[wallet] Get rid of CWalletTx default constructor

No change in behavior in the normal case. But buggy mapWallet lookups with
invalid txids will now throw exceptions instead of inserting dummy entries into
the map, and potentially causing segfaults and other failures.

This also makes it a compiler error to use the mapWallet[hash] syntax which
could create dummy entries.

src/wallet/test/accounting_tests.cpp

@@ -29,7 +29,7 @@ GetResults(CWallet& wallet, std::map<CAmount, CAccountingEntry>& results)
 BOOST_AUTO_TEST_CASE(acc_orderupgrade)
 {
     std::vector<CWalletTx*> vpwtx;
-    CWalletTx wtx;
+    CWalletTx wtx(nullptr /* pwallet */, MakeTransactionRef());
     CAccountingEntry ae;
     std::map<CAmount, CAccountingEntry> results;
 
@@ -44,7 +44,7 @@ BOOST_AUTO_TEST_CASE(acc_orderupgrade)
 
     wtx.mapValue["comment"] = "z";
     m_wallet.AddToWallet(wtx);
-    vpwtx.push_back(&m_wallet.mapWallet[wtx.GetHash()]);
+    vpwtx.push_back(&m_wallet.mapWallet.at(wtx.GetHash()));
     vpwtx[0]->nTimeReceived = (unsigned int)1333333335;
     vpwtx[0]->nOrderPos = -1;
 
@@ -86,7 +86,7 @@ BOOST_AUTO_TEST_CASE(acc_orderupgrade)
         wtx.SetTx(MakeTransactionRef(std::move(tx)));
     }
     m_wallet.AddToWallet(wtx);
-    vpwtx.push_back(&m_wallet.mapWallet[wtx.GetHash()]);
+    vpwtx.push_back(&m_wallet.mapWallet.at(wtx.GetHash()));
     vpwtx[1]->nTimeReceived = (unsigned int)1333333336;
 
     wtx.mapValue["comment"] = "x";
@@ -96,7 +96,7 @@ BOOST_AUTO_TEST_CASE(acc_orderupgrade)
         wtx.SetTx(MakeTransactionRef(std::move(tx)));
     }
     m_wallet.AddToWallet(wtx);
-    vpwtx.push_back(&m_wallet.mapWallet[wtx.GetHash()]);
+    vpwtx.push_back(&m_wallet.mapWallet.at(wtx.GetHash()));
     vpwtx[2]->nTimeReceived = (unsigned int)1333333329;
     vpwtx[2]->nOrderPos = -1;
 

src/wallet/wallet.cpp

@@ -531,7 +531,7 @@ void CWallet::SyncMetaData(std::pair<TxSpends::iterator, TxSpends::iterator> ran
     int nMinOrderPos = std::numeric_limits<int>::max();
     const CWalletTx* copyFrom = nullptr;
     for (TxSpends::iterator it = range.first; it != range.second; ++it) {
-        const CWalletTx* wtx = &mapWallet[it->second];
+        const CWalletTx* wtx = &mapWallet.at(it->second);
         if (wtx->nOrderPos < nMinOrderPos) {
             nMinOrderPos = wtx->nOrderPos;;
             copyFrom = wtx;
@@ -544,7 +544,7 @@ void CWallet::SyncMetaData(std::pair<TxSpends::iterator, TxSpends::iterator> ran
     for (TxSpends::iterator it = range.first; it != range.second; ++it)
     {
         const uint256& hash = it->second;
-        CWalletTx* copyTo = &mapWallet[hash];
+        CWalletTx* copyTo = &mapWallet.at(hash);
         if (copyFrom == copyTo) continue;
         assert(copyFrom && "Oldest wallet transaction in range assumed to have been found.");
         if (!copyFrom->IsEquivalentTo(*copyTo)) continue;
@@ -3081,7 +3081,7 @@ bool CWallet::CommitTransaction(CTransactionRef tx, mapValue_t mapValue, std::ve
             // Notify that old coins are spent
             for (const CTxIn& txin : wtxNew.tx->vin)
             {
-                CWalletTx &coin = mapWallet[txin.prevout.hash];
+                CWalletTx &coin = mapWallet.at(txin.prevout.hash);
                 coin.BindWallet(this);
                 NotifyTransactionChanged(this, coin.GetHash(), CT_UPDATED);
             }
@@ -3092,7 +3092,7 @@ bool CWallet::CommitTransaction(CTransactionRef tx, mapValue_t mapValue, std::ve
 
         // Get the inserted-CWalletTx from mapWallet so that the
         // fInMempool flag is cached properly
-        CWalletTx& wtx = mapWallet[wtxNew.GetHash()];
+        CWalletTx& wtx = mapWallet.at(wtxNew.GetHash());
 
         if (fBroadcastTransactions)
         {
@@ -3548,7 +3548,7 @@ std::set< std::set<CTxDestination> > CWallet::GetAddressGroupings()
                 CTxDestination address;
                 if(!IsMine(txin)) /* If this input isn't mine, ignore it */
                     continue;
-                if(!ExtractDestination(mapWallet[txin.prevout.hash].tx->vout[txin.prevout.n].scriptPubKey, address))
+                if(!ExtractDestination(mapWallet.at(txin.prevout.hash).tx->vout[txin.prevout.n].scriptPubKey, address))
                     continue;
                 grouping.insert(address);
                 any_mine = true;

src/wallet/wallet.h

@@ -348,11 +348,6 @@ public:
     mutable CAmount nAvailableWatchCreditCached;
     mutable CAmount nChangeCached;
 
-    CWalletTx()
-    {
-        Init(nullptr);
-    }
-
     CWalletTx(const CWallet* pwalletIn, CTransactionRef arg) : CMerkleTx(std::move(arg))
     {
         Init(pwalletIn);

src/wallet/walletdb.cpp

@@ -265,7 +265,7 @@ ReadKeyValue(CWallet* pwallet, CDataStream& ssKey, CDataStream& ssValue,
         {
             uint256 hash;
             ssKey >> hash;
-            CWalletTx wtx;
+            CWalletTx wtx(nullptr /* pwallet */, MakeTransactionRef());
             ssValue >> wtx;
             CValidationState state;
             if (!(CheckTransaction(*wtx.tx, state) && (wtx.GetHash() == hash) && state.IsValid()))
@@ -603,7 +603,7 @@ DBErrors CWalletDB::LoadWallet(CWallet* pwallet)
         pwallet->UpdateTimeFirstKey(1);
 
     for (uint256 hash : wss.vWalletUpgrade)
-        WriteTx(pwallet->mapWallet[hash]);
+        WriteTx(pwallet->mapWallet.at(hash));
 
     // Rewrite encrypted wallets of versions 0.4.0 and 0.5.0rc:
     if (wss.fIsEncrypted && (wss.nFileVersion == 40000 || wss.nFileVersion == 50000))
@@ -664,7 +664,7 @@ DBErrors CWalletDB::FindWalletTx(std::vector<uint256>& vTxHash, std::vector<CWal
                 uint256 hash;
                 ssKey >> hash;
 
-                CWalletTx wtx;
+                CWalletTx wtx(nullptr /* pwallet */, MakeTransactionRef());
                 ssValue >> wtx;
 
                 vTxHash.push_back(hash);