void(*func)(int) is a pointer to a function whose return value is void and the parameter is int
Is a function pointer
Specific understanding http://zhidao.baidu.com/link?url=5GpEN7wPUhDlk_m-3drRHV9bGxv53tj818vtd1GIsyaVfyY1mdsFZfP6_2M_DNAfTQrh0qxMo_wXhK1CjIEPJK