diff --git a/cl/_testcgo/hello/out.ll b/cl/_testcgo/hello/out.ll
index 0975dbc3..93ba0f3e 100644
--- a/cl/_testcgo/hello/out.ll
+++ b/cl/_testcgo/hello/out.ll
@@ -11,7 +11,6 @@ _llgo_0:
 
 _llgo_1:                                          ; preds = %_llgo_0
   store i1 true, ptr @"main.init$guard", align 1
-  call void @"github.com/goplus/llgo/cl/internal/libc.init"()
   store i8 72, ptr @main.format, align 1
   store i8 101, ptr getelementptr inbounds (i8, ptr @main.format, i64 1), align 1
   store i8 108, ptr getelementptr inbounds (i8, ptr @main.format, i64 2), align 1
@@ -36,8 +35,6 @@ _llgo_0:
   ret void
 }
 
-declare void @"github.com/goplus/llgo/cl/internal/libc.init"()
-
 declare i32 @strlen(ptr)
 
 declare void @"github.com/goplus/llgo/cl/internal/libc.Printf"(ptr, ...)
diff --git a/cl/builtin_test.go b/cl/builtin_test.go
index 8eabda7c..de5ce57d 100644
--- a/cl/builtin_test.go
+++ b/cl/builtin_test.go
@@ -48,7 +48,7 @@ func TestIgnoreName(t *testing.T) {
 func TestErrImport(t *testing.T) {
 	var ctx context
 	pkg := types.NewPackage("foo", "foo")
-	ctx.importPkg(pkg)
+	ctx.importPkg(pkg, nil)
 }
 
 func TestErrInitLinkname(t *testing.T) {
diff --git a/cl/compile.go b/cl/compile.go
index 57eea93c..b8556a76 100644
--- a/cl/compile.go
+++ b/cl/compile.go
@@ -61,12 +61,12 @@ const (
 	fnIgnore
 )
 
-func funcKind(vfn ssa.Value) int {
+func (p *context) funcKind(vfn ssa.Value) int {
 	if fn, ok := vfn.(*ssa.Function); ok && fn.Signature.Recv() == nil {
 		params := fn.Signature.Params()
 		n := params.Len()
 		if n == 0 {
-			if fn.Name() == "init" && ignorePkgInit(fn.Pkg.Pkg.Path()) {
+			if fn.Name() == "init" && p.pkgNoInit(fn.Pkg.Pkg) {
 				return fnIgnore
 			}
 		} else {
@@ -79,10 +79,10 @@ func funcKind(vfn ssa.Value) int {
 	return fnNormal
 }
 
-func ignorePkgInit(pkgPath string) bool {
-	switch pkgPath {
-	case "unsafe", "syscall", "runtime/cgo":
-		return true
+func (p *context) pkgNoInit(pkg *types.Package) bool {
+	p.ensureLoaded(pkg)
+	if i, ok := p.loaded[pkg]; ok {
+		return i.kind != pkgNormal
 	}
 	return false
 }
@@ -113,13 +113,21 @@ func inPkg(name, pkg string) bool {
 
 // -----------------------------------------------------------------------------
 
-type none = struct{}
-
 type instrOrValue interface {
 	ssa.Instruction
 	ssa.Value
 }
 
+const (
+	pkgNormal   = iota
+	pkgNoInit   // noinit: a package that don't need to be initialized
+	pkgDeclOnly // decl: a package that only have declarations
+)
+
+type pkgInfo struct {
+	kind int
+}
+
 type context struct {
 	prog   llssa.Program
 	pkg    llssa.Package
@@ -129,7 +137,7 @@ type context struct {
 	goTyps *types.Package
 	goPkg  *ssa.Package
 	link   map[string]string           // pkgPath.nameInPkg => linkname
-	loaded map[*types.Package]none     // loaded packages
+	loaded map[*types.Package]*pkgInfo // loaded packages
 	bvals  map[ssa.Value]llssa.Expr    // block values
 	vargs  map[*ssa.Alloc][]llssa.Expr // varargs
 	inits  []func()
@@ -271,7 +279,7 @@ func (p *context) compileInstrOrValue(b llssa.Builder, iv instrOrValue, asValue
 	case *ssa.Call:
 		call := v.Call
 		cv := call.Value
-		kind := funcKind(cv)
+		kind := p.funcKind(cv)
 		if kind == fnIgnore {
 			return
 		}
@@ -484,8 +492,10 @@ func NewPackage(prog llssa.Program, pkg *ssa.Package, files []*ast.File) (ret ll
 		goTyps: pkgTypes,
 		goPkg:  pkg,
 		link:   make(map[string]string),
-		loaded: make(map[*types.Package]none),
 		vargs:  make(map[*ssa.Alloc][]llssa.Expr),
+		loaded: map[*types.Package]*pkgInfo{
+			types.Unsafe: {kind: pkgNoInit}, // TODO(xsw): pkgNoInit or pkgDeclOnly?
+		},
 	}
 	ctx.initFiles(pkgPath, files)
 	for _, m := range members {
diff --git a/cl/import.go b/cl/import.go
index 1f351476..bd9a28fb 100644
--- a/cl/import.go
+++ b/cl/import.go
@@ -19,6 +19,7 @@ package cl
 import (
 	"bytes"
 	"go/ast"
+	"go/constant"
 	"go/token"
 	"go/types"
 	"os"
@@ -43,11 +44,27 @@ func contentOf(m contentMap, file string) (lines contentLines, err error) {
 	return
 }
 
