Merge #9125: Make CBlock a vector of shared_ptr of CTransactions

b4e4ba4 Introduce convenience type CTransactionRef (Pieter Wuille)
1662b43 Make CBlock::vtx a vector of shared_ptr<CTransaction> (Pieter Wuille)
da60506 Add deserializing constructors to CTransaction and CMutableTransaction (Pieter Wuille)
0e85204 Add serialization for unique_ptr and shared_ptr (Pieter Wuille)

27 files changed, 261 insertions, 171 deletions

diff --git a/src/blockencodings.cpp b/src/blockencodings.cpp
index dbed90583d..f14ae1c412 100644
--- a/src/blockencodings.cpp
+++ b/src/blockencodings.cpp
@@ -24,7 +24,7 @@ CBlockHeaderAndShortTxIDs::CBlockHeaderAndShortTxIDs(const CBlock& block, bool f
     //TODO: Use our mempool prior to block acceptance to predictively fill more than just the coinbase
     prefilledtxn[0] = {0, block.vtx[0]};
     for (size_t i = 1; i < block.vtx.size(); i++) {
-        const CTransaction& tx = block.vtx[i];
+        const CTransaction& tx = *block.vtx[i];
         shorttxids[i - 1] = GetShortID(fUseWTXID ? tx.GetWitnessHash() : tx.GetHash());
     }
 }
@@ -59,7 +59,7 @@ ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& c
 
     int32_t lastprefilledindex = -1;
     for (size_t i = 0; i < cmpctblock.prefilledtxn.size(); i++) {
-        if (cmpctblock.prefilledtxn[i].tx.IsNull())
+        if (cmpctblock.prefilledtxn[i].tx->IsNull())
             return READ_STATUS_INVALID;
 
         lastprefilledindex += cmpctblock.prefilledtxn[i].index + 1; //index is a uint16_t, so cant overflow here
@@ -71,7 +71,7 @@ ReadStatus PartiallyDownloadedBlock::InitData(const CBlockHeaderAndShortTxIDs& c
             // have neither a prefilled txn or a shorttxid!
             return READ_STATUS_INVALID;
         }
-        txn_available[lastprefilledindex] = std::make_shared<CTransaction>(cmpctblock.prefilledtxn[i].tx);
+        txn_available[lastprefilledindex] = cmpctblock.prefilledtxn[i].tx;
     }
     prefilled_count = cmpctblock.prefilledtxn.size();
 
@@ -142,7 +142,7 @@ bool PartiallyDownloadedBlock::IsTxAvailable(size_t index) const {
     return txn_available[index] ? true : false;
 }
 
-ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<CTransaction>& vtx_missing) const {
+ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing) const {
     assert(!header.IsNull());
     block = header;
     block.vtx.resize(txn_available.size());
@@ -154,7 +154,7 @@ ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<
                 return READ_STATUS_INVALID;
             block.vtx[i] = vtx_missing[tx_missing_offset++];
         } else
-            block.vtx[i] = *txn_available[i];
+            block.vtx[i] = txn_available[i];
     }
     if (vtx_missing.size() != tx_missing_offset)
         return READ_STATUS_INVALID;
@@ -172,8 +172,8 @@ ReadStatus PartiallyDownloadedBlock::FillBlock(CBlock& block, const std::vector<
 
     LogPrint("cmpctblock", "Successfully reconstructed block %s with %lu txn prefilled, %lu txn from mempool and %lu txn requested\n", header.GetHash().ToString(), prefilled_count, mempool_count, vtx_missing.size());
     if (vtx_missing.size() < 5) {
-        for(const CTransaction& tx : vtx_missing)
-            LogPrint("cmpctblock", "Reconstructed block %s required tx %s\n", header.GetHash().ToString(), tx.GetHash().ToString());
+        for (const auto& tx : vtx_missing)
+            LogPrint("cmpctblock", "Reconstructed block %s required tx %s\n", header.GetHash().ToString(), tx->GetHash().ToString());
     }
 
     return READ_STATUS_OK;
diff --git a/src/blockencodings.h b/src/blockencodings.h
index 1f9491867a..27baf1f8f8 100644
--- a/src/blockencodings.h
+++ b/src/blockencodings.h
@@ -14,9 +14,9 @@ class CTxMemPool;
 // Dumb helper to handle CTransaction compression at serialize-time
 struct TransactionCompressor {
 private:
-    CTransaction& tx;
+    CTransactionRef& tx;
 public:
-    TransactionCompressor(CTransaction& txIn) : tx(txIn) {}
+    TransactionCompressor(CTransactionRef& txIn) : tx(txIn) {}
 
     ADD_SERIALIZE_METHODS;
 
@@ -72,7 +72,7 @@ class BlockTransactions {
 public:
     // A BlockTransactions message
     uint256 blockhash;
-    std::vector<CTransaction> txn;
+    std::vector<CTransactionRef> txn;
 
     BlockTransactions() {}
     BlockTransactions(const BlockTransactionsRequest& req) :
@@ -104,7 +104,7 @@ struct PrefilledTransaction {
     // Used as an offset since last prefilled tx in CBlockHeaderAndShortTxIDs,
     // as a proper transaction-in-block-index in PartiallyDownloadedBlock
     uint16_t index;
-    CTransaction tx;
+    CTransactionRef tx;
 
     ADD_SERIALIZE_METHODS;
 
@@ -193,7 +193,7 @@ public:
 
 class PartiallyDownloadedBlock {
 protected:
-    std::vector<std::shared_ptr<const CTransaction> > txn_available;
+    std::vector<CTransactionRef> txn_available;
     size_t prefilled_count = 0, mempool_count = 0;
     CTxMemPool* pool;
 public:
@@ -202,7 +202,7 @@ public:
 
     ReadStatus InitData(const CBlockHeaderAndShortTxIDs& cmpctblock);
     bool IsTxAvailable(size_t index) const;
-    ReadStatus FillBlock(CBlock& block, const std::vector<CTransaction>& vtx_missing) const;
+    ReadStatus FillBlock(CBlock& block, const std::vector<CTransactionRef>& vtx_missing) const;
 };
 
 #endif
diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index a57ab632e4..3b3c0a5d3e 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -31,7 +31,7 @@ static CBlock CreateGenesisBlock(const char* pszTimestamp, const CScript& genesi
     genesis.nBits    = nBits;
     genesis.nNonce   = nNonce;
     genesis.nVersion = nVersion;
-    genesis.vtx.push_back(txNew);
+    genesis.vtx.push_back(MakeTransactionRef(std::move(txNew)));
     genesis.hashPrevBlock.SetNull();
     genesis.hashMerkleRoot = BlockMerkleRoot(genesis);
     return genesis;
diff --git a/src/consensus/merkle.cpp b/src/consensus/merkle.cpp
index 35f7d2e05a..6fa96ddf45 100644
--- a/src/consensus/merkle.cpp
+++ b/src/consensus/merkle.cpp
@@ -160,7 +160,7 @@ uint256 BlockMerkleRoot(const CBlock& block, bool* mutated)
     std::vector<uint256> leaves;
     leaves.resize(block.vtx.size());
     for (size_t s = 0; s < block.vtx.size(); s++) {
-        leaves[s] = block.vtx[s].GetHash();
+        leaves[s] = block.vtx[s]->GetHash();
     }
     return ComputeMerkleRoot(leaves, mutated);
 }
@@ -171,7 +171,7 @@ uint256 BlockWitnessMerkleRoot(const CBlock& block, bool* mutated)
     leaves.resize(block.vtx.size());
     leaves[0].SetNull(); // The witness hash of the coinbase is 0.
     for (size_t s = 1; s < block.vtx.size(); s++) {
-        leaves[s] = block.vtx[s].GetWitnessHash();
+        leaves[s] = block.vtx[s]->GetWitnessHash();
     }
     return ComputeMerkleRoot(leaves, mutated);
 }
@@ -181,7 +181,7 @@ std::vector<uint256> BlockMerkleBranch(const CBlock& block, uint32_t position)
     std::vector<uint256> leaves;
     leaves.resize(block.vtx.size());
     for (size_t s = 0; s < block.vtx.size(); s++) {
-        leaves[s] = block.vtx[s].GetHash();
+        leaves[s] = block.vtx[s]->GetHash();
     }
     return ComputeMerkleBranch(leaves, position);
 }
diff --git a/src/core_memusage.h b/src/core_memusage.h
index b8e0f08bbf..0dcc24c40c 100644
--- a/src/core_memusage.h
+++ b/src/core_memusage.h
@@ -69,8 +69,8 @@ static inline size_t RecursiveDynamicUsage(const CMutableTransaction& tx) {
 
 static inline size_t RecursiveDynamicUsage(const CBlock& block) {
     size_t mem = memusage::DynamicUsage(block.vtx);
-    for (std::vector<CTransaction>::const_iterator it = block.vtx.begin(); it != block.vtx.end(); it++) {
-        mem += RecursiveDynamicUsage(*it);
+    for (const auto& tx : block.vtx) {
+        mem += memusage::DynamicUsage(tx) + RecursiveDynamicUsage(*tx);
     }
     return mem;
 }
diff --git a/src/main.cpp b/src/main.cpp
index 263421aea4..aeeb31ec40 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -233,7 +233,7 @@ namespace {
     int nPeersWithValidatedDownloads = 0;
 
     /** Relay map, protected by cs_main. */
-    typedef std::map<uint256, std::shared_ptr<const CTransaction>> MapRelay;
+    typedef std::map<uint256, CTransactionRef> MapRelay;
     MapRelay mapRelay;
     /** Expiration-time ordered list of (expire time, relay map entry) pairs, protected by cs_main). */
     std::deque<std::pair<int64_t, MapRelay::iterator>> vRelayExpiration;
@@ -1639,7 +1639,7 @@ bool GetTransaction(const uint256 &hash, CTransaction &txOut, const Consensus::P
 
