exagon https://stackoverflow.com/questions/41770375/strange-semantic-behaviour-of-boost-spirit-x3-after-splitting

ast.hpp

#pragma once

#include <vector>
#include <string>
#include <boost/fusion/include/adapt_struct.hpp>



namespace ast{

namespace x3 = boost::spirit::x3;

struct Enum {
    std::string _name;
    std::vector<std::string> _elements;
};


}

BOOST_FUSION_ADAPT_STRUCT(ast::Enum, _name, _elements)

config.hpp

#pragma once 

#include <boost/spirit/home/x3.hpp>

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;

}

enum.cpp

#include "enum_def.hpp"
#include "config.hpp"

namespace parser { namespace impl {
     BOOST_SPIRIT_INSTANTIATE(enum_type, iterator_type, context_type)
}}

namespace parser {

const impl::enum_type& enum_parser()
{
    return impl::enum_parser;
}
    
}

enum.hpp

#pragma once

#include <boost/spirit/home/x3.hpp>
#include "ast.hpp"

namespace parser{ namespace impl{
    namespace x3=boost::spirit::x3;
    
    typedef x3::rule<class enum_class, ast::Enum> enum_type;
    
    BOOST_SPIRIT_DECLARE(enum_type)

}}

namespace parser{
    const impl::enum_type& enum_parser();
}

enum_def.hpp

#pragma once

#include "identifier.hpp"
#include "enum.hpp"
#include "ast.hpp"

namespace parser{ namespace impl{
    
    namespace x3=boost::spirit::x3;
    
    const enum_type enum_parser = "enum";
    
    namespace{
        const auto& identifier = parser::identifier();
    }
    auto const enum_parser_def =
        "enum"
        > identifier
        > "{"
        > identifier % ","
        >"}";

    BOOST_SPIRIT_DEFINE(enum_parser)
}}

enum_parser.hpp

#pragma once

#include "id.hpp"
#include "ast.hpp"

namespace parser {
    
    namespace x3=boost::spirit::x3;

    typedef x3::rule<class enum_class, ast::Enum> enum_type;
    
    const enum_type enum_parser = "enum";

    auto const enum_parser_def =
        "enum"
        > identifier
        > "{"
        > identifier % ","
        >"}";

    BOOST_SPIRIT_DEFINE(enum_parser)
}

id.hpp

#pragma once

#include <boost/spirit/home/x3.hpp>

namespace parser{
    namespace x3=boost::spirit::x3;
    
    typedef x3::rule<class identifier_class, std::string> identifier_type;

    const identifier_type identifier = "identifier";
    
    auto const identifier_def = x3::lexeme[
        ((x3::alpha | '_') >> *(x3::alnum | '_'))
    ];
    
    BOOST_SPIRIT_DEFINE(identifier)
}

identifier.hpp

#pragma once
#include <boost/spirit/home/x3.hpp>

namespace parser{ namespace impl{
    namespace x3=boost::spirit::x3;
    
    typedef x3::rule<class identifier_class, std::string> identifier_type;
    
    BOOST_SPIRIT_DECLARE(identifier_type)
}}


namespace parser{
    const impl::identifier_type& identifier();
}

identifier_def.hpp

#pragma once
#include <boost/spirit/home/x3.hpp>
#include "identifier.hpp"

namespace parser{ namespace impl{
    
    namespace x3=boost::spirit::x3;
    
    const identifier_type identifier = "identifier";    

    auto const identifier_def = x3::lexeme[
        ((x3::alpha | '_') >> *(x3::alnum | '_'))
    ];
    
    BOOST_SPIRIT_DEFINE(identifier)
}}

main.cpp

#include <boost/spirit/home/x3.hpp>
#include "ast.hpp"
#include "enum.hpp"

namespace x3 = boost::spirit::x3;

template<typename Parser, typename Attribute>
bool test(const std::string& str, Parser&& p, Attribute&& attr)
{
    using iterator_type = std::string::const_iterator;
    iterator_type in = str.begin();
    iterator_type end = str.end();

    bool ret = x3::phrase_parse(in, end, p, x3::ascii::space, attr);
    ret &= (in == end);
    return ret;

}

int main(){
    ast::Enum attr;
    test("enum foo{foo,bar}", parser::enum_parser(), attr);
    test("enum {foo,bar}", parser::enum_parser(), attr);    
}

Makefile

all: test

CXX=clang++
CPPFLAGS=-std=c++14 -O2 -Wall -pedantic -march=native
#CPPFLAGS+=-fsanitize=address,undefined
CPPFLAGS+=-I ~/custom/boost

test: main.o identifier.o enum.o
	$(CXX) $(CPPFLAGS) -o $@ $^ $(LDFLAGS)

%.o: %.cpp
	$(CXX) $(CPPFLAGS) $^ -o $@ -c

output.txt

terminate called after throwing an instance of 'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::spirit::x3::expectation_failure<__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > > >'
  what():  boost::spirit::x3::expectation_failure