#include <iostream>
#include <memory>
 
using namespace std;
 
struct MyClass
{
  MyClass() { cout << "MyClass ctor runned." << endl; }
  ~MyClass() { cout << "MyClass dtor runned." << endl; }
};
 
int main() 
{
  shared_ptr<MyClass> sp1 = make_shared<MyClass>(); // since C++11
  cout << "Use count: " << sp1.use_count() << endl;
 
  weak_ptr<MyClass> wp = sp1;
  cout << "Use count: " << sp1.use_count() << endl; // Only shared_ptr counts, weak_ptr does not
  cout << "Use count: " << wp.use_count() << endl;
 
  {
    cout << "Entered inner block." << endl;
    shared_ptr<MyClass> sp2 = wp.lock();
    cout << "Use count: " << sp1.use_count() << endl;
 
    if(sp2)
      cout << "Lock acquired." << endl;
    cout << "Leaving inner block." << endl;
  }
  cout << "Left inner block." << endl;
  cout << "Use count: " << sp1.use_count() << endl;
 
  cout << "About to delete the last shared pointer." << endl;
  sp1.reset();
  cout << "Deleted the last shared pointer." << endl;
 
  shared_ptr<MyClass> sp3 = wp.lock();
  if(!sp3)
    cout << "Shared object does not exists anymore." << endl;
 
  if(wp.expired())	// Not thread safe solution.
    cout << "Shared object does not exists anymore." << endl;
 
  return 0;
} 

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