The following code is a streamlined version of what i’m trying to do. Basically,

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Asked: June 10, 20262026-06-10T01:44:24+00:00 2026-06-10T01:44:24+00:00

The following code is a streamlined version of what i’m trying to do. Basically,

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The following code is a streamlined version of what i’m trying to do. Basically, I have struct (int_holder in the toy code), with a container data member. I want to insert an object (int in this case) and return to the parent qi::rule a pointer to the newly inserted object.

I pass the int_holder to the grammar by reference, in order to fill it with values while parsing, therefore the int_holder will be an inherited attribute of the grammar. Code:

#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix_core.hpp>
#include <boost/spirit/include/phoenix_operator.hpp>
#include <boost/spirit/include/phoenix_function.hpp>
#include <vector>

namespace qi=boost::spirit::qi;
namespace phoenix=boost::phoenix;

struct int_holder
{
    int_holder() {}
    std::vector<int> ints;
};


struct insert_impl
{
    template<class, class>
    struct result { typedef int* type; };
    int* operator() (int_holder& holder, int i) const
    {
        holder.ints.push_back (i);
        return &holder.ints.back();
    }
};

template<class Iterator>
struct my_grammar : qi::grammar<Iterator, int*(int_holder&)>
{
    my_grammar () : my_grammar::base_type (start)
          , insert (insert_impl())
    {
        using qi::_val;
        using qi::int_;
        using qi::_r1;
        using qi::_1;

        using phoenix::ref;

        start = +next(_val) [_val = _1];
        next = int_ [_val = insert(_r1, _1)];
    }
    qi::rule<Iterator, int*(int_holder&)> start, next;
    phoenix::function<insert_impl> insert;
};


int main ()
{
    using phoenix::ref;

    const char* p="1";
    int* last;
    int_holder holder;
    my_grammar<const char*> g;
    qi::parse (p, p+1, g(ref(holder)), last);
}

The code does not compile, with the following error message:

