23 General utilities library [utilities]

23.11 Smart pointers [smartptr]

23.11.2 Shared-ownership pointers [util.smartptr]

23.11.2.2 Class template shared_­ptr [util.smartptr.shared]

23.11.2.2.5 shared_­ptr observers [util.smartptr.shared.obs]

element_type* get() const noexcept;
Returns: The stored pointer.
T& operator*() const noexcept;
Requires: get() != 0.
Returns: *get().
Remarks: When T is an array type or cv void, it is unspecified whether this member function is declared.
If it is declared, it is unspecified what its return type is, except that the declaration (although not necessarily the definition) of the function shall be well-formed.
T* operator->() const noexcept;
Requires: get() != 0.
Returns: get().
Remarks: When T is an array type, it is unspecified whether this member function is declared.
If it is declared, it is unspecified what its return type is, except that the declaration (although not necessarily the definition) of the function shall be well-formed.
element_type& operator[](ptrdiff_t i) const;
Requires: get() != 0 && i >= 0.
If T is U[N], i < N.
Returns: get()[i].
Remarks: When T is not an array type, it is unspecified whether this member function is declared.
If it is declared, it is unspecified what its return type is, except that the declaration (although not necessarily the definition) of the function shall be well-formed.
Throws: Nothing.
long use_count() const noexcept;
Returns: The number of shared_­ptr objects, *this included, that share ownership with *this, or 0 when *this is empty.
Synchronization: None.
[Note
:
get() == nullptr does not imply a specific return value of use_­count().
end note
]
[Note
:
weak_­ptr<T>​::​lock() can affect the return value of use_­count().
end note
]
[Note
:
When multiple threads can affect the return value of use_­count(), the result should be treated as approximate.
In particular, use_­count() == 1 does not imply that accesses through a previously destroyed shared_­ptr have in any sense completed.
end note
]
explicit operator bool() const noexcept;
Returns: get() != 0.
template <class U> bool owner_before(const shared_ptr<U>& b) const noexcept; template <class U> bool owner_before(const weak_ptr<U>& b) const noexcept;
Returns: An unspecified value such that
  • x.owner_­before(y) defines a strict weak ordering as defined in [alg.sorting];
  • under the equivalence relation defined by owner_­before, !a.owner_­before(b) && !b.owner_­before(a), two shared_­ptr or weak_­ptr instances are equivalent if and only if they share ownership or are both empty.