Re: STM32F4 GNAT Run Time System - roadmap

["Randy Brukardt" <randy@rrsoftware.com>]

"Simon Clubley" <clubley@remove_me.eisner.decus.org-Earth.UFP> wrote in 
message news:n49suh$en8$1@dont-email.me...
> On 2015-12-08, Randy Brukardt <randy@rrsoftware.com> wrote:
>> "Simon Wright" <simon@pushface.org> wrote in message
>> news:lya8pnh1dq.fsf@pushface.org...
>>> ...I've not done any evaluation yet
>>> aside from noting that they generate the GNAT-specific
>>> Volatile_Full_Access aspect, which is noted in the 'under development'
>>> version of the GCC docs (so, will likely be in GCC 6). Maybe plain
>>> Volatile will do (but users would have to remember to access the whole
>>> register explicitly, rather than leaving it up to the compiler to Do The
>>> Right Thing); that would be an easy-enough patch.
>>
>> The ARG has decided on a different direction to fix the problem addressed 
>> by
>> Volatile_Full_Access; essentially, accesses to non-volatile components of
>> atomic objects have to be accessed with a read-modify-write cycle. (See
>> AI12-0128-1.) Various parts of Annex C will be rewritten to make that 
>> make
>> sense.
>>
>
> Hmm, one of the two I submitted last year. :-) Nice to see it moving 
> forward.
>
> What's the general feeling within the ARG about the related AI12-0127-1
> partial aggregate notation proposal, especially as it applies to updating
> bitfields within device registers ? How likely is that to happen ?

The holdup is that the proposal only covers record aggregates. The similar 
SPARK feature includes all kinds of aggregates, and of course we'd like to 
be able to replace the SPARK feature entirely. The problem being that there 
isn't an obvious extension for array aggregates (it's much messier once 
multi-dimensional arrays are considered), so it's back in the lab at the 
moment. I think there is a good chance that it will be adopted down the 
road, but it's definitely not a slam-dunk.

                                         Randy.