----Original Message---- From: Peter Dimov [mailto:pdimov@mmltd.net] Sent: 08 December 2005 16:46 To: boost@lists.boost.org Subject: Re: [boost] [boost::throw_exception] and platforms where itdon't throw

Martin Bonner wrote:

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From: Peter Dimov [mailto:pdimov@mmltd.net]

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And of course in a situation where throw_exception is used to throw bad_alloc, an assertion makes even less sense, because there are no "logic errors" involved, and presenting the effects of a failed assertion to the end user would serve little purpose; the program could do nothing to defend itself from the out of memory situation.

But if a library is being used in an exception free environment, maybe presenting an assertion failure to the user is as good as you can do.

Possibly, but who is "you" in the above sentence? The library author.

The whole point of using an exception is that you the library author do not take responsibility of handling the error, leaving it up to you the library user to do that instead. Right. But the problem is what does the author of boost::whatever do when the user wants to use boost::whatever in an environment that doesn't support exceptions?

One solution is to offer two functions (like at() and operator[]) and the user who doesn't want exceptions uses the no-throw function. That's a good solution sometimes, but there are other occasions where adding all that extra machinery to support the few no-throw users is a bit much. In those circumstances, it may be better for boost::whatever to say "if your environment supports exceptions, you can handle condition x by catching y; if not, condition x will crash your program." The no-throw users may decide they know condition x is not going to happen, or that crashing is OK, or that they can't use the library. At least that way the users get to choose. -- Martin Bonner Martin.Bonner@Pitechnology.com Pi Technology, Milton Hall, Ely Road, Milton, Cambridge, CB4 6WZ, ENGLAND Tel: +44 (0)1223 441434