RE: FOR loop limit

The application isn't hardcoded. This is the actual application source
line:

For CurLblOnItm = 1 To FulItmLbls By 1;

The values in both of those fields were 999 at the time the app bombed. I
wrote the quickie program to confirm that's what the issue was.


--
Jeff Crosby
UniPro FoodService/Dilgard
P.O. Box 13369
Ft. Wayne, IN 46868-3369
260-422-7531
www.dilgardfoods.com

The opinions expressed are my own and not necessarily the opinion of my
company.  Unless I say so.

-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:rpg400-l-bounces@xxxxxxxxxxxx]

On

Behalf Of Mark S. Waterbury
Sent: Thursday, January 29, 2009 3:19 PM
To: RPG programming on the IBM i / System i
Subject: Re: FOR loop limit

Hi, Rory:

Thanks for that link and the doc. excerpt -- I still think this is a
compiler error. The compiler should emit a compile time error,
indicating that the size of the variable is not sufficient, based on the
fact that the compiler "knows" at compile-time the upper limit, in this
case, since it was coded as a literal.

On the other hand, if you had coded:

FOR i = 1 TO x BY 1

then the compiler does not "know" what the upper limit value will be,
but some deductions can be made, e.g. based on the size of the variable
X, especially if both "i" and "x" are declared to be packed decimal.

I still think if the increment is 1, the generated code should never
cause this exception. At least, that's the semantics in most other HLLs
that I know that have a similar for-loop construct. Or, they specify
that the value of the index variable is "undefined" upon exit from the
loop. Oh, well...

Cheers,

Mark S. Waterbury

> Rory Hewitt wrote:

Not a compiler error:

http://publib.boulder.ibm.com/infocenter/iseries/v5r3/index.jsp?topic=/books
/

c092508502.htm

The FOR operation is performed as follows:

1. If the conditioning indicators on the FOR statement line are
satisfied, the FOR operation is processed (step 2). If the indicators

are

not satisfied, control passes to the next operation to be processed
following the associated END or ENDFOR statement (step 8).
2. If specified, the initial value is assigned to the index name.
Otherwise, the index name retains the same value it had before the

start

of

the loop.
3. If specified, the limit value is evaluated and compared to the

index

name. If no limit value is specified, the loop repeats indefinitely

until it

encounters a statement that exits the loop (such as a LEAVE or GOTO)

or

that

ends the program or procedure (such as a RETURN).

If the TO clause is specified and the index name value is greater

than

the limit value, control passes to the first statement following the

ENDFOR

statement. If DOWNTO is specified and the index name is less than the

limit

value, control passes to the first statement after the ENDFOR.
4. The operations in the FOR group are processed.
5. If the conditioning indicators on the END or ENDFOR statement are

not

satisfied, control passes to the statement after the associated END

or

ENDFOR and the loop ends.
6. If the increment value is specified, it is evaluated. Otherwise,

it

defaults to 1.
7. The increment value is either added to (for TO) or subtracted from
(for DOWNTO) the index name. Control passes to step 3. (Note that the
conditioning indicators on the FOR statement are not tested again

(step

1)

when control passes to step 3.)
8. The statement after the END or ENDFOR statement is processed when

the

conditioning indicators on the FOR, END, or ENDFOR statements are not
satisfied (step 1 or 5), or when the index value is greater than (for

TO) or

less than (for DOWNTO) the limit value (step 3), or when the index

value

overflows.


"If the FOR loop is performed *n* times, the limit value is evaluated
*n+1*times and the increment value is evaluated
*n* times. This can be important if the limit value or increment value

is

complex and time-consuming to evaluate, or if the limit value or

increment

value contains calls to subprocedures with side-effects. If multiple
evaluation of the limit or increment is not desired, calculate the

values

in

temporaries before the FOR loop and use the temporaries in the FOR

loop."

On Thu, Jan 29, 2009 at 9:43 AM, Mark S. Waterbury

<mark.s.waterbury@xxxxxxx

wrote:

Hi, Jeff:

IMHO, that looks like an error ("bug") in the compiler generated code

--

you should open a PMR with IBM.

What VxRyMz of i5/OS or OS/400 did you encounter this problem at? And
what did you specify for TGTRLS? (That could affect it if this problem
was already fixed in a subsequent release).

Mark S. Waterbury

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