[Info-vax] yet another sys$qiow question

Bob Koehler koehler at eisner.nospam.decuserve.org
Wed Aug 19 16:02:21 EDT 2015


In article <55d4ce53$0$1643$c3e8da3$12bcf670 at news.astraweb.com>, JF Mezei <jfmezei.spamnot at vaxination.ca> writes:
> On 15-08-19 09:12, Johnny Billquist wrote:
> 
>> So, you need to tell the C compiler that iosb can indeed be modified 
>> outside of the flow of the program, so that the compilar cannot make 
>> optimizations with regards to the read of the iosb variable. And that is 
>> what volatile do.
> 
> 
> Iteresting use of vocabulary. To me, "volatile" would imply that the
> variable can be optimized away or be temporarily allocated (aka: not
> garanteed to survive after end of subroutine).

   volatile basically means:  there's something going on with this
   data that you, Mr. Compiler, can't see and may not obey you're
   language rules.  So treat the data as volatile and never rely
   on copies you made, nor never fail to fully update it.




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