std::shared_ptr::unique

bool unique() const noexcept;		(deprecated)

Checks if *this is the only shared_ptr instance managing the current object, i.e. whether use_count() == 1.

Parameters

(none)

Return value

true if *this is the only shared_ptr instance managing the current object, false otherwise.

Exceptions

noexcept specification:

noexcept

Notes

This function is deprecated as of C++17 because use_count is only an approximation in multithreaded environment.

Example

Run this code

#include <memory> 
#include <iostream> 
 
int main() 
{ 
    auto sp1 = std::make_shared<int>(5);
    std::cout << std::boolalpha;
    std::cout << "sp1.unique() == " << sp1.unique() << '\n'; 
 
    std::shared_ptr<int> sp2 = sp1; 
    std::cout << "sp1.unique() == " << sp1.unique() << '\n'; 
}

Output:

sp1.unique() == true
sp1.unique() == false

Language
Standard library headers
Concepts
Utilities library
Strings library
Containers library
Algorithms library
Iterators library
Numerics library
Input/output library
Localizations library
Regular expressions library (C++11)
Atomic operations library (C++11)
Thread support library (C++11)
Filesystem library (C++17)
Technical Specifications

Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Date and time
Function objects
initializer_list (C++11)
bitset
hash (C++11)
Relational operators
rel_ops::operator!=rel_ops::operator>rel_ops::operator<=rel_ops::operator>=
`optional`, `any` and `variant` (C++17)
optional
any
variant
in_placein_place_typein_place_indexin_place_tin_place_type_tin_place_index_t
Pairs and tuples
pair
tuple (C++11)
apply (C++17)
make_from_tuple (C++17)
piecewise_construct_t (C++11)
piecewise_construct (C++11)
integer_sequence (C++14)
Swap, forward and move
swap
exchange (C++14)
forward (C++11)
move (C++11)
move_if_noexcept (C++11)
Elementary string conversions
to_chars (C++17)
from_chars (C++17)
chars_format (C++17)
Type operations
declval (C++11)
as_const (C++17)

Member functions
shared_ptr::shared_ptr
shared_ptr::~shared_ptr
shared_ptr::operator=
Modifiers
shared_ptr::reset
shared_ptr::swap
Observers
shared_ptr::get
shared_ptr::operator*shared_ptr::operator->
shared_ptr::operator[] (C++17)
shared_ptr::use_count
shared_ptr::unique (deprecated)
shared_ptr::operator bool
shared_ptr::owner_before
Non-member functions
std::swap
make_shared
allocate_shared
static_pointer_castdynamic_pointer_castconst_pointer_castreinterpret_pointer_cast (C++17)
get_deleter
operator==operator\|=operator<operator<=operator>operator>=
operator<<
atomic_is_lock_freeatomic_loadatomic_load_explicitatomic_storeatomic_store_explicitatomic_exchangeatomic_exchange_explicitatomic_compare_exchange_weakatomic_compare_exchange_strongatomic_compare_exchange_weak_explicitatomic_compare_exchange_strong_explicit
std::hash