r259931 - [SystemZ] Define __GCC_HAVE_SYNC_COMPARE_AND_SWAP macros

[Ulrich Weigand via cfe-commits]

Hans,

this is one more patch that should go into 3.8  --  it fixes miscompiles of
code using GCC-provided C++11 system headers like <thread>.

With this patch, the test suite is now clean also with a bootstrapped
clang.

>Author: uweigand
>Date: Fri Feb  5 15:34:28 2016
>New Revision: 259931
>
>URL: http://llvm.org/viewvc/llvm-project?rev=259931&view=rev
>Log: [SystemZ] Define __GCC_HAVE_SYNC_COMPARE_AND_SWAP macros
>
>Define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_[1248] macros on SystemZ.
>
>This fixes a miscompile of GCC C++11 standard library headers
>due to use of those macros in an ABI-changing manner.
>
>See e.g. /usr/include/c++/4.8.5/ext/concurrence.h:
>
>  // Compile time constant that indicates prefered locking policy in
>  // the current configuration.
>  static const _Lock_policy __default_lock_policy =
>#ifdef __GTHREADS
>#if (defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_2) \
>     && defined(__GCC_HAVE_SYNC_COMPARE_AND_SWAP_4))
>  _S_atomic;
>#else
>  _S_mutex;
>#endif
>#else
>  _S_single;
>#endif
>
>A different choice of __default_lock_policy causes different
>sizes of several of the C++11 data structures, which are then
>incompatible when inlined in clang-compiled code with what the
>(GCC-compiled) external library expects.
>
>This in turn leads to various crashes when using std::thread
>in code compiled with clang, as see e.g. via the ThreadPool
>unit tests.  See PR 26473 for an example.
>
>
>Modified:
>    cfe/trunk/lib/Basic/Targets.cpp
>    cfe/trunk/test/Preprocessor/predefined-arch-macros.c


Mit freundlichen Gruessen / Best Regards

Ulrich Weigand

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