Refer to:
void reset_() noexcept {
if (target_ != NullType::singleton() &&
detail::atomic_refcount_decrement(target_->refcount_) == 0) {
// See comment above about weakcount. As long as refcount>0,
// weakcount is one larger than the actual number of weak references.
// So we need to decrement it here.
bool should_delete =
target_->weakcount_.load(std::memory_order_acquire) == 1;
if (!should_delete) {
// justification for const_cast: release_resources is basically a
// destructor and a destructor always mutates the object, even for const
// objects. NOLINTNEXTLINE(cppcoreguidelines-pro-type-const-cast)
const_cast<std::remove_const_t<TTarget>*>(target_)->release_resources();
should_delete =
detail::atomic_weakcount_decrement(target_->weakcount_) == 0;
}
if (should_delete) {
delete target_;
}
}
}
When decrement refcount_ from 1 to 0, why not release_resources() directly but additionally determine weakcount != 1? Should weakcount_ controls the object itself, and refcount_controls the resources occupied by the object？