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  1. #include <iostream>
  2. #include <list>
  3.  
  4. namespace NS1 
  5. {
  6.     template <class T>
  7.         class Base
  8.         {   
  9.         protected:
  10.             Base()
  11.             {   
  12.                 instances.push_back(static_cast<T*>(this));
  13.             }   
  14.         private:
  15.             static std::list<T*> instances;
  16.         };  
  17.  
  18.         class Derived : public Base<Derived>
  19.         {   
  20.         public:
  21.             Derived()
  22.                 :Base<Derived>()
  23.             {   
  24.             }   
  25.         };  
  26. }
  27.  
  28. template <> std::list<NS1::Derived*> NS1::Base<NS1::Derived>::instances;
  29.  
  30. int main()
  31. {
  32.     NS1::Derived d;
  33.     return 0;
  34. }
  35.  
Compilation error #stdin compilation error #stdout 0s 0KB
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stdin
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Standard input is empty
compilation info 
/home/Yyyqn1/ccGSPRP5.o: In function `main':
prog.cpp:(.text+0x5c): undefined reference to `NS1::Base<NS1::Derived>::instances'
collect2: ld returned 1 exit status
stdout
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Standard output is empty
https://ideone.com/rFab5
language:
C++ (gcc 8.3)
created:
14 years ago
visibility:
public

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