为什么在初始化一个函数指针数组时有一个“警告”？

ring-buffer.c:57:19: warning: assignment from incompatible pointer type [enabled by default]
RBufP->rbfunc[0] = &RBufPush;
                 ^

但邻里的确定：

/*typedef for func pointer*/
typedef RBRetCod_t (*RBFunc)();

/*RBufP*/
typedef struct {
    RBufSiz_t size; /*size and mask*/
    RBufDat_t rbufdat;
    RBufPoint_t head,tail;
    RBFunc rbfunc[3]; /*announce of function pointers array*/
} RBuf_t;
RBuf_t *RBufP;
...

/*init for func pointers array*/
RBufP->rbfunc[2] = &RBufDel; /*it is ok*/
RBufP->rbfunc[1] = &RBufPull; /*it is ok*/
RBufP->rbfunc[0] = &RBufPush; /*it is bad,why???*/

...

/*body of the functions*/
RBRetCod_t RBufPull(unsigned char *dat)
{
        return RBSUCC;
}
RBRetCod_t RBufDel(void)
{
        return RBSUCC;
}
RBRetCod_t RBufPush(unsigned char dat)
{
        return RBSUCC;
}

请告诉我为什么在这一行发生警告：RBufP-> rbfunc [0] =& RBufPush,但在相邻的行不存在？