Experimental Physics and
Industrial Control System

Noboru Yamamoto <[email protected]> · Tue, 25 Jan 2000 09:55:32 +0900

Janousch Markus wrote:
> 
>   Sorry, for bothering you, but I have some problems compiling/running
> CaPython.
> 
> 1. It seems that you are running on a HP-machine because you are linking
> against      -lCompat in Epics. We are running Linux (Red Hat 5.2) here,
> so I don't need this library. I don't think this is the source of my
> problems.
On Linux platform,  lines in Setup.local looks like the following:

EPICS_BASE=/proj/epics/R313/base # you need to change this anyway.
#
_ca _ca.c -DUNIX -I/proj/local/$(ARCH)/include -I$(EPICS_BASE)/include -L$(EPICS_BASE\
)/lib/Linux  -lca -lAs -lCom -lDb

You need to change /proj/local/$(ARCH)/include appropriately.
> 
> 2. When linking I get an unresolved symbol
> > /home/local/janousch/Python-1.5.2/Modules/./_ca.c:1105: undefined reference to `ca_sock_id'
> I couldn't find any reference to the function ca_sock_id() in one of the
> Epics libraries. We are using Epics 3.13.0.beta12; can it be that you
> are using a more recent version of Epics/CA that has this function
> defined?
>
ca_sock_id() is itroduced to define Py_ca_fileno(). It is not a part of
the standard EPICS 
distribution.
You need to add the following two lines to $(EPICS)/base/src/cadef.h

#define ca_sock_id(CHID)                ca_sock_id_function(CHID)
epicsShareFunc READONLY int epicsShareAPI ca_sock_id_function ( chid channel);

and add the following definitions in $(EPICS)/base/src/caaccess.c

READONLY int epicsShareAPI ca_sock_id_function(chid chix)
{
        IIU     *piiu;

        piiu = chix->piiu;

        if(!piiu){
                return NULL;
        }
        return piiu->sock_chan;
}
> 
> Anyhow, I replaced the return value of the function by a fixed integer
> value, since I presume that the function Py_ca_fileno() that calls
> ca_sock_id() is not needed for a small test.
>

You need ca_sock_id/Py_ca_fileno when you wants write you own event loop
using 
select function call in a Python program. Otherwise you can commentout
this function. 

It may be better idea to register fd_manager after importing ca module. 

	def fdreg(uarg, fd, opend):
		if opened:
			print "fd %d was opened"%fd
		else:
			print "fd %d was closed"%fd
	uarg="any data for fdreg"

	import ca	
	ca.add_fd_registration(fdreg, uarg)

ca.add_fd_registation  will register a wrpper fd_registration fucntion using

ca_add_fd_registraion(wrap_fdreg,uarg);

where uarg will be a pointer to the PyObject which includes (fdreg,
uarg) pair.

wrap_fdreg() will evaluate Python object passed as  uarg. And evaluate
fdreg in
Python interpreter with file_descriptor, open/close flag and user argument.

If you have better idea, please let me know.

> 
> 3. Thus, when running ca_test.py with the newly built Python and I do
> not give a channel name as an argument a small window with a
> 'Quit'-button appears; looks fine for me. But giving a valid channel as
> an argument results in a core dump (segmentation fault). Before that
> happens a message is printed:
> > Acquire Lock No1
> and then the application dies.
I believe you build python build with "thread" support. 
Check Setup.thread in your Python/Modules directory.

Currently Python/CA does not work with Python-thread.
I'm very sorry about it. We are working on that without much success.

> 
>  Do you have any idea what I could be doing wrong? I built and tested on
> a Linux-PC running Red Hat 5.2. The compilation was done with gcc
> 2.7.2.3 and the Epics version used was 3.13.0.beta12. The Python version
> is 1.5.2 and it seems to run with the existing python-code I have.
>
We runs Python CA on 

HP-UX 10.20
OSF1 v4.0
Red Hat Linux release 6.1 , Kernel 2.2.12-20 on an i686

without Python-thead support.
> 
>   Thanks for any help,
>                       Markus
>
I'm very sorry about my poor documentation and source code preparation.
I greatly appriciate your comments.

Thanks.

Noboru

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System