Merge #8580: Make CTransaction actually immutable

81e3228 Make CTransaction actually immutable (Pieter Wuille)
42fd8de Make DecodeHexTx return a CMutableTransaction (Pieter Wuille)
c3f5673 Make CWalletTx store a CTransactionRef instead of inheriting (Pieter Wuille)
a188353 Switch GetTransaction to returning a CTransactionRef (Pieter Wuille)

28 files changed, 287 insertions, 292 deletions

diff --git a/src/bench/coin_selection.cpp b/src/bench/coin_selection.cpp
index 7091ee3e11..32690fe484 100644
--- a/src/bench/coin_selection.cpp
+++ b/src/bench/coin_selection.cpp
@@ -19,7 +19,7 @@ static void addCoin(const CAmount& nValue, const CWallet& wallet, vector<COutput
     tx.nLockTime = nextLockTime++; // so all transactions get different hashes
     tx.vout.resize(nInput + 1);
     tx.vout[nInput].nValue = nValue;
-    CWalletTx* wtx = new CWalletTx(&wallet, tx);
+    CWalletTx* wtx = new CWalletTx(&wallet, MakeTransactionRef(std::move(tx)));
 
     int nAge = 6 * 24;
     COutput output(wtx, nInput, nAge, true, true);
diff --git a/src/bitcoin-tx.cpp b/src/bitcoin-tx.cpp
index 346d8e180d..1ed1449f03 100644
--- a/src/bitcoin-tx.cpp
+++ b/src/bitcoin-tx.cpp
@@ -623,7 +623,7 @@ static int CommandLineRawTx(int argc, char* argv[])
             argv++;
         }
 
-        CTransaction txDecodeTmp;
+        CMutableTransaction tx;
         int startArg;
 
         if (!fCreateBlank) {
@@ -636,15 +636,13 @@ static int CommandLineRawTx(int argc, char* argv[])
             if (strHexTx == "-")                 // "-" implies standard input
                 strHexTx = readStdin();
 
-            if (!DecodeHexTx(txDecodeTmp, strHexTx, true))
+            if (!DecodeHexTx(tx, strHexTx, true))
                 throw std::runtime_error("invalid transaction encoding");
 
             startArg = 2;
         } else
             startArg = 1;
 
-        CMutableTransaction tx(txDecodeTmp);
-
         for (int i = startArg; i < argc; i++) {
             std::string arg = argv[i];
             std::string key, value;
diff --git a/src/core_io.h b/src/core_io.h
index 5aecbc4489..4344290bb8 100644
--- a/src/core_io.h
+++ b/src/core_io.h
@@ -11,13 +11,14 @@
 class CBlock;
 class CScript;
 class CTransaction;
+class CMutableTransaction;
 class uint256;
 class UniValue;
 
 // core_read.cpp
 CScript ParseScript(const std::string& s);
 std::string ScriptToAsmStr(const CScript& script, const bool fAttemptSighashDecode = false);
-bool DecodeHexTx(CTransaction& tx, const std::string& strHexTx, bool fTryNoWitness = false);
+bool DecodeHexTx(CMutableTransaction& tx, const std::string& strHexTx, bool fTryNoWitness = false);
 bool DecodeHexBlk(CBlock&, const std::string& strHexBlk);
 uint256 ParseHashUV(const UniValue& v, const std::string& strName);
 uint256 ParseHashStr(const std::string&, const std::string& strName);
diff --git a/src/core_read.cpp b/src/core_read.cpp
index 7cfda6dd6d..b6d0285459 100644
--- a/src/core_read.cpp
+++ b/src/core_read.cpp
@@ -90,7 +90,7 @@ CScript ParseScript(const std::string& s)
     return result;
 }
 
-bool DecodeHexTx(CTransaction& tx, const std::string& strHexTx, bool fTryNoWitness)
+bool DecodeHexTx(CMutableTransaction& tx, const std::string& strHexTx, bool fTryNoWitness)
 {
     if (!IsHex(strHexTx))
         return false;
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index 747167264b..b1283c236c 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -1594,8 +1594,7 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
 
         deque<COutPoint> vWorkQueue;
         vector<uint256> vEraseQueue;
-        CTransaction tx;
-        vRecv >> tx;
+        CTransaction tx(deserialize, vRecv);
 
         CInv inv(MSG_TX, tx.GetHash());
         pfrom->AddInventoryKnown(inv);
diff --git a/src/primitives/transaction.cpp b/src/primitives/transaction.cpp
index 91f4d29488..11d7eace55 100644
--- a/src/primitives/transaction.cpp
+++ b/src/primitives/transaction.cpp
@@ -62,9 +62,9 @@ uint256 CMutableTransaction::GetHash() const
     return SerializeHash(*this, SER_GETHASH, SERIALIZE_TRANSACTION_NO_WITNESS);
 }
 
-void CTransaction::UpdateHash() const
+uint256 CTransaction::ComputeHash() const
 {
-    *const_cast<uint256*>(&hash) = SerializeHash(*this, SER_GETHASH, SERIALIZE_TRANSACTION_NO_WITNESS);
+    return SerializeHash(*this, SER_GETHASH, SERIALIZE_TRANSACTION_NO_WITNESS);
 }
 
 uint256 CTransaction::GetWitnessHash() const
@@ -72,25 +72,10 @@ uint256 CTransaction::GetWitnessHash() const
     return SerializeHash(*this, SER_GETHASH, 0);
 }
 
-CTransaction::CTransaction() : nVersion(CTransaction::CURRENT_VERSION), vin(), vout(), nLockTime(0) { }
-
-CTransaction::CTransaction(const CMutableTransaction &tx) : nVersion(tx.nVersion), vin(tx.vin), vout(tx.vout), wit(tx.wit), nLockTime(tx.nLockTime) {
-    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;
-    *const_cast<std::vector<CTxOut>*>(&vout) = tx.vout;
-    *const_cast<CTxWitness*>(&wit) = tx.wit;
-    *const_cast<unsigned int*>(&nLockTime) = tx.nLockTime;
-    *const_cast<uint256*>(&hash) = tx.hash;
-    return *this;
-}
+/* For backward compatibility, the hash is initialized to 0. TODO: remove the need for this default constructor entirely. */
+CTransaction::CTransaction() : nVersion(CTransaction::CURRENT_VERSION), vin(), vout(), nLockTime(0), hash() {}
+CTransaction::CTransaction(const CMutableTransaction &tx) : nVersion(tx.nVersion), vin(tx.vin), vout(tx.vout), wit(tx.wit), nLockTime(tx.nLockTime), hash(ComputeHash()) {}
+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), hash(ComputeHash()) {}
 
 CAmount CTransaction::GetValueOut() const
 {
diff --git a/src/primitives/transaction.h b/src/primitives/transaction.h
index 0fa85a1519..66fefafef5 100644
--- a/src/primitives/transaction.h
+++ b/src/primitives/transaction.h
@@ -286,73 +286,81 @@ struct CMutableTransaction;
  *   - CTxWitness wit;
  * - uint32_t nLockTime
  */
-template<typename Stream, typename Operation, typename TxType>
-inline void SerializeTransaction(TxType& tx, Stream& s, Operation ser_action) {
+template<typename Stream, typename TxType>
+inline void UnserializeTransaction(TxType& tx, Stream& s) {
     const bool fAllowWitness = !(s.GetVersion() & SERIALIZE_TRANSACTION_NO_WITNESS);
 
-    READWRITE(*const_cast<int32_t*>(&tx.nVersion));
+    s >> tx.nVersion;
     unsigned char flags = 0;
-    if (ser_action.ForRead()) {
-        const_cast<std::vector<CTxIn>*>(&tx.vin)->clear();
-        const_cast<std::vector<CTxOut>*>(&tx.vout)->clear();
-        const_cast<CTxWitness*>(&tx.wit)->SetNull();
-        /* Try to read the vin. In case the dummy is there, this will be read as an empty vector. */
-        READWRITE(*const_cast<std::vector<CTxIn>*>(&tx.vin));
-        if (tx.vin.size() == 0 && fAllowWitness) {
-            /* We read a dummy or an empty vin. */
-            READWRITE(flags);
-            if (flags != 0) {
-                READWRITE(*const_cast<std::vector<CTxIn>*>(&tx.vin));
-                READWRITE(*const_cast<std::vector<CTxOut>*>(&tx.vout));
-            }
-        } else {
-            /* We read a non-empty vin. Assume a normal vout follows. */
-            READWRITE(*const_cast<std::vector<CTxOut>*>(&tx.vout));
-        }
-        if ((flags & 1) && fAllowWitness) {
-            /* The witness flag is present, and we support witnesses. */
-            flags ^= 1;
-            const_cast<CTxWitness*>(&tx.wit)->vtxinwit.resize(tx.vin.size());
-            READWRITE(tx.wit);
-        }
-        if (flags) {
-            /* Unknown flag in the serialization */
-            throw std::ios_base::failure("Unknown transaction optional data");
+    tx.vin.clear();
+    tx.vout.clear();
+    tx.wit.SetNull();
+    /* Try to read the vin. In case the dummy is there, this will be read as an empty vector. */
+    s >> tx.vin;
+    if (tx.vin.size() == 0 && fAllowWitness) {
+        /* We read a dummy or an empty vin. */
+        s >> flags;
+        if (flags != 0) {
+            s >> tx.vin;
+            s >> tx.vout;
         }
     } else {
-        // Consistency check
-        assert(tx.wit.vtxinwit.size() <= tx.vin.size());
-        if (fAllowWitness) {
-            /* Check whether witnesses need to be serialized. */
-            if (!tx.wit.IsNull()) {
-                flags |= 1;
-            }
-        }
-        if (flags) {
-            /* Use extended format in case witnesses are to be serialized. */
-            std::vector<CTxIn> vinDummy;
-            READWRITE(vinDummy);
-            READWRITE(flags);
+        /* We read a non-empty vin. Assume a normal vout follows. */
+        s >> tx.vout;
+    }
+    if ((flags & 1) && fAllowWitness) {
+        /* The witness flag is present, and we support witnesses. */
+        flags ^= 1;
+        tx.wit.vtxinwit.resize(tx.vin.size());
+        s >> tx.wit;
+    }
+    if (flags) {
+        /* Unknown flag in the serialization */
+        throw std::ios_base::failure("Unknown transaction optional data");
+    }
+    s >> tx.nLockTime;
+}
+
+template<typename Stream, typename TxType>
+inline void SerializeTransaction(const TxType& tx, Stream& s) {
+    const bool fAllowWitness = !(s.GetVersion() & SERIALIZE_TRANSACTION_NO_WITNESS);
+
+    s << tx.nVersion;
+    unsigned char flags = 0;
+    // Consistency check
+    assert(tx.wit.vtxinwit.size() <= tx.vin.size());
+    if (fAllowWitness) {
+        /* Check whether witnesses need to be serialized. */
+        if (!tx.wit.IsNull()) {
+            flags |= 1;
         }
-        READWRITE(*const_cast<std::vector<CTxIn>*>(&tx.vin));
-        READWRITE(*const_cast<std::vector<CTxOut>*>(&tx.vout));
-        if (flags & 1) {
-            const_cast<CTxWitness*>(&tx.wit)->vtxinwit.resize(tx.vin.size());
-            READWRITE(tx.wit);
+    }
+    if (flags) {
+        /* Use extended format in case witnesses are to be serialized. */
+        std::vector<CTxIn> vinDummy;
+        s << vinDummy;
+        s << flags;
+    }
+    s << tx.vin;
+    s << tx.vout;
+    if (flags & 1) {
+        for (size_t i = 0; i < tx.vin.size(); i++) {
+            if (i < tx.wit.vtxinwit.size()) {
+                s << tx.wit.vtxinwit[i];
+            } else {
+                s << CTxInWitness();
+            }
         }
     }
-    READWRITE(*const_cast<uint32_t*>(&tx.nLockTime));
+    s << tx.nLockTime;
 }
 
