Experimental Physics and
Industrial Control System

Till Straumann <[email protected]> · Fri, 13 Feb 2004 16:34:19 -0800

Hi Ben.
Benjamin Franksen wrote:

Hello,
I have a simple question regarding the CA client library: which is the
guaranteed live span of the data ointed to by the void pointer argument
received by a CA event handler routine?

Don't know if I understand you correctly - do you mean the 'dbr' field of
the event_handler_args structure (which itself is passed by value)?
If you do, then after browsing the source for 2min, it seems to me that
what you get is a pointer to a message buffer which is very probably
volatile, i.e. it would surprise me if it would be safe to use it after
the callback returns.
These are just my 2 cents - someone with deeper knowledge might have
to correct me...
-- Till

More specifically: does this pointer change from call(-back) to call(-back) or
does it always refer to the same memory location? (It could of course be
anything in between).
The reason I ask is that (1) i'd like to know if there are any conditions
under which it is safe to store the pointer for later access and (2) i
couldn't find any hint on this in the CA reference manual.
Ben

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System