diff options
| -rw-r--r-- | src/libcore/sync/atomic.rs | 74 | ||||
| -rw-r--r-- | src/libstd/lib.rs | 1 | ||||
| -rw-r--r-- | src/libstd/sys/wasm/alloc.rs | 4 | ||||
| -rw-r--r-- | src/libstd/sys/wasm/condvar_atomics.rs | 2 | ||||
| -rw-r--r-- | src/libstd/sys/wasm/mutex_atomics.rs | 4 |
5 files changed, 80 insertions, 5 deletions
diff --git a/src/libcore/sync/atomic.rs b/src/libcore/sync/atomic.rs index 820c1edf930..251d49db062 100644 --- a/src/libcore/sync/atomic.rs +++ b/src/libcore/sync/atomic.rs @@ -802,6 +802,43 @@ impl AtomicBool { pub fn fetch_xor(&self, val: bool, order: Ordering) -> bool { unsafe { atomic_xor(self.v.get(), val as u8, order) != 0 } } + + /// Returns a mutable pointer to the underlying [`bool`]. + /// + /// Doing non-atomic reads and writes on the resulting integer can be a data race. + /// This method is mostly useful for FFI, where the function signature may use + /// `*mut bool` instead of `&AtomicBool`. + /// + /// Returning an `*mut` pointer from a shared reference to this atomic is safe because the + /// atomic types work with interior mutability. All modifications of an atomic change the value + /// through a shared reference, and can do so safely as long as they use atomic operations. Any + /// use of the returned raw pointer requires an `unsafe` block and still has to uphold the same + /// restriction: operations on it must be atomic. + /// + /// [`bool`]: ../../../std/primitive.bool.html + /// + /// # Examples + /// + /// ```ignore (extern-declaration) + /// # fn main() { + /// use std::sync::atomic::AtomicBool; + /// extern { + /// fn my_atomic_op(arg: *mut bool); + /// } + /// + /// let mut atomic = AtomicBool::new(true); + /// unsafe { + /// my_atomic_op(atomic.as_mut_ptr()); + /// } + /// # } + /// ``` + #[inline] + #[unstable(feature = "atomic_mut_ptr", + reason = "recently added", + issue = "66893")] + pub fn as_mut_ptr(&self) -> *mut bool { + self.v.get() as *mut bool + } } #[cfg(target_has_atomic_load_store = "ptr")] @@ -1891,6 +1928,43 @@ assert_eq!(min_foo, 12); } } + doc_comment! { + concat!("Returns a mutable pointer to the underlying integer. + +Doing non-atomic reads and writes on the resulting integer can be a data race. +This method is mostly useful for FFI, where the function signature may use +`*mut ", stringify!($int_type), "` instead of `&", stringify!($atomic_type), "`. + +Returning an `*mut` pointer from a shared reference to this atomic is safe because the +atomic types work with interior mutability. All modifications of an atomic change the value +through a shared reference, and can do so safely as long as they use atomic operations. Any +use of the returned raw pointer requires an `unsafe` block and still has to uphold the same +restriction: operations on it must be atomic. + +# Examples + +```ignore (extern-declaration) +# fn main() { +", $extra_feature, "use std::sync::atomic::", stringify!($atomic_type), "; + +extern { + fn my_atomic_op(arg: *mut ", stringify!($int_type), "); +} + +let mut atomic = ", stringify!($atomic_type), "::new(1); +unsafe { + my_atomic_op(atomic.as_mut_ptr()); +} +# } +```"), + #[inline] + #[unstable(feature = "atomic_mut_ptr", + reason = "recently added", + issue = "66893")] + pub fn as_mut_ptr(&self) -> *mut $int_type { + self.v.get() + } + } } } } diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs index acf53f7f003..1dbb0c6ec83 100644 --- a/src/libstd/lib.rs +++ b/src/libstd/lib.rs @@ -234,6 +234,7 @@ #![feature(allocator_internals)] #![feature(allow_internal_unsafe)] #![feature(allow_internal_unstable)] +#![feature(atomic_mut_ptr)] #![feature(arbitrary_self_types)] #![feature(array_error_internals)] #![feature(asm)] diff --git a/src/libstd/sys/wasm/alloc.rs b/src/libstd/sys/wasm/alloc.rs index c1af6ec1262..05e55334ac0 100644 --- a/src/libstd/sys/wasm/alloc.rs +++ b/src/libstd/sys/wasm/alloc.rs @@ -67,7 +67,7 @@ mod lock { // // unsafe { // let r = core::arch::wasm32::i32_atomic_wait( - // &LOCKED as *const AtomicI32 as *mut i32, + // LOCKED.as_mut_ptr(), // 1, // expected value // -1, // timeout // ); @@ -143,7 +143,7 @@ mod lock { // // unsafe { // core::arch::wasm32::atomic_notify( - // &LOCKED as *const AtomicI32 as *mut i32, + // LOCKED.as_mut_ptr(), // 1, // only one thread // ); // } diff --git a/src/libstd/sys/wasm/condvar_atomics.rs b/src/libstd/sys/wasm/condvar_atomics.rs index 580d2121844..f452bbd3487 100644 --- a/src/libstd/sys/wasm/condvar_atomics.rs +++ b/src/libstd/sys/wasm/condvar_atomics.rs @@ -89,6 +89,6 @@ impl Condvar { #[inline] fn ptr(&self) -> *mut i32 { assert_eq!(mem::size_of::<usize>(), mem::size_of::<i32>()); - &self.cnt as *const AtomicUsize as *mut i32 + self.cnt.as_mut_ptr() as *mut i32 } } diff --git a/src/libstd/sys/wasm/mutex_atomics.rs b/src/libstd/sys/wasm/mutex_atomics.rs index 0e4f3d80aa9..cddd584dd22 100644 --- a/src/libstd/sys/wasm/mutex_atomics.rs +++ b/src/libstd/sys/wasm/mutex_atomics.rs @@ -56,7 +56,7 @@ impl Mutex { #[inline] fn ptr(&self) -> *mut i32 { assert_eq!(mem::size_of::<usize>(), mem::size_of::<i32>()); - &self.locked as *const AtomicUsize as *mut isize as *mut i32 + self.locked.as_mut_ptr() as *mut i32 } } @@ -145,6 +145,6 @@ impl ReentrantMutex { #[inline] fn ptr(&self) -> *mut i32 { - &self.owner as *const AtomicU32 as *mut i32 + self.owner.as_mut_ptr() as *mut i32 } } |