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  1. #include <iostream>
  2. #include <memory>
  3.  
  4. using namespace std;
  5.  
  6. struct MyClass
  7. {
  8.   shared_ptr<MyClass> next;
  9.  
  10.   MyClass(shared_ptr<MyClass> next)
  11.   {
  12.     this->next = next;
  13.     cout << "Constructor completed for a MyClass object." << endl;
  14.   }
  15.  
  16.   virtual ~MyClass()
  17.   {
  18.     cout << "Destructor completed for a MyClass object." << endl;
  19.   }
  20. };
  21.  
  22. int main() 
  23. {
  24.   shared_ptr<MyClass> nullp;
  25.   shared_ptr<MyClass> sp1(new MyClass(nullp));
  26.   shared_ptr<MyClass> sp2(new MyClass(sp1));
  27.  
  28.   {
  29.     cout << "Entered inner block." << endl;
  30.     shared_ptr<MyClass> sp3(new MyClass(sp2));
  31.     sp1->next = sp3;	// Create cyclic referencing
  32.     cout << "sp3 use count: " << sp3.use_count() << endl;
  33.     cout << "Leaving inner block." << endl;
  34.   }
  35.   cout << "Left inner block." << endl;
  36.  
  37.   cout << "sp1 use count: " << sp1.use_count() << endl;
  38.   cout << "sp2 use count: " << sp2.use_count() << endl;
  39.   cout << "sp3 use count: " << sp1->next.use_count() << endl;
  40.  
  41.   sp1.reset();
  42.   sp2.reset();
  43.  
  44.   cout << "Released sp1 and sp2, dtors still not executed." << endl;
  45.  
  46.   return 0;
  47. }
Success #stdin #stdout 0s 3416KB
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stdin
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Standard input is empty
stdout
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Constructor completed for a MyClass object.
Constructor completed for a MyClass object.
Entered inner block.
Constructor completed for a MyClass object.
sp3 use count: 2
Leaving inner block.
Left inner block.
sp1 use count: 2
sp2 use count: 2
sp3 use count: 1
Released sp1 and sp2, dtors still not executed.
https://ideone.com/wfKa8Z
Advanced CPP: Memory usage
shared_ptr and cyclic reference
language:
C++14 (gcc 8.3)
created:
8 years ago
visibility:
secret

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