dirdiff is an awesome little tool. Now that Tiger has Wish 8.4 with the native Aqua GUI elements in it, I had to see how it would run. After a little bump getting the filecmp.c to compile, it works wonderfully. Nothing too complex, just a couple tweaks to the Makefile to handle the mac-isms. Here is the patch just in case you want to get it working for yourself.
diff -urN dirdiff-2.1/Makefile dirdiff-2.1-new/Makefile --- dirdiff-2.1/Makefile 2005-04-19 05:22:01.000000000 -0500 +++ dirdiff-2.1-new/Makefile 2005-11-27 11:45:02.000000000 -0600 @@ -7,12 +7,12 @@ INSTALL=install # You may need to change the -I arguments depending on your system -CFLAGS=-O3 -I/usr/include/tcl8.3/ -I/usr/include/tcl +CFLAGS=-O3 -framework Tcl all: libfilecmp.so.0.0 libfilecmp.so.0.0: filecmp.c - $(CC) $(CFLAGS) -shared -o $@ filecmp.c + $(CC) $(CFLAGS) -dynamiclib -o $@ filecmp.c install: dirdiff libfilecmp.so.0.0 $(INSTALL) -c dirdiff $(BINDIR)