Add a small tool to find conflicting filenames

When building Kaleidoscope, the compiled object files are linked together into a
static archive. This static archive has a very simple structure, and only stores
filenames, not paths, not even relative ones. As such, we can't have files with
the same name, because they will conflict, and one will override the other.

To avoid this situation, this script will find all cpp source files (we don't
need to care about header-only things, those do not result in an object file),
and will comb through them to find conflicting filenames.

If a conflict is found, it will print all files that share the name, and will
exit with an error at the end. It does not exit at the first duplicate, but will
find and print all of them.

If no conflict is found, the script just prints its status message and exits
with zero.

This addresses the bulk of #850.

Signed-off-by: Gergely Nagy <algernon@keyboard.io>

bin/find-duplicate-cpp-files

@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+# find-duplicate-cpp-files - Finds duplicate cpp files
+# Copyright (C) 2020  Keyboard.io, Inc.
+#
+# This program is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation, version 3.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program. If not, see <http://www.gnu.org/licenses/>.
+
+## When building Kaleidoscope, the compiled object files are linked together
+## into a static archive. This static archive has a very simple structure, and
+## only stores filenames, not paths, not even relative ones. As such, we can't
+## have files with the same name, because they will conflict, and one will
+## override the other.
+##
+## To avoid this situation, this script will find all cpp source files (we don't
+## need to care about header-only things, those do not result in an object
+## file), and will comb through them to find conflicting filenames.
+##
+## If a conflict is found, it will print all files that share the name, and will
+## exit with an error at the end. It does not exit at the first duplicate, but
+## will find and print all of them.
+##
+## If no conflict is found, the script just prints its status message and exits
+## with zero.
+
+set -e
+
+FILE_LIST="$(find src -name '*.cpp' | sed -e 's,\(\(.*\)/\([^/]*\)\),\3 \1,')"
+
+exit_code=0
+
+echo -n "Looking for conflicting filenames... "
+
+for f in $(echo "${FILE_LIST}" | cut -f1 -d" "); do
+    count=$(echo "${FILE_LIST}" | grep -c "^${f}")
+    if [ "$count" -gt 1 ]; then
+        echo >&2
+        echo " Duplicate found for ${f}: " >&2
+        echo "${FILE_LIST}" | grep "${f}" | cut -d" " -f2 | sed -e 's,^,   ,' >&2
+        exit_code=1
+    fi
+done
+
+if [ "${exit_code}" -eq 0 ]; then
+    echo "done."
+fi
+
+exit ${exit_code}