tests: add fuzz tests for VecDeque

2 files changed, 492 insertions, 0 deletions

diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index 742022ca93..8a638ec690 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -397,6 +397,7 @@ test_fuzz_fuzz_SOURCES = \
  test/fuzz/utxo_snapshot.cpp \
  test/fuzz/utxo_total_supply.cpp \
  test/fuzz/validation_load_mempool.cpp \
+ test/fuzz/vecdeque.cpp \
  test/fuzz/versionbits.cpp
 endif # ENABLE_FUZZ_BINARY
 
diff --git a/src/test/fuzz/vecdeque.cpp b/src/test/fuzz/vecdeque.cpp
new file mode 100644
index 0000000000..1d9a98931f
--- /dev/null
+++ b/src/test/fuzz/vecdeque.cpp
@@ -0,0 +1,491 @@
+// Copyright (c) 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 <span.h>
+#include <test/fuzz/util.h>
+#include <test/util/xoroshiro128plusplus.h>
+#include <util/vecdeque.h>
+
+#include <deque>
+#include <stdint.h>
+
+namespace {
+
+/** The maximum number of simultaneous buffers kept by the test. */
+static constexpr size_t MAX_BUFFERS{3};
+/** How many elements are kept in a buffer at most. */
+static constexpr size_t MAX_BUFFER_SIZE{48};
+/** How many operations are performed at most on the buffers in one test. */
+static constexpr size_t MAX_OPERATIONS{1024};
+
+/** Perform a simulation fuzz test on VecDeque type T.
+ *
+ * T must be constructible from a uint64_t seed, comparable to other T, copyable, and movable.
+ */
+template<typename T, bool CheckNoneLeft>
+void TestType(Span<const uint8_t> buffer, uint64_t rng_tweak)
+{
+    FuzzedDataProvider provider(buffer.data(), buffer.size());
+    // Local RNG, only used for the seeds to initialize T objects with.
+    XoRoShiRo128PlusPlus rng(provider.ConsumeIntegral<uint64_t>() ^ rng_tweak);
+
+    // Real circular buffers.
+    std::vector<VecDeque<T>> real;
+    real.reserve(MAX_BUFFERS);
+    // Simulated circular buffers.
+    std::vector<std::deque<T>> sim;
+    sim.reserve(MAX_BUFFERS);
+    // Temporary object of type T.
+    std::optional<T> tmp;
+
+    // Compare a real and a simulated buffer.
+    auto compare_fn = [](const VecDeque<T>& r, const std::deque<T>& s) {
+        assert(r.size() == s.size());
+        assert(r.empty() == s.empty());
+        assert(r.capacity() >= r.size());
+        if (s.size() == 0) return;
+        assert(r.front() == s.front());
+        assert(r.back() == s.back());
+        for (size_t i = 0; i < s.size(); ++i) {
+            assert(r[i] == s[i]);
+        }
+    };
+
+    LIMITED_WHILE(provider.remaining_bytes(), MAX_OPERATIONS) {
+        int command = provider.ConsumeIntegral<uint8_t>() % 64;
+        unsigned idx = real.empty() ? 0 : provider.ConsumeIntegralInRange<unsigned>(0, real.size() - 1);
+        const size_t num_buffers = sim.size();
+        // Pick one operation based on value of command. Not all operations are always applicable.
+        // Loop through the applicable ones until command reaches 0 (which avoids the need to
+        // compute the number of applicable commands ahead of time).
