Re: Regarding retrieving source from modules -- MIDRANGE-L




 > So, does the RPG compiler optimize the executable?  Or is that either not
 > possible, or an additional step I need to perform?

The default is for no (or as close to "no" as the AS/400 goes) optimization.  I
would suggest that you develop and test with this setting for reasons I'll cover
in a moment.  Once the program needs to move into production you can either
recompile and specify a higher level or (safer) simply use CHGPGM and change the
optimization level.

 > If the RPG compiler
 > doesn't optimize my code, then it is a non issue and I can go ahead and
 > compile with *ALL (since there is practically no size increase over *LIST).

This is probably a good time to point out that there is very little difference
in ability to step though a program regardless of what level of optimization you
use.  I've never tried it, but I guess in theory the dead code elimination
process could cause you to step from line 21 to line 23 (apparently) skipping
line 22 and things like this but it is not a practical consideration to my mind.
You'll know when this happens while setting debug points as when you point at
the source line and press F6 - if that line is not "debugable" then the system
just sets a break at  next line that is. Of more concern is the ability to
display and change variables.  at higher levels of optimization when  you
display a variable you may not be seeing the current value.  This is due to
"register" optimization which has caused the variables storage location to not
yet be updated.  I believe a similar process works in reverse when you change a
variable in debug.  If a copy is already in a "register" then your modified
value will not be used. In fact I think at some levels it will not even let you
change the variable.

 > And this CPROBJ (which I have never used before, nor heard of).  Does
 > that just remove the debugging information?  Or is that what actually does
 > the optimization?

Optimization is done by CHGPGM or CRTPGM.  CPROBJ can be used against most any
AS/400 object, look at the help for the command to what it does for each type of
object.  In the case of *PGM and *SRVPGM objects it compresses the observability
information (and I guess debug information in the case of ILE programs).  If you
were a software vendor and wanted to remove debug and/or observability - then
you can use CHGPGM to remove either or both. There is really no   point in
removing observability IMHO but some do it anyway (out of habit since in the
case of OPM programs debug and observability are the same thing ?).  In the case
of ILE programs they are separate and it is possible to remove one without
removing the other.

Let me stress again that debug and observability information are never a
performance consideration.  They do not affect program execution, only physical
DASD storage is involved here.


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