Re: [gobo-eiffel-develop] GEC debugger requirements

[Paul C. <pac...@gm...>]

On 8/10/07, Wolfgang Jansen <wj...@so...> wrote:
> Paul Cohen wrote:
> > Ok. Couldn't batch mode (and reading commands from a file/stdin)
> > execution be implemented with not to much effort?
> >
> The debugger is CLI-based. Thus, interactive mode and batch mode
> by reading commands from stdin (and then from an arbitrary file)
> is not very different. The necessary changes/additions include
> - suppressing command prompts
> - redirecting debugger output to a file
> - stop after command error
> There is no problem to make the changes/additions.
>
> But is batch mode really of interest? To my experience,
> debugging will be done if the program does not what was expected,
> i.e. if there is a somewhat surprising outcome.
> Interactive mode is needed to react to unexpected behavior.

Debugging Eiffel wrappings of C code or problems with using C API:s
can be quite tricky at times. I have had cases where it would have
been nice to be able to quickly rerun a debugging session to see if I
get the same behaviour or not, without having to add debug trace
statements to the program. But you are right that having a CLI allows
you to give the debugger commands from stdin. Which is one of the many
benefits of having a CLI-based debugger!

> >
> >> - 3.1 to 3.14, 3.17, 3.18, 3.21,3.22 are available;
> >> - 3.15, 3.16 are not hard to implement. Whether
> >> to implement 3.19, 3.20 is a question of philosophy.
> >>
> >
> > I don't quite understand what you mean by philosophy. Are you saying
> > that editing program data during debugging can be seen as violating
> > some debugging principle or? I see them rather as power debugging
> > features.
> >
> Yes, philosophy means here that some people do not like to change
> program data during debugging.

Ok. I think I'm more pragmatic in this case.

> A viable approach in case of Eiffel
> may be as follows: changing an attribute value is allowed if the class
> of the enclosing object has been compiled with invariant checking on
> and if the invariant is still satisfied after the change.

Yes. That seems reasonable.

> There will be no restriction to change local variables.
> But what about routine arguments? The program must not change them,
> will the debugger be allowed to do so? (This is a secondary problem
> and may be discussed later.)
>

Ok. Obviously there are some issues that need to be resolved/decided
regarding the requirements on data editing. That is to say, if data
editing commands are to be added to the debugger at all. That is the
reason I listed those requirements as lower priority for now.

> I hope that you didn't misunderstand the role that the debugger
> plays in SE: it is not part of the official SE distribution.
> I made the offer to SE1.2 developers to add it to this
> compiler version, but I didn't get any answer so far.

I see. As I said before, I would welcome your debugger contribution to
Gobo very much!

/Paul