+        const bool non_empty{num_buffers != 0};
+        const bool non_full{num_buffers < MAX_BUFFERS};
+        const bool partially_full{non_empty && non_full};
+        const bool multiple_exist{num_buffers > 1};
+        const bool existing_buffer_non_full{non_empty && sim[idx].size() < MAX_BUFFER_SIZE};
+        const bool existing_buffer_non_empty{non_empty && !sim[idx].empty()};
+        assert(non_full || non_empty);
+        while (true) {
+            if (non_full && command-- == 0) {
+                /* Default construct. */
+                real.emplace_back();
+                sim.emplace_back();
+                break;
+            }
+            if (non_empty && command-- == 0) {
+                /* resize() */
+                compare_fn(real[idx], sim[idx]);
+                size_t new_size = provider.ConsumeIntegralInRange<size_t>(0, MAX_BUFFER_SIZE);
+                real[idx].resize(new_size);
+                sim[idx].resize(new_size);
+                assert(real[idx].size() == new_size);
+                break;
+            }
+            if (non_empty && command-- == 0) {
+                /* clear() */
+                compare_fn(real[idx], sim[idx]);
+                real[idx].clear();
+                sim[idx].clear();
+                assert(real[idx].empty());
+                break;
+            }
+            if (non_empty && command-- == 0) {
+                /* Copy construct default. */
+                compare_fn(real[idx], sim[idx]);
+                real[idx] = VecDeque<T>();
+                sim[idx].clear();
+                assert(real[idx].size() == 0);
+                break;
+            }
+            if (non_empty && command-- == 0) {
+                /* Destruct. */
+                compare_fn(real.back(), sim.back());
+                real.pop_back();
+                sim.pop_back();
+                break;
+            }
+            if (partially_full && command-- == 0) {
+                /* Copy construct. */
+                real.emplace_back(real[idx]);
+                sim.emplace_back(sim[idx]);
+                break;
+            }
+            if (partially_full && command-- == 0) {
+                /* Move construct. */
+                VecDeque<T> copy(real[idx]);
+                real.emplace_back(std::move(copy));
+                sim.emplace_back(sim[idx]);
+                break;
+            }
+            if (multiple_exist && command-- == 0) {
+                /* swap() */
+                swap(real[idx], real[(idx + 1) % num_buffers]);
+                swap(sim[idx], sim[(idx + 1) % num_buffers]);
+                break;
+            }
+            if (multiple_exist && command-- == 0) {
+                /* Copy assign. */
+                compare_fn(real[idx], sim[idx]);
+                real[idx] = real[(idx + 1) % num_buffers];
+                sim[idx] = sim[(idx + 1) % num_buffers];
+                break;
+            }
+            if (multiple_exist && command-- == 0) {
+                /* Move assign. */
+                VecDeque<T> copy(real[(idx + 1) % num_buffers]);
+                compare_fn(real[idx], sim[idx]);
+                real[idx] = std::move(copy);
+                sim[idx] = sim[(idx + 1) % num_buffers];
+                break;
+            }
+            if (non_empty && command-- == 0) {
+                /* Self swap() */
+                swap(real[idx], real[idx]);
+                break;
+            }
+            if (non_empty && command-- == 0) {
+                /* Self-copy assign. */
+                real[idx] = real[idx];
+                break;
+            }
+            if (non_empty && command-- == 0) {
+                /* Self-move assign. */
+                // Do not use std::move(real[idx]) here: -Wself-move correctly warns about that.
+                real[idx] = static_cast<VecDeque<T>&&>(real[idx]);
+                break;
+            }
+            if (non_empty && command-- == 0) {
+                /* reserve() */
+                size_t res_size = provider.ConsumeIntegralInRange<size_t>(0, MAX_BUFFER_SIZE);
+                size_t old_cap = real[idx].capacity();
+                size_t old_size = real[idx].size();
+                real[idx].reserve(res_size);
+                assert(real[idx].size() == old_size);
+                assert(real[idx].capacity() == std::max(old_cap, res_size));
+                break;
+            }
+            if (non_empty && command-- == 0) {
+                /* shrink_to_fit() */
+                size_t old_size = real[idx].size();
+                real[idx].shrink_to_fit();
+                assert(real[idx].size() == old_size);
+                assert(real[idx].capacity() == old_size);
+                break;
+            }
+            if (existing_buffer_non_full && command-- == 0) {
+                /* push_back() (copying) */
+                tmp = T(rng());
+                size_t old_size = real[idx].size();
+                size_t old_cap = real[idx].capacity();
+                real[idx].push_back(*tmp);
+                sim[idx].push_back(*tmp);
+                assert(real[idx].size() == old_size + 1);
+                if (old_cap > old_size) {
+                    assert(real[idx].capacity() == old_cap);
+                } else {
+                    assert(real[idx].capacity() > old_cap);
+                    assert(real[idx].capacity() <= 2 * (old_cap + 1));
+                }
+                break;
+            }
+            if (existing_buffer_non_full && command-- == 0) {
+                /* push_back() (moving) */
+                tmp = T(rng());
+                size_t old_size = real[idx].size();
+                size_t old_cap = real[idx].capacity();
+                sim[idx].push_back(*tmp);
+                real[idx].push_back(std::move(*tmp));
+                assert(real[idx].size() == old_size + 1);
+                if (old_cap > old_size) {
+                    assert(real[idx].capacity() == old_cap);
