diff --git a/src/frontend/cxx/frontend.cc b/src/frontend/cxx/frontend.cc
index 7f1e0fd5..78fc6531 100644
--- a/src/frontend/cxx/frontend.cc
+++ b/src/frontend/cxx/frontend.cc
@@ -340,7 +340,7 @@ auto runOnFile(const CLI& cli, const std::string& fileName) -> bool {
 
   if (!shouldExit) {
     unit.parse(ParserConfiguration{
-        .checkTypes = cli.opt_fcheck,
+        .checkTypes = cli.opt_fcheck || unit.language() == LanguageKind::kC,
         .fuzzyTemplateResolution = true,
         .reflect = !cli.opt_fno_reflect,
     });
diff --git a/src/mlir/cxx/mlir/CxxOps.td b/src/mlir/cxx/mlir/CxxOps.td
index 765d80bc..9a6dd7a3 100644
--- a/src/mlir/cxx/mlir/CxxOps.td
+++ b/src/mlir/cxx/mlir/CxxOps.td
@@ -133,7 +133,7 @@ def Cxx_CallOp : Cxx_Op<"call"> {
     OptionalAttr<DictArrayAttr>:$res_attrs
   );
 
-  let results = (outs AnyType);
+  let results = (outs Optional<AnyType>:$result);
 }
 
 def Cxx_AllocaOp : Cxx_Op<"alloca"> {
diff --git a/src/mlir/cxx/mlir/codegen_expressions.cc b/src/mlir/cxx/mlir/codegen_expressions.cc
index 44903236..dab589e2 100644
--- a/src/mlir/cxx/mlir/codegen_expressions.cc
+++ b/src/mlir/cxx/mlir/codegen_expressions.cc
@@ -465,7 +465,7 @@ auto Codegen::ExpressionVisitor::operator()(SubscriptExpressionAST* ast)
 
 auto Codegen::ExpressionVisitor::operator()(CallExpressionAST* ast)
     -> ExpressionResult {
-  auto check_direct_call = [&]() -> ExpressionResult {
+  auto check_direct_call = [&]() -> std::optional<ExpressionResult> {
     auto func = ast->baseExpression;
 
     while (auto nested = ast_cast<NestedExpressionAST>(func)) {
@@ -490,16 +490,20 @@ auto Codegen::ExpressionVisitor::operator()(CallExpressionAST* ast)
     auto loc = gen.getLocation(ast->lparenLoc);
 
     auto functionType = type_cast<FunctionType>(functionSymbol->type());
-    auto resultType = gen.convertType(functionType->returnType());
+    mlir::SmallVector<mlir::Type> resultTypes;
+    if (!control()->is_void(functionType->returnType())) {
+      resultTypes.push_back(gen.convertType(functionType->returnType()));
+    }
+
     auto op = gen.builder_.create<mlir::cxx::CallOp>(
-        loc, resultType, funcOp.getSymName(), arguments, mlir::ArrayAttr{},
+        loc, resultTypes, funcOp.getSymName(), arguments, mlir::ArrayAttr{},
         mlir::ArrayAttr{});
 
-    return {op};
+    return ExpressionResult{op.getResult()};
   };
 
-  if (auto op = check_direct_call(); op.value) {
-    return op;
+  if (auto op = check_direct_call(); op.has_value()) {
+    return *op;
   }
 
   auto op =
diff --git a/src/mlir/cxx/mlir/cxx_dialect_conversions.cc b/src/mlir/cxx/mlir/cxx_dialect_conversions.cc
index 76a7038f..ad65af0f 100644
--- a/src/mlir/cxx/mlir/cxx_dialect_conversions.cc
+++ b/src/mlir/cxx/mlir/cxx_dialect_conversions.cc
@@ -124,16 +124,16 @@ class CallOpLowering : public OpConversionPattern<cxx::CallOp> {
       argumentTypes.push_back(convertedType);
     }
 
