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c++visual-c++boost-spiritboost-spirit-x3

Unintelligible compilation error for a simple X3 grammar

I have a quite simple grammar I try to implement using boost spirit x3, without success.

It does not compile, and due to all the templates and complex concepts used in the library (I know, it is rather a "header"), the compilation error message is way too long to be intelligible.

I tried to comment part of the code in order narrow down the culprit, without success as it comes down to several parts, for which I don't see any error anyway.

Edit2: the first error message is in indeed in push_front_impl.hpp highlighting that:
::REQUESTED_PUSH_FRONT_SPECIALISATION_FOR_SEQUENCE_DOES_NOT_EXIST::*

I suspect the keyword auto or maybe the p2 statement with ulong_long...but with no faith. Need the help of you guys...spirit's elites !

Below a minimal code snippet reproducing the compilation error. Edit: using boost 1.70 and visual studio 2019 v16.1.6

#include <string>
#include <iostream>
#include "boost/spirit/home/x3.hpp"
#include "boost/spirit/include/support_istream_iterator.hpp"

int main(void)
{
       std::string input = \
             "\"nodes\":{ {\"type\":\"bb\", \"id\" : 123456567, \"label\" : \"0x12023049\"}," \
                         "{\"type\":\"bb\", \"id\" : 123123123, \"label\" : \"0x01223234\"}," \
                         "{\"type\":\"ib\", \"id\" : 223092343, \"label\" : \"0x03020343\"}}";
       std::istringstream iss(input);
       namespace x3 = boost::spirit::x3;
       using x3::char_;
       using x3::ulong_long;
       using x3::lit;
 
       auto q = lit('\"'); /* q => quote */
 
       auto p1 = q >> lit("type") >> q >> lit(':') >> q >> (lit("bb") | lit("ib")) >> q;
       auto p2 = q >> lit("id") >> q >> lit(':') >> ulong_long;
       auto p3 = q >> lit("label") >> q >> lit(':') >> q >> (+x3::alpha) >> q;
       auto node =  lit('{') >> p1 >> lit(',') >> p2 >> lit(',') >> p3 >> lit('}');
       auto nodes = q >> lit("nodes") >> q >> lit(':') >> lit('{') >> node % lit(',') >> lit('}');
 
       boost::spirit::istream_iterator f(iss >> std::noskipws), l{};
       bool b = x3::phrase_parse(f, l, nodes, x3::space);
 
       return 0;
}
Solution

  • It is an known MPL limitation (Issue with X3 and MS VS2017, https://github.com/boostorg/spirit/issues/515) + bug/difference of implementation for MSVC/ICC compilers (https://github.com/boostorg/mpl/issues/43).

    I rewrote an offending part without using MPL (https://github.com/boostorg/spirit/pull/607), it will be released in Boost 1.74, until then you should be able to workaround with:

    #define BOOST_MPL_CFG_NO_PREPROCESSED_HEADERS
#define BOOST_MPL_LIMIT_VECTOR_SIZE 50

    Alternatively you could wrap different parts of your grammar into rules, what will reduce sequence parser chain.

    Note that q >> lit("x") >> q >> lit(':') >> ... probably is not what you really want, it (with a skipper) will allow " x ": to be parsed. If you do not want that use simply lit("\"x\"") >> lit(':') >> ...