In file included from     
/opt/local/include/boost/fusion/sequence/intrinsic/detail/segmented_begin.hpp:16:0,
         from /opt/local/include/boost/fusion/sequence/intrinsic/begin.hpp:17, from
         /opt/local/include/boost/fusion/iterator/segmented_iterator.hpp:12, from
         /opt/local/include/boost/fusion/sequence/intrinsic/detail/segmented_end.hpp:11, from
         /opt/local/include/boost/fusion/sequence/intrinsic/end.hpp:17, from
         /opt/local/include/boost/fusion/sequence/intrinsic/back.hpp:11, from
         /opt/local/include/boost/fusion/sequence/intrinsic.hpp:11, from
         /opt/local/include/boost/fusion/include/intrinsic.hpp:10, from
         /opt/local/include/boost/proto/fusion.hpp:22, from
         /opt/local/include/boost/proto/core.hpp:21, from
         /opt/local/include/boost/proto/proto.hpp:12, from
         /opt/local/include/boost/spirit/home/support/meta_compiler.hpp:19, from
         /opt/local/include/boost/spirit/home/qi/meta_compiler.hpp:14, from
         /opt/local/include/boost/spirit/home/qi/action/action.hpp:14, from
         /opt/local/include/boost/spirit/home/qi/action.hpp:14, from
         /opt/local/include/boost/spirit/home/qi.hpp:14, from
         /opt/local/include/boost/spirit/include/qi.hpp:16, from test_qi.cpp:1:
         /opt/local/include/boost/fusion/container/list/cons.hpp: In instantiation of
         'boost::fusion::cons<Car, Cdr>::cons(const boost::fusion::cons<Car2, Cdr2>&) [with Car2 =
         int*&; Cdr2 = boost::fusion::nil; Car = int_holder&; Cdr = boost::fusion::nil]':
         /opt/local/include/boost/spirit/home/support/context.hpp:117:20: required from
         'boost::spirit::context<Attributes, Locals>::context(typename Attributes::car_type, const
         Args&, Context&) [with Args =
         boost::fusion::vector<boost::phoenix::actor<boost::spirit::attribute<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_,
         boost::fusion::void_>; Context = boost::spirit::context<boost::fusion::cons<int*&,
         boost::fusion::cons<int_holder&, boost::fusion::nil> >, boost::fusion::vector0<> >;
         Attributes = boost::fusion::cons<int*&, boost::fusion::cons<int_holder&,
         boost::fusion::nil> >; Locals = boost::fusion::vector0<>; typename Attributes::car_type =
         int*&]' /opt/local/include/boost/spirit/home/qi/nonterminal/rule.hpp:343:67: required
         from 'bool boost::spirit::qi::rule<Iterator, T1, T2, T3, T4>::parse(Iterator&, const
         Iterator&, Context&, const Skipper&, Attribute&, const Params&) const [with Context =
         boost::spirit::context<boost::fusion::cons<int*&, boost::fusion::cons<int_holder&,
         boost::fusion::nil> >, boost::fusion::vector0<> >; Skipper = boost::spirit::unused_type;
         Attribute = int*; Params =
         boost::fusion::vector<boost::phoenix::actor<boost::spirit::attribute<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_,
         boost::fusion::void_>; Iterator = const char*; T1 = int*(int_holder&); T2 =
         boost::spirit::unused_type; T3 = boost::spirit::unused_type; T4 =
         boost::spirit::unused_type]'
         /opt/local/include/boost/spirit/home/qi/nonterminal/detail/parameterized.hpp:48:79:
         required from 'bool boost::spirit::qi::parameterized_nonterminal<Subject,
         Params>::parse(Iterator&, const Iterator&, Context&, const Skipper&, Attribute&) const
         [with Iterator = const char*; Context = boost::spirit::context<boost::fusion::cons<int*&,
         boost::fusion::cons<int_holder&, boost::fusion::nil> >, boost::fusion::vector0<> >;
         Skipper = boost::spirit::unused_type; Attribute = int*; Subject =
         boost::spirit::qi::rule<const char*, int*(int_holder&), boost::spirit::unused_type,
         boost::spirit::unused_type, boost::spirit::unused_type>; Params =
         boost::fusion::vector<boost::phoenix::actor<boost::spirit::attribute<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_,
         boost::fusion::void_>]' /opt/local/include/boost/spirit/home/qi/action/action.hpp:65:13:
         required from 'bool boost::spirit::qi::action<Subject, Action>::parse(Iterator&, const
         Iterator&, Context&, const Skipper&, Attribute&) const [with Iterator = const char*;
         Context = boost::spirit::context<boost::fusion::cons<int*&,
         boost::fusion::cons<int_holder&, boost::fusion::nil> >, boost::fusion::vector0<> >;
         Skipper = boost::spirit::unused_type; Attribute = boost::spirit::unused_type; Subject =
         boost::spirit::qi::parameterized_nonterminal<boost::spirit::qi::rule<const char*,
         int*(int_holder&), boost::spirit::unused_type, boost::spirit::unused_type,
         boost::spirit::unused_type>,
         boost::fusion::vector<boost::phoenix::actor<boost::spirit::attribute<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_,
         boost::fusion::void_> >; Action =
         boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::assign_eval,
         boost::fusion::vector<boost::spirit::attribute<0>, 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_> >
         >]' /opt/local/include/boost/spirit/home/qi/detail/fail_function.hpp:38:72: required from
         'bool boost::spirit::qi::detail::fail_function<Iterator, Context,
         Skipper>::operator()(const Component&, Attribute&) const [with Component =
         boost::spirit::qi::action<boost::spirit::qi::parameterized_nonterminal<boost::spirit::qi::rule<const
         char*, int*(int_holder&), boost::spirit::unused_type, boost::spirit::unused_type,
         boost::spirit::unused_type>,
         boost::fusion::vector<boost::phoenix::actor<boost::spirit::attribute<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_,
         boost::fusion::void_> >,
         boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::assign_eval,
         boost::fusion::vector<boost::spirit::attribute<0>, 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_> >
         > >; Attribute = boost::spirit::unused_type; Iterator = const char*; Context =
         boost::spirit::context<boost::fusion::cons<int*&, boost::fusion::cons<int_holder&,
         boost::fusion::nil> >, boost::fusion::vector0<> >; Skipper = boost::spirit::unused_type]'
         /opt/local/include/boost/spirit/home/qi/detail/pass_container.hpp:263:38: [ skipping 10
         instantiation contexts ] /opt/local/include/boost/function/function_template.hpp:1042:16:
         required from 'boost::function<R(T0, T1, T2, T3)>::function(Functor, typename
         boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value,
         int>::type) [with Functor =
         boost::spirit::qi::detail::parser_binder<boost::spirit::qi::plus<boost::spirit::qi::action<boost::spirit::qi::parameterized_nonterminal<boost::spirit::qi::rule<const
         char*, int*(int_holder&), boost::spirit::unused_type, boost::spirit::unused_type,
