diff --git a/c/pthread/sync/_pthd/pthd.c b/c/pthread/sync/_pthd/pthd.c
index 453bbe4d..e8275a54 100644
--- a/c/pthread/sync/_pthd/pthd.c
+++ b/c/pthread/sync/_pthd/pthd.c
@@ -1,6 +1,7 @@
 #include <pthread.h>
 
-pthread_once_t llgoSyncOnceInitVal() {
-    pthread_once_t initVal = PTHREAD_ONCE_INIT;
-    return initVal;
-}
+// -----------------------------------------------------------------------------
+
+pthread_once_t llgoSyncOnceInitVal = PTHREAD_ONCE_INIT;
+
+// -----------------------------------------------------------------------------
diff --git a/c/pthread/sync/sync.go b/c/pthread/sync/sync.go
index 2ddf2ee9..9fd3dd03 100644
--- a/c/pthread/sync/sync.go
+++ b/c/pthread/sync/sync.go
@@ -30,12 +30,15 @@ const (
 	LLGoPackage = "link"
 )
 
+// -----------------------------------------------------------------------------
+
+// Once is an object that will perform exactly one action.
 type Once C.pthread_once_t
 
-//go:linkname onceInitVal C.llgoSyncOnceInitVal
-func onceInitVal() Once
-
-var OnceInit = onceInitVal()
+//go:linkname OnceInit llgoSyncOnceInitVal
+var OnceInit Once
 
 // llgo:link (*Once).Do C.pthread_once
 func (o *Once) Do(f func()) c.Int { return 0 }
+
+// -----------------------------------------------------------------------------
diff --git a/cl/_testlibgo/sync/in.go b/cl/_testlibgo/sync/in.go
new file mode 100644
index 00000000..1442dbbd
--- /dev/null
+++ b/cl/_testlibgo/sync/in.go
@@ -0,0 +1,18 @@
+package main
+
+import (
+	"sync"
+)
+
+var once sync.Once
+
+func f(s string) {
+	once.Do(func() {
+		println(s)
+	})
+}
+
+func main() {
+	f("Do once")
+	f("Do twice")
+}
diff --git a/cl/compile.go b/cl/compile.go
index ec18c06f..dbfe8fa1 100644
--- a/cl/compile.go
+++ b/cl/compile.go
@@ -279,6 +279,9 @@ func (p *context) compileFuncDecl(pkg llssa.Package, f *ssa.Function) (llssa.Fun
 			}
 			b.EndBuild()
 		})
+		for _, af := range f.AnonFuncs {
+			p.compileFuncDecl(pkg, af)
+		}
 	}
 	return fn, nil, goFunc
 }
diff --git a/cl/import.go b/cl/import.go
index fbbf4408..fc1bc46d 100644
--- a/cl/import.go
+++ b/cl/import.go
@@ -336,8 +336,14 @@ func typesFuncName(pkgPath string, fn *types.Func) (fullName, inPkgName string)
 // - func: pkg.name
 // - method: pkg.(T).name, pkg.(*T).name
 func funcName(pkg *types.Package, fn *ssa.Function) string {
-	sig := fn.Signature
-	return llssa.FuncName(pkg, fn.Name(), sig.Recv())
+	var recv *types.Var
+	parent := fn.Parent()
+	if parent != nil { // closure in method
+		recv = parent.Signature.Recv()
+	} else {
+		recv = fn.Signature.Recv()
+	}
+	return llssa.FuncName(pkg, fn.Name(), recv)
 }
 
 func checkCgo(fnName string) bool {
diff --git a/internal/lib/sync/sync.go b/internal/lib/sync/sync.go
index 56822964..63f22d78 100644
--- a/internal/lib/sync/sync.go
+++ b/internal/lib/sync/sync.go
@@ -18,5 +18,39 @@ package sync
 
 // llgo:skipall
 import (
-	_ "unsafe"
+	"unsafe"
+
+	"github.com/goplus/llgo/c"
+	"github.com/goplus/llgo/c/pthread"
+	"github.com/goplus/llgo/c/pthread/sync"
 )
+
+const (
+	LLGoPackage = "link"
+)
+
+// -----------------------------------------------------------------------------
+
+var onceParam pthread.Key
+
+func init() {
+	onceParam.Create(nil)
+}
+
+type Once sync.Once
+
+func (o *Once) Do(f func()) {
+	ptr := c.Malloc(unsafe.Sizeof(f))
+	*(*func())(ptr) = f
+	onceParam.Set(ptr)
+	if *(*c.Long)(unsafe.Pointer(o)) == 0 { // try init
+		*(*sync.Once)(o) = sync.OnceInit
+	}
+	(*sync.Once)(o).Do(func() {
+		ptr := onceParam.Get()
+		(*(*func())(ptr))()
+		c.Free(ptr)
+	})
+}
+
+// -----------------------------------------------------------------------------