Re: [Boost-bugs] [Boost C++ Libraries] #287: wrong usage of ios_base::narrow

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #287: wrong usage of ios_base::narrow
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-05-29 18:27:52

#287: wrong usage of ios_base::narrow
---------------------------+------------------------------------------------
  Reporter:  vandrejev     |       Owner:  az_sw_dude
      Type:  Bugs          |      Status:  assigned  
 Milestone:  Boost 1.40.0  |   Component:  date_time 
   Version:  None          |    Severity:  Problem   
Resolution:  None          |    Keywords:            
---------------------------+------------------------------------------------
Changes (by marshall):

  * severity:  => Problem
  * milestone:  => Boost 1.40.0


Old description:

> {{{
> /cvsroot/boost/boost/boost/date_time/date_parsing.hpp
> revision 1.18, lines 207, 214
>
> std::stringstream has char_type typedef evidently equal
> to char, not wchar_t, so in std::stringstream::narrow
> function the first argument has type char and in the call
>
> ss << ss.narrow(*beg++, 'X');
>
> *beg will be converted from wchar_t to char before call
> to narrow will be made.
>
> I suggest the following patch:
>
> diff -c -r1.18 date_parsing.hpp
> ***************
> *** 207,214 ****
>                                  wchar_t)
>       {
>         std::stringstream ss("");
>         while(beg != end) {
> !         ss << ss.narrow(*beg++, 'X'); // 'X' will cause
> exception to be thrown
>         }
>         return parse_date<date_type>(ss.str());
>       }
> --- 207,215 ----
>                                  wchar_t)
>       {
>         std::stringstream ss("");
> +       std::locale loc;
>         while(beg != end) {
> !         ss << std::use_facet<std::ctype<wchar_t> >
> (loc).narrow(*beg++, 'X');
>         }
>         return parse_date<date_type>(ss.str());
>       }
>
> }}}

New description:

 {{{
 /cvsroot/boost/boost/boost/date_time/date_parsing.hpp
 revision 1.18, lines 207, 214

 std::stringstream has char_type typedef evidently equal
 to char, not wchar_t, so in std::stringstream::narrow
 function the first argument has type char and in the call

 ss << ss.narrow(*beg++, 'X');

 *beg will be converted from wchar_t to char before call
 to narrow will be made.

 I suggest the following patch:

 diff -c -r1.18 date_parsing.hpp
 ***************
 *** 207,214 ****
                                  wchar_t)
       {
         std::stringstream ss("");
         while(beg != end) {
 !         ss << ss.narrow(*beg++, 'X'); // 'X' will cause
 exception to be thrown
         }
         return parse_date<date_type>(ss.str());
       }
 --- 207,215 ----
                                  wchar_t)
       {
         std::stringstream ss("");
 +       std::locale loc;
         while(beg != end) {
 !         ss << std::use_facet<std::ctype<wchar_t> >
 (loc).narrow(*beg++, 'X');
         }
         return parse_date<date_type>(ss.str());
       }

 }}}

--
Comment:
 Marshall sez: looking at the code in trunk, it appears that this patch has
 been (more or less) applied.
 I'm not sure about the constructor call to std:locale() for each
 character, though.
 {{
       while(beg != end) {
 #if !defined(BOOST_DATE_TIME_NO_LOCALE)
         ss << std::use_facet<std::ctype<wchar_t>
 >(std::locale()).narrow(*beg++, 'X'); // 'X' will cause exception to be
 thrown
 #else
         ss << ss.narrow(*beg++, 'X');
 #endif
       }
 }}
-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/287#comment:1>
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