strcoll: Remove incorrect STRDIFF-based optimization (Bug 18589).

The optimization introduced in commit
f13c2a8dff2329c6692a80176262ceaaf8a6f74e, causes regressions in
sorting for languages that have digraphs that change sort order, like
cs_CZ which sorts ch between h and i.

My analysis shows the fast-forwarding optimization in STRCOLL advances
through a digraph while possibly stopping in the middle which results
in a subsequent skipping of the digraph and incorrect sorting. The
optimization is incorrect as implemented and because of that I'm
removing it for 2.23, and I will also commit this fix for 2.22 where
it was originally introduced.

This patch reverts the optimization, introduces a new bug-strcoll2.c
regression test that tests both cs_CZ.UTF-8 and da_DK.ISO-8859-1 and
ensures they sort one digraph each correctly. The optimization can't be
applied without regressing this test.

Checked on x86_64, bug-strcoll2.c fails without this patch and passes
after. This will also get a fix on 2.22 which has the same bug.

10 files changed, 116 insertions, 67 deletions

diff --git a/ChangeLog b/ChangeLog
index 501fa2d..f2dcaed 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2015-10-08  Carlos O'Donell  <carlos@redhat.com>
+
+	[BZ #18589]
+	* string/bug-strcoll2.c: New file.
+	* locale/categories.def: Revert commit
+	f13c2a8dff2329c6692a80176262ceaaf8a6f74e.
+	* locale/langinfo.h: Likewise.
+	* locale/localeinfo.h: Likewise.
+	* locale/C-collate.c: Likewise.
+	* programs/ld-collate.c (collate_output): Likewise.
+	* string/strcoll_l.c (STRDIFF): Likewise.
+	(STRCOLL): Likewise.
+	* wcsmbs/wcscoll_l.c: Likewise.
+
 2015-10-08  Joseph Myers  <joseph@codesourcery.com>
 
 	* math/libm-test.inc (lround_test_data): Do not expect the absence
diff --git a/NEWS b/NEWS
index a3d0ea9..af70dc5 100644
--- a/NEWS
+++ b/NEWS
@@ -13,13 +13,13 @@ Version 2.23
   15384, 15786, 15918, 16141, 16296, 16347, 16415, 16517, 16519, 16520,
   16521, 16620, 16734, 16973, 16985, 17118, 17243, 17244, 17250, 17441,
   17787, 17886, 17887, 17905, 18084, 18086, 18240, 18265, 18370, 18421,
-  18480, 18525, 18595, 18610, 18618, 18647, 18661, 18674, 18675, 18681,
-  18724, 18757, 18778, 18781, 18787, 18789, 18790, 18795, 18796, 18803,
-  18820, 18823, 18824, 18825, 18857, 18863, 18870, 18872, 18873, 18875,
-  18887, 18921, 18951, 18952, 18956, 18961, 18966, 18967, 18969, 18970,
-  18977, 18980, 18981, 18985, 19003, 19012, 19016, 19018, 19032, 19046,
-  19049, 19050, 19059, 19071, 19076, 19077, 19078, 19079, 19085, 19086,
-  19088.
+  18480, 18525, 18595, 18589, 18610, 18618, 18647, 18661, 18674, 18675,
+  18681, 18724, 18757, 18778, 18781, 18787, 18789, 18790, 18795, 18796,
+  18803, 18820, 18823, 18824, 18825, 18857, 18863, 18870, 18872, 18873,
+  18875, 18887, 18921, 18951, 18952, 18956, 18961, 18966, 18967, 18969,
+  18970, 18977, 18980, 18981, 18985, 19003, 19012, 19016, 19018, 19032,
+  19046, 19049, 19050, 19059, 19071, 19076, 19077, 19078, 19079, 19085,
+  19086, 19088.
 
 * The obsolete header <regexp.h> has been removed.  Programs that require
   this header must be updated to use <regex.h> instead.
diff --git a/locale/C-collate.c b/locale/C-collate.c
index d7f3c55..06dfdfa 100644
--- a/locale/C-collate.c
+++ b/locale/C-collate.c
@@ -144,8 +144,6 @@ const struct __locale_data _nl_C_LC_COLLATE attribute_hidden =
     /* _NL_COLLATE_COLLSEQWC */
     { .string = (const char *) collseqwc },
     /* _NL_COLLATE_CODESET */
-    { .string = _nl_C_codeset },
-    /* _NL_COLLATE_ENCODING_TYPE */
-    { .word = __cet_8bit }
+    { .string = _nl_C_codeset }
   }
 };
diff --git a/locale/categories.def b/locale/categories.def
index 045489d..a8dda53 100644
--- a/locale/categories.def
+++ b/locale/categories.def
@@ -58,7 +58,6 @@ DEFINE_CATEGORY
   DEFINE_ELEMENT (_NL_COLLATE_COLLSEQMB,        "collate-collseqmb",        std, wstring)
   DEFINE_ELEMENT (_NL_COLLATE_COLLSEQWC,        "collate-collseqwc",        std, wstring)
   DEFINE_ELEMENT (_NL_COLLATE_CODESET,		"collate-codeset",	    std, string)
-  DEFINE_ELEMENT (_NL_COLLATE_ENCODING_TYPE,   "collate-encoding-type",    std, word)
   ), NO_POSTLOAD)
 
