c++ - 使用 boost::spirit::x3 编译错误

Question

我尝试编译 example file使用 gcc 5.3.1 (5.3.1 20160406 (Red Hat 5.3.1-6) (GCC))，boost 1.61.0。

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

#include <iostream>

// Presented are various ways to attach semantic actions
//  * Using plain function pointer
//  * Using simple function object

namespace client
{
    namespace x3 = boost::spirit::x3;
    using x3::_attr;

    struct print_action
    {    
        template <typename Context>
        void operator()(Context const& ctx) const
        {
            std::cout << _attr(ctx) << std::endl;
        }
    };
}

int main()
{
    using boost::spirit::x3::int_;
    using boost::spirit::x3::parse;
    using client::print_action;

    { // example using function object

        char const *first = "{43}", *last = first + std::strlen(first);
        parse(first, last, '{' >> int_[print_action()] >> '}');
    }

    { // example using C++14 lambda

        char const *first = "{44}", *last = first + std::strlen(first);
        auto f = [](auto& ctx){ std::cout << _attr(ctx) << std::endl; };
        parse(first, last, '{' >> int_[f] >> '}');
    }

    return 0;
}

编译命令为:g++ test.cpp -std=c++1y(我只是重命名了文件。)

我收到以下错误:

test.cpp: In instantiation of ‘main()::<lambda(auto:1&)> [with auto:1 = const boost::spirit::x3::context<boost::spirit::x3::attr_context_tag, int, boost::spirit::x3::context<boost::spirit::x3::where_context_tag, boost::iterator_range<const char*>, boost::spirit::x3::context<boost::spirit::x3::rule_val_context_tag, const boost::spirit::x3::unused_type, boost::spirit::x3::context<boost::spirit::x3::parse_pass_context_tag, bool, boost::spirit::x3::unused_type> > > >]’:
/usr/local/include/boost/spirit/home/x3/support/utility/is_callable.hpp:20:35:   required from ‘struct boost::spirit::x3::is_callable<main()::<lambda(auto:1&)>(const boost::spirit::x3::context<boost::spirit::x3::attr_context_tag, int, boost::spirit::x3::context<boost::spirit::x3::where_context_tag, boost::iterator_range<const char*>, boost::spirit::x3::context<boost::spirit::x3::rule_val_context_tag, const boost::spirit::x3::unused_type, boost::spirit::x3::context<boost::spirit::x3::parse_pass_context_tag, bool, boost::spirit::x3::unused_type> > > >&)>’
/usr/local/include/boost/spirit/home/x3/core/call.hpp:72:28:   required from ‘auto boost::spirit::x3::call(F, Iterator&, const Iterator&, const Context&, RuleContext&, Attribute&) [with F = main()::<lambda(auto:1&)>; Iterator = const char*; Context = boost::spirit::x3::context<boost::spirit::x3::parse_pass_context_tag, bool, boost::spirit::x3::unused_type>; RuleContext = const boost::spirit::x3::unused_type; Attribute = int]’
/usr/local/include/boost/spirit/home/x3/core/action.hpp:45:17:   required from ‘bool boost::spirit::x3::action<Subject, Action>::call_action(Iterator&, const Iterator&, const Context&, RuleContext&, Attribute&) const [with Iterator = const char*; Context = boost::spirit::x3::unused_type; RuleContext = const boost::spirit::x3::unused_type; Attribute = int; Subject = boost::spirit::x3::int_parser<int>; Action = main()::<lambda(auto:1&)>]’
/usr/local/include/boost/spirit/home/x3/core/action.hpp:57:32:   required from ‘bool boost::spirit::x3::action<Subject, Action>::parse_main(Iterator&, const Iterator&, const Context&, RuleContext&, Attribute&) const [with Iterator = const char*; Context = boost::spirit::x3::unused_type; RuleContext = const boost::spirit::x3::unused_type; Attribute = int; Subject = boost::spirit::x3::int_parser<int>; Action = main()::<lambda(auto:1&)>]’
