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  1. #include <iostream>
  2. #include <memory>
  3.  
  4. class Object
  5. {
  6. public:	
  7.    //...potentially lots of data...
  8. };
  9.  
  10. class ObjectHandle
  11. {
  12. public:	
  13.    ObjectHandle() { std::cout << "Constructed" << std::endl; }
  14.    ~ObjectHandle() { std::cout << "Destructed" << std::endl; }
  15.  
  16. private:
  17.     Object *ptrToPotentiallyLotsOfData = nullptr;
  18. };
  19.  
  20. int main()
  21. {
  22. 	std::cout << "ObjectHandle size: " << sizeof(ObjectHandle) << std::endl;
  23. 	std::cout << (std::is_pod<ObjectHandle>::value? "Is plain-ol`-data" : "Is not plain-old-data") << std::endl;
  24. 	std::cout << "\nOutter scope began" << std::endl;
  25. 	{
  26. 		std::weak_ptr<ObjectHandle> objectWPtr;
  27.  
  28. 		std::cout << "Inner scope began" << std::endl;
  29. 		{
  30. 			std::shared_ptr<ObjectHandle> objectSPtr = std::make_shared<ObjectHandle>();
  31. 			objectWPtr = objectSPtr;
  32. 		}
  33. 		std::cout << "Inner scope ended (shared_ptr goes out of scope)" << std::endl;
  34.  
  35. 	}
  36. 	std::cout << "Outter scope ended (weak_ptr goes out of scope)" << std::endl;
  37.  
  38. 	return 0;
  39. }
Success #stdin #stdout 0s 3476KB
comments (?)
stdin
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Standard input is empty
stdout
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ObjectHandle size: 4
Is not plain-old-data

Outter scope began
Inner scope began
Constructed
Destructed
Inner scope ended (shared_ptr goes out of scope)
Outter scope ended (weak_ptr goes out of scope)
https://ideone.com/zuFUJs
Testing how weak_ptr might not deallocate class memory for objects until after even all the weak_ptrs are destroyed, if the object is small enough to be allocated within the shared pointer control block that stores the reference counts.

This can be a problem if the 'small object' itself contains pointers to other objects or lots of memory.
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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