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

[Carlos O'Donell <carlos@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=82292c99b2b68504e0b09b19a339d0232c2e1eaa

commit 82292c99b2b68504e0b09b19a339d0232c2e1eaa
Author: Hanataka Shinya <hanataka.shinya@gmail.com>
Date:   Wed Feb 17 23:00:48 2021 -0500

    LC_COLLATE: Fix last character ellipsis handling (Bug 22668)
    
    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.
    
    Retested and no regressions on x86_64 and i686.
    
    Co-authored-by: Carlos O'Donell <carlos@redhat.com>

Diff:
---
 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;
 }