-func (p *context) importPkg(pkg *types.Package) {
+// decl: a package that only contains declarations
+// noinit: a package that does not need to be initialized
+func pkgKind(v string) int {
+	switch v {
+	case "decl":
+		return pkgDeclOnly
+	case "noinit":
+		return pkgNoInit
+	}
+	return pkgNormal
+}
+
+func (p *context) importPkg(pkg *types.Package, i *pkgInfo) {
 	scope := pkg.Scope()
-	if scope.Lookup("LLGoPackage") == nil {
+	llpkg, ok := scope.Lookup("LLGoPackage").(*types.Const)
+	if !ok {
 		return
 	}
+	if v := llpkg.Val(); v.Kind() == constant.String {
+		i.kind = pkgKind(constant.StringVal(v))
+	}
 	fset := p.fset
 	names := scope.Names()
 	contents := make(contentMap)
@@ -170,9 +187,20 @@ func (p *context) varOf(v *ssa.Global) llssa.Global {
 func (p *context) ensureLoaded(pkgTypes *types.Package) *types.Package {
 	if p.goTyps != pkgTypes {
 		if _, ok := p.loaded[pkgTypes]; !ok {
-			p.loaded[pkgTypes] = none{}
-			p.importPkg(pkgTypes)
+			i := &pkgInfo{
+				kind: pkgKindByPath(pkgTypes.Path()),
+			}
+			p.loaded[pkgTypes] = i
+			p.importPkg(pkgTypes, i)
 		}
 	}
 	return pkgTypes
 }
+
+func pkgKindByPath(pkgPath string) int {
+	switch pkgPath {
+	case "syscall", "runtime/cgo":
+		return pkgNoInit
+	}
+	return pkgNormal
+}
diff --git a/cl/internal/libc/libc.go b/cl/internal/libc/libc.go
index 8828a4df..59b830d7 100644
--- a/cl/internal/libc/libc.go
+++ b/cl/internal/libc/libc.go
@@ -4,7 +4,7 @@ import "C"
 import _ "unsafe"
 
 const (
-	LLGoPackage = true
+	LLGoPackage = "decl"
 )
 
 //go:linkname Printf C.printf
diff --git a/internal/runtime/z_gc.go b/internal/runtime/c/c.go
similarity index 64%
rename from internal/runtime/z_gc.go
rename to internal/runtime/c/c.go
index 1aae6025..451d80b0 100644
--- a/internal/runtime/z_gc.go
+++ b/internal/runtime/c/c.go
@@ -14,18 +14,28 @@
  * limitations under the License.
  */
 
-package runtime
+package c
 
 import "unsafe"
 
 const (
-	LLGoPackage = true
+	LLGoPackage = "decl"
 )
 
+//go:linkname String llgo.CString
+func String(string) *int8
+
+//go:linkname Alloca llgo.Alloca
+func Alloca(size uintptr) unsafe.Pointer
+
+//go:linkname Unreachable llgo.Unreachable
+func Unreachable()
+
 //go:linkname Malloc C.malloc
 func Malloc(size uintptr) unsafe.Pointer
 
-// Alloc allocates memory.
-func Alloc(size uintptr) unsafe.Pointer {
-	return Malloc(size)
-}
+//go:linkname Memcpy C.memcpy
+func Memcpy(dst, src unsafe.Pointer, n uintptr) unsafe.Pointer
+
+//go:linkname Printf C.printf
+func Printf(format *int8, __llgo_va_list ...any)
diff --git a/internal/runtime/z_c.go b/internal/runtime/z_c.go
new file mode 100644
index 00000000..6cca5b99
--- /dev/null
+++ b/internal/runtime/z_c.go
@@ -0,0 +1,44 @@
+/*
+ * 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/runtime/c"
+)
+
+// Alloc allocates memory.
+func Alloc(size uintptr) unsafe.Pointer {
+	return c.Malloc(size)
+}
+
+/*
+// Panic panics with a value.
+func Panic(v Interface) {
+	c.Printf(c.String("Panic!!!\n"))
+	kind := abi.Kind(v.tab._type.Kind_)
+	switch {
+	case kind == abi.String:
+		s := (*String)(v.data)
+		cs := c.Alloca(uintptr(s.len) + 1)
+		c.Memcpy(cs, s.data, uintptr(s.len))
+		(*[1 << 30]int8)(cs)[s.len] = 0
+		c.Printf(c.String("%s\n"), cs)
+	}
+}
+*/