20 Memory management library [mem]

20.3 Smart pointers [smartptr]

20.3.1 Unique-ownership pointers [unique.ptr]

20.3.1.4 unique_ptr for array objects with a runtime length [unique.ptr.runtime]

20.3.1.4.1 General [unique.ptr.runtime.general]

namespace std { template<class T, class D> class unique_ptr<T[], D> { public: using pointer = see below; using element_type = T; using deleter_type = D; // [unique.ptr.runtime.ctor], constructors constexpr unique_ptr() noexcept; template<class U> constexpr explicit unique_ptr(U p) noexcept; template<class U> constexpr unique_ptr(U p, see below d) noexcept; template<class U> constexpr unique_ptr(U p, see below d) noexcept; constexpr unique_ptr(unique_ptr&& u) noexcept; template<class U, class E> constexpr unique_ptr(unique_ptr<U, E>&& u) noexcept; constexpr unique_ptr(nullptr_t) noexcept; // destructor constexpr ~unique_ptr(); // 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.runtime.observers], observers constexpr T& operator[](size_t i) const; 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.runtime.modifiers], modifiers constexpr pointer release() noexcept; template<class U> constexpr void reset(U p) noexcept; constexpr void reset(nullptr_t = nullptr) 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; }; }

A specialization for array types is provided with a slightly altered interface.

(1.1)
Conversions between different types of unique_ptr<T[], D> that would be disallowed for the corresponding pointer-to-array types, and conversions to or from the non-array forms of unique_ptr, produce an ill-formed program.
(1.2)
Pointers to types derived from T are rejected by the constructors, and by reset.
(1.3)
The observers operator* and operator-> are not provided.
(1.4)
The indexing observer operator[] is provided.
(1.5)
The default deleter will call delete[].

Descriptions are provided below only for members that differ from the primary template.

The template argument T shall be a complete type.

20.3.1.4.2 Constructors [unique.ptr.runtime.ctor]

🔗

template<class U> constexpr explicit unique_ptr(U p) noexcept;

This constructor behaves the same as the constructor in the primary template that takes a single parameter of type pointer.

Constraints:

(2.1)
U is the same type as pointer, or
(2.2)
pointer is the same type as element_type*, U is a pointer type V*, and V(*)[] is convertible to element_type(*)[].

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template<class U> constexpr unique_ptr(U p, see below d) noexcept;
template<class U> constexpr unique_ptr(U p, see below d) noexcept;

These constructors behave the same as the constructors in the primary template that take a parameter of type pointer and a second parameter.

Constraints:

(4.1)
U is the same type as pointer,
(4.2)
U is nullptr_t, or
(4.3)
pointer is the same type as element_type*, U is a pointer type V*, and V(*)[] is convertible to element_type(*)[].

🔗

template<class U, class E> constexpr unique_ptr(unique_ptr<U, E>&& u) noexcept;

This constructor behaves the same as in the primary template.

Constraints: Where UP is unique_ptr<U, E>:

(6.1)
U is an array type, and
(6.2)
pointer is the same type as element_type*, and
(6.3)
UP::pointer is the same type as UP::element_type*, and
(6.4)
UP::element_type(*)[] is convertible to element_type(*)[], and
(6.5)
either D is a reference type and E is the same type as D, or D is not a reference type and E is implicitly convertible to D.

[Note 1:

This replaces the Constraints: specification of the primary template.

— end note]

20.3.1.4.3 Assignment [unique.ptr.runtime.asgn]

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template<class U, class E> constexpr unique_ptr& operator=(unique_ptr<U, E>&& u) noexcept;

This operator behaves the same as in the primary template.

Constraints: Where UP is unique_ptr<U, E>:

(2.1)
U is an array type, and
(2.2)
pointer is the same type as element_type*, and
(2.3)
UP::pointer is the same type as UP::element_type*, and
(2.4)
UP::element_type(*)[] is convertible to element_type(*)[], and
(2.5)
is_assignable_v<D&, E&&> is true.

[Note 1:

This replaces the Constraints: specification of the primary template.

— end note]

20.3.1.4.4 Observers [unique.ptr.runtime.observers]

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constexpr T& operator[](size_t i) const;

Preconditions: i < the number of elements in the array to which the stored pointer points.

Returns: get()[i].

20.3.1.4.5 Modifiers [unique.ptr.runtime.modifiers]

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constexpr void reset(nullptr_t p = nullptr) noexcept;

Effects: Equivalent to reset(pointer()).

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template<class U> constexpr void reset(U p) noexcept;

This function behaves the same as the reset member of the primary template.

Constraints:

(3.1)
U is the same type as pointer, or
(3.2)
pointer is the same type as element_type*, U is a pointer type V*, and V(*)[] is convertible to element_type(*)[].