Re: [PATCH] LC_COLLATE: Fix last character ellipsis handling (Bug 22668)

[Florian Weimer via Libc-alpha <libc-alpha@sourceware.org>]

* Carlos O'Donell via Libc-alpha:

> From: Hanataka Shinya <hanataka.shinya@gmail.com>
>
> During ellipsis processing the collation cursor was not correctly
> moved to the end of the ellipsis after processing.
>
> The code inserted the new entry after the cursor, but before the
> real end of the ellipsis:
>                                 [cursor]
> ... element_t <-> element_t <-> element_t <-> element_t
>                   "<U0000>"     "<U0001>"     "<U007F>"
>                   startp                      endp
>
> At the end of the function we have:
>
>                   [cursor]
> ... element_t <-> element_t <-> element_t
>                   "<U007E>"     "<U007F>"
>                                 endp
>
> The cursor should be pointing at endp, the last element in the
> doubly-linked list, otherwise when execution returns to the
> caller we will start inserting the next line after <U007E>.
>
> Subsequent operations end up unlinking the ellipsis end entry or
> just leaving it in the list dangling from the end.  This kind of
> dangling is immediately visible in C.UTF-8 with the following
> sorting from strcoll:
> <U0010FFFF>
> <U0000FFFF>
> <U000007FF>
> <U0000007F>
>
> With the cursor correctly adjusted the end entry is correctly given
> the right location and thus the right weight.
>
> No regressions on x86_64 and i686.
>
> Co-authored-by: Carlos O'Donell <carlos@redhat.com>
> ---
>  locale/programs/ld-collate.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/locale/programs/ld-collate.c b/locale/programs/ld-collate.c
> index 0af21e05e2..b6406b775d 100644
> --- a/locale/programs/ld-collate.c
> +++ b/locale/programs/ld-collate.c
> @@ -1483,6 +1483,9 @@ order for `%.*s' already defined at %s:%Zu"),
>  	    }
>  	}
>      }
> +  /* Move the cursor to the last entry in the ellipsis.
> +     Subsequent operations need to start from the last entry.  */
> +  collate->cursor = endp;
>  }

I do not completely understand the code, but I double-checked a few
things, and this looks consistent.  So I guess it's okay to check this
in.

Thanks,
Florian