Found here at ESS:
(all in one line)
EPICS_CA_ADDR_LIST=averylonghostname.mylabnetwork.technicalnetwork.example.com
EPICS_CA_AUTO_ADDR_LIST=NO
caget somePVnam
leads to something like this:
CA.Client.Exception...............................................
Warning: "Empty PV search address list"
Source File: ../udpiiu.cpp line 403
Current Time: Thu Jun 09 2022 10:10:47.804161447
Problem desription:
addAddrToChannelAccessAddressList() will collect what ever we specify in
EPICS_CA_ADDR_LIST for channel access.
That function will add IP-addresses to the search list.
hostnames are possible, but are ignored if longer than 32 bytes,
because buf is too short.
If a hostname can be resolved into an IP, that is fine,
if not that is "fine as well" (better say: silently ignored):
If, and only if, EPICS_CA_AUTO_ADDR_LIST=NO is given then the one
and only too long hostname will be ignored and lead to an
"Empty PV search address list".
If EPICS_CA_AUTO_ADDR_LIST=YES (or nothing) is specified, the search list
is not empty, and EPICS will search all broadcast addresses.
This will eventually lead into a timout.
Solution:
Increase the buf size in addAddrToChannelAccessAddressList() from 32 to 256
The maximum length for a hostname is 255:
https://www.ietf.org/rfc/rfc1034.txt
If we add one byte for the string terminating '\0', we need 256 bytes.
And yes, this patch neglets the fact that a user can specify HOSTNAME:PORT,
which may need another 6 bytes. To put it the other way around:
In this case the hostname length is limited to 250 bytes,
which is still long enough in practice.
libCa shouldn't cause an application to abort with an uncaught
exception on a machine that has timezone problems just because
we can't convert the current time into a string.
The other Perl scripts that use FindBin for their lib path could
have the same changes applied, but these two scripts are the ones
normally run by hand so might get soft-linked by an installer.
Without this change these scripts don't actually work if run from
a soft-link instead of directly.
* CPP's defined() is UB outside of a #if line
* Use (void)! cast to prevent recent GCCs & glibc from warning
about ignoring the return status from chdir()
caProto.h was using IPPORT_USERRESERVED but not including itself,
meaning there was an order dependency of header inclusion when using
this header. Now there shouldn't be.
Also, RTEMS wasn't defining IPPORT_USERRESERVED, so that definition
has been added.
In some cases the license-identification header was missing,
so I added that as well. Replaced the remaining headers that
specifically identified "Versions 3.13.7 and higher".
Makefiles and the build system were deliberately excluded.
Use the pre-expanded Perl configuration variables.
Conda builds of Perl need these (and a fix to the Perl
config files, see https://github.com/conda/conda/issues/8425
for details).
When using an EPICS 7 softIoc.dbd file with a PV from an older version
of Base which didn't have all the fields, our attempts to read those
fields will time out, but the internal logic was buggy. Don't try to
print the values of timed out fields at all. The user will still see a
warning about connection timeouts at the top.
