diff options
Diffstat (limited to 'library/alloc/src')
| -rw-r--r-- | library/alloc/src/sync.rs | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs index 104cb35c23b..c62f8e5b70f 100644 --- a/library/alloc/src/sync.rs +++ b/library/alloc/src/sync.rs @@ -84,9 +84,29 @@ macro_rules! acquire { /// /// Shared references in Rust disallow mutation by default, and `Arc` is no /// exception: you cannot generally obtain a mutable reference to something -/// inside an `Arc`. If you need to mutate through an `Arc`, use -/// [`Mutex`][mutex], [`RwLock`][rwlock], or one of the [`Atomic`][atomic] -/// types. +/// inside an `Arc`. If you do need to mutate through an `Arc`, you have several options: +/// +/// 1. Use interior mutability with synchronization primitives like [`Mutex`][mutex], +/// [`RwLock`][rwlock], or one of the [`Atomic`][atomic] types. +/// +/// 2. Use clone-on-write semantics with [`Arc::make_mut`] which provides efficient mutation +/// without requiring interior mutability. This approach clones the data only when +/// needed (when there are multiple references) and can be more efficient when mutations +/// are infrequent. +/// +/// 3. Use [`Arc::get_mut`] when you know your `Arc` is not shared (has a reference count of 1), +/// which provides direct mutable access to the inner value without any cloning. +/// +/// ``` +/// use std::sync::Arc; +/// +/// let mut data = Arc::new(vec![1, 2, 3]); +/// +/// // This will clone the vector only if there are other references to it +/// Arc::make_mut(&mut data).push(4); +/// +/// assert_eq!(*data, vec![1, 2, 3, 4]); +/// ``` /// /// **Note**: This type is only available on platforms that support atomic /// loads and stores of pointers, which includes all platforms that support |