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

[Jim Meyering]

Jim Meyering wrote:
> 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

Actually the above is fine after all --
and it uses less memory than the patch below.
I must have been testing something else.

> (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;
>  }