Re: [boost] Re: Lock Classes: Does anyone care.

From: Kevin Atkinson (kevin_at_[hidden])
Date: 2003-02-19 14:13:59

On Wed, 19 Feb 2003, Kevin Atkinson wrote:

> On Wed, 19 Feb 2003, Alexander Terekhov wrote:
> 
> > Kevin Atkinson wrote:
> 
> > > >  static const pthread_mutex_t MUTEX_INIT = PTHREAD_MUTEX_INITIALIZER;
> > > >
> > > >  class Mutex {
> > > >    pthread_mutex_t l_;
> > > >  public:
> > > >    Mutex() : l_(MUTEX_INIT) {}"
> > > >              ^^^^^^^^^^^^^^
> > > 
> > > I believe this behavior is well defined.  ....
> > "....
> >  Only /mutex/ itself may be used for performing synchronization. 
> >  The result of referring to copies of /mutex/ in calls to <snip>
> >  is undefined."
> >
> > End of story.
> 
> You ignored the rest of my argument.  Neither the right hand side or the
> left hand side of the assignment involve a mutex that has ever been used
> in any way by any function.  It may be technically undefined by the POSIX
> standard however I can not see any way that this can do any harm.  I
> challenge you to find an implementation in which what I did will cause a
> problem, or for that matter an hypothetical implementation.

Alright after reading the standard a bit closer on the behavior
PTHREAD_MUTEX_INITIALIZER.  It says it can be used to statically
initialize a mutex and implies it may only be used in the form of
"pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER".  However I do not see 
how:

  static const pthread_mutex_t MUTEX_INIT = PTHREAD_MUTEX_INITIALIZER;
  pthread_mutex_t mutex = MUTEX_INIT.

is functionally different than the form it gives.

-- 
http://kevin.atkinson.dhs.org