diff --git a/src/cheat/CheatManager.cxx b/src/cheat/CheatManager.cxx
index 80bd13613..c01c133f6 100644
--- a/src/cheat/CheatManager.cxx
+++ b/src/cheat/CheatManager.cxx
@@ -147,8 +147,8 @@ shared_ptr<Cheat> CheatManager::createCheat(const string& name, const string& co
 void CheatManager::parse(const string& cheats)
 {
   StringList s;
-  string::size_type lastPos = cheats.find_first_not_of(",", 0);
-  string::size_type pos     = cheats.find_first_of(",", lastPos);
+  string::size_type lastPos = cheats.find_first_not_of(',', 0);
+  string::size_type pos     = cheats.find_first_of(',', lastPos);
   string cheat, name, code;
 
   // Split string by comma, getting each cheat
@@ -158,13 +158,13 @@ void CheatManager::parse(const string& cheats)
     cheat = cheats.substr(lastPos, pos - lastPos);
 
     // Split cheat by colon, separating each part
-    string::size_type lastColonPos = cheat.find_first_not_of(":", 0);
-    string::size_type colonPos     = cheat.find_first_of(":", lastColonPos);
+    string::size_type lastColonPos = cheat.find_first_not_of(':', 0);
+    string::size_type colonPos     = cheat.find_first_of(':', lastColonPos);
     while(string::npos != colonPos || string::npos != lastColonPos)
     {
       s.push_back(cheat.substr(lastColonPos, colonPos - lastColonPos));
-      lastColonPos = cheat.find_first_not_of(":", colonPos);
-      colonPos     = cheat.find_first_of(":", lastColonPos);
+      lastColonPos = cheat.find_first_not_of(':', colonPos);
+      colonPos     = cheat.find_first_of(':', lastColonPos);
     }
 
     // Account for variable number of items specified for cheat
@@ -190,8 +190,8 @@ void CheatManager::parse(const string& cheats)
     }
     s.clear();
 
-    lastPos = cheats.find_first_not_of(",", pos);
-    pos     = cheats.find_first_of(",", lastPos);
+    lastPos = cheats.find_first_not_of(',', pos);
+    pos     = cheats.find_first_of(',', lastPos);
   }
 }
 
@@ -228,10 +228,10 @@ void CheatManager::loadCheatDatabase()
     if(line.length() == 0)
       continue;
 
-    one = line.find("\"", 0);
-    two = line.find("\"", one + 1);
-    three = line.find("\"", two + 1);
-    four = line.find("\"", three + 1);
+    one = line.find('\"', 0);
+    two = line.find('\"', one + 1);
+    three = line.find('\"', two + 1);
+    four = line.find('\"', three + 1);
 
     // Invalid line if it doesn't contain 4 quotes
     if((one == string::npos) || (two == string::npos) ||
diff --git a/src/common/FSNodeZIP.cxx b/src/common/FSNodeZIP.cxx
index 72d8ab5c7..abab6ce0e 100644
--- a/src/common/FSNodeZIP.cxx
+++ b/src/common/FSNodeZIP.cxx
@@ -106,7 +106,7 @@ FilesystemNodeZIP::FilesystemNodeZIP(const string& p)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 FilesystemNodeZIP::FilesystemNodeZIP(
     const string& zipfile, const string& virtualpath,
-    AbstractFSNodePtr realnode, bool isdir)
+    const AbstractFSNodePtr& realnode, bool isdir)
   : _error(zip_error::NONE),
     _numFiles(0),
     _isDirectory(isdir),
@@ -118,7 +118,7 @@ FilesystemNodeZIP::FilesystemNodeZIP(
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void FilesystemNodeZIP::setFlags(const string& zipfile,
                                  const string& virtualpath,
-                                 AbstractFSNodePtr realnode)
+                                 const AbstractFSNodePtr& realnode)
 {
   _zipFile = zipfile;
   _virtualPath = virtualpath;
diff --git a/src/common/FSNodeZIP.hxx b/src/common/FSNodeZIP.hxx
index 70d1c0cd2..951f85a2d 100644
--- a/src/common/FSNodeZIP.hxx
+++ b/src/common/FSNodeZIP.hxx
@@ -71,10 +71,10 @@ class FilesystemNodeZIP : public AbstractFSNode
 
   private:
     FilesystemNodeZIP(const string& zipfile, const string& virtualpath,
-        AbstractFSNodePtr realnode, bool isdir);
+        const AbstractFSNodePtr& realnode, bool isdir);
 
     void setFlags(const string& zipfile, const string& virtualpath,
-        AbstractFSNodePtr realnode);
+        const AbstractFSNodePtr& realnode);
 
     friend ostream& operator<<(ostream& os, const FilesystemNodeZIP& node)
     {
diff --git a/src/common/PJoystickHandler.cxx b/src/common/PJoystickHandler.cxx
index 88e3eff6d..954294099 100644
--- a/src/common/PJoystickHandler.cxx
+++ b/src/common/PJoystickHandler.cxx
@@ -58,7 +58,7 @@ PhysicalJoystickHandler::PhysicalJoystickHandler(
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-int PhysicalJoystickHandler::add(PhysicalJoystickPtr stick)
+int PhysicalJoystickHandler::add(const PhysicalJoystickPtr& stick)
 {
   // Skip if we couldn't open it for any reason
   if(stick->ID < 0)
@@ -416,7 +416,7 @@ void PhysicalJoystickHandler::enableCommonMappings()
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void PhysicalJoystickHandler::enableMappings(const Event::EventSet events, EventMode mode)
+void PhysicalJoystickHandler::enableMappings(const Event::EventSet& events, EventMode mode)
 {
   for (const auto& event : events)
     enableMapping(event, mode);
diff --git a/src/common/PJoystickHandler.hxx b/src/common/PJoystickHandler.hxx
index a9f54a124..21cdaf464 100644
--- a/src/common/PJoystickHandler.hxx
+++ b/src/common/PJoystickHandler.hxx
@@ -49,7 +49,7 @@ class PhysicalJoystickHandler
     struct StickInfo
     {
       StickInfo(const string& map = EmptyString, PhysicalJoystickPtr stick = nullptr)
-        : mapping(map), joy(stick) {}
+        : mapping(map), joy(std::move(stick)) {}
 
       string mapping;
       PhysicalJoystickPtr joy;
@@ -64,7 +64,7 @@ class PhysicalJoystickHandler
     PhysicalJoystickHandler(OSystem& system, EventHandler& handler);
 
