20 General utilities library [utilities]

20.7 Smart pointers [smartptr]

20.7.1 Class template unique_ptr [unique.ptr]

20.7.1.3 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:
    typedef see below pointer;
    typedef T element_type;
    typedef D deleter_type;

    // [unique.ptr.runtime.ctor], constructors
    constexpr unique_ptr() noexcept;
    explicit unique_ptr(pointer p) noexcept;
    unique_ptr(pointer p, see below d) noexcept;
    unique_ptr(pointer p, see below d) noexcept;
    unique_ptr(unique_ptr&& u) noexcept;
    constexpr unique_ptr(nullptr_t) noexcept : unique_ptr() { }

    // destructor
    ~unique_ptr();

    // assignment
    unique_ptr& operator=(unique_ptr&& 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;
    void reset(pointer p = pointer()) noexcept;
    void reset(nullptr_t) noexcept;
    template <class U> void reset(U) = delete;
    void swap(unique_ptr& u) noexcept;

    // disable copy from lvalue
    unique_ptr(const unique_ptr&) = delete;
    unique_ptr& operator=(const unique_ptr&) = delete;
  };
}
1

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

  • (1.1)

    Conversions between different types of unique_ptr<T[], D> or 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[].

2

Descriptions are provided below only for member functions that have behavior different from the primary template.

3

The template argument T shall be a complete type.

20.7.1.3.1 unique_ptr constructors [unique.ptr.runtime.ctor]

explicit unique_ptr(pointer p) noexcept; unique_ptr(pointer p, see below d) noexcept; unique_ptr(pointer p, see below d) noexcept;

These constructors behave the same as in the primary template except that they do not accept pointer types which are convertible to pointer. [ Note: One implementation technique is to create private templated overloads of these members.  — end note ]

20.7.1.3.2 unique_ptr observers [unique.ptr.runtime.observers]

T& operator[](size_t i) const;

1

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

2

Returns: get()[i].

20.7.1.3.3 unique_ptr modifiers [unique.ptr.runtime.modifiers]

void reset(pointer p = pointer()) noexcept; void reset(nullptr_t p) noexcept;

1

Effects: If get() == nullptr there are no effects. Otherwise get_deleter()(get()).

2

Postcondition: get() == p.