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

_demo/cppintf/cppintf.go

@@ -0,0 +1,37 @@
+package main
+
+import (
+	"github.com/goplus/llgo/_demo/cppintf/foo"
+	"github.com/goplus/llgo/c"
+)
+
+type Bar struct {
+	foo.Callback
+	a int
+	b float64
+}
+
+func NewBar(a int, b float64) *Bar {
+	return &Bar{
+		Callback: foo.Callback{
+			Vptr: &foo.CallbackVtbl{
+				ValA: c.Func((*Bar).getA),
+				ValB: c.Func((*Bar).getB),
+			},
+		},
+		a: a, b: b,
+	}
+}
+
+func (p *Bar) getA() int {
+	return p.a
+}
+
+func (p *Bar) getB() float64 {
+	return p.b
+}
+
+func main() {
+	bar := NewBar(1, 2.0)
+	foo.F(&bar.Callback)
+}

_demo/cppintf/foo/bar/bar.cpp

@@ -0,0 +1,11 @@
+#include <stdio.h>
+#define interface struct
+
+interface ICallback {
+	virtual int valA() = 0;
+	virtual double valB() = 0;
+};
+
+extern "C" void f(ICallback* cb) {
+	printf("Hello %d, %lf!\n", cb->valA(), cb->valB());
+}

_demo/cppintf/foo/foo.go

@@ -0,0 +1,22 @@
+package foo
+
+import (
+	"unsafe"
+)
+
+const (
+	LLGoFiles   = "bar/bar.cpp"
+	LLGoPackage = "link"
+)
+
+type Callback struct {
+	Vptr *CallbackVtbl
+}
+
+type CallbackVtbl struct {
+	ValA unsafe.Pointer
+	ValB unsafe.Pointer
+}
+
+//go:linkname F C.f
+func F(cb *Callback)