stddefaultdelete

Stddefaultdelete is not a standard library term; the standard name is std::default_delete. It is a function-object deleter provided by the C++ standard library for use with smart pointers, most notably std::unique_ptr. std::default_delete defines how memory is released when a pointer is no longer needed.

The primary form is a class template in the header <memory>. For a non-array type T, default_delete provides an operator() that takes a T* and calls delete on it. There is also a partial specialization for array types, default_delete<T[]> which calls delete[] on the pointer. These deleters are designed to be lightweight and default-constructible, so they are inexpensive to store inside smart pointers.

In practice, std::default_delete is the default deleter used by std::unique_ptr when no custom deleter is provided. This means a unique_ptr<T> will, by default, delete the managed object with delete, and a std::unique_ptr<T[]> will delete with delete[]. The deleter is part of the unique_ptr’s type, and it can be customized by supplying a different deleter type D via the unique_ptr<T, D> template parameters.

Custom deleters can be any callable object, including function pointers or stateful functors, allowing developers to customize memory management (for example, using a memory pool or specialized release routine). If a custom deleter is supplied, it is invoked instead of std::default_delete when the smart pointer releases ownership.

Historically, std::default_delete has been part of C++11 and remains a standard means of defining default destruction behavior for dynamic allocations. There is no separate entity named stddefaultdelete in the standard library.