Always check return values of TxnBegin() and TxnCommit()

PARTIAL, since d68dcf7 isn't backported (yet)

src/main.cpp

@@ -1336,7 +1336,9 @@ bool CBlock::SetBestChain(CTxDB& txdb, CBlockIndex* pindexNew)
 {
     uint256 hash = GetHash();
 
-    txdb.TxnBegin();
+    if (!txdb.TxnBegin())
+        return error("SetBestChain() : TxnBegin failed");
+
     if (pindexGenesisBlock == NULL && hash == hashGenesisBlock)
     {
         txdb.WriteHashBestChain(hash);
@@ -1416,7 +1418,8 @@ bool CBlock::AddToBlockIndex(unsigned int nFile, unsigned int nBlockPos)
     pindexNew->bnChainWork = (pindexNew->pprev ? pindexNew->pprev->bnChainWork : 0) + pindexNew->GetBlockWork();
 
     CTxDB txdb;
-    txdb.TxnBegin();
+    if (!txdb.TxnBegin())
+        return false;
     txdb.WriteBlockIndex(CDiskBlockIndex(pindexNew));
     if (!txdb.TxnCommit())
         return false;

src/rpc.cpp

@@ -723,7 +723,8 @@ Value movecmd(const Array& params, bool fHelp)
         strComment = params[4].get_str();
 
     CWalletDB walletdb(pwalletMain->strWalletFile);
-    walletdb.TxnBegin();
+    if (!walletdb.TxnBegin())
+        throw JSONRPCError(-20, "database error");
 
     int64 nNow = GetAdjustedTime();
 
@@ -745,7 +746,8 @@ Value movecmd(const Array& params, bool fHelp)
     credit.strComment = strComment;
     walletdb.WriteAccountingEntry(credit);
 
-    walletdb.TxnCommit();
+    if (!walletdb.TxnCommit())
+        throw JSONRPCError(-20, "database error");
 
     return true;
 }

src/wallet.cpp

@@ -165,7 +165,8 @@ bool CWallet::EncryptWallet(const string& strWalletPassphrase)
         if (fFileBacked)
         {
             pwalletdbEncryption = new CWalletDB(strWalletFile);
-            pwalletdbEncryption->TxnBegin();
+            if (!pwalletdbEncryption->TxnBegin())
+                return false;
             pwalletdbEncryption->WriteMasterKey(nMasterKeyMaxID, kMasterKey);
         }