boost Spirit 语法错误 - “‘struct boost::spirit::unused_type’中没有名为‘size’的类型”

Question

请帮助我诊断以下错误。我有一个简单的语法：

struct json_start_elem_grammar_object : qi::grammar<StreamIterator,
                                                  void(const CharType*, CharType),
                                                  ascii::space_type>
{
  json_start_elem_grammar_object() : json_start_elem_grammar_object::base_type(start_elem, "start_elem")
  {
    start_elem =  qi::lit('"') > qi::lit(qi::_1) > qi::lit('"') > qi::lit(':') >
                  qi::lit(qi::_2) > -qi::lit('\n');
  }

  qi::rule<StreamIterator, void(const CharType*, CharType), ascii::space_type>  start_elem;
};

创建此语法的实例时出现错误：

/usr/include/boost/spirit/home/qi/nonterminal/rule.hpp:220:19:   required from ‘boost::spirit::qi::rule<Iterator, T1, T2, T3, T4>& boost::spirit::qi::rule<Iterator, T1, T2, T3, T4>::operator=(const Expr&) [with Expr = boost::proto::exprns_::expr<boost::proto::tagns_::tag::greater, boost::proto::argsns_::list2<const boost::proto::exprns_::expr<boost::proto::tagns_::tag::greater, boost::proto::argsns_::list2<const boost::proto::exprns_::expr<boost::proto::tagns_::tag::greater, boost::proto::argsns_::list2<const boost::proto::exprns_::expr<boost::proto::tagns_::tag::greater, boost::proto::argsns_::list2<const boost::proto::exprns_::expr<boost::proto::tagns_::tag::greater, boost::proto::argsns_::list2<const boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::terminal_ex<boost::spirit::tag::lit, boost::fusion::vector1<char> > >, 0l>&, const boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::lazy_terminal<boost::spirit::tag::lit, boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::detail::function_eval<1>, boost::fusion::vector<boost::phoenix::value<boost::spirit::terminal<boost::spirit::tag::lit> >, boost::spirit::argument<0>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > >, 1> >, 0l>&>, 2l>&, const boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::terminal_ex<boost::spirit::tag::lit, boost::fusion::vector1<char> > >, 0l>&>, 2l>&, const boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::terminal_ex<boost::spirit::tag::lit, boost::fusion::vector1<char> > >, 0l>&>, 2l>&, const boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::lazy_terminal<boost::spirit::tag::lit, boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::detail::function_eval<1>, boost::fusion::vector<boost::phoenix::value<boost::spirit::terminal<boost::spirit::tag::lit> >, boost::spirit::argument<1>, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_, boost::fusion::void_> > >, 1> >, 0l>&>, 2l>&, const boost::proto::exprns_::expr<boost::proto::tagns_::tag::negate, boost::proto::argsns_::list1<const boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::terminal_ex<boost::spirit::tag::lit, boost::fusion::vector1<char> > >, 0l>&>, 1l>&>, 2l>; Iterator = boost::spirit::basic_istream_iterator<char>; T1 = void(const char*, char); T2 = boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0l>; T3 = boost::spirit::unused_type; T4 = boost::spirit::unused_type]’
/home/marcin/workspace/json_archive/basic_json_grammar.hpp:149:18:   required from ‘boost::archive::basic_json_grammar<CharType>::json_start_elem_grammar_object::json_start_elem_grammar_object() [with CharType = char]’
/home/marcin/workspace/json_archive/basic_json_grammar.hpp:194:50:   required from ‘boost::archive::basic_json_grammar<CharType>::basic_json_grammar() [with CharType = char]’
/home/marcin/workspace/json_archive/json_iarchive_impl.ipp:141:85:   required from ‘boost::archive::json_iarchive_impl<Archive>::json_iarchive_impl(std::istream&, unsigned int) [with Archive = boost::archive::naked_json_iarchive; std::istream = std::basic_istream<char>]’
/home/marcin/workspace/json_archive/json_iarchive.hpp:102:68:   required from here
/usr/include/boost/fusion/sequence/intrinsic/size.hpp:33:20: error: no type named ‘size’ in ‘struct boost::spirit::unused_type’
         struct unsegmented_size : Sequence::size {};