     LOCK(cs_main);
 
-    std::shared_ptr<const CTransaction> ptx = mempool.get(hash);
+    CTransactionRef ptx = mempool.get(hash);
     if (ptx)
     {
         txOut = *ptx;
@@ -1682,9 +1682,9 @@ bool GetTransaction(const uint256 &hash, CTransaction &txOut, const Consensus::P
     if (pindexSlow) {
         CBlock block;
         if (ReadBlockFromDisk(block, pindexSlow, consensusParams)) {
-            BOOST_FOREACH(const CTransaction &tx, block.vtx) {
-                if (tx.GetHash() == hash) {
-                    txOut = tx;
+            for (const auto& tx : block.vtx) {
+                if (tx->GetHash() == hash) {
+                    txOut = *tx;
                     hashBlock = pindexSlow->GetBlockHash();
                     return true;
                 }
@@ -2223,7 +2223,7 @@ bool DisconnectBlock(const CBlock& block, CValidationState& state, const CBlockI
 
     // undo transactions in reverse order
     for (int i = block.vtx.size() - 1; i >= 0; i--) {
-        const CTransaction &tx = block.vtx[i];
+        const CTransaction &tx = *(block.vtx[i]);
         uint256 hash = tx.GetHash();
 
         // Check that all outputs are available and match the outputs in the block itself
@@ -2417,8 +2417,8 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
     fEnforceBIP30 = fEnforceBIP30 && (!pindexBIP34height || !(pindexBIP34height->GetBlockHash() == chainparams.GetConsensus().BIP34Hash));
 
     if (fEnforceBIP30) {
-        BOOST_FOREACH(const CTransaction& tx, block.vtx) {
-            const CCoins* coins = view.AccessCoins(tx.GetHash());
+        for (const auto& tx : block.vtx) {
+            const CCoins* coins = view.AccessCoins(tx->GetHash());
             if (coins && !coins->IsPruned())
                 return state.DoS(100, error("ConnectBlock(): tried to overwrite transaction"),
                                  REJECT_INVALID, "bad-txns-BIP30");
@@ -2474,7 +2474,7 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
     txdata.reserve(block.vtx.size()); // Required so that pointers to individual PrecomputedTransactionData don't get invalidated
     for (unsigned int i = 0; i < block.vtx.size(); i++)
     {
-        const CTransaction &tx = block.vtx[i];
+        const CTransaction &tx = *(block.vtx[i]);
 
         nInputs += tx.vin.size();
 
@@ -2544,10 +2544,10 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
     LogPrint("bench", "      - Connect %u transactions: %.2fms (%.3fms/tx, %.3fms/txin) [%.2fs]\n", (unsigned)block.vtx.size(), 0.001 * (nTime3 - nTime2), 0.001 * (nTime3 - nTime2) / block.vtx.size(), nInputs <= 1 ? 0 : 0.001 * (nTime3 - nTime2) / (nInputs-1), nTimeConnect * 0.000001);
 
     CAmount blockReward = nFees + GetBlockSubsidy(pindex->nHeight, chainparams.GetConsensus());
-    if (block.vtx[0].GetValueOut() > blockReward)
+    if (block.vtx[0]->GetValueOut() > blockReward)
         return state.DoS(100,
                          error("ConnectBlock(): coinbase pays too much (actual=%d vs limit=%d)",
-                               block.vtx[0].GetValueOut(), blockReward),
+                               block.vtx[0]->GetValueOut(), blockReward),
                                REJECT_INVALID, "bad-cb-amount");
 
     if (!control.Wait())
@@ -2590,7 +2590,7 @@ bool ConnectBlock(const CBlock& block, CValidationState& state, CBlockIndex* pin
     // Watch for changes to the previous coinbase transaction.
     static uint256 hashPrevBestCoinBase;
     GetMainSignals().UpdatedTransaction(hashPrevBestCoinBase);
-    hashPrevBestCoinBase = block.vtx[0].GetHash();
+    hashPrevBestCoinBase = block.vtx[0]->GetHash();
 
     // Erase orphan transactions include or precluded by this block
     if (vOrphanErase.size()) {
@@ -2807,7 +2807,8 @@ bool static DisconnectTip(CValidationState& state, const CChainParams& chainpara
     if (!fBare) {
         // Resurrect mempool transactions from the disconnected block.
         std::vector<uint256> vHashUpdate;
-        BOOST_FOREACH(const CTransaction &tx, block.vtx) {
+        for (const auto& it : block.vtx) {
+            const CTransaction& tx = *it;
             // ignore validation errors in resurrected transactions
             CValidationState stateDummy;
             if (tx.IsCoinBase() || !AcceptToMemoryPool(mempool, stateDummy, tx, false, NULL, true)) {
@@ -2828,8 +2829,8 @@ bool static DisconnectTip(CValidationState& state, const CChainParams& chainpara
     UpdateTip(pindexDelete->pprev, chainparams);
     // Let wallets know transactions went from 1-confirmed to
     // 0-confirmed or conflicted:
-    BOOST_FOREACH(const CTransaction &tx, block.vtx) {
-        GetMainSignals().SyncTransaction(tx, pindexDelete->pprev, CMainSignals::SYNC_TRANSACTION_NOT_IN_BLOCK);
+    for (const auto& tx : block.vtx) {
+        GetMainSignals().SyncTransaction(*tx, pindexDelete->pprev, CMainSignals::SYNC_TRANSACTION_NOT_IN_BLOCK);
     }
     return true;
 }
@@ -2844,7 +2845,7 @@ static int64_t nTimePostConnect = 0;
  * Connect a new block to chainActive. pblock is either NULL or a pointer to a CBlock
  * corresponding to pindexNew, to bypass loading it again from disk.
  */
-bool static ConnectTip(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexNew, const CBlock* pblock, std::vector<std::shared_ptr<const CTransaction>> &txConflicted, std::vector<std::tuple<CTransaction,CBlockIndex*,int>> &txChanged)
+bool static ConnectTip(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexNew, const CBlock* pblock, std::vector<CTransactionRef> &txConflicted, std::vector<std::tuple<CTransactionRef,CBlockIndex*,int>> &txChanged)
 {
     assert(pindexNew->pprev == chainActive.Tip());
     // Read block from disk.
@@ -2884,7 +2885,7 @@ bool static ConnectTip(CValidationState& state, const CChainParams& chainparams,
     // Update chainActive & related variables.
     UpdateTip(pindexNew, chainparams);
 
-    for(unsigned int i=0; i < pblock->vtx.size(); i++)
+    for (unsigned int i=0; i < pblock->vtx.size(); i++)
         txChanged.emplace_back(pblock->vtx[i], pindexNew, i);
 
     int64_t nTime6 = GetTimeMicros(); nTimePostConnect += nTime6 - nTime5; nTimeTotal += nTime6 - nTime1;
@@ -2967,7 +2968,7 @@ static void PruneBlockIndexCandidates() {
  * Try to make some progress towards making pindexMostWork the active block.
  * pblock is either NULL or a pointer to a CBlock corresponding to pindexMostWork.
  */
-static bool ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const CBlock* pblock, bool& fInvalidFound, std::vector<std::shared_ptr<const CTransaction>>& txConflicted, std::vector<std::tuple<CTransaction,CBlockIndex*,int>>& txChanged)
+static bool ActivateBestChainStep(CValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const CBlock* pblock, bool& fInvalidFound, std::vector<CTransactionRef>& txConflicted, std::vector<std::tuple<CTransactionRef,CBlockIndex*,int>>& txChanged)
 {
     AssertLockHeld(cs_main);
     const CBlockIndex *pindexOldTip = chainActive.Tip();
@@ -3068,7 +3069,7 @@ static void NotifyHeaderTip() {
 bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams, const CBlock *pblock) {
     CBlockIndex *pindexMostWork = NULL;
     CBlockIndex *pindexNewTip = NULL;
-    std::vector<std::tuple<CTransaction,CBlockIndex*,int>> txChanged;
+    std::vector<std::tuple<CTransactionRef,CBlockIndex*,int>> txChanged;
     if (pblock)
         txChanged.reserve(pblock->vtx.size());
     do {
@@ -3078,7 +3079,7 @@ bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams,
             break;
 
         const CBlockIndex *pindexFork;
-        std::vector<std::shared_ptr<const CTransaction>> txConflicted;
+        std::vector<CTransactionRef> txConflicted;
         bool fInitialDownload;
         {
             LOCK(cs_main);
@@ -3109,13 +3110,13 @@ bool ActivateBestChain(CValidationState &state, const CChainParams& chainparams,
 
         // throw all transactions though the signal-interface
         // while _not_ holding the cs_main lock
-        for(std::shared_ptr<const CTransaction> tx : txConflicted)
+        for (const auto& tx : txConflicted)
         {
             GetMainSignals().SyncTransaction(*tx, pindexNewTip, CMainSignals::SYNC_TRANSACTION_NOT_IN_BLOCK);
         }
         // ... and about transactions that got confirmed:
-        for(unsigned int i = 0; i < txChanged.size(); i++)
-            GetMainSignals().SyncTransaction(std::get<0>(txChanged[i]), std::get<1>(txChanged[i]), std::get<2>(txChanged[i]));
+        for (unsigned int i = 0; i < txChanged.size(); i++)
+            GetMainSignals().SyncTransaction(*std::get<0>(txChanged[i]), std::get<1>(txChanged[i]), std::get<2>(txChanged[i]));
 
         // Notify external listeners about the new tip.
         GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork, fInitialDownload);
@@ -3454,22 +3455,22 @@ bool CheckBlock(const CBlock& block, CValidationState& state, const Consensus::P
         return state.DoS(100, false, REJECT_INVALID, "bad-blk-length", false, "size limits failed");
 
