Compile-time simple format string check.

gistfile1.cpp

template<typename T>
struct FormatTraits;

template<std::size_t N>
struct FormatTraits<char[N]> {
    constexpr static bool supports(char c) {
        return c == 's';
    }
};

#define DECLARE_SUPPORTED_FORMAT(__type, __char) \
    template<> \
    struct FormatTraits<__type> { \
        constexpr static bool supports(char c) { \
            return c == __char; \
        } \
    }

DECLARE_SUPPORTED_FORMAT(char, 'c');
DECLARE_SUPPORTED_FORMAT(unsigned int, 'o');
DECLARE_SUPPORTED_FORMAT(int, 'd');
DECLARE_SUPPORTED_FORMAT(double, 'f');
DECLARE_SUPPORTED_FORMAT(std::string, 's');

template<std::size_t N, class T>
constexpr bool check_format_helper(const T(&format)[N], std::size_t current) {
    return current == N ? true : format[current] != '%' ?
                check_format_helper(format, current + 1) : format[current + 1] == '%' ?
                check_format_helper(format, current + 2) : false;

}

template<std::size_t N, class T, class Arg, class... Args>
constexpr bool check_format_helper(const T(&format)[N], std::size_t current, Arg const& arg, Args const& ...args) {
    return current == N ?
                false :
                format[current] != '%' ?
                check_format_helper(format, current + 1, arg, args...) :
                format[current + 1] == '%' && format[current + 2] == '%' ?
                    check_format_helper(format, current + 2, arg, args...) :
                    FormatTraits<Arg>::supports(format[current + 1]) && check_format_helper(format, current + 2, args...);
}

template<class T, std::size_t N, class... Args>
constexpr bool check_format(const T(&format)[N], Args const& ... args) {
    return check_format_helper(format, 0, args...);
}

// usage: static_assert(check_format("this is %s and %d", "blah-blah", 10), "ha-ha, you suck!");