Re: [PATCH] Cygwin: Add /dev/disk/by-label and /dev/disk/by-uuid symlinks

[Corinna Vinschen <corinna-cygwin@cygwin.com>]

On Nov 20 10:40, Corinna Vinschen wrote:
> Hi Christian,
> 
> This puzzles me:
> 
> On Nov 17 21:25, Christian Franke wrote:
> > @@ -610,7 +607,7 @@ get_by_id_table (by_id_entry * &table, fhandler_dev_disk::dev_disk_location loc)
> >    if (!table)
> >      return (errno_set ? -1 : 0);
> >  
> > -  /* Sort by name and remove duplicates. */
> > +  /* Sort by name and mark duplicates. */
> >    qsort (table, table_size, sizeof (*table), by_id_compare_name);
> >    for (unsigned i = 0; i < table_size; i++)
> 
> by_id_compare_name only compars the actual names...
> 
> >      {
> > @@ -619,12 +616,13 @@ get_by_id_table (by_id_entry * &table, fhandler_dev_disk::dev_disk_location loc)
> >  	j++;
> >        if (j == i + 1)
> >  	continue;
> > -      /* Duplicate(s) found, remove all entries with this name. */
> > -      debug_printf ("removing duplicates %d-%d: '%s'", i, j - 1, table[i].name);
> > -      if (j < table_size)
> > -	memmove (table + i, table + j, (table_size - j) * sizeof (*table));
> > -      table_size -= j - i;
> > -      i--;
> > +      /* Duplicate(s) found, append "#N" to all entries.  This never
> 
> ...but the names are identical.  So the *order* within the identically
> named entries depends on qsort's reshuffling of table
> entries.  Which in turn depends on outside factors like number of table
> entries and the ultimate position of the identical entries within the
> ordered table.
> 
> Having said that, I don't see how adding ordinals to the names can be
> unambiguous.  AFAICS, the numbers may change by just adding another
> disk (USB Stick) to the system...

Oops, that's not exactly what I was trying to say, sorry.

The problem is not adding ordinals to the name, AFAICS, the problem is
that the sorting function by_id_compare_name is not up to the task to
make sure the order is unambiguous within the entries of identical name.


Corinna