+                } else {
+                    assert(real[idx].capacity() > old_cap);
+                    assert(real[idx].capacity() <= 2 * (old_cap + 1));
+                }
+                break;
+            }
+            if (existing_buffer_non_full && command-- == 0) {
+                /* emplace_back() */
+                uint64_t seed{rng()};
+                size_t old_size = real[idx].size();
+                size_t old_cap = real[idx].capacity();
+                sim[idx].emplace_back(seed);
+                real[idx].emplace_back(seed);
+                assert(real[idx].size() == old_size + 1);
+                if (old_cap > old_size) {
+                    assert(real[idx].capacity() == old_cap);
+                } else {
+                    assert(real[idx].capacity() > old_cap);
+                    assert(real[idx].capacity() <= 2 * (old_cap + 1));
+                }
+                break;
+            }
+            if (existing_buffer_non_full && command-- == 0) {
+                /* push_front() (copying) */
+                tmp = T(rng());
+                size_t old_size = real[idx].size();
+                size_t old_cap = real[idx].capacity();
+                real[idx].push_front(*tmp);
+                sim[idx].push_front(*tmp);
+                assert(real[idx].size() == old_size + 1);
+                if (old_cap > old_size) {
+                    assert(real[idx].capacity() == old_cap);
+                } else {
+                    assert(real[idx].capacity() > old_cap);
+                    assert(real[idx].capacity() <= 2 * (old_cap + 1));
+                }
+                break;
+            }
+            if (existing_buffer_non_full && command-- == 0) {
+                /* push_front() (moving) */
+                tmp = T(rng());
+                size_t old_size = real[idx].size();
+                size_t old_cap = real[idx].capacity();
+                sim[idx].push_front(*tmp);
+                real[idx].push_front(std::move(*tmp));
+                assert(real[idx].size() == old_size + 1);
+                if (old_cap > old_size) {
+                    assert(real[idx].capacity() == old_cap);
+                } else {
+                    assert(real[idx].capacity() > old_cap);
+                    assert(real[idx].capacity() <= 2 * (old_cap + 1));
+                }
+                break;
+            }
+            if (existing_buffer_non_full && command-- == 0) {
+                /* emplace_front() */
+                uint64_t seed{rng()};
+                size_t old_size = real[idx].size();
+                size_t old_cap = real[idx].capacity();
+                sim[idx].emplace_front(seed);
+                real[idx].emplace_front(seed);
+                assert(real[idx].size() == old_size + 1);
+                if (old_cap > old_size) {
+                    assert(real[idx].capacity() == old_cap);
+                } else {
+                    assert(real[idx].capacity() > old_cap);
+                    assert(real[idx].capacity() <= 2 * (old_cap + 1));
+                }
+                break;
+            }
+            if (existing_buffer_non_empty && command-- == 0) {
+                /* front() [modifying] */
+                tmp = T(rng());
+                size_t old_size = real[idx].size();
+                assert(sim[idx].front() == real[idx].front());
+                sim[idx].front() = *tmp;
+                real[idx].front() = std::move(*tmp);
+                assert(real[idx].size() == old_size);
+                break;
+            }
+            if (existing_buffer_non_empty && command-- == 0) {
+                /* back() [modifying] */
+                tmp = T(rng());
+                size_t old_size = real[idx].size();
+                assert(sim[idx].back() == real[idx].back());
+                sim[idx].back() = *tmp;
+                real[idx].back() = *tmp;
+                assert(real[idx].size() == old_size);
+                break;
+            }
+            if (existing_buffer_non_empty && command-- == 0) {
+                /* operator[] [modifying] */
+                tmp = T(rng());
+                size_t pos = provider.ConsumeIntegralInRange<size_t>(0, sim[idx].size() - 1);
+                size_t old_size = real[idx].size();
+                assert(sim[idx][pos] == real[idx][pos]);
+                sim[idx][pos] = *tmp;
+                real[idx][pos] = std::move(*tmp);
+                assert(real[idx].size() == old_size);
+                break;
+            }
+            if (existing_buffer_non_empty && command-- == 0) {
+                /* pop_front() */
+                assert(sim[idx].front() == real[idx].front());
+                size_t old_size = real[idx].size();
+                sim[idx].pop_front();
+                real[idx].pop_front();
+                assert(real[idx].size() == old_size - 1);
+                break;
+            }
+            if (existing_buffer_non_empty && command-- == 0) {
+                /* pop_back() */
+                assert(sim[idx].back() == real[idx].back());
+                size_t old_size = real[idx].size();
+                sim[idx].pop_back();
+                real[idx].pop_back();
+                assert(real[idx].size() == old_size - 1);
+                break;
+            }
+        }
+    }
+
+    /* Fully compare the final state. */
+    for (unsigned i = 0; i < sim.size(); ++i) {
+        // Make sure const getters work.
+        const VecDeque<T>& realbuf = real[i];
+        const std::deque<T>& simbuf = sim[i];
+        compare_fn(realbuf, simbuf);
+        for (unsigned j = 0; j < sim.size(); ++j) {
+            assert((realbuf == real[j]) == (simbuf == sim[j]));
+            assert(((realbuf <=> real[j]) >= 0) == (simbuf >= sim[j]));
+            assert(((realbuf <=> real[j]) <= 0) == (simbuf <= sim[j]));
+        }
+        // Clear out the buffers so we can check below that no objects exist anymore.
