Issues with syslog on Raspbian using gnu c++ 11

Ok so I am having problems with syslog on Raspbian Stretch. I am trying to write to /var/log/blah.log using local0 as my facility. I am using gnu C++ 11 As the application is being written in C++ so I trying to create a logging class.

My /etc/syslog.conf has the following entry

local0.*    /var/log/blah.log

... and I have restarted the service and the Pi.

My code to open the log is as follows:

setlogmask(LOG_UPTO(LOG_DEBUG));
openlog(blah, LOG_PERROR | LOG_CONS | LOG_NDELAY, LOG_LOCAL0);

...and my logging code is:

syslog(LOG_INFO | LOG_LOCAL0, fullMessage.c_str());

There is no /var/log/blah.log file created and no log entries written, although the message is written to the console as I am using LOG_CONS.

If I replace LOG_LOCAL0 with LOG_USER I am successfully able write to user.log.

I do want to be able to write to the custom log file because: a) it is easy to ask a user to look at that file for debugging purposes b) it should work!!

As I have stated I have looked through the numerous posts on this site and others and still cannot get it top work so posting links to man pages and other articles won't help!