Template variable specialization (for template template)

Question

When I try to specialize a template variable for a universal container (for example, std::list<...>but not for a specific one, for example std::list<double>), I get a communication error with gcc 5.3(but not with clang 3.5)

/tmp/ccvxFv3R.s: Assembler messages:
/tmp/ccvxFv3R.s:206: Error: symbol `_ZL9separator' is already defined

http://coliru.stacked-crooked.com/a/38f68c782d385bac

#include<string>
#include<iostream>
#include<list>
#include<forward_list>
#include<vector>

template<typename T> std::string const separator = ", ";
template<typename... Ts> std::string const separator<std::list<Ts...>        > = "<->";
template<typename... Ts> std::string const separator<std::forward_list<Ts...>> = "->";

int main(){

    std::cout << separator<std::vector<double>> << '\n';
    std::cout << separator<std::list<double>> << '\n';
    std::cout << separator<std::forward_list<double>> << '\n';

}

(This compiles well with help clang 3.5and works as expected. Also, the variational pattern does not cause problems, I tried to use an invariant pattern).

If this is not a mistake gcc, do you think there is a job? I tried to use class specialization, but this is not possible:

template<class T>
struct separator{
    static std::string const value;
};
template<class T>
std::string const separator<T>::value = ", ";
template<typename... Ts>
std::string const separator<std::list<Ts...>>::value = "<->";
template<typename... Ts>
std::string const sep<std::forward_list<Ts...>>::value = "->";

Answer 1

, gcc. ( ), , @T.C. .

template<class T>
struct sep{
    static const std::string value;
};
template<class T>
const std::string sep<T>::value = ", ";

template<typename... Ts>
struct sep<std::list<Ts...>>{
    static const std::string value;
};
template<typename... Ts>
const std::string sep<std::list<Ts...>>::value = "<->";

template<typename... Ts>
struct sep<std::forward_list<Ts...>>{
    static const std::string value;
};
template<typename... Ts>
const std::string sep<std::forward_list<Ts...>>::value = "->";

( )

template<typename T> std::string const separator = sep<T>::value;

gcc, clang.

---

@T.C., ( )

template<class T>
struct sep{
    static std::string value(){return ", ";}
};
template<typename... Ts>
struct sep<std::list<Ts...>>{
    static std::string value(){return "<->";}
};

template<typename... Ts>
struct sep<std::forward_list<Ts...>>{
    static std::string value(){return "->";}
};
...
template<typename T> std::string const separator = sep<T>::value();

---

constexpr const char*

template<class T>
struct sep{static constexpr const char* value = ", ";};

template<typename... Ts>
struct sep<std::list<Ts...>>{static constexpr const char* value = "<->";};

template<typename... Ts>
struct sep<std::forward_list<Ts...>>{static constexpr const char* value = "->";};
...
template<typename T> std::string const separator = sep<T>::value;

const_str (a constexpr - std::string), .