/usr/local/include/boost/spirit/home/x3/operator/sequence.hpp:32:17:   recursively required from ‘bool boost::spirit::x3::sequence<Left, Right>::parse(Iterator&, const Iterator&, const Context&, RContext&, boost::spirit::x3::unused_type) const [with Iterator = const char*; Context = boost::spirit::x3::unused_type; RContext = const boost::spirit::x3::unused_type; Left = boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>; Right = boost::spirit::x3::action<boost::spirit::x3::int_parser<int>, main()::<lambda(auto:1&)> >]’
/usr/local/include/boost/spirit/home/x3/operator/sequence.hpp:32:17:   required from ‘bool boost::spirit::x3::sequence<Left, Right>::parse(Iterator&, const Iterator&, const Context&, RContext&, boost::spirit::x3::unused_type) const [with Iterator = const char*; Context = boost::spirit::x3::unused_type; RContext = const boost::spirit::x3::unused_type; Left = boost::spirit::x3::sequence<boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>, boost::spirit::x3::action<boost::spirit::x3::int_parser<int>, main()::<lambda(auto:1&)> > >; Right = boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>]’
/usr/local/include/boost/spirit/home/x3/core/parse.hpp:35:68:   required from ‘bool boost::spirit::x3::parse_main(Iterator&, Iterator, const Parser&, Attribute&) [with Iterator = const char*; Parser = boost::spirit::x3::sequence<boost::spirit::x3::sequence<boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>, boost::spirit::x3::action<boost::spirit::x3::int_parser<int>, main()::<lambda(auto:1&)> > >, boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type> >; Attribute = const boost::spirit::x3::unused_type]’
/usr/local/include/boost/spirit/home/x3/core/parse.hpp:71:26:   required from ‘bool boost::spirit::x3::parse(Iterator&, Iterator, const Parser&) [with Iterator = const char*; Parser = boost::spirit::x3::sequence<boost::spirit::x3::sequence<boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>, boost::spirit::x3::action<boost::spirit::x3::int_parser<int>, main()::<lambda(auto:1&)> > >, boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type> >]’
test.cpp:47:49:   required from here
test.cpp:46:51: 错误：use of ‘template<class Context> decltype(auto) boost::spirit::x3::_attr(const Context&)’ before deduction of ‘auto’
         auto f = [](auto& ctx){ std::cout << _attr(ctx) << std::endl; };
                                                   ^
test.cpp:46:51: 错误：use of ‘decltype(auto) boost::spirit::x3::_attr(const Context&) [with Context = boost::spirit::x3::context<boost::spirit::x3::attr_context_tag, int, boost::spirit::x3::context<boost::spirit::x3::where_context_tag, boost::iterator_range<const char*>, boost::spirit::x3::context<boost::spirit::x3::rule_val_context_tag, const boost::spirit::x3::unused_type, boost::spirit::x3::context<boost::spirit::x3::parse_pass_context_tag, bool, boost::spirit::x3::unused_type> > > >]’ before deduction of ‘auto’
In file included from /usr/local/include/boost/spirit/home/x3/core/action.hpp:13:0,
                 from /usr/local/include/boost/spirit/home/x3/core.hpp:14,
                 from /usr/local/include/boost/spirit/home/x3.hpp:20,
                 from test.cpp:8:
/usr/local/include/boost/spirit/home/x3/core/call.hpp: In instantiation of ‘auto boost::spirit::x3::call(F, Iterator&, const Iterator&, const Context&, RuleContext&, Attribute&) [with F = main()::<lambda(auto:1&)>; Iterator = const char*; Context = boost::spirit::x3::context<boost::spirit::x3::parse_pass_context_tag, bool, boost::spirit::x3::unused_type>; RuleContext = const boost::spirit::x3::unused_type; Attribute = int]’:
/usr/local/include/boost/spirit/home/x3/core/action.hpp:45:17:   required from ‘bool boost::spirit::x3::action<Subject, Action>::call_action(Iterator&, const Iterator&, const Context&, RuleContext&, Attribute&) const [with Iterator = const char*; Context = boost::spirit::x3::unused_type; RuleContext = const boost::spirit::x3::unused_type; Attribute = int; Subject = boost::spirit::x3::int_parser<int>; Action = main()::<lambda(auto:1&)>]’
