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  1. class Base
  2. {
  3. public:
  4.     void foo() {} // Dummy method to clarify the example
  5. };
  6.  
  7. class PublicChild : public Base
  8. {
  9. public:
  10.     void test()
  11.     {
  12.         foo(); // OK, we have access to Base public members
  13.         static_cast<Base*>(this)->foo(); // OK
  14.     }
  15.     friend class PublicFriend;
  16. };
  17.  
  18. class PublicFriend
  19. {
  20.     void test(PublicChild* p)
  21.     {
  22.         p->foo(); // OK, the method is public anyway
  23.         static_cast<Base*>(p)->foo(); // OK
  24.     }
  25. };
  26.  
  27. class ProtectedChild : protected Base
  28. {
  29. public:
  30.     void test()
  31.     {
  32.         foo(); // OK, we have access to Base public members
  33.         static_cast<Base*>(this)->foo(); // OK
  34.     }
  35.     friend class ProtectedFriend;
  36. };
  37.  
  38. class ProtectedFriend
  39. {
  40.     void test(ProtectedChild* p)
  41.     {
  42.         p->foo(); // OK, because we are a friend of ProtectedChild, we have the same visibility as ProtectedChild itself
  43.         static_cast<Base*>(p)->foo(); // OK
  44.     }
  45. };
  46.  
  47. class PrivateChild : private Base
  48. {
  49. public:
  50.     void test()
  51.     {
  52.         foo(); // OK, we have access to Base public members
  53.         static_cast<Base*>(this)->foo(); // OK
  54.     }
  55.     friend class PrivateFriend;
  56. };
  57.  
  58. class PrivateFriend
  59. {
  60.     void test(PrivateChild* p)
  61.     {
  62.         p->foo(); // OK, because we are a friend of PrivateChild, we have the same visibility as PrivateChild itself
  63.         static_cast<Base*>(p)->foo(); // OK
  64.     }
  65. };
  66.  
  67. int main()
  68. {
  69.     Base b;
  70.     b.foo(); // OK: public method
  71.  
  72.     PublicChild p1;
  73.     p1.foo(); // OK: public inheritance makes Base::foo public
  74.     static_cast<Base>(p1).foo(); // OK
  75.  
  76.     ProtectedChild p2;
  77.     // p2.foo(); // error: protected inheritance makes Base::foo protected
  78.     // static_cast<Base>(p2).foo(); // error
  79.  
  80.     PrivateChild p3;
  81.     // p3.foo(); // error: private inheritance makes Base::foo private
  82.     // static_cast<Base>(p3).foo(); // error
  83.  
  84. 	return 0;
  85. }
Success #stdin #stdout 0s 4388KB
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https://ideone.com/Zbaqbu
language:
C++ (gcc 8.3)
created:
7 years ago
visibility:
public

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