19 General utilities library [utilities]

19.11 Smart pointers [smartptr]

19.11.1 Class template unique_­ptr [unique.ptr]

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

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;
  };
}
A specialization for array types is provided with a slightly altered interface.
  • 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.
  • Pointers to types derived from T are rejected by the constructors, and by reset.
  • The observers operator* and operator-> are not provided.
  • The indexing observer operator[] is provided.
  • 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.

19.11.1.3.1 Constructors [unique.ptr.runtime.ctor]

template<class U> 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 except that it additionally shall not participate in overload resolution unless
  • U is the same type as pointer, or
  • pointer is the same type as element_­type*, U is a pointer type V*, and V(*)[] is convertible to element_­type(*)[].
template<class U> unique_ptr(U p, see below d) noexcept; template<class U> 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 except that they shall not participate in overload resolution unless either
  • U is the same type as pointer,
  • U is nullptr_­t, or
  • 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> unique_ptr(unique_ptr<U, E>&& u) noexcept;
This constructor behaves the same as in the primary template, except that it shall not participate in overload resolution unless all of the following conditions hold, where UP is unique_­ptr<U, E>:
  • U is an array type, and
  • pointer is the same type as element_­type*, and
  • UP​::​pointer is the same type as UP​::​element_­type*, and
  • UP​::​element_­type(*)[] is convertible to element_­type(*)[], and
  • 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
:
This replaces the overload-resolution specification of the primary template
end note
]

19.11.1.3.2 Assignment [unique.ptr.runtime.asgn]

template<class U, class E> unique_ptr& operator=(unique_ptr<U, E>&& u)noexcept;
This operator behaves the same as in the primary template, except that it shall not participate in overload resolution unless all of the following conditions hold, where UP is unique_­ptr<U, E>:
  • U is an array type, and
  • pointer is the same type as element_­type*, and
  • UP​::​pointer is the same type as UP​::​element_­type*, and
  • UP​::​element_­type(*)[] is convertible to element_­type(*)[], and
  • is_­assignable_­v<D&, E&&> is true.
[Note
:
This replaces the overload-resolution specification of the primary template
end note
]

19.11.1.3.3 Observers [unique.ptr.runtime.observers]

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

19.11.1.3.4 Modifiers [unique.ptr.runtime.modifiers]

void reset(nullptr_t p = nullptr) noexcept;
Effects: Equivalent to reset(pointer()).
template<class U> void reset(U p) noexcept;
This function behaves the same as the reset member of the primary template, except that it shall not participate in overload resolution unless either
  • U is the same type as pointer, or
  • pointer is the same type as element_­type*, U is a pointer type V*, and V(*)[] is convertible to element_­type(*)[].