[Boost-bugs] [Boost C++ Libraries] #7929: boost::lexical_cast< std::string, std::wstring > gives a compiler error.

Subject: [Boost-bugs] [Boost C++ Libraries] #7929: boost::lexical_cast< std::string, std::wstring > gives a compiler error.
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-01-26 01:44:35

#7929: boost::lexical_cast< std::string, std::wstring > gives a compiler error.
---------------------------------+------------------------------------------
 Reporter:  nate@…               |       Owner:  apolukhin   
     Type:  Bugs                 |      Status:  new         
Milestone:  To Be Determined     |   Component:  lexical_cast
  Version:  Boost 1.52.0         |    Severity:  Problem     
 Keywords:                       |  
---------------------------------+------------------------------------------
 This causes a problem with `boost::program_options::typed_value<
 std::wstring, wchar_t >::default_value( const std::wstring& v )` which
 attempts to use lexical_cast to convert `v` into a `std::string`. Using
 `lexical_cast` to convert a wide string to a normal one may be debatable,
 but program_options should not give a compiler error on a valid use case
 such as the one shown below. Luckily you can work around this by providing
 an explicit `std::string` version or not using the `default_value` method
 at all.

 ==== lexical_cast error ====
 {{{#!cpp
 #include <boost/lexical_cast.hpp>
 #include <string>

 int main( int argc, wchar_t* argv[] ){
     std::wstring wstr = L"some string";
     std::string str = boost::lexical_cast< std::string >( wstr );

     return 0;
 }
 }}}

 ==== program_options error ====
 {{{#!cpp
 #include <boost/program_options.hpp>
 #include <string>

 int main( int argc, wchar_t* argv[] ){
     namespace po = boost::program_options;
     po::options_description opts( "Some opts" );

     std::wstring str = L"";
     opts.add_options()
         (
             "o",
             po::wvalue< std::wstring >( &str )
                 ->default_value( L"default value" ), // This line causes
 error.
             "an option"
         );

     return 0;
 }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7929>
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