/usr/local/include/boost/spirit/home/x3/core/action.hpp:57:32:   required from ‘bool boost::spirit::x3::action<Subject, Action>::parse_main(Iterator&, const Iterator&, const Context&, RuleContext&, Attribute&) const [with Iterator = const char*; Context = boost::spirit::x3::unused_type; RuleContext = const boost::spirit::x3::unused_type; Attribute = int; Subject = boost::spirit::x3::int_parser<int>; Action = main()::<lambda(auto:1&)>]’
/usr/local/include/boost/spirit/home/x3/operator/sequence.hpp:32:17:   recursively required from ‘bool boost::spirit::x3::sequence<Left, Right>::parse(Iterator&, const Iterator&, const Context&, RContext&, boost::spirit::x3::unused_type) const [with Iterator = const char*; Context = boost::spirit::x3::unused_type; RContext = const boost::spirit::x3::unused_type; Left = boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>; Right = boost::spirit::x3::action<boost::spirit::x3::int_parser<int>, main()::<lambda(auto:1&)> >]’
/usr/local/include/boost/spirit/home/x3/operator/sequence.hpp:32:17:   required from ‘bool boost::spirit::x3::sequence<Left, Right>::parse(Iterator&, const Iterator&, const Context&, RContext&, boost::spirit::x3::unused_type) const [with Iterator = const char*; Context = boost::spirit::x3::unused_type; RContext = const boost::spirit::x3::unused_type; Left = boost::spirit::x3::sequence<boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>, boost::spirit::x3::action<boost::spirit::x3::int_parser<int>, main()::<lambda(auto:1&)> > >; Right = boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>]’
/usr/local/include/boost/spirit/home/x3/core/parse.hpp:35:68:   required from ‘bool boost::spirit::x3::parse_main(Iterator&, Iterator, const Parser&, Attribute&) [with Iterator = const char*; Parser = boost::spirit::x3::sequence<boost::spirit::x3::sequence<boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>, boost::spirit::x3::action<boost::spirit::x3::int_parser<int>, main()::<lambda(auto:1&)> > >, boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type> >; Attribute = const boost::spirit::x3::unused_type]’
/usr/local/include/boost/spirit/home/x3/core/parse.hpp:71:26:   required from ‘bool boost::spirit::x3::parse(Iterator&, Iterator, const Parser&) [with Iterator = const char*; Parser = boost::spirit::x3::sequence<boost::spirit::x3::sequence<boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type>, boost::spirit::x3::action<boost::spirit::x3::int_parser<int>, main()::<lambda(auto:1&)> > >, boost::spirit::x3::literal_char<boost::spirit::char_encoding::standard, boost::spirit::x3::unused_type> >]’
test.cpp:47:49:   required from here
/usr/local/include/boost/spirit/home/x3/core/call.hpp:72:28: 错误：use of ‘auto boost::spirit::x3::detail::call(F, const Context&, mpl_::true_) [with F = main()::<lambda(auto:1&)>; Context = boost::spirit::x3::context<boost::spirit::x3::attr_context_tag, int, boost::spirit::x3::context<boost::spirit::x3::where_context_tag, boost::iterator_range<const char*>, boost::spirit::x3::context<boost::spirit::x3::rule_val_context_tag, const boost::spirit::x3::unused_type, boost::spirit::x3::context<boost::spirit::x3::parse_pass_context_tag, bool, boost::spirit::x3::unused_type> > > >; mpl_::true_ = mpl_::bool_<true>]’ before deduction of ‘auto’
         return detail::call(f, attr_context, is_callable<F(decltype(attr_context) const&)>());
                            ^

我想知道是什么导致了这个错误？

P.S: 在文件中，错是Error的意思。

Answer 1

Note It looks like you linked the wrong sample file. My answer responds to the code shown in the error message instead.

我无法重现问题，但我记得曾经见过类似的问题。

似乎 GCC 有时在为多态 lambda 参数类型执行 ADL 时遇到问题。

我绕过它的方法是禁用那里的 ADL:

auto f = [](auto& ctx){ std::cout << x3::_attr(ctx) << std::endl; };

或:

auto f = [](auto& ctx){ std::cout << (_attr)(ctx) << std::endl; };