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  1. #include <iostream>
  2. #include <utility>
  3. #include <cstddef>
  4.  
  5. template <typename T>
  6. struct my_shared_ptr
  7. {
  8. 	my_shared_ptr() : rc(0) {}
  9.  
  10. 	template <typename... Args>
  11. 	my_shared_ptr(Args&&... args)
  12. 		: rc(new refcount_block(std::forward<Args>(args)...))
  13. 	{}
  14.  
  15. 	T& operator * ()
  16. 	{
  17. 		return *rc->ptr();
  18. 	}
  19.  
  20. 	T* operator -> ()
  21. 	{
  22. 		return rc->ptr();
  23. 	}
  24.  
  25. 	~my_shared_ptr()
  26. 	{
  27. 		if(!--rc->refs)
  28. 			delete rc;
  29. 	}
  30.  
  31. private:
  32. 	struct refcount_block
  33. 	{
  34. 		template <typename... Args>
  35. 		refcount_block(Args&&... args)
  36. 			: refs(1)
  37. 		{
  38. 			new (object) T(std::forward<Args>(args)...);
  39. 		}
  40.  
  41. 		~refcount_block()
  42. 		{
  43. 			ptr()->~T();
  44. 		}
  45.  
  46. 		T* ptr()
  47. 		{
  48. 			return reinterpret_cast<T*>(object);
  49. 		}
  50.  
  51. 		std::size_t refs;
  52. 		char object[sizeof(T)]; // alignas(T)
  53. 	};
  54.  
  55. 	refcount_block* rc;
  56. };
  57.  
  58. int main()
  59. {
  60. 	std::cout << sizeof(int*)                 << '\n'
  61. 	          << sizeof(my_shared_ptr<int>)   << '\n';
  62. }
Success #stdin #stdout 0s 2828KB
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https://ideone.com/aIlrW
language:
C++14 (gcc 8.3)
created:
13 years ago
visibility:
public

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