Shamelessly copy Josiah

source/lib/json/tests/thirdparty/Fuzzer/test/StrncmpOOBTest.cpp

@@ -0,0 +1,21 @@
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+
+// Test that libFuzzer itself does not read out of bounds.
+#include <assert.h>
+#include <cstdint>
+#include <cstring>
+#include <cstdlib>
+#include <cstddef>
+#include <iostream>
+
+static volatile int Sink;
+
+extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  if (Size < 5) return 0;
+  const char *Ch = reinterpret_cast<const char *>(Data);
+  if (Ch[Size - 3] == 'a')
+    Sink = strncmp(Ch + Size - 3, "abcdefg", 6);
+  return 0;
+}
+