Re: Passed by Reference vs. Passed by Value

"RPG400-L" <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> wrote on 03/11/2020
06:15:55 PM:

This is a comment not specifically to Dave's post but also to the
post he was commenting on.

Programs can ONLY receive parameters by reference. The VALUE
keyword is not permitted on a PI/PR for a program. If a parm is
declared as CONST then IF it does not match the definition a copy is
made and a pointer to the copy is passed. In all other cases a
pointer to the original data is passed.

For procedures parms can be passed by reference or value. In both
cases the parameters are effectively pushed onto the stack and then
popped in the called procedure. If you pass a field by value a copy
of the actual data is pushed on the stack. There are minor
exceptions to this in a few oddball cases such as floating point
fields but it is valid to think it this way.

Sorry, I misspoke when I said "...where one program was passing a
parameter by reference (by default) but the called program expected the
parameter to be passed by value (explicitly)...". I corrected myself
later as it was a CL program using CALLPRC to call an RPG procedure -- a
service procedure, specifically. So, yes the VALUE keyword *is* allowed
on the PR/PI in such a case and, yes, in such a case the RPG procedure is
expecting an actual data value to be passed in the call stack and *not* a
pointer to the data value (as is the usual case).


Sincerely,

Dave Clark