Re: [boost] [atomic] atomic<int>::is_lock_free() returns false on iPad 4 (armv7s)

Subject: Re: [boost] [atomic] atomic<int>::is_lock_free() returns false on iPad 4 (armv7s)
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2013-09-06 13:43:13

On Friday 06 September 2013 09:20:16 Tim Blechmann wrote:
> >>   boost:atomic<int>::is_lock_free() returns false on iPad 4 (armv7s) but
> >> 
> >> returns true on iPad 3 (armv7). Is this expected or did I build boost
> >> incorrectly?
> > 
> > Most of Boost.Atomic code is header-only, so the problem is not related to
> > building Boost.
> > 
> > I suppose, noone added detection for the armv7s target because noone knows
> > how to detect it at compile time. If you could provide a compiler
> > predefined macro that can be used for this purpose, we could add the
> > support.
> 
> my experience with arm is rather limited (ccing phil, who wrote the
> arm-part), just two points:
> 
> * if armv7s is similar to armv7, it may be safe to adapt
> atomic/detail/platform.hpp with __ARM_ARCH_7S__

I've found that this (and quite a few other) macros are used in 
boost/smart_ptr/detail/spinlock_gcc_arm.hpp, so I've updated Boost.Atomic to 
use them as well. It would be great if anyone could test the updated version 
for the actual ARM target.