If you own a compiler which produces symbolic information in an unsupported format you can modify yourself to support it. For a model of how to do this look for setsym() and mwsetsym() in the file adb1.c. Both of them call addsym() which performs an actual insertion of a new symbol and its value into a linked list of supported symbols. A current version of addsym() will handle symbol names of any length but internally they will be chopped off to something not longer than the current value of the global variable swidth. Ensure that this value is set properly for your needs.
The mechanism above can be easily extended to allow reading some symbols and their values from a user suplied text file. Some may find it very handy. The current version of does not support this feature. It is possible to roll your own if you really need it.