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revision 89 by nigel, Sat Feb 24 21:41:27 2007 UTC revision 119 by ph10, Mon Mar 12 09:29:45 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4    Version 7.1 05-Mar-07
5    ---------------------
6    
7     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
8        that is more "standard", making use of automake and other autotools. There
9        is some re-arrangement of the files and adjustment of comments consequent
10        on this.
11    
12     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
13        for recursive directory scanning broke on some systems because the files
14        are not scanned in any specific order and on different systems the order
15        was different. A call to "sort" has been inserted into RunGrepTest for the
16        approprate test as a short-term fix. In the longer term there may be an
17        alternative.
18    
19     3. I had an email from Eric Raymond about problems translating some of PCRE's
20        man pages to HTML (despite the fact that I distribute HTML pages, some
21        people do their own conversions for various reasons). The problems
22        concerned the use of low-level troff macros .br and .in. I have therefore
23        removed all such uses from the man pages (some were redundant, some could
24        be replaced by .nf/.fi pairs). The 132html script that I use to generate
25        HTML has been updated to handle .nf/.fi and to complain if it encounters
26        .br or .in.
27    
28     4. Updated comments in configure.ac that get placed in config.h.in and also
29        arranged for config.h to be included in the distribution, with the name
30        config.h.generic, for the benefit of those who have to compile without
31        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
32    
33     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
34        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
35        makevp.bat for the current PCRE, using the additional files !compile.txt,
36        !linklib.txt, and pcregexp.pas.
37    
38     6. A Windows user reported a minor discrepancy with test 2, which turned out
39        to be caused by a trailing space on an input line that had got lost in his
40        copy. The trailing space was an accident, so I've just removed it.
41    
42     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
43        that is needed.
44    
45     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
46        as "const" (a) because they are and (b) because it helps the PHP
47        maintainers who have recently made a script to detect big data structures
48        in the php code that should be moved to the .rodata section. I remembered
49        to update Builducptable as well, so it won't revert if ucptable.h is ever
50        re-created.
51    
52     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
53        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
54        order to be able to cut out the UTF-8 tables in the latter when UTF-8
55        support is not required. This saves 1.5-2K of code, which is important in
56        some applications.
57    
58        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
59        so as not to refer to the tables, even though these functions will never be
60        called when UTF-8 support is disabled. Otherwise there are problems with a
61        shared library.
62    
63    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
64    
65        (a) It was defining its arguments as char * instead of void *.
66    
67        (b) It was assuming that all moves were upwards in memory; this was true
68            a long time ago when I wrote it, but is no longer the case.
69    
70        The emulated memove() is provided for those environments that have neither
71        memmove() nor bcopy(). I didn't think anyone used it these days, but that
72        is clearly not the case, as these two bugs were recently reported.
73    
74    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
75        and Detrail to create the HTML documentation, the .txt form of the man
76        pages, and it removes trailing spaces from listed files. It also creates
77        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
78        case, it wraps all the #defines with #ifndefs. This script should be run
79        before "make dist".
80    
81    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
82        with Unicode property support.
83    
84        (a) For a maximizing quantifier, if the two different cases of the
85            character were of different lengths in their UTF-8 codings (there are
86            some cases like this - I found 11), and the matching function had to
87            back up over a mixture of the two cases, it incorrectly assumed they
88            were both the same length.
89    
90        (b) When PCRE was configured to use the heap rather than the stack for
91            recursion during matching, it was not correctly preserving the data for
92            the other case of a UTF-8 character when checking ahead for a match
93            while processing a minimizing repeat. If the check also involved
94            matching a wide character, but failed, corruption could cause an
95            erroneous result when trying to check for a repeat of the original
96            character.
97    
98    13. Some tidying changes to the testing mechanism:
99    
100        (a) The RunTest script now detects the internal link size and whether there
101            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
102            values substituted by "configure". (The RunGrepTest script already did
103            this for UTF-8.) The configure.ac script no longer substitutes the
104            relevant variables.
105    
106        (b) The debugging options /B and /D in pcretest show the compiled bytecode
107            with length and offset values. This means that the output is different
108            for different internal link sizes. Test 2 is skipped for link sizes
109            other than 2 because of this, bypassing the problem. Unfortunately,
110            there was also a test in test 3 (the locale tests) that used /B and
111            failed for link sizes other than 2. Rather than cut the whole test out,
112            I have added a new /Z option to pcretest that replaces the length and
113            offset values with spaces. This is now used to make test 3 independent
114            of link size.
