Boost spirit x3 示例计算器（calc8、calc9）链接器错误

Question

我对提升精神（和提升）非常陌生。它非常有趣的图书馆。

我使用 qtcreator + MinGW 5.3。我只是将 git_hub_calc8 中的每个源文件添加到新项目中并添加了一些 boost 库，但是我在尝试构建时遇到了以下错误（所有其他示例都可以正常工作）

C:\Program Files\boost\boost\boost\spirit\home\x3\nonterminal\rule.hpp:113: ошибка: undefined reference to `bool client::parser::parse_rule<__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >, boost::spirit::x3::context<boost::spirit::x3::error_handler_tag, std::reference_wrapper<boost::spirit::x3::error_handler<__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, boost::spirit::x3::context<boost::spirit::x3::skipper_tag, boost::spirit::x3::char_class<boost::spirit::char_encoding::ascii, boost::spirit::x3::space_tag> const, boost::spirit::x3::unused_type> >, std::__cxx11::list<client::ast::statement, std::allocator<client::ast::statement> > >(boost::spirit::x3::rule<client::parser::statement_class, std::__cxx11::list<client::ast::statement, std::allocator<client::ast::statement> >, false>, __gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&, __gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > const&, boost::spirit::x3::context<boost::spirit::x3::error_handler_tag, std::reference_wrapper<boost::spirit::x3::error_handler<__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >, boost::spirit::x3::context<boost::spirit::x3::skipper_tag, boost::spirit::x3::char_class<boost::spirit::char_encoding::ascii, boost::spirit::x3::space_tag> const, boost::spirit::x3::unused_type> > const&, std::__cxx11::list<client::ast::statement, std::allocator<client::ast::statement> >&)'

我做错了什么？我应该如何使用此示例创建项目？

似乎是 BOOST_SPIRIT_DECLARE 的问题，因为错误指出的地方是调用与此定义相关联的模板函数

(template <typename Iterator, typename Context, typename Attribute_>
        bool parse(Iterator& first, Iterator const& last
          , Context const& context, unused_type, Attribute_& attr) const
        {
            return parse_rule(*this, first, last, context, attr);
        }

Answer 1

BOOST_SPIRIT_INSTANTIATE marco 相当于做

namespace client { namespace parser
{

    template bool parse_rule<iterator_type, context_type, statement_type::attribute_type>(
        statement_type rule_, iterator_type &first, iterator_type const &last,
        context_type const &context,
        statement_type ::attribute_type &attr);
                                                                        ;
}}

所以关键是 iterator_type 和 context_type 匹配完全调用站点所需的那些。现在，未解析的符号是（demangled）：

bool client::parser::parse_rule<
    __gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >,
    boost::spirit::x3::context<
        boost::spirit::x3::error_handler_tag,
        std::reference_wrapper<boost::spirit::x3::error_handler<__gnu_cxx::__normal_iterator<
            char const *, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >,
        boost::spirit::x3::context<
            boost::spirit::x3::skipper_tag,
            boost::spirit::x3::char_class<boost::spirit::char_encoding::ascii, boost::spirit::x3::space_tag> const,
            boost::spirit::x3::unused_type> >,
    std::__cxx11::list<client::ast::statement, std::allocator<client::ast::statement> >
>
(boost::spirit::x3::rule<client::parser::statement_class, std::__cxx11::list<client::ast::statement, std::allocator<client::ast::statement> >, false>,
__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&,
__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > const&,
    boost::spirit::x3::context<
        boost::spirit::x3::error_handler_tag,
        std::reference_wrapper<boost::spirit::x3::error_handler<__gnu_cxx::__normal_iterator<
            char const *, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >,
        boost::spirit::x3::context<
            boost::spirit::x3::skipper_tag,
            boost::spirit::x3::char_class<boost::spirit::char_encoding::ascii, boost::spirit::x3::space_tag> const,
            boost::spirit::x3::unused_type> > const &,
std::__cxx11::list<client::ast::statement, std::allocator<client::ast::statement> >&)

这意味着 iterator_type 应该是：

__gnu_cxx::__normal_iterator<char const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >,

这确实是 std::string::const_iterator 在我的系统上的扩展。因此，上下文类型可能不匹配。通过在 BOOST_SPIRIT_INSTANTIATE 调用上方添加强制类型错误，如下所示：

struct {} _ = *static_cast<client::parser::context_type*>(nullptr);

我能够强制编译器在实例化时输出 context_type 的扩展类型：

statement.cpp:12 error: conversion from ‘client::parser::context_type {aka boost::spirit::x3::context<boost::spirit::x3::error_handler_tag, const std::reference_wrapper<boost::spirit::x3::error_handler<__gnu_cxx::__normal_iterator<const char*, std::__cxx11::basic_string<char> > > >, boost::spirit::x3::context<boost::spirit::x3::skipper_tag, const boost::spirit::x3::char_class<boost::spirit::char_encoding::ascii, boost::spirit::x3::space_tag>, boost::spirit::x3::unused_type> >}’ to non-scalar type ‘client::parser::<anonymous struct>’ requested

这告诉我们上下文类型是（为了易读而格式化）：

boost::spirit::x3::context<
    boost::spirit::x3::error_handler_tag,
    const std::reference_wrapper<boost::spirit::x3::error_handler<
        __gnu_cxx::__normal_iterator<const char *, std::__cxx11::basic_string<char> > > >,
    boost::spirit::x3::context<
        boost::spirit::x3::skipper_tag,
        boost::spirit::x3::char_class<boost::spirit::char_encoding::ascii, boost::spirit::x3::space_tag> const,
        boost::spirit::x3::unused_type> >,

但是：链接器将其设置为

boost::spirit::x3::context<
    boost::spirit::x3::error_handler_tag,
    std::reference_wrapper<boost::spirit::x3::error_handler<
        __gnu_cxx::__normal_iterator<const char *, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > > > >,
    boost::spirit::x3::context<
        boost::spirit::x3::skipper_tag,
        boost::spirit::x3::char_class<boost::spirit::char_encoding::ascii, boost::spirit::x3::space_tag> const,
        boost::spirit::x3::unused_type> >

最显着的区别在于 std::basic_string（char_traits 和 allocator）上默认模板参数的拼写，但这实际上并没有区别。不过，真正重要的区别在于缺少 const 和 reference_wrapper<> 类型。

修复它

我想这可能是 X3 历史上的一次改变。在这种情况下，最简单的解决方法是在 config.hpp:

中删除 const

typedef x3::context<
    error_handler_tag
  , std::reference_wrapper<error_handler_type>
  , phrase_context_type>
context_type;

事实上，它现在可以编译

Boost spirit x3 示例计算器（calc8、calc9）链接器错误

Boost spirit x3 example calculator (calc8, calc9) linker error

boost

linker-errors

boost-spirit

boost-spirit-x3

修复它