scripted-diff: Avoid temporary copies when looping over std::map

The ::value_type of the std::map/std::multimap/std::unordered_map containers is
std::pair<const Key, T>. Dropping the const results in an unnecessary copy,
for example in C++11 range-based loops.

For this I started with a more general scripted diff, then narrowed it down
based on the inspection showing that all actual map/multimap/unordered_map
variables used in loops start with m or have map in the name.

-BEGIN VERIFY SCRIPT-
sed -i -E 's/for \(([^<]*)std::pair<([^c])(.+) : m/for (\1std::pair<const \2\3 : m/' src/*.cpp src/**/*.cpp
sed -i -E 's/for \(([^<]*)std::pair<([^c])(.+) : (.*)map/for (\1std::pair<const \2\3 : \4map/' src/*.cpp src/**/*.cpp
-END VERIFY SCRIPT-

src/init.cpp

@@ -614,7 +614,7 @@ static void CleanupBlockRevFiles()
     // keeping a separate counter.  Once we hit a gap (or if 0 doesn't exist)
     // start removing block files.
     int nContigCounter = 0;
-    for (const std::pair<std::string, fs::path>& item : mapBlockFiles) {
+    for (const std::pair<const std::string, fs::path>& item : mapBlockFiles) {
         if (atoi(item.first) == nContigCounter) {
             nContigCounter++;
             continue;

src/rpc/net.cpp

@@ -475,7 +475,7 @@ static UniValue getnetworkinfo(const JSONRPCRequest& request)
     UniValue localAddresses(UniValue::VARR);
     {
         LOCK(cs_mapLocalHost);
-        for (const std::pair<CNetAddr, LocalServiceInfo> &item : mapLocalHost)
+        for (const std::pair<const CNetAddr, LocalServiceInfo> &item : mapLocalHost)
         {
             UniValue rec(UniValue::VOBJ);
             rec.pushKV("address", item.first.ToString());

src/validation.cpp

@@ -3840,7 +3840,7 @@ bool CChainState::LoadBlockIndex(const Consensus::Params& consensus_params, CBlo
     // Calculate nChainWork
     std::vector<std::pair<int, CBlockIndex*> > vSortedByHeight;
     vSortedByHeight.reserve(mapBlockIndex.size());
-    for (const std::pair<uint256, CBlockIndex*>& item : mapBlockIndex)
+    for (const std::pair<const uint256, CBlockIndex*>& item : mapBlockIndex)
     {
         CBlockIndex* pindex = item.second;
         vSortedByHeight.push_back(std::make_pair(pindex->nHeight, pindex));
@@ -3907,7 +3907,7 @@ bool static LoadBlockIndexDB(const CChainParams& chainparams)
     // Check presence of blk files
     LogPrintf("Checking all blk files are present...\n");
     std::set<int> setBlkDataFiles;
-    for (const std::pair<uint256, CBlockIndex*>& item : mapBlockIndex)
+    for (const std::pair<const uint256, CBlockIndex*>& item : mapBlockIndex)
     {
         CBlockIndex* pindex = item.second;
         if (pindex->nStatus & BLOCK_HAVE_DATA) {

src/wallet/rpcwallet.cpp

@@ -120,7 +120,7 @@ static void WalletTxToJSON(const CWalletTx& wtx, UniValue& entry)
     }
     entry.pushKV("bip125-replaceable", rbfStatus);
 
-    for (const std::pair<std::string, std::string>& item : wtx.mapValue)
+    for (const std::pair<const std::string, std::string>& item : wtx.mapValue)
         entry.pushKV(item.first, item.second);
 }
 
@@ -343,7 +343,7 @@ static UniValue setlabel(const JSONRPCRequest& request)
     // If so, delete the account record for it. Labels, unlike addresses, can be deleted,
     // and if we wouldn't do this, the record would stick around forever.
     bool found_address = false;
-    for (const std::pair<CTxDestination, CAddressBookData>& item : pwallet->mapAddressBook) {
+    for (const std::pair<const CTxDestination, CAddressBookData>& item : pwallet->mapAddressBook) {
         if (item.second.name == label) {
             found_address = true;
             break;
@@ -440,7 +440,7 @@ static UniValue getaddressesbyaccount(const JSONRPCRequest& request)
 
     // Find all addresses that have the given account
     UniValue ret(UniValue::VARR);
-    for (const std::pair<CTxDestination, CAddressBookData>& item : pwallet->mapAddressBook) {
+    for (const std::pair<const CTxDestination, CAddressBookData>& item : pwallet->mapAddressBook) {
         const CTxDestination& dest = item.first;
         const std::string& strName = item.second.name;
         if (strName == strAccount) {
@@ -753,7 +753,7 @@ static UniValue getreceivedbyaddress(const JSONRPCRequest& request)
 