115    
116    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
117        segmentation fault instead of giving the appropriate error message.
118    
119    
120    Version 7.0 19-Dec-06
121    ---------------------
122    
123     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
124        moving to gcc 4.1.1.
125    
126     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
127        sys/time.h, which is documented as needed for this function. It doesn't
128        seem to matter on Linux, but it showed up on some releases of OS X.
129    
130     3. It seems that there are systems where bytes whose values are greater than
131        127 match isprint() in the "C" locale. The "C" locale should be the
132        default when a C program starts up. In most systems, only ASCII printing
133        characters match isprint(). This difference caused the output from pcretest
134        to vary, making some of the tests fail. I have changed pcretest so that:
135    
136        (a) When it is outputting text in the compiled version of a pattern, bytes
137            other than 32-126 are always shown as hex escapes.
138    
139        (b) When it is outputting text that is a matched part of a subject string,
140            it does the same, unless a different locale has been set for the match
141            (using the /L modifier). In this case, it uses isprint() to decide.
142    
143     4. Fixed a major bug that caused incorrect computation of the amount of memory
144        required for a compiled pattern when options that changed within the
145        pattern affected the logic of the preliminary scan that determines the
146        length. The relevant options are -x, and -i in UTF-8 mode. The result was
147        that the computed length was too small. The symptoms of this bug were
148        either the PCRE error "internal error: code overflow" from pcre_compile(),
149        or a glibc crash with a message such as "pcretest: free(): invalid next
150        size (fast)". Examples of patterns that provoked this bug (shown in
151        pcretest format) are:
152    
153          /(?-x: )/x
154          /(?x)(?-x: \s*#\s*)/
155          /((?i)[\x{c0}])/8
156          /(?i:[\x{c0}])/8
157    
158        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
159        is now done differently.
160    
161     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
162        wrapper classes; (b) implement a new function in the C++ scanner that is
163        more efficient than the old way of doing things because it avoids levels of
164        recursion in the regex matching; (c) add a paragraph to the documentation
165        for the FullMatch() function.
166    
167     6. The escape sequence \n was being treated as whatever was defined as
168        "newline". Not only was this contrary to the documentation, which states
169        that \n is character 10 (hex 0A), but it also went horribly wrong when
170        "newline" was defined as CRLF. This has been fixed.
171    
172     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
173        was being set to -1 for the "end of line" case (supposedly a value that no
174        character can have). Though this value is never used (the check for end of
175        line is "zero bytes in current character"), it caused compiler complaints.
176        I've changed it to 0xffffffff.
177    
178     8. In pcre_version.c, the version string was being built by a sequence of
179        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
180        string (as it is for production releases) called a macro with an empty
181        argument. The C standard says the result of this is undefined. The gcc
182        compiler treats it as an empty string (which was what was wanted) but it is
183        reported that Visual C gives an error. The source has been hacked around to
184        avoid this problem.
185    
186     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
187        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
188        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
189        of them did).
190    
191    10. Originally, pcretest opened its input and output without "b"; then I was
192        told that "b" was needed in some environments, so it was added for release
193        5.0 to both the input and output. (It makes no difference on Unix-like
194        systems.) Later I was told that it is wrong for the input on Windows. I've
195        now abstracted the modes into two macros, to make it easier to fiddle with
196        them, and removed "b" from the input mode under Windows.
197    
198    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
199    
200    12. Added -help and --help to pcretest as an official way of being reminded
201        of the options.
202    
203    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
204        and pcrecpp.cc because they annoy compilers at high warning levels.
205    
206    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
207    
208    15. Fixed an occurrence of == in configure.ac that should have been = (shell
209        scripts are not C programs :-) and which was not noticed because it works
210        on Linux.
211    
212    16. pcretest is supposed to handle any length of pattern and data line (as one
213        line or as a continued sequence of lines) by extending its input buffer if
214        necessary. This feature was broken for very long pattern lines, leading to
215        a string of junk being passed to pcre_compile() if the pattern was longer
216        than about 50K.
217    
218    17. I have done a major re-factoring of the way pcre_compile() computes the
219        amount of memory needed for a compiled pattern. Previously, there was code
220        that made a preliminary scan of the pattern in order to do this. That was
221        OK when PCRE was new, but as the facilities have expanded, it has become
222        harder and harder to keep it in step with the real compile phase, and there
223        have been a number of bugs (see for example, 4 above). I have now found a
224        cunning way of running the real compile function in a "fake" mode that
225        enables it to compute how much memory it would need, while actually only
226        ever using a few hundred bytes of working memory and without too many
227        tests of the mode. This should make future maintenance and development
228        easier. A side effect of this work is that the limit of 200 on the nesting
229        depth of parentheses has been removed (though this was never a serious
230        limitation, I suspect). However, there is a downside: pcre_compile() now
231        runs more slowly than before (30% or more, depending on the pattern). I
232        hope this isn't a big issue. There is no effect on runtime performance.