     // First transaction must be coinbase, the rest must not be
-    if (block.vtx.empty() || !block.vtx[0].IsCoinBase())
+    if (block.vtx.empty() || !block.vtx[0]->IsCoinBase())
         return state.DoS(100, false, REJECT_INVALID, "bad-cb-missing", false, "first tx is not coinbase");
     for (unsigned int i = 1; i < block.vtx.size(); i++)
-        if (block.vtx[i].IsCoinBase())
+        if (block.vtx[i]->IsCoinBase())
             return state.DoS(100, false, REJECT_INVALID, "bad-cb-multiple", false, "more than one coinbase");
 
     // Check transactions
     for (const auto& tx : block.vtx)
-        if (!CheckTransaction(tx, state, false))
+        if (!CheckTransaction(*tx, state, false))
             return state.Invalid(false, state.GetRejectCode(), state.GetRejectReason(),
-                                 strprintf("Transaction check failed (tx hash %s) %s", tx.GetHash().ToString(), state.GetDebugMessage()));
+                                 strprintf("Transaction check failed (tx hash %s) %s", tx->GetHash().ToString(), state.GetDebugMessage()));
 
     unsigned int nSigOps = 0;
     for (const auto& tx : block.vtx)
     {
-        nSigOps += GetLegacySigOpCount(tx);
+        nSigOps += GetLegacySigOpCount(*tx);
     }
     if (nSigOps * WITNESS_SCALE_FACTOR > MAX_BLOCK_SIGOPS_COST)
         return state.DoS(100, false, REJECT_INVALID, "bad-blk-sigops", false, "out-of-bounds SigOpCount");
@@ -3505,8 +3506,8 @@ bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& pa
 static int GetWitnessCommitmentIndex(const CBlock& block)
 {
     int commitpos = -1;
-    for (size_t o = 0; o < block.vtx[0].vout.size(); o++) {
-        if (block.vtx[0].vout[o].scriptPubKey.size() >= 38 && block.vtx[0].vout[o].scriptPubKey[0] == OP_RETURN && block.vtx[0].vout[o].scriptPubKey[1] == 0x24 && block.vtx[0].vout[o].scriptPubKey[2] == 0xaa && block.vtx[0].vout[o].scriptPubKey[3] == 0x21 && block.vtx[0].vout[o].scriptPubKey[4] == 0xa9 && block.vtx[0].vout[o].scriptPubKey[5] == 0xed) {
+    for (size_t o = 0; o < block.vtx[0]->vout.size(); o++) {
+        if (block.vtx[0]->vout[o].scriptPubKey.size() >= 38 && block.vtx[0]->vout[o].scriptPubKey[0] == OP_RETURN && block.vtx[0]->vout[o].scriptPubKey[1] == 0x24 && block.vtx[0]->vout[o].scriptPubKey[2] == 0xaa && block.vtx[0]->vout[o].scriptPubKey[3] == 0x21 && block.vtx[0]->vout[o].scriptPubKey[4] == 0xa9 && block.vtx[0]->vout[o].scriptPubKey[5] == 0xed) {
             commitpos = o;
         }
     }
@@ -3517,10 +3518,12 @@ void UpdateUncommittedBlockStructures(CBlock& block, const CBlockIndex* pindexPr
 {
     int commitpos = GetWitnessCommitmentIndex(block);
     static const std::vector<unsigned char> nonce(32, 0x00);
-    if (commitpos != -1 && IsWitnessEnabled(pindexPrev, consensusParams) && block.vtx[0].wit.IsEmpty()) {
-        block.vtx[0].wit.vtxinwit.resize(1);
-        block.vtx[0].wit.vtxinwit[0].scriptWitness.stack.resize(1);
-        block.vtx[0].wit.vtxinwit[0].scriptWitness.stack[0] = nonce;
+    if (commitpos != -1 && IsWitnessEnabled(pindexPrev, consensusParams) && block.vtx[0]->wit.IsEmpty()) {
+        CMutableTransaction tx(*block.vtx[0]);
+        tx.wit.vtxinwit.resize(1);
+        tx.wit.vtxinwit[0].scriptWitness.stack.resize(1);
+        tx.wit.vtxinwit[0].scriptWitness.stack[0] = nonce;
+        block.vtx[0] = MakeTransactionRef(std::move(tx));
     }
 }
 
@@ -3530,7 +3533,7 @@ std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBloc
     int commitpos = GetWitnessCommitmentIndex(block);
     bool fHaveWitness = false;
     for (size_t t = 1; t < block.vtx.size(); t++) {
-        if (!block.vtx[t].wit.IsNull()) {
+        if (!block.vtx[t]->wit.IsNull()) {
             fHaveWitness = true;
             break;
         }
@@ -3551,8 +3554,8 @@ std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBloc
             out.scriptPubKey[5] = 0xed;
             memcpy(&out.scriptPubKey[6], witnessroot.begin(), 32);
             commitment = std::vector<unsigned char>(out.scriptPubKey.begin(), out.scriptPubKey.end());
-            const_cast<std::vector<CTxOut>*>(&block.vtx[0].vout)->push_back(out);
-            block.vtx[0].UpdateHash();
+            const_cast<std::vector<CTxOut>*>(&block.vtx[0]->vout)->push_back(out);
+            block.vtx[0]->UpdateHash();
         }
     }
     UpdateUncommittedBlockStructures(block, pindexPrev, consensusParams);
@@ -3601,7 +3604,7 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, const Co
 
     // Check that all transactions are finalized
     for (const auto& tx : block.vtx) {
-        if (!IsFinalTx(tx, nHeight, nLockTimeCutoff)) {
+        if (!IsFinalTx(*tx, nHeight, nLockTimeCutoff)) {
             return state.DoS(10, false, REJECT_INVALID, "bad-txns-nonfinal", false, "non-final transaction");
         }
     }
@@ -3610,8 +3613,8 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, const Co
     if (nHeight >= consensusParams.BIP34Height)
     {
         CScript expect = CScript() << nHeight;
-        if (block.vtx[0].vin[0].scriptSig.size() < expect.size() ||
-            !std::equal(expect.begin(), expect.end(), block.vtx[0].vin[0].scriptSig.begin())) {
+        if (block.vtx[0]->vin[0].scriptSig.size() < expect.size() ||
+            !std::equal(expect.begin(), expect.end(), block.vtx[0]->vin[0].scriptSig.begin())) {
             return state.DoS(100, false, REJECT_INVALID, "bad-cb-height", false, "block height mismatch in coinbase");
         }
     }
@@ -3633,11 +3636,11 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, const Co
             // The malleation check is ignored; as the transaction tree itself
             // already does not permit it, it is impossible to trigger in the
             // witness tree.
-            if (block.vtx[0].wit.vtxinwit.size() != 1 || block.vtx[0].wit.vtxinwit[0].scriptWitness.stack.size() != 1 || block.vtx[0].wit.vtxinwit[0].scriptWitness.stack[0].size() != 32) {
+            if (block.vtx[0]->wit.vtxinwit.size() != 1 || block.vtx[0]->wit.vtxinwit[0].scriptWitness.stack.size() != 1 || block.vtx[0]->wit.vtxinwit[0].scriptWitness.stack[0].size() != 32) {
                 return state.DoS(100, false, REJECT_INVALID, "bad-witness-nonce-size", true, strprintf("%s : invalid witness nonce size", __func__));
             }
-            CHash256().Write(hashWitness.begin(), 32).Write(&block.vtx[0].wit.vtxinwit[0].scriptWitness.stack[0][0], 32).Finalize(hashWitness.begin());
-            if (memcmp(hashWitness.begin(), &block.vtx[0].vout[commitpos].scriptPubKey[6], 32)) {
+            CHash256().Write(hashWitness.begin(), 32).Write(&block.vtx[0]->wit.vtxinwit[0].scriptWitness.stack[0][0], 32).Finalize(hashWitness.begin());
+            if (memcmp(hashWitness.begin(), &block.vtx[0]->vout[commitpos].scriptPubKey[6], 32)) {
                 return state.DoS(100, false, REJECT_INVALID, "bad-witness-merkle-match", true, strprintf("%s : witness merkle commitment mismatch", __func__));
             }
             fHaveWitness = true;
@@ -3647,7 +3650,7 @@ bool ContextualCheckBlock(const CBlock& block, CValidationState& state, const Co
     // No witness data is allowed in blocks that don't commit to witness data, as this would otherwise leave room for spam
     if (!fHaveWitness) {
         for (size_t i = 0; i < block.vtx.size(); i++) {
-            if (!block.vtx[i].wit.IsNull()) {
+            if (!block.vtx[i]->wit.IsNull()) {
                 return state.DoS(100, false, REJECT_INVALID, "unexpected-witness", true, strprintf("%s : unexpected witness data found", __func__));
             }
         }
@@ -4953,7 +4956,7 @@ void static ProcessGetData(CNode* pfrom, const Consensus::Params& consensusParam
                             // however we MUST always provide at least what the remote peer needs
                             typedef std::pair<unsigned int, uint256> PairType;
                             BOOST_FOREACH(PairType& pair, merkleBlock.vMatchedTxn)
-                                connman.PushMessageWithFlag(pfrom, SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::TX, block.vtx[pair.first]);
+                                connman.PushMessageWithFlag(pfrom, SERIALIZE_TRANSACTION_NO_WITNESS, NetMsgType::TX, *block.vtx[pair.first]);
                         }
                         // else
                             // no response
diff --git a/src/merkleblock.cpp b/src/merkleblock.cpp
index 31332526a9..882717ac56 100644
--- a/src/merkleblock.cpp
+++ b/src/merkleblock.cpp
@@ -23,8 +23,8 @@ CMerkleBlock::CMerkleBlock(const CBlock& block, CBloomFilter& filter)
 
     for (unsigned int i = 0; i < block.vtx.size(); i++)
     {
-        const uint256& hash = block.vtx[i].GetHash();
-        if (filter.IsRelevantAndUpdate(block.vtx[i]))
+        const uint256& hash = block.vtx[i]->GetHash();
+        if (filter.IsRelevantAndUpdate(*block.vtx[i]))
         {
             vMatch.push_back(true);
             vMatchedTxn.push_back(make_pair(i, hash));
@@ -49,7 +49,7 @@ CMerkleBlock::CMerkleBlock(const CBlock& block, const std::set<uint256>& txids)
 
     for (unsigned int i = 0; i < block.vtx.size(); i++)
     {
-        const uint256& hash = block.vtx[i].GetHash();
+        const uint256& hash = block.vtx[i]->GetHash();
         if (txids.count(hash))
             vMatch.push_back(true);
         else
diff --git a/src/miner.cpp b/src/miner.cpp
index 6ad63207cc..c40b12cd8e 100644
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -134,7 +134,7 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     pblock = &pblocktemplate->block; // pointer for convenience
 
