Experimental Physics and
Industrial Control System

Marty Kraimer <[email protected]> · Mon, 07 Jul 1997 09:53:52 -0500

Bob Dalesio wrote:
> 
> I think it would be nice if the record was able to detect this
> and set it's status to BAD_CALC and not take a dirt nap. Do you
> have a copy of the expression that did the dirty deed.
> 
>         Bob

Done. This will be in next 3.13 release.
The fix involved adding one to all defines in post.h
so that it could start:

#define         BAD_EXPRESSION  0
#define         FETCH_A         1
#define         FETCH_B         2
#define         FETCH_C         3

postfix.c and calcPerform were changed to use BAD_EXPRESSION.
This means that ANY record type that uses calcPerform should
work if it meets two conditions:

1) The array holding the reverse polish notation is initialized
   to start with a null. (This is automatically done if a field
   defined in the dbd file is used).
2) The record type checks the return code from calcPerform, i.e.
   it has code similar to the following:

if(calcPerform(&pcalc->a,&pcalc->val,pcalc->rpcl)) {
     recGblSetSevr(pcalc,CALC_ALARM,INVALID_ALARM);
} else pcalc->udf = FALSE;

What made things crash before was:

1) FETCH_A was defined to be 0
2) The array holding the rpn was initialized to nulls.

This meant that calcPerform got something that looked
like an expression starting with a bunch (at least 200) of FETCH_A.
I did not look hard enough to see what happened next but I can
imagine really bad things.

Marty Kraimer

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System