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Merge bitcoin/bitcoin#25311: refactor: remove CBlockIndex copy construction

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36c201feb7 remove CBlockIndex copy construction (James O'Beirne)

Pull request description:

  Copy construction of CBlockIndex objects is a footgun because of the
  wide use of equality-by-pointer comparison in the code base. There are
  also potential lifetime confusions of using copied instances, since
  there are recursive pointer members (e.g. pprev).

  (See also https://github.com/bitcoin/bitcoin/pull/24008#discussion_r891949166)

  We can't just delete the copy constructors because they are used for
  derived classes (CDiskBlockIndex), so we mark them protected.

ACKs for top commit:
  ajtowns:
    ACK 36c201feb7 - code review only
  MarcoFalke:
    re-ACK 36c201feb7  🏻

Tree-SHA512: b1cf9a1cb992464a4377dad609713eea63cc099435df374e4553bfe62d362a4eb5e3c6c6649177832f38c0905b23841caf9d62196cef8e3084bfea0bfc26374b
This commit is contained in:
fanquake 2022-12-19 09:34:34 +00:00
commit 65f5cfda65
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GPG key ID: 2EEB9F5CC09526C1
3 changed files with 31 additions and 17 deletions
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22
src/chain.h
View file

@ -213,10 +213,6 @@ public:
//! (memory only) Maximum nTime in the chain up to and including this block.
unsigned int nTimeMax{0};
CBlockIndex()
{
}
explicit CBlockIndex(const CBlockHeader& block)
: nVersion{block.nVersion},
hashMerkleRoot{block.hashMerkleRoot},
@ -355,6 +351,24 @@ public:
//! Efficiently find an ancestor of this block.
CBlockIndex* GetAncestor(int height);
const CBlockIndex* GetAncestor(int height) const;
CBlockIndex() = default;
~CBlockIndex() = default;
protected:
//! CBlockIndex should not allow public copy construction because equality
//! comparison via pointer is very common throughout the codebase, making
//! use of copy a footgun. Also, use of copies do not have the benefit
//! of simplifying lifetime considerations due to attributes like pprev and
//! pskip, which are at risk of becoming dangling pointers in a copied
//! instance.
//!
//! We declare these protected instead of simply deleting them so that
//! CDiskBlockIndex can reuse copy construction.
CBlockIndex(const CBlockIndex&) = default;
CBlockIndex& operator=(const CBlockIndex&) = delete;
CBlockIndex(CBlockIndex&&) = delete;
CBlockIndex& operator=(CBlockIndex&&) = delete;
};
arith_uint256 GetBlockProof(const CBlockIndex& block);

14
src/test/fuzz/pow.cpp
View file

@ -26,7 +26,7 @@ FUZZ_TARGET_INIT(pow, initialize_pow)
{
FuzzedDataProvider fuzzed_data_provider(buffer.data(), buffer.size());
const Consensus::Params& consensus_params = Params().GetConsensus();
std::vector<CBlockIndex> blocks;
std::vector<std::unique_ptr<CBlockIndex>> blocks;
const uint32_t fixed_time = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
const uint32_t fixed_bits = fuzzed_data_provider.ConsumeIntegral<uint32_t>();
LIMITED_WHILE(fuzzed_data_provider.remaining_bytes() > 0, 10000) {
@ -34,9 +34,10 @@ FUZZ_TARGET_INIT(pow, initialize_pow)
if (!block_header) {
continue;
}
CBlockIndex current_block{*block_header};
CBlockIndex& current_block{
*blocks.emplace_back(std::make_unique<CBlockIndex>(*block_header))};
{
CBlockIndex* previous_block = blocks.empty() ? nullptr : &PickValue(fuzzed_data_provider, blocks);
CBlockIndex* previous_block = blocks.empty() ? nullptr : PickValue(fuzzed_data_provider, blocks).get();
const int current_height = (previous_block != nullptr && previous_block->nHeight != std::numeric_limits<int>::max()) ? previous_block->nHeight + 1 : 0;
if (fuzzed_data_provider.ConsumeBool()) {
current_block.pprev = previous_block;
@ -58,7 +59,6 @@ FUZZ_TARGET_INIT(pow, initialize_pow)
} else {
current_block.nChainWork = ConsumeArithUInt256(fuzzed_data_provider);
}
blocks.push_back(current_block);
}
{
(void)GetBlockProof(current_block);
@ -68,9 +68,9 @@ FUZZ_TARGET_INIT(pow, initialize_pow)
}
}
{
const CBlockIndex* to = &PickValue(fuzzed_data_provider, blocks);
const CBlockIndex* from = &PickValue(fuzzed_data_provider, blocks);
const CBlockIndex* tip = &PickValue(fuzzed_data_provider, blocks);
const auto& to = PickValue(fuzzed_data_provider, blocks);
const auto& from = PickValue(fuzzed_data_provider, blocks);
const auto& tip = PickValue(fuzzed_data_provider, blocks);
try {
(void)GetBlockProofEquivalentTime(*to, *from, *tip, consensus_params);
} catch (const uint_error&) {

12
src/test/miner_tests.cpp
View file

@ -87,11 +87,11 @@ constexpr static struct {
{0, 792342903}, {6, 678455063}, {6, 773251385}, {5, 186617471}, {6, 883189502}, {7, 396077336},
{8, 254702874}, {0, 455592851}};
static CBlockIndex CreateBlockIndex(int nHeight, CBlockIndex* active_chain_tip) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
static std::unique_ptr<CBlockIndex> CreateBlockIndex(int nHeight, CBlockIndex* active_chain_tip) EXCLUSIVE_LOCKS_REQUIRED(cs_main)
{
CBlockIndex index;
index.nHeight = nHeight;
index.pprev = active_chain_tip;
auto index{std::make_unique<CBlockIndex>()};
index->nHeight = nHeight;
index->pprev = active_chain_tip;
return index;
}
@ -438,7 +438,7 @@ void MinerTestingSetup::TestBasicMining(const CScript& scriptPubKey, const std::
{
CBlockIndex* active_chain_tip = m_node.chainman->ActiveChain().Tip();
BOOST_CHECK(SequenceLocks(CTransaction(tx), flags, prevheights, CreateBlockIndex(active_chain_tip->nHeight + 2, active_chain_tip))); // Sequence locks pass on 2nd block
BOOST_CHECK(SequenceLocks(CTransaction(tx), flags, prevheights, *CreateBlockIndex(active_chain_tip->nHeight + 2, active_chain_tip))); // Sequence locks pass on 2nd block
}
// relative time locked
@ -455,7 +455,7 @@ void MinerTestingSetup::TestBasicMining(const CScript& scriptPubKey, const std::
m_node.chainman->ActiveChain().Tip()->GetAncestor(m_node.chainman->ActiveChain().Tip()->nHeight - i)->nTime += SEQUENCE_LOCK_TIME; // Trick the MedianTimePast
{
CBlockIndex* active_chain_tip = m_node.chainman->ActiveChain().Tip();
BOOST_CHECK(SequenceLocks(CTransaction(tx), flags, prevheights, CreateBlockIndex(active_chain_tip->nHeight + 1, active_chain_tip)));
BOOST_CHECK(SequenceLocks(CTransaction(tx), flags, prevheights, *CreateBlockIndex(active_chain_tip->nHeight + 1, active_chain_tip)));
}
for (int i = 0; i < CBlockIndex::nMedianTimeSpan; ++i) {