+
 /** The basic transaction that is broadcasted on the network and contained in
  * blocks.  A transaction can contain multiple inputs and outputs.
  */
 class CTransaction
 {
-private:
-    /** Memory only. */
-    const uint256 hash;
-
 public:
     // Default transaction version.
     static const int32_t CURRENT_VERSION=1;
@@ -374,6 +382,13 @@ public:
     CTxWitness wit; // Not const: can change without invalidating the txid cache
     const uint32_t nLockTime;
 
+private:
+    /** Memory only. */
+    const uint256 hash;
+
+    uint256 ComputeHash() const;
+
+public:
     /** Construct a CTransaction that qualifies as IsNull() */
     CTransaction();
 
@@ -381,18 +396,13 @@ public:
     CTransaction(const CMutableTransaction &tx);
     CTransaction(CMutableTransaction &&tx);
 
-    CTransaction& operator=(const CTransaction& tx);
-
-    ADD_SERIALIZE_METHODS;
-
-    template <typename Stream, typename Operation>
-    inline void SerializationOp(Stream& s, Operation ser_action) {
-        SerializeTransaction(*this, s, ser_action);
-        if (ser_action.ForRead()) {
-            UpdateHash();
-        }
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        SerializeTransaction(*this, s);
     }
 
+    /** This deserializing constructor is provided instead of an Unserialize method.
+     *  Unserialize is not possible, since it would require overwriting const fields. */
     template <typename Stream>
     CTransaction(deserialize_type, Stream& s) : CTransaction(CMutableTransaction(deserialize, s)) {}
 
@@ -417,7 +427,7 @@ public:
 
     // Compute modified tx size for priority calculation (optionally given tx size)
     unsigned int CalculateModifiedSize(unsigned int nTxSize=0) const;
-    
+
     /**
      * Get the total transaction size in bytes, including witness data.
      * "Total Size" defined in BIP141 and BIP144.
@@ -441,8 +451,6 @@ public:
     }
 
     std::string ToString() const;
-
-    void UpdateHash() const;
 };
 
 /** A mutable version of CTransaction. */
@@ -457,11 +465,15 @@ struct CMutableTransaction
     CMutableTransaction();
     CMutableTransaction(const CTransaction& tx);
 
-    ADD_SERIALIZE_METHODS;
+    template <typename Stream>
+    inline void Serialize(Stream& s) const {
+        SerializeTransaction(*this, s);
+    }
 
-    template <typename Stream, typename Operation>
-    inline void SerializationOp(Stream& s, Operation ser_action) {
-        SerializeTransaction(*this, s, ser_action);
+
+    template <typename Stream>
+    inline void Unserialize(Stream& s) {
+        UnserializeTransaction(*this, s);
     }
 
     template <typename Stream>
diff --git a/src/qt/coincontroldialog.cpp b/src/qt/coincontroldialog.cpp
index 704e2e2569..4d34bf95e9 100644
--- a/src/qt/coincontroldialog.cpp
+++ b/src/qt/coincontroldialog.cpp
@@ -470,21 +470,21 @@ void CoinControlDialog::updateLabels(WalletModel *model, QDialog* dialog)
         nQuantity++;
 
         // Amount
-        nAmount += out.tx->vout[out.i].nValue;
+        nAmount += out.tx->tx->vout[out.i].nValue;
 
         // Priority
-        dPriorityInputs += (double)out.tx->vout[out.i].nValue * (out.nDepth+1);
+        dPriorityInputs += (double)out.tx->tx->vout[out.i].nValue * (out.nDepth+1);
 
         // Bytes
         CTxDestination address;
         int witnessversion = 0;
         std::vector<unsigned char> witnessprogram;
-        if (out.tx->vout[out.i].scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram))
+        if (out.tx->tx->vout[out.i].scriptPubKey.IsWitnessProgram(witnessversion, witnessprogram))
         {
             nBytesInputs += (32 + 4 + 1 + (107 / WITNESS_SCALE_FACTOR) + 4);
             fWitness = true;
         }
-        else if(ExtractDestination(out.tx->vout[out.i].scriptPubKey, address))
+        else if(ExtractDestination(out.tx->tx->vout[out.i].scriptPubKey, address))
         {
             CPubKey pubkey;
             CKeyID *keyid = boost::get<CKeyID>(&address);
@@ -677,7 +677,7 @@ void CoinControlDialog::updateView()
         CAmount nSum = 0;
         int nChildren = 0;
         BOOST_FOREACH(const COutput& out, coins.second) {
-            nSum += out.tx->vout[out.i].nValue;
+            nSum += out.tx->tx->vout[out.i].nValue;
             nChildren++;
 
             CCoinControlWidgetItem *itemOutput;
@@ -689,7 +689,7 @@ void CoinControlDialog::updateView()
             // address
             CTxDestination outputAddress;
             QString sAddress = "";
-            if(ExtractDestination(out.tx->vout[out.i].scriptPubKey, outputAddress))
+            if(ExtractDestination(out.tx->tx->vout[out.i].scriptPubKey, outputAddress))
             {
                 sAddress = QString::fromStdString(CBitcoinAddress(outputAddress).ToString());
 
@@ -714,8 +714,8 @@ void CoinControlDialog::updateView()
             }
 
             // amount
-            itemOutput->setText(COLUMN_AMOUNT, BitcoinUnits::format(nDisplayUnit, out.tx->vout[out.i].nValue));
-            itemOutput->setData(COLUMN_AMOUNT, Qt::UserRole, QVariant((qlonglong)out.tx->vout[out.i].nValue)); // padding so that sorting works correctly
+            itemOutput->setText(COLUMN_AMOUNT, BitcoinUnits::format(nDisplayUnit, out.tx->tx->vout[out.i].nValue));
+            itemOutput->setData(COLUMN_AMOUNT, Qt::UserRole, QVariant((qlonglong)out.tx->tx->vout[out.i].nValue)); // padding so that sorting works correctly
 
             // date
             itemOutput->setText(COLUMN_DATE, GUIUtil::dateTimeStr(out.tx->GetTxTime()));
diff --git a/src/qt/transactiondesc.cpp b/src/qt/transactiondesc.cpp
index 01f6ab867f..e7d03a6119 100644
--- a/src/qt/transactiondesc.cpp
+++ b/src/qt/transactiondesc.cpp
@@ -26,10 +26,10 @@ QString TransactionDesc::FormatTxStatus(const CWalletTx& wtx)
     AssertLockHeld(cs_main);
     if (!CheckFinalTx(wtx))
     {
-        if (wtx.nLockTime < LOCKTIME_THRESHOLD)
-            return tr("Open for %n more block(s)", "", wtx.nLockTime - chainActive.Height());
+        if (wtx.tx->nLockTime < LOCKTIME_THRESHOLD)
+            return tr("Open for %n more block(s)", "", wtx.tx->nLockTime - chainActive.Height());
         else
-            return tr("Open until %1").arg(GUIUtil::dateTimeStr(wtx.nLockTime));
+            return tr("Open until %1").arg(GUIUtil::dateTimeStr(wtx.tx->nLockTime));
     }
     else
     {
@@ -133,7 +133,7 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
         // Coinbase
         //
         CAmount nUnmatured = 0;
-        BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
             nUnmatured += wallet->GetCredit(txout, ISMINE_ALL);
         strHTML += "<b>" + tr("Credit") + ":</b> ";
         if (wtx.IsInMainChain())
@@ -152,14 +152,14 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
     else
     {
         isminetype fAllFromMe = ISMINE_SPENDABLE;
-        BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+        BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
         {
             isminetype mine = wallet->IsMine(txin);
             if(fAllFromMe > mine) fAllFromMe = mine;
         }
 
         isminetype fAllToMe = ISMINE_SPENDABLE;
-        BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
         {
             isminetype mine = wallet->IsMine(txout);
             if(fAllToMe > mine) fAllToMe = mine;
@@ -173,7 +173,7 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
             //
             // Debit
             //
-            BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+            BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
             {
                 // Ignore change
                 isminetype toSelf = wallet->IsMine(txout);
@@ -212,7 +212,7 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
                 strHTML += "<b>" + tr("Total credit") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, nValue) + "<br>";
             }
 
-            CAmount nTxFee = nDebit - wtx.GetValueOut();
+            CAmount nTxFee = nDebit - wtx.tx->GetValueOut();
             if (nTxFee > 0)
                 strHTML += "<b>" + tr("Transaction fee") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, -nTxFee) + "<br>";
         }
@@ -221,10 +221,10 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
             //
             // Mixed debit transaction
             //
-            BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+            BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
                 if (wallet->IsMine(txin))
                     strHTML += "<b>" + tr("Debit") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, -wallet->GetDebit(txin, ISMINE_ALL)) + "<br>";
-            BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+            BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
                 if (wallet->IsMine(txout))
                     strHTML += "<b>" + tr("Credit") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, wallet->GetCredit(txout, ISMINE_ALL)) + "<br>";
         }
@@ -241,7 +241,7 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
         strHTML += "<br><b>" + tr("Comment") + ":</b><br>" + GUIUtil::HtmlEscape(wtx.mapValue["comment"], true) + "<br>";
 
     strHTML += "<b>" + tr("Transaction ID") + ":</b> " + rec->getTxID() + "<br>";
-    strHTML += "<b>" + tr("Transaction total size") + ":</b> " + QString::number(wtx.GetTotalSize()) + " bytes<br>";
+    strHTML += "<b>" + tr("Transaction total size") + ":</b> " + QString::number(wtx.tx->GetTotalSize()) + " bytes<br>";
     strHTML += "<b>" + tr("Output index") + ":</b> " + QString::number(rec->getOutputIndex()) + "<br>";
 
