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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 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.

>>> 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.

>>>>> 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.

-- 
Ian Collins

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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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