cl: embed struct support __llgo_va_list

cl/_testrt/vamethod/in.go

@@ -0,0 +1,32 @@
+package main
+
+import (
+	"unsafe"
+	_ "unsafe"
+
+	"github.com/goplus/lib/c"
+)
+
+type T c.Char
+
+//go:linkname Printf C.printf
+func Printf(format *c.Char, __llgo_va_list ...any) c.Int
+
+//llgo:link (*T).Printf C.printf
+func (*T) Printf(__llgo_va_list ...any) c.Int { return 0 }
+
+type CFmt struct {
+	*T
+}
+
+func (f *CFmt) SetFormat(fmt string) {
+	f.T = (*T)(unsafe.Pointer(c.AllocaCStr(fmt)))
+}
+
+func main() {
+	cfmt := &CFmt{}
+	cfmt.SetFormat("%s (%d)\n")
+	cfmt.Printf(c.Str("hello"), 100)
+	cfmt.SetFormat("(%d) %s\n")
+	cfmt.Printf(200, c.Str("world"))
+}