cppintf: c++ name

_demo/cppintf/cppintf.go

@@ -34,4 +34,5 @@ func (p *Bar) sqrt(v float64) float64 {
 func main() {
 	bar := NewBar(1)
 	foo.F(&bar.Callback)
+	foo.G(&bar.Callback)
 }

_demo/cppintf/foo/bar/bar.cpp

@@ -9,3 +9,7 @@ interface ICallback {
 extern "C" void f(ICallback* cb) {
 	printf("val: %d\ncalc(2): %lf\n", cb->val(), cb->calc(2));
 }
+
+void g(ICallback* cb) {
+	f(cb);
+}

_demo/cppintf/foo/foo.go

@@ -20,3 +20,6 @@ type CallbackVtbl struct {
 
 //go:linkname F C.f
 func F(cb *Callback)
+
+//go:linkname G C._Z1gP9ICallback
+func G(cb *Callback)