Adhemerval Zanella wrote:
> +/* Any distinct values will do here.
> +   Undef any existing macros out of the way.  */
> +#ifndef DT_UNKNOWN
> +# define DT_UNKNOWN 0
> +#endif
> +#ifndef DT_DIR
> +# define DT_DIR 1
> +#endif
> +#ifndef DT_LNK
> +# define DT_LNK 2
> +#endif

The comment here does not match the code, as nothing is being undeffed. Instead 
of this change, how about the following?

#if !defined _LIBC && !defined HAVE_STRUCT_DIRENT_D_TYPE
/* Any distinct values will do here.
    Undef any existing macros out of the way.  */
# undef DT_UNKNOWN
# undef DT_DIR
# undef DT_LNK
# define DT_UNKNOWN 0
# define DT_DIR 1
# define DT_LNK 2
#endif

This makes it more clear to the casual reader that this code is for use only 
outside glibc. Also, it's more robust for hopefully only-hypothetical non-glibc 
platforms that define some DT_ symbols but not others, because it guarantees 
their uniqueness in that case. I installed the attached patch into Gnulib, along 
these lines.