bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Rollup merge of #136300 - RalfJung:compare-and-swap, r=joboet

Browse source 
atomic: extend compare_and_swap migration docs

Fixes https://github.com/rust-lang/rust/issues/80486
This commit is contained in:
Jacob Pratt 2025-01-31 00:26:32 -05:00 • committed by GitHub
commit e2a73ab7ad
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
1 changed files with 18 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

18
library/core/src/sync/atomic.rs
View file

@ -716,6 +716,12 @@ impl AtomicBool {
/// AcqRel | AcqRel | Acquire
/// SeqCst | SeqCst | SeqCst
///
/// `compare_and_swap` and `compare_exchange` also differ in their return type. You can use
/// `compare_exchange(...).unwrap_or_else(|x| x)` to recover the behavior of `compare_and_swap`,
/// but in most cases it is more idiomatic to check whether the return value is `Ok` or `Err`
/// rather than to infer success vs failure based on the value that was read.
///
/// During migration, consider whether it makes sense to use `compare_exchange_weak` instead.
/// `compare_exchange_weak` is allowed to fail spuriously even when the comparison succeeds,
/// which allows the compiler to generate better assembly code when the compare and swap
/// is used in a loop.
@ -1651,6 +1657,12 @@ impl<T> AtomicPtr<T> {
/// AcqRel | AcqRel | Acquire
/// SeqCst | SeqCst | SeqCst
///
/// `compare_and_swap` and `compare_exchange` also differ in their return type. You can use
/// `compare_exchange(...).unwrap_or_else(|x| x)` to recover the behavior of `compare_and_swap`,
/// but in most cases it is more idiomatic to check whether the return value is `Ok` or `Err`
/// rather than to infer success vs failure based on the value that was read.
///
/// During migration, consider whether it makes sense to use `compare_exchange_weak` instead.
/// `compare_exchange_weak` is allowed to fail spuriously even when the comparison succeeds,
/// which allows the compiler to generate better assembly code when the compare and swap
/// is used in a loop.
@ -2771,6 +2783,12 @@ macro_rules! atomic_int {
/// AcqRel | AcqRel | Acquire
/// SeqCst | SeqCst | SeqCst
///
/// `compare_and_swap` and `compare_exchange` also differ in their return type. You can use
/// `compare_exchange(...).unwrap_or_else(|x| x)` to recover the behavior of `compare_and_swap`,
/// but in most cases it is more idiomatic to check whether the return value is `Ok` or `Err`
/// rather than to infer success vs failure based on the value that was read.
///
/// During migration, consider whether it makes sense to use `compare_exchange_weak` instead.
/// `compare_exchange_weak` is allowed to fail spuriously even when the comparison succeeds,
/// which allows the compiler to generate better assembly code when the compare and swap
/// is used in a loop.