refactor: remove dead branches in SingletonClusterImpl

`SplitAll()` always calls `ApplyRemovals()` first, for a singleton, it empties the cluster, therefore any `SingletonClusterImpl` passed to `Split()` must be empty.

`TxGraphImpl::ApplyDependencies()` first merges each dependency group and asserts the group has at least one dependency.
Since `parent` != `child`, `TxGraphImpl::Merge()` upgrades the merge target to `GenericClusterImpl`, therefore the `ApplyDependencies()` is never dispatched to `SingletonClusterImpl`.

Found during review: https://github.com/bitcoin/bitcoin/pull/33157#discussion_r2423058928
Coverage evidence:
* https://maflcko.github.io/b-c-cov/fuzz.coverage/src/txgraph.cpp.gcov.html#L1446
* https://storage.googleapis.com/oss-fuzz-coverage/bitcoin-core/reports/20251103/linux/src/bitcoin-core/src/txgraph.cpp.html#L1446
This commit is contained in:
Lőrinc
2025-11-03 12:19:05 +01:00
parent 25c45bb0d0
commit 2d23820ee1

View File

@@ -1437,16 +1437,9 @@ bool GenericClusterImpl::Split(TxGraphImpl& graph, int level) noexcept
bool SingletonClusterImpl::Split(TxGraphImpl& graph, int level) noexcept
{
Assume(NeedsSplitting());
if (GetTxCount() == 0) {
// The cluster is now empty.
graph.GetClusterSet(level).m_cluster_usage -= TotalMemoryUsage();
return true;
} else {
// Nothing changed.
graph.SetClusterQuality(level, m_quality, m_setindex, QualityLevel::OPTIMAL);
Updated(graph, level);
return false;
}
Assume(!GetTxCount());
graph.GetClusterSet(level).m_cluster_usage -= TotalMemoryUsage();
return true;
}
void GenericClusterImpl::Merge(TxGraphImpl& graph, int level, Cluster& other) noexcept
@@ -1482,10 +1475,9 @@ void GenericClusterImpl::Merge(TxGraphImpl& graph, int level, Cluster& other) no
});
}
void SingletonClusterImpl::Merge(TxGraphImpl& graph, int level, Cluster& other_abstract) noexcept
void SingletonClusterImpl::Merge(TxGraphImpl&, int, Cluster&) noexcept
{
// Nothing can be merged into a singleton; it should have been converted to GenericClusterImpl
// first.
// Nothing can be merged into a singleton; it should have been converted to GenericClusterImpl first.
Assume(false);
}
@@ -1537,13 +1529,10 @@ void GenericClusterImpl::ApplyDependencies(TxGraphImpl& graph, int level, std::s
Updated(graph, level);
}
void SingletonClusterImpl::ApplyDependencies(TxGraphImpl& graph, int level, std::span<std::pair<GraphIndex, GraphIndex>> to_apply) noexcept
void SingletonClusterImpl::ApplyDependencies(TxGraphImpl&, int, std::span<std::pair<GraphIndex, GraphIndex>>) noexcept
{
// Nothing can actually be applied.
for (auto& [par, chl] : to_apply) {
Assume(par == m_graph_index);
Assume(chl == m_graph_index);
}
Assume(false);
}
TxGraphImpl::~TxGraphImpl() noexcept