xffm in HEAD uses -Wunused-function, -Wunused-label, -Wunused-value, and -Wunused-variable in some of its subdirectories' Makefiles. This results in the code not being compilable with gcc 2.95. Removing these flags from the Makefiles fixes the problem.
-Wunused* directives removed from makefiles
These flags reappared in the latest CVS. Are these things auto-generated?
The generation of makefiles is: Makefile.am -> Makefile.in -> Makefile, So that changing Makefile.am is enough. Perhaps your Makefiles have not been regenerated. Do a "make distclean && ./configure" to regenerated them. Maybe that's why you still have the flags.
I think xfdiff4's Makefile.am seems to not have the unused-* removed.
That is correct. I have now removed the flags from xfdiff makefiles at CVS.
Judging from the comments this should have been resolved as FIXED.