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  1. #include <iostream>
  2. #include <ostream>
  3.  
  4. using namespace std;
  5.  
  6. struct Example
  7. {
  8.     virtual void virtualfunction()=0;
  9.     virtual ~Example() {}
  10. };
  11.  
  12. struct Implmenetation : Example
  13. {
  14.     bool alive;
  15.     Implmenetation() : alive(true) {}
  16.     void virtualfunction()
  17.     {
  18.         cout << "Implmenetation::virtualfunction alive=" << alive << endl;
  19.     }
  20.     ~Implmenetation()
  21.     {
  22.         alive=false;
  23.         cout << "Implmenetation::~Implmenetation" << endl;
  24.     }
  25. };
  26.  
  27. struct Forwarder : Example
  28. {
  29.     Example *impl;
  30.     Forwarder(Example *i) : impl(i) {}
  31.     void virtualfunction()
  32.     {
  33.         impl->virtualfunction();
  34.     }
  35. };
  36.  
  37. void codeIDontControl(Example *ex)
  38. {
  39.      ex->virtualfunction();
  40.      delete ex;
  41. }
  42.  
  43. void myCode()
  44. {
  45.     Implmenetation impl;
  46.  
  47.     codeIDontControl(new Forwarder(&impl));
  48.     //do something with ex //doesn't work because ex has been freed
  49.     impl.virtualfunction();
  50. }
  51. int main()
  52. {
  53.     myCode();
  54. }
  55.  
Success #stdin #stdout 0.02s 2816KB
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Standard input is empty
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Implmenetation::virtualfunction alive=1
Implmenetation::virtualfunction alive=1
Implmenetation::~Implmenetation
https://ideone.com/Ac3cS5
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
secret

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