cl: c.Func (llgo.funcAddr); demo: cppintf (how to use c++ interface)

cl/_testlibc/complex/in.go

@@ -1,10 +1,12 @@
 package main
 
 import (
+	"github.com/goplus/llgo/c"
 	"github.com/goplus/llgo/c/math/cmplx"
 )
 
-func f(c, z complex64) {
+func f(c, z complex64, addr c.Pointer) {
+	println("addr:", addr)
 	println("abs(3+4i):", cmplx.Absf(c))
 	println("real(3+4i):", real(z))
 	println("imag(3+4i):", imag(z))
@@ -14,6 +16,6 @@ func main() {
 	re := float32(3.0)
 	im := float32(4.0)
 	z := complex64(3 + 4i)
-	c := complex(re, im)
-	f(c, z)
+	x := complex(re, im)
+	f(x, z, c.Func(f))
 }