         boost::spirit::unused_type>,
         boost::fusion::vector<boost::phoenix::actor<boost::spirit::attribute<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_,
         boost::fusion::void_> >,
         boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::assign_eval,
         boost::fusion::vector<boost::spirit::attribute<0>, 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_> >
         > > >, mpl_::bool_<false> >; R = bool; T0 = const char*&; T1 = const char* const&; T2 =
         boost::spirit::context<boost::fusion::cons<int*&, boost::fusion::cons<int_holder&,
         boost::fusion::nil> >, boost::fusion::vector0<> >&; T3 = const
         boost::spirit::unused_type&; typename
         boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value,
         int>::type = int]' /opt/local/include/boost/function/function_template.hpp:1083:5:
         required from 'typename
         boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value,
         boost::function<R(T0, T1, T2, T3)>&>::type boost::function<R(T0, T1, T2,
         T3)>::operator=(Functor) [with Functor =
         boost::spirit::qi::detail::parser_binder<boost::spirit::qi::plus<boost::spirit::qi::action<boost::spirit::qi::parameterized_nonterminal<boost::spirit::qi::rule<const
         char*, int*(int_holder&), boost::spirit::unused_type, boost::spirit::unused_type,
         boost::spirit::unused_type>,
         boost::fusion::vector<boost::phoenix::actor<boost::spirit::attribute<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_,
         boost::fusion::void_> >,
         boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::assign_eval,
         boost::fusion::vector<boost::spirit::attribute<0>, 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_> >
         > > >, mpl_::bool_<false> >; R = bool; T0 = const char*&; T1 = const char* const&; T2 =
         boost::spirit::context<boost::fusion::cons<int*&, boost::fusion::cons<int_holder&,
         boost::fusion::nil> >, boost::fusion::vector0<> >&; T3 = const
         boost::spirit::unused_type&; typename
         boost::enable_if_c<boost::type_traits::ice_not<boost::is_integral<Functor>::value>::value,
         boost::function<R(T0, T1, T2, T3)>&>::type = boost::function<bool(const char*&, const
         char* const&, boost::spirit::context<boost::fusion::cons<int*&,
         boost::fusion::cons<int_holder&, boost::fusion::nil> >, boost::fusion::vector0<> >&,
         const boost::spirit::unused_type&)>&]'
         /opt/local/include/boost/spirit/home/qi/nonterminal/rule.hpp:182:13: required from
         'static void boost::spirit::qi::rule<Iterator, T1, T2, T3,
         T4>::define(boost::spirit::qi::rule<Iterator, T1, T2, T3, T4>&, const Expr&, mpl_::true_)
         [with Auto = mpl_::bool_<false>; Expr =
         boost::proto::exprns_::expr<boost::proto::tagns_::tag::unary_plus,
         boost::proto::argsns_::list1<const
         boost::proto::exprns_::expr<boost::proto::tagns_::tag::subscript,
         boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
         boost::proto::argsns_::term<boost::spirit::qi::parameterized_nonterminal<boost::spirit::qi::rule<const
         char*, int*(int_holder&), boost::spirit::unused_type, boost::spirit::unused_type,
         boost::spirit::unused_type>,
         boost::fusion::vector<boost::phoenix::actor<boost::spirit::attribute<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_,
         boost::fusion::void_> > >, 0l>&,
         boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
         boost::proto::argsns_::term<const
         boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::assign_eval,
         boost::fusion::vector<boost::spirit::attribute<0>, 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_> >
         >&>, 0l> >, 2l>&>, 1l>; Iterator = const char*; T1 = int*(int_holder&); T2 =
         boost::spirit::unused_type; T3 = boost::spirit::unused_type; T4 =
         boost::spirit::unused_type; boost::spirit::qi::rule<Iterator, T1, T2, T3, T4> =
         boost::spirit::qi::rule<const char*, int*(int_holder&), boost::spirit::unused_type,
         boost::spirit::unused_type, boost::spirit::unused_type>; mpl_::true_ =
         mpl_::bool_<true>]' /opt/local/include/boost/spirit/home/qi/nonterminal/rule.hpp:220:13:
         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::unary_plus,
         boost::proto::argsns_::list1<const
         boost::proto::exprns_::expr<boost::proto::tagns_::tag::subscript,
         boost::proto::argsns_::list2<boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
         boost::proto::argsns_::term<boost::spirit::qi::parameterized_nonterminal<boost::spirit::qi::rule<const
         char*, int*(int_holder&), boost::spirit::unused_type, boost::spirit::unused_type,
         boost::spirit::unused_type>,
         boost::fusion::vector<boost::phoenix::actor<boost::spirit::attribute<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_,
         boost::fusion::void_> > >, 0l>&,
         boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal,
         boost::proto::argsns_::term<const
         boost::phoenix::actor<boost::phoenix::composite<boost::phoenix::assign_eval,
         boost::fusion::vector<boost::spirit::attribute<0>, 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_> >
         >&>, 0l> >, 2l>&>, 1l>; Iterator = const char*; T1 = int*(int_holder&); T2 =
         boost::spirit::unused_type; T3 = boost::spirit::unused_type; T4 =
         boost::spirit::unused_type; boost::spirit::qi::rule<Iterator, T1, T2, T3, T4> =
         boost::spirit::qi::rule<const char*, int*(int_holder&), boost::spirit::unused_type,
         boost::spirit::unused_type, boost::spirit::unused_type>]' test_qi.cpp:41:3: required from
         'my_grammar<Iterator>::my_grammar() [with Iterator = const char*]' test_qi.cpp:57:26:
         required from here /opt/local/include/boost/fusion/container/list/cons.hpp:83:40: error:
         invalid initialization of reference of type 'boost::fusion::cons<int_holder&,
         boost::fusion::nil>::car_type {aka int_holder&}' from expression of type 'int*'

There is obviously a problem when passing _r1 to the phoenix::function, but I have no idea how to solve it. Thanks in advance.

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1 Answer

Editorial Team · Answer 1 · 2026-06-10T01:44:25+00:00

Editorial Team

2026-06-10T01:44:25+00:00Added an answer on June 10, 2026 at 1:44 am

Sorry, I have just discovered the error, the line of code

start = +next(_val) [_val = _1];

needed to be changed to

start = +next(_r1) [_val = _1];

and then it works. Sorry for wasting you time! Bye!

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The following code is a streamlined version of what i’m trying to do. Basically,

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