233    
234    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
235        newline (only possible for the last line of a file) and it was a
236        pattern that set a locale (followed by /Lsomething), pcretest crashed.
237    
238    19. Added additional timing features to pcretest. (1) The -tm option now times
239        matching only, not compiling. (2) Both -t and -tm can be followed, as a
240        separate command line item, by a number that specifies the number of
241        repeats to use when timing. The default is 50000; this gives better
242        precision, but takes uncomfortably long for very large patterns.
243    
244    20. Extended pcre_study() to be more clever in cases where a branch of a
245        subpattern has no definite first character. For example, (a*|b*)[cd] would
246        previously give no result from pcre_study(). Now it recognizes that the
247        first character must be a, b, c, or d.
248    
249    21. There was an incorrect error "recursive call could loop indefinitely" if
250        a subpattern (or the entire pattern) that was being tested for matching an
251        empty string contained only one non-empty item after a nested subpattern.
252        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
253        incorrectly, because the \d was being skipped in the check.
254    
255    22. The pcretest program now has a new pattern option /B and a command line
256        option -b, which is equivalent to adding /B to every pattern. This causes
257        it to show the compiled bytecode, without the additional information that
258        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
259        is the same as /B/I).
260    
261    23. A new optimization is now able automatically to treat some sequences such
262        as a*b as a*+b. More specifically, if something simple (such as a character
263        or a simple class like \d) has an unlimited quantifier, and is followed by
264        something that cannot possibly match the quantified thing, the quantifier
265        is automatically "possessified".
266    
267    24. A recursive reference to a subpattern whose number was greater than 39
268        went wrong under certain circumstances in UTF-8 mode. This bug could also
269        have affected the operation of pcre_study().
270    
271    25. Realized that a little bit of performance could be had by replacing
272        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
273    
274    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
275    
276    27. Possessive quantifiers such as a++ were previously implemented by turning
277        them into atomic groups such as ($>a+). Now they have their own opcodes,
278        which improves performance. This includes the automatically created ones
279        from 23 above.
280    
281    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
282        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
283        the first matched character to be a colon. This applied both to named and
284        numbered groups.
285    
286    29. The ucpinternal.h header file was missing its idempotency #ifdef.
287    
288    30. I was sent a "project" file called libpcre.a.dev which I understand makes
289        building PCRE on Windows easier, so I have included it in the distribution.
290    
291    31. There is now a check in pcretest against a ridiculously large number being
292        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
293        loop, the loop is abandoned.
294    
295    32. Forward references to subpatterns in conditions such as (?(2)...) where
296        subpattern 2 is defined later cause pcre_compile() to search forwards in
297        the pattern for the relevant set of parentheses. This search went wrong
298        when there were unescaped parentheses in a character class, parentheses
299        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
300    
301    33. "Subroutine" calls and backreferences were previously restricted to
302        referencing subpatterns earlier in the regex. This restriction has now
303        been removed.
304    
305    34. Added a number of extra features that are going to be in Perl 5.10. On the
306        whole, these are just syntactic alternatives for features that PCRE had
307        previously implemented using the Python syntax or my own invention. The
308        other formats are all retained for compatibility.
309    
310        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
311            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
312            also .NET compatible.
313    
314        (b) A recursion or subroutine call to a named group can now be defined as
315            (?&name) as well as (?P>name).
316    
317        (c) A backreference to a named group can now be defined as \k<name> or
318            \k'name' as well as (?P=name). The new forms, as well as being in Perl
319            5.10, are also .NET compatible.
320    
321        (d) A conditional reference to a named group can now use the syntax
322            (?(<name>) or (?('name') as well as (?(name).
323    
324        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
325            groups (named and numbered) that are never evaluated inline, but can be
326            called as "subroutines" from elsewhere. In effect, the DEFINE condition
327            is always false. There may be only one alternative in such a group.
328    
329        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
330            as the simple (?(R). The condition is true only if the most recent
331            recursion is that of the given number or name. It does not search out
332            through the entire recursion stack.