     // Message from normal bitcoin:URI (bitcoin:123...?message=example)
@@ -276,20 +276,20 @@ QString TransactionDesc::toHTML(CWallet *wallet, CWalletTx &wtx, TransactionReco
     if (fDebug)
     {
         strHTML += "<hr><br>" + tr("Debug information") + "<br><br>";
-        BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+        BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
             if(wallet->IsMine(txin))
                 strHTML += "<b>" + tr("Debit") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, -wallet->GetDebit(txin, ISMINE_ALL)) + "<br>";
-        BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
             if(wallet->IsMine(txout))
                 strHTML += "<b>" + tr("Credit") + ":</b> " + BitcoinUnits::formatHtmlWithUnit(unit, wallet->GetCredit(txout, ISMINE_ALL)) + "<br>";
 
         strHTML += "<br><b>" + tr("Transaction") + ":</b><br>";
-        strHTML += GUIUtil::HtmlEscape(wtx.ToString(), true);
+        strHTML += GUIUtil::HtmlEscape(wtx.tx->ToString(), true);
 
         strHTML += "<br><b>" + tr("Inputs") + ":</b>";
         strHTML += "<ul>";
 
-        BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+        BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
         {
             COutPoint prevout = txin.prevout;
 
diff --git a/src/qt/transactionrecord.cpp b/src/qt/transactionrecord.cpp
index 7d7bce7be2..a1d1422317 100644
--- a/src/qt/transactionrecord.cpp
+++ b/src/qt/transactionrecord.cpp
@@ -47,7 +47,7 @@ QList<TransactionRecord> TransactionRecord::decomposeTransaction(const CWallet *
         //
         // Credit
         //
-        BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
         {
             isminetype mine = wallet->IsMine(txout);
             if(mine)
@@ -83,7 +83,7 @@ QList<TransactionRecord> TransactionRecord::decomposeTransaction(const CWallet *
     {
         bool involvesWatchAddress = false;
         isminetype fAllFromMe = ISMINE_SPENDABLE;
-        BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+        BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
         {
             isminetype mine = wallet->IsMine(txin);
             if(mine & ISMINE_WATCH_ONLY) involvesWatchAddress = true;
@@ -91,7 +91,7 @@ QList<TransactionRecord> TransactionRecord::decomposeTransaction(const CWallet *
         }
 
         isminetype fAllToMe = ISMINE_SPENDABLE;
-        BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
         {
             isminetype mine = wallet->IsMine(txout);
             if(mine & ISMINE_WATCH_ONLY) involvesWatchAddress = true;
@@ -112,11 +112,11 @@ QList<TransactionRecord> TransactionRecord::decomposeTransaction(const CWallet *
             //
             // Debit
             //
-            CAmount nTxFee = nDebit - wtx.GetValueOut();
+            CAmount nTxFee = nDebit - wtx.tx->GetValueOut();
 
-            for (unsigned int nOut = 0; nOut < wtx.vout.size(); nOut++)
+            for (unsigned int nOut = 0; nOut < wtx.tx->vout.size(); nOut++)
             {
-                const CTxOut& txout = wtx.vout[nOut];
+                const CTxOut& txout = wtx.tx->vout[nOut];
                 TransactionRecord sub(hash, nTime);
                 sub.idx = parts.size();
                 sub.involvesWatchAddress = involvesWatchAddress;
@@ -190,15 +190,15 @@ void TransactionRecord::updateStatus(const CWalletTx &wtx)
 
     if (!CheckFinalTx(wtx))
     {
-        if (wtx.nLockTime < LOCKTIME_THRESHOLD)
+        if (wtx.tx->nLockTime < LOCKTIME_THRESHOLD)
         {
             status.status = TransactionStatus::OpenUntilBlock;
-            status.open_for = wtx.nLockTime - chainActive.Height();
+            status.open_for = wtx.tx->nLockTime - chainActive.Height();
         }
         else
         {
             status.status = TransactionStatus::OpenUntilDate;
-            status.open_for = wtx.nLockTime;
+            status.open_for = wtx.tx->nLockTime;
         }
     }
     // For generated transactions, determine maturity
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index ab6c4b9274..a78fc90d2c 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -67,7 +67,7 @@ CAmount WalletModel::getBalance(const CCoinControl *coinControl) const
         wallet->AvailableCoins(vCoins, true, coinControl);
         BOOST_FOREACH(const COutput& out, vCoins)
             if(out.fSpendable)
-                nBalance += out.tx->vout[out.i].nValue;
+                nBalance += out.tx->tx->vout[out.i].nValue;
 
         return nBalance;
     }
@@ -609,7 +609,7 @@ void WalletModel::listCoins(std::map<QString, std::vector<COutput> >& mapCoins)
         int nDepth = wallet->mapWallet[outpoint.hash].GetDepthInMainChain();
         if (nDepth < 0) continue;
         COutput out(&wallet->mapWallet[outpoint.hash], outpoint.n, nDepth, true, true);
-        if (outpoint.n < out.tx->vout.size() && wallet->IsMine(out.tx->vout[outpoint.n]) == ISMINE_SPENDABLE)
+        if (outpoint.n < out.tx->tx->vout.size() && wallet->IsMine(out.tx->tx->vout[outpoint.n]) == ISMINE_SPENDABLE)
             vCoins.push_back(out);
     }
 
@@ -617,14 +617,14 @@ void WalletModel::listCoins(std::map<QString, std::vector<COutput> >& mapCoins)
     {
         COutput cout = out;
 
-        while (wallet->IsChange(cout.tx->vout[cout.i]) && cout.tx->vin.size() > 0 && wallet->IsMine(cout.tx->vin[0]))
+        while (wallet->IsChange(cout.tx->tx->vout[cout.i]) && cout.tx->tx->vin.size() > 0 && wallet->IsMine(cout.tx->tx->vin[0]))
         {
-            if (!wallet->mapWallet.count(cout.tx->vin[0].prevout.hash)) break;
-            cout = COutput(&wallet->mapWallet[cout.tx->vin[0].prevout.hash], cout.tx->vin[0].prevout.n, 0, true, true);
+            if (!wallet->mapWallet.count(cout.tx->tx->vin[0].prevout.hash)) break;
+            cout = COutput(&wallet->mapWallet[cout.tx->tx->vin[0].prevout.hash], cout.tx->tx->vin[0].prevout.n, 0, true, true);
         }
 
         CTxDestination address;
-        if(!out.fSpendable || !ExtractDestination(cout.tx->vout[cout.i].scriptPubKey, address))
+        if(!out.fSpendable || !ExtractDestination(cout.tx->tx->vout[cout.i].scriptPubKey, address))
             continue;
         mapCoins[QString::fromStdString(CBitcoinAddress(address).ToString())].push_back(out);
     }
diff --git a/src/qt/walletmodeltransaction.cpp b/src/qt/walletmodeltransaction.cpp
index fdec6a1c86..f9a95bed42 100644
--- a/src/qt/walletmodeltransaction.cpp
+++ b/src/qt/walletmodeltransaction.cpp
@@ -64,7 +64,7 @@ void WalletModelTransaction::reassignAmounts(int nChangePosRet)
                 if (out.amount() <= 0) continue;
                 if (i == nChangePosRet)
                     i++;
-                subtotal += walletTransaction->vout[i].nValue;
+                subtotal += walletTransaction->tx->vout[i].nValue;
                 i++;
             }
             rcp.amount = subtotal;
@@ -73,7 +73,7 @@ void WalletModelTransaction::reassignAmounts(int nChangePosRet)
         {
             if (i == nChangePosRet)
                 i++;
-            rcp.amount = walletTransaction->vout[i].nValue;
+            rcp.amount = walletTransaction->tx->vout[i].nValue;
             i++;
         }
     }
diff --git a/src/rest.cpp b/src/rest.cpp
index 7d7a7d3225..6379061f8f 100644
--- a/src/rest.cpp
+++ b/src/rest.cpp
@@ -363,7 +363,7 @@ static bool rest_tx(HTTPRequest* req, const std::string& strURIPart)
     if (!ParseHashStr(hashStr, hash))
         return RESTERR(req, HTTP_BAD_REQUEST, "Invalid hash: " + hashStr);
 
-    CTransaction tx;
+    CTransactionRef tx;
     uint256 hashBlock = uint256();
     if (!GetTransaction(hash, tx, Params().GetConsensus(), hashBlock, true))
         return RESTERR(req, HTTP_NOT_FOUND, hashStr + " not found");
@@ -388,7 +388,7 @@ static bool rest_tx(HTTPRequest* req, const std::string& strURIPart)
 
     case RF_JSON: {
         UniValue objTx(UniValue::VOBJ);
-        TxToJSON(tx, hashBlock, objTx);
+        TxToJSON(*tx, hashBlock, objTx);
         string strJSON = objTx.write() + "\n";
         req->WriteHeader("Content-Type", "application/json");
         req->WriteReply(HTTP_OK, strJSON);
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index ce16870d3c..48769a5335 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -218,19 +218,19 @@ UniValue getrawtransaction(const JSONRPCRequest& request)
         } 
     }
 
-    CTransaction tx;
+    CTransactionRef tx;
     uint256 hashBlock;
     if (!GetTransaction(hash, tx, Params().GetConsensus(), hashBlock, true))
         throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "No information available about transaction");
 
-    string strHex = EncodeHexTx(tx);
+    string strHex = EncodeHexTx(*tx);
 
     if (!fVerbose)
         return strHex;
 
     UniValue result(UniValue::VOBJ);
     result.push_back(Pair("hex", strHex));
-    TxToJSON(tx, hashBlock, result);
+    TxToJSON(*tx, hashBlock, result);
     return result;
 }
 
@@ -289,7 +289,7 @@ UniValue gettxoutproof(const JSONRPCRequest& request)
 
     if (pblockindex == NULL)
     {
-        CTransaction tx;
+        CTransactionRef tx;
         if (!GetTransaction(oneTxid, tx, Params().GetConsensus(), hashBlock, false) || hashBlock.IsNull())
             throw JSONRPCError(RPC_INVALID_ADDRESS_OR_KEY, "Transaction not yet in block");
         if (!mapBlockIndex.count(hashBlock))
@@ -520,13 +520,13 @@ UniValue decoderawtransaction(const JSONRPCRequest& request)
     LOCK(cs_main);
     RPCTypeCheck(request.params, boost::assign::list_of(UniValue::VSTR));
 
-    CTransaction tx;
+    CMutableTransaction mtx;
 
-    if (!DecodeHexTx(tx, request.params[0].get_str(), true))
+    if (!DecodeHexTx(mtx, request.params[0].get_str(), true))
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
 
     UniValue result(UniValue::VOBJ);
-    TxToJSON(tx, uint256(), result);
+    TxToJSON(CTransaction(std::move(mtx)), uint256(), result);
 
     return result;
 }
@@ -883,9 +883,10 @@ UniValue sendrawtransaction(const JSONRPCRequest& request)
     RPCTypeCheck(request.params, boost::assign::list_of(UniValue::VSTR)(UniValue::VBOOL));
 
