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

Subject: Re: Problems with Alh & Channel Access (R3.13.0b4).
From: Jeff Hill <[email protected]>
To: Nick Patavalis <[email protected]>
Cc: [email protected]
Date: Mon, 03 Mar 1997 15:27:38 -0700
Nick Patavalis wrote:

> The crash happens durring the conversion from net to host
> format. Specifically when the "cac_dbr_cvrt[]" array is de-referenced
> and the outcome (function ptr) executed. When the crash happens the
> code reaches there with:
>         piiu->curMsg.m_type == 37
> Since there are but 34 function pointers in the  "cac_dbr_cvrt[]"
> array (as initialized in "convert.c"), crashing is unavoidable!

As Mark Rivers mentioned, there was a problem in R3.13 occurring
when all of the following were true (fixed in R3.13.beta5).
o IEEE native floating point format
o double precision operand
o little endian host
o source and destination address for conversion are identical

However, on the surface this does not appear to be the same 
problem because:
o The data item that is incorrect is a 16 bit unsigned integer
o Many other programs are working {medm, probe, ...} on this 
platform (and they use data type codes).
 
Possible causes of out of range data type code:
o some code is writing on the CA client's internal data structures
o CA protocol is being read missaligned. We have not seen this.
 
Causes we dont expect:
o ALH using the wrong data type code (this is checked by
the client lib and also by the server)
 
I dont have much to go on. Perhaps the floating point problem 
is causing corruption to occur (seems unlikely). 
 
We will need to reproduce the problem. Since I dont 
have a lynux system set up here perhaps you can provide
a remote login (and access to -g compiled object code).
 
Do the symptoms (location of the crash) change if you 
rearrange the configuration for ALH. Has anyone else used ALH
under lynux before?


> I just looked at the APS, WWW server, and the most recent release is
> R3.13.0beta6. I supose this won't do the trick....
> 

beta6 has the fix for the double precision/ieee/liddle endian
problem.

> I also wonder if there is any documention on channel access other than
> the the... elementary "channel access reference", which only contains a
> short description of the function calls. 

A CA tutorial that is less ... elementary is in the works :)

> Is there a Channel Access
> _Protocol_ reference? If so where I can look for it?

No such critter exists. Depending on funding, a simple protocol 
document may be a product of the design cycle for CA V4.

Jeff

-- 
______________________________________________________________________
Jeffrey O. Hill                 Internet        [email protected]
LANL MS H820                    Voice           505 665 1831
Los Alamos, NM 87545 USA        FAX             505 665 5107


Replies:
Re: Problems with Alh & Channel Access (R3.13.0b4). Nick Patavalis
References:
Problems with Alh & Channel Access (R3.13.0b4). Nick Patavalis

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