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  1. #include <iostream>
  2.  
  3. using namespace std;
  4.  
  5. template<class T> class CBase
  6. {
  7.     public:
  8.         template <class T2> CBase(const T2 &x) : _var(x) {;}
  9.         template <class T2> CBase (const CBase<T2> &x) {_var = x.var();}
  10.         ~CBase() {;}
  11.         T var() const {return _var;}
  12.     protected:
  13.         T _var;
  14. };
  15.  
  16. template<class T> class CDerived : public CBase<T>
  17. {
  18.     public:
  19.         template <class T2> CDerived(const T2 &x) : CBase<T>(x) {;}
  20.         template <class T2> CDerived(const CDerived<T2> &x) : CBase<T>(x.var()) {;}
  21.         template <class T2> CDerived (const CBase<T2> &x) : CBase<T>(x) {;}
  22.         ~CDerived() {;}
  23. };
  24.  
  25. int main()
  26. {
  27.     CBase<double> bd(3);
  28.     CBase<int> bi(bd); // <- No problem
  29.     CDerived<double> dd1(3);
  30.     CDerived<double> dd2(dd1);
  31.     CDerived<int> di(dd1); // <- The problem is here
  32.     return 0;
  33. }
Success #stdin #stdout 0s 2780KB
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https://ideone.com/CAQ8q
language:
C++14 (gcc 8.3)
created:
11 years ago
visibility:
public

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