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  1. #include <iostream>
  2.  
  3. template <typename T>
  4. class shared_ptr {
  5.   T *ptr;
  6.   int *cnt;
  7. public:
  8.   shared_ptr(T *ptr) : ptr(ptr), cnt(new int(1)) {}
  9.   shared_ptr(shared_ptr const& o) : ptr(o.ptr), cnt(o.cnt) { ++*cnt; }
  10.   ~shared_ptr() { if (!--*cnt) { delete ptr; delete cnt; } }
  11.  
  12.   friend inline void swap(shared_ptr& lhs, shared_ptr& rhs)
  13.   { std::swap(lhs.ptr, rhs.ptr); std::swap(lhs.cnt, rhs.cnt); }
  14.   shared_ptr& operator=(shared_ptr rhs) { swap(*this, rhs); return *this; }
  15. };
  16.  
  17. struct test {
  18.   const char *c;
  19.   test(const char *c):c(c){ std::cout << "construct " << c << '\n'; }
  20.   ~test(){ std::cout << "destruct " << c << '\n'; }
  21. };
  22.  
  23. int main()
  24. {
  25.   shared_ptr<test> t(new test("A"));
  26.   {
  27.     shared_ptr<test> v(new test("B"));
  28.     {
  29.       shared_ptr<test> s(new test("C"));
  30.       shared_ptr<test> u(new test("D"));
  31.       t = s;
  32.     }
  33.   }
  34. }
  35.  
Success #stdin #stdout 0.01s 2816KB
comments (?)
stdin
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Standard input is empty
stdout
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construct A
construct B
construct C
construct D
destruct A
destruct D
destruct B
destruct C
https://ideone.com/chRAGN
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
public

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