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  1. #include <memory>
  2. #include <new>
  3. #include <cstdlib>
  4. #include <iostream>
  5.  
  6. template<typename T>
  7. T*
  8. allocate()
  9. {
  10.     std::unique_ptr<T, void(*)(void*)> hold(static_cast<T*>(std::malloc(sizeof(T))),
  11.                                                             std::free);
  12.     ::new (hold.get()) T;
  13.     std::cout << hold.get() << std::endl;
  14.     return static_cast<T*>(hold.release());
  15. }
  16.  
  17. template<typename B,typename T>
  18. void
  19. deallocate(B* p)
  20. {
  21. 	std::cout << p << std::endl;
  22.     T* d = static_cast<T*>(p);
  23.     d->~T();
  24.     std::cout << d << std::endl;
  25.     std::free(d);
  26. }
  27.  
  28. struct Base
  29. {
  30. 	int i;
  31.     Base() {std::cout << "Base()\n";}
  32.     Base(const Base&) = delete;
  33.     Base& operator=(const Base&) = delete;
  34.     ~Base() {std::cout << "~Base()\n";}
  35. };
  36.  
  37. struct Derived
  38.     : public Base
  39. {
  40. 	int di;
  41.     Derived() {std::cout << "Derived()\n";}
  42.     Derived(const Base&) = delete;
  43.     Derived& operator=(const Derived&) = delete;
  44.     virtual ~Derived() {std::cout << "~Derived()\n";}
  45. };
  46.  
  47. int
  48. main()
  49. {
  50.     std::unique_ptr<Derived, void(*)(Base*)> p(allocate<Derived>(), deallocate<Base,Derived>);
  51.     std::unique_ptr<Base, void(*)(Base*)> p2 = std::move(p);
  52.     std::unique_ptr<Derived, void(*)(Base*)> p3(allocate<Derived>(), deallocate<Base,Derived>);
  53.  
  54. }
Success #stdin #stdout 0s 3432KB
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Standard input is empty
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Base()
Derived()
0x8947008
Base()
Derived()
0x8947018
0x894701c
~Derived()
~Base()
0x8947018
0x894700c
~Derived()
~Base()
0x8947008
https://ideone.com/521Q7V
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
public

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