C: "No such file or directory"on sem_open() with O_CREAT 和正确的信号量名称

Question

我正在尝试在 C 中的初始化函数中创建信号量:

void sem_init(int size, sem_t** sem1, sem_t** sem2) {
  char* semname1 = "/somename";
  char* semname2 = "/someothername";

  errno = 0;
  *sem1 = sem_open(semname1, O_CREAT, S_IRUSR|S_IWUSR, 0);
  printf(strerror(errno));

  errno = 0;
  *sem2 = sem_open(semname2, O_CREAT, S_IRUSR|S_IWUSR, size);
  printf(strerror(errno));
}

但即使我设置了 O_CREAT 标志并且名称格式正确，我总是得到“没有这样的文件或目录”作为输出。信号量创建于 /dev/shm/...

我看不出有任何明显的错误发生原因。请帮助我解决我做错了什么。

Answer 1

正如对 OP 问题的评论所指出的，errno 中使用了不正确的值。建议:

void sem_init(int size, sem_t** sem1, sem_t** sem2) {
    char* semname1 = "/somename";
    char* semname2 = "/someothername";
    sem_t local_sem1;
    sem_t local_sem2;

    if( (local_sem1 = sem_open(semname1, O_CREAT, S_IRUSR|S_IWUSR, 0) ) == SEM_FAILED )
    {
        perror( "sem_open for sem1 failed" );
        exit( EXIT_FAILURE );
    }

    *sem1 = local_sem1;

    if( (local_sem2 = sem_open(semname2, O_CREAT, S_IRUSR|S_IWUSR, 0) ) == SEM_FAILED )
    {
        perror( "sem_open doe awm2 failed" );
        exit( EXIT_FAILURE );
    }

    *sem2 = local_sem2;
}