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  1.  
  2. template<typename T>
  3. class Base
  4. {
  5.    template<typename U>
  6.    friend void f(void *ptr) {
  7.      static_cast<Base<U>*>(ptr)->run();
  8.    }
  9.    protected:
  10.        virtual void run() = 0; 
  11. };
  12.  
  13. class A : public Base<A>
  14. {
  15.    protected:
  16.        virtual void run() {}
  17. };
  18.  
  19. /*
  20. class B : public Base<B>
  21. {
  22.    protected:
  23.        virtual void run() {}
  24. };
  25. */
  26.  
  27. int main()
  28. {
  29.    A a;
  30.    f<A>(&a);
  31. }
Success #stdin #stdout 0.01s 2720KB
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https://ideone.com/VU72N
language:
C++ (gcc 8.3)
created:
12 years ago
visibility:
public

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