Re: [Boost-bugs] [Boost C++ Libraries] #5475: [Foreach] rvalue reference binding of temporary ranges

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #5475: [Foreach] rvalue reference binding of temporary ranges
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-10-20 16:34:58

#5475: [Foreach] rvalue reference binding of temporary ranges
--------------------------------------+-------------------------------------
  Reporter:  mimomorin@…              |       Owner:  eric_niebler  
      Type:  Patches                  |      Status:  closed        
 Milestone:  To Be Determined         |   Component:  foreach       
   Version:  Boost Development Trunk  |    Severity:  Problem       
Resolution:  fixed                    |    Keywords:  foreach, C++0x
--------------------------------------+-------------------------------------

Comment (by Michel Morin <mimomorin@…>):

 ***Regressions for compilers supporting C++11 lambda***

 Because the current C++11 BOOST_FOREACH uses `decltype` rather than
 `auto`,
 it cannot be used with C++11 lambda.
 This is possibly a serious regression.
 The following code compiles fine on VC++10 and gcc 4.5-4.7 with Boost
 1.47,
 but fails to compile with Boost trunk:
 {{{
 #include <iostream>
 #include <vector>
 #include <boost/foreach.hpp>
 #define BOOST_RESULT_OF_USE_DECLTYPE
 #include <boost/range/adaptor/transformed.hpp>

 int main (int argc, char* argv[])
 {
     std::vector<int> v(3, 0);

     BOOST_FOREACH(int x, v | boost::adaptors::transformed([](int i){
 return i + 1; }))
     {
         std::cout << x << std::endl;
     }

     return 0;
 }
 }}}
 I know the release branch is already closed,
 but how about deferring C++11 support to Boost 1.49?

 Sorry for repeatedly troubling you.
 I should have noticed this regression earlier and
 I shouldn't have used `decltype` to workaround gcc's `auto` bugs.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5475#comment:31>
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