tests: Add fuzzing harness for functions/classes in flatfile.h

Author: practicalswift

src/Makefile.test.include

@@ -35,6 +35,7 @@ FUZZ_TARGETS = \
   test/fuzz/fee_rate \
   test/fuzz/fee_rate_deserialize \
   test/fuzz/flat_file_pos_deserialize \
+  test/fuzz/flatfile \
   test/fuzz/float \
   test/fuzz/hex \
   test/fuzz/integer \
@@ -480,6 +481,12 @@ test_fuzz_flat_file_pos_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_flat_file_pos_deserialize_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_flat_file_pos_deserialize_SOURCES = $(FUZZ_SUITE) test/fuzz/deserialize.cpp
 
+test_fuzz_flatfile_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_flatfile_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_flatfile_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_flatfile_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_flatfile_SOURCES = $(FUZZ_SUITE) test/fuzz/flatfile.cpp
+
 test_fuzz_float_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 test_fuzz_float_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_float_LDADD = $(FUZZ_SUITE_LD_COMMON)

src/test/fuzz/flatfile.cpp

@@ -0,0 +1,30 @@
+// 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 <flatfile.h>
+#include <optional.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cassert>
+#include <cstdint>
+#include <string>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+    Optional<FlatFilePos> flat_file_pos = ConsumeDeserializable<FlatFilePos>(fuzzed_data_provider);
+    if (!flat_file_pos) {
+        return;
+    }
+    Optional<FlatFilePos> another_flat_file_pos = ConsumeDeserializable<FlatFilePos>(fuzzed_data_provider);
+    if (another_flat_file_pos) {
+        assert((*flat_file_pos == *another_flat_file_pos) != (*flat_file_pos != *another_flat_file_pos));
+    }
+    (void)flat_file_pos->ToString();
+    flat_file_pos->SetNull();
+    assert(flat_file_pos->IsNull());
+}