Re: [boost] [Boost-users] [Review] Boost.Atomic review starts today, October 17th 2011

Subject: Re: [boost] [Boost-users] [Review] Boost.Atomic review starts today, October 17th 2011
From: Anthony Williams (anthony.ajw_at_[hidden])
Date: 2011-10-24 06:41:53

On 17/10/11 00:45, Tim Blechmann wrote:
> The review of Helge Bahmann's Boost.Atomic library starts today, October
> 17th 2011. It will end on October 26th.

Just a few quick comments about correctness.

* Operations build on top of compare_exchange (such as fetch_xor in 
gcc-x86.hpp) use memory_order_relaxed for all operations. Are you sure 
there are enough compiler memory barriers? Shouldn't you pass the 
supplied memory order through to the CAS call?

* In gcc-ppc.h the BOOST_ATOMIC_ASM_SLOWPATH_CLEAR macro includes a 1: 
label, yet many of the asm blocks that use it also include a 1: label. 
Is this correct?

* In gcc-x86.h, the platform_cmpxchg64_strong implementation assumes 
that T is an integral type, such that you can do (int)(desired>>32) to 
take the top 32 bits, and (int)desired to take the low 32 bits, which is 
essentially just the signed and unsigned variants of the 64-bit integer. 
This should therefore not be a template, but a plain inline function. 
cas64strong.hpp uses it incorrectly for pointers, but this 
specialization is unnecessary anyway --- this file is only relevant for 
32-bit x86.

Anthony
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