     // parse hex string from parameter
-    CTransaction tx;
-    if (!DecodeHexTx(tx, request.params[0].get_str()))
+    CMutableTransaction mtx;
+    if (!DecodeHexTx(mtx, request.params[0].get_str()))
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
+    CTransaction tx(std::move(mtx));
     uint256 hashTx = tx.GetHash();
 
     bool fLimitFree = false;
diff --git a/src/script/bitcoinconsensus.cpp b/src/script/bitcoinconsensus.cpp
index 069ac55bfb..036d6ca7bf 100644
--- a/src/script/bitcoinconsensus.cpp
+++ b/src/script/bitcoinconsensus.cpp
@@ -85,8 +85,7 @@ static int verify_script(const unsigned char *scriptPubKey, unsigned int scriptP
     }
     try {
         TxInputStream stream(SER_NETWORK, PROTOCOL_VERSION, txTo, txToLen);
-        CTransaction tx;
-        stream >> tx;
+        CTransaction tx(deserialize, stream);
         if (nIn >= tx.vin.size())
             return set_error(err, bitcoinconsensus_ERR_TX_INDEX);
         if (GetSerializeSize(tx, SER_NETWORK, PROTOCOL_VERSION) != txToLen)
diff --git a/src/test/bloom_tests.cpp b/src/test/bloom_tests.cpp
index ffa1fb6ad0..b15ff9e44b 100644
--- a/src/test/bloom_tests.cpp
+++ b/src/test/bloom_tests.cpp
@@ -114,16 +114,14 @@ BOOST_AUTO_TEST_CASE(bloom_create_insert_key)
 BOOST_AUTO_TEST_CASE(bloom_match)
 {
     // Random real transaction (b4749f017444b051c44dfd2720e88f314ff94f3dd6d56d40ef65854fcd7fff6b)
-    CTransaction tx;
     CDataStream stream(ParseHex("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"), SER_DISK, CLIENT_VERSION);
-    stream >> tx;
+    CTransaction tx(deserialize, stream);
 
     // and one which spends it (e2769b09e784f32f62ef849763d4f45b98e07ba658647343b915ff832b110436)
     unsigned char ch[] = {0x01, 0x00, 0x00, 0x00, 0x01, 0x6b, 0xff, 0x7f, 0xcd, 0x4f, 0x85, 0x65, 0xef, 0x40, 0x6d, 0xd5, 0xd6, 0x3d, 0x4f, 0xf9, 0x4f, 0x31, 0x8f, 0xe8, 0x20, 0x27, 0xfd, 0x4d, 0xc4, 0x51, 0xb0, 0x44, 0x74, 0x01, 0x9f, 0x74, 0xb4, 0x00, 0x00, 0x00, 0x00, 0x8c, 0x49, 0x30, 0x46, 0x02, 0x21, 0x00, 0xda, 0x0d, 0xc6, 0xae, 0xce, 0xfe, 0x1e, 0x06, 0xef, 0xdf, 0x05, 0x77, 0x37, 0x57, 0xde, 0xb1, 0x68, 0x82, 0x09, 0x30, 0xe3, 0xb0, 0xd0, 0x3f, 0x46, 0xf5, 0xfc, 0xf1, 0x50, 0xbf, 0x99, 0x0c, 0x02, 0x21, 0x00, 0xd2, 0x5b, 0x5c, 0x87, 0x04, 0x00, 0x76, 0xe4, 0xf2, 0x53, 0xf8, 0x26, 0x2e, 0x76, 0x3e, 0x2d, 0xd5, 0x1e, 0x7f, 0xf0, 0xbe, 0x15, 0x77, 0x27, 0xc4, 0xbc, 0x42, 0x80, 0x7f, 0x17, 0xbd, 0x39, 0x01, 0x41, 0x04, 0xe6, 0xc2, 0x6e, 0xf6, 0x7d, 0xc6, 0x10, 0xd2, 0xcd, 0x19, 0x24, 0x84, 0x78, 0x9a, 0x6c, 0xf9, 0xae, 0xa9, 0x93, 0x0b, 0x94, 0x4b, 0x7e, 0x2d, 0xb5, 0x34, 0x2b, 0x9d, 0x9e, 0x5b, 0x9f, 0xf7, 0x9a, 0xff, 0x9a, 0x2e, 0xe1, 0x97, 0x8d, 0xd7, 0xfd, 0x01, 0xdf, 0xc5, 0x22, 0xee, 0x02, 0x28, 0x3d, 0x3b, 0x06, 0xa9, 0xd0, 0x3a, 0xcf, 0x80, 0x96, 0x96, 0x8d, 0x7d, 0xbb, 0x0f, 0x91, 0x78, 0xff, 0xff, 0xff, 0xff, 0x02, 0x8b, 0xa7, 0x94, 0x0e, 0x00, 0x00, 0x00, 0x00, 0x19, 0x76, 0xa9, 0x14, 0xba, 0xde, 0xec, 0xfd, 0xef, 0x05, 0x07, 0x24, 0x7f, 0xc8, 0xf7, 0x42, 0x41, 0xd7, 0x3b, 0xc0, 0x39, 0x97, 0x2d, 0x7b, 0x88, 0xac, 0x40, 0x94, 0xa8, 0x02, 0x00, 0x00, 0x00, 0x00, 0x19, 0x76, 0xa9, 0x14, 0xc1, 0x09, 0x32, 0x48, 0x3f, 0xec, 0x93, 0xed, 0x51, 0xf5, 0xfe, 0x95, 0xe7, 0x25, 0x59, 0xf2, 0xcc, 0x70, 0x43, 0xf9, 0x88, 0xac, 0x00, 0x00, 0x00, 0x00, 0x00};
     vector<unsigned char> vch(ch, ch + sizeof(ch) -1);
     CDataStream spendStream(vch, SER_DISK, CLIENT_VERSION);
-    CTransaction spendingTx;
-    spendStream >> spendingTx;
+    CTransaction spendingTx(deserialize, spendStream);
 
     CBloomFilter filter(10, 0.000001, 0, BLOOM_UPDATE_ALL);
     filter.insert(uint256S("0xb4749f017444b051c44dfd2720e88f314ff94f3dd6d56d40ef65854fcd7fff6b"));
diff --git a/src/test/script_tests.cpp b/src/test/script_tests.cpp
index 3169afb13a..eb324d5a6b 100644
--- a/src/test/script_tests.cpp
+++ b/src/test/script_tests.cpp
@@ -276,7 +276,7 @@ private:
     //! The Witness embedded script
     CScript witscript;
     CScriptWitness scriptWitness;
-    CTransaction creditTx;
+    CTransactionRef creditTx;
     CMutableTransaction spendTx;
     bool havePush;
     std::vector<unsigned char> push;
@@ -319,8 +319,8 @@ public:
             redeemscript = scriptPubKey;
             scriptPubKey = CScript() << OP_HASH160 << ToByteVector(CScriptID(redeemscript)) << OP_EQUAL;
         }
-        creditTx = BuildCreditingTransaction(scriptPubKey, nValue);
-        spendTx = BuildSpendingTransaction(CScript(), CScriptWitness(), creditTx);
+        creditTx = MakeTransactionRef(BuildCreditingTransaction(scriptPubKey, nValue));
+        spendTx = BuildSpendingTransaction(CScript(), CScriptWitness(), *creditTx);
     }
 
     TestBuilder& ScriptError(ScriptError_t err)
@@ -421,7 +421,7 @@ public:
     {
         TestBuilder copy = *this; // Make a copy so we can rollback the push.
         DoPush();
-        DoTest(creditTx.vout[0].scriptPubKey, spendTx.vin[0].scriptSig, scriptWitness, flags, comment, scriptError, nValue);
+        DoTest(creditTx->vout[0].scriptPubKey, spendTx.vin[0].scriptSig, scriptWitness, flags, comment, scriptError, nValue);
         *this = copy;
         return *this;
     }
@@ -447,7 +447,7 @@ public:
             array.push_back(wit);
         }
         array.push_back(FormatScript(spendTx.vin[0].scriptSig));
-        array.push_back(FormatScript(creditTx.vout[0].scriptPubKey));
+        array.push_back(FormatScript(creditTx->vout[0].scriptPubKey));
         array.push_back(FormatScriptFlags(flags));
         array.push_back(FormatScriptError((ScriptError_t)scriptError));
         array.push_back(comment);
@@ -461,7 +461,7 @@ public:
 
     const CScript& GetScriptPubKey()
     {
-        return creditTx.vout[0].scriptPubKey;
+        return creditTx->vout[0].scriptPubKey;
     }
 };
 
diff --git a/src/test/serialize_tests.cpp b/src/test/serialize_tests.cpp
index bbadf57957..1dc86eb116 100644
--- a/src/test/serialize_tests.cpp
+++ b/src/test/serialize_tests.cpp
@@ -21,10 +21,10 @@ protected:
     bool boolval;
     std::string stringval;
     const char* charstrval;
-    CTransaction txval;
+    CTransactionRef txval;
 public:
     CSerializeMethodsTestSingle() = default;
-    CSerializeMethodsTestSingle(int intvalin, bool boolvalin, std::string stringvalin, const char* charstrvalin, CTransaction txvalin) : intval(intvalin), boolval(boolvalin), stringval(std::move(stringvalin)), charstrval(charstrvalin), txval(txvalin){}
+    CSerializeMethodsTestSingle(int intvalin, bool boolvalin, std::string stringvalin, const char* charstrvalin, CTransaction txvalin) : intval(intvalin), boolval(boolvalin), stringval(std::move(stringvalin)), charstrval(charstrvalin), txval(MakeTransactionRef(txvalin)){}
     ADD_SERIALIZE_METHODS;
 
     template <typename Stream, typename Operation>
@@ -42,7 +42,7 @@ public:
                 boolval == rhs.boolval && \
                 stringval == rhs.stringval && \
                 strcmp(charstrval, rhs.charstrval) == 0 && \
-                txval == rhs.txval;
+                *txval == *rhs.txval;
     }
 };
 
diff --git a/src/test/sighash_tests.cpp b/src/test/sighash_tests.cpp
index 38d58e7ab0..a524f5b946 100644
--- a/src/test/sighash_tests.cpp
+++ b/src/test/sighash_tests.cpp
@@ -184,7 +184,7 @@ BOOST_AUTO_TEST_CASE(sighash_from_data)
         std::string raw_tx, raw_script, sigHashHex;
         int nIn, nHashType;
         uint256 sh;
-        CTransaction tx;
+        CTransactionRef tx;
         CScript scriptCode = CScript();
 
         try {
@@ -199,7 +199,7 @@ BOOST_AUTO_TEST_CASE(sighash_from_data)
           stream >> tx;
 
           CValidationState state;
-          BOOST_CHECK_MESSAGE(CheckTransaction(tx, state), strTest);
+          BOOST_CHECK_MESSAGE(CheckTransaction(*tx, state), strTest);
           BOOST_CHECK(state.IsValid());
 
           std::vector<unsigned char> raw = ParseHex(raw_script);
@@ -209,7 +209,7 @@ BOOST_AUTO_TEST_CASE(sighash_from_data)
           continue;
         }
 
-        sh = SignatureHash(scriptCode, tx, nIn, nHashType, 0, SIGVERSION_BASE);
+        sh = SignatureHash(scriptCode, *tx, nIn, nHashType, 0, SIGVERSION_BASE);
         BOOST_CHECK_MESSAGE(sh.GetHex() == sigHashHex, strTest);
     }
 }
diff --git a/src/test/transaction_tests.cpp b/src/test/transaction_tests.cpp
index 7b4763669a..ae5406ef7e 100644
--- a/src/test/transaction_tests.cpp
+++ b/src/test/transaction_tests.cpp
@@ -150,8 +150,7 @@ BOOST_AUTO_TEST_CASE(tx_valid)
 
             string transaction = test[1].get_str();
             CDataStream stream(ParseHex(transaction), SER_NETWORK, PROTOCOL_VERSION);
-            CTransaction tx;
-            stream >> tx;
+            CTransaction tx(deserialize, stream);
 
