Pointer Based Basing Pointers and Debug

Archived from comp.sys.ibm.as400.misc

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Message-ID: <43C84A3C.38DF558@ca.ibm.com>
Date: Fri, 13 Jan 2006 19:47:56 -0500
From: Barbara Morris 
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Subject: Re: When the based variable's basing pointer is pointer based...

Chris Pando wrote:
> When the based variable's basing pointer is pointer based
> you can't use debug to display it.

That's true when debugging RPG.  At least, you can't display the
variable directly.

But for RPG and I believe COBOL, the debugger supports an a->b->c syntax
for following multiply-based pointers.  "A" is the top level pointer, B
is the pointer based on A, and C is the variable based on B.

 d recordDS        ds                  Based(ds@)
 d  parent@                        *
 d  objLen                       10i 0
 d  objDat                       10i 0
 d  objSiz                       10i 0
 d  objVar                        1a

 d ds@             s               *   Based(ds@@)

===>  eval ds@@->ds@->objLen

You can go more levels than 3, and you can modify variables this way:

===> eval ds@@->ds@->parent@->objDat = 13

To get the debug expression, work from right to left starting with the
variable you want to display:


Now add the basing pointer for objLen:


Now add the basing pointer for ds@:


The expression is ready when you reach a pointer that is not based (ds@@).

 ===> eval  ds@@->ds@->objLen

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BrilligWare/ chris@pando.org / revised February 2008