Made error messages when using portable_atomic without appropriate cf…

…g flag easier to understand

src/lib.rs

@@ -68,34 +68,37 @@ extern crate portable_atomic;
 
 #[cfg(not(feature = "portable_atomic"))]
 use core::sync::atomic;
-#[cfg(feature = "portable_atomic")]
+#[cfg(all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))]
 use portable_atomic as atomic;
 
-#[cfg(feature = "barrier")]
+#[cfg(all(feature = "portable_atomic", not(portable_atomic_unsafe_assume_single_core)))]
+core::compile_error!("The feature \"portable_atomic\" requires the \"portable_atomic_unsafe_assume_single_core\" cfg flag to be enabled. See https://docs.rs/portable-atomic/latest/portable_atomic/#optional-cfg.");
+
+#[cfg(all(feature = "barrier", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "barrier")))]
 pub mod barrier;
-#[cfg(feature = "lazy")]
+#[cfg(all(feature = "lazy", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "lazy")))]
 pub mod lazy;
-#[cfg(feature = "mutex")]
+#[cfg(all(feature = "mutex", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "mutex")))]
 pub mod mutex;
-#[cfg(feature = "once")]
+#[cfg(all(feature = "once", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "once")))]
 pub mod once;
 pub mod relax;
-#[cfg(feature = "rwlock")]
+#[cfg(all(feature = "rwlock", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "rwlock")))]
 pub mod rwlock;
 
-#[cfg(feature = "mutex")]
+#[cfg(all(feature = "mutex", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "mutex")))]
 pub use mutex::MutexGuard;
 #[cfg(feature = "std")]
 #[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 pub use relax::Yield;
 pub use relax::{RelaxStrategy, Spin};
-#[cfg(feature = "rwlock")]
+#[cfg(all(feature = "rwlock", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "rwlock")))]
 pub use rwlock::RwLockReadGuard;
 
@@ -107,39 +110,39 @@ pub use rwlock::RwLockReadGuard;
 ///
 /// A note for advanced users: this alias exists to avoid subtle type inference errors due to the default relax
 /// strategy type parameter. If you need a non-default relax strategy, use the fully-qualified path.
-#[cfg(feature = "barrier")]
+#[cfg(all(feature = "barrier", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "barrier")))]
 pub type Barrier = crate::barrier::Barrier;
 
 /// A value which is initialized on the first access. See [`lazy::Lazy`] for documentation.
 ///
 /// A note for advanced users: this alias exists to avoid subtle type inference errors due to the default relax
 /// strategy type parameter. If you need a non-default relax strategy, use the fully-qualified path.
-#[cfg(feature = "lazy")]
+#[cfg(all(feature = "lazy", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "lazy")))]
 pub type Lazy<T, F = fn() -> T> = crate::lazy::Lazy<T, F>;
 
 /// A primitive that synchronizes the execution of multiple threads. See [`mutex::Mutex`] for documentation.
 ///
 /// A note for advanced users: this alias exists to avoid subtle type inference errors due to the default relax
 /// strategy type parameter. If you need a non-default relax strategy, use the fully-qualified path.
-#[cfg(feature = "mutex")]
+#[cfg(all(feature = "mutex", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "mutex")))]
 pub type Mutex<T> = crate::mutex::Mutex<T>;
 
 /// A primitive that provides lazy one-time initialization. See [`once::Once`] for documentation.
 ///
 /// A note for advanced users: this alias exists to avoid subtle type inference errors due to the default relax
 /// strategy type parameter. If you need a non-default relax strategy, use the fully-qualified path.
-#[cfg(feature = "once")]
+#[cfg(all(feature = "once", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "once")))]
 pub type Once<T = ()> = crate::once::Once<T>;
 
 /// A lock that provides data access to either one writer or many readers. See [`rwlock::RwLock`] for documentation.
 ///
 /// A note for advanced users: this alias exists to avoid subtle type inference errors due to the default relax
 /// strategy type parameter. If you need a non-default relax strategy, use the fully-qualified path.
-#[cfg(feature = "rwlock")]
+#[cfg(all(feature = "rwlock", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "rwlock")))]
 pub type RwLock<T> = crate::rwlock::RwLock<T>;
 
@@ -148,15 +151,15 @@ pub type RwLock<T> = crate::rwlock::RwLock<T>;
 ///
 /// A note for advanced users: this alias exists to avoid subtle type inference errors due to the default relax
 /// strategy type parameter. If you need a non-default relax strategy, use the fully-qualified path.
-#[cfg(feature = "rwlock")]
+#[cfg(all(feature = "rwlock", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "rwlock")))]
 pub type RwLockUpgradableGuard<'a, T> = crate::rwlock::RwLockUpgradableGuard<'a, T>;
 
 /// A guard that provides mutable data access. See [`rwlock::RwLockWriteGuard`] for documentation.
 ///
 /// A note for advanced users: this alias exists to avoid subtle type inference errors due to the default relax
 /// strategy type parameter. If you need a non-default relax strategy, use the fully-qualified path.
-#[cfg(feature = "rwlock")]
+#[cfg(all(feature = "rwlock", any(not(feature = "portable_atomic"), all(feature = "portable_atomic", portable_atomic_unsafe_assume_single_core))))]
 #[cfg_attr(docsrs, doc(cfg(feature = "rwlock")))]
 pub type RwLockWriteGuard<'a, T> = crate::rwlock::RwLockWriteGuard<'a, T>;