Experimental Physics and
Industrial Control System

Marty Kraimer <[email protected]> · Wed, 25 Apr 2001 07:47:37 -0500

I will fix this in the next release of both 3.13 and 3.14. Andy was the first
one to make we aware of this bug.

Marty Kraimer

Andy Foster wrote:
> 
> Hi Eric,
> 
> Yes, I noticed this too and have "spoken" (over E-mail) with
> Marty about it.
> 
> There are other records which exhibit the same feature, namely:
> dfanout, stringout, steppermotor.
> 
> All have code similar to the longout with respect to the DOL
> link. What I did was changed the longout and others to be like
> this:
> 
>      if (!plongout->pact) {
>              if( (plongout->dol.type != CONSTANT) && (plongout->omsl ==
> CLOSED_LOOP)) {
>                      status = dbGetLink(&(plongout->dol),DBR_LONG,
>                              &value,0,0);
>                      if (plongout->dol.type!=CONSTANT &&
> RTN_SUCCESS(status))
>                              plongout->udf=FALSE;
>              }
>              else {
>                      value = plongout->val;
>              }
>              if (!status) convert(plongout,value);
>       }
> 
> Then for a CONSTANT DOL type, the value gets initialized as it does
> in an ao record.
> 
> Cheers,
> 
> Andy
> 
> Eric Bjorklund wrote:
> >
> > I appear to have discovered a bug in longoutRecord.c under R3.13.4 which
> > probably dates back to R3.13.3, when the drvh & drvl fields were added.
> >
> > The manifestation is that a longout record with OMSL in closed_loop and
> > a constant value in the DOL link, will end up with an arbitrary value
> > in VAL when the record is processed.
> >
> > The culpret is in the following code from the "process" routine:
> >
> >     if (!plongout->pact) {
> >             if (plongout->omsl == CLOSED_LOOP) {
> >                     status = dbGetLink(&(plongout->dol),DBR_LONG,
> >                             &value,0,0);
> >                     if (plongout->dol.type!=CONSTANT && RTN_SUCCESS(status))
> >                             plongout->udf=FALSE;
> >             }
> >             else {
> >                     value = plongout->val;
> >             }
> >             if (!status) convert(plongout,value);
> >      }
> >
> > If dol.type is CONSTANT, dbGetLink does not fetch the link value, and so
> > the variable "value" is never initialized.
> >
> > The fix, I've implemented for now is to initialize "value" in its declaration
> > at the begining of the process routine, i.e:
> >
> >         long             value=plongout->val;
> >
> > This restores the longout record to its previous behavior -- which is not
> > the same as, for example, an ao record with the similar setup since it
> > allows you to change the value by writing to the VAL field.  For that, however,
> > we'd probably have to add another field to longout (such as the ao's PVAL
> > field).
> >
> > Eric Bjorklund
> > LANSCE-6 Controls
> > Los Alamos Neutron Scattering Center.
> > [email protected]
> 
> --
> Observatory Sciences Limited            Email: [email protected]
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System