-    auto resultType = typeConverter->convertType(op.getType());
-    if (!resultType) {
+    SmallVector<Type> resultTypes;
+    if (failed(typeConverter->convertTypes(op.getResultTypes(), resultTypes))) {
       return rewriter.notifyMatchFailure(op,
                                          "failed to convert call result types");
     }
 
     auto llvmCallOp = rewriter.create<LLVM::CallOp>(
-        op.getLoc(), resultType, adaptor.getCallee(), adaptor.getInputs());
+        op.getLoc(), resultTypes, adaptor.getCallee(), adaptor.getInputs());
 
-    rewriter.replaceOp(op, llvmCallOp.getResults());
+    rewriter.replaceOp(op, llvmCallOp);
     return success();
   }
 };
@@ -875,6 +875,10 @@ void CxxToLLVMLoweringPass::runOnOperation() {
   // set up the type converter
   LLVMTypeConverter typeConverter{context};
 
+  typeConverter.addConversion([](cxx::VoidType type) {
+    return LLVM::LLVMVoidType::get(type.getContext());
+  });
+
   typeConverter.addConversion([](cxx::BoolType type) {
     // todo: i8/i32 for data and i1 for control flow
     return IntegerType::get(type.getContext(), 1);
diff --git a/src/parser/cxx/parser.cc b/src/parser/cxx/parser.cc
index 46ea9882..07a8f9be 100644
--- a/src/parser/cxx/parser.cc
+++ b/src/parser/cxx/parser.cc
@@ -3288,6 +3288,8 @@ void Parser::parse_init_statement(StatementAST*& yyast) {
 
 void Parser::parse_condition(ExpressionAST*& yyast, const ExprContext& ctx) {
   auto lookat_condition = [&] {
+    if (!is_parsing_cxx()) return false;
+
     LookaheadParser lookahead{this};
 
     List<AttributeSpecifierAST*>* attributes = nullptr;
diff --git a/src/parser/cxx/type_checker.cc b/src/parser/cxx/type_checker.cc
index 4e985020..19661448 100644
--- a/src/parser/cxx/type_checker.cc
+++ b/src/parser/cxx/type_checker.cc
@@ -140,6 +140,9 @@ struct TypeChecker::Visitor {
   [[nodiscard]] auto check_static_cast(ExpressionAST*& expression,
                                        const Type* targetType) -> bool;
 
+  [[nodiscard]] auto check_const_cast(ExpressionAST*& expression,
+                                      const Type* targetType) -> bool;
+
   [[nodiscard]] auto check_cast_to_derived(ExpressionAST* expression,
                                            const Type* targetType) -> bool;
 
@@ -467,13 +470,13 @@ void TypeChecker::Visitor::operator()(CallExpressionAST* ast) {
 
   if (!functionType) {
     if (control()->is_pointer(ast->baseExpression->type)) {
-      // ressolve pointer to function type
+      // resolve pointer to function type
       functionType = type_cast<FunctionType>(
           control()->get_element_type(ast->baseExpression->type));
-    }
 
-    if (functionType && is_parsing_c()) {
-      (void)ensure_prvalue(ast->baseExpression);
+      if (functionType && is_parsing_c()) {
+        (void)ensure_prvalue(ast->baseExpression);
+      }
     }
   }
 
@@ -489,6 +492,46 @@ void TypeChecker::Visitor::operator()(CallExpressionAST* ast) {
   }
 
   // TODO: check the arguments
+  if (is_parsing_c()) {
+    const auto& argumentTypes = functionType->parameterTypes();
+
+    int argc = 0;
+    for (auto it = ast->expressionList; it; it = it->next) {
+      if (!it->value) {
+        error(ast->firstSourceLocation(),
+              "invalid call with null argument expression");
+        continue;
+      }
+
+      if (argc >= argumentTypes.size()) {
+        if (functionType->isVariadic()) {
+          // do the promotion for the variadic arguments
+          (void)ensure_prvalue(it->value);
+          adjust_cv(it->value);
+
+          if (integral_promotion(it->value)) continue;
+          if (floating_point_promotion(it->value)) continue;
+
+          continue;
+        }
+
+        error(it->value->firstSourceLocation(),
+              std::format("too many arguments for function of type '{}'",
+                          to_string(functionType)));
+        break;
+      }
+
+      auto targetType = argumentTypes[argc];
+      ++argc;
+
+      if (!implicit_conversion(it->value, targetType)) {
+        error(it->value->firstSourceLocation(),
+              std::format("invalid argument of type '{}' for parameter of type "
+                          "'{}'",
+                          to_string(it->value->type), to_string(targetType)));
+      }
+    }
+  }
 