 
diff --git a/locale/langinfo.h b/locale/langinfo.h
index ffc5c7f..a565d9d 100644
--- a/locale/langinfo.h
+++ b/locale/langinfo.h
@@ -255,7 +255,6 @@ enum
   _NL_COLLATE_COLLSEQMB,
   _NL_COLLATE_COLLSEQWC,
   _NL_COLLATE_CODESET,
-  _NL_COLLATE_ENCODING_TYPE,
   _NL_NUM_LC_COLLATE,
 
   /* LC_CTYPE category: character classification.
diff --git a/locale/localeinfo.h b/locale/localeinfo.h
index 434b839..789da44 100644
--- a/locale/localeinfo.h
+++ b/locale/localeinfo.h
@@ -110,14 +110,6 @@ enum coll_sort_rule
   sort_mask
 };
 
-/* Collation encoding type.  */
-enum collation_encoding_type
-{
-  __cet_other,
-  __cet_8bit,
-  __cet_utf8
-};
-
 /* We can map the types of the entries into a few categories.  */
 enum value_type
 {
diff --git a/locale/programs/ld-collate.c b/locale/programs/ld-collate.c
index a39a94f..dc0fe30 100644
--- a/locale/programs/ld-collate.c
+++ b/locale/programs/ld-collate.c
@@ -32,7 +32,6 @@
 #include "linereader.h"
 #include "locfile.h"
 #include "elem-hash.h"
-#include "../localeinfo.h"
 
 /* Uncomment the following line in the production version.  */
 /* #define NDEBUG 1 */
@@ -2131,8 +2130,6 @@ collate_output (struct localedef_t *locale, const struct charmap_t *charmap,
 	  /* The words have to be handled specially.  */
 	  if (idx == _NL_ITEM_INDEX (_NL_COLLATE_SYMB_HASH_SIZEMB))
 	    add_locale_uint32 (&file, 0);
-	  else if (idx == _NL_ITEM_INDEX (_NL_COLLATE_ENCODING_TYPE))
-	    add_locale_uint32 (&file, __cet_other);
 	  else
 	    add_locale_empty (&file);
 	}
@@ -2496,12 +2493,6 @@ collate_output (struct localedef_t *locale, const struct charmap_t *charmap,
   add_locale_raw_data (&file, collate->mbseqorder, 256);
   add_locale_collseq_table (&file, &collate->wcseqorder);
   add_locale_string (&file, charmap->code_set_name);
-  if (strcmp (charmap->code_set_name, "UTF-8") == 0)
-    add_locale_uint32 (&file, __cet_utf8);
-  else if (charmap->mb_cur_max == 1)
-    add_locale_uint32 (&file, __cet_8bit);
-  else
-    add_locale_uint32 (&file, __cet_other);
   write_locale_data (output_path, LC_COLLATE, "LC_COLLATE", &file);
 