     /** Return stick ID on success, -1 on failure. */
-    int add(PhysicalJoystickPtr stick);
+    int add(const PhysicalJoystickPtr& stick);
     bool remove(int id);
     bool remove(const string& name);
     void mapStelladaptors(const string& saport);
@@ -161,7 +161,7 @@ class PhysicalJoystickHandler
 
     void enableCommonMappings();
 
-    void enableMappings(const Event::EventSet events, EventMode mode);
+    void enableMappings(const Event::EventSet& events, EventMode mode);
     void enableMapping(const Event::Type event, EventMode mode);
 
   private:
diff --git a/src/common/PKeyboardHandler.cxx b/src/common/PKeyboardHandler.cxx
index 5c53e7a7d..b5b2568cf 100644
--- a/src/common/PKeyboardHandler.cxx
+++ b/src/common/PKeyboardHandler.cxx
@@ -237,7 +237,7 @@ void PhysicalKeyboardHandler::enableCommonMappings()
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void PhysicalKeyboardHandler::enableMappings(const Event::EventSet events, EventMode mode)
+void PhysicalKeyboardHandler::enableMappings(const Event::EventSet& events, EventMode mode)
 {
   for (const auto& event : events)
     enableMapping(event, mode);
diff --git a/src/common/PKeyboardHandler.hxx b/src/common/PKeyboardHandler.hxx
index 8c9aab5f1..dbfd3158b 100644
--- a/src/common/PKeyboardHandler.hxx
+++ b/src/common/PKeyboardHandler.hxx
@@ -100,7 +100,7 @@ class PhysicalKeyboardHandler
 
     void enableCommonMappings();
 
-    void enableMappings(const Event::EventSet events, EventMode mode);
+    void enableMappings(const Event::EventSet& events, EventMode mode);
     void enableMapping(const Event::Type event, EventMode mode);
 
     OSystem& myOSystem;
diff --git a/src/common/TimerManager.cxx b/src/common/TimerManager.cxx
index a5e734a46..748f5b826 100644
--- a/src/common/TimerManager.cxx
+++ b/src/common/TimerManager.cxx
@@ -64,7 +64,7 @@ TimerManager::TimerId TimerManager::addTimer(
   // Assign an ID and insert it into function storage
   auto id = nextId++;
   auto iter = active.emplace(id, Timer(id, Clock::now() + Duration(msDelay),
-      Duration(msPeriod), std::move(func)));
+      Duration(msPeriod), func));
 
   // Insert a reference to the Timer into ordering queue
   Queue::iterator place = queue.emplace(iter.first->second);
@@ -240,11 +240,11 @@ TimerManager::Timer::Timer(TimerId tid)
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 TimerManager::Timer::Timer(Timer&& r) noexcept
-  : id(std::move(r.id)),
-    next(std::move(r.next)),
-    period(std::move(r.period)),
+  : id(r.id),
+    next(r.next),
+    period(r.period),
     handler(std::move(r.handler)),
-    running(std::move(r.running))
+    running(r.running)
 {
 }
 
@@ -254,7 +254,7 @@ TimerManager::Timer::Timer(TimerId tid, Timestamp tnext, Duration tperiod,
   : id(tid),
     next(tnext),
     period(tperiod),
-    handler(std::move(func)),
+    handler(func),
     running(false)
 {
 }
diff --git a/src/common/audio/LanczosResampler.cxx b/src/common/audio/LanczosResampler.cxx
index 02c760c51..91e8eb934 100644
--- a/src/common/audio/LanczosResampler.cxx
+++ b/src/common/audio/LanczosResampler.cxx
@@ -56,7 +56,7 @@ namespace {
 LanczosResampler::LanczosResampler(
   Resampler::Format formatFrom,
   Resampler::Format formatTo,
-  Resampler::NextFragmentCallback nextFragmentCallback,
+  const Resampler::NextFragmentCallback& nextFragmentCallback,
   uInt32 kernelParameter)
 :
   Resampler(formatFrom, formatTo, nextFragmentCallback),
diff --git a/src/common/audio/LanczosResampler.hxx b/src/common/audio/LanczosResampler.hxx
index 2570f0fc6..eeba17f2a 100644
--- a/src/common/audio/LanczosResampler.hxx
+++ b/src/common/audio/LanczosResampler.hxx
@@ -29,7 +29,7 @@ class LanczosResampler : public Resampler
     LanczosResampler(
       Resampler::Format formatFrom,
       Resampler::Format formatTo,
-      Resampler::NextFragmentCallback nextFragmentCallback,
+      const Resampler::NextFragmentCallback& nextFragmentCallback,
       uInt32 kernelParameter
     );
 
diff --git a/src/common/audio/Resampler.hxx b/src/common/audio/Resampler.hxx
index 2c8bd3fcf..f8a065b6e 100644
--- a/src/common/audio/Resampler.hxx
+++ b/src/common/audio/Resampler.hxx
@@ -50,7 +50,8 @@ class Resampler {
 
   public:
 
