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<== Date ==> <== Thread ==>

Subject: RE: empty channel field in medm/dm2k
From: [email protected] (Jeff Hill)
To: "Ben-chin K. Cha" <[email protected]>
Cc: "EPICS-tech-talk" <[email protected]>
Date: Mon, 22 Nov 1999 11:19:33 -0700
> >      Yes, I have noticed.  It was that way when I got it.  I think it
> > is a hack to avoid some kind of error, but I don't know what.  Perhaps
> > it is to force CA to allocate the usual structures instead of properly
> > handling the situation.  I haven't changed it on the grounds that (1)
> > it (up to now) didn't seem to be causing problems and (2) "Never
> > change a working code ...".  It looks like bad coding proctice, and it
> > would be nice to eliminate it, even if it weren't continually calling
> > CA as Noboru says.
> > 
> >       Unless someone tells me it is a known trick and has a purpose, I
> > will eliminate it (in the next release).
> > 
> 
> I also use this " " to replace the NULL pvname if the user 
> mistakenly provided a NULL string for name search to an 
> interactive CA client. If I remember it right this will 
> avaoid the problem of core dump and accidentally get 
> out of the interactive CA client.
> 

I assume that this "core dump" occurs when SEVCHK() is
called and the severity level of the status returned from
CA is higher than a warning. SEVCHK calls abort() in this
situation.

In production code you should check the status from CA 
and take appropriate action when the user supplies an 
invalid channel name. I assume that appropriate action 
in PV wave would be to set a "bad channel" flag in your
code and return bad status back to PV wave applications 
when they attempt to read and write to a poorly named 
channel.

Jeff 


References:
Re: empty channel field in medm/dm2k Ben-chin K. Cha

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