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: 2011-10-16 12:20:54

#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@…>):

 Attached a patch that implements C of comment 23.
 This patch should only affect a C++0x mode of gcc-4.4.

 I ported the code in this
 [[http://lists.boost.org/Archives/boost/2011/04/180591.php|post]].
 But, due to `auto&&` bug in gcc-4.4, I needed to change the code for
 adding `const` qualification to rvalue ranges.
 With this patch, `BOOST_FOREACH(DECL, EXPR)` does the following in a C++0x
 mode of gcc-4.4:

 1. Expand EXPR's lifetime
 {{{
 auto && tmp = EXPR
 }}}
 2. Add const if EXPR is rvalue
 {{{
 auto && rng = add_const_if< boost::is_rvalue_reference<decltype( (EXPR)
 )&&> >(tmp)
 }}}
 3. Do the usual range-based for loop over `rng`

 `libs/foreach/test/` ran successfully on gcc (4.3 - 4.6 and 4.7
 (experimental)) and clang (3.1(trunk) and Apple version 2.1) both in C++03
 and C++11 modes.
 I also tested `libs/spirit/test/karma/actions.cpp` on gcc-4.4 in a C++11
 mode
 and it ran fine.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5475#comment:24>
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