For std::unique_ptr pImpl pointers, declare special member functions in the class header, but implement them in the implementation file.

Compared to new, make functions eliminate source code duplication, improve exception safety, and, for std::make_shard and std::allocate_shared, generate code that’s smaller and faster.

Potential use cases for std::weak_ptr include caching, observer lists, and the prevention of std::shared_ptr cycles.

std::shared_ptrs offer convenience approaching that of garbage collection for the shared lifetime management of arbitrary resources.

std::unique_ptr is a small, fast, move-only smart pointer for managing resources with exclusive-ownership semantics.