Struct ChildLabelFn 

pub struct ChildLabelFn(pub Arc<dyn Fn(TaskId, &mut Labels) + 'static>);

A special label that can be used to set labels for a task when it is spawned.

By default, when a task or thread T is spawned, it inherits all labels from its parent. It’s often useful to modify or add new Labels to T. One approach is to put label changes at the beginning of the closure that is passed to spawn, but this approach has the drawback that the changes are applied only when T is first selected for execution, and the closure is invoked. To overcome this drawback, we introduce the ChildLabelFn label. If a parent task or thread has a ChildLabelFn set when it spawns a new child task or thread, the child’s label set at spawn time will be modified by applying the function inside the ChildLabelFn.

Example

The following example shows how a ChildLabelFn can be used to set up names for the next child(ren) that will be spawned by a parent task (see shuttle/tests/basic/labels.rs for runnable versions).

// In the parent, set up a `ChildLabelFn` that assigns a name to the child task
shuttle::check_dfs(|| {
  set_label_for_task(me(), ChildLabelFn(Arc::new(|_task_id, labels| { labels.insert(TaskName::from("ChildTask")); })));
  shuttle::thread::spawn(|| {
    assert_eq!(get_name_for_task(me()).unwrap(), TaskName::from("ChildTask")); // child task already has the name
    // ... rest of child
  }).join().unwrap();
}, None);

Tuple Fields

0: Arc<dyn Fn(TaskId, &mut Labels) + 'static>

Trait Implementations

impl Clone for ChildLabelFn

fn clone(&self) -> ChildLabelFn

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ChildLabelFn

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.