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  1. #include <iostream>
  2. #include <string>
  3. #include <memory>
  4.  
  5. using namespace std;
  6.  
  7. struct A
  8. {
  9.     int x;
  10.     std::string y;
  11.     A(int x, std::string y) : x(x), y(y) {}
  12.     A(A&& a) : x(std::move(a.x)), y(std::move(a.y)) {}
  13.  
  14.     virtual const char* who() const { return "A"; }
  15.     void show() const { std::cout << (void const*)this << " " << who() << " " << x << " [" << y << "]" << std::endl; }
  16. };
  17.  
  18. struct B : A
  19. {
  20.     virtual const char* who() const { return "B"; }
  21.     B(A&& a) : A(std::move(a)) {}
  22. };
  23.  
  24. template<class TO_T> 
  25.   inline TO_T* turn_A_to(A* a) {
  26.   	A temp(std::move(*a));
  27.   	a->~A();
  28.   	return new(a) B(std::move(temp));
  29.   }
  30.  
  31.  
  32. int main()
  33. {
  34.     A* pa = new A(123, "text");
  35.     pa->show(); // 0xbfbefa58 A 123 [text]
  36.     turn_A_to<B>(pa);
  37.     pa->show(); // 0xbfbefa58 B 123 [text]
  38.  
  39. }
Success #stdin #stdout 0s 3476KB
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stdin
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Standard input is empty
stdout
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0x8c48020 A 123 [text]
0x8c48020 B 123 [text]
https://ideone.com/5O6SFV
language:
C++14 (gcc 8.3)
created:
10 years ago
visibility:
public

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