-    Resampler(Format formatFrom, Format formatTo, NextFragmentCallback nextFragmentCallback) :
+    Resampler(Format formatFrom, Format formatTo,
+              const NextFragmentCallback& nextFragmentCallback) :
       myFormatFrom(formatFrom),
       myFormatTo(formatTo),
       myNextFragmentCallback(nextFragmentCallback),
diff --git a/src/common/audio/SimpleResampler.cxx b/src/common/audio/SimpleResampler.cxx
index 48ba246e0..ecaec92d5 100644
--- a/src/common/audio/SimpleResampler.cxx
+++ b/src/common/audio/SimpleResampler.cxx
@@ -21,7 +21,7 @@
 SimpleResampler::SimpleResampler(
   Resampler::Format formatFrom,
   Resampler::Format formatTo,
-  Resampler::NextFragmentCallback nextFragmentCallback)
+  const Resampler::NextFragmentCallback& nextFragmentCallback)
   : Resampler(formatFrom, formatTo, nextFragmentCallback),
     myCurrentFragment(nullptr),
     myTimeIndex(0),
diff --git a/src/common/audio/SimpleResampler.hxx b/src/common/audio/SimpleResampler.hxx
index c847d20b4..e76be209f 100644
--- a/src/common/audio/SimpleResampler.hxx
+++ b/src/common/audio/SimpleResampler.hxx
@@ -27,7 +27,7 @@ class SimpleResampler : public Resampler
     SimpleResampler(
       Resampler::Format formatFrom,
       Resampler::Format formatTo,
-      Resampler::NextFragmentCallback NextFragmentCallback
+      const Resampler::NextFragmentCallback& NextFragmentCallback
     );
 
     void fillFragment(float* fragment, uInt32 length) override;
diff --git a/src/common/repository/KeyValueRepositoryConfigfile.cxx b/src/common/repository/KeyValueRepositoryConfigfile.cxx
index b492d94f1..459f3e58e 100644
--- a/src/common/repository/KeyValueRepositoryConfigfile.cxx
+++ b/src/common/repository/KeyValueRepositoryConfigfile.cxx
@@ -50,7 +50,7 @@ std::map<string, Variant> KeyValueRepositoryConfigfile::load()
   while(getline(in, line))
   {
     // Strip all whitespace and tabs from the line
-    while((garbage = line.find("\t")) != string::npos)
+    while((garbage = line.find('\t')) != string::npos)
       line.erase(garbage, 1);
 
     // Ignore commented and empty lines
@@ -58,7 +58,7 @@ std::map<string, Variant> KeyValueRepositoryConfigfile::load()
       continue;
 
     // Search for the equal sign and discard the line if its not found
-    if((equalPos = line.find("=")) == string::npos)
+    if((equalPos = line.find('=')) == string::npos)
       continue;
 
     // Split the line into key/value pairs and trim any whitespace
@@ -78,7 +78,7 @@ std::map<string, Variant> KeyValueRepositoryConfigfile::load()
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void KeyValueRepositoryConfigfile::save(const std::map<string, Variant>& values)
 {
-ofstream out(myFilename);
+  ofstream out(myFilename);
   if(!out || !out.is_open()) {
     Logger::error("ERROR: Couldn't save to settings file " + myFilename);
 
diff --git a/src/debugger/CartDebug.cxx b/src/debugger/CartDebug.cxx
index cd0286482..2d29b6488 100644
--- a/src/debugger/CartDebug.cxx
+++ b/src/debugger/CartDebug.cxx
@@ -214,7 +214,7 @@ string CartDebug::toString()
     curraddr = state.rport[i];
     buf << Base::HEX2 << (curraddr & 0x00ff) << ": ";
 
-    for(uInt8 j = 0; j < bytesPerLine; ++j)
+    for(uInt32 j = 0; j < bytesPerLine; ++j)
     {
       buf << myDebugger.invIfChanged(state.ram[i+j], oldstate.ram[i+j]) << " ";
 
@@ -794,12 +794,12 @@ string CartDebug::loadSymbolFile()
       if (iter == myUserLabels.end() || !BSPF::equalsIgnoreCase(label, iter->second))
       {
         // Check for period, and strip leading number
-        string::size_type pos = label.find_first_of(".", 0);
+        string::size_type pos = label.find_first_of('.', 0);
         if(pos != string::npos)
           addLabel(label.substr(pos), value);
         else
         {
-          pos = label.find_last_of("$");
+          pos = label.find_last_of('$');
           if (pos == string::npos || pos != label.length() - 1)
             addLabel(label, value);
         }
diff --git a/src/debugger/Debugger.cxx b/src/debugger/Debugger.cxx
index 26396a037..1645d6d42 100644
--- a/src/debugger/Debugger.cxx
+++ b/src/debugger/Debugger.cxx
@@ -661,7 +661,7 @@ void Debugger::saveOldState(bool clearDirtyPages)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void Debugger::addState(string rewindMsg)
+void Debugger::addState(const string& rewindMsg)
 {
   // Add another rewind level to the Time Machine buffer
   RewindManager& r = myOSystem.state().rewindManager();
diff --git a/src/debugger/Debugger.hxx b/src/debugger/Debugger.hxx
index 7eda40551..92d08d0b3 100644
--- a/src/debugger/Debugger.hxx
+++ b/src/debugger/Debugger.hxx
@@ -293,7 +293,7 @@ class Debugger : public DialogContainer
     /**
       Saves a rewind state with the given message.
     */
-    void addState(string rewindMsg);
+    void addState(const string& rewindMsg);
 
