[Boost-bugs] [Boost C++ Libraries] #7892: boost.atomic misbehaves with Apple clang version 4.1 and -O2

Subject: [Boost-bugs] [Boost C++ Libraries] #7892: boost.atomic misbehaves with Apple clang version 4.1 and -O2
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-01-14 21:19:36

#7892: boost.atomic misbehaves with Apple clang version 4.1 and -O2
--------------------------------------------------------+-------------------
 Reporter:  Andreas Beisler <ebfx@…>                    |       Owner:  timblechmann
     Type:  Bugs                                        |      Status:  new         
Milestone:  To Be Determined                            |   Component:  atomic      
  Version:  Boost Release Branch                        |    Severity:  Problem     
 Keywords:                                              |  
--------------------------------------------------------+-------------------
 There seems to be an issue, when assigning to an atomic in a "while
 (true)" loop (without break statement!).

 {{{
 #include <boost/atomic.hpp>

 void this_works()
 {
     boost::atomic_bool b(false);
     std::cout << b << std::endl; // 0
     b = true;
     std::cout << b << std::endl; // 1
 }

 void this_works_too()
 {
     boost::atomic_bool b(false);
     while (true)
     {
         std::cout << b << std::endl; // 0
         b = true;
         std::cout << b << std::endl; // 1
         break;
     }
 }

 void this_doesnt_work()
 {
     boost::atomic_bool b(false);
     while (true)
     {
         std::cout << b << std::endl; // 0
         b = true;
         std::cout << b << std::endl; // 0
     }
 }

 // Issue arises when compiled with Apple LLVM 4.1 and -O2:
 //     clang++ -O2 main.cpp

 int main(int argc, char ** argv)
 {
     this_works();
     this_works_too();
     this_doesnt_work();
     return 0;
 }
 }}}

 This happens only when the optimization level is set to at least 2. It
 happens in clang++ 4.1, but works in clang++ 3.2. Maybe it's possible to
 work around that issue, since std::atomic works fine.

 Best regards,
 Andreas

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/7892>
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