Index: bin/hdrtest/Makefile
===================================================================
--- /dev/null
+++ bin/hdrtest/Makefile
@@ -0,0 +1,46 @@
+#
+# A number of header files in sys/* have, going back to 7th Edition Unix in
+# 1979, reqiured other files (like sys/types.h) to compile. Likewise the 4BSD
+# networking code has had prerequisites. However, going back to around the turn
+# of the century, other systems have made them be independently includable
+# (wide-spread header include protection post-dates 7th edition Unix by maybe 4
+# or 5 years judging from netnews sources). Start down the path of making them
+# all independently includable by creating this test that fails buildworld when
+# they are not.
+#
+PROG=	hdrtest
+SRCS=	hdrtest.c
+INTERNALPROG=	This is a compile-only test
+MAN=
+HDRS!=	(cd ${SRCTOP}/sys; ls sys/*.h net*/*.h)
+
+# Some files have to be clean for extra defines too...
+#CFLAGS.event.c=	-D_WANT_KEVENT32 -D_WANT_FREEBSD11_KEVENT
+
+.include "badfiles.inc"
+
+.for h in ${HDRS}
+.if !${BADHDRS:M${h}}
+SRCS+=	${h:R}.c
+CLEANFILES+=${h:R}.c
+${h:R}.c:
+	echo "#include <$h>" > ${.TARGET}
+.endif
+.endfor
+
+#
+# Target to make the current known bad list. In general, this list should only
+# ever shrink and never grow.
+#
+badfiles.inc!
+	@(cd ${SRCTOP}/sys;							\
+	echo "# DO NOT EDIT-- this file is automatically @""generated.";	\
+	echo "BADHDRS= \\";							\
+	for i in sys/*.h net*/*.h; do						\
+		echo "#include <$$i>" |						\
+			${CC} ${CFLAGS} -xc - -c -o /dev/null 2> /dev/null ||	\
+			echo "	$$i \\";					\
+	done;									\
+	echo) > ${.CURDIR}/badfiles.inc
+
+.include <bsd.prog.mk>
Index: bin/hdrtest/badfiles.inc
===================================================================
--- /dev/null
+++ bin/hdrtest/badfiles.inc
@@ -0,0 +1,376 @@
+# DO NOT EDIT-- this file is automatically @generated.
+BADHDRS= \
+	sys/_atomic64e.h \
+	sys/_atomic_subword.h \
+	sys/_blockcount.h \
+	sys/_callout.h \
+	sys/_endian.h \
+	sys/_ffcounter.h \
+	sys/_lock.h \
+	sys/_lockmgr.h \
+	sys/_mutex.h \
+	sys/_pctrie.h \
+	sys/_rangeset.h \
+	sys/_rmlock.h \
+	sys/_rwlock.h \
+	sys/_semaphore.h \
+	sys/_seqc.h \
+	sys/_sigset.h \
+	sys/_smr.h \
+	sys/_sockaddr_storage.h \
+	sys/_stack.h \
+	sys/_stdint.h \
+	sys/_sx.h \
+	sys/_task.h \
+	sys/_ucontext.h \
+	sys/_unrhdr.h \
+	sys/aac_ioctl.h \
+	sys/acct.h \
