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

src/Makefile.test.include

@@ -28,6 +28,7 @@ FUZZ_TARGETS = \
   test/fuzz/bloom_filter \
   test/fuzz/bloomfilter_deserialize \
   test/fuzz/chain \
+  test/fuzz/checkqueue \
   test/fuzz/coins_deserialize \
   test/fuzz/decode_tx \
   test/fuzz/descriptor_parse \
@@ -431,6 +432,12 @@ test_fuzz_chain_LDADD = $(FUZZ_SUITE_LD_COMMON)
 test_fuzz_chain_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
 test_fuzz_chain_SOURCES = test/fuzz/chain.cpp
 
+test_fuzz_checkqueue_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
+test_fuzz_checkqueue_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
+test_fuzz_checkqueue_LDADD = $(FUZZ_SUITE_LD_COMMON)
+test_fuzz_checkqueue_LDFLAGS = $(RELDFLAGS) $(AM_LDFLAGS) $(LIBTOOL_APP_LDFLAGS)
+test_fuzz_checkqueue_SOURCES = test/fuzz/checkqueue.cpp
+
 test_fuzz_coins_deserialize_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES) -DCOINS_DESERIALIZE=1
 test_fuzz_coins_deserialize_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)
 test_fuzz_coins_deserialize_LDADD = $(FUZZ_SUITE_LD_COMMON)

src/test/fuzz/checkqueue.cpp

@@ -0,0 +1,65 @@
+// 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 <checkqueue.h>
+#include <optional.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace {
+struct DumbCheck {
+    const bool result = false;
+
+    DumbCheck() = default;
+
+    explicit DumbCheck(const bool _result) : result(_result)
+    {
+    }
+
+    bool operator()() const
+    {
+        return result;
+    }
+
+    void swap(DumbCheck& x)
+    {
+    }
+};
+} // namespace
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
+
+    const unsigned int batch_size = fuzzed_data_provider.ConsumeIntegralInRange<unsigned int>(0, 1024);
+    CCheckQueue<DumbCheck> check_queue_1{batch_size};
+    CCheckQueue<DumbCheck> check_queue_2{batch_size};
+    std::vector<DumbCheck> checks_1;
+    std::vector<DumbCheck> checks_2;
+    const int size = fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 1024);
+    for (int i = 0; i < size; ++i) {
+        const bool result = fuzzed_data_provider.ConsumeBool();
+        checks_1.emplace_back(result);
+        checks_2.emplace_back(result);
+    }
+    if (fuzzed_data_provider.ConsumeBool()) {
+        check_queue_1.Add(checks_1);
+    }
+    if (fuzzed_data_provider.ConsumeBool()) {
+        (void)check_queue_1.Wait();
+    }
+
+    CCheckQueueControl<DumbCheck> check_queue_control{&check_queue_2};
+    if (fuzzed_data_provider.ConsumeBool()) {
+        check_queue_control.Add(checks_2);
+    }
+    if (fuzzed_data_provider.ConsumeBool()) {
+        (void)check_queue_control.Wait();
+    }
+}