const {

// Copy into a vector, since we can't sort an unordered_set in-place.

std::vector<CleanupHookCallback> callbacks(cleanup_hooks_.begin(),

cleanup_hooks_.end());

// We can't erase the copied elements from `cleanup_hooks_` yet, because we

// need to be able to check whether they were un-scheduled by another hook.

std::sort(callbacks.begin(),

callbacks.end(),

[](const CleanupHookCallback& a, const CleanupHookCallback& b) {

// Sort in descending order so that the most recently inserted

// callbacks are run first.

return a.insertion_order_counter_ > b.insertion_order_counter_;

});

return callbacks;

std::vector<CleanupHookCallback> callbacks = GetOrdered();

for (const CleanupHookCallback& cb : callbacks) {

if (cleanup_hooks_.count(cb) == 0) {

// This hook was removed from the `cleanup_hooks_` set during another

// hook that was run earlier. Nothing to do here.

continue;

}

cb.fn_(cb.arg_);

cleanup_hooks_.erase(cb);

}