integer %=
    attr_cast<int,std::string>(
    lexeme[
        -(char_('+') | char_('-')) >>
        char_("1-9") >> *char_("0-9")
    ]
    )
    ;

template <>
struct transform_attribute<int, std::string, qi::domain>
{
    // input type
    typedef std::string& type;

    static std::string pre(int & d) {
        return "";
    }
    static void post(int & val, const type attr) {
        val = boost::lexical_cast<int>(attr);
    }
    static void fail(int &) {}
};

integer %= qi::int_; // Job Done

bool ok = parse(f, l,
        (matches['-']  | -lit('+') >> attr(false)) [ phx::ref(negative) = _1 ] >> // sign
        eps    [ _val = 0 ] >>
        +digit [ _val *= 10, _val += (_1 - '0') ],
        parsed);

namespace boost { namespace spirit { namespace traits {

    template <typename Int>
        struct assign_to_attribute_from_value<
            Int,
            std::string,
            typename std::enable_if<std::is_integral<Int>::value, void>::type // Enabler
            >
        {
            static void call(std::string const& val, Int& attr) {
                //std::cout << __PRETTY_FUNCTION__ << "('" << val << "')n";
                attr = boost::lexical_cast<Int>(val);
            }
        };

} } }

// boost lexical_cast does not usefully support `char` types as integrals... (SIC)
template <>
    struct assign_to_attribute_from_value<signed char, std::string> {
        static void call(std::string const& val, signed char& attr) {
            int tmp;
            assign_to_attribute_from_value<int, std::string>::call(val, tmp);
            attr = static_cast<signed char>(tmp);
        }
    };

template <>
    struct assign_to_attribute_from_value<unsigned char, std::string> {
        static void call(std::string const& val, unsigned char& attr) {
            unsigned int tmp;
            assign_to_attribute_from_value<unsigned int, std::string>::call(val, tmp);
            attr = static_cast<unsigned char>(tmp);
        }
    };

Int parsed = 0;
    bool ok = parse(f, l, as_string [ -char_("-+") >> +digit ], parsed);

Int parsed = 0;
 bool ok = qi::parse(f, l, qi::auto_, parsed);

#include <boost/spirit/include/qi.hpp>

template <typename Int>
void do_test() {
    for (Int const testcase : { std::numeric_limits<Int>::min(), Int(), std::numeric_limits<Int>::max() }) {
        auto const input = std::to_string(testcase);
        auto f(input.begin()), l(input.end());

        Int parsed = 0;
        bool ok = boost::spirit::qi::parse(f, l, boost::spirit::qi::auto_, parsed);

        if (!ok || f!=l)
            throw std::runtime_error("parse error");

        std::cout << std::boolalpha << (testcase==parsed) << "t" << testcase << " -> " << parsed << "n";
    }
}

int main() {
    do_test<int16_t>();  do_test<uint16_t>();
    do_test<int32_t>();  do_test<uint32_t>();
    do_test<int64_t>();  do_test<uint64_t>();
    do_test<intmax_t>(); do_test<uintmax_t>();
}