RE: DS Array

Years ago a friend, who wrote Cobol, described something like this. He was debugging a program and getting weird results. Turned out to be an out-of-bounds index on an array. Cobol was just calculating that address for the (non-existent) element. No index error; it was just grabbing whatever happened to be at the memory address. As Jon said, this sounds like what the debugger is doing. I just range a test using the iSeries Graphical Debugger and set monitors for element zero [0] of an array and another element beyond the max number of elements. All the monitor did was show blanks for these monitors.

Jerry C. Adams
IBM System i Programmer/Analyst
B&W Wholesale
office: 615-995-7024
email: jerry@xxxxxxxxxxxxxxx


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Jon Paris
Sent: Wednesday, November 05, 2008 10:47 AM
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: DS Array

I've been playing with a DS defined with DIM as opposed to OCCURS
for the first time.

I noticed while debugging that if I type EVAL MyDS I see all the
elements from 1 to the last. As it happens I have 10 elements. But I
can type EVAL MyDS(0) or EVAL MyDS(100000) or any other number as
the element number. I suppose thes elements are also available to
the program, so whats the point of stating DIM(10) on my DS specs
and controlling that I don't try and put more than 10 rows in it?

What's happening?

The debugger has no real reason to do the range checking that a running RPG
program will do so it probably simply does what you tell it and calculates the
address of the element based on what you tell it. I'd have expected zero to
cause a problem - but I'm not that surprised that it doesn't.

Jon Paris
Partner400
www.Partner400.com

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