C++ smart pointer library

An implementation of smart pointers for C++. Features regular STL pointers as well as a custom IntrusivePtr

UniquePtr

• Provides unique ownership semantics
• Non-copyable
• Accepts a generic Deleter to support custom deallocation logic
• The implementation employs empty base optimization to avoid storing empty Deleter instances without any state. This is achieved with a custom CompressedPair.
• Exactly pointer-sized when used with an empty deleter (including the default one)
• Supports ownership transfer via move semantics
• Template specialization for arrays that correctly handles construction/destruction
• Follows the std::unique_ptr API

SharedPtr

• Provides shared ownership semantics
• Allocates a control block separately by default
• An optimized MakeShared implementation is provided. Stores the object and its reference count in a single contiguous allocation.
• Always pointer-sized
• Follows the std::shared_ptr API

WeakPtr

• Weak reference to a SharedPtr-managed object
• Holds shared ownership of the control block
• Always pointer-sized
• Follows the std::weak_ptr API

SharedFromThis

• Allows a class to construct SharedPtr from this via CRTP
• Avoids double-freeing this
• Correctly handles creation of a new shared pointer and retrieval of existing one

IntrusivePtr

• Lightweight alternative to SharedPtr for objects with internal refcount logic
• Requires the type to implement a specific interface
• Supports complex object lifetimes
• A convenient CRTP refcount mixin is provided