333    
334        (g) The escape \gN or \g{N} has been added, where N is a positive or
335            negative number, specifying an absolute or relative reference.
336    
337    35. Tidied to get rid of some further signed/unsigned compiler warnings and
338        some "unreachable code" warnings.
339    
340    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
341        things, this adds five new scripts.
342    
343    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
344        There were also incompatibilities regarding the handling of \Q..\E inside
345        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
346        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
347    
348    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
349        matches an empty string, and forcibly breaks the loop. There were bugs in
350        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
351        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
352        separate and independent bugs (that affected different cases) have been
353        fixed.
354    
355    39. Refactored the code to abolish the use of different opcodes for small
356        capturing bracket numbers. This is a tidy that I avoided doing when I
357        removed the limit on the number of capturing brackets for 3.5 back in 2001.
358        The new approach is not only tidier, it makes it possible to reduce the
359        memory needed to fix the previous bug (38).
360    
361    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
362        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
363        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
364        mode.
365    
366    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
367        report.
368    
369    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
370        copy construction and assignment in the C++ wrapper.
371    
372    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
373        couple of bugs that could have given wrong results in the "--newline=crlf"
374        case.
375    
376    44. Added a number of casts and did some reorganization of signed/unsigned int
377        variables following suggestions from Dair Grant. Also renamed the variable
378        "this" as "item" because it is a C++ keyword.
379    
380    45. Arranged for dftables to add
381    
382          #include "pcre_internal.h"
383    
384        to pcre_chartables.c because without it, gcc 4.x may remove the array
385        definition from the final binary if PCRE is built into a static library and
386        dead code stripping is activated.
387    
388    46. For an unanchored pattern, if a match attempt fails at the start of a
389        newline sequence, and the newline setting is CRLF or ANY, and the next two
390        characters are CRLF, advance by two characters instead of one.
391    
392    
393    Version 6.7 04-Jul-06
394    ---------------------
395    
396     1. In order to handle tests when input lines are enormously long, pcretest has
397        been re-factored so that it automatically extends its buffers when
398        necessary. The code is crude, but this _is_ just a test program. The
399        default size has been increased from 32K to 50K.
400    
401     2. The code in pcre_study() was using the value of the re argument before
402        testing it for NULL. (Of course, in any sensible call of the function, it
403        won't be NULL.)
404    
405     3. The memmove() emulation function in pcre_internal.h, which is used on
406        systems that lack both memmove() and bcopy() - that is, hardly ever -
407        was missing a "static" storage class specifier.
408    
409     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
410        containing an extended class (one that cannot be represented by a bitmap
411        because it contains high-valued characters or Unicode property items, e.g.
412        [\pZ]). Almost always one would set UTF-8 mode when processing such a
413        pattern, but PCRE should not loop if you do not (it no longer does).
414        [Detail: two cases were found: (a) a repeated subpattern containing an
415        extended class; (b) a recursive reference to a subpattern that followed a
416        previous extended class. It wasn't skipping over the extended class
417        correctly when UTF-8 mode was not set.]
418    
419     5. A negated single-character class was not being recognized as fixed-length
420        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
421        compile error "lookbehind assertion is not fixed length".
422    
423     6. The RunPerlTest auxiliary script was showing an unexpected difference
424        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
425        write a Perl script that can interpret lines of an input file either as
426        byte characters or as UTF-8, which is what "perltest" was being required to
427        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
428        can't do is switch easily at run time between having the "use utf8;" pragma
429        or not. In the end, I fudged it by using the RunPerlTest script to insert
430        "use utf8;" explicitly for the UTF-8 tests.
431    
432     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
433        the end of the subject string, contrary to the documentation and to what
434        Perl does. This was true of both matching functions. Now it matches only at
435        the start of the subject and immediately after *internal* newlines.
436    
437     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
438        a pointer to an int instead of a pointer to an unsigned long int. This
439        caused problems on 64-bit systems.
440    
441     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
442        instance of the 'standard' template library not being so standard".
443    
444    10. There was no check on the number of named subpatterns nor the maximum
445        length of a subpattern name. The product of these values is used to compute
446        the size of the memory block for a compiled pattern. By supplying a very
447        long subpattern name and a large number of named subpatterns, the size
448        computation could be caused to overflow. This is now prevented by limiting
449        the length of names to 32 characters, and the number of named subpatterns
450        to 10,000.
