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NNTP-Posting-Date: Sat, 08 Oct 2011 08:14:32 -0500
Date: Sat, 08 Oct 2011 09:14:15 -0400
From: "Peter C. Chapin" <PChapin@vtc.vsc.edu>
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Subject: Re: What's wrong with C++?
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Date: 2011-10-08T09:14:15-04:00
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On 2011-10-07 21:24, Randy Brukardt wrote:

> But isn't that a really terrible error message? When I've had compiler bugs
> that caused infinite loops, I've often spent many hours trying to find a
> work-around, and only trial-and-error works (there being no information at
> all as to the cause).

You're right, of course, that the "error message" is not very helpful 
when the compiler just fails to terminate. In our case it wasn't too bad 
because we were doing frequent builds so the amount of material under 
suspicion was not large.

The problem was due to a subprogram with a large number of overly 
complicated expressions... a relatively well isolated construct. The 
SPARK simplifier appeared to hang while processing that subprogram (it 
was nice that it outputs a message each time it moves on to a different 
one) so it was pretty obvious what the problem was once we looked at the 
offending code and at the massive collection of VCs the Examiner had 
created for that code. We also learned an important lesson about SPARK: 
keep it simple.

Peter