Re: unsafe use of dirfd in fts.c, getcwd.c, glob.c?

[Bruno Haible]

Hi Paul,

> Can dirfd really return -1 on real platforms, when its argument is a valid
> open directory stream?  POSIX allows that behavior, but I don't know
> of any implementations that do it.

Nothing of this sort is known for Unix platforms, but
gnulib/doc/posix-functions/dirfd.texi mentions that this problem exists on
mingw:

  Portability problems not fixed by Gnulib:
  @itemize
  @item
  This function always fails on some platforms:
  mingw.
  @end itemize

Also, see the comment in lib/fchdir.c: "FIXME - make dirfd possible on mingw".

So, for modules that attempt portability to mingw - and 'getcwd' and 'glob'
are certainly in this group - you shouldn't use dirfd for essential purposes,
but rather use file names and 'DIR *' pointers.

Bruno