boost :: phoenix try_ catch_all构造无法编译

Question

我正在为日期解析编写boost :: spirit :: qi语法。

#include <boost/spirit/include/qi.hpp> 
#include <boost/spirit/include/phoenix.hpp> 
#include <boost/date_time.hpp> 

template < typename InputIterator > 
struct date_rfc1123_grammar : 
      boost::spirit::qi::grammar< InputIterator, boost::gregorian::date()> { 
    typedef boost::gregorian::date value_type; 
    date_rfc1123_grammar() : date_rfc1123_grammar::base_type(date) 
    { 
     namespace qi = boost::spirit::qi; 
     namespace phx = boost::phoenix; 
     using qi::_pass; 
     using qi::_val; 
     using qi::_2; 
     using qi::_3; 
     using qi::_4; 

     _2digits = qi::uint_parser< std::uint32_t, 10, 2, 2 >(); 
     _4digits = qi::uint_parser< std::uint32_t, 10, 4, 4 >(); 
     date = (weekday >> ' ' >> _2digits >> ' ' >> month >> ' ' >> _4digits) 
      [ 
       phx::try_[ 
       _val = phx::construct<value_type>(_4, _3, _2) 
       ].catch_all[ 
       _pass = false 
       ] 
      ]; 
    } 
    boost::spirit::qi::rule< InputIterator, value_type()> date; 
    weekday_grammar weekday; 
    month_grammar month; 
    boost::spirit::qi::rule< InputIterator, std::int32_t() > _2digits; 
    boost::spirit::qi::rule< InputIterator, std::int32_t() > _4digits; 
}; 

我依靠boost::gregorian::date构造函数的参数检查，并希望解析器在异常情况下失败。但boost::phoenix::try_[ ].catch_all[ ]构建失败，出现以下消息编译：

/path_to_file/datetime_parse.hpp:102:8: required from ‘tip::http::grammar::parse::date_rfc1123_grammar<InputIterator>::date_rfc1123_grammar() [with InputIterator = boost::spirit::multi_pass<std::istreambuf_iterator<char, std::char_traits<char> > >]’ 
/path_to_file/grammar_parse_test.hpp:17:7: required from here 
/usr/local/include/boost/proto/traits.hpp:341:13: error: static assertion failed: 0 == Expr::proto_arity_c 
      BOOST_STATIC_ASSERT(0 == Expr::proto_arity_c); 
      ^

没有try_.catch_all构建语法编译OK，但我想分析器捕获异常，并设置_pass标志设置为false，使语法失败。

操作系统和编译器的信息：

$ uname -a 
Linux zmij 3.19.0-27-generiC#29-Ubuntu SMP Fri Aug 14 21:43:37 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux 
$ g++ -v 
Thread model: posix 
gcc version 4.9.2 (Ubuntu 4.9.2-10ubuntu13) 

增压版本1.58

Answer 1

我以前见过这个，可能是当地某些升压/编译器版本。

一种解决方法将包括使其成为一个序列的无操作语句（如_pass=_pass）：

date = (weekday >> ' ' >> _2digits >> ' ' >> month >> ' ' >> _4digits) 
     [ 
      _pass = _pass, 
      phx::try_[ 
      _val = phx::construct<value_type>(_4, _3, _2) 
      ].catch_all[ 
      _pass = false 
      ] 
     ]; 

看到它Live On Coliru

#include <boost/spirit/include/qi.hpp> 
#include <boost/spirit/include/phoenix.hpp> 
#include <boost/date_time/gregorian/greg_date.hpp> 

template <typename InputIterator> 
struct date_rfc1123_grammar : boost::spirit::qi::grammar< InputIterator, boost::gregorian::date()> 
{ 
    typedef boost::gregorian::date value_type; 
    date_rfc1123_grammar() : date_rfc1123_grammar::base_type(date) 
    { 
     namespace qi = boost::spirit::qi; 
     namespace phx = boost::phoenix; 
     using qi::_pass; 
     using qi::_val; 
     using qi::_2; 
     using qi::_3; 
     using qi::_4; 

     date = (weekday >> ' ' >> _2digits >> ' ' >> month >> ' ' >> _4digits) 
      [ 
       _pass = _pass, 
       phx::try_[ 
       _val = phx::construct<value_type>(_4, _3, _2) 
       ].catch_all[ 
       _pass = false 
       ] 
      ]; 
    } 
    boost::spirit::qi::rule< InputIterator, value_type()> date; 
    boost::spirit::qi::rule< InputIterator, uint()> weekday, month; 
    boost::spirit::qi::uint_parser< std::uint32_t, 10, 2, 2 > _2digits; 
    boost::spirit::qi::uint_parser< std::uint32_t, 10, 4, 4 > _4digits; 
}; 

int main() { 
    using It = std::string::const_iterator; 
    std::string const input; 

    date_rfc1123_grammar<It> g; 

    It f = input.begin(), l = input.end(); 

    boost::gregorian::date d; 
    bool ok = boost::spirit::qi::parse(f, l, g, d); 

    return ok?1:2; 
}