     // Add dummy coinbase tx as first transaction
-    pblock->vtx.push_back(CTransaction());
+    pblock->vtx.emplace_back();
     pblocktemplate->vTxFees.push_back(-1); // updated at end
     pblocktemplate->vTxSigOpsCost.push_back(-1); // updated at end
 
@@ -178,7 +178,7 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;
     coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
-    pblock->vtx[0] = coinbaseTx;
+    pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
     pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
     pblocktemplate->vTxFees[0] = -nFees;
 
@@ -190,7 +190,7 @@ std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& sc
     UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
     pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
     pblock->nNonce         = 0;
-    pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(pblock->vtx[0]);
+    pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);
 
     CValidationState state;
     if (!TestBlockValidity(state, chainparams, *pblock, pindexPrev, false, false)) {
@@ -312,7 +312,7 @@ bool BlockAssembler::TestForBlock(CTxMemPool::txiter iter)
 
 void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
 {
-    pblock->vtx.push_back(iter->GetTx());
+    pblock->vtx.emplace_back(iter->GetSharedTx());
     pblocktemplate->vTxFees.push_back(iter->GetFee());
     pblocktemplate->vTxSigOpsCost.push_back(iter->GetSigOpCost());
     if (fNeedSizeAccounting) {
@@ -601,10 +601,10 @@ void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned
     }
     ++nExtraNonce;
     unsigned int nHeight = pindexPrev->nHeight+1; // Height first in coinbase required for block.version=2
-    CMutableTransaction txCoinbase(pblock->vtx[0]);
+    CMutableTransaction txCoinbase(*pblock->vtx[0]);
     txCoinbase.vin[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce)) + COINBASE_FLAGS;
     assert(txCoinbase.vin[0].scriptSig.size() <= 100);
 
-    pblock->vtx[0] = txCoinbase;
+    pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
     pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
 }
diff --git a/src/primitives/block.cpp b/src/primitives/block.cpp
index 0e6ab4dd71..95bd2211f9 100644
--- a/src/primitives/block.cpp
+++ b/src/primitives/block.cpp
@@ -27,7 +27,7 @@ std::string CBlock::ToString() const
         vtx.size());
     for (unsigned int i = 0; i < vtx.size(); i++)
     {
-        s << "  " << vtx[i].ToString() << "\n";
+        s << "  " << vtx[i]->ToString() << "\n";
     }
     return s.str();
 }
diff --git a/src/primitives/block.h b/src/primitives/block.h
index d148aec1e0..b037fc839c 100644
--- a/src/primitives/block.h
+++ b/src/primitives/block.h
@@ -73,7 +73,7 @@ class CBlock : public CBlockHeader
 {
 public:
     // network and disk
-    std::vector<CTransaction> vtx;
+    std::vector<CTransactionRef> vtx;
 
     // memory only
     mutable bool fChecked;
diff --git a/src/primitives/transaction.cpp b/src/primitives/transaction.cpp
index 7acdac17f2..91f4d29488 100644
--- a/src/primitives/transaction.cpp
+++ b/src/primitives/transaction.cpp
@@ -78,6 +78,10 @@ CTransaction::CTransaction(const CMutableTransaction &tx) : nVersion(tx.nVersion
     UpdateHash();
 }
 
+CTransaction::CTransaction(CMutableTransaction &&tx) : nVersion(tx.nVersion), vin(std::move(tx.vin)), vout(std::move(tx.vout)), wit(std::move(tx.wit)), nLockTime(tx.nLockTime) {
+    UpdateHash();
+}
+
 CTransaction& CTransaction::operator=(const CTransaction &tx) {
     *const_cast<int*>(&nVersion) = tx.nVersion;
     *const_cast<std::vector<CTxIn>*>(&vin) = tx.vin;
diff --git a/src/primitives/transaction.h b/src/primitives/transaction.h
index 1d176e5d8c..0fa85a1519 100644
--- a/src/primitives/transaction.h
+++ b/src/primitives/transaction.h
@@ -379,6 +379,7 @@ public:
 
     /** Convert a CMutableTransaction into a CTransaction. */
     CTransaction(const CMutableTransaction &tx);
+    CTransaction(CMutableTransaction &&tx);
 
     CTransaction& operator=(const CTransaction& tx);
 
@@ -392,6 +393,9 @@ public:
         }
     }
 
+    template <typename Stream>
+    CTransaction(deserialize_type, Stream& s) : CTransaction(CMutableTransaction(deserialize, s)) {}
+
     bool IsNull() const {
         return vin.empty() && vout.empty();
     }
@@ -460,12 +464,23 @@ struct CMutableTransaction
         SerializeTransaction(*this, s, ser_action);
     }
 
+    template <typename Stream>
+    CMutableTransaction(deserialize_type, Stream& s) {
+        Unserialize(s);
+    }
+
     /** Compute the hash of this CMutableTransaction. This is computed on the
      * fly, as opposed to GetHash() in CTransaction, which uses a cached result.
      */
     uint256 GetHash() const;
 };
 
+typedef std::shared_ptr<const CTransaction> CTransactionRef;
+static inline CTransactionRef MakeTransactionRef() { return std::make_shared<const CTransaction>(); }
+template <typename Tx> static inline CTransactionRef MakeTransactionRef(Tx&& txIn) { return std::make_shared<const CTransaction>(std::forward<Tx>(txIn)); }
+static inline CTransactionRef MakeTransactionRef(const CTransactionRef& txIn) { return txIn; }
+static inline CTransactionRef MakeTransactionRef(CTransactionRef&& txIn) { return std::move(txIn); }
+
 /** Compute the weight of a transaction, as defined by BIP 141 */
 int64_t GetTransactionWeight(const CTransaction &tx);
 
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 8caea14adb..154107c0dc 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -119,16 +119,16 @@ UniValue blockToJSON(const CBlock& block, const CBlockIndex* blockindex, bool tx
     result.push_back(Pair("versionHex", strprintf("%08x", block.nVersion)));
     result.push_back(Pair("merkleroot", block.hashMerkleRoot.GetHex()));
     UniValue txs(UniValue::VARR);
-    BOOST_FOREACH(const CTransaction&tx, block.vtx)
+    for(const auto& tx : block.vtx)
     {
         if(txDetails)
         {
             UniValue objTx(UniValue::VOBJ);
-            TxToJSON(tx, uint256(), objTx);
+            TxToJSON(*tx, uint256(), objTx);
             txs.push_back(objTx);
         }
         else
-            txs.push_back(tx.GetHash().GetHex());
+            txs.push_back(tx->GetHash().GetHex());
     }
     result.push_back(Pair("tx", txs));
     result.push_back(Pair("time", block.GetBlockTime()));
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index ad545bdf0d..6b0e52a309 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -557,7 +557,8 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
     UniValue transactions(UniValue::VARR);
     map<uint256, int64_t> setTxIndex;
     int i = 0;
-    BOOST_FOREACH (CTransaction& tx, pblock->vtx) {
+    for (const auto& it : pblock->vtx) {
+        const CTransaction& tx = *it;
         uint256 txHash = tx.GetHash();
         setTxIndex[txHash] = i++;
 
@@ -662,7 +663,7 @@ UniValue getblocktemplate(const JSONRPCRequest& request)
     result.push_back(Pair("previousblockhash", pblock->hashPrevBlock.GetHex()));
     result.push_back(Pair("transactions", transactions));
     result.push_back(Pair("coinbaseaux", aux));
-    result.push_back(Pair("coinbasevalue", (int64_t)pblock->vtx[0].vout[0].nValue));
+    result.push_back(Pair("coinbasevalue", (int64_t)pblock->vtx[0]->vout[0].nValue));
     result.push_back(Pair("longpollid", chainActive.Tip()->GetBlockHash().GetHex() + i64tostr(nTransactionsUpdatedLast)));
     result.push_back(Pair("target", hashTarget.GetHex()));
     result.push_back(Pair("mintime", (int64_t)pindexPrev->GetMedianTimePast()+1));
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 0656a61755..b9b81600ba 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -288,8 +288,8 @@ UniValue gettxoutproof(const JSONRPCRequest& request)
         throw JSONRPCError(RPC_INTERNAL_ERROR, "Can't read block from disk");
 
     unsigned int ntxFound = 0;
-    BOOST_FOREACH(const CTransaction&tx, block.vtx)
-        if (setTxids.count(tx.GetHash()))
+    for (const auto& tx : block.vtx)
+        if (setTxids.count(tx->GetHash()))
             ntxFound++;
     if (ntxFound != setTxids.size())
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "(Not all) transactions not found in specified block");
diff --git a/src/serialize.h b/src/serialize.h
index 91864e1b64..e28ca548c0 100644
--- a/src/serialize.h
+++ b/src/serialize.h
@@ -13,6 +13,7 @@
 #include <ios>
 #include <limits>
 #include <map>
+#include <memory>
 #include <set>
 #include <stdint.h>
 #include <string>
@@ -25,6 +26,20 @@
 static const unsigned int MAX_SIZE = 0x02000000;
 
