Yet again abusing my blog to store random software development notes,
readelf is a linux command that dumps information about ELF-format object files (e.g. .so libraries). Just pipe it into a temp file using e.g.
readelf ~/maya/2008.cg/plugins/HairDynamics.so > out
and search for the unfiltered symbol you want to examine using your favorite text editor/grepper. This will produce a line similar to:
r19: 00000000 0 NOTYPE GLOBAL DEFAULT UND _ZN2My5Library10FileWriter4
which in this case means the particular My::Library::FileWriter is UNDefined. Highly useful when messing around with link/runtime shared object errors.