diff --git a/_demo/cppstr/cppstr.go b/_demo/cppstr/cppstr.go
new file mode 100644
index 00000000..25bb941a
--- /dev/null
+++ b/_demo/cppstr/cppstr.go
@@ -0,0 +1,12 @@
+package main
+
+import (
+	"github.com/goplus/lib/c"
+	"github.com/goplus/lib/cpp/std"
+)
+
+func main() {
+	s := std.Str("Hello world\n")
+	c.Printf(s.CStr())
+	print(s.Str(), s.Size(), "\n")
+}