Compiling tcpdump 4.0.0 without ipv6 - linking against ipv6less
libpcap too - generates the following error:

print-enc.o: In function `enc_if_print':
print-enc.c:(.text+0xce): undefined reference to `ip6_print'
collect2: ld returned 1 exit status
make: *** [tcpdump] Error 1

--- tcpdump/print-enc.c.orig	2008-09-01 04:44:22 +0200
+++ tcpdump/print-enc.c	2008-11-11 14:48:00 +0100
@@ -77,9 +77,11 @@
 	case AF_INET:
 		ip_print(gndo, p, length);
 		break;
+#ifdef INET6
 	case AF_INET6:
 		ip6_print(p, length);
 		break;
+#endif
 	}

 out: