我正在尝试将一个成员函数传递给应该被视为回调的libevent 。
#include <event.h>
class A
{
public:
void eventcb(evutil_socket_t fd, short events, void *ctx) { }
};
static void global_eventcb(evutil_socket_t fd, short events, void *ctx) { }
typedef void (A::*mthd)(evutil_socket_t, short, void*);
int main(void)
{
struct event_base *evbase = event_base_new();
mthd eventcb = &A::eventcb;
A *instance = new A;
(instance->*eventcb)(NULL, 0, NULL);
struct event *timer1 = evtimer_new(evbase, global_eventcb, NULL);
struct event *timer2 = evtimer_new(evbase, (instance->*eventcb), NULL);
return 0;
}
我可以成功地在 A 类中创建一个指向eventcb的方法指针,并在 A 的实例上调用它(第 20 行)。
此外,在第 22 行传递一个全局函数(就像在 C 中所做的那样)也可以正常工作。
但是,在第 23 行,我尝试将我的方法指针传递给libevent,当我编译它时,我收到以下错误(使用clang编译器)
example.cpp:23:25: error: no matching function for call to 'event_new'
struct event *timer2 = evtimer_new(evbase, (instance->*eventcb), NULL);
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from example.cpp:1:
In file included from /usr/local/include/event.h:71:
/usr/local/include/event2/event.h:749:40: note: instantiated from:
#define evtimer_new(b, cb, arg) event_new((b), -1, 0, (cb), (arg))
^~~~~~~~~
/usr/local/include/event2/event.h:833:15: note: candidate function not viable: no know conversion from '<bound member function type>' to 'event_callback_fn'
(aka 'void (*)(int, short, void *)') for 4th argument
struct event *event_new(struct event_base *, evutil_socket_t, short, event_callback_fn, void *);
^
1 error generated.
我究竟做错了什么?