Re: CA library usage problem

[Andrew Johnson via Tech-talk <tech-talk@aps.anl.gov>]

Hi Jörn,

On 9/29/22 7:49 AM, Jörn Dreyer via Tech-talk wrote:

i guess I have a misunderstanding how to use the user callback functions 
together with a subscription to a PV variable.

In my userfunc the value of arg.status is always 1 which evaluates to a 
ca_message of "Normal successful completion". But the documentation say's to 
check against ECA_NORMAL witch is 0.

What am I doing wrong here.

Actually the macro ECA_NORMAL expands to the value 1, so arg.status == ECA_NORMAL will evaluate to true in your userfunc as described above. The status macros defined in caerr.h are somewhat confusing as they are actually a bitmask — the bottom 3 bits are a severity code, and the severity code CA_K_SUCCESS has the value 1. I suspect this may have been done to avoid using a status value of 0 which could then be used to detect the absence of a status value, although I doubt if anyone uses it like that now.

HTH,

- Andrew

-- 
Complexity comes for free, Simplicity you have to work for.