diff --git a/internal/runtime/c/c.go b/internal/runtime/c/c.go
index c26c8748..eb502d92 100644
--- a/internal/runtime/c/c.go
+++ b/internal/runtime/c/c.go
@@ -74,3 +74,9 @@ func Printf(format *Char, __llgo_va_list ...any) Int
 
 //go:linkname Fprintf C.fprintf
 func Fprintf(fp FilePtr, format *Char, __llgo_va_list ...any) Int
+
+//go:linkname Fwrite C.fwrite
+func Fwrite(data Pointer, size, count uintptr, fp FilePtr) uintptr
+
+//go:linkname Fputc C.fputc
+func Fputc(c Int, fp FilePtr) Int
diff --git a/internal/runtime/llgo_autogen.lla b/internal/runtime/llgo_autogen.lla
index 4187e819..bd66305d 100644
Binary files a/internal/runtime/llgo_autogen.lla and b/internal/runtime/llgo_autogen.lla differ
diff --git a/internal/runtime/runtime2.go b/internal/runtime/runtime2.go
index 027c408f..69d80ae1 100644
--- a/internal/runtime/runtime2.go
+++ b/internal/runtime/runtime2.go
@@ -13,11 +13,6 @@ type eface struct {
 	data  unsafe.Pointer
 }
 
-/*
-func efaceOf(ep *any) *eface {
-	return (*eface)(unsafe.Pointer(ep))
-}
-
 type iface struct {
 	tab  *itab
 	data unsafe.Pointer
@@ -35,6 +30,11 @@ type itab struct {
 	fun   [1]uintptr // variable sized. fun[0]==0 means _type does not implement inter.
 }
 
+/*
+func efaceOf(ep *any) *eface {
+	return (*eface)(unsafe.Pointer(ep))
+}
+
 func MakeInterface(inter *InterfaceType, typ *Type, data unsafe.Pointer) Interface {
 	tab := &itab{inter: inter, _type: typ, hash: 0, fun: [1]uintptr{0}}
 	return Interface{
diff --git a/internal/runtime/z_eface.go b/internal/runtime/z_eface.go
deleted file mode 100644
index a0f96d03..00000000
--- a/internal/runtime/z_eface.go
+++ /dev/null
@@ -1,70 +0,0 @@
-/*
- * 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 runtime
-
-import (
-	"unsafe"
-
-	"github.com/goplus/llgo/internal/abi"
-)
-
-type Eface = eface
-
-// -----------------------------------------------------------------------------
-
-func MakeAnyIntptr(typ *Type, data uintptr) Eface {
-	return eface{
-		_type: typ, data: unsafe.Pointer(data),
-	}
-}
-
-func MakeAnyString(data string) Eface {
-	typ := basicTypes[abi.String]
-	return eface{
-		_type: typ, data: unsafe.Pointer(&data),
-	}
-}
-
-func I2Int(v Eface, t *Type) uintptr {
-	if v._type == t {
-		return uintptr(v.data)
-	}
-	panic("I2Int: type mismatch")
-}
-
-func CheckI2Int(v Eface, t *Type) (uintptr, bool) {
-	if v._type == t {
-		return uintptr(v.data), true
-	}
-	return 0, false
-}
-
-func I2String(v Eface) string {
-	if v._type.Kind() == abi.String {
-		return *(*string)(v.data)
-	}
-	panic("I2String: type mismatch")
-}
-
-func CheckI2String(v Eface) (string, bool) {
-	if v._type.Kind() == abi.String {
-		return *(*string)(v.data), true
-	}
-	return "", false
-}
-
-// -----------------------------------------------------------------------------
diff --git a/internal/runtime/z_print.go b/internal/runtime/z_print.go
index 7aeca7f3..27a47ac7 100644
--- a/internal/runtime/z_print.go
+++ b/internal/runtime/z_print.go
@@ -7,7 +7,7 @@ package runtime
 import (
 	"unsafe"
 
-	"github.com/goplus/llgo/c"
+	"github.com/goplus/llgo/internal/runtime/c"
 )
 
 func PrintByte(v byte) {
diff --git a/internal/runtime/z_type.go b/internal/runtime/z_type.go
index e28dd638..93eb6420 100644
--- a/internal/runtime/z_type.go
+++ b/internal/runtime/z_type.go
@@ -22,11 +22,47 @@ import (
 	"github.com/goplus/llgo/internal/abi"
 )
 
-// -----------------------------------------------------------------------------
+type (
+	Eface = eface
+	Iface = iface
+	Itab  = itab
+)
 
 type Kind = abi.Kind
 type Type = abi.Type
 
+type InterfaceType = abi.InterfaceType
+
+// -----------------------------------------------------------------------------
+
+// Interface returns an interface type.
+func Interface(pkgPath string) *Type {
+	// TODO(xsw): pkgPath
+	// npkg := abi.NewName(pkgPath, "", false, false)
+	ret := &abi.InterfaceType{
+		Type: Type{
+			Size_: unsafe.Sizeof(eface{}),
+			Hash:  uint32(abi.Interface), // TODO(xsw): hash
+			Kind_: uint8(abi.Interface),
+		},
+		//PkgPath: npkg,
+		Methods: nil,
+	}
+	return &ret.Type
+}
+
+// NewItab returns a new itab.
+func NewItab(inter *InterfaceType, typ *Type) *Itab {
+	return &itab{
+		inter: inter,
+		_type: typ,
+		hash:  typ.Hash,
+		//fun: nil, TODO(xsw)
+	}
+}
+
+// -----------------------------------------------------------------------------
+
 func Basic(kind Kind) *Type {
 	return basicTypes[kind]
 }