Function conc::add_garbage

pub fn add_garbage<T: Sync>(ptr: &'static T, dtor: fn(_: &'static T))

Declare a pointer unreachable garbage to be deleted eventually.

This adds ptr to the queue of garbage, which eventually will be destroyed through its destructor given in dtor. This is ensured to happen at some point after the last guard protecting the pointer is dropped.

It is legal for ptr to be invalidated by dtor, such that accessing it is undefined after dtor has been run. This means that dtor can safely (there are exceptions, see below) run a destructor of ptr's data.

Unreachability criterion

If you invalidate ptr in the destructor, it is extremely important that ptr is no longer reachable from any data structure: It should be impossible to create new guard representing ptr from now on, as such thing can mean that new guards can be created after it is dropped causing use-after-free.

Constraints

The T: Sync constraint is added to account for the fact that dtor might be called in another thread, meaning that it could cause thread-insafety if the pointer couldn't be shared.

Destruction

If the destructor provided panics under execution, it will cause panic in the garbage collection, and the destructor won't run again.