     /**
       Set initial state before entering the debugger.
diff --git a/src/debugger/gui/DelayQueueWidget.hxx b/src/debugger/gui/DelayQueueWidget.hxx
index a48c80fd7..47722eda6 100644
--- a/src/debugger/gui/DelayQueueWidget.hxx
+++ b/src/debugger/gui/DelayQueueWidget.hxx
@@ -44,8 +44,8 @@ class DelayQueueWidget : public Widget
     DelayQueueWidget() = delete;
     DelayQueueWidget(const DelayQueueWidget&) = delete;
     DelayQueueWidget(DelayQueueWidget&&) = delete;
-    DelayQueueWidget& operator=(const DelayQueueWidget&);
-    DelayQueueWidget& operator=(DelayQueueWidget&&);
+    DelayQueueWidget& operator=(const DelayQueueWidget&) = delete;
+    DelayQueueWidget& operator=(DelayQueueWidget&&) = delete;
 };
 
 #endif // DELAY_QUEUE_WIDGET_HXX
diff --git a/src/debugger/gui/PromptWidget.cxx b/src/debugger/gui/PromptWidget.cxx
index d9babbad0..4189c353a 100644
--- a/src/debugger/gui/PromptWidget.cxx
+++ b/src/debugger/gui/PromptWidget.cxx
@@ -810,6 +810,7 @@ void PromptWidget::updateScrollBuffer()
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
+// TODO: rewrite this (cert-dcl50-cpp)
 int PromptWidget::printf(const char* format, ...)
 {
   va_list argptr;
diff --git a/src/emucore/AtariVox.cxx b/src/emucore/AtariVox.cxx
index 9587bd54b..e877817bf 100644
--- a/src/emucore/AtariVox.cxx
+++ b/src/emucore/AtariVox.cxx
@@ -23,7 +23,7 @@
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 AtariVox::AtariVox(Jack jack, const Event& event, const System& system,
                    const string& portname, const string& eepromfile,
-                   onMessageCallback callback)
+                   const onMessageCallback& callback)
   : SaveKey(jack, event, system, eepromfile, callback, Controller::Type::AtariVox),
     myShiftCount(0),
     myShiftRegister(0),
diff --git a/src/emucore/AtariVox.hxx b/src/emucore/AtariVox.hxx
index 87e59440f..1dc4a840c 100644
--- a/src/emucore/AtariVox.hxx
+++ b/src/emucore/AtariVox.hxx
@@ -48,7 +48,7 @@ class AtariVox : public SaveKey
     */
     AtariVox(Jack jack, const Event& event, const System& system,
              const string& portname, const string& eepromfile,
-             onMessageCallback callback);
+             const onMessageCallback& callback);
     virtual ~AtariVox() = default;
 
   public:
diff --git a/src/emucore/Cart.hxx b/src/emucore/Cart.hxx
index f3afbe7a2..d9203449a 100644
--- a/src/emucore/Cart.hxx
+++ b/src/emucore/Cart.hxx
@@ -91,8 +91,8 @@ class Cartridge : public Device
       Set the function to use when we want to query the 'Cartridge.StartBank'
       ROM property.
     */
-    void setStartBankFromPropsFunc(StartBankFromPropsFunc func) {
-      myStartBankFromPropsFunc = std::move(func);
+    void setStartBankFromPropsFunc(const StartBankFromPropsFunc& func) {
+      myStartBankFromPropsFunc = func;
     }
 
     /**
diff --git a/src/emucore/CartBF.cxx b/src/emucore/CartBF.cxx
index 07334fe52..7ac9df7fc 100644
--- a/src/emucore/CartBF.cxx
+++ b/src/emucore/CartBF.cxx
@@ -94,7 +94,7 @@ bool CartridgeBF::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1000; addr < (0x1F80U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1000; addr < static_cast<uInt16>(0x1F80U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartBFSC.cxx b/src/emucore/CartBFSC.cxx
index 92332d436..010e9fcf0 100644
--- a/src/emucore/CartBFSC.cxx
+++ b/src/emucore/CartBFSC.cxx
@@ -133,7 +133,7 @@ bool CartridgeBFSC::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1100; addr < (0x1F80U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1100; addr < static_cast<uInt16>(0x1F80U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartDF.cxx b/src/emucore/CartDF.cxx
index 283ba62eb..5114cda5f 100644
--- a/src/emucore/CartDF.cxx
+++ b/src/emucore/CartDF.cxx
@@ -90,7 +90,7 @@ bool CartridgeDF::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1000; addr < (0x1FC0U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1000; addr < static_cast<uInt16>(0x1FC0U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartDFSC.cxx b/src/emucore/CartDFSC.cxx
index 18df1cbd0..8978aa6a7 100644
--- a/src/emucore/CartDFSC.cxx
+++ b/src/emucore/CartDFSC.cxx
@@ -133,7 +133,7 @@ bool CartridgeDFSC::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1100; addr < (0x1FC0U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1100; addr < static_cast<uInt16>(0x1FC0U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartDPC.cxx b/src/emucore/CartDPC.cxx
index 759f24324..dc266df23 100644
--- a/src/emucore/CartDPC.cxx
+++ b/src/emucore/CartDPC.cxx
@@ -394,7 +394,7 @@ bool CartridgeDPC::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1080; addr < (0x1FF8U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1080; addr < static_cast<uInt16>(0x1FF8U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myProgramImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartE0.cxx b/src/emucore/CartE0.cxx
index d9ea44902..2a39edbe9 100644
--- a/src/emucore/CartE0.cxx
+++ b/src/emucore/CartE0.cxx
@@ -57,7 +57,7 @@ void CartridgeE0::install(System& system)
   System::PageAccess access(this, System::PageAccessType::READ);
 
