Add unused headers check to CI

.gitlab-ci.yml

@@ -466,6 +466,7 @@ misc:
     - sh util/check-win32util-configure
     - sh util/check-categories.sh
     - if git grep SYSTEMTESTTOP -- ':!.gitlab-ci.yml'; then echo 'Please use relative paths instead of $SYSTEMTESTTOP.'; exit 1; fi
+    - bash util/unused-headers.sh
   needs: []
   artifacts:
     paths:

util/copyrights

@@ -2193,6 +2193,7 @@
 ./util/run-clang-tidy				X	2020
 ./util/spacewhack.pl				PERL	2000,2001,2004,2007,2012,2016,2018,2019,2020
 ./util/tabify-changes				SH	2004,2007,2012,2016,2018,2019,2020
+./util/unused-headers.sh			SH	2020
 ./util/update-drafts.pl				PERL	2000,2001,2004,2007,2012,2016,2018,2019,2020
 ./util/update_branches				PERL	2005,2007,2012,2016,2018,2019,2020
 ./util/update_copyrights			PERL	1998,1999,2000,2001,2004,2005,2006,2007,2008,2009,2010,2012,2013,2014,2015,2016,2017,2018,2019,2020

util/unused-headers.sh

@@ -0,0 +1,29 @@
+#!/bin/bash
+#
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, you can obtain one at https://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+unused_headers=$(
+	git ls-files -- '*.h' ':!:*include*' ':!:*rdata*' ':!:*win32*' |
+	sed 's|.*/\(.*\.h\)|\1|' |
+	while read -r header; do
+		git grep -q "#include \".*${header}\"" || echo "${header}"
+	done
+
+	git ls-files -- '*include/*.h' |
+	sed 's|.*/include\/\(.*\.h\)|\1|' |
+	while read -r header; do
+		git grep -q "#include <${header}>" || echo "${header}"
+	done
+)
+
+if [ -n "${unused_headers}" ]; then
+	echo -e "Following headers are unused:\n${unused_headers}"
+	exit 1
+fi