Re: [Boost-users] [numeric_cast] Warning with MSVC

Alexander Lamaison wrote: Sent: Thursday, July 16, 2009 6:09 AM

I'm using boost::numeric_cast to convert the size of a wstring (presumably a size_t) to an int.

const int size = boost::numeric_cast<int>(my_string.size());

MSVC still gives me a warning about possible loss of data:

c:\program files\boost\boost_1_38\boost\numeric\conversion\ cast.hpp(41) : warning C4267: 'argument' : conversion from 'size_t' to 'unsigned int', possible loss of data c:\users\awl03\documents\visual studio 2005\projects\swish_trunk (padd)\swish\utils.hpp(91) : see reference to function template instantiation 'Target boost::numeric_cast(Source)' being compiled with [ Target=int, Source=__w64 unsigned int ] c:\users\awl03\documents\visual studio 2005\projects\swish_trunk (padd)\swish\utils.hpp(121) : see reference to function template instantiation 'std::basic_string<_Elem,_Traits,_Ax> swish::utils::ConvertString<`anonymous-namespace'::Narrow>(const std::basic_string,std:: allocator<_Ty>> &)' being compiled with [ _Elem=char, _Traits=std::char_traits<char>, _Ax=std::allocator<char>, _Ty=wchar_t ]

Unless I misunderstand, isn't the idea of numeric_cast that warnings aren't needed because the casts are checked for loss of data? Any advice is greatly appreaciated.

I am using the MSVC 8.0 compiler with Boost 1.38.0 on 32-bit Windows Vista.

Thanks.

Alex Lamaison

The issue is a compiler option called "detect 64-bit portability issues" or "/Wp64". As it is both non-standard and a rather brutal hack, there is probably no way for Boost to support it. I would recommend turning that option off.