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  1. #include <iostream>
  2. #include <vector>
  3.  
  4. struct Value
  5. {
  6.     int x;
  7. };
  8.  
  9. struct Delta
  10. {       
  11.     int dx;
  12. };
  13.  
  14. void apply(std::vector<Value> & values, const Delta & delta)
  15. {
  16.     for (unsigned i = 0; i < values.size(); i++)
  17.     {
  18.         values[i].x += delta.dx;
  19.     }
  20. }
  21.  
  22. int main()
  23. {
  24.     std::vector<Value> values(2);
  25.  
  26.     Delta & d = reinterpret_cast<Delta&>(values[0]);
  27.     d.dx = 1;
  28.  
  29.     apply(values, d);
  30.  
  31.     std::cout << values[1].x << std::endl;
  32. }
  33.  
  34. // My results with GCC 4.6.3
  35. #if 0
  36.     $ g++ -o test -O0 main.cpp && ./test
  37.     2
  38.  
  39.     $ g++ -o test -O1 main.cpp && ./test
  40.     2
  41.  
  42.     $ g++ -o test -O2 main.cpp && ./test
  43.     1
  44.  
  45.     $ g++ -o test -O3 main.cpp && ./test
  46.     1
  47. #endif
Success #stdin #stdout 0.01s 2812KB
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https://ideone.com/tnUV1
language:
C++ (gcc 8.3)
created:
13 years ago
visibility:
public

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