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  1. #include <iostream>
  2.  
  3. template<typename T> struct identity { typedef T type; };
  4. template<typename T> inline T implicit_cast(typename identity<T>::type x) { return x; }
  5.  
  6. class Base {
  7. protected:
  8.     Base(Base const&) { std::cout << "Base copy ctor"; }
  9.  
  10.     template<typename T>
  11.     Base(T&&)         { std::cout << "universal Base ctor"; }
  12.  
  13.     Base() {}
  14.  
  15.     ~Base() {}
  16. };
  17.  
  18. class NotDeclared : private Base {
  19.     // use implicit compiler-generated constructors
  20. };
  21.  
  22. class DeclaredDefault : private Base {
  23. public:
  24.     DeclaredDefault(DeclaredDefault const&) = default;
  25.  
  26.     DeclaredDefault() {}
  27. };
  28.  
  29. class DefinedPlain : private Base {
  30. public:
  31.     DefinedPlain(DefinedPlain const& other) : Base(other) {}
  32.  
  33.     DefinedPlain() {}
  34. };
  35.  
  36. class DefinedCastToBase : private Base {
  37. public:
  38.     DefinedCastToBase(DefinedCastToBase const& other) : Base(implicit_cast<Base const&>(other)) {}
  39.  
  40.     DefinedCastToBase() {}
  41. };
  42.  
  43. int main()
  44. {
  45.     using std::cout; using std::endl;
  46.  
  47.     NotDeclared nd;
  48.     DeclaredDefault dd;
  49.     DefinedPlain dp;
  50.     DefinedCastToBase dctb;
  51.  
  52.     cout << "NotDeclared       : "; NotDeclared nd2(nd);           cout << endl;
  53.     cout << "DeclaredDefault   : "; DeclaredDefault dd2(dd);       cout << endl;
  54.     cout << "DefinedPlain      : "; DefinedPlain dp2(dp);          cout << endl;
  55.     cout << "DefinedCastToBase : "; DefinedCastToBase dctb2(dctb); cout << endl;
  56. }
Success #stdin #stdout 0s 2896KB
comments (?)
stdin
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Standard input is empty
stdout
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NotDeclared       : Base copy ctor
DeclaredDefault   : Base copy ctor
DefinedPlain      : universal Base ctor
DefinedCastToBase : Base copy ctor
https://ideone.com/TrgGyi
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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