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From: mab@dst17.wdl.loral.com (Mark A Biggar)
Subject: Re: Integer'Size < 32 ?
Date: 1996/08/11
Message-ID: <4ulinr$a7q@wdl1.wdl.lmco.com>#1/1
X-Deja-AN: 173553429
references: <9608081258.AA02749@most>
organization: Loral Western Development Labs
newsgroups: comp.lang.ada
Date: 1996-08-11T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <9608081258.AA02749@most> "W. Wesley Groleau (Wes)" <wwgrol@PSESERV3.FW.HAC.COM> writes:
>But I have a related question: many of the posts on the topic repeated
>the definition
>   .... range -(2**31) .. ((2**31)-1)
>I once used a compiler for which Integer'Size = 32 and which had an
>interesting "feature."  It recognized that the above would fit in 32 bits,
>so it compiled for that size.  Then at run-time, it would (obeying
>the precedence rules) try to compute 2**31 and raise constraint_error.
>(I didn't use the parentheses, but that doesn't change the semantics.)
>The ugly work-around was
>   .... range  -2**31 .. 2**30 + (2**30 - 1);
>My question is, "Is this a common 'feature'?"  (Since so many people have
>quoted the same example, I presume the answer is 'no')

At minimum this is bad quality of implementation, for an Ada 95 compiler this
appears to a compiler bug.  Ada 95 basically used a duck* test for static
expression and requires that they be evaluated at compile time even when they
don't appear in a static context.

*duck test: if it look like a duck, quacks like a duck, walks like a duck...
	etc, then it must be a duck even if you see it wahere no duck has
	ever apeared before.

--
Mark Biggar
mab@wdl.lmco.com