   // Set the page acessing methods for the first part of the last segment
-  for(uInt16 addr = 0x1C00; addr < (0x1FE0U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1C00; addr < static_cast<uInt16>(0x1FE0U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[0x1C00 + (addr & 0x03FF)];
diff --git a/src/emucore/CartEF.cxx b/src/emucore/CartEF.cxx
index b8807e430..521e754c1 100644
--- a/src/emucore/CartEF.cxx
+++ b/src/emucore/CartEF.cxx
@@ -90,7 +90,7 @@ bool CartridgeEF::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1000; addr < (0x1FE0U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1000; addr < static_cast<uInt16>(0x1FE0U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartEFSC.cxx b/src/emucore/CartEFSC.cxx
index c630c79f3..370beed68 100644
--- a/src/emucore/CartEFSC.cxx
+++ b/src/emucore/CartEFSC.cxx
@@ -133,7 +133,7 @@ bool CartridgeEFSC::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1100; addr < (0x1FE0U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1100; addr < static_cast<uInt16>(0x1FE0U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartF0.cxx b/src/emucore/CartF0.cxx
index 25e886652..3677fa131 100644
--- a/src/emucore/CartF0.cxx
+++ b/src/emucore/CartF0.cxx
@@ -97,7 +97,7 @@ bool CartridgeF0::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1000; addr < (0x1FF0U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1000; addr < static_cast<uInt16>(0x1FF0U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartF4.cxx b/src/emucore/CartF4.cxx
index 8e57359da..f24b19b91 100644
--- a/src/emucore/CartF4.cxx
+++ b/src/emucore/CartF4.cxx
@@ -94,7 +94,7 @@ bool CartridgeF4::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1000; addr < (0x1FF4U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1000; addr < static_cast<uInt16>(0x1FF4U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartF4SC.cxx b/src/emucore/CartF4SC.cxx
index 8d075302a..42265636c 100644
--- a/src/emucore/CartF4SC.cxx
+++ b/src/emucore/CartF4SC.cxx
@@ -133,7 +133,7 @@ bool CartridgeF4SC::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1100; addr < (0x1FF4U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1100; addr < static_cast<uInt16>(0x1FF4U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartF6.cxx b/src/emucore/CartF6.cxx
index 9ff62dda9..133f58a1d 100644
--- a/src/emucore/CartF6.cxx
+++ b/src/emucore/CartF6.cxx
@@ -134,7 +134,7 @@ bool CartridgeF6::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1000; addr < (0x1FF6U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1000; addr < static_cast<uInt16>(0x1FF6U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartF6SC.cxx b/src/emucore/CartF6SC.cxx
index f5d64517e..05832809c 100644
--- a/src/emucore/CartF6SC.cxx
+++ b/src/emucore/CartF6SC.cxx
@@ -173,7 +173,7 @@ bool CartridgeF6SC::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1100; addr < (0x1FF6U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1100; addr < static_cast<uInt16>(0x1FF6U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartF8.cxx b/src/emucore/CartF8.cxx
index 5b660e2e4..bfe4253c1 100644
--- a/src/emucore/CartF8.cxx
+++ b/src/emucore/CartF8.cxx
@@ -115,7 +115,7 @@ bool CartridgeF8::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1000; addr < (0x1FF8U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1000; addr < static_cast<uInt16>(0x1FF8U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartF8SC.cxx b/src/emucore/CartF8SC.cxx
index 60299169a..0d148ed65 100644
--- a/src/emucore/CartF8SC.cxx
+++ b/src/emucore/CartF8SC.cxx
@@ -153,7 +153,7 @@ bool CartridgeF8SC::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1100; addr < (0x1FF8U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1100; addr < static_cast<uInt16>(0x1FF8U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartFA.cxx b/src/emucore/CartFA.cxx
index f5a3c9230..e62fea198 100644
--- a/src/emucore/CartFA.cxx
+++ b/src/emucore/CartFA.cxx
@@ -163,7 +163,7 @@ bool CartridgeFA::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1200; addr < (0x1FF8U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1200; addr < static_cast<uInt16>(0x1FF8U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartFA2.cxx b/src/emucore/CartFA2.cxx
index 5b701a628..c901f7e75 100644
--- a/src/emucore/CartFA2.cxx
+++ b/src/emucore/CartFA2.cxx
@@ -230,7 +230,7 @@ bool CartridgeFA2::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for(uInt16 addr = 0x1200; addr < (0x1FF4U & ~System::PAGE_MASK);
+  for(uInt16 addr = 0x1200; addr < static_cast<uInt16>(0x1FF4U & ~System::PAGE_MASK);
       addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/CartFC.cxx b/src/emucore/CartFC.cxx
index 75082ff36..eb11f9813 100644
--- a/src/emucore/CartFC.cxx
+++ b/src/emucore/CartFC.cxx
@@ -126,7 +126,7 @@ bool CartridgeFC::bank(uInt16 bank)
   }
 
   // Setup the page access methods for the current bank
-  for (uInt16 addr = 0x1000; addr < (0x1FF8U & ~System::PAGE_MASK);
+  for (uInt16 addr = 0x1000; addr < static_cast<uInt16>(0x1FF8U & ~System::PAGE_MASK);
        addr += System::PAGE_SIZE)
   {
     access.directPeekBase = &myImage[myBankOffset + (addr & 0x0FFF)];
diff --git a/src/emucore/Control.hxx b/src/emucore/Control.hxx
index 1903a3ce2..8b26f8588 100644
--- a/src/emucore/Control.hxx
+++ b/src/emucore/Control.hxx
@@ -252,8 +252,8 @@ class Controller : public Serializable
     /**
       Inject a callback to be notified on analog pin updates.
     */
-    void setOnAnalogPinUpdateCallback(onAnalogPinUpdateCallback callback) {
-      myOnAnalogPinUpdateCallback = std::move(callback);
+    void setOnAnalogPinUpdateCallback(const onAnalogPinUpdateCallback& callback) {
+      myOnAnalogPinUpdateCallback = callback;
     }
 
