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

From: Rob Desbois (rob.desbois_at_[hidden])
Date: 2008-04-04 09:33:45

On Fri, Apr 4, 2008 at 1:35 PM, Schrader, Glenn <gschrad_at_[hidden]> 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.
>  >
>  Another option would be to just supply the __sync_fetch_and_add_4 function that gcc is trying to link in. When gcc doesn't support the builtin it assumes that a function exists with that name. A snippet of ARM assembly to implement the atomic operation shouldn't be that difficult.

Perhaps not for you. I am a novice when it comes to any assembly, and
have never even touched ARM assembly.
If you can provide the ARM equivalent operation I would be extremely
grateful, but I am unable to code it myself unfortunately.