20 Memory management library [mem]

20.3 Smart pointers [smartptr]

20.3.1 Unique-ownership pointers [unique.ptr] unique_ptr for single objects [unique.ptr.single] General [unique.ptr.single.general]

namespace std { template<class T, class D = default_delete<T>> class unique_ptr { public: using pointer = see below; using element_type = T; using deleter_type = D; // [unique.ptr.single.ctor], constructors constexpr unique_ptr() noexcept; constexpr explicit unique_ptr(type_identity_t<pointer> p) noexcept; constexpr unique_ptr(type_identity_t<pointer> p, see below d1) noexcept; constexpr unique_ptr(type_identity_t<pointer> p, see below d2) noexcept; constexpr unique_ptr(unique_ptr&& u) noexcept; constexpr unique_ptr(nullptr_t) noexcept; template<class U, class E> constexpr unique_ptr(unique_ptr<U, E>&& u) noexcept; // [unique.ptr.single.dtor], destructor constexpr ~unique_ptr(); // [unique.ptr.single.asgn], assignment constexpr unique_ptr& operator=(unique_ptr&& u) noexcept; template<class U, class E> constexpr unique_ptr& operator=(unique_ptr<U, E>&& u) noexcept; constexpr unique_ptr& operator=(nullptr_t) noexcept; // [unique.ptr.single.observers], observers constexpr add_lvalue_reference_t<T> operator*() const noexcept(see below); constexpr pointer operator->() const noexcept; constexpr pointer get() const noexcept; constexpr deleter_type& get_deleter() noexcept; constexpr const deleter_type& get_deleter() const noexcept; constexpr explicit operator bool() const noexcept; // [unique.ptr.single.modifiers], modifiers constexpr pointer release() noexcept; constexpr void reset(pointer p = pointer()) noexcept; constexpr void swap(unique_ptr& u) noexcept; // disable copy from lvalue unique_ptr(const unique_ptr&) = delete; unique_ptr& operator=(const unique_ptr&) = delete; }; }
The default type for the template parameter D is default_delete.
A client-supplied template argument D shall be a function object type ([function.objects]), lvalue reference to function, or lvalue reference to function object type for which, given a value d of type D and a value ptr of type unique_ptr<T, D>​::​pointer, the expression d(ptr) is valid and has the effect of disposing of the pointer as appropriate for that deleter.
If the deleter's type D is not a reference type, D shall meet the Cpp17Destructible requirements (Table 35).
If the qualified-id remove_reference_t<D>​::​pointer is valid and denotes a type ([temp.deduct]), then unique_ptr<T, D>​::​pointer shall be a synonym for remove_reference_t<D>​::​pointer.
Otherwise unique_ptr<T, D>​::​pointer shall be a synonym for element_type*.
The type unique_ptr<T, D>​::​pointer shall meet the Cpp17NullablePointer requirements (Table 36).
[Example 1: 
Given an allocator type X ([allocator.requirements.general]) and letting A be a synonym for allocator_traits<X>, the types A​::​pointer, A​::​const_pointer, A​::​void_pointer, and A​::​const_void_pointer may be used as unique_ptr<T, D>​::​pointer.
— end example]