I cannot link against Boost libraries 1.35.0 built with CodeSourcery's ARM/GNU toolchain, although the build is successful. I built Boost with: bjam --with-regex --with-serialization --with-thread stage And tried to link to the test program from the 'Getting Started (Unix)' guide I get: $ arm-none-linux-gnueabi-g++ test-regex.cpp -I. stage/lib/libboost_regex-gcc42-mt-1_35.so /tmp/ccVow1Eq.o: In function `boost::detail::atomic_decrement(int*)': test-regex.cpp:(.text._ZN5boost6detail16atomic_decrementEPi[boost::detail::atomic_decrement(int*)]+0x18): undefined reference to `__sync_fetch_and_add_4' collect2: ld returned 1 exit status With assistance on the boost-build list I've ascertained that the problem is that GCC doesn't support __sync_fetch_and_add and the other atomic built-ins on ARM. An additional case for this may need to be added to boost/detail/sp_counted_base.hpp I don't know enough to patch boost for this, short-term or otherwise; can anyone offer any advice? TIA, --rob