+	sys/agpio.h \
+	sys/alq.h \
+	sys/apm.h \
+	sys/ata.h \
+	sys/atomic_common.h \
+	sys/atomic_san.h \
+	sys/backlight.h \
+	sys/bio.h \
+	sys/bitstring.h \
+	sys/blist.h \
+	sys/buf.h \
+	sys/buf_ring.h \
+	sys/bus.h \
+	sys/bus_dma.h \
+	sys/bus_dma_internal.h \
+	sys/bus_san.h \
+	sys/busdma_bufalloc.h \
+	sys/callout.h \
+	sys/caprights.h \
+	sys/cdrio.h \
+	sys/cfictl.h \
+	sys/conf.h \
+	sys/cons.h \
+	sys/copyright.h \
+	sys/counter.h \
+	sys/coverage.h \
+	sys/cpu.h \
+	sys/cpuctl.h \
+	sys/cpuset.h \
+	sys/devctl.h \
+	sys/devmap.h \
+	sys/disk_zone.h \
+	sys/diskmbr.h \
+	sys/domain.h \
+	sys/domainset.h \
+	sys/dtrace_bsd.h \
+	sys/dvdio.h \
+	sys/efi.h \
+	sys/efiio.h \
+	sys/elf32.h \
+	sys/elf64.h \
+	sys/elf_common.h \
+	sys/elf_generic.h \
+	sys/epoch.h \
+	sys/eui64.h \
+	sys/eventhandler.h \
+	sys/eventvar.h \
+	sys/exec.h \
+	sys/extattr.h \
+	sys/fail.h \
+	sys/filedesc.h \
+	sys/firmware.h \
+	sys/fnv_hash.h \
+	sys/font.h \
+	sys/gmon.h \
+	sys/gpio.h \
+	sys/gpt.h \
+	sys/gtaskqueue.h \
+	sys/hhook.h \
+	sys/iconv.h \
+	sys/imgact.h \
+	sys/imgact_aout.h \
+	sys/imgact_elf.h \
+	sys/interrupt.h \
+	sys/intr.h \
+	sys/ioctl_compat.h \
+	sys/iov.h \
+	sys/iov_schema.h \
+	sys/ipmi.h \
+	sys/jail.h \
+	sys/kdb.h \
+	sys/kernel.h \
+	sys/khelp.h \
+	sys/kobj.h \
+	sys/ksem.h \
+	sys/ktls.h \
+	sys/ktrace.h \
+	sys/libkern.h \
+	sys/link_aout.h \
+	sys/linker.h \
+	sys/linker_set.h \
+	sys/lock.h \
+	sys/lock_profile.h \
+	sys/lockf.h \
+	sys/lockmgr.h \
+	sys/loginclass.h \
+	sys/mac.h \
+	sys/mbuf.h \
+	sys/md4.h \
+	sys/md5.h \
+	sys/mdioctl.h \
+	sys/memdesc.h \
+	sys/memrange.h \
+	sys/module.h \
+	sys/module_khelp.h \
+	sys/mpt_ioctl.h \
+	sys/msgbuf.h \
+	sys/mutex.h \
+	sys/namei.h \
+	sys/osd.h \
+	sys/pciio.h \
+	sys/pctrie.h \
+	sys/physmem.h \
+	sys/pipe.h \
+	sys/pmc.h \
+	sys/pmckern.h \
+	sys/pmclog.h \
+	sys/posix4.h \
+	sys/power.h \
+	sys/priority.h \
+	sys/prng.h \
+	sys/proc.h \
+	sys/qmath.h \
+	sys/racct.h \
+	sys/refcount.h \
+	sys/resourcevar.h \
+	sys/rman.h \
+	sys/rmlock.h \
+	sys/rtprio.h \
+	sys/runq.h \
+	sys/rwlock.h \
+	sys/sbuf.h \
+	sys/sema.h \
+	sys/sf_buf.h \
+	sys/sglist.h \
+	sys/sigio.h \
+	sys/signalvar.h \
+	sys/smr.h \
+	sys/smr_types.h \
+	sys/socketvar.h \
+	sys/sockopt.h \
+	sys/stack.h \
+	sys/stats.h \
+	sys/sx.h \
+	sys/syscallsubr.h \
+	sys/syslimits.h \
