Found a solution to make RVO in ATNDeserializer work.

Visual Studio needs a move constructor. The move assignment is not enough. No need for the copy constructor anymore, so it can go.

runtime/Cpp/demo/Windows/antlr4-cpp-demo/main.cpp

@@ -20,6 +20,7 @@ using namespace antlrcpptest;
 using namespace org::antlr::v4::runtime;
 
 int main(int argc, const char * argv[]) {
+
   ANTLRInputStream input(L"divideŴ and conquer");
   TLexer lexer(&input);
   CommonTokenStream tokens(&lexer);
@@ -27,7 +28,7 @@ int main(int argc, const char * argv[]) {
   TParser parser(&tokens);
   std::shared_ptr<tree::ParseTree> tree = parser.main();
 
-  std::wstring s = tree->toStringTree(&parser);
+  std::wstring s = tree->toStringTree(&parser) + L"\n";
   OutputDebugString(s.data());
 
   return 0;

runtime/Cpp/runtime/atn/ATN.cpp

@@ -49,19 +49,16 @@ using namespace antlrcpp;
 ATN::ATN() : ATN(ATNType::LEXER, 0) {
 }
 
-/**
- * Required to be defined (even though not used) as we have an explicit move assignment operator.
- */
-ATN::ATN(const ATN &other) {
-  states = other.states;
-  decisionToState = other.decisionToState;
-  ruleToStartState = other.ruleToStartState;
-  ruleToStopState = other.ruleToStopState;
-  grammarType = other.grammarType;
-  maxTokenType = other.maxTokenType;
-  ruleToTokenType = other.ruleToTokenType;
-  ruleToActionIndex = other.ruleToActionIndex;
-  modeToStartState = other.modeToStartState;
+ATN::ATN(ATN &&other) {
+  states = std::move(other.states);
+  decisionToState = std::move(other.decisionToState);
+  ruleToStartState = std::move(other.ruleToStartState);
+  ruleToStopState = std::move(other.ruleToStopState);
+  grammarType = std::move(other.grammarType);
+  maxTokenType = std::move(other.maxTokenType);
+  ruleToTokenType = std::move(other.ruleToTokenType);
+  ruleToActionIndex = std::move(other.ruleToActionIndex);
+  modeToStartState = std::move(other.modeToStartState);
 }
 
 ATN::ATN(ATNType grammarType, size_t maxTokenType) : grammarType(grammarType), maxTokenType(maxTokenType) {
@@ -69,7 +66,7 @@ ATN::ATN(ATNType grammarType, size_t maxTokenType) : grammarType(grammarType), m
 
 ATN::~ATN() {
   for (ATNState *state : states) {
-    //delete state;
+    delete state;
   }
 }
 

runtime/Cpp/runtime/atn/ATN.h

@@ -45,7 +45,7 @@ namespace atn {
 
     /// Used for runtime deserialization of ATNs from strings.
     ATN();
-    ATN(const ATN &other);
+    ATN(ATN &&other);
     ATN(ATNType grammarType, size_t maxTokenType);
     ~ATN();