tools: New script to check magic numbers

Only from a git clone, and only from the root directory, which should
leave alone distcheck and builds from release archives.

tools/magic_check.sh

+#!/bin/sh
+#
+# Copyright (c) 2021 Varnish Software AS
+# All rights reserved.
+#
+# Author: Dridi Boukelmoune <dridi.boukelmoune@gmail.com>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+# Check that all magic numbers are declared as:
+#
+# - 0x00112233	(most magic numbers)
+# - 0x00	(where size matters)
+
+set -e
+set -u
+
+ROOT=$(git rev-parse --show-cdup 2>/dev/null) || exit 77
+test -z "$ROOT" || exit 77
+
+git grep -h '^#define \w*_MAGIC' |
+sed 's/\\t/\t/g' |
+awk '{print $3}' |
+tr '[:upper:]' '[:lower:]' |
+sort |
+uniq -c |
+sort |
+awk '$1 != 1 || $2 !~ /^0x[[:xdigit:]]*$/ || length($2) !~ /^(4|10)$/' |
+while read -r COUNT MAGIC
+do
+	if [ $COUNT -eq 1 ]
+	then
+		echo "Invalid magic number:"
+	else
+		echo "Duplicate magic number:"
+	fi
+	git grep -ih '^#define \w*_MAGIC\s*'$MAGIC
+	echo
+	false # propagate non-zero exit status
+done