C++ strcat(template版本)

template<unsigned N, unsigned M>
inline std::shared_ptr<char> strcat(const char (&p1)[N], const char (&p2)[M])
{
    std::shared_ptr<char> s1(new char[N]);
    char s2[M];
    std::strcpy(s1.get(), p1);
    std::strcpy(s2, p2);
    std::strcat(s1.get(), s2);
    return s1;
};