Re: thread lock/unlock example

From: William Kempf (sirwillard_at_[hidden])
Date: 2000-09-14 11:06:17

--- In boost_at_[hidden], Levente Farkas <lfarkas_at_m...> wrote:
> William Kempf wrote:
> > 
> > --- In boost_at_[hidden], Levente Farkas <lfarkas_at_m...> wrote:
> > > William Kempf wrote:
> > > > > create the lock on the heap can't help here.
> > > >
> > > > And why not?
> > >
> > > since you can't protect a.next() in that way.
> > 
> > Why not?
> {
>   boost::lock* lock = new boost::lock(m);
>   for (int i = a.get(); i < 100; a.next())
>   {
>     <some code>
>     delete lock;
>     f();
>     lock = new boost::lock(m);
>     <some code>
>   }
>   delete lock;
> }
> 
> since you can do it just the following way, but this code create 
100 lock
> (for safety:-()

I don't follow you.  You just showed how the heap WILL work to solve 
your problem.  The only issue left is performance, since allocations 
are expensive, but unsafe_lock<> solves this issue by using placement 
new.

> ps. anyway I can agree with csaba, if we don't have lock/unlock on 
mutex at 
> least we need it on lock (yes this is the unsafe_lock and we loose 
compile 
> time check and...almost everything safe, but the exception safety).

Again, I don't know why you keep going back to this argument if 
you're happy with unsafe_lock<> (which need not even be included in 
the library since implementing it is trivial, even though I've 
already agreed to it's inclusion).

Bill Kempf