c++ - linking errors while separate parser using boost spirit x3

Question

I am currentyl trying to separate my boost spirit x3 parser into different _def and .cpp files using BOOST_SPIRIT_DEFINE/DECLARE/INSTANTIATE, but I keep getting a linking error. HERE is my parser which is separated.

The linker error reads

<artificial>:(.text.startup+0xbb): undefined reference to `bool kyle::parser::impl::parse_rule<__gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::x3::context<boost::spirit::x3::skipper_tag, boost::spirit::x3::char_class<boost::spirit::char_encoding::standard, boost::spirit::x3::space_tag> const, boost::spirit::x3::unused_type>, boost::spirit::x3::unused_type const>(boost::spirit::x3::rule<kyle::parser::impl::identifier_class, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, false>, __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, __gnu_cxx::__normal_iterator<char*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > const&, boost::spirit::x3::context<boost::spirit::x3::skipper_tag, boost::spirit::x3::char_class<boost::spirit::char_encoding::standard, boost::spirit::x3::space_tag> const, boost::spirit::x3::unused_type> const&, boost::spirit::x3::unused_type const&)'

What am I doing wrong? How can I make my example work?

• config.hpp:

  #include <boost/spirit/home/x3.hpp>
  
  namespace kyle{
  namespace parser{
  
  namespace x3 = boost::spirit::x3;
  
  typedef std::string::const_iterator iterator_type;
  typedef x3::phrase_parse_context<x3::ascii::space_type>::type context_type;
  
  }
  }
  

• literals.cpp:

  #include "literals_def.hpp"
  #include "config.hpp"
  #include <boost/spirit/home/x3.hpp>
  
  
  namespace kyle {
  namespace parser {
  namespace impl {
  
  BOOST_SPIRIT_INSTANTIATE(identifier_type, iterator_type, context_type);
  
  }
  }
  }
  

• literals_def.hpp:

  #include <boost/spirit/home/x3.hpp>
  #include "literals.hpp"
  
  namespace kyle {
  namespace parser {
  namespace impl {
  
  namespace x3 = boost::spirit::x3;
  
  
  const identifier_type identifier = "identifier";
  
  
  
  auto const identifier_def = x3::alpha >> *x3::alnum;
  
  BOOST_SPIRIT_DEFINE(identifier)
  }
  impl::identifier_type identifier(){
      return impl::identifier;
  }
  
  
  }
  }
  

• literals.hpp:

  #include <boost/spirit/home/x3.hpp>
  
  namespace kyle{
  namespace parser{
  namespace impl {
  namespace x3 = boost::spirit::x3;
  
  struct identifier_class;
  
  typedef x3::rule<identifier_class, std::string> identifier_type;
  
  BOOST_SPIRIT_DECLARE(identifier_type)
  }
  
  impl::identifier_type identifier();
  
  
  }
  }
  

• main.cpp:

  #include "literals.hpp"
  #include <iostream>
  
  template<typename Parser>
  bool test(std::string str, Parser&& p, bool full_match = true)
  {
      auto in = str.begin();
      auto end = str.end();
      bool ret = boost::spirit::x3::phrase_parse(in, end, p, boost::spirit::x3::space);
      ret &= (!full_match || (in == end));
      return ret;
  
  }
  
  int main(){
      auto b = test("fobar", kyle::parser::identifier());
      std::cout << b << std::endl;
  
  }
  

Answer 1

Two points:

1. You define the context as

   typedef x3::phrase_parse_context<x3::space_type>::type context_type;
   

   However, you try to invoke it with x3::space instead of x3::ascii::space.

   The hint was in the error message that you didn't include:

   /home/sehe/custom/boost/boost/spirit/home/x3/nonterminal/rule.hpp:116: undefined reference to 'bool kyle::parser::impl::parse_rule<__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::x3::context<boost::spirit::x3::skipper_tag, boost::spirit::x3::char_class<boost::spirit::char_encoding::standard, boost::spirit::x3::space_tag> const, boost::spirit::x3::unused_type>, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >(boost::spirit::x3::rule<kyle::parser::impl::identifier_class, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, false>, __gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, __gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > const&, boost::spirit::x3::context<boost::spirit::x3::skipper_tag, boost::spirit::x3::char_class<boost::spirit::char_encoding::standard, boost::spirit::x3::space_tag> const, boost::spirit::x3::unused_type> const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&)'

2. Iterator type is getting deduced as std::string::iterator, not std::string::const_iterator. Fix it or don't use auto always:

Live On Melpon

FULL CODE

For posterity

• config.hpp:

  #include <boost/spirit/home/x3.hpp>
  
  namespace kyle{
      namespace parser{
  
          namespace x3 = boost::spirit::x3;
  
          typedef std::string::const_iterator iterator_type;
          typedef x3::phrase_parse_context<x3::space_type>::type context_type;
  
      }
  }
  

• literals.cpp:

  #include "literals_def.hpp"
  #include "config.hpp"
  #include <boost/spirit/home/x3.hpp>
  
  namespace kyle { namespace parser { namespace impl {
      BOOST_SPIRIT_INSTANTIATE(identifier_type, iterator_type, context_type);
  } } }
  

• literals_def.hpp:

  #include <boost/spirit/home/x3.hpp>
  #include "literals.hpp"
  
  namespace kyle {
      namespace parser {
          namespace impl {
  
              namespace x3 = boost::spirit::x3;
  
              const identifier_type identifier = "identifier";
              auto const identifier_def = x3::alpha >> *x3::alnum;
  
              BOOST_SPIRIT_DEFINE(identifier)
          }
          impl::identifier_type identifier(){
              return impl::identifier;
          }
      }
  }
  

• literals.hpp:

  #include <boost/spirit/home/x3.hpp>
  
  namespace kyle{
      namespace parser{
          namespace impl {
              namespace x3 = boost::spirit::x3;
  
              struct identifier_class;
  
              typedef x3::rule<identifier_class, std::string> identifier_type;
  
              BOOST_SPIRIT_DECLARE(identifier_type)
          }
  
          impl::identifier_type identifier();
      }
  }
  

• main.cpp:

  #include "literals.hpp"
  #include <iostream>
  
  template<typename Parser>
  bool test(std::string const& str, Parser p, std::string& output, bool full_match = true)
  {
      auto in = str.begin();
      auto end = str.end();
      bool ret = boost::spirit::x3::phrase_parse(in, end, p, boost::spirit::x3::space, output);
      ret &= (!full_match || (in == end));
      return ret;
  }
  
  int main(){
      std::string s;
      auto b = test("fobar", kyle::parser::identifier(), s);
      std::cout << b << ": " << s << std::endl;
  }
  

• CMakeLists.txt:

  ADD_EXECUTABLE(sox3 main.cpp literals.cpp)
  
  SET(CMAKE_CXX_COMPILER g++-5)
  SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -isystem /home/sehe/custom/boost -std=c++14 -O3 -pthread -march=native -flto)