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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada Annoyances
Date: Sun, 25 Jun 2017 18:43:15 -0500
Organization: JSA Research & Innovation
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Xref: news.eternal-september.org comp.lang.ada:47115
Date: 2017-06-25T18:43:15-05:00
List-Id: <comp.lang.ada>

"Niklas Holsti" <niklas.holsti@tidorum.invalid> wrote in message 
news:4921bd4e-3827-a7ac-7f2d-d60edbc514a3@tidorum.invalid...
> On 17-06-23 20:49 , Randy Brukardt wrote:
>> <raph.amiard@gmail.com> wrote in message
>> news:be1619b4-2220-4287-8e67-1af32377d3f7@googlegroups.com...
>> ...
>>> Ada forcing tagged types on you to use certain features *is* a
>>> problem, if only because certain Ada users are forbidden to
>>> use tagged types altogether and thus are prevented to use a
>>> lot of useful features.
>>
>> Stupid language usage rules are not the problem of the language design,
>> they're a management problem.
>
> Sometimes usage rules are imposed by environment constraints, in 
> particular limited resources in smallish embedded systems, combined with 
> reliability requirements which mean that running out of resources at run 
> time must be avoided.
>
>> I can understand banning T'Class (thus banning
>> dynamic dispatching) and banning controlled types (thus banning hidden 
>> calls
>> that can be harder to analyze), but not banning tagged types themselves.
...

> b) the non-static size of class-wide objects (of type T'Class), which 
> means that the compiler and/or the programmer must use dynamic allocation 
> (usually heap or secondary stack) for such objects.
...
> Point (b) is more difficult and I know of no work-around that can be 
> applied at analysis time.

Simply banning the use of T'Class has that effect. It's rather drastic, but 
it eliminates all of the dynamic features. Note that this was considered 
important enough that the standard (in Annex H) restriction No_Dispatch has 
this effect.

You still get the other advantages of tagged types (extension, proper 
inheritance for private, equality, prefixed notation, etc.), and there is 
almost no runtime penalty (or analysis problem).

                         Randy.

    .