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From: Aaron Metzger <ametzger@erols.com>
Subject: Re: GNAT exception traceback
Date: 1997/06/14
Message-ID: <33A22F37.41CBA26B@erols.com>#1/1
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References: <339EFAE3.26C@ccis.adisys.com.au> <dewar.866126413@merv>
Organization: Erol's Internet Services
X-Received-On: 14 Jun 1997 01:39:33 GMT
Newsgroups: comp.lang.ada
Date: 1997-06-14T00:00:00+00:00
List-Id: <comp.lang.ada>


Robert Dewar wrote:
> 
> Steve asks
> 
> <<My question is, without running gdb or adding additional exception
> handlers, is it possible to generate traceback information to determine
> which line of code in which package generated the exception, and if so
> how ?
>  >>
> 
> You need to run gdb to get the traceback. This is easy to do, so it is
> not clear why you set the precondition of not using it (your question is
> a bit like saying: can I use GNAT to compile my Ada program without
> using gcc -- the answer in both cases is no!)

I believe that Steve's question does have merit.

I was going to wait until I had studied the implementation of exception
handling in GNAT before posting a similar question but since someone
brought it up here goes ...

We develop applications written in Ada for use in embedded systems.  Due
to limited resources in the embedded target, the production code is
generally delivered with a few judiciously placed exception handlers in
outer scopes to recover the system just in case something slipped
through testing and propogates an unhandled exception.

The systems are first subjected to extreme operating conditions while
many miles away from the software developers and a debugger.  If an
error occurs it is often not repeatable due to the complex environment
that the system is in.

This means that we get just one chance to collect all possible
information about what the software was doing at the point that an
exception was propagated.

It would be an EXTREMELY valuable capability if the
Ada.Exceptions.Exception_Information function carried with it some
information about where the exception was originally raised or even
better a full traceback.

This may be too much baggage to justify implementation in the compiler
but nevertheless it would provide a useful capability to a certain group
of users.

------------- 
Aaron Metzger