> |Undefined                       first referenced
> | symbol                             in file
> |__builtin_va_arg_incr               libruby.a(eval.o)
> |ld: fatal: Symbol referencing errors. No output written to miniruby
> |make: *** [miniruby] Error 1

I remember getting this bug a few years ago because we were using GNU
headers with SUN libraries or SUN headers with GNU libraries. It had to do
with a macro definition. 

matju