diff --git a/cpp/std/std_gc.go b/cpp/std/std_gc.go
new file mode 100644
index 00000000..21902954
--- /dev/null
+++ b/cpp/std/std_gc.go
@@ -0,0 +1,39 @@
+//go:build !nogc
+// +build !nogc
+
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package std
+
+import (
+	"unsafe"
+
+	"github.com/goplus/llgo/c"
+	"github.com/goplus/llgo/c/bdwgc"
+)
+
+// -----------------------------------------------------------------------------
+
+func allocString() *String {
+	ptr := bdwgc.Malloc(unsafe.Sizeof(String{}))
+	bdwgc.RegisterFinalizer(ptr, func(obj, data c.Pointer) {
+		(*String)(obj).Dispose()
+	}, nil, nil, nil)
+	return (*String)(ptr)
+}
+
+// -----------------------------------------------------------------------------
diff --git a/cpp/std/std_nogc.go b/cpp/std/std_nogc.go
new file mode 100644
index 00000000..20f8c880
--- /dev/null
+++ b/cpp/std/std_nogc.go
@@ -0,0 +1,35 @@
+//go:build nogc
+// +build nogc
+
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package std
+
+import (
+	"unsafe"
+
+	"github.com/goplus/llgo/c"
+)
+
+// -----------------------------------------------------------------------------
+
+func allocString() *String {
+	ptr := c.Malloc(unsafe.Sizeof(String{}))
+	return (*String)(ptr)
+}
+
+// -----------------------------------------------------------------------------
diff --git a/cpp/std/string.go b/cpp/std/string.go
index fa04524f..5427a51a 100644
--- a/cpp/std/string.go
+++ b/cpp/std/string.go
@@ -20,7 +20,6 @@ import (
 	"unsafe"
 
 	"github.com/goplus/llgo/c"
-	"github.com/goplus/llgo/c/bdwgc"
 )
 
 // -----------------------------------------------------------------------------
@@ -32,7 +31,7 @@ type StringView = string
 
 // String represents a C++ std::string object.
 type String struct {
-	Unused [24]byte
+	Unused [3]uintptr
 }
 
 // llgo:link (*String).InitEmpty C.stdStringInitEmpty
@@ -52,14 +51,6 @@ func (s *String) Dispose() {}
 
 // -----------------------------------------------------------------------------
 
-func allocString() *String {
-	ptr := bdwgc.Malloc(unsafe.Sizeof(String{}))
-	bdwgc.RegisterFinalizer(ptr, func(obj, data c.Pointer) {
-		(*String)(obj).Dispose()
-	}, nil, nil, nil)
-	return (*String)(ptr)
-}
-
 // NewString creates a C++ std::string object.
 func NewString(v string) *String {
 	ret := allocString()