cppmintf: implements multiple intefaces in c++

_demo/cppmintf/cpp_multi_intf.go

@@ -0,0 +1,50 @@
+package main
+
+import (
+	"unsafe"
+
+	"github.com/goplus/llgo/_demo/cppmintf/foo"
+	"github.com/goplus/llgo/c"
+	"github.com/goplus/llgo/c/math"
+)
+
+type Bar struct {
+	foo.Callback
+	a int
+}
+
+func NewBar(a int) *Bar {
+	return &Bar{
+		Callback: foo.Callback{
+			ICalc: foo.ICalc{
+				Vptr: &foo.ICalcVtbl{
+					Calc: c.Func((*Bar).sqrt),
+				},
+			},
+			IVal: foo.IVal{
+				Vptr: &foo.IValVtbl{
+					Val: c.Func(bar_IVal_getA),
+				},
+			},
+		},
+		a: a,
+	}
+}
+
+func (p *Bar) getA() int {
+	return p.a
+}
+
+func bar_IVal_getA(this c.Pointer) int {
+	const delta = -int(unsafe.Offsetof(foo.Callback{}.IVal))
+	return (*Bar)(c.Advance(this, delta)).getA()
+}
+
+func (p *Bar) sqrt(v float64) float64 {
+	return math.Sqrt(v)
+}
+
+func main() {
+	bar := NewBar(1)
+	foo.F(&bar.Callback)
+}

_demo/cppmintf/foo/bar/bar.cpp

@@ -0,0 +1,17 @@
+#include <stdio.h>
+#define interface struct
+
+interface ICalc {
+	virtual double calc(double v) = 0;
+};
+
+interface IVal {
+	virtual int val() = 0;
+};
+
+class Callback : public ICalc, public IVal {
+};
+
+extern "C" void f(Callback* cb) {
+	printf("val: %d\ncalc(2): %lf\n", cb->val(), cb->calc(2));
+}

_demo/cppmintf/foo/foo.go

@@ -0,0 +1,42 @@
+package foo
+
+import (
+	"unsafe"
+)
+
+const (
+	LLGoFiles   = "bar/bar.cpp"
+	LLGoPackage = "link"
+)
+
+// -----------------------------------------------------------------------------
+
+type ICalc struct {
+	Vptr *ICalcVtbl
+}
+
+type ICalcVtbl struct {
+	Calc unsafe.Pointer
+}
+
+// -----------------------------------------------------------------------------
+
+type IVal struct {
+	Vptr *IValVtbl
+}
+
+type IValVtbl struct {
+	Val unsafe.Pointer
+}
+
+// -----------------------------------------------------------------------------
+
+type Callback struct {
+	ICalc
+	IVal
+}
+
+//go:linkname F C.f
+func F(cb *Callback)
+
+// -----------------------------------------------------------------------------