Avoid unnecessary heap allocations for short-lived strings (#41)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: Nuno Lopes <nuno.lopes@tecnico.ulisboa.pt>

Author: Copilot

cpp2rust/converter/converter.cpp

@@ -2136,7 +2136,7 @@ std::string Converter::ConvertDeclRefExpr(clang::DeclRefExpr *expr) {
     return std::format("{}::{}",
                        GetRecordName(clang::dyn_cast<clang::EnumDecl>(
                            enum_constant->getDeclContext())),
-                       enum_constant->getName().str());
+                       std::string_view(enum_constant->getName()));
   } else if (IsGlobalVar(expr)) {
     return ReplaceAll(Mapper::ToString(expr->getDecl()), "::", "_");
   }
@@ -2612,12 +2612,12 @@ bool Converter::VisitEnumDecl(clang::EnumDecl *decl) {
   for (auto e : decl->enumerators()) {
     llvm::SmallVector<char, 32> init;
     e->getInitVal().toString(init, 10);
-    std::string init_str(init.begin(), init.end());
     if (first_enumerator) {
       StrCat("#[default]");
       first_enumerator = false;
     }
-    StrCat(std::format("{} = {},", e->getNameAsString(), init_str));
+    StrCat(std::format("{} = {},", std::string_view(e->getName()),
+                       std::string_view(init.data(), init.size())));
   }
   StrCat("}");
   return false;
@@ -2854,7 +2854,7 @@ std::string Converter::ConvertVarDefaultInit(clang::QualType qual_type) {
 
 std::string
 Converter::GetOverloadedFunctionName(const clang::FunctionDecl *decl) {
-  std::string name(decl->getNameAsString());
+  auto name = decl->getNameAsString();
 
   if (decl->getNumParams() != 0U) {
     name += '_';

cpp2rust/converter/mapper.cpp

@@ -443,7 +443,7 @@ void addBuiltinTypes(Model model) {
   auto build_rust_type = [&](clang::QualType qt) {
     unsigned bits = ctx_->getTypeSize(qt);
     char sign = qt->isSignedIntegerType() ? 'i' : 'u';
-    return std::string(1, sign) + std::to_string(bits);
+    return std::format("{}{}", sign, bits);
   };
 
   // Misc
@@ -858,10 +858,11 @@ std::string ToString(const clang::Expr *expr) {
   }
 
   if (const auto *uop = llvm::dyn_cast<clang::UnaryOperator>(expr)) {
-    std::string opcode =
-        clang::UnaryOperator::getOpcodeStr(uop->getOpcode()).str();
-    return uop->isPostfix() ? ToString(uop->getSubExpr()) + std::move(opcode)
-                            : std::move(opcode) + ToString(uop->getSubExpr());
+    auto sub = ToString(uop->getSubExpr());
+    std::string_view opcode =
+        clang::UnaryOperator::getOpcodeStr(uop->getOpcode());
+    return uop->isPostfix() ? std::format("{}{}", sub, opcode)
+                            : std::format("{}{}", opcode, sub);
   }
 
   return "Unhandled case in ToString";

cpp2rust/converter/models/converter_refcount.cpp

@@ -1757,7 +1757,7 @@ void ConverterRefCount::ConvertGenericBinaryOperator(
     clang::BinaryOperator *expr) {
   auto lhs = expr->getLHS();
   auto rhs = expr->getRHS();
-  auto opcode = expr->getOpcodeStr().str();
+  std::string_view opcode = expr->getOpcodeStr();
 
   auto lhs_vars = GetAllVars(lhs);
   auto rhs_vars = GetAllVars(rhs);