Add regression test: Don't assert(...) with side effects

test/lint/lint-assertions.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+#
+# Copyright (c) 2018 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+#
+# Check for assertions with obvious side effects.
+
+export LC_ALL=C
+
+EXIT_CODE=0
+
+# PRE31-C (SEI CERT C Coding Standard):
+# "Assertions should not contain assignments, increment, or decrement operators."
+OUTPUT=$(git grep -E '[^_]assert\(.*(\+\+|\-\-|[^=!<>]=[^=!<>]).*\);' -- "*.cpp" "*.h")
+if [[ ${OUTPUT} != "" ]]; then
+    echo "Assertions should not have side effects:"
+    echo
+    echo "${OUTPUT}"
+    EXIT_CODE=1
+fi
+
+exit ${EXIT_CODE}