Re: Removing ATOMIC_REFCOUNT remainders from build system?

[John W. Eaton]

On 10/11/19 12:39 PM, Rik wrote:
> jwe,
>
> Since you re-built the atomic operations atop C++ std::atomic, there
> doesn't seem to be any use for OCTAVE_ENABLE_ATOMIC_REFCOUNT.  Should the
> remaining vestiges in configure.ac, toplev.cc, oct-conf-post.in.h,
> mk-octave-config-h.sh be removed?
>
> Alternatively, we could re-instate the functionality in oct-refcount.h
>
> #if defined OCTAVE_ENABLE_ATOMIC_REFCOUNT
>      std::atomic<T> m_count;
> #else
>    T m_count;
> #endif
>
> This would mostly be of use in determining the penalty we pay for
> cross-thread communication.  It might be useful if we eventually attempt an
> optimization such that only objects which are traveling cross-thread use
> the atomic interface.  But, this is speculative so I'm also fine with just
> removing it.

If someone wants to test the cost of the penalty, it's just a one line 
change.  Even if we keep the test in the code, I'd prefer to remove the 
configure option to avoid giving the impression that it is OK to compile 
with this feature disabled.  I'm inclined to just remove it completely 
to avoid confusion about why there is a macro without a corresponding 
configure test.  I pushed the following changeset:

  http://hg.savannah.gnu.org/hgweb/octave/rev/adcd6740b2c7

jwe