Some C++20 additions.

src/common/HighScoresManager.cxx

@@ -462,8 +462,8 @@ Int32 HighScoresManager::convert(Int32 val, uInt32 maxVal, bool isBCD,
   //maxVal += zeroBased ? 0 : 1;
   maxVal -= zeroBased ? 1 : 0;
   const Int32 bits = isBCD
-    ? ceil(log(maxVal) / log(10) * 4)
-    : ceil(log(maxVal) / log(2));
+    ? ceil(log(maxVal) / std::numbers::ln10 * 4)
+    : ceil(log(maxVal) / std::numbers::ln2);
 
   // limit to maxVal's bits
   val %= 1 << bits;

src/common/Variant.hxx

@@ -60,26 +60,17 @@ class Variant
     const string& toString() const { return data; }
     const char* toCString() const { return data.c_str(); }
     Int32 toInt() const {
-      istringstream ss(data);
-      Int32 parsed;
-      ss >> parsed;
-
-      return parsed;
+      try { return std::stoi(data); } catch(...) { return 0; }
     }
     float toFloat() const {
-      istringstream ss(data);
-      float parsed;
-      ss >> parsed;
-
-      return parsed;
+      try { return std::stof(data); } catch(...) { return 0.F; }
     }
-    bool toBool() const         { return data == "1" || data == "true"; }
+    bool toBool() const { return data == "1" || data == "true"; }
     Common::Size toSize() const { return Common::Size(data); }
     Common::Point toPoint() const { return Common::Point(data); }
 
     // Comparison
-    bool operator==(const Variant& v) const { return data == v.data; }
-    bool operator!=(const Variant& v) const { return data != v.data; }
+    bool operator<=>(const Variant& v) const = default;
 
     friend ostream& operator<<(ostream& os, const Variant& v) {
       return os << v.data;

src/emucore/QuadTari.cxx

@@ -38,7 +38,6 @@ QuadTari::QuadTari(Jack jack, const OSystem& osystem, const System& system,
     myOSystem{osystem},
     myProperties{properties}
 {
-  Controller::Type firstType, secondType;
   string first, second;
 
   if(jack == Controller::Jack::Left)
@@ -51,8 +50,8 @@ QuadTari::QuadTari(Jack jack, const OSystem& osystem, const System& system,
     first = properties.get(PropType::Controller_Right1);
     second = properties.get(PropType::Controller_Right2);
   }
-  firstType = Controller::getType(first);
-  secondType = Controller::getType(second);
+  Controller::Type firstType = Controller::getType(first),
+                   secondType = Controller::getType(second);
 
   // Autodetect QuadTari controllers:
   // This will detect the same controller for 1st and 2nd controller

src/gui/QuadTariDialog.cxx

@@ -134,8 +134,6 @@ void QuadTariDialog::show(bool enableLeft, bool enableRight)
 // - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 void QuadTariDialog::loadControllerProperties(const Properties& props)
 {
-  string controller;
-
   if(myLeftPortLabel->isEnabled())
   {
     defineController(props, PropType::Controller_Left1, Controller::Jack::Left,
@@ -160,7 +158,7 @@ void QuadTariDialog::defineController(const Properties& props, PropType key,
   ByteBuffer image;
   size_t size = 0;
 
-  string controllerName = props.get(key);
+  const string& controllerName = props.get(key);
   popupWidget->setSelected(controllerName, "AUTO");
 
   // try to load the image for auto detection
@@ -173,7 +171,7 @@ void QuadTariDialog::defineController(const Properties& props, PropType key,
       && (image = instance().openROM(node, md5, size)) != nullptr;
   }
   string label;
-  Controller::Type type = Controller::getType(popupWidget->getSelectedTag().toString());
+  const Controller::Type type = Controller::getType(popupWidget->getSelectedTag().toString());
 
   if(type == Controller::Type::Unknown)
   {

src/gui/RomImageWidget.cxx

@@ -323,7 +323,7 @@ bool RomImageWidget::loadPng(const string& fileName)
         break;
       }
       if(data.first == "Software"
-          && data.second.toString().find("Stella") == 0)
+          && data.second.toString().starts_with("Stella"))
         myLabel = "Snapshot"; // default for Stella snapshots with missing "Title" meta data
     }
     return true;