linux中的信号结构体

typedef struct siginfo
{
                int si_signo;            /* Signal number.*/
                int si_errno;            /* If non-zero, an errno value associated with this signal, as defined in <errno.h>.*/
                int si_code;             /* Signal code*/
                union
                {
                         int _pad[__SI_PAD_SIZE];
                         struct  /* kill().*/
                         {
                                     __pid_t si_pid;          /* Sending process ID.*/
                                     __uid_t si_uid;          /* Real user ID of sending process.*/
  &n