Path: utzoo!utgpu!water!watmath!clyde!rutgers!cmcl2!brl-adm!umd5!cvl!elsie!nih-csl!keith
From: keith@nih-csl.UUCP (keith gorlen)
Newsgroups: comp.lang.c++
Subject: Exception handling (was: OOPS gripes)
Summary: Popping the exception frames is the easy part
	 calling destructors causes the problem
Message-ID: <306@nih-csl.UUCP>
Date: 7 Feb 88 14:22:53 GMT
References: <3117@okstate.UUCP>
Organization: NIH-CSL, Bethesda, MD
Lines: 36

In article <3117@okstate.UUCP>, norman@a.cs.okstate.edu (Norman Graham) writes:
> in article , keith@nih-csl.UUCP (keith gorlen) says:
> 
> > My inclination is to ignore the OOPS exception handling code as much
> > as possible, and replace it when exception handling is incorporated
> > into C++.
> 
> I tried desperately to design a suitable (ie. simple, transparent, etc)
> exception handling scheme for a project I'm involed with ( >80000 lines 
> of C source in >450 files).  We wanted to use a stack of exception frames
> and we would have, except for one problem... we couldn't guarentee that the
> exception frame stack would be poped on each function return.

Actually, popping the exception frame on each function return is the
easy part.  You just make exception frames instances of a class that
has a destructor, and have the destructor update the exception frame
stack.

But don't get excited -- the real problem is that when an exception
occurs and you want to jump out to an enclosing exception frame,
there's no way to get the destructors of all the objects local to
blocks that are going out of scope called without help from the
compiler.

Bjarne has mentioned in several papers and talks that he's working on
exception handling for C++.  An additional problem is that the C++
exception handling mechanism should work in situations where you have
C and C++ functions calling one another, and the C functions don't
understand C++ exception handling.


-- 
	Keith Gorlen			phone: (301) 496-5363
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