             CValidationState state;
             BOOST_CHECK_MESSAGE(CheckTransaction(tx, state), strTest);
@@ -236,8 +235,7 @@ BOOST_AUTO_TEST_CASE(tx_invalid)
 
             string transaction = test[1].get_str();
             CDataStream stream(ParseHex(transaction), SER_NETWORK, PROTOCOL_VERSION );
-            CTransaction tx;
-            stream >> tx;
+            CTransaction tx(deserialize, stream);
 
             CValidationState state;
             fValid = CheckTransaction(tx, state) && state.IsValid();
@@ -346,7 +344,7 @@ BOOST_AUTO_TEST_CASE(test_Get)
     BOOST_CHECK_EQUAL(coins.GetValueIn(t1), (50+21+22)*CENT);
 }
 
-void CreateCreditAndSpend(const CKeyStore& keystore, const CScript& outscript, CTransaction& output, CMutableTransaction& input, bool success = true)
+void CreateCreditAndSpend(const CKeyStore& keystore, const CScript& outscript, CTransactionRef& output, CMutableTransaction& input, bool success = true)
 {
     CMutableTransaction outputm;
     outputm.nVersion = 1;
@@ -360,22 +358,22 @@ void CreateCreditAndSpend(const CKeyStore& keystore, const CScript& outscript, C
     CDataStream ssout(SER_NETWORK, PROTOCOL_VERSION);
     ssout << outputm;
     ssout >> output;
-    assert(output.vin.size() == 1);
-    assert(output.vin[0] == outputm.vin[0]);
-    assert(output.vout.size() == 1);
-    assert(output.vout[0] == outputm.vout[0]);
-    assert(output.wit.vtxinwit.size() == 0);
+    assert(output->vin.size() == 1);
+    assert(output->vin[0] == outputm.vin[0]);
+    assert(output->vout.size() == 1);
+    assert(output->vout[0] == outputm.vout[0]);
+    assert(output->wit.vtxinwit.size() == 0);
 
     CMutableTransaction inputm;
     inputm.nVersion = 1;
     inputm.vin.resize(1);
-    inputm.vin[0].prevout.hash = output.GetHash();
+    inputm.vin[0].prevout.hash = output->GetHash();
     inputm.vin[0].prevout.n = 0;
     inputm.wit.vtxinwit.resize(1);
     inputm.vout.resize(1);
     inputm.vout[0].nValue = 1;
     inputm.vout[0].scriptPubKey = CScript();
-    bool ret = SignSignature(keystore, output, inputm, 0, SIGHASH_ALL);
+    bool ret = SignSignature(keystore, *output, inputm, 0, SIGHASH_ALL);
     assert(ret == success);
     CDataStream ssin(SER_NETWORK, PROTOCOL_VERSION);
     ssin << inputm;
@@ -393,11 +391,11 @@ void CreateCreditAndSpend(const CKeyStore& keystore, const CScript& outscript, C
     }
 }
 
-void CheckWithFlag(const CTransaction& output, const CMutableTransaction& input, int flags, bool success)
+void CheckWithFlag(const CTransactionRef& output, const CMutableTransaction& input, int flags, bool success)
 {
     ScriptError error;
     CTransaction inputi(input);
-    bool ret = VerifyScript(inputi.vin[0].scriptSig, output.vout[0].scriptPubKey, inputi.wit.vtxinwit.size() > 0 ? &inputi.wit.vtxinwit[0].scriptWitness : NULL, flags, TransactionSignatureChecker(&inputi, 0, output.vout[0].nValue), &error);
+    bool ret = VerifyScript(inputi.vin[0].scriptSig, output->vout[0].scriptPubKey, inputi.wit.vtxinwit.size() > 0 ? &inputi.wit.vtxinwit[0].scriptWitness : NULL, flags, TransactionSignatureChecker(&inputi, 0, output->vout[0].nValue), &error);
     assert(ret == success);
 }
 
@@ -466,10 +464,10 @@ BOOST_AUTO_TEST_CASE(test_big_witness_transaction) {
         assert(hashSigned);
     }
 
-    CTransaction tx;
     CDataStream ssout(SER_NETWORK, PROTOCOL_VERSION);
-    WithOrVersion(&ssout, 0) << mtx;
-    WithOrVersion(&ssout, 0) >> tx;
+    auto vstream = WithOrVersion(&ssout, 0);
+    vstream << mtx;
+    CTransaction tx(deserialize, vstream);
 
     // check all inputs concurrently, with the cache
     PrecomputedTransactionData txdata(tx);
@@ -547,7 +545,7 @@ BOOST_AUTO_TEST_CASE(test_witness)
     keystore2.AddCScript(GetScriptForWitness(scriptMulti));
     keystore2.AddKeyPubKey(key3, pubkey3);
 
-    CTransaction output1, output2;
+    CTransactionRef output1, output2;
     CMutableTransaction input1, input2;
     SignatureData sigdata;
 
@@ -639,8 +637,8 @@ BOOST_AUTO_TEST_CASE(test_witness)
     CheckWithFlag(output1, input1, 0, false);
     CreateCreditAndSpend(keystore2, scriptMulti, output2, input2, false);
     CheckWithFlag(output2, input2, 0, false);
-    BOOST_CHECK(output1 == output2);
-    UpdateTransaction(input1, 0, CombineSignatures(output1.vout[0].scriptPubKey, MutableTransactionSignatureChecker(&input1, 0, output1.vout[0].nValue), DataFromTransaction(input1, 0), DataFromTransaction(input2, 0)));
+    BOOST_CHECK(*output1 == *output2);
+    UpdateTransaction(input1, 0, CombineSignatures(output1->vout[0].scriptPubKey, MutableTransactionSignatureChecker(&input1, 0, output1->vout[0].nValue), DataFromTransaction(input1, 0), DataFromTransaction(input2, 0)));
     CheckWithFlag(output1, input1, STANDARD_SCRIPT_VERIFY_FLAGS, true);
 
     // P2SH 2-of-2 multisig
@@ -650,8 +648,8 @@ BOOST_AUTO_TEST_CASE(test_witness)
     CreateCreditAndSpend(keystore2, GetScriptForDestination(CScriptID(scriptMulti)), output2, input2, false);
     CheckWithFlag(output2, input2, 0, true);
     CheckWithFlag(output2, input2, SCRIPT_VERIFY_P2SH, false);
-    BOOST_CHECK(output1 == output2);
-    UpdateTransaction(input1, 0, CombineSignatures(output1.vout[0].scriptPubKey, MutableTransactionSignatureChecker(&input1, 0, output1.vout[0].nValue), DataFromTransaction(input1, 0), DataFromTransaction(input2, 0)));
+    BOOST_CHECK(*output1 == *output2);
+    UpdateTransaction(input1, 0, CombineSignatures(output1->vout[0].scriptPubKey, MutableTransactionSignatureChecker(&input1, 0, output1->vout[0].nValue), DataFromTransaction(input1, 0), DataFromTransaction(input2, 0)));
     CheckWithFlag(output1, input1, SCRIPT_VERIFY_P2SH, true);
     CheckWithFlag(output1, input1, STANDARD_SCRIPT_VERIFY_FLAGS, true);
 
@@ -662,8 +660,8 @@ BOOST_AUTO_TEST_CASE(test_witness)
     CreateCreditAndSpend(keystore2, GetScriptForWitness(scriptMulti), output2, input2, false);
     CheckWithFlag(output2, input2, 0, true);
     CheckWithFlag(output2, input2, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS, false);
-    BOOST_CHECK(output1 == output2);
-    UpdateTransaction(input1, 0, CombineSignatures(output1.vout[0].scriptPubKey, MutableTransactionSignatureChecker(&input1, 0, output1.vout[0].nValue), DataFromTransaction(input1, 0), DataFromTransaction(input2, 0)));
+    BOOST_CHECK(*output1 == *output2);
+    UpdateTransaction(input1, 0, CombineSignatures(output1->vout[0].scriptPubKey, MutableTransactionSignatureChecker(&input1, 0, output1->vout[0].nValue), DataFromTransaction(input1, 0), DataFromTransaction(input2, 0)));
     CheckWithFlag(output1, input1, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS, true);
     CheckWithFlag(output1, input1, STANDARD_SCRIPT_VERIFY_FLAGS, true);
 
@@ -674,8 +672,8 @@ BOOST_AUTO_TEST_CASE(test_witness)
     CreateCreditAndSpend(keystore2, GetScriptForDestination(CScriptID(GetScriptForWitness(scriptMulti))), output2, input2, false);
     CheckWithFlag(output2, input2, SCRIPT_VERIFY_P2SH, true);
     CheckWithFlag(output2, input2, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS, false);
-    BOOST_CHECK(output1 == output2);
-    UpdateTransaction(input1, 0, CombineSignatures(output1.vout[0].scriptPubKey, MutableTransactionSignatureChecker(&input1, 0, output1.vout[0].nValue), DataFromTransaction(input1, 0), DataFromTransaction(input2, 0)));
+    BOOST_CHECK(*output1 == *output2);
+    UpdateTransaction(input1, 0, CombineSignatures(output1->vout[0].scriptPubKey, MutableTransactionSignatureChecker(&input1, 0, output1->vout[0].nValue), DataFromTransaction(input1, 0), DataFromTransaction(input2, 0)));
     CheckWithFlag(output1, input1, SCRIPT_VERIFY_P2SH | SCRIPT_VERIFY_WITNESS, true);
     CheckWithFlag(output1, input1, STANDARD_SCRIPT_VERIFY_FLAGS, true);
 }
diff --git a/src/validation.cpp b/src/validation.cpp
index 9cfb5221a6..7eef14af2b 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -984,7 +984,7 @@ bool AcceptToMemoryPool(CTxMemPool& pool, CValidationState &state, const CTransa
 }
 
 /** Return transaction in txOut, and if it was found inside a block, its hash is placed in hashBlock */
-bool GetTransaction(const uint256 &hash, CTransaction &txOut, const Consensus::Params& consensusParams, uint256 &hashBlock, bool fAllowSlow)
+bool GetTransaction(const uint256 &hash, CTransactionRef &txOut, const Consensus::Params& consensusParams, uint256 &hashBlock, bool fAllowSlow)
 {
     CBlockIndex *pindexSlow = NULL;
 
@@ -993,7 +993,7 @@ bool GetTransaction(const uint256 &hash, CTransaction &txOut, const Consensus::P
     CTransactionRef ptx = mempool.get(hash);
     if (ptx)
     {
-        txOut = *ptx;
+        txOut = ptx;
         return true;
     }
 
