Re: fdopendir: Fix fd leak and test failure on native Windows

[Bruno Haible]

KO Myung-Hun wrote:
> > @@ -78,11 +82,17 @@ _gl_unregister_dirp_fd (int fd)
> >  int
> >  dirfd (DIR *dir_p)
> >  {
> > +#if GNULIB_defined_DIR
> > +  int fd = dir_p->fd_to_close;
> 
> dirfd() allows to take an invalid `dir_p' ?

No; this must be a misunderstanding.

dirfd is specified at
https://pubs.opengroup.org/onlinepubs/9699919799/functions/dirfd.html
Which says that if "The dirp argument does not refer to a valid directory 
stream"
the function may fail with error EINVAL. It may alternatively simply crash
("the behavior is undefined").

In this code, we have two cases, depending on platforms:
  - If GNULIB_defined_DIR, it means that gnulib has defined or overridden
    the 'DIR' type, to include an 'fd_to_close' field'.
    Currently that's only on native Windows, but I'm suggesting that the same
    code could also be used on kLIBC.
  - Otherwise, gnulib uses either the system-provided dirfd function or macro,
    or does a lookup in dir_p->d_fd or dir_p->dd_fd.

Bruno