tests: Add fuzzing harness for AdditionOverflow(...)

src/test/fuzz/addition_overflow.cpp

@@ -0,0 +1,55 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+#if defined(__has_builtin)
+#if __has_builtin(__builtin_add_overflow)
+#define HAVE_BUILTIN_ADD_OVERFLOW
+#endif
+#elif defined(__GNUC__) && (__GNUC__ >= 5)
+#define HAVE_BUILTIN_ADD_OVERFLOW
+#endif
+
+namespace {
+template <typename T>
+void TestAdditionOverflow(FuzzedDataProvider& fuzzed_data_provider)
+{
+    const T i = fuzzed_data_provider.ConsumeIntegral<T>();
+    const T j = fuzzed_data_provider.ConsumeIntegral<T>();
+    const bool is_addition_overflow_custom = AdditionOverflow(i, j);
+#if defined(HAVE_BUILTIN_ADD_OVERFLOW)
+    T result_builtin;
+    const bool is_addition_overflow_builtin = __builtin_add_overflow(i, j, &result_builtin);
+    assert(is_addition_overflow_custom == is_addition_overflow_builtin);
+    if (!is_addition_overflow_custom) {
+        assert(i + j == result_builtin);
+    }
+#else
+    if (!is_addition_overflow_custom) {
+        (void)(i + j);
+    }
+#endif
+}
+} // namespace
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    TestAdditionOverflow<int64_t>(fuzzed_data_provider);
+    TestAdditionOverflow<uint64_t>(fuzzed_data_provider);
+    TestAdditionOverflow<int32_t>(fuzzed_data_provider);
+    TestAdditionOverflow<uint32_t>(fuzzed_data_provider);
+    TestAdditionOverflow<int16_t>(fuzzed_data_provider);
+    TestAdditionOverflow<uint16_t>(fuzzed_data_provider);
+    TestAdditionOverflow<char>(fuzzed_data_provider);
+    TestAdditionOverflow<unsigned char>(fuzzed_data_provider);
+    TestAdditionOverflow<signed char>(fuzzed_data_provider);
+}