stddefaultdeletetT

std::default_delete<T> is a class template in the C++ standard library that provides the default deletion strategy for pointer-managed objects. It is defined in the <memory> header and is used by smart pointers to destroy the managed object when ownership ends.

The primary template defines operator()(T* ptr) to call delete ptr; a specialization exists for array types, operator()(T* ptr) calls delete[] ptr. This arrangement ensures that unique_ptr<T> uses delete for single objects, while unique_ptr<T[]> uses delete[] for arrays. The deleter is typically stateless and inexpensive to copy, making it an efficient, reusable mechanism in generic code.

In practice, std::default_delete<T> serves as the default deleter for smart pointers such as std::unique_ptr and, indirectly, influences std::shared_ptr behavior. It can be replaced by a custom deleter by supplying a different deleter type to the smart pointer’s template parameters or constructor, enabling custom destruction logic without altering ownership semantics.

Key properties include its compatibility with non-owning scenarios where a deleter object may be passed around, and its role as a common, standards-compliant default in template-based memory management. The specialization for arrays ensures correct behavior for both scalar and array types when managing dynamic memory.

Common use cases involve managing dynamically allocated objects with std::unique_ptr<T> p(new T); default deletion is used automatically unless a custom deleter is provided. Understanding std::default_delete<T> helps in designing generic, exception-safe resource management strategies in modern C++.