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- Path: fido.asd.sgi.com!austern
- From: Dick Menninger <Dick.Menninger@daytonoh.attgis.com>
- Newsgroups: comp.std.c++
- Subject: Re: Throwing an exception from within a si
- Date: 24 Jan 1996 11:36:13 PST
- Organization: AT&T Global Information Solutions
- Approved: austern@isolde.mti.sgi.com
- Message-ID: <DLp9Ez.796@falcon.daytonoh.attgis.com>
- References: <4e0moi$4dp@engnews1.Eng.Sun.COM>
- Reply-To: mennid <Dick.Menninger@daytonoh.attgis.com>
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- Originator: austern@isolde.mti.sgi.com
-
- > ==========Steve Clamage, 1/22/96==========
-
- > In article 8k8@galaxy.ucr.edu, thp@cs.ucr.edu (Tom Payne) writes:
- > >Steve Clamage (clamage@Eng.Sun.COM) wrote:
-
- > >: What we put in the language standard is binding on all
- > implementations. We
- > >: try to specify things that can be implemented efficiently on
- > any likely
- > >: system. In addition, we try to specify features so that they
- > have no cost
- > >: (or nearly no cost) if you don't use them. IMHO, guarantees
- > about what you
-
- > >Agreed!!
-
- > >: can do in an asynchronous signal handler don't meet those
- criteria for
- > >: inclusion in the C++ standard.
-
- > >That's a rather broad conclusion, given the discussion so far.
-
- > I don't agree. If you have control over the entire environment, you can
- > make more guarantees about behavior. For example, Ada implementations
- > have extensive requirements on what they must support. If a platform
- > cannot reasonably meet those requirements, you aren't going to find an
- > Ada implementation which is both conforming and useful.
-
- > C++, on the other hand, is intended to be dropped into (nearly)
- > any existing
- > platform and coexist with other languages on that platform.
- The language
- > definition attempts to stay away from areas where common platforms have
- > widely differing behavior for that reason. Asynchronous signal handling
- > certainly varies widely among platforms.
- >
- > It's easy to wave your hands and say that the implementation ought to
- > be relatively easy to do and not overly expensive. But what if the ABI
- > on a common platform makes that infeasible? If a language feature
- > limits the number of platforms which allow implementation, it should be
- > important to a wide range of programmers and programs.
-
- It is important for asynchronous threads that may interrupt other
- threads (signal handlers, interrupt handlers, ...) to be able to use
- the same exception semantics that any thread would use. Else
- you must define two sets of C++ behavior and STL, new, etc., must
- all work in both. You made exceptions part of the language, but
- they still seem to be second class citizens. Until they are made
- first class citizens, you will continue to have a lot of arguing about
- inherent problems of them being second class.
-
- This is just one case where trying to limit the standard to ALL
- potential environments seems to be hurting the thinking and
- the language. I suspect that essentially all environments can
- actually do something sensible. If a few cannot, they should
- be exceptional, in that area, to the standard.
-
- Good Day
- Dick
- Dick.Menninger@DaytonOH.ATTGIS.COM
- ---
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