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From: =?iso-8859-15?Q?Yannick_Duch=EAne_=28Hibou57=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Record aggregates assignments and the black-box and else
Date: Mon, 10 May 2010 21:03:44 +0200
Organization: Ada At Home
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Date: 2010-05-10T21:03:44+02:00
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Le Mon, 10 May 2010 17:20:08 +0200, Adam Beneschan <adam@irvine.com> a  =

=E9crit:
> where R was previously uninitialized.  Even though R.A is supposed to
> have subtype "Natural", if it's uninitialized and thus garbage, it
> could have a negative value.  Thus, it's possible that this
> assignment, which is conceptually part of the assignment that creates
> the temporary object:
>
>    Temp_Object.A :=3D R.A;
>
> could raise an exception if R.A happened to have a garbage negative
> value.
What should be involved here, is access to uninitialized value rather th=
an  =

range-check error. Unfortunately, I don't know a way to achieve this in =
 =

Ada (except with some GNAT pragma which requires to initialize scalars s=
o  =

as to be sure it will later raise a range-check error if it was not  =

properly initialized... still indirect)

> Anyway, assuming that the compiler determines that R.A will not raise
> an exception, and that B =3D> 5 cannot raise an exception either, and
> there aren't any other reasons why R has to be preserved while the
> temporary object is being created, it might decide that there's no
> reason to create a temporary object.  This is permissible since the
> semantics would be exactly the same in all cases.  Then it's
> conceivable that the compiler could generate code that looks like
I agree with you about this semantic equivalence.


-- =

No-no, this isn't an oops ...or I hope (TM) - Don't blame me... I'm just=
  =

not lucky