Re: [Boost-bugs] [Boost C++ Libraries] #3659: warning when using boost::counting_iterator<int> and std::vector<int> on MSVC

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #3659: warning when using boost::counting_iterator<int> and std::vector<int> on MSVC
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-06-04 11:28:23

#3659: warning when using boost::counting_iterator<int> and std::vector<int> on
MSVC
---------------------------+------------------------------------------------
  Reporter:  anonymous     |       Owner:  dave    
      Type:  Bugs          |      Status:  closed  
 Milestone:  Boost 1.42.0  |   Component:  iterator
   Version:  Boost 1.41.0  |    Severity:  Cosmetic
Resolution:  wontfix       |    Keywords:          
---------------------------+------------------------------------------------

Comment (by Sergey Mitsyn <svm at jinr.ru>):

 The warning still doesn't go when the difference type is explicitly
 specified instead of the default:

 {{{
 #include <boost/iterator/counting_iterator.hpp>
 int main()
 {
         boost::counting_iterator<int, boost::use_default, int> a(0),
 b(10);

         a+=(b-a);

         return 0;
 }
 }}}


 the compiler complains with the following:


 {{{
 boost_1_43_0\boost\iterator\counting_iterator.hpp(139) : warning C4244:
 'return' : conversion from '__int64' to 'int', possible loss of data
 }}}

 IMHO looks like the C-style cast to {{{ numeric_distance }}} forces the
 difference to be intmax_t, and implicit conversion to return type {{{
 Difference }}} invokes the warning.

 Maybe it's OK to assume that if a user specifies the difference type
 explicitly, he/she knows what he/she is doing and use static_cast to {{{
 Difference }}}?

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/3659#comment:2>
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