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  1. #include <memory>
  2. #include <new>
  3. #include <cstdlib>
  4.  
  5. template<typename T, typename... Args>
  6. T*
  7. allocate(Args&&... args)
  8. {
  9.     std::unique_ptr<T, void(*)(void*)> hold(static_cast<T*>(std::malloc(sizeof(T))),
  10.                                                             std::free);
  11.     ::new (hold.get()) T(std::forward<Args>(args)...);
  12.     return static_cast<T*>(hold.release());
  13. }
  14.  
  15. template<typename T>
  16. void
  17. deallocate(void* p)
  18. {
  19.     static_cast<T*>(p)->~T();
  20.     std::free(p);
  21. }
  22.  
  23. #include <iostream>
  24.  
  25. struct Base
  26. {
  27.     int i;
  28.     Base(int i) : i(i) {std::cout << "Base() " << i << std::endl ;}
  29.     Base(const Base&) = delete;
  30.     Base& operator=(const Base&) = delete;
  31.     ~Base() {std::cout << "~Base() " << i << std::endl;}
  32.  
  33.     virtual void bark() const {std::cout << "Hi Base! " << i << std::endl;}
  34. };
  35.  
  36. struct Derived
  37.     : public Base
  38. {
  39.     double d;
  40.     Derived(int i, double d) : Base(i), d(d) {std::cout << "Derived() " << i << " " << d << std::endl;}
  41.     Derived(const Base&) = delete;
  42.     Derived& operator=(const Derived&) = delete;
  43.     ~Derived() {std::cout << "~Derived() " << i << " " << d << std::endl;}
  44.  
  45.     void bark() const {std::cout << "Hi Derived! " << i << " " << d << std::endl;}
  46. };
  47.  
  48. int
  49. main()
  50. {
  51.     std::unique_ptr<Base, void(*)(void*)> p(allocate<Derived>(42, 10.42), deallocate<Derived>);
  52.     p->bark();
  53.     std::unique_ptr<Base, void(*)(void*)> p2 = std::move(p);
  54.     p2->bark();
  55. }
  56.  
Success #stdin #stdout 0.01s 5340KB
comments (?)
stdin 
Standard input is empty
stdout 
Base() 42
Derived() 42 10.42
Hi Derived! 42 10.42
Hi Derived! 42 10.42
~Derived() 42 10.42
~Base() 42
https://ideone.com/bIBHpt
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
public

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