We have a distributed application containing C++ and Java modules, interacting via CORBA.
Are there any C++ libraries/tools for exposing "variables" and "methods" to JMX tools (to create unified management) ?
So even though your application is C++ and Java, you're only looking to expose C++ module attributes to the JMX manager ?
If so, or actually, even if you are exposing both, I would look at using an SNMP library for both instances, since trying to get C++ to support JMX directly could be hairy. JMX and SNMP are broadly interoperable, I am pretty sure you can find SNMP libraries for your C++ components (and I know you can for Java) and you may as well stick to one protocol rather than have one for C++ and one for Java.
The last piece (and probably the easiest) is to find an SNMP "bridge" for your JMX console, manager or whatever you're using.