     /**
diff --git a/src/emucore/EmulationWorker.cxx b/src/emucore/EmulationWorker.cxx
index 39721e209..9d55b8ba0 100644
--- a/src/emucore/EmulationWorker.cxx
+++ b/src/emucore/EmulationWorker.cxx
@@ -336,7 +336,7 @@ void EmulationWorker::waitUntilPendingSignalHasProcessed()
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void EmulationWorker::fatal(string message)
+void EmulationWorker::fatal(const string& message)
 {
   (cerr << "FATAL in emulation worker: " << message << std::endl).flush();
   throw runtime_error(message);
diff --git a/src/emucore/EmulationWorker.hxx b/src/emucore/EmulationWorker.hxx
index b5315fbbb..ba116d88e 100644
--- a/src/emucore/EmulationWorker.hxx
+++ b/src/emucore/EmulationWorker.hxx
@@ -128,7 +128,7 @@ class EmulationWorker
     /**
       Log a fatal error to cerr and throw a runtime exception.
      */
-    [[noreturn]] void fatal(string message);
+    [[noreturn]] void fatal(const string& message);
 
   private:
   /**
diff --git a/src/emucore/EventHandler.cxx b/src/emucore/EventHandler.cxx
index 760e005c7..e2f817f33 100644
--- a/src/emucore/EventHandler.cxx
+++ b/src/emucore/EventHandler.cxx
@@ -147,7 +147,7 @@ void EventHandler::reset(EventHandlerState state)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void EventHandler::addPhysicalJoystick(PhysicalJoystickPtr joy)
+void EventHandler::addPhysicalJoystick(const PhysicalJoystickPtr& joy)
 {
 #ifdef JOYSTICK_SUPPORT
   int ID = myPJoyHandler->add(joy);
diff --git a/src/emucore/EventHandler.hxx b/src/emucore/EventHandler.hxx
index 0e7586dff..a33d08ba3 100644
--- a/src/emucore/EventHandler.hxx
+++ b/src/emucore/EventHandler.hxx
@@ -380,7 +380,7 @@ class EventHandler
     /**
       Add the given joystick to the list of physical joysticks available to the handler.
     */
-    void addPhysicalJoystick(PhysicalJoystickPtr stick);
+    void addPhysicalJoystick(const PhysicalJoystickPtr& stick);
 
     /**
       Remove physical joystick at the current index.
diff --git a/src/emucore/FSNode.cxx b/src/emucore/FSNode.cxx
index e12dc51f8..64ca0845b 100644
--- a/src/emucore/FSNode.cxx
+++ b/src/emucore/FSNode.cxx
@@ -28,7 +28,7 @@ FilesystemNode::FilesystemNode()
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 FilesystemNode::FilesystemNode(AbstractFSNodePtr realNode)
-  : _realNode(realNode)
+  : _realNode(std::move(realNode))
 {
 }
 
@@ -145,7 +145,7 @@ string FilesystemNode::getNameWithExt(const string& ext) const
   string s = pos == string::npos ? _realNode->getName() :
         _realNode->getName().substr(pos+1);
 
-  pos = s.find_last_of(".");
+  pos = s.find_last_of('.');
   return (pos != string::npos) ? s.replace(pos, string::npos, ext) : s + ext;
 }
 
@@ -157,7 +157,7 @@ string FilesystemNode::getPathWithExt(const string& ext) const
 
   string s = _realNode->getPath();
 
-  size_t pos = s.find_last_of(".");
+  size_t pos = s.find_last_of('.');
   return (pos != string::npos) ? s.replace(pos, string::npos, ext) : s + ext;
 }
 
diff --git a/src/emucore/M6502.hxx b/src/emucore/M6502.hxx
index 10df4a13a..06472adcc 100644
--- a/src/emucore/M6502.hxx
+++ b/src/emucore/M6502.hxx
@@ -94,7 +94,9 @@ class M6502 : public Serializable
     /**
       Set the callback for handling a halt condition
     */
-    void setOnHaltCallback(onHaltCallback callback) { myOnHaltCallback = callback; }
+    void setOnHaltCallback(const onHaltCallback& callback) {
+      myOnHaltCallback = callback;
+    }
 
     /**
       RDY pulled low --- halt on next read.
diff --git a/src/emucore/MT24LC256.cxx b/src/emucore/MT24LC256.cxx
index ce1ca257f..4c9cef8b9 100644
--- a/src/emucore/MT24LC256.cxx
+++ b/src/emucore/MT24LC256.cxx
@@ -44,7 +44,7 @@
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 MT24LC256::MT24LC256(const string& filename, const System& system,
-                     Controller::onMessageCallback callback)
+                     const Controller::onMessageCallback& callback)
   : mySystem(system),
     myCallback(callback),
     mySDA(false),
diff --git a/src/emucore/MT24LC256.hxx b/src/emucore/MT24LC256.hxx
index 5f7e6c3a4..1fb659632 100644
--- a/src/emucore/MT24LC256.hxx
+++ b/src/emucore/MT24LC256.hxx
@@ -41,7 +41,7 @@ class MT24LC256
       @param callback  Called to pass messages back to the parent controller
     */
     MT24LC256(const string& filename, const System& system,
-              Controller::onMessageCallback callback);
+              const Controller::onMessageCallback& callback);
     ~MT24LC256();
 
   public:
@@ -89,7 +89,7 @@ class MT24LC256
 
     // Sends messages back to the parent class
     // Currently used for indicating read/write access
-    Controller::onMessageCallback myCallback;
+    const Controller::onMessageCallback myCallback;
 
     // The EEPROM data
     std::array<uInt8, FLASH_SIZE> myData;
diff --git a/src/emucore/ProfilingRunner.cxx b/src/emucore/ProfilingRunner.cxx
index 9935872a6..f2bd97c0c 100644
--- a/src/emucore/ProfilingRunner.cxx
+++ b/src/emucore/ProfilingRunner.cxx
@@ -63,7 +63,7 @@ ProfilingRunner::ProfilingRunner(int argc, char* argv[])
     ProfilingRun& run(profilingRuns[i-2]);
 
     string arg = argv[i];
-    size_t splitPoint = arg.find_first_of(":");
+    size_t splitPoint = arg.find_first_of(':');
 
     run.romFile = splitPoint == string::npos ? arg : arg.substr(0, splitPoint);
 
