c10-16 sigsuspend --set global variable --apue

#include "apue.h"

volatile sig_atomic_t quitflag ; /* set nonzero by signal handler */
static void
sig_int(int signo)
{
        printf("\n interrupt ");
}
static void
sig_quit(int signo)
{
        quitflag = 1;  /* set flag for main loop */

}
int main(void )
{
    sigset_t newmask,oldmask,zeromask;

    if (signal(SIGINT,sig_int) == SIG_ERR)
        err_sys("signal(SIGINT) error");
    if (signal(SIGQUIT,sig_quit) == SIG_ERR)
        err_sys("signal(sigquit) error");
    sigemptyset(&zeromask);
    sigemptyset(&newmask);
    sigaddset(&newmask,SIGQUIT);

    /*
     *block sigquit and save current signal mask
     */
    if (sigprocmask(SIG_BLOCK,&newmask,&oldmask) < 0)
        err_sys("SIGPROCMASK block error");
    while (quitflag == 0)
        sigsuspend(&zeromask);
    /*
     *sigquit has been caught and is now block,do whatever
     */
    quitflag = 0;

    /*
     * reset signal mask which unblock sigquit
     */
    if (sigprocmask(SIG_SETMASK,&oldmask,NULL) < 0)
        err_sys("SIG_SETMASK,ERROR");
    exit(0);
}

#include "apue.h"
/* reliable version of signal() ,using posix signaction()*/
Sigfunc *
signal(int signo,Sigfunc * func)
{
    struct sigaction act,oact;

    act.sa_handler = func;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
    if ( signo  == SIGALRM){
    #ifdef SA_INTERRUPT
        act.sa_flags |=  SA_INTERRUPT;
    #endif
    } else{
    #ifdef  SA_RESTART
        act.sa_flags |= SA_RESTART;
    #endif
    }
    if (sigaction(signo,&act,&oact) < 0)
        return(SIG_ERR);
    return(oact.sa_handler);
}

output of program :

ubuntu@ubuntu-virtual-machine:~/Desktop/apue$ ./c10-16
^C
^C interrupt
^C interrupt
^C interrupt
^C interrupt
^C interrupt
^C interrupt
^C interrupt
^C interrupt
^\ interrupt

我的结果和书上面的不一致，第一次的中断信号被丢失，不知道什么原因？

我试过多次都是这个结果，期待高手解决，signal程序是c10-12