Re: Passed by Reference vs. Passed by Value

CONST does not always create a copy...

CONST is only enforced by the compiler...

The callee of a VALUE parm, can modify it ...but it will never get back to
the calling program.
Whereas if the callee has CONST, the compiler won't allow the variable to
be modified.

If the PR used by the caller has CONST and the PI/PR used by the callee
does not
- everything will compile without error
- if the compiler chose _NOT_ to make a copy (type & length match) then the
callee can successfully change the data in the caller.

This is why you should never have two PR's, define a single PR and /include
it in both places..

Charles



On Wed, Mar 11, 2020 at 3:45 PM Niels Liisberg <nli@xxxxxxxxxxxxxxxxx>
wrote:

CONST is parsing a pointer on the stack to a copy of the data.
VALUE is copying the values on the stack.

So it is the same behaviour.

However with CONST the implementation of the caller can decide if it
wants to encapsulate the variable or let it be modified by the called
procedure. Where VALUE it will always be not modified ( except when you
pass a pointer by value .... it can be a long story .... :)





On Wed, Mar 11, 2020 at 10:26 PM Charles Wilt <charles.wilt@xxxxxxxxx>
wrote:

That's not right...

when yo use VALUE, the actual value is passed, not an address..

Charles

On Wed, Mar 11, 2020 at 3:02 PM <dlclark@xxxxxxxxxxxxxxxx> wrote:

"RPG400-L" <rpg400-l-bounces@xxxxxxxxxxxxxxxxxx> wrote on 03/11/2020
04:38:34 PM:

In which case, the variabkle is copied to a new location and *pointer

to

new location* is passed to procedure.

In the end, you always passed a pointer under covert....

I used to think that. But then I ran into the situation where

one

program was passing a parameter by reference (by default) but the

called

program expected the parameter to be passed by value (explicitly) and

the

called program couldn't see the passed value at all. Explain to me why

is

that? Thanks for the education.


Sincerely,

Dave Clark
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