[Info-vax] yet another sys$qiow question

[JF Mezei]

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).

But based on reading here, "volatile" means the exact opposite, that it
is a variable that must not be optimized away, and much remain allocated.

So, if I have a variable or IOSB structure which is declared outside of
a subroutine in C, what sttribute before "struct" do I put to enable
that "volatile" thing ?