build: Add format string linter

This linter checks that the number of arguments passed to each variadic format
string function matches the number of format specifiers in the format string.

test/lint/lint-format-strings.sh

@@ -0,0 +1,40 @@
+#!/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.
+#
+# Lint format strings: This program checks that the number of arguments passed
+# to a variadic format string function matches the number of format specifiers
+# in the format string.
+
+export LC_ALL=C
+
+FUNCTION_NAMES_AND_NUMBER_OF_LEADING_ARGUMENTS=(
+    FatalError,0
+    fprintf,1
+    LogConnectFailure,1
+    LogPrint,1
+    LogPrintf,0
+    printf,0
+    snprintf,2
+    sprintf,1
+    strprintf,0
+    vfprintf,1
+    vprintf,1
+    vsnprintf,1
+    vsprintf,1
+)
+
+EXIT_CODE=0
+if ! python3 -m doctest test/lint/lint-format-strings.py; then
+    EXIT_CODE=1
+fi
+for S in "${FUNCTION_NAMES_AND_NUMBER_OF_LEADING_ARGUMENTS[@]}"; do
+    IFS="," read -r FUNCTION_NAME SKIP_ARGUMENTS <<< "${S}"
+    mapfile -t MATCHING_FILES < <(git grep --full-name -l "${FUNCTION_NAME}" -- "*.c" "*.cpp" "*.h" | sort | grep -vE "^src/(leveldb|secp256k1|tinyformat|univalue)")
+    if ! test/lint/lint-format-strings.py --skip-arguments "${SKIP_ARGUMENTS}" "${FUNCTION_NAME}" "${MATCHING_FILES[@]}"; then
+        EXIT_CODE=1
+    fi
+done
+exit ${EXIT_CODE}