Is there a way to observe destructor of std::shared

I would like to know if the count of references in shared_ptr becomes 1. In other words, I want to observe shared_ptr. It reminds me Observer pattern. The whole picture is that there are several threads in the application requesting a logger instance. When each thread has done its job it deallocates its instance of shared_ptr. Therefore, once all threads have completed, there is left a single instance of object and just one reference to the object - shared_ptr. And the question is how to get rid of it. Evident solution is been rendered here: garbage collector running every 5 minutes...

CodePudding user response：

Therefore, once all theads have completed, there is left a single instance of object and just one reference to the object - shared_ptr. And the question is how to get rid of it.

Simply don't create the extra shared pointer to the object in the first place.

CodePudding user response：

You can use std::shared_ptr::use_count or std::shared_ptr::unique in C 20:

#include <iostream>
#include <memory>

int main( )
{
    auto sptr { std::make_shared<double>( 10.0 ) };

    std::cout << "use count == " << sptr.use_count( )
              << " --- is unique? " << std::boolalpha << sptr.unique( ) << std::noboolalpha << '\n';

    auto sptr2 { sptr };
    std::cout << "use count == " << sptr2.use_count( )
              << " --- is unique? " << std::boolalpha << sptr2.unique( ) << '\n';
}

Sample output:

use count == 1 --- is unique? true
use count == 2 --- is unique? false