Re: SRVPGM func compiled w/o VALUE keyword now crashes

[Charles Wilt <charles.wilt@xxxxxxxxx>]

Adding or removing the VALUE keyword on a parameter means both the
called procedure and its callers will need to be recompiled.

Consider with a 15p0 parameter.

With VALUE
What's passed is 8 bytes containing the actual value of the variable.

Without VALUE
What's passed is 16 bytes containing a pointer to the 8 bytes of
memory holding the value.

Thus it should be obvious why you're having problems.

HTH,
Charles

On Mon, Aug 16, 2010 at 3:35 PM, Tyler, Matt <matt.tyler@xxxxxxxxxxxxxx> wrote:
> We have a small function in one of our service programs that was
> recently changed (no names or reasons to be given).  The change seemed
> small but is having an immediate impact.
>
>
>
> The value keyword was taken off the interface of one of the parameters
> so it will be passed by reference now.  The callers were not recompiled
> to use the new interface.
>
>
>
> The passed param and receiving param are both defined exactly as 15p0.
> In the function there is a blank name DS with fields.  No INZ is on the
> DS definition.  The sub field is defined as 15s0.
>
>
>
> In version 1 the system passed the callers data by value to the function
> and then that value was loaded into the DS subfield.  No problems.  The
> subfield loaded just fine.
>
>
>
> Now in version 2 (the one without the value keyword) the program crashes
> attempting to load the subfield with a data decimal error.
>
>
>
> The question I want to answer is why is the function causing a data
> decimal error only when passed by reference and not by value?
>
>
>
>
>
> <code version="1">
>
>  <interface>
>
>     D CalcUPCChkD     PI             1P 0
>
>     D  UPC                          15P 0 Value
>
>  </interface>
>
>  <blankds>
>
>     D                 DS
>
>     D UPCField                      15S 0
>
>     D UPCAr                          1S 0 DIM(15) Overlay(UPCField)
>
>  </blankds>
>
>  <cspec>
>
>       UPCField = UPC*10; // move to left by one
>
>  </cspec>
>
> </code>
>
>
>
> <code version="2">
>
>  <interface>
>
>     D CalcUPCChkD     PI             1P 0
>
>     D  UPC                          15P 0
>
>  </interface>
>
>  <blankds>
>
>     D                 DS
>
>     D UPCField                      15S 0
>
>     D UPCAr                          1S 0 DIM(15) Overlay(UPCField)
>
>  </blankds>
>
>  <cspec>
>
>       UPCField = UPC*10; // move to left by one
>
>  </cspec>
>
> </code>
>
>
>
> When I check the field addressing in both versions they are all
> different between the caller and callee as I would expect on anything
> not call by reference (although pass by reference the addresses are very
> close to each other).
>
>
>
>
>
> Thanks for any insight, Matt
>
>
>
> Full function code here http://code.midrange.com/461e637167.html.
>
> --
> This is the RPG programming on the IBM i / System i (RPG400-L) mailing list
> To post a message email: RPG400-L@xxxxxxxxxxxx
> To subscribe, unsubscribe, or change list options,
> visit: http://lists.midrange.com/mailman/listinfo/rpg400-l
> or email: RPG400-L-request@xxxxxxxxxxxx
> Before posting, please take a moment to review the archives
> at http://archive.midrange.com/rpg400-l.