std::default_delete - Man Page

constexpr default_delete () noexcept=default
Default constructor.
template<typename _Up , typename  = _Require<is_convertible<_Up*, _Tp*>>> constexpr default_delete (const default_delete< _Up > &) noexcept
Converting constructor.
constexpr void operator() (_Tp *__ptr) const
Calls delete __ptr

struct std::default_delete< _Tp >"Primary template of default_delete, used by unique_ptr for single objects

Since

C++11

Default constructor.

Converting constructor. Allows conversion from a deleter for objects of another type, _Up, only if _Up* is convertible to _Tp*.

Calls delete __ptr