Re: Converting RPG to RPG ILE

[Joep Beckeringh <joep@xxxxxxxxxxxxxxxxxxx>]

Barbara,

I understand what you mean, but it is not always as clear cut as you put it.

Sometimes overflow can be totally harmless: We had a customer who had, 
for obscure historical reasons, a field 'Number of times sold this year' 
in their item file. For even more obscure reasons the field was defined 
3P0. Nobody ever looked at the contents of that field. When we converted 
the program to RPG IV and changed the harmless looking 'ADD 1' to an 
EVAL, we discovered that it overflowed a few times each week. We were, 
eh, not enthousiastic about the way we discovered it.

Sometimes overflow can be harmful, but is easily repaired afterwards: I 
once used too small intermediate fields in a currency calculation, 
loosing 6 million Dutch Guilders (appr. 3 million dollars) in the 
process. Luckily it was RPG III, so the process completed normally. The 
next morning the customer immediately spotted the deficit; they repaired 
the database with a few corrective bookings and I repaired the program. 
Had the program stopped at the overflow, I would have had to clean up a 
half completed invoice process. Believe me, that would have been a mess.

So, overflow can be dangerous and stopping with an error is a sensible 
default action to take. But I think it was unfair that, until MONITOR 
was introduced, it was the only possible action and that there was no 
way for a programmer to deal with it other than delving into condition 
handlers. Just EVAL(E) would have done the job nicely.

Joep Beckeringh


Barbara Morris wrote:
> "Lapeyre, Francis" wrote:
> > The way I have it set, no, because there comes a point where adding one
> > to anything can possibly cause an overflow. But you can go into the
> > source and fix it. If I put a 'Z' in the numeric area for that line, it
> > changes to Eval X = X + 1.  I only do this if I'm dead sure I'll never
> > overflow the value.
>
> If you leave it as ADD, and it overflows someday, wouldn't you want to
> know about that?
>
> Overflow exceptions are a Good Thing.  They're like the pain you get
> when you put your hand in the fire; the pain may be bad, but the burnt
> hand is worse.