// code exapmle 1
1   package main
  1
  2 /*
  3 #include <stdio.h>
  4
  5 void nothing(void *x) {
  6 }
  7 */
  8 import "C"
  9 import (
 10         "unsafe"
 11 )
 12
 13 type foo struct {
 14         p *int
 15         a int
 16 }
 17
 18 func main() {
 19         f := &foo{}
 20         b := 10
 21         f.p = &b
 22         f.a = b
 23         C.nothing(unsafe.Pointer(&f.a))
 24 }

// code exapmle 2
1   package main
  1
  2 /*
  3 #include <stdio.h>
  4
  5 void nothing(void *x) {
  6 }
  7 */
  8 import "C"
  9 import (
 10         "unsafe"
 11 )
 12
 13 type foo struct {
 14         p *int
 15         a *int
 16 }
 17
 18 func main() {
 19         f := &foo{}
 20         b := 10
 21         f.p = &b
 22         f.a = &b
 23         C.nothing(unsafe.Pointer(f.a))
 24 }

panic: runtime error: cgo argument has Go pointer to Go pointer

goroutine 1 [running]:
main.main.func1(0xc420010038)
        /root/go/src/github.com/winglq/test/pointer/main.go:23 +0x96
main.main()
        /root/go/src/github.com/winglq/test/pointer/main.go:24 +0x7f