我正在尝试实现一个继承自boost：：spirit：：qi：：grammar的类，并使其可在动态库中导出：

#pragma once
#include <impexp.h>
#include <boost/spirit/include/qi.hpp>
#include <boost/spirit/include/phoenix.hpp>

using boost::spirit::ascii::space_type;
struct EXPORT_DLLCLASS Grammar : boost::spirit::qi::grammar< char const*, space_type >
{
   Grammar()
       : Grammar::base_type( expr )
   {
   }
   boost::spirit::qi::rule< char const*, space_type > expr, term;
};

我使用EXPORT_DLLCLASS来指定__attribute__( ( visibility( "default" ) ) )或__declspec( dllexport )，具体取决于平台。在Linux平台下构建成功，但在Windows平台下编译时遇到问题，错误如下：

C:\.conan\oq2odq\1\include\boost/proto/extends.hpp(536,17):  error: call to implicitly-deleted default constructor of 'boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::qi::reference<const boost::spirit::qi::rule<const char *, boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0>, boost::spirit::unused_type, boost::spirit::unused_type, boost::spirit::unused_type> > >, 0>'
              : proto_expr_()
                ^
C:\.conan\oq2odq\1\include\boost/proto/proto_fwd.hpp(377,16):  note: in instantiation of member function 'boost::proto::exprns_::extends<boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::qi::reference<const boost::spirit::qi::rule<const char *, boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0>, boost::spirit::unused_type, boost::spirit::unused_type, boost::spirit::unused_type> > >, 0>, boost::spirit::qi::grammar<const char *, boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0>, boost::spirit::unused_type, boost::spirit::unused_type, boost::spirit::unused_type>, boost::proto::domainns_::default_domain, 0>::extends' requested here
        struct extends;
               ^
C:\.conan\oq2odq\1\include\boost/proto/detail/preprocessed/expr_variadic.hpp(50,49):  note: default constructor of 'expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::qi::reference<const boost::spirit::qi::rule<const char *, boost::proto::exprns_::expr<boost::proto::tagns_::tag::terminal, boost::proto::argsns_::term<boost::spirit::tag::char_code<boost::spirit::tag::space, boost::spirit::char_encoding::ascii> >, 0>, boost::spirit::unused_type, boost::spirit::unused_type, boost::spirit::unused_type> > >, 0>' is implicitly deleted because field 'child0' has no default constructor
        typedef Arg0 proto_child0; proto_child0 child0;

如果未指定EXPORT_DLLCLASS，则构建成功。