Re: Help with embedded hardware/software platform selection for ADA

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

<mjsilva@scriptoriumdesigns.com> wrote in message 
news:d39ad66d-63a3-43e8-a8ae-3c799c12512e@googlegroups.com...
...
>> Why a hobbyist would even look at Ravenscar?
>>
>Because it provides the simple multitasking that a great many projects can 
>benefit from.

That's true only if you think hobbyists want a lot a frustration. That's 
because Ravenscar makes it impossible to build resilient systems - the lack 
of a entry call with timeout means that any error or failure will cause a 
deadlock. If you are going to use fancy proof tools to *prove* that there 
are no errors or deadlock possibilities, then this is OK (and that's what 
Ravenscar is for), but hobbyists are unlikely to have access to such tools. 
(Heck, *I* have no access to such tools - I'm not even sure if they really 
exist.)

Even if you don't have a sensible recovery action, the timeout can raise an 
exception pinpointing where the deadlock happened -- which greatly eases 
debugging. (I don't think Claw would have been usable without that, as it is 
way too easy to unintentially cause a deadlock by doing the wrong thing in 
an action handler.)

So, IMHO (and much like SPARK), Ravenscar is a tool needed only in very 
specialized circumstances (typically, some sort of certification 
requirement). Otherwise, one ought to forget about it and use Ada as it was 
intended.

                                                  Randy.