7 +760,7 @@ pub trait TryStreamExt: TryStream {
     /// assert_eq!(buffered.next().await, Some(Err("error in the stream")));
     /// # Ok::<(), Box<dyn std::error::Error>>(()) }).unwrap();
     /// ```
-    #[cfg(not(no_atomic_cas))]
+    #[cfg(not(futures_no_atomic_cas))]
     #[cfg(feature = "alloc")]
     fn try_buffered(self, n: usize) -> TryBuffered<Self>
     where