[linux]signal函数不起作用

#include "apue.h"

#include <sys/wait.h>

static void sig_int(int); /* our signal-catching function */

int main(int argc, char *argv[])
{
    printf("uid = %d, gid = %d\n", getuid(), getgid());

    char buf[MAXLINE]; /* from apue.h */
    pid_t pid;
    int status;

    // register the signal handler
    if ( signal(SIGINT, sig_int) == SIG_ERR)
        err_sys("signal error");

    printf("%% "); /* print prompt (printf requires %% to print %) */
    while (fgets(buf, MAXLINE, stdin) != NULL) {
        if (buf[strlen(buf) - ] == '\n')
            buf[strlen(buf) - ] = ; /* replace newline with null */
        if ((pid = fork()) < ) {
            err_sys("fork error");
        } else if (pid == ) { /* child */
            execlp(buf, buf, (char *));
            err_ret("couldn't execute: %s", buf);
            exit();
        }
        /* parent */
        if ((pid = waitpid(pid, &status, )) < )
            err_sys("waitpid error");
        printf("Last pid: %ld\n", (long)pid);
        printf("%% ");
    }

    exit();
}

void sig_int(int signo)
{
    printf("sig_int: interrupt\n%% ");
    exit(); // I add this line to exit the program through CTRL+C (SIGINT), CTRL+D is to terminate the program
}

代码来自APUE Figure1.10

我编译之后用gdb调试，发现sig_int始终不会被调用

最后终于发现问题是因为编译选项加了-g，在调试状态下signal机制貌似被禁用了