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From: "Hyman Rosen" <hyman.rosen@gmail.com>
Newsgroups: comp.lang.ada
Subject: Re: Ada exception block does NOT work?
Date: 18 Aug 2005 15:01:01 -0700
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Date: 2005-08-18T15:01:01-07:00
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Robert A Duff wrote:
> But it does mean that exceptions are not well-integrated,
> since certain run-time errors that really ought to cause
> exceptions do not.  For example, overflow on signed integer
> arithmetic.

This argument is flawed. It would make sense only if C++
detected signed overflow and reported the error other than
by raising an exception. C++ merely follows the lead of
its parent language and does no checking for this condition.
It's not because exceptions were unavailable, it's because
requiring the check was conceived to be potentially too
costly and would have served as a barrier to adoption because
it would have slowed down the equivalent code in C++ with
respect to C.

Actually, since signed overflow is undefined behavior, an
implementation is free to check for it and raise an exception
if it wants to.

The checked vector accessor reports a bad index through
exceptions. The memory allocator reports failure through
exceptions. The formatted I/O system can report failure
through exceptions (although it's normally more convenient
to check for errors at the end).