Re: [PATCH] Prefer readlink to lstat+S_ISLNK when easy

[Bruno Haible via Gnulib discussion list]

Paul Eggert wrote:
> diff --git a/lib/unlinkat.c b/lib/unlinkat.c
> index 7fb0371996..6873ba558d 100644
> --- a/lib/unlinkat.c
> +++ b/lib/unlinkat.c
> @@ -71,8 +71,8 @@ rpl_unlinkat (int fd, char const *name, int flag)
>            memcpy (short_name, name, len);
>            while (len && ISSLASH (short_name[len - 1]))
>              short_name[--len] = '\0';
> -          if (len && (fstatat (fd, short_name, &st, AT_SYMLINK_NOFOLLOW)
> -                      || S_ISLNK (st.st_mode)))
> +          if (len && (readlinkat (fd, short_name, linkbuf, 1) < 0
> +                      || errno == EINVAL))
>              {
>                free (short_name);
>                errno = EPERM;

This looks wrong. Copying the logic from lib/unlink.c, I would expect these
two lines to be

          if (len && ! (readlinkat (fd, short_name, linkbuf, 1) < 0
                        && errno == EINVAL))

or — if you want —

          if (len && (readlinkat (fd, short_name, linkbuf, 1) >= 0
                      || errno != EINVAL))

Bruno