Socket on linux work but not on osx

Question

I'm struggling with an issue, my socket interface for Linux works perfectly, But on osx, I'm not receiving/sending any data, using gdb, I found out that select never set the fd_set, and so my code never read on the socket: Here the select code , which might be in cause:

static inline int   max_fd_plusone(t_list *fds)
{
  int           max;
  t_list        *tmp;
  t_selfd       *fd;

  max = -1;
  tmp = fds;
  while (tmp)
    {
      fd = (t_selfd*)tmp->data;
      max = fd->fd > max ? fd->fd : max;
      tmp = tmp->next;
    }
  return (max + 1);
}

static inline void  set_fdset(t_list *fds, fd_set *setr, fd_set *setw)
{
  t_list        *tmp;
  t_selfd       *fd;

  FD_ZERO(setr);
  FD_ZERO(setw);
  tmp = fds;
  while (tmp)
    {
      fd = (t_selfd*)tmp->data;
      if ((fd->checktype & FDREAD) == FDREAD)
        FD_SET(fd->fd, setr);
      if ((fd->checktype & FDWRITE) == FDWRITE)
        FD_SET(fd->fd, setw);
      tmp = tmp->next;
    }
}

t_selfd     *create_fd(int fd, void *data, int (*call)())
{
  t_selfd   *res;

  if ((res = malloc(1 * sizeof(t_selfd))) == NULL)
    return (NULL);
  res->fd = fd;
  res->etype = 0;
  res->checktype = FDREAD;
  res->data = data;
  res->callback = call;
  res->to_close = 0;
  res->rbuff = create_ring_buffer(BUFSIZ * 2);
  res->wbuff = create_ring_buffer(BUFSIZ * 2);
  if (!res->rbuff || !res->wbuff)
    {
      destroy_ring_buffer(res->rbuff);
      destroy_ring_buffer(res->wbuff);
      free(res);
      return (NULL);
    }
  return (res);
}

void        do_select(t_list *fds, struct timeval *tv, void *global_arg)
{
  fd_set    setr;
  fd_set    setw;
  t_list    *tmp;
  t_list    *nexttmp;
  t_selfd   *fd;

  nexttmp = NULL;
  set_fdset(fds, &setr, &setw);
  if ((select(max_fd_plusone(fds), &setr, &setw, NULL, tv) == -1))
    return ;
  tmp = fds;
  nexttmp = tmp->next;
  while (tmp)
    {
      fd = (t_selfd*)tmp->data;
      fd->etype = (FD_ISSET(fd->fd, &setr)) * FDREAD
                  + (FD_ISSET(fd->fd, &setw)) * FDWRITE;
      fd->checktype = 0;
      fd->callback(fd, global_arg);
      tmp = nexttmp;
      nexttmp = tmp ? tmp->next : NULL;
    }
}

Answer 1

This looks suspicious:

  fd->etype = (FD_ISSET(fd->fd, &setr)) * FDREAD
              + (FD_ISSET(fd->fd, &setw)) * FDWRITE;

You're assuming that FD_ISSET returns a specific value (most likely 1) while it's only documented to return non-zero or zero. This will definitely be different between operating systems.

Linux returns a normalized boolean here (0 or 1) while MacOS doesn't.

NB since it seems that you're designing some library, it might be a good idea to use a more modern interface like poll instead of select . Select performs badly and can fail completely when you get too many file descriptors.