refactor: Make CTxMemPoolEntry only explicitly copyable

This has the goal of prohibiting users from accidentally creating
runtime failures, e.g. by interacting with iterator_to with a copied
entry.

CTxMemPoolEntry is already implicitly not move-constructable. So be
explicit about this and use a std::list to collect the values in the
policy_estimator fuzz test instead of a std::vector.

Co-authored-by: Anthony Towns <aj@erisian.com.au>

1 files changed, 12 insertions, 0 deletions

diff --git a/src/kernel/mempool_entry.h b/src/kernel/mempool_entry.h
index 7c905ca4f4..b5c0499012 100644
--- a/src/kernel/mempool_entry.h
+++ b/src/kernel/mempool_entry.h
@@ -71,6 +71,11 @@ public:
     typedef std::set<CTxMemPoolEntryRef, CompareIteratorByHash> Children;
 
 private:
+    CTxMemPoolEntry(const CTxMemPoolEntry&) = default;
+    struct ExplicitCopyTag {
+        explicit ExplicitCopyTag() = default;
+    };
+
     const CTransactionRef tx;
     mutable Parents m_parents;
     mutable Children m_children;
@@ -122,6 +127,13 @@ public:
           nModFeesWithAncestors{nFee},
           nSigOpCostWithAncestors{sigOpCost} {}
 
+    CTxMemPoolEntry(ExplicitCopyTag, const CTxMemPoolEntry& entry) : CTxMemPoolEntry(entry) {}
+    CTxMemPoolEntry& operator=(const CTxMemPoolEntry&) = delete;
+    CTxMemPoolEntry(CTxMemPoolEntry&&) = delete;
+    CTxMemPoolEntry& operator=(CTxMemPoolEntry&&) = delete;
+
+    static constexpr ExplicitCopyTag ExplicitCopy{};
+
     const CTransaction& GetTx() const { return *this->tx; }
     CTransactionRef GetSharedTx() const { return this->tx; }
     const CAmount& GetFee() const { return nFee; }