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Re: New atomics not mentioned in /gcc-4.7/changes.html


On 02/08/2012 10:23 AM, Jonathan Wakely wrote:
On 8 February 2012 13:06, Andrew MacLeod<amacleod@redhat.com> wrote:
On 02/08/2012 05:54 AM, Richard Guenther wrote:
On Wed, Feb 8, 2012 at 10:59 AM, Jonathan Wakely<jwakely.gcc@gmail.com>
  wrote:
Should they be?
Yes. Esp. also the deprecation of the __sync builtins.
Yes, I meant to do that last week, but instead it's this week :-P     Gerald
had pinged me about it a while ago.
Great, thanks - I was thinking about adding a line to the C++11
improvements in the libstdc++ section mentioning the new
implementation of<atomic>, do you think it's worth it?
Sure. There are 2 benefits for c++ now

- We can compile atomic objects of any arbitrary size/type now. Previously there was a compiler error if it was not an integer class that mapped to a supported size of lock-free __sync call. Now a user POD that is the same size as a supported integer will use the lock free instructions.

- If there is not a lock free sequence it becomes a library call. Although this release does not include an atomic library, I have made a sample source file available on the wiki which can be compiled and linked with code to resolve those library calls (using a locked implementation) Its located in external library section of the wiki: http://gcc.gnu.org/wiki/Atomic/GCCMM

Andrew


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