 /**
+ * Dummy data type to identify deserializing constructors.
+ *
+ * By convention, a constructor of a type T with signature
+ *
+ *   template <typename Stream> T::T(deserialize_type, Stream& s)
+ *
+ * is a deserializing constructor, which builds the type by
+ * deserializing it from s. If T contains const fields, this
+ * is likely the only way to do so.
+ */
+struct deserialize_type {};
+constexpr deserialize_type deserialize {};
+
+/**
  * Used to bypass the rule against non-const reference to temporary
  * where it makes sense with wrappers such as CFlatData or CTxDB
  */
@@ -521,7 +536,17 @@ template<typename Stream, typename K, typename T, typename Pred, typename A> voi
 template<typename Stream, typename K, typename Pred, typename A> void Serialize(Stream& os, const std::set<K, Pred, A>& m);
 template<typename Stream, typename K, typename Pred, typename A> void Unserialize(Stream& is, std::set<K, Pred, A>& m);
 
+/**
+ * shared_ptr
+ */
+template<typename Stream, typename T> void Serialize(Stream& os, const std::shared_ptr<const T>& p);
+template<typename Stream, typename T> void Unserialize(Stream& os, std::shared_ptr<const T>& p);
 
+/**
+ * unique_ptr
+ */
+template<typename Stream, typename T> void Serialize(Stream& os, const std::unique_ptr<const T>& p);
+template<typename Stream, typename T> void Unserialize(Stream& os, std::unique_ptr<const T>& p);
 
 
 
@@ -776,6 +801,40 @@ void Unserialize(Stream& is, std::set<K, Pred, A>& m)
 
 
 /**
+ * unique_ptr
+ */
+template<typename Stream, typename T> void
+Serialize(Stream& os, const std::unique_ptr<const T>& p)
+{
+    Serialize(os, *p);
+}
+
+template<typename Stream, typename T>
+void Unserialize(Stream& is, std::unique_ptr<const T>& p)
+{
+    p.reset(new T(deserialize, is));
+}
+
+
+
+/**
+ * shared_ptr
+ */
+template<typename Stream, typename T> void
+Serialize(Stream& os, const std::shared_ptr<const T>& p)
+{
+    Serialize(os, *p);
+}
+
+template<typename Stream, typename T>
+void Unserialize(Stream& is, std::shared_ptr<const T>& p)
+{
+    p = std::make_shared<const T>(deserialize, is);
+}
+
+
+
+/**
  * Support for ADD_SERIALIZE_METHODS and READWRITE macro
  */
 struct CSerActionSerialize
diff --git a/src/test/blockencodings_tests.cpp b/src/test/blockencodings_tests.cpp
index 0ed5d62ef6..b013cda6d7 100644
--- a/src/test/blockencodings_tests.cpp
+++ b/src/test/blockencodings_tests.cpp
@@ -26,21 +26,21 @@ static CBlock BuildBlockTestCase() {
     tx.vout[0].nValue = 42;
 
     block.vtx.resize(3);
-    block.vtx[0] = tx;
+    block.vtx[0] = MakeTransactionRef(tx);
     block.nVersion = 42;
     block.hashPrevBlock = GetRandHash();
     block.nBits = 0x207fffff;
 
     tx.vin[0].prevout.hash = GetRandHash();
     tx.vin[0].prevout.n = 0;
-    block.vtx[1] = tx;
+    block.vtx[1] = MakeTransactionRef(tx);
 
     tx.vin.resize(10);
     for (size_t i = 0; i < tx.vin.size(); i++) {
         tx.vin[i].prevout.hash = GetRandHash();
         tx.vin[i].prevout.n = 0;
     }
-    block.vtx[2] = tx;
+    block.vtx[2] = MakeTransactionRef(tx);
 
     bool mutated;
     block.hashMerkleRoot = BlockMerkleRoot(block, &mutated);
@@ -59,8 +59,8 @@ BOOST_AUTO_TEST_CASE(SimpleRoundTripTest)
     TestMemPoolEntryHelper entry;
     CBlock block(BuildBlockTestCase());
 
-    pool.addUnchecked(block.vtx[2].GetHash(), entry.FromTx(block.vtx[2]));
-    BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
+    pool.addUnchecked(block.vtx[2]->GetHash(), entry.FromTx(*block.vtx[2]));
+    BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2]->GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
 
     // Do a simple ShortTxIDs RT
     {
@@ -78,14 +78,14 @@ BOOST_AUTO_TEST_CASE(SimpleRoundTripTest)
         BOOST_CHECK(!partialBlock.IsTxAvailable(1));
         BOOST_CHECK( partialBlock.IsTxAvailable(2));
 
-        BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
+        BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2]->GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
 
-        std::vector<std::shared_ptr<const CTransaction>> removed;
-        pool.removeRecursive(block.vtx[2], &removed);
+        std::vector<CTransactionRef> removed;
+        pool.removeRecursive(*block.vtx[2], &removed);
         BOOST_CHECK_EQUAL(removed.size(), 1);
 
         CBlock block2;
-        std::vector<CTransaction> vtx_missing;
+        std::vector<CTransactionRef> vtx_missing;
         BOOST_CHECK(partialBlock.FillBlock(block2, vtx_missing) == READ_STATUS_INVALID); // No transactions
 
         vtx_missing.push_back(block.vtx[2]); // Wrong transaction
@@ -152,8 +152,10 @@ BOOST_AUTO_TEST_CASE(NonCoinbasePreforwardRTTest)
     TestMemPoolEntryHelper entry;
     CBlock block(BuildBlockTestCase());
 
-    pool.addUnchecked(block.vtx[2].GetHash(), entry.FromTx(block.vtx[2]));
-    BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
+    pool.addUnchecked(block.vtx[2]->GetHash(), entry.FromTx(*block.vtx[2]));
+    BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2]->GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
+
+    uint256 txhash;
 
     // Test with pre-forwarding tx 1, but not coinbase
     {
@@ -161,8 +163,8 @@ BOOST_AUTO_TEST_CASE(NonCoinbasePreforwardRTTest)
         shortIDs.prefilledtxn.resize(1);
         shortIDs.prefilledtxn[0] = {1, block.vtx[1]};
         shortIDs.shorttxids.resize(2);
-        shortIDs.shorttxids[0] = shortIDs.GetShortID(block.vtx[0].GetHash());
-        shortIDs.shorttxids[1] = shortIDs.GetShortID(block.vtx[2].GetHash());
+        shortIDs.shorttxids[0] = shortIDs.GetShortID(block.vtx[0]->GetHash());
+        shortIDs.shorttxids[1] = shortIDs.GetShortID(block.vtx[2]->GetHash());
 
         CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
         stream << shortIDs;
@@ -176,10 +178,10 @@ BOOST_AUTO_TEST_CASE(NonCoinbasePreforwardRTTest)
         BOOST_CHECK( partialBlock.IsTxAvailable(1));
         BOOST_CHECK( partialBlock.IsTxAvailable(2));
 
-        BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
+        BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2]->GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
 
         CBlock block2;
-        std::vector<CTransaction> vtx_missing;
+        std::vector<CTransactionRef> vtx_missing;
         BOOST_CHECK(partialBlock.FillBlock(block2, vtx_missing) == READ_STATUS_INVALID); // No transactions
 
         vtx_missing.push_back(block.vtx[1]); // Wrong transaction
@@ -194,9 +196,13 @@ BOOST_AUTO_TEST_CASE(NonCoinbasePreforwardRTTest)
         BOOST_CHECK_EQUAL(block.hashMerkleRoot.ToString(), BlockMerkleRoot(block3, &mutated).ToString());
         BOOST_CHECK(!mutated);
 
-        BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
+        txhash = block.vtx[2]->GetHash();
+        block.vtx.clear();
+        block2.vtx.clear();
+        block3.vtx.clear();
+        BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
     }
-    BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[2].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
+    BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
 }
 
 BOOST_AUTO_TEST_CASE(SufficientPreforwardRTTest)
@@ -205,8 +211,10 @@ BOOST_AUTO_TEST_CASE(SufficientPreforwardRTTest)
     TestMemPoolEntryHelper entry;
     CBlock block(BuildBlockTestCase());
 
-    pool.addUnchecked(block.vtx[1].GetHash(), entry.FromTx(block.vtx[1]));
-    BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[1].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
+    pool.addUnchecked(block.vtx[1]->GetHash(), entry.FromTx(*block.vtx[1]));
+    BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[1]->GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
+
+    uint256 txhash;
 
     // Test with pre-forwarding coinbase + tx 2 with tx 1 in mempool
     {
@@ -215,7 +223,7 @@ BOOST_AUTO_TEST_CASE(SufficientPreforwardRTTest)
         shortIDs.prefilledtxn[0] = {0, block.vtx[0]};
         shortIDs.prefilledtxn[1] = {1, block.vtx[2]}; // id == 1 as it is 1 after index 1
         shortIDs.shorttxids.resize(1);
-        shortIDs.shorttxids[0] = shortIDs.GetShortID(block.vtx[1].GetHash());
+        shortIDs.shorttxids[0] = shortIDs.GetShortID(block.vtx[1]->GetHash());
 
         CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
         stream << shortIDs;
@@ -229,19 +237,22 @@ BOOST_AUTO_TEST_CASE(SufficientPreforwardRTTest)
         BOOST_CHECK( partialBlock.IsTxAvailable(1));
         BOOST_CHECK( partialBlock.IsTxAvailable(2));
 
-        BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[1].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
+        BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[1]->GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
 
         CBlock block2;
-        std::vector<CTransaction> vtx_missing;
+        std::vector<CTransactionRef> vtx_missing;
         BOOST_CHECK(partialBlock.FillBlock(block2, vtx_missing) == READ_STATUS_OK);
         BOOST_CHECK_EQUAL(block.GetHash().ToString(), block2.GetHash().ToString());
         bool mutated;
         BOOST_CHECK_EQUAL(block.hashMerkleRoot.ToString(), BlockMerkleRoot(block2, &mutated).ToString());
         BOOST_CHECK(!mutated);
 
-        BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[1].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
+        txhash = block.vtx[1]->GetHash();
+        block.vtx.clear();
+        block2.vtx.clear();
+        BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 1);
     }
-    BOOST_CHECK_EQUAL(pool.mapTx.find(block.vtx[1].GetHash())->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
+    BOOST_CHECK_EQUAL(pool.mapTx.find(txhash)->GetSharedTx().use_count(), SHARED_TX_OFFSET + 0);
 }
 
 BOOST_AUTO_TEST_CASE(EmptyBlockRoundTripTest)
@@ -255,7 +266,7 @@ BOOST_AUTO_TEST_CASE(EmptyBlockRoundTripTest)
 
     CBlock block;
     block.vtx.resize(1);
-    block.vtx[0] = coinbase;
+    block.vtx[0] = MakeTransactionRef(std::move(coinbase));
     block.nVersion = 42;
     block.hashPrevBlock = GetRandHash();
     block.nBits = 0x207fffff;
@@ -280,7 +291,7 @@ BOOST_AUTO_TEST_CASE(EmptyBlockRoundTripTest)
         BOOST_CHECK(partialBlock.IsTxAvailable(0));
 
         CBlock block2;
-        std::vector<CTransaction> vtx_missing;
+        std::vector<CTransactionRef> vtx_missing;
         BOOST_CHECK(partialBlock.FillBlock(block2, vtx_missing) == READ_STATUS_OK);
         BOOST_CHECK_EQUAL(block.GetHash().ToString(), block2.GetHash().ToString());
         BOOST_CHECK_EQUAL(block.hashMerkleRoot.ToString(), BlockMerkleRoot(block2, &mutated).ToString());
diff --git a/src/test/mempool_tests.cpp b/src/test/mempool_tests.cpp
index a73dbe725c..1faf8b6aeb 100644
--- a/src/test/mempool_tests.cpp
+++ b/src/test/mempool_tests.cpp
@@ -55,7 +55,7 @@ BOOST_AUTO_TEST_CASE(MempoolRemoveTest)
 
 
     CTxMemPool testPool(CFeeRate(0));
-    std::vector<std::shared_ptr<const CTransaction>> removed;
+    std::vector<CTransactionRef> removed;
 
     // Nothing in pool, remove should do nothing:
     testPool.removeRecursive(txParent, &removed);
@@ -410,8 +410,8 @@ BOOST_AUTO_TEST_CASE(MempoolAncestorIndexingTest)
     CheckSort<ancestor_score>(pool, sortedOrder);
 
     /* after tx6 is mined, tx7 should move up in the sort */
-    std::vector<CTransaction> vtx;
-    vtx.push_back(tx6);
+    std::vector<CTransactionRef> vtx;
+    vtx.push_back(MakeTransactionRef(tx6));
     pool.removeForBlock(vtx, 1, NULL, false);
 
     sortedOrder.erase(sortedOrder.begin()+1);
@@ -546,7 +546,7 @@ BOOST_AUTO_TEST_CASE(MempoolSizeLimitTest)
     pool.addUnchecked(tx5.GetHash(), entry.Fee(1000LL).FromTx(tx5, &pool));
     pool.addUnchecked(tx7.GetHash(), entry.Fee(9000LL).FromTx(tx7, &pool));
 
-    std::vector<CTransaction> vtx;
+    std::vector<CTransactionRef> vtx;
     SetMockTime(42);
     SetMockTime(42 + CTxMemPool::ROLLING_FEE_HALFLIFE);
     BOOST_CHECK_EQUAL(pool.GetMinFee(1).GetFeePerK(), maxFeeRateRemoved.GetFeePerK() + 1000);
diff --git a/src/test/merkle_tests.cpp b/src/test/merkle_tests.cpp
index 706d30f489..55e6852a15 100644
--- a/src/test/merkle_tests.cpp
+++ b/src/test/merkle_tests.cpp
@@ -15,8 +15,8 @@ static uint256 BlockBuildMerkleTree(const CBlock& block, bool* fMutated, std::ve
 {
     vMerkleTree.clear();
     vMerkleTree.reserve(block.vtx.size() * 2 + 16); // Safe upper bound for the number of total nodes.
-    for (std::vector<CTransaction>::const_iterator it(block.vtx.begin()); it != block.vtx.end(); ++it)
-        vMerkleTree.push_back(it->GetHash());
+    for (std::vector<CTransactionRef>::const_iterator it(block.vtx.begin()); it != block.vtx.end(); ++it)
+        vMerkleTree.push_back((*it)->GetHash());
     int j = 0;
     bool mutated = false;
     for (int nSize = block.vtx.size(); nSize > 1; nSize = (nSize + 1) / 2)
@@ -86,7 +86,7 @@ BOOST_AUTO_TEST_CASE(merkle_test)
             for (int j = 0; j < ntx; j++) {
                 CMutableTransaction mtx;
                 mtx.nLockTime = j;
-                block.vtx[j] = mtx;
+                block.vtx[j] = MakeTransactionRef(std::move(mtx));
             }
             // Compute the root of the block before mutating it.
             bool unmutatedMutated = false;
@@ -126,7 +126,7 @@ BOOST_AUTO_TEST_CASE(merkle_test)
                     std::vector<uint256> newBranch = BlockMerkleBranch(block, mtx);
                     std::vector<uint256> oldBranch = BlockGetMerkleBranch(block, merkleTree, mtx);
                     BOOST_CHECK(oldBranch == newBranch);
-                    BOOST_CHECK(ComputeMerkleRootFromBranch(block.vtx[mtx].GetHash(), newBranch, mtx) == oldRoot);
+                    BOOST_CHECK(ComputeMerkleRootFromBranch(block.vtx[mtx]->GetHash(), newBranch, mtx) == oldRoot);
                 }
             }
         }
diff --git a/src/test/miner_tests.cpp b/src/test/miner_tests.cpp
index 1ef70c343c..aea8920936 100644
--- a/src/test/miner_tests.cpp
+++ b/src/test/miner_tests.cpp
@@ -77,7 +77,7 @@ bool TestSequenceLocks(const CTransaction &tx, int flags)
 // Implemented as an additional function, rather than a separate test case,
 // to allow reusing the blockchain created in CreateNewBlock_validity.
 // Note that this test assumes blockprioritysize is 0.
-void TestPackageSelection(const CChainParams& chainparams, CScript scriptPubKey, std::vector<CTransaction *>& txFirst)
+void TestPackageSelection(const CChainParams& chainparams, CScript scriptPubKey, std::vector<CTransactionRef>& txFirst)
 {
     // Test the ancestor feerate transaction selection.
     TestMemPoolEntryHelper entry;
@@ -108,9 +108,9 @@ void TestPackageSelection(const CChainParams& chainparams, CScript scriptPubKey,
     mempool.addUnchecked(hashHighFeeTx, entry.Fee(50000).Time(GetTime()).SpendsCoinbase(false).FromTx(tx));
 
     std::unique_ptr<CBlockTemplate> pblocktemplate = BlockAssembler(chainparams).CreateNewBlock(scriptPubKey);
-    BOOST_CHECK(pblocktemplate->block.vtx[1].GetHash() == hashParentTx);
-    BOOST_CHECK(pblocktemplate->block.vtx[2].GetHash() == hashHighFeeTx);
-    BOOST_CHECK(pblocktemplate->block.vtx[3].GetHash() == hashMediumFeeTx);
+    BOOST_CHECK(pblocktemplate->block.vtx[1]->GetHash() == hashParentTx);
+    BOOST_CHECK(pblocktemplate->block.vtx[2]->GetHash() == hashHighFeeTx);
+    BOOST_CHECK(pblocktemplate->block.vtx[3]->GetHash() == hashMediumFeeTx);
 
     // Test that a package below the min relay fee doesn't get included
     tx.vin[0].prevout.hash = hashHighFeeTx;
@@ -130,8 +130,8 @@ void TestPackageSelection(const CChainParams& chainparams, CScript scriptPubKey,
     pblocktemplate = BlockAssembler(chainparams).CreateNewBlock(scriptPubKey);
     // Verify that the free tx and the low fee tx didn't get selected
     for (size_t i=0; i<pblocktemplate->block.vtx.size(); ++i) {
-        BOOST_CHECK(pblocktemplate->block.vtx[i].GetHash() != hashFreeTx);
-        BOOST_CHECK(pblocktemplate->block.vtx[i].GetHash() != hashLowFeeTx);
+        BOOST_CHECK(pblocktemplate->block.vtx[i]->GetHash() != hashFreeTx);
+        BOOST_CHECK(pblocktemplate->block.vtx[i]->GetHash() != hashLowFeeTx);
     }
 
