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  1. #include <iostream>       // std::cout
  2. #include <vector>         // std::vector
  3. #include <thread>         // std::thread
  4. #include <mutex>          // std::mutex, std::unique_lock, std::defer_lock
  5. #include "stdio.h"
  6. class B;
  7.  
  8. template <typename T>
  9. class shared_ptr {
  10. public:
  11.     shared_ptr() : count(0),_ptr(nullptr) {}
  12.     shared_ptr(T* p) : count(new int(1)), _ptr(p) {printf("new int %d,count = %d\n",*this,*count);}
  13.     shared_ptr(shared_ptr<T>& other) : count(&(++*other.count)), _ptr(other._ptr) {printf("copy run count=%d\n",*count);}
  14.     T* operator->() { return _ptr; }
  15.     T& operator*() { return *_ptr; }
  16.     shared_ptr<T>& operator=(shared_ptr<T>& other)
  17.     {
  18.  
  19.         ++*other.count;
  20.         if (this->_ptr && 0 == --*this->count)
  21.         {
  22.             delete count;
  23.             delete _ptr;
  24.         }
  25.         this->_ptr = other._ptr;
  26.         this->count = other.count;
  27.         printf("= run %d,count = %d\n",*this,*count);
  28.         return *this;
  29.     }
  30.     ~shared_ptr()
  31.     {
  32.  
  33.         if (--*count == 0)
  34.         {
  35.             //delete count;
  36.             //delete _ptr;
  37.         }    
  38.         printf("distory run %d,%d\n",*this,*count);
  39.     }
  40.  
  41.     int getRef() { return *count; }
  42. private:
  43.     int* count;
  44.     T* _ptr;
  45. };
  46.  
  47.  
  48.  
  49. class A
  50. {
  51. public:
  52.      A(){printf("A construct run\n");};
  53.      ~A(){printf("A disconstruct run\n");};
  54.      shared_ptr<B> m_b;
  55. };
  56. class B
  57. {
  58. public:
  59.      B(){printf("B construct run\n");};
  60.      ~B(){printf("B disconstruct run\n");};
  61.     shared_ptr<A> m_a;
  62. };
  63.  
  64. int main() 
  65. {
  66. //   A a;
  67. //   B b;
  68. shared_ptr<A> a(new A);  //new出来的A的引用计数此时为1
  69. shared_ptr<B> b(new B);  //new出来的B的引用计数此时为1
  70. a->m_b = b;              //B的引用计数增加为2
  71. b->m_a = a;              //A的引用计数增加为2
  72. }
Success #stdin #stdout 0s 4504KB
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stdin
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Standard input is empty
stdout
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A construct run
new int -1246472800,count = 1
B construct run
new int -1246472784,count = 1
= run 164244512,count = 2
= run 164248688,count = 2
distory run -1246472784,1
distory run -1246472800,1
https://ideone.com/tDwC0Y
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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