Re: instance counter

From:

Moshbear dot Net <moshbear.net@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sat, 11 Jun 2011 15:58:12 -0700 (PDT)

Message-ID:

<80324efc-d3cb-44c9-be7e-837ead801ec6@m4g2000yqk.googlegroups.com>

On Jun 11, 6:43 pm, "Chris M. Thomasson" <cris...@charter.net> wrote:

"Moshbear dot Net" <moshbear....@gmail.com> wrote in messagenews:ccf39133=

-e576-456d-9ee2-66f9bebdf8aa@d14g2000yqb.googlegroups.com...

Given
class Fred {
public:
   Fred() {
     ctr = ++xctr;
   }
...
private:
   unsigned ctr;
   static unsigned xctr; // initialized via boost::thread::run_once
...
};
,
what would be the best way to make the increment-and-read of xctr
atomic so that it is thread-safe?

Perhaps an atomic fetch-and-add operation, or a statically initialized
PThread mutex.

Is there a portable way of doing
atomic {
++xctr;
ctr = xctr;
}

Also, it looks like I'm going to have to search the boost docs for
mutex-locked statically-scoped counters.
However, I believe that somebody has already done this and can offer
guidance as to which boost class is
preferred (or c++0x/tr1 class, given that this is c.l.c++ :)

I'm using xctr to track instance number of class so that I can use
operator<(const Fred&) to compare by instance-creation time.

What happens when that "version counter" wraps around?

I'd be using ::uint64_t in actual code. This was just to show the
concept.