ch2: 增加一个例子

examples/ch2-xx/return-go-ptr/main.go

@@ -0,0 +1,28 @@
+// Copyright © 2017 ChaiShushan <chaishushan{AT}gmail.com>.
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+
+package main
+
+// go run x.go
+// GODEBUG=cgocheck=0 go run x.go
+
+// panic: runtime error: cgo result has Go pointer
+
+/*
+extern int* getGoPtr();
+
+static void Main() {
+	int* p = getGoPtr();
+	*p = 42;
+}
+*/
+import "C"
+
+func main() {
+	C.Main()
+}
+
+//export getGoPtr
+func getGoPtr() *C.int {
+	return new(C.int)
+}