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

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The optimization introduced in commit
f13c2a8dff, 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.
This commit is contained in:
Carlos O'Donell
2015-10-08 16:34:53 -04:00
parent fd91891a50
commit 87701a58e2
10 changed files with 116 additions and 67 deletions
Download Patch File Download Diff File Expand all files Collapse all files

38
string/strcoll_l.c
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@ -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;