@@ -92,7 +92,7 @@ bool ProfilingRunner::run()
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-bool ProfilingRunner::runOne(const ProfilingRun run)
+bool ProfilingRunner::runOne(const ProfilingRun& run)
 {
   FilesystemNode imageFile(run.romFile);
 
diff --git a/src/emucore/ProfilingRunner.hxx b/src/emucore/ProfilingRunner.hxx
index 6c63de49a..48dbe9e08 100644
--- a/src/emucore/ProfilingRunner.hxx
+++ b/src/emucore/ProfilingRunner.hxx
@@ -52,7 +52,7 @@ class ProfilingRunner {
 
   private:
 
-    bool runOne(const ProfilingRun run);
+    bool runOne(const ProfilingRun& run);
 
   private:
 
diff --git a/src/emucore/SaveKey.cxx b/src/emucore/SaveKey.cxx
index 45734fff7..b9546b5cc 100644
--- a/src/emucore/SaveKey.cxx
+++ b/src/emucore/SaveKey.cxx
@@ -22,7 +22,8 @@
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 SaveKey::SaveKey(Jack jack, const Event& event, const System& system,
-                 const string& eepromfile, onMessageCallback callback, Type type)
+                 const string& eepromfile, const onMessageCallback& callback,
+                 Type type)
   : Controller(jack, event, system, type)
 {
   myEEPROM = make_unique<MT24LC256>(eepromfile, system, callback);
@@ -33,7 +34,7 @@ SaveKey::SaveKey(Jack jack, const Event& event, const System& system,
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 SaveKey::SaveKey(Jack jack, const Event& event, const System& system,
-                 const string& eepromfile, onMessageCallback callback)
+                 const string& eepromfile, const onMessageCallback& callback)
   : SaveKey(jack, event, system, eepromfile, callback, Controller::Type::SaveKey)
 {
 }
diff --git a/src/emucore/SaveKey.hxx b/src/emucore/SaveKey.hxx
index cb483b18a..89fa6c8a5 100644
--- a/src/emucore/SaveKey.hxx
+++ b/src/emucore/SaveKey.hxx
@@ -45,7 +45,7 @@ class SaveKey : public Controller
       @param callback   Called to pass messages back to the parent controller
     */
     SaveKey(Jack jack, const Event& event, const System& system,
-            const string& eepromfile, onMessageCallback callback);
+            const string& eepromfile, const onMessageCallback& callback);
     virtual ~SaveKey();
 
   protected:
@@ -54,7 +54,7 @@ class SaveKey : public Controller
       that inherit from SaveKey (currently, AtariVox)
     */
     SaveKey(Jack jack, const Event& event, const System& system,
-            const string& eepromfile, onMessageCallback callback, Type type);
+            const string& eepromfile, const onMessageCallback& callback, Type type);
 
   public:
     using Controller::read;
diff --git a/src/emucore/Settings.cxx b/src/emucore/Settings.cxx
index c53654584..4d1287bd8 100644
--- a/src/emucore/Settings.cxx
+++ b/src/emucore/Settings.cxx
@@ -218,7 +218,7 @@ Settings::Settings()
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void Settings::setRepository(shared_ptr<KeyValueRepository> repository)
 {
-  myRespository = repository;
+  myRespository = std::move(repository);
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/emucore/tia/Audio.cxx b/src/emucore/tia/Audio.cxx
index ca8943522..84b53295b 100644
--- a/src/emucore/tia/Audio.cxx
+++ b/src/emucore/tia/Audio.cxx
@@ -55,7 +55,7 @@ void Audio::reset()
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void Audio::setAudioQueue(shared_ptr<AudioQueue> queue)
+void Audio::setAudioQueue(const shared_ptr<AudioQueue>& queue)
 {
   myAudioQueue = queue;
 
diff --git a/src/emucore/tia/Audio.hxx b/src/emucore/tia/Audio.hxx
index 761b22080..8494c7934 100644
--- a/src/emucore/tia/Audio.hxx
+++ b/src/emucore/tia/Audio.hxx
@@ -31,7 +31,7 @@ class Audio : public Serializable
 
     void reset();
 
-    void setAudioQueue(shared_ptr<AudioQueue> queue);
+    void setAudioQueue(const shared_ptr<AudioQueue>& queue);
 
     void tick();
 
diff --git a/src/emucore/tia/TIA.cxx b/src/emucore/tia/TIA.cxx
index 698ae2bc0..dd5f901ee 100644
--- a/src/emucore/tia/TIA.cxx
+++ b/src/emucore/tia/TIA.cxx
@@ -66,7 +66,8 @@ enum ResxCounter: uInt8 {
 static constexpr uInt8 resxLateHblankThreshold = TIAConstants::H_CYCLES - 3;
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-TIA::TIA(ConsoleIO& console, ConsoleTimingProvider timingProvider, Settings& settings)
+TIA::TIA(ConsoleIO& console, const ConsoleTimingProvider& timingProvider,
+         Settings& settings)
   : myConsole(console),
     myTimingProvider(timingProvider),
     mySettings(settings),
@@ -112,7 +113,7 @@ void TIA::setFrameManager(AbstractFrameManager* frameManager)
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-void TIA::setAudioQueue(shared_ptr<AudioQueue> queue)
+void TIA::setAudioQueue(const shared_ptr<AudioQueue>& queue)
 {
   myAudio.setAudioQueue(queue);
 }
diff --git a/src/emucore/tia/TIA.hxx b/src/emucore/tia/TIA.hxx
index 74cde1f36..e6d79faeb 100644
--- a/src/emucore/tia/TIA.hxx
+++ b/src/emucore/tia/TIA.hxx
@@ -115,8 +115,8 @@ class TIA : public Device
       @param console   The console the TIA is associated with
       @param settings  The settings object for this TIA device
     */
-    TIA(ConsoleIO& console, ConsoleTimingProvider timingProvider, Settings& settings);
-
+    TIA(ConsoleIO& console, const ConsoleTimingProvider& timingProvider,
+        Settings& settings);
     virtual ~TIA() = default;
 
   public:
@@ -129,7 +129,7 @@ class TIA : public Device
       Set the audio queue. This needs to be dynamic as the queue is created after
       the timing has been determined.
     */
-    void setAudioQueue(shared_ptr<AudioQueue> audioQueue);
+    void setAudioQueue(const shared_ptr<AudioQueue>& audioQueue);
 