在哪里

using CharType = char;
using StreamIterator = spirit::basic_istream_iterator<CharType>;

在处理 boost.serialization 和 boost.spirit 编译错误几天后，我完全脑死了，似乎被困在这个问题上：/

这个语法的用法（略简化）是：

json_start_elem_grammar_object start_elem_parser_object;
using invoker = _details::invoke_grammar<CharType, decltype(start_elem_parser_object(name, preamble))>;

invoker::apply( is,
              start_elem_parser_object(name, preamble),
              "Invalid object element in archive");

在哪里

decltype(is) = IStream& 
decltype(name) = const CharType* 
decltype(preamble) = CharType 


template<typename CharType, typename Expr>
struct invoke_grammar<CharType, Expr> {
 using IStream = std::basic_istream<CharType>;
 using StreamIterator = spirit::basic_istream_iterator<CharType>;

 static void apply(IStream & is, Expr const& grammar, const CharType* errMsg)
 {
   boost::io::ios_flags_saver ifs(is);
   is.unsetf (std::ios::skipws);

   StreamIterator it_end;
   StreamIterator it_beg (is);

   if (!qi::phrase_parse(it_beg, it_end,
                        grammar,
                        ascii::space))
   {
     boost::serialization::throw_exception(
       archive_exception(archive_exception::invalid_signature, errMsg)
     );
   }
 }
};

Answer 1

就像我评论的那样，您需要使用 qi::_r1 和 qi::_r2，inherited attributes 的占位符^[1]。

对于其余部分，我可以假设（因为您的代码不完整，并且由于非标准方法对我来说有点不清楚）：

• 您可能希望 ascii::blank_type 作为船长，否则 lit('\n') 将永远不会匹配（除非与 no_skip[] 或 lexeme[] 匹配）。

• 您必须小心使用实际的CharType const* 调用解析器，而不是CharType const (&)[]。如果您使用例如调用它，则会发生后者parser("name", 'a')。相反，无论是

  • 引入一个临时变量
  • 演员表
  • 隐式衰减使用例如+"name"

我做了一个例子，它成功了，看看它Live on Coliru

完整代码：

#define BOOST_SPIRIT_USE_PHOENIX_V3
#include <boost/fusion/adapted.hpp>
#include <boost/spirit/include/qi.hpp>

namespace qi    = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;

template <typename StreamIterator, typename CharType=char>
struct json_start_elem_grammar_object : qi::grammar<StreamIterator,
    void(const CharType*, CharType),
    ascii::blank_type>
{
    json_start_elem_grammar_object() : json_start_elem_grammar_object::base_type(start_elem, "start_elem")
    {
        using namespace qi;
        _r1_type _name;     // prefer descriptive names
        _r2_type _preamble;

        start_elem = 
            '"' > lit(_name) > '"' > 
            ':' > lit(_preamble) > 
            -lit('\n')
            ;
    }

    qi::rule<StreamIterator, void(const CharType*, CharType), ascii::blank_type>  start_elem;
};

bool doParse(const std::string& input)
{
    typedef std::string::const_iterator It;
    auto f(begin(input)), l(end(input));

    json_start_elem_grammar_object<It> p;

    try
    {
        bool ok = qi::phrase_parse(f, l, p(+"lol", 'q'), ascii::blank);
        if (ok)   
        {
            std::cout << "parse success\n";
        }
        else      std::cerr << "parse failed: '" << std::string(f,l) << "'\n";

        if (f!=l) std::cerr << "trailing unparsed: '" << std::string(f,l) << "'\n";
        return ok;
    } catch(const qi::expectation_failure<It>& e)
    {
        std::string frag(e.first, e.last);
        std::cerr << e.what() << "'" << frag << "'\n";
    }

    return false;
}

int main()
{
    bool ok = doParse("\"lol\" : q\n");
    return ok? 0 : 255;
}

---

^[1]另见

• non-terminals 的文档
• mini-xml example from the tutorial