   obstack_free (&weightpool, NULL);
diff --git a/string/bug-strcoll2.c b/string/bug-strcoll2.c
new file mode 100644
index 0000000..5ce2f94
--- /dev/null
+++ b/string/bug-strcoll2.c
@@ -0,0 +1,93 @@
+/* Bug 18589: sort-test.sh fails at random.
+   Copyright (C) 1998-2015 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <stdio.h>
+#include <string.h>
+#include <locale.h>
+
+/* An incorrect strcoll optimization resulted in incorrect
+   results from strcoll for cs_CZ and da_DK.  */
+
+int
+test_cs_CZ (void)
+{
+  const char t1[] = "config";
+  const char t2[] = "choose";
+  if (setlocale (LC_ALL, "cs_CZ.UTF-8") == NULL)
+    {
+      perror ("setlocale");
+      return 1;
+    }
+  /* In Czech the digraph ch sorts after c, therefore we expect
+     config to sort before choose.  */
+  int a = strcoll (t1, t2);
+  int b = strcoll (t2, t1);
+  printf ("strcoll (\"%s\", \"%s\") = %d\n", t1, t2, a);
+  printf ("strcoll (\"%s\", \"%s\") = %d\n", t2, t1, b);
+  if (a < 0 && b > 0)
+    {
+      puts ("PASS: config < choose");
+      return 0;
+    }
+  else
+    {
+      puts ("FAIL: Wrong sorting in cz_CZ.UTF-8.");
+      return 1;
+    }
+}
+
+int
+test_da_DK (void)
+{
+  const char t1[] = "AS";
+  const char t2[] = "AA";
+  if (setlocale (LC_ALL, "da_DK.ISO-8859-1") == NULL)
+    {
+      perror ("setlocale");
+      return 1;
+    }
+  /* AA should be treated as the last letter of the Danish alphabet,
+     hence sorting after AS.  */
+  int a = strcoll (t1, t2);
+  int b = strcoll (t2, t1);
+  printf ("strcoll (\"%s\", \"%s\") = %d\n", t1, t2, a);
+  printf ("strcoll (\"%s\", \"%s\") = %d\n", t2, t1, b);
+  if (a < 0 && b > 0)
+    {
+      puts ("PASS: AS < AA");
+      return 0;
+    }
+  else
+    {
+      puts ("FAIL: Wrong sorting in da_DK.ISO-8859-1");
+      return 1;
+    }
+}
+
+static int
+do_test (void)
+{
+  int err = 0;
+  err |= test_cs_CZ ();
+  err |= test_da_DK ();
+  return err;
+}
+
+#define TEST_FUNCTION do_test ()
+#include "../test-skeleton.c"
diff --git a/string/strcoll_l.c b/string/strcoll_l.c
index 8f1225f..35bc0e4 100644
--- a/string/strcoll_l.c
+++ b/string/strcoll_l.c
@@ -29,7 +29,6 @@
 # define STRING_TYPE char
 # define USTRING_TYPE unsigned char
 # define STRCOLL __strcoll_l
-# define STRDIFF __strdiff
 # define STRCMP strcmp
 # define WEIGHT_H "../locale/weight.h"
 # define SUFFIX	MB
@@ -42,20 +41,6 @@
 #include "../locale/localeinfo.h"
 #include WEIGHT_H
 
-#define MASK_UTF8_7BIT  (1 << 7)
-#define MASK_UTF8_START (3 << 6)
-
-size_t
-STRDIFF (const STRING_TYPE *s, const STRING_TYPE *t)
-{
-  size_t n;
-
-  for (n = 0; *s != '\0' && *s++ == *t++; ++n)
-    continue;
-
-  return n;
-}
-
 /* Track status while looking for sequences in a string.  */
 typedef struct
 {
@@ -269,29 +254,9 @@ STRCOLL (const STRING_TYPE *s1, const STRING_TYPE *s2, __locale_t l)
   const USTRING_TYPE *extra;
   const int32_t *indirect;
 
-  /* In case there is no locale specific sort order (C / POSIX).  */
   if (nrules == 0)
     return STRCMP (s1, s2);
 
-  /* Fast forward to the position of the first difference.  Needs to be
-     encoding aware as the byte-by-byte comparison can stop in the middle
-     of a char sequence for multibyte encodings like UTF-8.  */
-  uint_fast32_t encoding =
-    current->values[_NL_ITEM_INDEX (_NL_COLLATE_ENCODING_TYPE)].word;
-  if (encoding != __cet_other)
-    {
-      size_t diff = STRDIFF (s1, s2);
-      if (diff > 0)
-	{
-	  if (encoding == __cet_utf8 && (*(s1 + diff) & MASK_UTF8_7BIT) != 0)
-	    do
-	      diff--;
-	    while (diff > 0 && (*(s1 + diff) & MASK_UTF8_START) != MASK_UTF8_START);
-	  s1 += diff;
-	  s2 += diff;
-	}
-    }
-
   /* Catch empty strings.  */
   if (__glibc_unlikely (*s1 == '\0') || __glibc_unlikely (*s2 == '\0'))
     return (*s1 != '\0') - (*s2 != '\0');
@@ -358,8 +323,7 @@ STRCOLL (const STRING_TYPE *s1, const STRING_TYPE *s2, __locale_t l)
 		     byte-level comparison to ensure that we don't waste time
 		     going through multiple passes for totally equal strings
 		     before proceeding to subsequent passes.  */
-		  if (pass == 0 && encoding == __cet_other &&
-		      STRCMP (s1, s2) == 0)
+		  if (pass == 0 && STRCMP (s1, s2) == 0)
 		    return result;
 		  else
 		    break;
diff --git a/wcsmbs/wcscoll_l.c b/wcsmbs/wcscoll_l.c
index 6d9384a..87f240d 100644
--- a/wcsmbs/wcscoll_l.c
+++ b/wcsmbs/wcscoll_l.c
@@ -23,7 +23,6 @@
 #define STRING_TYPE wchar_t
 #define USTRING_TYPE wint_t
 #define STRCOLL __wcscoll_l
-#define STRDIFF __wcsdiff
 #define STRCMP __wcscmp
 #define WEIGHT_H "../locale/weightwc.h"
 #define SUFFIX	WC