[Boost-bugs] [Boost C++ Libraries] #9842: long long not lockfree on i686 compiled with clang

Subject: [Boost-bugs] [Boost C++ Libraries] #9842: long long not lockfree on i686 compiled with clang
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-04-06 21:14:37

#9842: long long not lockfree on i686 compiled with clang
-------------------------------------+--------------------------
 Reporter:  gjasny@…                 |      Owner:  timblechmann
     Type:  Bugs                     |     Status:  new
Milestone:  To Be Determined         |  Component:  atomic
  Version:  Boost Development Trunk  |   Severity:  Problem
 Keywords:                           |
-------------------------------------+--------------------------
 $ clang --version
 Hello,

 I just discovered that the lockfree test fails on trunk:
 ====== BEGIN OUTPUT ======
 atomic<char> is always lock free
 atomic<short> is always lock free
 atomic<int> is always lock free
 atomic<long> is always lock free
 lockfree.cpp(29): test lock_free_macro_val == lock_free_expect failed in
 function: 'void verify_lock_free(const char *, int, int) [T = long long]'
 atomic<long long> is never lock free
 atomic<void *> is always lock free
 atomic<bool> is always lock free

 My system is a Mac with 10.9 and Xcode 5.1:
 Apple LLVM version 5.1 (clang-503.0.38) (based on LLVM 3.4svn)
 Target: x86_64-apple-darwin13.1.0
 Thread model: posix

 I build the three with:
 b2 toolset=darwin architecture=x86 address-model=32

 I think t boils down to the following:

 $ clang -march=core2 -dM -E - -m32 < /dev/null|grep -i
 __GCC_ATOMIC_LLONG_LOCK_FREE
 #define __GCC_ATOMIC_LLONG_LOCK_FREE 1

 The lockfree test expects 2 here.

 (Clang 3.4 on Linux also just returns 1 for long long).

 If I change the code in the platform header and switch from gcc-atomic.hpp
 to gcc-x86.hpp the test passes.

 Thanks,
 Gregor

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/9842>
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