Don't use pass by reference to const for cheaply-copied types (bool, char, etc.).

src/qt/sendcoinsdialog.cpp

@@ -171,7 +171,7 @@ void SendCoinsDialog::setModel(WalletModel *_model)
         coinControlUpdateLabels();
 
         // fee section
-        for (const int &n : confTargets) {
+        for (const int n : confTargets) {
             ui->confTargetSelector->addItem(tr("%1 (%2 blocks)").arg(GUIUtil::formatNiceTimeOffset(n*Params().GetConsensus().nPowTargetSpacing)).arg(n));
         }
         connect(ui->confTargetSelector, SIGNAL(currentIndexChanged(int)), this, SLOT(updateSmartFeeLabel()));

src/streams.h

@@ -241,8 +241,8 @@ public:
     const_reference operator[](size_type pos) const  { return vch[pos + nReadPos]; }
     reference operator[](size_type pos)              { return vch[pos + nReadPos]; }
     void clear()                                     { vch.clear(); nReadPos = 0; }
-    iterator insert(iterator it, const char& x=char()) { return vch.insert(it, x); }
+    iterator insert(iterator it, const char x=char()) { return vch.insert(it, x); }
-    void insert(iterator it, size_type n, const char& x) { vch.insert(it, n, x); }
+    void insert(iterator it, size_type n, const char x) { vch.insert(it, n, x); }
     value_type* data()                               { return vch.data() + nReadPos; }
     const value_type* data() const                   { return vch.data() + nReadPos; }
 

src/wallet/rpcdump.cpp

@@ -703,8 +703,8 @@ UniValue ProcessImport(CWallet * const pwallet, const UniValue& data, const int6
         const std::string& strRedeemScript = data.exists("redeemscript") ? data["redeemscript"].get_str() : "";
         const UniValue& pubKeys = data.exists("pubkeys") ? data["pubkeys"].get_array() : UniValue();
         const UniValue& keys = data.exists("keys") ? data["keys"].get_array() : UniValue();
-        const bool& internal = data.exists("internal") ? data["internal"].get_bool() : false;
+        const bool internal = data.exists("internal") ? data["internal"].get_bool() : false;
-        const bool& watchOnly = data.exists("watchonly") ? data["watchonly"].get_bool() : false;
+        const bool watchOnly = data.exists("watchonly") ? data["watchonly"].get_bool() : false;
         const std::string& label = data.exists("label") && !internal ? data["label"].get_str() : "";
 
         bool isScript = scriptPubKey.getType() == UniValue::VSTR;

src/wallet/wallet.cpp

@@ -1822,7 +1822,7 @@ CAmount CWalletTx::GetAvailableCredit(bool fUseCache) const
     return nCredit;
 }
 
-CAmount CWalletTx::GetImmatureWatchOnlyCredit(const bool& fUseCache) const
+CAmount CWalletTx::GetImmatureWatchOnlyCredit(const bool fUseCache) const
 {
     if (IsCoinBase() && GetBlocksToMaturity() > 0 && IsInMainChain())
     {
@@ -1836,7 +1836,7 @@ CAmount CWalletTx::GetImmatureWatchOnlyCredit(const bool& fUseCache) const
     return 0;
 }
 
-CAmount CWalletTx::GetAvailableWatchOnlyCredit(const bool& fUseCache) const
+CAmount CWalletTx::GetAvailableWatchOnlyCredit(const bool fUseCache) const
 {
     if (pwallet == 0)
         return 0;
@@ -2127,7 +2127,7 @@ CAmount CWallet::GetAvailableBalance(const CCoinControl* coinControl) const
     return balance;
 }
 
-void CWallet::AvailableCoins(std::vector<COutput> &vCoins, bool fOnlySafe, const CCoinControl *coinControl, const CAmount &nMinimumAmount, const CAmount &nMaximumAmount, const CAmount &nMinimumSumAmount, const uint64_t &nMaximumCount, const int &nMinDepth, const int &nMaxDepth) const
+void CWallet::AvailableCoins(std::vector<COutput> &vCoins, bool fOnlySafe, const CCoinControl *coinControl, const CAmount &nMinimumAmount, const CAmount &nMaximumAmount, const CAmount &nMinimumSumAmount, const uint64_t nMaximumCount, const int nMinDepth, const int nMaxDepth) const
 {
     vCoins.clear();
 

src/wallet/wallet.h

@@ -449,8 +449,8 @@ public:
     CAmount GetCredit(const isminefilter& filter) const;
     CAmount GetImmatureCredit(bool fUseCache=true) const;
     CAmount GetAvailableCredit(bool fUseCache=true) const;
-    CAmount GetImmatureWatchOnlyCredit(const bool& fUseCache=true) const;
+    CAmount GetImmatureWatchOnlyCredit(const bool fUseCache=true) const;
-    CAmount GetAvailableWatchOnlyCredit(const bool& fUseCache=true) const;
+    CAmount GetAvailableWatchOnlyCredit(const bool fUseCache=true) const;
     CAmount GetChange() const;
 
     void GetAmounts(std::list<COutputEntry>& listReceived,
@@ -819,7 +819,7 @@ public:
     /**
      * populate vCoins with vector of available COutputs.
      */
-    void AvailableCoins(std::vector<COutput>& vCoins, bool fOnlySafe=true, const CCoinControl *coinControl = nullptr, const CAmount& nMinimumAmount = 1, const CAmount& nMaximumAmount = MAX_MONEY, const CAmount& nMinimumSumAmount = MAX_MONEY, const uint64_t& nMaximumCount = 0, const int& nMinDepth = 0, const int& nMaxDepth = 9999999) const;
+    void AvailableCoins(std::vector<COutput>& vCoins, bool fOnlySafe=true, const CCoinControl *coinControl = nullptr, const CAmount& nMinimumAmount = 1, const CAmount& nMaximumAmount = MAX_MONEY, const CAmount& nMinimumSumAmount = MAX_MONEY, const uint64_t nMaximumCount = 0, const int nMinDepth = 0, const int nMaxDepth = 9999999) const;
 
     /**
      * Return list of available coins and locked coins grouped by non-change output address.