IBM AS/400 manual After the Else, Move Inlr, Else ADD

	*=================================================================*
	* NOLOOP:		Show how to avoid	recursion in a *PSSR subroutine.				*
	*=================================================================*
	*-----------------------------------------------------------------							*
	* Array that will be used to			cause an error				*
	*-----------------------------------------------------------------							*
D Arr1			S	10A	DIM(5)
	*-----------------------------------------------------------------							*
	* Generate an array out of bounds error to pass control to *P￿SSR. *
	*-----------------------------------------------------------------							*
C			Z-ADD	-1		Neg1	5 0
C			MOVE	Arr1(Neg1)		Arr1(Neg1)
C			MOVE	*ON		*INLR
	*=================================================================*
	* *PSSR: Error Subroutine for the procedure. We use the							*
	*	variable InPssr to detect recursion in the PSSR.						*
	*	If we detect recursion, then we *CANCL the procedure.						*
	*=================================================================*
C	*PSSR		BEGSR
C			IF	InPssr = 1
C			MOVE	'*CANCL'		ReturnPt	6
C			Z-ADD	0		InPssr	1 0
C			ELSE
C			Z-ADD	1		InPssr
	*							*
	*		We now generate another error in the PSSR to see					*
	*		how the subroutine	cancels the procedure.				*
	*							*
C			MOVE	Arr1(Neg1)		Arr1(Neg1)
	*							*
	*		Note that the next	two operations will not be				*
	*		processed if Neg1 is still negative.					*
	*							*
C			MOVE	'*GETIN'		ReturnPt
C			Z-ADD	0		InPssr
C			ENDIF
C			ENDSR	ReturnPt
Figure	115.	Avoiding a Loop in an Error Subroutine

To create the program and start debugging it, using the source in Fig

CRTBNDRPG PGM(MYLIB/NOLOOP) DBGVIEW(*SOURCE)

STRDBG PGM(MYLIB/NOLOOP)

Set a break point on the BEGSR line of the *PSSR subroutine so you can through the *PSSR subroutine.

When you call the program, the following occurs:

1. An

exception

occurs

when the

program

tries

to do a MOVE operation

array

using

a

negative

index.

Control is passed to the *PSSR.

2. Since

this

is

the

first time through the *PSSR, the variable In_Pss

already

set

on.

To

prevent

a

future

loop,

the variable In_Pssr is

3. Processing

continues

within

the

*PSSR

with

the

MOVE

after the ELSE.

Aga

an

exception

occurs

and

so

processing

of the *PSSR

begins anew.

4. This

time

through,

the variable In_Pssr

is

already set to 1. Sinc

that

the

subroutine

is

in

a

loop,

the

procedure

is canceled by

s

ReturnPt

field

to

*CANCL.

236

ILE RPG for AS/400 Programmer's

Guide