Re: Address of Variable in Service Program Exported Procedure

Correct - the only time the actual data is passed is on a procedure call with a VALUE parameter or when a procedure returns a value.

In the latter case RPG has dealt with this by providing the RTNPARM return value option which handles the large return values as a parameter under the covers.


Jon P.

On Nov 7, 2022, at 3:48 PM, Vinay Gavankar <vinaygav@xxxxxxxxx> wrote:

The reason it was being done was the variable is 32K bytes. I guess it
shouldn't matter as RPG would internally pass the pointer, so there would
be no effect on program performance.

On Mon, Nov 7, 2022 at 3:43 PM Vinay Gavankar <vinaygav@xxxxxxxxx> wrote:

Thanks everyone for your replies. I have changed the Service program and
the calling programs to use variables instead of pointers.

On Mon, Nov 7, 2022 at 12:24 PM Jon Paris <jon.paris@xxxxxxxxxxxxxx>
wrote:

As others have intimated this is a _really_ bad idea even if it worked -
which would be circumstance dependent. It is a very error prone design.

Returning a pointer in general is rarely a good idea for two main
reasons. One, the code that has the address can change the content of the
variable "invisibly". And 2) The code that has that pointer has no way of
knowing if it is still valid! If it pointed to stack storage (for example)
it would still be valid pointer long after the storage had been reused by
another process!

This is in the category of things your mother (had she been a programmer)
would have warned you would make you go blind if you kept doing it!


Jon P.

On Nov 7, 2022, at 9:52 AM, Vinay Gavankar <vinaygav@xxxxxxxxx> wrote:

Hi,

We have an exported procedure in a Service program (RPG) which needs to
pass back the address of a variable, so that the calling program can
use the value in that variable.

Can the calling program (RPG) access the value of the variable if it is
defined within that exportable procedure, or does the variable need to

be

'global' in the Service Program?

TIA
Vinay
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