     // Tally
     CAmount nAmount = 0;
-    for (const std::pair<uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
+    for (const std::pair<const uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
         const CWalletTx& wtx = pairWtx.second;
         if (wtx.IsCoinBase() || !CheckFinalTx(*wtx.tx))
             continue;
@@ -821,7 +821,7 @@ static UniValue getreceivedbylabel(const JSONRPCRequest& request)
 
     // Tally
     CAmount nAmount = 0;
-    for (const std::pair<uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
+    for (const std::pair<const uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
         const CWalletTx& wtx = pairWtx.second;
         if (wtx.IsCoinBase() || !CheckFinalTx(*wtx.tx))
             continue;
@@ -1534,7 +1534,7 @@ static UniValue ListReceived(CWallet * const pwallet, const UniValue& params, bo
 
     // Tally
     std::map<CTxDestination, tallyitem> mapTally;
-    for (const std::pair<uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
+    for (const std::pair<const uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
         const CWalletTx& wtx = pairWtx.second;
 
         if (wtx.IsCoinBase() || !CheckFinalTx(*wtx.tx))
@@ -2113,13 +2113,13 @@ static UniValue listaccounts(const JSONRPCRequest& request)
             includeWatchonly = includeWatchonly | ISMINE_WATCH_ONLY;
 
     std::map<std::string, CAmount> mapAccountBalances;
-    for (const std::pair<CTxDestination, CAddressBookData>& entry : pwallet->mapAddressBook) {
+    for (const std::pair<const CTxDestination, CAddressBookData>& entry : pwallet->mapAddressBook) {
         if (IsMine(*pwallet, entry.first) & includeWatchonly) {  // This address belongs to me
             mapAccountBalances[entry.second.name] = 0;
         }
     }
 
-    for (const std::pair<uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
+    for (const std::pair<const uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
         const CWalletTx& wtx = pairWtx.second;
         CAmount nFee;
         std::string strSentAccount;
@@ -2148,7 +2148,7 @@ static UniValue listaccounts(const JSONRPCRequest& request)
         mapAccountBalances[entry.strAccount] += entry.nCreditDebit;
 
     UniValue ret(UniValue::VOBJ);
-    for (const std::pair<std::string, CAmount>& accountBalance : mapAccountBalances) {
+    for (const std::pair<const std::string, CAmount>& accountBalance : mapAccountBalances) {
         ret.pushKV(accountBalance.first, ValueFromAmount(accountBalance.second));
     }
     return ret;
@@ -2257,7 +2257,7 @@ static UniValue listsinceblock(const JSONRPCRequest& request)
 
     UniValue transactions(UniValue::VARR);
 
-    for (const std::pair<uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
+    for (const std::pair<const uint256, CWalletTx>& pairWtx : pwallet->mapWallet) {
         CWalletTx tx = pairWtx.second;
 
         if (depth == -1 || tx.GetDepthInMainChain() < depth) {
@@ -4194,7 +4194,7 @@ static UniValue getaddressesbylabel(const JSONRPCRequest& request)
 
     // Find all addresses that have the given label
     UniValue ret(UniValue::VOBJ);
-    for (const std::pair<CTxDestination, CAddressBookData>& item : pwallet->mapAddressBook) {
+    for (const std::pair<const CTxDestination, CAddressBookData>& item : pwallet->mapAddressBook) {
         if (item.second.name == label) {
             ret.pushKV(EncodeDestination(item.first), AddressBookDataToJSON(item.second, false));
         }
@@ -4247,7 +4247,7 @@ static UniValue listlabels(const JSONRPCRequest& request)
 
     // Add to a set to sort by label name, then insert into Univalue array
     std::set<std::string> label_set;
-    for (const std::pair<CTxDestination, CAddressBookData>& entry : pwallet->mapAddressBook) {
+    for (const std::pair<const CTxDestination, CAddressBookData>& entry : pwallet->mapAddressBook) {
         if (purpose.empty() || entry.second.purpose == purpose) {
             label_set.insert(entry.second.name);
         }

src/wallet/wallet.cpp

@@ -3284,7 +3284,7 @@ bool CWallet::DelAddressBook(const CTxDestination& address)
 
         // Delete destdata tuples associated with address
         std::string strAddress = EncodeDestination(address);
-        for (const std::pair<std::string, std::string> &item : mapAddressBook[address].destdata)
+        for (const std::pair<const std::string, std::string> &item : mapAddressBook[address].destdata)
         {
             WalletBatch(*database).EraseDestData(strAddress, item.first);
         }
@@ -3685,7 +3685,7 @@ std::set<CTxDestination> CWallet::GetLabelAddresses(const std::string& label) co
 {
     LOCK(cs_wallet);
     std::set<CTxDestination> result;
-    for (const std::pair<CTxDestination, CAddressBookData>& item : mapAddressBook)
+    for (const std::pair<const CTxDestination, CAddressBookData>& item : mapAddressBook)
     {
         const CTxDestination& address = item.first;
         const std::string& strName = item.second.name;