+	sys/systm.h \
+	sys/taskqueue.h \
+	sys/terminal.h \
+	sys/termios.h \
+	sys/tiio.h \
+	sys/timeb.h \
+	sys/timeet.h \
+	sys/timeffc.h \
+	sys/timepps.h \
+	sys/timetc.h \
+	sys/ttydevsw.h \
+	sys/ttydisc.h \
+	sys/ttyhook.h \
+	sys/ttyqueue.h \
+	sys/umtx.h \
+	sys/unpcb.h \
+	sys/user.h \
+	sys/uuid.h \
+	sys/vdso.h \
+	sys/vmmeter.h \
+	sys/vnode.h \
+	sys/vtoc.h \
+	net/bpf.h \
+	net/bpf_buffer.h \
+	net/bpf_jitter.h \
+	net/bpf_zerocopy.h \
+	net/bpfdesc.h \
+	net/bridgestp.h \
+	net/debugnet_int.h \
+	net/ethernet.h \
+	net/firewire.h \
+	net/if_arp.h \
+	net/if_bridgevar.h \
+	net/if_dl.h \
+	net/if_enc.h \
+	net/if_lagg.h \
+	net/if_llatbl.h \
+	net/if_llc.h \
+	net/if_media.h \
+	net/if_mib.h \
+	net/if_pflog.h \
+	net/if_pfsync.h \
+	net/if_sppp.h \
+	net/if_tap.h \
+	net/if_tun.h \
+	net/if_var.h \
+	net/if_vlan_var.h \
+	net/iflib.h \
+	net/iflib_private.h \
+	net/ifq.h \
+	net/mp_ring.h \
+	net/mppc.h \
+	net/netisr.h \
+	net/netisr_internal.h \
+	net/netmap.h \
+	net/netmap_legacy.h \
+	net/paravirt.h \
+	net/pfil.h \
+	net/pfkeyv2.h \
+	net/pfvar.h \
+	net/radix.h \
+	net/raw_cb.h \
+	net/rndis.h \
+	net/route.h \
+	net/rss_config.h \
+	net/slcompress.h \
+	net/toeplitz.h \
+	net80211/_ieee80211.h \
+	net80211/ieee80211.h \
+	net80211/ieee80211_action.h \
+	net80211/ieee80211_adhoc.h \
+	net80211/ieee80211_ageq.h \
+	net80211/ieee80211_alq.h \
+	net80211/ieee80211_amrr.h \
+	net80211/ieee80211_crypto.h \
+	net80211/ieee80211_dfs.h \
+	net80211/ieee80211_freebsd.h \
+	net80211/ieee80211_hostap.h \
+	net80211/ieee80211_ht.h \
+	net80211/ieee80211_input.h \
+	net80211/ieee80211_ioctl.h \
+	net80211/ieee80211_mesh.h \
+	net80211/ieee80211_monitor.h \
+	net80211/ieee80211_node.h \
+	net80211/ieee80211_power.h \
+	net80211/ieee80211_proto.h \
+	net80211/ieee80211_radiotap.h \
+	net80211/ieee80211_ratectl.h \
+	net80211/ieee80211_rssadapt.h \
+	net80211/ieee80211_scan.h \
+	net80211/ieee80211_scan_sw.h \
+	net80211/ieee80211_sta.h \
+	net80211/ieee80211_superg.h \
+	net80211/ieee80211_tdma.h \
+	net80211/ieee80211_var.h \
+	net80211/ieee80211_vht.h \
+	net80211/ieee80211_wds.h \
+	netgraph/netgraph.h \
+	netgraph/ng_async.h \
+	netgraph/ng_bpf.h \
+	netgraph/ng_bridge.h \
+	netgraph/ng_car.h \
+	netgraph/ng_checksum.h \
+	netgraph/ng_cisco.h \
+	netgraph/ng_deflate.h \
+	netgraph/ng_etf.h \
+	netgraph/ng_hole.h \