     /**
       Clear the configured frame manager and deteach the lifecycle callbacks.
diff --git a/src/emucore/tia/frame-manager/AbstractFrameManager.cxx b/src/emucore/tia/frame-manager/AbstractFrameManager.cxx
index 6ba5295c6..9f322173c 100644
--- a/src/emucore/tia/frame-manager/AbstractFrameManager.cxx
+++ b/src/emucore/tia/frame-manager/AbstractFrameManager.cxx
@@ -53,9 +53,10 @@ void AbstractFrameManager::nextLine()
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void AbstractFrameManager::setHandlers(
-  callback frameStartCallback,
-  callback frameCompletionCallback
-) {
+  const callback& frameStartCallback,
+  const callback& frameCompletionCallback
+)
+{
   myOnFrameStart = frameStartCallback;
   myOnFrameComplete = frameCompletionCallback;
 }
diff --git a/src/emucore/tia/frame-manager/AbstractFrameManager.hxx b/src/emucore/tia/frame-manager/AbstractFrameManager.hxx
index 7a20b7033..e37aa5488 100644
--- a/src/emucore/tia/frame-manager/AbstractFrameManager.hxx
+++ b/src/emucore/tia/frame-manager/AbstractFrameManager.hxx
@@ -40,8 +40,8 @@ class AbstractFrameManager : public Serializable
      * Configure the various handler callbacks.
      */
     void setHandlers(
-      callback frameStartCallback,
-      callback frameCompletionCallback
+      const callback& frameStartCallback,
+      const callback& frameCompletionCallback
     );
 
     /**
diff --git a/src/gui/DeveloperDialog.cxx b/src/gui/DeveloperDialog.cxx
index 28d50d5a4..95555035c 100644
--- a/src/gui/DeveloperDialog.cxx
+++ b/src/gui/DeveloperDialog.cxx
@@ -763,7 +763,6 @@ void DeveloperDialog::getWidgetStates(SettingsSet set)
   myTimeMachine[set] = myTimeMachineWidget->getState();
   myStateSize[set] = myStateSizeWidget->getValue();
   myUncompressed[set] = myUncompressedWidget->getValue();
-  myStateInterval[set] = myStateIntervalWidget->getSelected();
   myStateInterval[set] = myStateIntervalWidget->getSelectedTag().toString();
   myStateHorizon[set] = myStateHorizonWidget->getSelectedTag().toString();
 }
diff --git a/src/gui/FileListWidget.cxx b/src/gui/FileListWidget.cxx
index ac21298fe..a49b77939 100644
--- a/src/gui/FileListWidget.cxx
+++ b/src/gui/FileListWidget.cxx
@@ -58,7 +58,7 @@ void FileListWidget::setDirectory(const FilesystemNode& node, string select)
     if(name.back() == '/' || name.back() == '\\')
       name.pop_back();
     if(!BSPF::startsWithIgnoreCase(name, " ["))
-      name = " [" + name + "]";
+      name = " [" + name.append("]");
 
     _history.push(name);
     tmp = tmp.getParent();
diff --git a/src/gui/GameInfoDialog.cxx b/src/gui/GameInfoDialog.cxx
index 4acadc345..ddd27bde2 100644
--- a/src/gui/GameInfoDialog.cxx
+++ b/src/gui/GameInfoDialog.cxx
@@ -425,7 +425,7 @@ void GameInfoDialog::loadEmulationProperties(const Properties& props)
   }
   else
   {
-    string startBank = props.get(PropType::Cart_StartBank);
+    const string& startBank = props.get(PropType::Cart_StartBank);
 
     VarList::push_back(items, startBank, startBank);
     myStartBank->setEnabled(false);
diff --git a/src/gui/RomAuditDialog.cxx b/src/gui/RomAuditDialog.cxx
index c62176f0f..5e07e8cfd 100644
--- a/src/gui/RomAuditDialog.cxx
+++ b/src/gui/RomAuditDialog.cxx
@@ -127,7 +127,7 @@ void RomAuditDialog::auditRoms()
   progress.setRange(0, int(files.size()) - 1, 5);
 
   Properties props;
-  int renamed = 0, notfound = 0;
+  uInt32 renamed = 0, notfound = 0;
   for(uInt32 idx = 0; idx < files.size(); ++idx)
   {
     string extension;
@@ -162,8 +162,8 @@ void RomAuditDialog::auditRoms()
   }
   progress.close();
 
-  myResults1->setText(Variant(renamed).toString());
-  myResults2->setText(Variant(notfound).toString());
+  myResults1->setText(std::to_string(renamed));
+  myResults2->setText(std::to_string(notfound));
 }
 
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
diff --git a/src/gui/RomInfoWidget.hxx b/src/gui/RomInfoWidget.hxx
index 88639130f..ff893266f 100644
--- a/src/gui/RomInfoWidget.hxx
+++ b/src/gui/RomInfoWidget.hxx
@@ -20,7 +20,7 @@
 
 class FBSurface;
 class Properties;
-namespace GUI {
+namespace Common {
   struct Size;
 }