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

From: Schrader, Glenn (gschrad_at_[hidden])
Date: 2008-04-04 08:35:31

> -----Original Message-----
> From: boost-bounces_at_[hidden] [mailto:boost-bounces_at_[hidden]]
> On Behalf Of Peter Dimov
> Sent: Thursday, April 03, 2008 1:42 PM
> To: boost_at_[hidden]
> Subject: 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.
>
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.