+        sim[i].clear();
+        real[i].clear();
+    }
+
+    if constexpr (CheckNoneLeft) {
+        tmp = std::nullopt;
+        T::CheckNoneExist();
+    }
+}
+
+/** Data structure with built-in tracking of all existing objects. */
+template<size_t Size>
+class TrackedObj
+{
+    static_assert(Size > 0);
+
+    /* Data type for map that actually stores the object data.
+     *
+     * The key is a pointer to the TrackedObj, the value is the uint64_t it was initialized with.
+     * Default-constructed and moved-from objects hold an std::nullopt.
+     */
+    using track_map_type = std::map<const TrackedObj<Size>*, std::optional<uint64_t>>;
+
+private:
+
+    /** Actual map. */
+    static inline track_map_type g_tracker;
+
+    /** Iterators into the tracker map for this object.
+     *
+     * This is an array of size Size, all holding the same value, to give the object configurable
+     * size. The value is g_tracker.end() if this object is not fully initialized. */
+    typename track_map_type::iterator m_track_entry[Size];
+
+    void Check() const
+    {
+        auto it = g_tracker.find(this);
+        for (size_t i = 0; i < Size; ++i) {
+            assert(m_track_entry[i] == it);
+        }
+    }
+
+    /** Create entry for this object in g_tracker and populate m_track_entry. */
+    void Register()
+    {
+        auto [it, inserted] = g_tracker.emplace(this, std::nullopt);
+        assert(inserted);
+        for (size_t i = 0; i < Size; ++i) {
+            m_track_entry[i] = it;
+        }
+    }
+
+    void Deregister()
+    {
+        Check();
+        assert(m_track_entry[0] != g_tracker.end());
+        g_tracker.erase(m_track_entry[0]);
+        for (size_t i = 0; i < Size; ++i) {
+            m_track_entry[i] = g_tracker.end();
+        }
+    }
+
+    /** Get value corresponding to this object in g_tracker. */
+    std::optional<uint64_t>& Deref()
+    {
+        Check();
+        assert(m_track_entry[0] != g_tracker.end());
+        return m_track_entry[0]->second;
+    }
+
+    /** Get value corresponding to this object in g_tracker. */
+    const std::optional<uint64_t>& Deref() const
+    {
+        Check();
+        assert(m_track_entry[0] != g_tracker.end());
+        return m_track_entry[0]->second;
+    }
+
+public:
+    ~TrackedObj() { Deregister(); }
+    TrackedObj() { Register(); }
+
+    TrackedObj(uint64_t value)
+    {
+        Register();
+        Deref() = value;
+    }
+
+    TrackedObj(const TrackedObj& other)
+    {
+        Register();
+        Deref() = other.Deref();
+    }
+
+    TrackedObj(TrackedObj&& other)
+    {
+        Register();
+        Deref() = other.Deref();
+        other.Deref() = std::nullopt;
+    }
+
+    TrackedObj& operator=(const TrackedObj& other)
+    {
+        if (this == &other) return *this;
+        Deref() = other.Deref();
+        return *this;
+    }
+
+    TrackedObj& operator=(TrackedObj&& other)
+    {
+        if (this == &other) return *this;
+        Deref() = other.Deref();
+        other.Deref() = std::nullopt;
+        return *this;
+    }
+
+    friend bool operator==(const TrackedObj& a, const TrackedObj& b)
+    {
+        return a.Deref() == b.Deref();
+    }
+
+    friend std::strong_ordering operator<=>(const TrackedObj& a, const TrackedObj& b)
+    {
+        // Libc++ 15 & 16 do not support std::optional<T>::operator<=> yet. See
+        // https://reviews.llvm.org/D146392.
+        if (!a.Deref().has_value() || !b.Deref().has_value()) {
+            return a.Deref().has_value() <=> b.Deref().has_value();
+        }
+        return *a.Deref() <=> *b.Deref();
+    }
+
+    static void CheckNoneExist()
+    {
+        assert(g_tracker.empty());
+    }
+};
+
+} // namespace
+
+FUZZ_TARGET(vecdeque)
+{
+    // Run the test with simple uints (which satisfy all the trivial properties).
+    static_assert(std::is_trivially_copyable_v<uint32_t>);
+    static_assert(std::is_trivially_destructible_v<uint64_t>);
+    TestType<uint8_t, false>(buffer, 1);
+    TestType<uint16_t, false>(buffer, 2);
+    TestType<uint32_t, false>(buffer, 3);
+    TestType<uint64_t, false>(buffer, 4);
+
+    // Run the test with TrackedObjs (which do not).
+    static_assert(!std::is_trivially_copyable_v<TrackedObj<3>>);
+    static_assert(!std::is_trivially_destructible_v<TrackedObj<17>>);
+    TestType<TrackedObj<1>, true>(buffer, 5);
+    TestType<TrackedObj<3>, true>(buffer, 6);
+    TestType<TrackedObj<17>, true>(buffer, 7);
+}