Re: [boost] ARM platform: undefined reference to __sync_fetch_and_add_4

Rob Desbois wrote:

I cannot link against Boost libraries 1.35.0 built with CodeSourcery's ARM/GNU toolchain, although the build is successful. ...

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?

Two workarounds are available: define BOOST_SP_DISABLE_THREADS to disable MT-safety for the reference count, or define BOOST_SP_USE_PTHREADS to use a pthread_mutex.