[boost] [spirit][qi] strange attribute composition when using expectation points

Subject: [boost] [spirit][qi] strange attribute composition when using expectation points
From: Evonik Energy Services GmbH (tobias.loew_at_[hidden])
Date: 2010-09-10 03:52:48

Hi,

I get a different attribute composition depending on the use of expectation points. Here is a small example:

////////////////////////////////////////////////////////////////////////////////////////////////
//

BOOST_FUSION_DEFINE_STRUCT(
    (client), input,
    (int,    index1)
    (std::string, text)
    (int,    index2)
)

namespace client {

    namespace fusion = boost::fusion;
    namespace phoenix = boost::phoenix;
    namespace qi = boost::spirit::qi;
    namespace char_enc = boost::spirit::iso8859_1;

    template <typename Iterator, typename Skipper>
    struct line_grammar
        : qi::grammar<Iterator, input(), Skipper>
    {
        line_grammar()
          : line_grammar::base_type(line)
        {
            using qi::int_;
            using qi::omit;
            using char_enc::char_;
            using qi::lit;

            line =
                    int_
                    >> lit(",")
#ifdef USE_EXPECTATION_POINT
                    >  *(char_ - ( "," >> int_  ) )
#else
                    >> *(char_ - ( "," >> int_  ) )
#endif
                    >> lit(",")
                    >> int_

                ;

        }

        qi::rule<Iterator, input(),  Skipper > line;

    };

    bool read_line(  )
    {
        typedef line_grammar<std::string::const_iterator, char_enc::space_type> grammar;

        grammar gr; // Our grammar

        input line_read;

        std::string source = "1,x,2";
        std::string::const_iterator iter = source.begin();
        std::string::const_iterator end = source.end();
        bool r = phrase_parse(iter, end, gr,
            char_enc::space,
            line_read);

        return r && iter == end;
    }

}

//
/////////////////////////////////////////////////////////////////////////////////////////////////////////

If USE_EXPECTATION_POINT is not defined then parsing succeeds and line_read == {1, "x", 2 }.
But if USE_EXPECTATION_POINT  is defined then parsing also succeeds but line_read == {1, "x\0x2", 0 }.
So, it seems that expectation points somehow break the semantics of attribute composition.

Tobias