+	netgraph/ng_ksocket.h \
+	netgraph/ng_l2tp.h \
+	netgraph/ng_lmi.h \
+	netgraph/ng_macfilter.h \
+	netgraph/ng_message.h \
+	netgraph/ng_mppc.h \
+	netgraph/ng_nat.h \
+	netgraph/ng_one2many.h \
+	netgraph/ng_parse.h \
+	netgraph/ng_patch.h \
+	netgraph/ng_pipe.h \
+	netgraph/ng_ppp.h \
+	netgraph/ng_pppoe.h \
+	netgraph/ng_pptpgre.h \
+	netgraph/ng_pred1.h \
+	netgraph/ng_sample.h \
+	netgraph/ng_socket.h \
+	netgraph/ng_socketvar.h \
+	netgraph/ng_source.h \
+	netgraph/ng_tag.h \
+	netgraph/ng_tcpmss.h \
+	netgraph/ng_tee.h \
+	netgraph/ng_vjc.h \
+	netgraph/ng_vlan.h \
+	netgraph/ng_vlan_rotate.h \
+	netgraph/qos.h \
+	netinet/dccp.h \
+	netinet/icmp6.h \
+	netinet/icmp_var.h \
+	netinet/if_ether.h \
+	netinet/igmp.h \
+	netinet/igmp_var.h \
+	netinet/in_fib.h \
+	netinet/in_kdtrace.h \
+	netinet/in_pcb.h \
+	netinet/in_rss.h \
+	netinet/in_systm.h \
+	netinet/in_var.h \
+	netinet/ip.h \
+	netinet/ip6.h \
+	netinet/ip_carp.h \
+	netinet/ip_dummynet.h \
+	netinet/ip_fw.h \
+	netinet/ip_icmp.h \
+	netinet/ip_mroute.h \
+	netinet/ip_options.h \
+	netinet/ip_var.h \
+	netinet/pim_var.h \
+	netinet/sctp_auth.h \
+	netinet/sctp_bsd_addr.h \
+	netinet/sctp_kdtrace.h \
+	netinet/sctp_os.h \
+	netinet/sctp_os_bsd.h \
+	netinet/sctp_pcb.h \
+	netinet/sctp_structs.h \
+	netinet/sctp_sysctl.h \
+	netinet/tcp_debug.h \
+	netinet/tcp_hpts.h \
+	netinet/tcp_log_buf.h \
+	netinet/tcp_lro.h \
+	netinet/tcp_offload.h \
+	netinet/tcp_pcap.h \
+	netinet/tcp_ratelimit.h \
+	netinet/tcp_var.h \
+	netinet/tcpip.h \
+	netinet/toecore.h \
+	netinet/udp.h \
+	netinet/udp_var.h \
+	netinet/udplite.h \
+	netinet6/icmp6.h \
+	netinet6/in6.h \
+	netinet6/in6_fib.h \
+	netinet6/in6_rss.h \
+	netinet6/in6_var.h \
+	netinet6/ip6.h \
+	netinet6/ip6_mroute.h \
+	netinet6/ip6_var.h \
+	netinet6/ip6protosw.h \
+	netinet6/ip_fw_nat64.h \
+	netinet6/ip_fw_nptv6.h \
+	netinet6/mld6.h \
+	netinet6/mld6_var.h \
+	netinet6/nd6.h \
+	netinet6/pim6.h \
+	netinet6/pim6_var.h \
+	netinet6/raw_ip6.h \
+	netinet6/send.h \
+	netipsec/ah.h \
+	netipsec/ah_var.h \
+	netipsec/esp.h \
+	netipsec/esp_var.h \
+	netipsec/ipcomp.h \
+	netipsec/ipcomp_var.h \
+	netipsec/ipsec.h \
+	netipsec/ipsec6.h \
+	netipsec/key_debug.h \
+	netipsec/keysock.h \
+	netipsec/xform.h \
+	netsmb/netbios.h \
+	netsmb/smb.h \
+	netsmb/smb_conn.h \
+	netsmb/smb_rq.h \
+	netsmb/smb_subr.h \
+	netsmb/smb_tran.h \
+