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[PATCH] Keep expected behaviour for [a-z] and [A-z] (Bug 23393).

In commit 9479b6d5e08eacce06c6ab60abc9b2f4eb8b71e4 we updated all of
the collation data to harmonize with the new version of ISO 14651
which is derived from Unicode 9.0.0.  This collation update brought
with it some changes to locales which were not desirable by some
users, in particular it altered the meaning of the
locale-dependent-range regular expression, namely [a-z] and [A-Z], and
for en_US it caused uppercase letters to be matched by [a-z] for the
first time.  The matching of uppercase letters by [a-z] is something
which is already known to users of other locales which have this
property, but this change could cause significant problems to en_US
and other similar locales that had never had this change before.
Whether this behaviour is desirable or not is contentious and GNU Awk
has this to say on the topic:
While the POSIX standard also has this further to say: "RE Bracket
"The current standard leaves unspecified the behavior of a range
expression outside the POSIX locale. ... As noted above, efforts were
made to resolve the differences, but no solution has been found that
would be specific enough to allow for portable software while not
invalidating existing implementations."
In glibc we implement the requirement of ISO POSIX-2:1993 and use
collation element order (CEO) to construct the range expression, the
API internally is __collseq_table_lookup().  The fact that we use CEO
and also have 4-level weights on each collation rule means that we can
in practice reorder the collation rules in iso14651_t1_common (the new
data) to provide consistent range expression resolution *and* the
weights should maintain the expected total order.  Therefore this
patch does three things:

* Reorder the collation rules for the LATIN script in
  iso14651_t1_common to deinterlace uppercase and lowercase letters in
  the collation element orders.

* Adds new test data for which exercises
  strcoll* and strxfrm* and ensures the ISO 14651 collation remains.

* Add back tests to tst-fnmatch.input and tst-regexloc.c which
  exercise that [a-z] does not match A or Z.

The reordering of the ISO 14651 data is done in an entirely mechanical
fashion using the following program attached to the bug:

It is up for discussion if the iso14651_t1_common data should be
refined further to have 3 very tight collation element ranges that
include only a-z, A-Z, and 0-9, which would implement the solution
sought after in:

No regressions on x86_64.
Verified that removal of the iso14651_t1_common change causes tst-fnmatch
to regress with:
422: fnmatch ("[a-z]", "A", 0) = 0 (FAIL, expected FNM_NOMATCH) ***
425: fnmatch ("[A-Z]", "z", 0) = 0 (FAIL, expected FNM_NOMATCH) ***
 ChangeLog                             |   11 +
 localedata/Makefile                   |    1 +
 localedata/             | 2159 +++++++++++++++++++++++++++++++++
 localedata/locales/iso14651_t1_common | 1928 ++++++++++++++---------------
 posix/tst-fnmatch.input               |  125 +-
 posix/tst-regexloc.c                  |    8 +-
 6 files changed, 3224 insertions(+), 1008 deletions(-)
 create mode 100644 localedata/

I'm suggesting this change immediately for 2.28 to avoid further
problems with users expectations and sorting with [a-z] and [A-Z] until
a clearer consensus can be reached for a final solution.

File attached as .tar.gz to get past spam detectors. There is a lot
of UTF-8 data in en_US.UTF-8 (every possible character in the LATIN
set that can be sorted with the existing test case infrastructure).


Attachment: swbz23393.tar.gz
Description: application/gzip

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