     // Test that packages above the min relay fee do get included, even if one
@@ -142,8 +142,8 @@ void TestPackageSelection(const CChainParams& chainparams, CScript scriptPubKey,
     hashLowFeeTx = tx.GetHash();
     mempool.addUnchecked(hashLowFeeTx, entry.Fee(feeToUse+2).FromTx(tx));
     pblocktemplate = BlockAssembler(chainparams).CreateNewBlock(scriptPubKey);
-    BOOST_CHECK(pblocktemplate->block.vtx[4].GetHash() == hashFreeTx);
-    BOOST_CHECK(pblocktemplate->block.vtx[5].GetHash() == hashLowFeeTx);
+    BOOST_CHECK(pblocktemplate->block.vtx[4]->GetHash() == hashFreeTx);
+    BOOST_CHECK(pblocktemplate->block.vtx[5]->GetHash() == hashLowFeeTx);
 
     // Test that transaction selection properly updates ancestor fee
     // calculations as ancestor transactions get included in a block.
@@ -166,8 +166,8 @@ void TestPackageSelection(const CChainParams& chainparams, CScript scriptPubKey,
 
     // Verify that this tx isn't selected.
     for (size_t i=0; i<pblocktemplate->block.vtx.size(); ++i) {
-        BOOST_CHECK(pblocktemplate->block.vtx[i].GetHash() != hashFreeTx2);
-        BOOST_CHECK(pblocktemplate->block.vtx[i].GetHash() != hashLowFeeTx2);
+        BOOST_CHECK(pblocktemplate->block.vtx[i]->GetHash() != hashFreeTx2);
+        BOOST_CHECK(pblocktemplate->block.vtx[i]->GetHash() != hashLowFeeTx2);
     }
 
     // This tx will be mineable, and should cause hashLowFeeTx2 to be selected
@@ -176,7 +176,7 @@ void TestPackageSelection(const CChainParams& chainparams, CScript scriptPubKey,
     tx.vout[0].nValue = 100000000 - 10000; // 10k satoshi fee
     mempool.addUnchecked(tx.GetHash(), entry.Fee(10000).FromTx(tx));
     pblocktemplate = BlockAssembler(chainparams).CreateNewBlock(scriptPubKey);
-    BOOST_CHECK(pblocktemplate->block.vtx[8].GetHash() == hashLowFeeTx2);
+    BOOST_CHECK(pblocktemplate->block.vtx[8]->GetHash() == hashLowFeeTx2);
 }
 
 // NOTE: These tests rely on CreateNewBlock doing its own self-validation!
@@ -203,23 +203,23 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
     // We can't make transactions until we have inputs
     // Therefore, load 100 blocks :)
     int baseheight = 0;
-    std::vector<CTransaction*>txFirst;
+    std::vector<CTransactionRef> txFirst;
     for (unsigned int i = 0; i < sizeof(blockinfo)/sizeof(*blockinfo); ++i)
     {
         CBlock *pblock = &pblocktemplate->block; // pointer for convenience
         pblock->nVersion = 1;
         pblock->nTime = chainActive.Tip()->GetMedianTimePast()+1;
-        CMutableTransaction txCoinbase(pblock->vtx[0]);
+        CMutableTransaction txCoinbase(*pblock->vtx[0]);
         txCoinbase.nVersion = 1;
         txCoinbase.vin[0].scriptSig = CScript();
         txCoinbase.vin[0].scriptSig.push_back(blockinfo[i].extranonce);
         txCoinbase.vin[0].scriptSig.push_back(chainActive.Height());
         txCoinbase.vout[0].scriptPubKey = CScript();
-        pblock->vtx[0] = CTransaction(txCoinbase);
+        pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
         if (txFirst.size() == 0)
             baseheight = chainActive.Height();
         if (txFirst.size() < 4)
-            txFirst.push_back(new CTransaction(pblock->vtx[0]));
+            txFirst.push_back(pblock->vtx[0]);
         pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
         pblock->nNonce = blockinfo[i].nonce;
         BOOST_CHECK(ProcessNewBlock(chainparams, pblock, true, NULL, NULL));
@@ -485,9 +485,6 @@ BOOST_AUTO_TEST_CASE(CreateNewBlock_validity)
 
     TestPackageSelection(chainparams, scriptPubKey, txFirst);
 
-    BOOST_FOREACH(CTransaction *_tx, txFirst)
-        delete _tx;
-
     fCheckpointsEnabled = true;
 }
 
diff --git a/src/test/pmt_tests.cpp b/src/test/pmt_tests.cpp
index c773129640..e6b689bc6c 100644
--- a/src/test/pmt_tests.cpp
+++ b/src/test/pmt_tests.cpp
@@ -45,14 +45,14 @@ BOOST_AUTO_TEST_CASE(pmt_test1)
         for (unsigned int j=0; j<nTx; j++) {
             CMutableTransaction tx;
             tx.nLockTime = j; // actual transaction data doesn't matter; just make the nLockTime's unique
-            block.vtx.push_back(CTransaction(tx));
+            block.vtx.push_back(MakeTransactionRef(std::move(tx)));
         }
 
         // calculate actual merkle root and height
         uint256 merkleRoot1 = BlockMerkleRoot(block);
         std::vector<uint256> vTxid(nTx, uint256());
         for (unsigned int j=0; j<nTx; j++)
-            vTxid[j] = block.vtx[j].GetHash();
+            vTxid[j] = block.vtx[j]->GetHash();
         int nHeight = 1, nTx_ = nTx;
         while (nTx_ > 1) {
             nTx_ = (nTx_+1)/2;
diff --git a/src/test/policyestimator_tests.cpp b/src/test/policyestimator_tests.cpp
index 38aaaba267..7dc8f226c9 100644
--- a/src/test/policyestimator_tests.cpp
+++ b/src/test/policyestimator_tests.cpp
@@ -45,7 +45,7 @@ BOOST_AUTO_TEST_CASE(BlockPolicyEstimates)
     CFeeRate baseRate(basefee, GetVirtualTransactionSize(tx));
 
     // Create a fake block
-    std::vector<CTransaction> block;
+    std::vector<CTransactionRef> block;
     int blocknum = 0;
 
     // Loop through 200 blocks
@@ -66,9 +66,9 @@ BOOST_AUTO_TEST_CASE(BlockPolicyEstimates)
             // 9/10 blocks add 2nd highest and so on until ...
             // 1/10 blocks add lowest fee transactions
             while (txHashes[9-h].size()) {
-                std::shared_ptr<const CTransaction> ptx = mpool.get(txHashes[9-h].back());
+                CTransactionRef ptx = mpool.get(txHashes[9-h].back());
                 if (ptx)
-                    block.push_back(*ptx);
+                    block.push_back(ptx);
                 txHashes[9-h].pop_back();
             }
         }
@@ -143,9 +143,9 @@ BOOST_AUTO_TEST_CASE(BlockPolicyEstimates)
     // Estimates should still not be below original
     for (int j = 0; j < 10; j++) {
         while(txHashes[j].size()) {
-            std::shared_ptr<const CTransaction> ptx = mpool.get(txHashes[j].back());
+            CTransactionRef ptx = mpool.get(txHashes[j].back());
             if (ptx)
-                block.push_back(*ptx);
+                block.push_back(ptx);
             txHashes[j].pop_back();
         }
     }
@@ -163,9 +163,9 @@ BOOST_AUTO_TEST_CASE(BlockPolicyEstimates)
                 tx.vin[0].prevout.n = 10000*blocknum+100*j+k;
                 uint256 hash = tx.GetHash();
                 mpool.addUnchecked(hash, entry.Fee(feeV[j]).Time(GetTime()).Priority(0).Height(blocknum).FromTx(tx, &mpool));
-                std::shared_ptr<const CTransaction> ptx = mpool.get(hash);
+                CTransactionRef ptx = mpool.get(hash);
                 if (ptx)
-                    block.push_back(*ptx);
+                    block.push_back(ptx);
 
             }
         }
diff --git a/src/test/test_bitcoin.cpp b/src/test/test_bitcoin.cpp
index 3f7416f23f..6cbe314a76 100644
--- a/src/test/test_bitcoin.cpp
+++ b/src/test/test_bitcoin.cpp
@@ -101,7 +101,7 @@ TestChain100Setup::TestChain100Setup() : TestingSetup(CBaseChainParams::REGTEST)
     {
         std::vector<CMutableTransaction> noTxns;
         CBlock b = CreateAndProcessBlock(noTxns, scriptPubKey);
-        coinbaseTxns.push_back(b.vtx[0]);
+        coinbaseTxns.push_back(*b.vtx[0]);
     }
 }
 
@@ -119,7 +119,7 @@ TestChain100Setup::CreateAndProcessBlock(const std::vector<CMutableTransaction>&
     // Replace mempool-selected txns with just coinbase plus passed-in txns:
     block.vtx.resize(1);
     BOOST_FOREACH(const CMutableTransaction& tx, txns)
-        block.vtx.push_back(tx);
+        block.vtx.push_back(MakeTransactionRef(tx));
     // IncrementExtraNonce creates a valid coinbase and merkleRoot
     unsigned int extraNonce = 0;
     IncrementExtraNonce(&block, chainActive.Tip(), extraNonce);
@@ -137,12 +137,12 @@ TestChain100Setup::~TestChain100Setup()
 }
 
 
-CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(CMutableTransaction &tx, CTxMemPool *pool) {
+CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(const CMutableTransaction &tx, CTxMemPool *pool) {
     CTransaction txn(tx);
     return FromTx(txn, pool);
 }
 
-CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(CTransaction &txn, CTxMemPool *pool) {
+CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(const CTransaction &txn, CTxMemPool *pool) {
     bool hasNoDependencies = pool ? pool->HasNoInputsOf(txn) : hadNoDependencies;
     // Hack to assume either its completely dependent on other mempool txs or not at all
     CAmount inChainValue = hasNoDependencies ? txn.GetValueOut() : 0;
diff --git a/src/test/test_bitcoin.h b/src/test/test_bitcoin.h
index 9819a7097d..3dea20445d 100644
--- a/src/test/test_bitcoin.h
+++ b/src/test/test_bitcoin.h
@@ -79,8 +79,8 @@ struct TestMemPoolEntryHelper
         nFee(0), nTime(0), dPriority(0.0), nHeight(1),
         hadNoDependencies(false), spendsCoinbase(false), sigOpCost(4) { }
     
-    CTxMemPoolEntry FromTx(CMutableTransaction &tx, CTxMemPool *pool = NULL);
-    CTxMemPoolEntry FromTx(CTransaction &tx, CTxMemPool *pool = NULL);
+    CTxMemPoolEntry FromTx(const CMutableTransaction &tx, CTxMemPool *pool = NULL);
+    CTxMemPoolEntry FromTx(const CTransaction &tx, CTxMemPool *pool = NULL);
 
     // Change the default value
     TestMemPoolEntryHelper &Fee(CAmount _fee) { nFee = _fee; return *this; }
diff --git a/src/txmempool.cpp b/src/txmempool.cpp
index 45135a5f73..417a88cbef 100644
--- a/src/txmempool.cpp
+++ b/src/txmempool.cpp
@@ -24,7 +24,7 @@ CTxMemPoolEntry::CTxMemPoolEntry(const CTransaction& _tx, const CAmount& _nFee,
                                  int64_t _nTime, double _entryPriority, unsigned int _entryHeight,
                                  bool poolHasNoInputsOf, CAmount _inChainInputValue,
                                  bool _spendsCoinbase, int64_t _sigOpsCost, LockPoints lp):
-    tx(std::make_shared<CTransaction>(_tx)), nFee(_nFee), nTime(_nTime), entryPriority(_entryPriority), entryHeight(_entryHeight),
+    tx(MakeTransactionRef(_tx)), nFee(_nFee), nTime(_nTime), entryPriority(_entryPriority), entryHeight(_entryHeight),
     hadNoDependencies(poolHasNoInputsOf), inChainInputValue(_inChainInputValue),
     spendsCoinbase(_spendsCoinbase), sigOpCost(_sigOpsCost), lockPoints(lp)
 {
@@ -503,7 +503,7 @@ void CTxMemPool::CalculateDescendants(txiter entryit, setEntries &setDescendants
     }
 }
 
-void CTxMemPool::removeRecursive(const CTransaction &origTx, std::vector<std::shared_ptr<const CTransaction>>* removed)
+void CTxMemPool::removeRecursive(const CTransaction &origTx, std::vector<CTransactionRef>* removed)
 {
     // Remove transaction from memory pool
     {
@@ -576,7 +576,7 @@ void CTxMemPool::removeForReorg(const CCoinsViewCache *pcoins, unsigned int nMem
     RemoveStaged(setAllRemoves, false);
 }
 
-void CTxMemPool::removeConflicts(const CTransaction &tx, std::vector<std::shared_ptr<const CTransaction>>* removed)
+void CTxMemPool::removeConflicts(const CTransaction &tx, std::vector<CTransactionRef>* removed)
 {
     // Remove transactions which depend on inputs of tx, recursively
     LOCK(cs);
@@ -596,29 +596,29 @@ void CTxMemPool::removeConflicts(const CTransaction &tx, std::vector<std::shared
 /**
  * Called when a block is connected. Removes from mempool and updates the miner fee estimator.
  */
-void CTxMemPool::removeForBlock(const std::vector<CTransaction>& vtx, unsigned int nBlockHeight,
-                                std::vector<std::shared_ptr<const CTransaction>>* conflicts, bool fCurrentEstimate)
+void CTxMemPool::removeForBlock(const std::vector<CTransactionRef>& vtx, unsigned int nBlockHeight,
+                                std::vector<CTransactionRef>* conflicts, bool fCurrentEstimate)
 {
     LOCK(cs);
     std::vector<CTxMemPoolEntry> entries;
-    BOOST_FOREACH(const CTransaction& tx, vtx)
+    for (const auto& tx : vtx)
     {
-        uint256 hash = tx.GetHash();
+        uint256 hash = tx->GetHash();
 
         indexed_transaction_set::iterator i = mapTx.find(hash);
         if (i != mapTx.end())
             entries.push_back(*i);
     }
-    BOOST_FOREACH(const CTransaction& tx, vtx)
+    for (const auto& tx : vtx)
     {
-        txiter it = mapTx.find(tx.GetHash());
+        txiter it = mapTx.find(tx->GetHash());
         if (it != mapTx.end()) {
             setEntries stage;
             stage.insert(it);
             RemoveStaged(stage, true);
         }
-        removeConflicts(tx, conflicts);
-        ClearPrioritisation(tx.GetHash());
+        removeConflicts(*tx, conflicts);
+        ClearPrioritisation(tx->GetHash());
     }
     // After the txs in the new block have been removed from the mempool, update policy estimates
     minerPolicyEstimator->processBlock(nBlockHeight, entries, fCurrentEstimate);
@@ -851,7 +851,7 @@ std::vector<TxMempoolInfo> CTxMemPool::infoAll() const
     return ret;
 }
 
-std::shared_ptr<const CTransaction> CTxMemPool::get(const uint256& hash) const
+CTransactionRef CTxMemPool::get(const uint256& hash) const
 {
     LOCK(cs);
     indexed_transaction_set::const_iterator i = mapTx.find(hash);
@@ -978,7 +978,7 @@ bool CCoinsViewMemPool::GetCoins(const uint256 &txid, CCoins &coins) const {
     // If an entry in the mempool exists, always return that one, as it's guaranteed to never
     // conflict with the underlying cache, and it cannot have pruned entries (as it contains full)
     // transactions. First checking the underlying cache risks returning a pruned entry instead.
-    shared_ptr<const CTransaction> ptx = mempool.get(txid);
+    CTransactionRef ptx = mempool.get(txid);
     if (ptx) {
         coins = CCoins(*ptx, MEMPOOL_HEIGHT);
         return true;
diff --git a/src/txmempool.h b/src/txmempool.h
index 9b0ca4655e..29b59363a2 100644
--- a/src/txmempool.h
+++ b/src/txmempool.h
@@ -80,7 +80,7 @@ class CTxMemPool;
 class CTxMemPoolEntry
 {
 private:
-    std::shared_ptr<const CTransaction> tx;
+    CTransactionRef tx;
     CAmount nFee;              //!< Cached to avoid expensive parent-transaction lookups
     size_t nTxWeight;          //!< ... and avoid recomputing tx weight (also used for GetTxSize())
     size_t nModSize;           //!< ... and modified size for priority
@@ -118,7 +118,7 @@ public:
     CTxMemPoolEntry(const CTxMemPoolEntry& other);
 
     const CTransaction& GetTx() const { return *this->tx; }
-    std::shared_ptr<const CTransaction> GetSharedTx() const { return this->tx; }
+    CTransactionRef GetSharedTx() const { return this->tx; }
     /**
      * Fast calculation of lower bound of current priority as update
      * from entry priority. Only inputs that were originally in-chain will age.
@@ -322,7 +322,7 @@ class CBlockPolicyEstimator;
 struct TxMempoolInfo
 {
     /** The transaction itself */
-    std::shared_ptr<const CTransaction> tx;
+    CTransactionRef tx;
 
     /** Time the transaction entered the mempool. */
     int64_t nTime;
@@ -527,11 +527,11 @@ public:
     bool addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry, bool fCurrentEstimate = true);
     bool addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry, setEntries &setAncestors, bool fCurrentEstimate = true);
 
-    void removeRecursive(const CTransaction &tx, std::vector<std::shared_ptr<const CTransaction>>* removed = NULL);
+    void removeRecursive(const CTransaction &tx, std::vector<CTransactionRef>* removed = NULL);
     void removeForReorg(const CCoinsViewCache *pcoins, unsigned int nMemPoolHeight, int flags);
-    void removeConflicts(const CTransaction &tx, std::vector<std::shared_ptr<const CTransaction>>* removed = NULL);
-    void removeForBlock(const std::vector<CTransaction>& vtx, unsigned int nBlockHeight,
-                        std::vector<std::shared_ptr<const CTransaction>>* conflicts = NULL, bool fCurrentEstimate = true);
+    void removeConflicts(const CTransaction &tx, std::vector<CTransactionRef>* removed = NULL);
+    void removeForBlock(const std::vector<CTransactionRef>& vtx, unsigned int nBlockHeight,
+                        std::vector<CTransactionRef>* conflicts = NULL, bool fCurrentEstimate = true);
     void clear();
     void _clear(); //lock free
     bool CompareDepthAndScore(const uint256& hasha, const uint256& hashb);
@@ -623,7 +623,7 @@ public:
         return (mapTx.count(hash) != 0);
     }
 
-    std::shared_ptr<const CTransaction> get(const uint256& hash) const;
+    CTransactionRef get(const uint256& hash) const;
     TxMempoolInfo info(const uint256& hash) const;
     std::vector<TxMempoolInfo> infoAll() const;
 
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 3e18cb702c..2e512fd57f 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -1492,7 +1492,7 @@ int CWallet::ScanForWalletTransactions(CBlockIndex* pindexStart, bool fUpdate)
             int posInBlock;
             for (posInBlock = 0; posInBlock < (int)block.vtx.size(); posInBlock++)
             {
-                if (AddToWalletIfInvolvingMe(block.vtx[posInBlock], pindex, posInBlock, fUpdate))
+                if (AddToWalletIfInvolvingMe(*block.vtx[posInBlock], pindex, posInBlock, fUpdate))
                     ret++;
             }
             pindex = chainActive.Next(pindex);