Re: Bug in epicsMessageQueue?

[Michael Davidsaver via Core-talk <core-talk at aps.anl.gov>]

On 3/20/20 5:00 PM, Mark Rivers wrote:
> Here is the code:
> 
>  
> 
> if (threadNode.eventSent && (threadNode.size <= size) &&
> 
>         status == epicsEventOK)
> 
>         return threadNode.size;
> 
>     return -1;
> 
>  
> 
> So it can return -1 if the allocated size for the message is wrong, but I believe that is impossible in this case.
> 
>  
> 
> It can fail if status is not epicsEventOK, which means epicsEventWaitWithTimeout returned something other than epicsEventOK, i.e. timeout.
> 
>  
> 
> I am not sure when threadNode.evenSent would be null.

It looks like door number three.  I'm not sure how the eventSent flag is meant to be used,
but your events are being lost when the epicsEvent is signaled and it is not set.

> $ gdb --args ./testMessageQueue 200 0.1
> (gdb) b osdMessageQueue.cpp:358 if status==0
> (gdb) r
... wait until breakpoint hit
> (gdb) p status
> $1 = epicsEventOK
> (gdb) p threadNode.size <= size
> $2 = true
> (gdb) p threadNode.eventSent
> $3 = false