(Comp.sys.hp48)
Item: 2761 by detlef@dmhh.hanse.de [Detlef Mueller]
Subj: About finding moved ROM entries..
Date: 28 Jan 1993

Hi all,

The number of people owning a ROM rev J HP48 grows and most sys-RPL/assembler
programs available as standalone objects or libraries are using 'unsupported'
ROM entry points simply because lot's of low level function aren't 'supported'
(eg. library handling, port management).

The little library provided in this article is a 1st step in trying to find
moved RPL code. It is written using only ROM entries listed in ENTRIES.A of
the HP toolkit, which should be safe on any HP48 ROM version. It provides
two commands, CKOB and CKLIB. CKOB expects an object of any type on the stack,
CKLIB a real number representing the library ID of an installed library. The
object, resp. the objects of a library, are searched for RPL pointer into the
ROM, each is checked for pointing to a valid RPL object.

The following rules define a valid RPL pointer (PTR) into the ROM:

  - a pointer to a primitive code object, ie. [PTR] = PTR - 5
  - a pointer to a RPL object, ie. [[PTR]] = PRLG
  - a pointer to the pointer DupAndThen, ie. [PTR] = DupAndThen

In case no invalid RPL pointer where found, both commands reports
         All inspected RPL
         pointer are valid...
in the status display area and leave the stack unchanged.

If the commands detect ROM pointer not following the above rules,
            !!! Warning !!!
         Found void RPL pointer
is reported in the display status area, the passed object is dropped and
a list of binary numbers is placed on the stack. The binary numbers are
the values of the illegal pointer.

If you get a new piece of software, which was written on a HP48 with a
different ROM revision than yours, run CKOB (or CKLIB in case it's a
library) on it.

If CHKIT reports any invalid RPL pointer, remove the new software immidately
from your HP48, send the list of the illegal pointer to the author of the
software and publish it in comp.sys.hp48 (please include the name of the
software, where you get it from and what ROM rev your HP48 have).

If CHKIT don't report a problem, this only means that the RPL pointer are
valid from the scope of RPL execution, not that the used ROM based code
didn't move !

Also RPL bases on assembler routines; there are some supported assembler
ROM entries and a lot of unsupported ones. Many programs have emdedded CODE
objects, containing assembler code slices or are completely written in
assembler (eg. <-LIB->, QED, StrWrt etc.). These entries can't be checked
for beeing valid without a complete entries list of each ROM rev !

CKLIB only works on an installed library - that may cause trouble, if its
configuration code makes use of unsupported entries !

However, I would really appreciate if someone owning a rev J HP48 will
install the <-LIB-> library (be shure, that flag 5 is clear !), then
executing 1221 CKLIB and mailing me the result..

Bye,
         8-Detlef

+------------------------------------+--------------------------------------+
|`What a depressingly stupid machine'|             Detlef Mueller           |
| -- Marvin                          |          detlef@dmhh.hanse.de        |
+------------------------------------+--------------------------------------+