451    
452    11. Subpatterns that are repeated with specific counts have to be replicated in
453        the compiled pattern. The size of memory for this was computed from the
454        length of the subpattern and the repeat count. The latter is limited to
455        65535, but there was no limit on the former, meaning that integer overflow
456        could in principle occur. The compiled length of a repeated subpattern is
457        now limited to 30,000 bytes in order to prevent this.
458    
459    12. Added the optional facility to have named substrings with the same name.
460    
461    13. Added the ability to use a named substring as a condition, using the
462        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
463        are numbers (not recommended). Forward references are permitted.
464    
465    14. Added forward references in named backreferences (if you see what I mean).
466    
467    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
468        pattern could run off the end of the subject. For example, the pattern
469        "(?s)(.{1,5})"8 did this with the subject "ab".
470    
471    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
472        PCRE_CASELESS was set when matching characters that were quantified with ?
473        or *.
474    
475    17. A character class other than a single negated character that had a minimum
476        but no maximum quantifier - for example [ab]{6,} - was not handled
477        correctly by pce_dfa_exec(). It would match only one character.
478    
479    18. A valid (though odd) pattern that looked like a POSIX character
480        class but used an invalid character after [ (for example [[,abc,]]) caused
481        pcre_compile() to give the error "Failed: internal error: code overflow" or
482        in some cases to crash with a glibc free() error. This could even happen if
483        the pattern terminated after [[ but there just happened to be a sequence of
484        letters, a binary zero, and a closing ] in the memory that followed.
485    
486    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
487        over the years. Originally (before any Unicode support), just the bottom 8
488        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
489        output from "man perlunicode" includes this:
490    
491          The regular expression compiler produces polymorphic opcodes.  That
492          is, the pattern adapts to the data and automatically switches to
493          the Unicode character scheme when presented with Unicode data--or
494          instead uses a traditional byte scheme when presented with byte
495          data.
496    
497        Sadly, a wide octal escape does not cause a switch, and in a string with
498        no other multibyte characters, these octal escapes are treated as before.
499        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
500        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
501        Unicode string.
502    
503        I have not perpetrated such confusion in PCRE. Up till now, it took just
504        the bottom 8 bits, as in old Perl. I have now made octal escapes with
505        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
506        translate to the appropriate multibyte character.
507    
508    29. Applied some refactoring to reduce the number of warnings from Microsoft
509        and Borland compilers. This has included removing the fudge introduced
510        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
511        a warning about an unused variable.
512    
513    21. PCRE has not included VT (character 0x0b) in the set of whitespace
514        characters since release 4.0, because Perl (from release 5.004) does not.
515        [Or at least, is documented not to: some releases seem to be in conflict
516        with the documentation.] However, when a pattern was studied with
517        pcre_study() and all its branches started with \s, PCRE still included VT
518        as a possible starting character. Of course, this did no harm; it just
519        caused an unnecessary match attempt.
520    
521    22. Removed a now-redundant internal flag bit that recorded the fact that case
522        dependency changed within the pattern. This was once needed for "required
523        byte" processing, but is no longer used. This recovers a now-scarce options
524        bit. Also moved the least significant internal flag bit to the most-
525        significant bit of the word, which was not previously used (hangover from
526        the days when it was an int rather than a uint) to free up another bit for
527        the future.
528    
529    23. Added support for CRLF line endings as well as CR and LF. As well as the
530        default being selectable at build time, it can now be changed at runtime
531        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
532        specify that it is scanning data with non-default line endings.
533    
534    24. Changed the definition of CXXLINK to make it agree with the definition of
535        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
536    
537    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
538        recursions. This makes a big different to stack usage for some patterns.
539    
540    26. If a subpattern containing a named recursion or subroutine reference such
541        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
542        the space required for the compiled pattern went wrong and gave too small a
543        value. Depending on the environment, this could lead to "Failed: internal
544        error: code overflow at offset 49" or "glibc detected double free or
545        corruption" errors.
546    
547    27. Applied patches from Google (a) to support the new newline modes and (b) to
548        advance over multibyte UTF-8 characters in GlobalReplace.
549    
550    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
551        difference for some implementation of PCRE in some Windows version.
552    
553    29. Added some extra testing facilities to pcretest:
554    
555        \q<number>   in a data line sets the "match limit" value
556        \Q<number>   in a data line sets the "match recursion limt" value
557        -S <number>  sets the stack size, where <number> is in megabytes
558    
559        The -S option isn't available for Windows.
560    
561    
562  Version 6.6 06-Feb-06  Version 6.6 06-Feb-06
563  ---------------------  ---------------------
564    

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