Re: Overflow errors on add

[Hans Boldt <boldt@xxxxxxxxxx>]

Euan wrote:
>Hi,
>I am in the process of converting my source from RPG3 to RPG4 and have the
>following piece of code.
>
>RPG3
>add x   y
>
>which translates to
>RPG4
>eval    x = x + y
>
>Now RPG3 is forgiving of overflow errors, but RPG4 is not.
>How can I trap potential overflow errors?
>Can I set a compiler option (in CRTBNDRPG) to show this condition?

The ILE RPG IV compiler has no option which will
ignore numeric overflow in expressions.

You are using a conversion utility which is too
aggressive in its conversions.  As you have seen,
the EVAL doesn't always work the same as the ADD.
So, it might be best to disable this particular
conversion. I believe most tools have that option.

I think the better question is this:  Why are you
getting the overflow exception?  Did you expect
truncation in this situation?

When designing and implementing ILE RPG IV, we
chose to always signal overflow in expressions for
several reasons.  First, the majority of overflow
situations reflect errors in the program.  Since
expressions can be more complex than fixed format
statements, truncation errors would have been more
common and harder to debug.  Second, it's more
difficult to handle truncation meaningfully for
integer, unsigned, and float numeric datatypes.

(Of course, by default, we kept the old numeric
overflow behavior for the decimal data types on old
fixed form statements for compatibility.)

Hmmm, maybe it IS a good idea to convert all
arithmetic to expressions just to see what your
program is doing to the data.  Perhaps you'd find
numeric truncation happening in places you didn't
expect?

Cheers!  Hans

Hans Boldt, ILE RPG Development, IBM Toronto Lab, boldt@ca.ibm.com
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