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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Efficiency of code generated by Ada compilers
Date: Wed, 11 Aug 2010 18:49:45 -0500
Organization: Jacob Sparre Andersen
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Date: 2010-08-11T18:49:45-05:00
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"Robert A Duff" <bobduff@shell01.TheWorld.com> wrote in message 
news:wcczkwtnvhb.fsf@shell01.TheWorld.com...
> Niklas Holsti <niklas.holsti@tidorum.invalid> writes:
>
>> Yannick Duch�ne (Hibou57) wrote:
>>> This is no more valid Ada (well.... this is still valid Ada 95, this
>>> is just not more valid Ada 2005/2012)
>>
>> In the Ada 2005 RM, see section J.10 (Obsolescent Features: Specific
>> Suppression of Checks).
>
> Right.  And things in the "Obsolescent Features" annex are perfectly
> good Ada, and all Ada compilers are required to support them.
> These features are "obsolescing" so slowly that they will never
> actually become "obsolete".  ;-)

Somewhat irrelevant in this case, because there is no definition or 
agreement as to what it means to suppress checks on a particular type or 
object. One possibility is to do nothing at all (a compiler is never 
*required* to suppress checks). So while this probably will work on most 
compilers, there is no guarantee that it will work the same way.

To make a more concrete example:

     A : Integer : = -1;
     B : Natural := 0;
     pragma Suppress (Range_Check, On => B);

     B := A; -- ??

The language does not say what object or type needs to be suppressed in 
order to suppress the range check on this assignment. It might require the 
check to be suppressed on A or on B or on both or on the subtype Natural or 
on something else. So this feature is best avoided. (Note that this is as 
true for Ada 83 and Ada 95 as it is for Ada 2005.)

                             Randy.