@@ -1012,7 +1012,7 @@ bool GetTransaction(const uint256 &hash, CTransaction &txOut, const Consensus::P
                 return error("%s: Deserialize or I/O error - %s", __func__, e.what());
             }
             hashBlock = header.GetHash();
-            if (txOut.GetHash() != hash)
+            if (txOut->GetHash() != hash)
                 return error("%s: txid mismatch", __func__);
             return true;
         }
@@ -1035,7 +1035,7 @@ bool GetTransaction(const uint256 &hash, CTransaction &txOut, const Consensus::P
         if (ReadBlockFromDisk(block, pindexSlow, consensusParams)) {
             for (const auto& tx : block.vtx) {
                 if (tx->GetHash() == hash) {
-                    txOut = *tx;
+                    txOut = tx;
                     hashBlock = pindexSlow->GetBlockHash();
                     return true;
                 }
@@ -2859,8 +2859,9 @@ 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();
+            CMutableTransaction tx(*block.vtx[0]);
+            tx.vout.push_back(out);
+            block.vtx[0] = MakeTransactionRef(std::move(tx));
         }
     }
     UpdateUncommittedBlockStructures(block, pindexPrev, consensusParams);
@@ -4090,10 +4091,9 @@ bool LoadMempool(void)
         file >> num;
         double prioritydummy = 0;
         while (num--) {
-            CTransaction tx;
             int64_t nTime;
             int64_t nFeeDelta;
-            file >> tx;
+            CTransaction tx(deserialize, file);
             file >> nTime;
             file >> nFeeDelta;
 
diff --git a/src/validation.h b/src/validation.h
index a798cf3702..f242c20ab9 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -276,7 +276,7 @@ bool IsInitialBlockDownload();
  */
 std::string GetWarnings(const std::string& strFor);
 /** Retrieve a transaction (from memory pool, or from disk, if possible) */
-bool GetTransaction(const uint256 &hash, CTransaction &tx, const Consensus::Params& params, uint256 &hashBlock, bool fAllowSlow = false);
+bool GetTransaction(const uint256 &hash, CTransactionRef &tx, const Consensus::Params& params, uint256 &hashBlock, bool fAllowSlow = false);
 /** Find the best known block, and make it the tip of the block chain */
 bool ActivateBestChain(CValidationState& state, const CChainParams& chainparams, const CBlock* pblock = NULL);
 CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams);
diff --git a/src/wallet/rpcdump.cpp b/src/wallet/rpcdump.cpp
index 671b391c78..008a4ece19 100644
--- a/src/wallet/rpcdump.cpp
+++ b/src/wallet/rpcdump.cpp
@@ -267,11 +267,11 @@ UniValue importprunedfunds(const JSONRPCRequest& request)
             "2. \"txoutproof\"     (string, required) The hex output from gettxoutproof that contains the transaction\n"
         );
 
-    CTransaction tx;
+    CMutableTransaction tx;
     if (!DecodeHexTx(tx, request.params[0].get_str()))
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
     uint256 hashTx = tx.GetHash();
-    CWalletTx wtx(pwalletMain,tx);
+    CWalletTx wtx(pwalletMain, MakeTransactionRef(std::move(tx)));
 
     CDataStream ssMB(ParseHexV(request.params[1], "proof"), SER_NETWORK, PROTOCOL_VERSION);
     CMerkleBlock merkleBlock;
@@ -304,7 +304,7 @@ UniValue importprunedfunds(const JSONRPCRequest& request)
 
     LOCK2(cs_main, pwalletMain->cs_wallet);
 
-    if (pwalletMain->IsMine(tx)) {
+    if (pwalletMain->IsMine(wtx)) {
         pwalletMain->AddToWallet(wtx, false);
         return NullUniValue;
     }
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index d0c13c41d1..9e32b6751d 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -583,10 +583,10 @@ UniValue getreceivedbyaddress(const JSONRPCRequest& request)
     for (map<uint256, CWalletTx>::iterator it = pwalletMain->mapWallet.begin(); it != pwalletMain->mapWallet.end(); ++it)
     {
         const CWalletTx& wtx = (*it).second;
-        if (wtx.IsCoinBase() || !CheckFinalTx(wtx))
+        if (wtx.IsCoinBase() || !CheckFinalTx(*wtx.tx))
             continue;
 
-        BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
             if (txout.scriptPubKey == scriptPubKey)
                 if (wtx.GetDepthInMainChain() >= nMinDepth)
                     nAmount += txout.nValue;
@@ -637,10 +637,10 @@ UniValue getreceivedbyaccount(const JSONRPCRequest& request)
     for (map<uint256, CWalletTx>::iterator it = pwalletMain->mapWallet.begin(); it != pwalletMain->mapWallet.end(); ++it)
     {
         const CWalletTx& wtx = (*it).second;
-        if (wtx.IsCoinBase() || !CheckFinalTx(wtx))
+        if (wtx.IsCoinBase() || !CheckFinalTx(*wtx.tx))
             continue;
 
-        BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
         {
             CTxDestination address;
             if (ExtractDestination(txout.scriptPubKey, address) && IsMine(*pwalletMain, address) && setAddress.count(address))
@@ -1149,14 +1149,14 @@ UniValue ListReceived(const UniValue& params, bool fByAccounts)
     {
         const CWalletTx& wtx = (*it).second;
 
-        if (wtx.IsCoinBase() || !CheckFinalTx(wtx))
+        if (wtx.IsCoinBase() || !CheckFinalTx(*wtx.tx))
             continue;
 
         int nDepth = wtx.GetDepthInMainChain();
         if (nDepth < nMinDepth)
             continue;
 
-        BOOST_FOREACH(const CTxOut& txout, wtx.vout)
+        BOOST_FOREACH(const CTxOut& txout, wtx.tx->vout)
         {
             CTxDestination address;
             if (!ExtractDestination(txout.scriptPubKey, address))
@@ -1780,7 +1780,7 @@ UniValue gettransaction(const JSONRPCRequest& request)
     CAmount nCredit = wtx.GetCredit(filter);
     CAmount nDebit = wtx.GetDebit(filter);
     CAmount nNet = nCredit - nDebit;
-    CAmount nFee = (wtx.IsFromMe(filter) ? wtx.GetValueOut() - nDebit : 0);
+    CAmount nFee = (wtx.IsFromMe(filter) ? wtx.tx->GetValueOut() - nDebit : 0);
 
     entry.push_back(Pair("amount", ValueFromAmount(nNet - nFee)));
     if (wtx.IsFromMe(filter))
@@ -2420,7 +2420,7 @@ UniValue listunspent(const JSONRPCRequest& request)
             continue;
 
         CTxDestination address;
-        const CScript& scriptPubKey = out.tx->vout[out.i].scriptPubKey;
+        const CScript& scriptPubKey = out.tx->tx->vout[out.i].scriptPubKey;
         bool fValidAddress = ExtractDestination(scriptPubKey, address);
 
         if (setAddress.size() && (!fValidAddress || !setAddress.count(address)))
@@ -2445,7 +2445,7 @@ UniValue listunspent(const JSONRPCRequest& request)
         }
 
         entry.push_back(Pair("scriptPubKey", HexStr(scriptPubKey.begin(), scriptPubKey.end())));
-        entry.push_back(Pair("amount", ValueFromAmount(out.tx->vout[out.i].nValue)));
+        entry.push_back(Pair("amount", ValueFromAmount(out.tx->tx->vout[out.i].nValue)));
         entry.push_back(Pair("confirmations", out.nDepth));
         entry.push_back(Pair("spendable", out.fSpendable));
         entry.push_back(Pair("solvable", out.fSolvable));
@@ -2557,17 +2557,16 @@ UniValue fundrawtransaction(const JSONRPCRequest& request)
     }
 
     // parse hex string from parameter
-    CTransaction origTx;
-    if (!DecodeHexTx(origTx, request.params[0].get_str(), true))
+    CMutableTransaction tx;
+    if (!DecodeHexTx(tx, request.params[0].get_str(), true))
         throw JSONRPCError(RPC_DESERIALIZATION_ERROR, "TX decode failed");
 
-    if (origTx.vout.size() == 0)
+    if (tx.vout.size() == 0)
         throw JSONRPCError(RPC_INVALID_PARAMETER, "TX must have at least one output");
 
-    if (changePosition != -1 && (changePosition < 0 || (unsigned int)changePosition > origTx.vout.size()))
+    if (changePosition != -1 && (changePosition < 0 || (unsigned int)changePosition > tx.vout.size()))
         throw JSONRPCError(RPC_INVALID_PARAMETER, "changePosition out of bounds");
 
-    CMutableTransaction tx(origTx);
     CAmount nFeeOut;
     string strFailReason;
 
diff --git a/src/wallet/test/accounting_tests.cpp b/src/wallet/test/accounting_tests.cpp
index a833be13d0..eb14d176bd 100644
--- a/src/wallet/test/accounting_tests.cpp
+++ b/src/wallet/test/accounting_tests.cpp
@@ -86,7 +86,7 @@ BOOST_AUTO_TEST_CASE(acc_orderupgrade)
     {
         CMutableTransaction tx(wtx);
         --tx.nLockTime;  // Just to change the hash :)
-        *static_cast<CTransaction*>(&wtx) = CTransaction(tx);
+        wtx.SetTx(MakeTransactionRef(std::move(tx)));
     }
     pwalletMain->AddToWallet(wtx);
     vpwtx.push_back(&pwalletMain->mapWallet[wtx.GetHash()]);
@@ -96,7 +96,7 @@ BOOST_AUTO_TEST_CASE(acc_orderupgrade)
     {
         CMutableTransaction tx(wtx);
         --tx.nLockTime;  // Just to change the hash :)
-        *static_cast<CTransaction*>(&wtx) = CTransaction(tx);
+        wtx.SetTx(MakeTransactionRef(std::move(tx)));
     }
     pwalletMain->AddToWallet(wtx);
     vpwtx.push_back(&pwalletMain->mapWallet[wtx.GetHash()]);
diff --git a/src/wallet/test/wallet_tests.cpp b/src/wallet/test/wallet_tests.cpp
index ecbbcb145d..8085706a99 100644
--- a/src/wallet/test/wallet_tests.cpp
+++ b/src/wallet/test/wallet_tests.cpp
@@ -42,7 +42,7 @@ static void add_coin(const CAmount& nValue, int nAge = 6*24, bool fIsFromMe = fa
         // so stop vin being empty, and cache a non-zero Debit to fake out IsFromMe()
         tx.vin.resize(1);
     }
-    CWalletTx* wtx = new CWalletTx(&wallet, tx);
+    CWalletTx* wtx = new CWalletTx(&wallet, MakeTransactionRef(std::move(tx)));
     if (fIsFromMe)
     {
         wtx->fDebitCached = true;
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 102c191d6a..638fca9917 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -75,7 +75,7 @@ struct CompareValueOnly
 
 std::string COutput::ToString() const
 {
-    return strprintf("COutput(%s, %d, %d) [%s]", tx->GetHash().ToString(), i, nDepth, FormatMoney(tx->vout[i].nValue));
+    return strprintf("COutput(%s, %d, %d) [%s]", tx->GetHash().ToString(), i, nDepth, FormatMoney(tx->tx->vout[i].nValue));
 }
 
 const CWalletTx* CWallet::GetWalletTx(const uint256& hash) const
@@ -400,7 +400,7 @@ set<uint256> CWallet::GetConflicts(const uint256& txid) const
 
     std::pair<TxSpends::const_iterator, TxSpends::const_iterator> range;
 
