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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Odd overflow exception being raised in one-line program
Date: Wed, 30 Jan 2013 10:15:23 +0000
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Date: 2013-01-30T10:15:23+00:00
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Jerry <lanceboyle@qwest.net> writes:

> A user of the PLplot plotting package, using Ada bindings, has
> reported an overflow exception that has not occurred before. He
> reports using Fedora rawhide which uses gcc 4.8. He reported the
> conditions surrounding the exception and I used that to make the
> following program and asked him to report his results. Line 7 of the
> below program mimics a line in the Ada binding to which his exception
> points.

>    r := Integer((r1 * 255.001) - 0.499999999999999);

> raised CONSTRAINT_ERROR : Test_Overflow.adb:7 overflow check failed

> I investigated other places (18 total) where he is getting an
> "overflow check failed" exception. In every case, the indicated line
> contains a conversion from Long_Float to Integer using the Integer( )
> function with a Long_Float argument. It appears very likely that the
> exception is happening at every attempt to make such a conversion.
>
> What am I missing here?

Well, GCC 4.8 hasn't been released yet! but a quick check through the
bugs/regressions doesn't show anything like this. Let's hope it doesn't
make it to the release ..

Neither GCC 4.7.0 nor GNAT GPL 2012 shows the problem.