diff options
Diffstat (limited to 'src/libstd/thread')
| -rw-r--r-- | src/libstd/thread/mod.rs | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/src/libstd/thread/mod.rs b/src/libstd/thread/mod.rs index 200368be275..d807424129e 100644 --- a/src/libstd/thread/mod.rs +++ b/src/libstd/thread/mod.rs @@ -367,6 +367,26 @@ impl Builder { /// want to specify the stack size or the name of the thread, use this API /// instead. /// +/// As you can see in the signature of `spawn` there are two constraints on +/// both the closure given to `spawn` and its return value, let's explain them: +/// +/// - The `'static` constraint means that the closure and its return value +/// must have a lifetime of the whole program execution. The reason for this +/// is that threads can `detach` and outlive the lifetime they have been +/// created in. +/// Indeed if the thread, and by extension its return value, can outlive their +/// caller, we need to make sure that they will be valid afterwards, and since +/// we *can't* know when it will return we need to have them valid as long as +/// possible, that is until the end of the program, hence the `'static` +/// lifetime. +/// - The [`Send`] constraint is because the closure will need to be passed +/// *by value* from the thread where it is spawned to the new thread. Its +/// return value will need to be passed from the new thread to the thread +/// where it is `join`ed. +/// As a reminder, the [`Send`] marker trait, expresses that it is safe to be +/// passed from thread to thread. [`Sync`] expresses that it is safe to have a +/// reference be passed from thread to thread. +/// /// # Panics /// /// Panics if the OS fails to create a thread; use [`Builder::spawn`] @@ -433,6 +453,8 @@ impl Builder { /// [`panic`]: ../../std/macro.panic.html /// [`Builder::spawn`]: ../../std/thread/struct.Builder.html#method.spawn /// [`Builder`]: ../../std/thread/struct.Builder.html +/// [`Send`]: ../../std/marker/trait.Send.html +/// [`Sync`]: ../../std/marker/trait.Sync.html #[stable(feature = "rust1", since = "1.0.0")] pub fn spawn<F, T>(f: F) -> JoinHandle<T> where F: FnOnce() -> T, F: Send + 'static, T: Send + 'static |