fork download
copy 
  1. #include <type_traits>
  2. #include <utility>
  3.  
  4. template< typename T >
  5. class clone_ptr_polymorph
  6. {
  7.     void* mDerivedPtr;
  8.     T* mBasicPtr;
  9.     std::pair<T*, void*> (* mCloner)(void*);  
  10.  
  11.     template< typename Derived >
  12.     static std::pair<T*, void*> clone(void* ptr)
  13.     {
  14.     	auto obj = new Derived{ *reinterpret_cast<Derived*>(ptr) };
  15.     	return { obj, obj };
  16.     }
  17.  
  18. public:
  19.     template< typename Derived,
  20.               typename=typename std::enable_if<std::is_base_of<T, Derived>::value>::type >
  21.     clone_ptr_polymorph( Derived* ptr ) :
  22.         mDerivedPtr{ptr},
  23.         mBasicPtr{ptr},
  24.         mCloner{ &clone<Derived> } {}
  25.  
  26.     clone_ptr_polymorph( clone_ptr_polymorph const& p ) :
  27.         mCloner{p.mCloner}
  28.     {
  29.     	auto pair = mCloner(p.mDerivedPtr);
  30.     	mBasicPtr = pair.first;
  31.     	mDerivedPtr = pair.second;
  32.     }
  33.  
  34.     ~clone_ptr_polymorph()
  35.     {
  36.     	delete mBasicPtr;
  37.     }
  38.  
  39.     clone_ptr_polymorph( clone_ptr_polymorph&& ) = default;
  40.     clone_ptr_polymorph& operator=( clone_ptr_polymorph&& ) = default;
  41. };
  42.  
  43. template<typename Base,
  44.          typename Der,
  45.          typename... Args>
  46. clone_ptr_polymorph<Base> make_clone_ptr( Args&&... args )
  47. {
  48. 	return { new Der(std::forward<Args>(args)...) };
  49. }
  50.  
  51. #include <iostream>
  52.  
  53. struct Base
  54. {
  55. 	virtual ~Base() { std::cout << "Base-Destructor\n"; }
  56. 	Base() { std::cout << "Base-Def-Ctor\n"; }
  57. 	Base(Base const&) { std::cout << "Base-Copy-Ctor\n"; }
  58. 	Base(Base&&) { std::cout << "Base-Move-Ctor\n"; }
  59. };
  60.  
  61. struct Derived : Base
  62. {
  63. 	~Derived() { std::cout << "Derived-Destructor\n"; }
  64. 	Derived() { std::cout << "Derived-Def-Ctor\n"; }
  65. 	Derived(Derived const&) { std::cout << "Derived-Copy-Ctor\n"; }
  66. 	Derived(Derived&&) { std::cout << "Derived-Move-Ctor\n"; }
  67. };
  68.  
  69. int main()
  70. {
  71. 	auto const& p = make_clone_ptr<Base, Derived>();
  72. 	auto second = p;
  73. }
  74.  
  75.  
Success #stdin #stdout 0s 3472KB
comments (?)
stdin
copy 
Standard input is empty
stdout
copy 
Base-Def-Ctor
Derived-Def-Ctor
Base-Def-Ctor
Derived-Copy-Ctor
Derived-Destructor
Base-Destructor
Derived-Destructor
Base-Destructor
https://ideone.com/MQ2xTv
language:
C++14 (gcc 8.3)
created:
12 years ago
visibility:
secret

Share or Embed source code

Discover > Sphere Engine API

The brand new service which powers Ideone!

Discover > IDE Widget

Widget for compiling and running the source code in a web browser!