clang update may have broken something to do with atomic

[joakim-noah]

I'm compiling the exact same codebase that I was before with clang 3.8.0-2, but it doesn't link anymore when using -std=c++11, because most object files are now missing __atomic_fetch_add_4. Looking at prior C++ builds, none of the object files had that symbol anywhere and I'm not sure where it's coming from now. I think this is a regression in the latest clang, or possibly libandroid-support-dev, which is the only other package containing headers that was updated. I last updated four days ago, so it's something recent that's broken.

Update: Another example is that I was able to build llvm locally before, but it now fails with this message when building with clang:

-- Performing Test HAVE_CXX_ATOMICS_WITHOUT_LIB
-- Performing Test HAVE_CXX_ATOMICS_WITHOUT_LIB - Failed
-- Looking for __atomic_fetch_add_4 in atomic
-- Looking for __atomic_fetch_add_4 in atomic - not found
CMake Error at cmake/modules/CheckAtomic.cmake:36 (message):
  Host compiler appears to require libatomic, but cannot find it.

That first atomics test passes with g++ 6.1.0, so I tried building llvm with g++, but it barfs on the first file in llvm with many errors.

Update 2: By adding -target armv7-linux-android to my CFLAGS and CXXFLAGS, llvm passes the atomic check and is compiling again. Funny what a big difference that subtle change makes. :)

[fornwall]

Thanks! Fixed in the 3.8.0-5 version of the clang package now.