20 General utilities library [utilities]

20.11 Smart pointers [smartptr]

20.11.1 Class template unique_­ptr [unique.ptr]

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

20.11.1.4.1 General [unique.ptr.runtime.general]

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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> explicit unique_ptr(U p) noexcept; template<class U> unique_ptr(U p, see below d) noexcept; template<class U> unique_ptr(U p, see below d) noexcept; unique_ptr(unique_ptr&& u) noexcept; template<class U, class E> unique_ptr(unique_ptr<U, E>&& u) noexcept; constexpr unique_ptr(nullptr_t) noexcept; // destructor ~unique_ptr(); // assignment unique_ptr& operator=(unique_ptr&& u) noexcept; template<class U, class E> unique_ptr& operator=(unique_ptr<U, E>&& u) noexcept; unique_ptr& operator=(nullptr_t) noexcept; // [unique.ptr.runtime.observers], observers T& operator[](size_t i) const; pointer get() const noexcept; deleter_type& get_deleter() noexcept; const deleter_type& get_deleter() const noexcept; explicit operator bool() const noexcept; // [unique.ptr.runtime.modifiers], modifiers pointer release() noexcept; template<class U> void reset(U p) noexcept; void reset(nullptr_t = nullptr) noexcept; void swap(unique_ptr& u) noexcept; // disable copy from lvalue unique_ptr(const unique_ptr&) = delete; unique_ptr& operator=(const unique_ptr&) = delete; }; }
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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[].
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Descriptions are provided below only for members that differ from the primary template.
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The template argument T shall be a complete type.

20.11.1.4.2 Constructors [unique.ptr.runtime.ctor]

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template<class U> explicit unique_ptr(U p) noexcept;
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This constructor behaves the same as the constructor in the primary template that takes a single parameter of type pointer.
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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> unique_ptr(U p, see below d) noexcept; template<class U> unique_ptr(U p, see below d) noexcept;
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These constructors behave the same as the constructors in the primary template that take a parameter of type pointer and a second parameter.
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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(*)[].
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template<class U, class E> unique_ptr(unique_ptr<U, E>&& u) noexcept;
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This constructor behaves the same as in the primary template.
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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]

20.11.1.4.3 Assignment [unique.ptr.runtime.asgn]

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template<class U, class E> unique_ptr& operator=(unique_ptr<U, E>&& u) noexcept;
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This operator behaves the same as in the primary template.
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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]

20.11.1.4.4 Observers [unique.ptr.runtime.observers]

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T& operator[](size_t i) const;
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Preconditions: the number of elements in the array to which the stored pointer points.
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Returns: get()[i].

20.11.1.4.5 Modifiers [unique.ptr.runtime.modifiers]

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void reset(nullptr_t p = nullptr) noexcept;
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Effects: Equivalent to reset(pointer()).
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template<class U> void reset(U p) noexcept;
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This function behaves the same as the reset member of the primary template.
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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(*)[].