   ast->type = functionType->returnType();
 
@@ -579,13 +622,23 @@ void TypeChecker::Visitor::operator()(CppCastExpressionAST* ast) {
   check_cpp_cast_expression(ast);
 
   switch (check.unit_->tokenKind(ast->castLoc)) {
-    case TokenKind::T_STATIC_CAST:
+    case TokenKind::T_STATIC_CAST: {
       if (check_static_cast(ast->expression, ast->type)) break;
       error(
           ast->firstSourceLocation(),
           std::format("invalid static_cast of '{}' to '{}'",
                       to_string(ast->expression->type), to_string(ast->type)));
       break;
+    }
+
+    case TokenKind::T_CONST_CAST: {
+      if (check_const_cast(ast->expression, ast->type)) break;
+      error(
+          ast->firstSourceLocation(),
+          std::format("invalid const_cast of '{}' to '{}'",
+                      to_string(ast->expression->type), to_string(ast->type)));
+      break;
+    }
 
     default:
       break;
@@ -653,6 +706,11 @@ auto TypeChecker::Visitor::check_static_cast(ExpressionAST*& expression,
   return true;
 }
 
+auto TypeChecker::Visitor::check_const_cast(ExpressionAST*& expression,
+                                            const Type* targetType) -> bool {
+  return false;
+}
+
 auto TypeChecker::Visitor::check_cast_to_derived(ExpressionAST* expression,
                                                  const Type* targetType)
     -> bool {
@@ -967,6 +1025,7 @@ void TypeChecker::Visitor::operator()(CastExpressionAST* ast) {
   }
 
   if (check_static_cast(ast->expression, ast->type)) return;
+  if (check_const_cast(ast->expression, ast->type)) return;
   // check the other casts
 }
 
@@ -1659,9 +1718,11 @@ auto TypeChecker::Visitor::pointer_conversion(ExpressionAST*& expr,
     const auto destinationPointerType = type_cast<PointerType>(destinationType);
     if (!destinationPointerType) return false;
 
-    if (control()->get_cv_qualifiers(pointerType->elementType()) !=
-        control()->get_cv_qualifiers(destinationPointerType->elementType()))
-      return false;
+    auto sourceCv = control()->get_cv_qualifiers(pointerType->elementType());
+    auto targetCv =
+        control()->get_cv_qualifiers(destinationPointerType->elementType());
+
+    if (!check_cv_qualifiers(targetCv, sourceCv)) return false;
 
     if (!control()->is_void(destinationPointerType->elementType()))
       return false;
@@ -1812,7 +1873,19 @@ auto TypeChecker::Visitor::temporary_materialization_conversion(
 auto TypeChecker::Visitor::qualification_conversion(ExpressionAST*& expr,
                                                     const Type* destinationType)
     -> bool {
-  return false;
+  auto type = get_qualification_combined_type(expr->type, destinationType);
+  if (!type) return false;
+
+  if (!control()->is_same(destinationType, type)) return false;
+
+  auto cast = make_node<ImplicitCastExpressionAST>(arena());
+  cast->castKind = ImplicitCastKind::kQualificationConversion;
+  cast->expression = expr;
+  cast->type = destinationType;
+  cast->valueCategory = expr->valueCategory;
+  expr = cast;
+
+  return true;
 }
 
 auto TypeChecker::Visitor::ensure_prvalue(ExpressionAST*& expr) -> bool {