Re: Help with Atomic_Components and whole array assignment

["DuckE" <nospam_steved94@home.com>]

> Note that the detailed list in AARM C.6(20) of disallowed
> transformations has no hint at all of the "separate" part of
> Tuck's claim, and conspicuously does not list combining writes
> as an improper transformation.
>
> Tuck, having something in your mind is not good enough if you
> do not write it down :-)
>
> > In general, that means each read/update is a separate
> > instruction.
>
> No, there is absolutely NO implication of this
>

I find the difference in interpretation of AARM C.6(20) interesting.

This clause states:

  "... The implementation shall not generate any memory reads or updates of
atomic or volatile objects other than those specified by the program."

My interpretation of this statement is: if my program contains two separate
assigments to two distinct variables for which pragma atomic applies, these
assignments will be performed as two distinct operations.  Since the two
assignments appear as separate assignments in the code, if the performed
these assignments are combined as single operation, an update is being
performed that my program did not specify.

Since there is obviously some confusion over this issue perhaps the AARM
should be revised?

BTW: When I first started reading about Ada I didn't realize that there was
any confusion on this issue.  It is actually one of the specific features of
the language that made me think Ada is superior for interfacing with
hardware.

SteveD