-    BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+    BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
     {
         if (mapTxSpends.count(txin.prevout) <= 1)
             continue;  // No conflict if zero or one spends
@@ -552,7 +552,7 @@ void CWallet::AddToSpends(const uint256& wtxid)
     if (thisTx.IsCoinBase()) // Coinbases don't spend anything!
         return;
 
-    BOOST_FOREACH(const CTxIn& txin, thisTx.vin)
+    BOOST_FOREACH(const CTxIn& txin, thisTx.tx->vin)
         AddToSpends(txin.prevout, wtxid);
 }
 
@@ -795,7 +795,7 @@ bool CWallet::GetAccountPubkey(CPubKey &pubKey, std::string strAccount, bool bFo
             for (map<uint256, CWalletTx>::iterator it = mapWallet.begin();
                  it != mapWallet.end() && account.vchPubKey.IsValid();
                  ++it)
-                BOOST_FOREACH(const CTxOut& txout, (*it).second.vout)
+                BOOST_FOREACH(const CTxOut& txout, (*it).second.tx->vout)
                     if (txout.scriptPubKey == scriptPubKey) {
                         bForceNew = true;
                         break;
@@ -954,7 +954,7 @@ bool CWallet::LoadToWallet(const CWalletTx& wtxIn)
     wtx.BindWallet(this);
     wtxOrdered.insert(make_pair(wtx.nOrderPos, TxPair(&wtx, (CAccountingEntry*)0)));
     AddToSpends(hash);
-    BOOST_FOREACH(const CTxIn& txin, wtx.vin) {
+    BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin) {
         if (mapWallet.count(txin.prevout.hash)) {
             CWalletTx& prevtx = mapWallet[txin.prevout.hash];
             if (prevtx.nIndex == -1 && !prevtx.hashUnset()) {
@@ -993,7 +993,7 @@ bool CWallet::AddToWalletIfInvolvingMe(const CTransaction& tx, const CBlockIndex
         if (fExisted && !fUpdate) return false;
         if (fExisted || IsMine(tx) || IsFromMe(tx))
         {
-            CWalletTx wtx(this,tx);
+            CWalletTx wtx(this, MakeTransactionRef(tx));
 
             // Get merkle branch if transaction was found in a block
             if (posInBlock != -1)
@@ -1052,7 +1052,7 @@ bool CWallet::AbandonTransaction(const uint256& hashTx)
             }
             // If a transaction changes 'conflicted' state, that changes the balance
             // available of the outputs it spends. So force those to be recomputed
-            BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+            BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
             {
                 if (mapWallet.count(txin.prevout.hash))
                     mapWallet[txin.prevout.hash].MarkDirty();
@@ -1113,7 +1113,7 @@ void CWallet::MarkConflicted(const uint256& hashBlock, const uint256& hashTx)
             }
             // If a transaction changes 'conflicted' state, that changes the balance
             // available of the outputs it spends. So force those to be recomputed
-            BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+            BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
             {
                 if (mapWallet.count(txin.prevout.hash))
                     mapWallet[txin.prevout.hash].MarkDirty();
@@ -1148,8 +1148,8 @@ isminetype CWallet::IsMine(const CTxIn &txin) const
         if (mi != mapWallet.end())
         {
             const CWalletTx& prev = (*mi).second;
-            if (txin.prevout.n < prev.vout.size())
-                return IsMine(prev.vout[txin.prevout.n]);
+            if (txin.prevout.n < prev.tx->vout.size())
+                return IsMine(prev.tx->vout[txin.prevout.n]);
         }
     }
     return ISMINE_NO;
@@ -1163,9 +1163,9 @@ CAmount CWallet::GetDebit(const CTxIn &txin, const isminefilter& filter) const
         if (mi != mapWallet.end())
         {
             const CWalletTx& prev = (*mi).second;
-            if (txin.prevout.n < prev.vout.size())
-                if (IsMine(prev.vout[txin.prevout.n]) & filter)
-                    return prev.vout[txin.prevout.n].nValue;
+            if (txin.prevout.n < prev.tx->vout.size())
+                if (IsMine(prev.tx->vout[txin.prevout.n]) & filter)
+                    return prev.tx->vout[txin.prevout.n].nValue;
         }
     }
     return 0;
@@ -1380,14 +1380,14 @@ void CWalletTx::GetAmounts(list<COutputEntry>& listReceived,
     CAmount nDebit = GetDebit(filter);
     if (nDebit > 0) // debit>0 means we signed/sent this transaction
     {
-        CAmount nValueOut = GetValueOut();
+        CAmount nValueOut = tx->GetValueOut();
         nFee = nDebit - nValueOut;
     }
 
     // Sent/received.
-    for (unsigned int i = 0; i < vout.size(); ++i)
+    for (unsigned int i = 0; i < tx->vout.size(); ++i)
     {
-        const CTxOut& txout = vout[i];
+        const CTxOut& txout = tx->vout[i];
         isminetype fIsMine = pwallet->IsMine(txout);
         // Only need to handle txouts if AT LEAST one of these is true:
         //   1) they debit from us (sent)
@@ -1573,7 +1573,7 @@ set<uint256> CWalletTx::GetConflicts() const
 
 CAmount CWalletTx::GetDebit(const isminefilter& filter) const
 {
-    if (vin.empty())
+    if (tx->vin.empty())
         return 0;
 
     CAmount debit = 0;
@@ -1663,11 +1663,11 @@ CAmount CWalletTx::GetAvailableCredit(bool fUseCache) const
 
     CAmount nCredit = 0;
     uint256 hashTx = GetHash();
-    for (unsigned int i = 0; i < vout.size(); i++)
+    for (unsigned int i = 0; i < tx->vout.size(); i++)
     {
         if (!pwallet->IsSpent(hashTx, i))
         {
-            const CTxOut &txout = vout[i];
+            const CTxOut &txout = tx->vout[i];
             nCredit += pwallet->GetCredit(txout, ISMINE_SPENDABLE);
             if (!MoneyRange(nCredit))
                 throw std::runtime_error("CWalletTx::GetAvailableCredit() : value out of range");
@@ -1706,11 +1706,11 @@ CAmount CWalletTx::GetAvailableWatchOnlyCredit(const bool& fUseCache) const
         return nAvailableWatchCreditCached;
 
     CAmount nCredit = 0;
-    for (unsigned int i = 0; i < vout.size(); i++)
+    for (unsigned int i = 0; i < tx->vout.size(); i++)
     {
         if (!pwallet->IsSpent(GetHash(), i))
         {
-            const CTxOut &txout = vout[i];
+            const CTxOut &txout = tx->vout[i];
             nCredit += pwallet->GetCredit(txout, ISMINE_WATCH_ONLY);
             if (!MoneyRange(nCredit))
                 throw std::runtime_error("CWalletTx::GetAvailableCredit() : value out of range");
@@ -1758,23 +1758,23 @@ bool CWalletTx::IsTrusted() const
         return false;
 
     // Trusted if all inputs are from us and are in the mempool:
-    BOOST_FOREACH(const CTxIn& txin, vin)
+    BOOST_FOREACH(const CTxIn& txin, tx->vin)
     {
         // Transactions not sent by us: not trusted
         const CWalletTx* parent = pwallet->GetWalletTx(txin.prevout.hash);
         if (parent == NULL)
             return false;
-        const CTxOut& parentOut = parent->vout[txin.prevout.n];
+        const CTxOut& parentOut = parent->tx->vout[txin.prevout.n];
         if (pwallet->IsMine(parentOut) != ISMINE_SPENDABLE)
             return false;
     }
     return true;
 }
 
-bool CWalletTx::IsEquivalentTo(const CWalletTx& tx) const
+bool CWalletTx::IsEquivalentTo(const CWalletTx& _tx) const
 {
-        CMutableTransaction tx1 = *this;
-        CMutableTransaction tx2 = tx;
+        CMutableTransaction tx1 = *this->tx;
+        CMutableTransaction tx2 = *_tx.tx;
         for (unsigned int i = 0; i < tx1.vin.size(); i++) tx1.vin[i].scriptSig = CScript();
         for (unsigned int i = 0; i < tx2.vin.size(); i++) tx2.vin[i].scriptSig = CScript();
         return CTransaction(tx1) == CTransaction(tx2);
@@ -1957,10 +1957,10 @@ void CWallet::AvailableCoins(vector<COutput>& vCoins, bool fOnlyConfirmed, const
             if (nDepth == 0 && !pcoin->InMempool())
                 continue;
 
-            for (unsigned int i = 0; i < pcoin->vout.size(); i++) {
-                isminetype mine = IsMine(pcoin->vout[i]);
+            for (unsigned int i = 0; i < pcoin->tx->vout.size(); i++) {
+                isminetype mine = IsMine(pcoin->tx->vout[i]);
                 if (!(IsSpent(wtxid, i)) && mine != ISMINE_NO &&
-                    !IsLockedCoin((*it).first, i) && (pcoin->vout[i].nValue > 0 || fIncludeZeroValue) &&
+                    !IsLockedCoin((*it).first, i) && (pcoin->tx->vout[i].nValue > 0 || fIncludeZeroValue) &&
                     (!coinControl || !coinControl->HasSelected() || coinControl->fAllowOtherInputs || coinControl->IsSelected(COutPoint((*it).first, i))))
                         vCoins.push_back(COutput(pcoin, i, nDepth,
                                                  ((mine & ISMINE_SPENDABLE) != ISMINE_NO) ||
@@ -2043,7 +2043,7 @@ bool CWallet::SelectCoinsMinConf(const CAmount& nTargetValue, int nConfMine, int
             continue;
 
         int i = output.i;
-        CAmount n = pcoin->vout[i].nValue;
+        CAmount n = pcoin->tx->vout[i].nValue;
 
         pair<CAmount,pair<const CWalletTx*,unsigned int> > coin = make_pair(n,make_pair(pcoin, i));
 
@@ -2130,7 +2130,7 @@ bool CWallet::SelectCoins(const vector<COutput>& vAvailableCoins, const CAmount&
         {
             if (!out.fSpendable)
                  continue;
-            nValueRet += out.tx->vout[out.i].nValue;
+            nValueRet += out.tx->tx->vout[out.i].nValue;
             setCoinsRet.insert(make_pair(out.tx, out.i));
         }
         return (nValueRet >= nTargetValue);
@@ -2150,9 +2150,9 @@ bool CWallet::SelectCoins(const vector<COutput>& vAvailableCoins, const CAmount&
         {
             const CWalletTx* pcoin = &it->second;
             // Clearly invalid input, fail
-            if (pcoin->vout.size() <= outpoint.n)
+            if (pcoin->tx->vout.size() <= outpoint.n)
                 return false;
-            nValueFromPresetInputs += pcoin->vout[outpoint.n].nValue;
+            nValueFromPresetInputs += pcoin->tx->vout[outpoint.n].nValue;
             setPresetCoins.insert(make_pair(pcoin, outpoint.n));
         } else
             return false; // TODO: Allow non-wallet inputs
@@ -2208,10 +2208,10 @@ bool CWallet::FundTransaction(CMutableTransaction& tx, CAmount& nFeeRet, bool ov
         return false;
 
     if (nChangePosInOut != -1)
-        tx.vout.insert(tx.vout.begin() + nChangePosInOut, wtx.vout[nChangePosInOut]);
+        tx.vout.insert(tx.vout.begin() + nChangePosInOut, wtx.tx->vout[nChangePosInOut]);
 
