错误:在gcc中‘wstat’的类型冲突

Question

我从这个文档中复制了这个程序：https://docs.oracle.com/cd/E19455-01/806-4750/signals-7/index.html

#include <stdio.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/resource.h>

void proc_exit()
{
        int wstat;
        union wait wstat;
        pid_t   pid;

        while (TRUE) {
            pid = wait3 (&wstat, WNOHANG, (struct rusage *)NULL );
            if (pid == 0)
                return;
            else if (pid == -1)
                return;
            else
                printf ("Return code: %d\n", wstat.w_retcode);
        }
}
main ()
{
        signal (SIGCHLD, proc_exit);
        switch (fork()) {
            case -1:
                perror ("main: fork");
                exit (0);
            case 0:
                printf ("I'm alive (temporarily)\n");
                exit (rand());
            default:
                pause();
        }
}

当我运行gcc main.c时，我得到这个错误：

main.c: In function ‘proc_exit’:
main.c:9:13: error: conflicting types for ‘wstat’
  union wait wstat;
             ^~~~~
main.c:8:6: note: previous declaration of ‘wstat’ was here
  int wstat;
      ^~~~~
main.c:9:13: error: storage size of ‘wstat’ isn’t known
  union wait wstat;
             ^~~~~
main.c:12:9: error: ‘TRUE’ undeclared (first use in this function)
  while (TRUE) {

据我所知，wstat被定义了两次。这是否意味着文档是不正确的？以及如何修复它？

Answer 1

是啊，那个密码就是坏了。我不知道union wait wstat;的意图是什么。可能是文档作者的一些复制粘贴错误。谁知道呢。一般来说，代码写得很差，IMO。

无论如何，以下是代码实际要做的事情：

int wstat;
pid_t pid;

while (1) {
    pid = wait3(&wstat, WNOHANG, NULL);
    if (pid == 0 || pid == -1)
        return;
    printf("Return code: %d\n", wstat);
}