bug#11453: `ls` in coreutils-8.17 incorrectly shows broken symlinks in /

[Jim Meyering]

Jim Meyering wrote:

> Mike Frysinger wrote:
>> coreutils-8.16 works fine (confirmed), and i don't recall seeing this bug
>> before, so looks like a regression with 8.17
>>
>> easy to show:
>> $ sudo ln -s dev /foo
>> $ ls --color=auto /
>> ... foo wrongly shows up in blinky text indicating it's a broken symlink ...
>> $ ls --color=auto /.
>> ... foo correctly shows up with normal coloring indicating it's a symlink ...
>> $ cd / ; ls --color=auto
>> ... foo correctly shows up with normal coloring indicating it's a symlink ...
>> -mike
>
> Rats.
> That bug was introduced by my clean-up.
> Here's the probable fix.
> Thanks for the report!
>
> diff --git a/src/ls.c b/src/ls.c
> index 397e4ea..b548382 100644
> --- a/src/ls.c
> +++ b/src/ls.c
> @@ -3213,7 +3213,8 @@ make_link_name (char const *name, char const *linkname)
>      return xstrdup (linkname);
>
>    char *p = xmalloc (prefix_len + 1 + strlen (linkname) + 1);
> -  stpcpy (stpncpy (p, name, prefix_len + 1), linkname);
> +  bool prefix_ends_in_slash = ISSLASH (name[prefix_len - 1]);
> +  stpcpy (stpncpy (p, name, prefix_len + !prefix_ends_in_slash), linkname);

While the above fixes your problem, it fails to
solve the problem when running e.g.,

  mkdir -p d/b; (cd d; ln -s b link); ls --color d

(i.e., with a single-component base directory name and a symlink
to a relative name it would still color "link" as if it were dangling)

This fixes both:

diff --git a/src/ls.c b/src/ls.c
index 397e4ea..93a3338 100644
--- a/src/ls.c
+++ b/src/ls.c
@@ -3206,14 +3206,9 @@ make_link_name (char const *name, char const *linkname)
   if (IS_ABSOLUTE_FILE_NAME (linkname))
     return xstrdup (linkname);

-  /* The link is to a relative name.  Prepend any leading directory
-     in 'name' to the link name.  */
-  size_t prefix_len = dir_len (name);
-  if (prefix_len == 0)
-    return xstrdup (linkname);
-
-  char *p = xmalloc (prefix_len + 1 + strlen (linkname) + 1);
-  stpcpy (stpncpy (p, name, prefix_len + 1), linkname);
+  char *d = dir_name (name);
+  char *p = file_name_concat (d, linkname, NULL);
+  free (d);
   return p;
 }