     // Add new txins (keeping original txin scriptSig/order)
-    BOOST_FOREACH(const CTxIn& txin, wtx.vin)
+    BOOST_FOREACH(const CTxIn& txin, wtx.tx->vin)
     {
         if (!coinControl.IsSelected(txin.prevout))
         {
@@ -2351,7 +2351,7 @@ bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wt
                 }
                 BOOST_FOREACH(PAIRTYPE(const CWalletTx*, unsigned int) pcoin, setCoins)
                 {
-                    CAmount nCredit = pcoin.first->vout[pcoin.second].nValue;
+                    CAmount nCredit = pcoin.first->tx->vout[pcoin.second].nValue;
                     //The coin age after the next block (depth+1) is used instead of the current,
                     //reflecting an assumption the user would accept a bit more delay for
                     //a chance at a free transaction.
@@ -2466,10 +2466,10 @@ bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wt
                 BOOST_FOREACH(const PAIRTYPE(const CWalletTx*,unsigned int)& coin, setCoins)
                 {
                     bool signSuccess;
-                    const CScript& scriptPubKey = coin.first->vout[coin.second].scriptPubKey;
+                    const CScript& scriptPubKey = coin.first->tx->vout[coin.second].scriptPubKey;
                     SignatureData sigdata;
                     if (sign)
-                        signSuccess = ProduceSignature(TransactionSignatureCreator(this, &txNewConst, nIn, coin.first->vout[coin.second].nValue, SIGHASH_ALL), scriptPubKey, sigdata);
+                        signSuccess = ProduceSignature(TransactionSignatureCreator(this, &txNewConst, nIn, coin.first->tx->vout[coin.second].nValue, SIGHASH_ALL), scriptPubKey, sigdata);
                     else
                         signSuccess = ProduceSignature(DummySignatureCreator(this), scriptPubKey, sigdata);
 
@@ -2494,16 +2494,16 @@ bool CWallet::CreateTransaction(const vector<CRecipient>& vecSend, CWalletTx& wt
                 }
 
                 // Embed the constructed transaction data in wtxNew.
-                *static_cast<CTransaction*>(&wtxNew) = CTransaction(txNew);
+                wtxNew.SetTx(MakeTransactionRef(std::move(txNew)));
 
                 // Limit size
-                if (GetTransactionWeight(txNew) >= MAX_STANDARD_TX_WEIGHT)
+                if (GetTransactionWeight(wtxNew) >= MAX_STANDARD_TX_WEIGHT)
                 {
                     strFailReason = _("Transaction too large");
                     return false;
                 }
 
-                dPriority = wtxNew.ComputePriority(dPriority, nBytes);
+                dPriority = wtxNew.tx->ComputePriority(dPriority, nBytes);
 
                 // Allow to override the default confirmation target over the CoinControl instance
                 int currentConfirmationTarget = nTxConfirmTarget;
@@ -2555,7 +2555,7 @@ bool CWallet::CommitTransaction(CWalletTx& wtxNew, CReserveKey& reservekey, CCon
 {
     {
         LOCK2(cs_main, cs_wallet);
-        LogPrintf("CommitTransaction:\n%s", wtxNew.ToString());
+        LogPrintf("CommitTransaction:\n%s", wtxNew.tx->ToString());
         {
             // Take key pair from key pool so it won't be used again
             reservekey.KeepKey();
@@ -2565,7 +2565,7 @@ bool CWallet::CommitTransaction(CWalletTx& wtxNew, CReserveKey& reservekey, CCon
             AddToWallet(wtxNew);
 
             // Notify that old coins are spent
-            BOOST_FOREACH(const CTxIn& txin, wtxNew.vin)
+            BOOST_FOREACH(const CTxIn& txin, wtxNew.tx->vin)
             {
                 CWalletTx &coin = mapWallet[txin.prevout.hash];
                 coin.BindWallet(this);
@@ -2939,15 +2939,15 @@ std::map<CTxDestination, CAmount> CWallet::GetAddressBalances()
             if (nDepth < (pcoin->IsFromMe(ISMINE_ALL) ? 0 : 1))
                 continue;
 
-            for (unsigned int i = 0; i < pcoin->vout.size(); i++)
+            for (unsigned int i = 0; i < pcoin->tx->vout.size(); i++)
             {
                 CTxDestination addr;
-                if (!IsMine(pcoin->vout[i]))
+                if (!IsMine(pcoin->tx->vout[i]))
                     continue;
-                if(!ExtractDestination(pcoin->vout[i].scriptPubKey, addr))
+                if(!ExtractDestination(pcoin->tx->vout[i].scriptPubKey, addr))
                     continue;
 
-                CAmount n = IsSpent(walletEntry.first, i) ? 0 : pcoin->vout[i].nValue;
+                CAmount n = IsSpent(walletEntry.first, i) ? 0 : pcoin->tx->vout[i].nValue;
 
                 if (!balances.count(addr))
                     balances[addr] = 0;
@@ -2969,16 +2969,16 @@ set< set<CTxDestination> > CWallet::GetAddressGroupings()
     {
         CWalletTx *pcoin = &walletEntry.second;
 
-        if (pcoin->vin.size() > 0)
+        if (pcoin->tx->vin.size() > 0)
         {
             bool any_mine = false;
             // group all input addresses with each other
-            BOOST_FOREACH(CTxIn txin, pcoin->vin)
+            BOOST_FOREACH(CTxIn txin, pcoin->tx->vin)
             {
                 CTxDestination address;
                 if(!IsMine(txin)) /* If this input isn't mine, ignore it */
                     continue;
-                if(!ExtractDestination(mapWallet[txin.prevout.hash].vout[txin.prevout.n].scriptPubKey, address))
+                if(!ExtractDestination(mapWallet[txin.prevout.hash].tx->vout[txin.prevout.n].scriptPubKey, address))
                     continue;
                 grouping.insert(address);
                 any_mine = true;
@@ -2987,7 +2987,7 @@ set< set<CTxDestination> > CWallet::GetAddressGroupings()
             // group change with input addresses
             if (any_mine)
             {
-               BOOST_FOREACH(CTxOut txout, pcoin->vout)
+               BOOST_FOREACH(CTxOut txout, pcoin->tx->vout)
                    if (IsChange(txout))
                    {
                        CTxDestination txoutAddr;
@@ -3004,11 +3004,11 @@ set< set<CTxDestination> > CWallet::GetAddressGroupings()
         }
 
         // group lone addrs by themselves
-        for (unsigned int i = 0; i < pcoin->vout.size(); i++)
-            if (IsMine(pcoin->vout[i]))
+        for (unsigned int i = 0; i < pcoin->tx->vout.size(); i++)
+            if (IsMine(pcoin->tx->vout[i]))
             {
                 CTxDestination address;
-                if(!ExtractDestination(pcoin->vout[i].scriptPubKey, address))
+                if(!ExtractDestination(pcoin->tx->vout[i].scriptPubKey, address))
                     continue;
                 grouping.insert(address);
                 groupings.insert(grouping);
@@ -3275,7 +3275,7 @@ void CWallet::GetKeyBirthTimes(std::map<CKeyID, int64_t> &mapKeyBirth) const {
         if (blit != mapBlockIndex.end() && chainActive.Contains(blit->second)) {
             // ... which are already in a block
             int nHeight = blit->second->nHeight;
-            BOOST_FOREACH(const CTxOut &txout, wtx.vout) {
+            BOOST_FOREACH(const CTxOut &txout, wtx.tx->vout) {
                 // iterate over all their outputs
                 CAffectedKeysVisitor(*this, vAffected).Process(txout.scriptPubKey);
                 BOOST_FOREACH(const CKeyID &keyid, vAffected) {
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 409d817046..f7103b6a80 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -161,13 +161,14 @@ struct COutputEntry
 };
 
 /** A transaction with a merkle branch linking it to the block chain. */
-class CMerkleTx : public CTransaction
+class CMerkleTx
 {
 private:
   /** Constant used in hashBlock to indicate tx has been abandoned */
     static const uint256 ABANDON_HASH;
 
 public:
+    CTransactionRef tx;
     uint256 hashBlock;
 
     /* An nIndex == -1 means that hashBlock (in nonzero) refers to the earliest
@@ -179,26 +180,37 @@ public:
 
     CMerkleTx()
     {
+        SetTx(MakeTransactionRef());
         Init();
     }
 
-    CMerkleTx(const CTransaction& txIn) : CTransaction(txIn)
+    CMerkleTx(CTransactionRef arg)
     {
+        SetTx(std::move(arg));
         Init();
     }
 
+    /** Helper conversion operator to allow passing CMerkleTx where CTransaction is expected.
+     *  TODO: adapt callers and remove this operator. */
+    operator const CTransaction&() const { return *tx; }
+
     void Init()
     {
         hashBlock = uint256();
         nIndex = -1;
     }
 
+    void SetTx(CTransactionRef arg)
+    {
+        tx = std::move(arg);
+    }
+
     ADD_SERIALIZE_METHODS;
 
     template <typename Stream, typename Operation>
     inline void SerializationOp(Stream& s, Operation ser_action) {
         std::vector<uint256> vMerkleBranch; // For compatibility with older versions.
-        READWRITE(*(CTransaction*)this);
+        READWRITE(tx);
         READWRITE(hashBlock);
         READWRITE(vMerkleBranch);
         READWRITE(nIndex);
@@ -221,6 +233,9 @@ public:
     bool hashUnset() const { return (hashBlock.IsNull() || hashBlock == ABANDON_HASH); }
     bool isAbandoned() const { return (hashBlock == ABANDON_HASH); }
     void setAbandoned() { hashBlock = ABANDON_HASH; }
+
+    const uint256& GetHash() const { return tx->GetHash(); }
+    bool IsCoinBase() const { return tx->IsCoinBase(); }
 };
 
 /** 
@@ -267,17 +282,7 @@ public:
         Init(NULL);
     }
 
-    CWalletTx(const CWallet* pwalletIn)
-    {
-        Init(pwalletIn);
-    }
-
-    CWalletTx(const CWallet* pwalletIn, const CMerkleTx& txIn) : CMerkleTx(txIn)
-    {
-        Init(pwalletIn);
-    }
-
-    CWalletTx(const CWallet* pwalletIn, const CTransaction& txIn) : CMerkleTx(txIn)
+    CWalletTx(const CWallet* pwalletIn, CTransactionRef arg) : CMerkleTx(std::move(arg))
     {
         Init(pwalletIn);
     }