Tools to check for config-dependent symbol sets?

[Stephen Satchell]

Before I start thinking how to design a tool to deal with 
highly-configurable software like the Linux kernel, I thought I'd ask 
first.  Does anyone know of any tools to determine if a symbol is undefined 
or multiply-defined for a given combination of <n> configuration variables 
without having to actually perform 2**n compilations?

Satch