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  1. #include <iostream>
  2. #include <deque>
  3. #include <algorithm>
  4. #include <utility>
  5. #include <memory>
  6. using namespace std;
  7.  
  8. deque<bool> pool;
  9.  
  10. class ExpressionTemp;
  11. class Scalar
  12. {
  13.     bool *alive;
  14.  
  15.     friend class ExpressionTemp;
  16.  
  17.     Scalar(const Scalar&);
  18.     Scalar &operator=(const Scalar&);
  19.     Scalar &operator=(Scalar&&);
  20. public:
  21.     Scalar()
  22.     {
  23.         pool.push_back(true);
  24.         alive=&pool.back();
  25.     }
  26.     Scalar(Scalar &&rhs)
  27.         : alive(0)
  28.     {
  29.         swap(alive,rhs.alive);
  30.     }
  31.     ~Scalar()
  32.     {
  33.         if(alive)
  34.             (*alive)=false;
  35.     }
  36. };
  37. class ExpressionTemp
  38. {
  39.     bool *operand_alive;
  40. public:
  41.     ExpressionTemp(const Scalar &s)
  42.         : operand_alive(s.alive)
  43.     {
  44.     }
  45.     void do_job()
  46.     {
  47.       if(*operand_alive)
  48.           cout << "captured operand is alive" << endl;
  49.       else
  50.           cout << "captured operand is DEAD!" << endl;
  51.     }
  52. };
  53.  
  54. ExpressionTemp expression(const Scalar &s)
  55. {
  56.     return {s};
  57. }
  58. int main()
  59. {
  60.     {
  61.         expression(Scalar()).do_job(); // OK
  62.     }
  63.     {
  64.         Scalar lv;
  65.         auto &&rvref=expression(lv);
  66.         rvref.do_job(); // OK, lv is still alive
  67.     }
  68.     {
  69.         auto &&rvref=expression(Scalar());
  70.         rvref.do_job(); // referencing to dead temporary
  71.     }
  72.     return 0;
  73. }
  74.  
Success #stdin #stdout 0s 3020KB
comments (?)
stdin 
Standard input is empty
stdout 
captured operand is alive
captured operand is alive
captured operand is DEAD!
https://ideone.com/soA7Kh
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
secret

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