SUPPORTED_TYPE(char, 'c');
SUPPORTED_TYPE(int, 'd');
SUPPORTED_TYPE(unsigned, 'u');
SUPPORTED_TYPE(char*, 's');
SUPPORTED_TYPE(const char*, 's');
SUPPORTED_TYPE(std::string, 's');
SUPPORTED_TYPE(boost::string_ref, 's');
SUPPORTED_TYPE(double, 'f');
SUPPORTED_TYPE(float, 'f');