Linker complains about missing virtual table
============================================

   "I'm getting a message complaining about an undefined virtual table.
Is this a compiler bug?"

   (On platforms that run neither collect nor the GNU linker, like
Solaris, you may see an odd undefined symbol like "_vt.3foo", where foo
is a class name).

   This is probably because you are missing a definition for the first
(non-inline) virtual function of the class.  Since gcc-2.7.0, g++ uses
a trick borrowed from cfront: the .o file containing the definition for
the first non-inline virtual function for the class will also contain
the virtual function table.