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Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually

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On Sat, Jul 07, 2012 at 03:50:59PM +1200, Ian Collins wrote:
> On 07/ 7/12 09:29 AM, Uncle Steve wrote:
> >On Sat, Jul 07, 2012 at 12:37:59PM +1200, Ian Collins wrote:
> >>On 07/ 7/12 08:27 AM, Uncle Steve wrote:
> >>>On Sat, Jul 07, 2012 at 11:29:02AM +1200, Ian Collins wrote:
> >>>>On 07/ 7/12 06:33 AM, Uncle Steve wrote:
> >>>>>
> >>>>>Is there are C standard threading framework?
> >>>>
> >>>>Yes, read C11.  If you are familiar with pthreads, you'll see where most
> >>>>of the new primitives originate.
> >>>
> >>>Well, I don't follow gcc development, so I don't know when those
> >>>features will be available on my system.
> >>
> >>Then use your platform's native threading primitives.
> >
> >Doing so would incur a performance penalty in comparison to my
> >synchronization primitives in some circumstances.
> 
> In other words, correctness would incur a performance penalty in 
> comparison to your synchronization primitives in some circumstances.

You probably shouldn't be using google translate to massage my code
into something you can understand.  It doesn't work like that.
 
> >>>O.K., so do nested structure elements inherit the parent structure's
> >>>volatile attribute?
> >>
> >>A volatile T is a volatile T no matter what it contains.
> >
> >Look.  In threaded applications, the truth associated with the value
> >associated with certain variables can be somewhat indeterminate.  If
> >that's true in your code, you might want to be aware of it.
> 
> If I could parse that, I'd respond to it.

Yeah well it happens.
 
> >>>>>While the specifics of an implementation within a given operating
> >>>>>system are not C issues, certain common optimizations can be a problem
> >>>>>with certain algorithms, and so there ought to be a C solution to the
> >>>>>problem.  What is it about the volatile attribute that makes it
> >>>>>insufficient in your mind to the problem presented by threaded code?
> >>>>
> >>>>Given you are the one going against conventional wisdom, what in your
> >>>>mind makes volatile a solution to the problem presented by threaded 
> >>>>code?
> >>>>
> >>>>In addition, what is "the problem presented by threaded code"?
> >>>
> >>>Well, code optimization from global CSE might eliminate memory
> >>>accesses to variable that could be modified by other threads in ways
> >>>that affect the algorithm.  Depends of the code.
> >>
> >>If the code depends on volatile, it is broken.  Use the atomics or
> >>synchronisation primitives provided by the language or platform.  They
> >>exist for a reason.
> >
> >You aren't listening to me.
> 
> You aren't making much sense.
> 
> An example of you your synchronization primitives would clear things up.

Sorry, you're going to have to wait.


Regards,

Uncle Steve

-- 
The moon has never been closer.

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Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Uncle Steve <stevet810@gmail.com> - 2012-07-06 14:33 -0400
  Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Ian Collins <ian-news@hotmail.com> - 2012-07-07 11:29 +1200
    Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Uncle Steve <stevet810@gmail.com> - 2012-07-06 16:27 -0400
      Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Ian Collins <ian-news@hotmail.com> - 2012-07-07 12:37 +1200
        Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Uncle Steve <stevet810@gmail.com> - 2012-07-06 17:29 -0400
          Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Ian Collins <ian-news@hotmail.com> - 2012-07-07 15:50 +1200
            Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Uncle Steve <stevet810@gmail.com> - 2012-07-06 19:55 -0400
          Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2012-07-07 17:04 +0300
  Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Eric Sosman <esosman@ieee-dot-org.invalid> - 2012-07-07 08:16 -0400
    Re: Clarification on the applicability of compile-time optimization to a struct variable which encompasses a mixture of fields declared as volatile and non-volatile individually Uncle Steve <stevet810@gmail.com> - 2012-07-07 05:09 -0400

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