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#ifndef TYPETOKEN_HPP_
#define TYPETOKEN_HPP_
 
#include <atomic>
 
namespace typetoken
{
 
	using token_t = std::size_t;
	template<typename T> token_t getToken(void);
 
	class tokenbase {
	private:
		tokenbase(void) = delete;
		static volatile std::atomic<token_t> counter;
 
		template<typename Q>
		friend token_t getToken(void);
	};
 
	template<typename T>
	struct typetoken : tokenbase {
	private:
		typetoken(void) = delete;
		static token_t ID;
 
		template<typename Q>
		friend token_t getToken(void);
	};
 
	template<typename T>
	token_t typetoken<T>::ID = 0;
 
	template<typename T>
	token_t getToken(void) {
		typedef typetoken<T> token;
		if (!token::ID) {
			token::ID = ++token::counter;
		}
		return token::ID;
	}
} // namespace typetoken
 
#endif /* TYPETOKEN_HPP_ */
 
#include <iostream>
 
int main(){
	std::cout << typetoken::getToken<int>() << ' ' << typetoken::getToken<signed int>() << ' ' << typetoken::getToken<char>() << ' ' << typetoken::getToken<int>() << '\n';
}
 

/home/osozHv/ccG7l86y.o: In function `unsigned int typetoken::getToken<int>()':
prog.cpp:(.text._ZN9typetoken8getTokenIiEEjv[_ZN9typetoken8getTokenIiEEjv]+0x16): undefined reference to `typetoken::tokenbase::counter'
/home/osozHv/ccG7l86y.o: In function `main':
prog.cpp:(.text.startup+0x25): undefined reference to `typetoken::tokenbase::counter'
collect2: error: ld returned 1 exit status

Standard output is empty