std::shared_ptr<T>::unique

Declarations

Deprecated in C++17, Removed in C++20

bool unique() const noexcept;

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.

Notes

This function was deprecated in C++17 and removed in C++20 because use_count is only an approximation in multithreaded environment (see Notes in use_count).

Example

#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'; 
}

Possible Result

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