Repository: bitcoin/bitcoin
File: src/test/fuzz/process_message.cpp (C++)

Code before:
#include <iostream>
#include <memory>
#include <string>
#include <string_view>
#include <vector>

namespace {
const TestingSetup* g_setup;
std::string_view LIMIT_TO_MESSAGE_TYPE{};
} // namespace

void initialize_process_message()
{
    if (const auto val{std::getenv("LIMIT_TO_MESSAGE_TYPE")}) {
        LIMIT_TO_MESSAGE_TYPE = val;
        Assert(std::count(ALL_NET_MESSAGE_TYPES.begin(), ALL_NET_MESSAGE_TYPES.end(), LIMIT_TO_MESSAGE_TYPE)); // Unknown message type passed
    }

    static const auto testing_setup = MakeNoLogFileContext<const TestingSetup>(
            /*chain_type=*/ChainType::REGTEST,
            {.extra_args = {"-txreconciliation"}});
    g_setup = testing_setup.get();
    for (int i = 0; i < 2 * COINBASE_MATURITY; i++) {
        MineBlock(g_setup->m_node, CScript() << OP_TRUE);
    }
    g_setup->m_node.validation_signals->SyncWithValidationInterfaceQueue();
}

FUZZ_TARGET(process_message, .init = initialize_process_message)
{
    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());

    ConnmanTestMsg& connman = *static_cast<ConnmanTestMsg*>(g_setup->m_node.connman.get());
    auto& chainman = static_cast<TestChainstateManager&>(*g_setup->m_node.chainman);
    SetMockTime(1610000000); // any time to successfully reset ibd
    chainman.ResetIbd();

    LOCK(NetEventsInterface::g_msgproc_mutex);

    const std::string random_message_type{fuzzed_data_provider.ConsumeBytesAsString(CMessageHeader::MESSAGE_TYPE_SIZE).c_str()};
    if (!LIMIT_TO_MESSAGE_TYPE.empty() && random_message_type != LIMIT_TO_MESSAGE_TYPE) {
        return;
    }
    CNode& p2p_node = *ConsumeNodeAsUniquePtr(fuzzed_data_provider).release();

    connman.AddTestNode(p2p_node);
    FillNode(fuzzed_data_provider, connman, p2p_node);

    const auto mock_time = ConsumeTime(fuzzed_data_provider);
    SetMockTime(mock_time);


Review comment (suggestion):
I would squash the last commit, then you can also drop the `using node::BlockAssembler` declaration entirely by just calling `MineBlock(g_setup->m_node, {})`.

Code after:
#include <iostream>
#include <memory>
#include <string>
#include <string_view>
#include <vector>

namespace {
const TestingSetup* g_setup;
std::string_view LIMIT_TO_MESSAGE_TYPE{};
} // namespace

void initialize_process_message()
{
    if (const auto val{std::getenv("LIMIT_TO_MESSAGE_TYPE")}) {
        LIMIT_TO_MESSAGE_TYPE = val;
        Assert(std::count(ALL_NET_MESSAGE_TYPES.begin(), ALL_NET_MESSAGE_TYPES.end(), LIMIT_TO_MESSAGE_TYPE)); // Unknown message type passed
    }

    static const auto testing_setup = MakeNoLogFileContext<const TestingSetup>(
            /*chain_type=*/ChainType::REGTEST,
            {.extra_args = {"-txreconciliation"}});
    g_setup = testing_setup.get();
    for (int i = 0; i < 2 * COINBASE_MATURITY; i++) {
        MineBlock(g_setup->m_node, {});
    }
    g_setup->m_node.validation_signals->SyncWithValidationInterfaceQueue();
}

FUZZ_TARGET(process_message, .init = initialize_process_message)
{
    FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());

    ConnmanTestMsg& connman = *static_cast<ConnmanTestMsg*>(g_setup->m_node.connman.get());
    auto& chainman = static_cast<TestChainstateManager&>(*g_setup->m_node.chainman);
    SetMockTime(1610000000); // any time to successfully reset ibd
    chainman.ResetIbd();

    LOCK(NetEventsInterface::g_msgproc_mutex);

    const std::string random_message_type{fuzzed_data_provider.ConsumeBytesAsString(CMessageHeader::MESSAGE_TYPE_SIZE).c_str()};
    if (!LIMIT_TO_MESSAGE_TYPE.empty() && random_message_type != LIMIT_TO_MESSAGE_TYPE) {
        return;
    }
    CNode& p2p_node = *ConsumeNodeAsUniquePtr(fuzzed_data_provider).release();

    connman.AddTestNode(p2p_node);
    FillNode(fuzzed_data_provider, connman, p2p_node);

    const auto mock_time = ConsumeTime(fuzzed_data_provider);
    SetMockTime(mock_time);