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revision 91 by nigel, Sat Feb 24 21:41:34 2007 UTC revision 222 by ph10, Fri Aug 17 10:48:51 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4    Version 7.3 17-Aug-07
5    ---------------------
6    
7     1. In the rejigging of the build system that eventually resulted in 7.1, the
8        line "#include <pcre.h>" was included in pcre_internal.h. The use of angle
9        brackets there is not right, since it causes compilers to look for an
10        installed pcre.h, not the version that is in the source that is being
11        compiled (which of course may be different). I have changed it back to:
12    
13          #include "pcre.h"
14    
15        I have a vague recollection that the change was concerned with compiling in
16        different directories, but in the new build system, that is taken care of
17        by the VPATH setting the Makefile.
18    
19     2. The pattern .*$ when run in not-DOTALL UTF-8 mode with newline=any failed
20        when the subject happened to end in the byte 0x85 (e.g. if the last
21        character was \x{1ec5}). *Character* 0x85 is one of the "any" newline
22        characters but of course it shouldn't be taken as a newline when it is part
23        of another character. The bug was that, for an unlimited repeat of . in
24        not-DOTALL UTF-8 mode, PCRE was advancing by bytes rather than by
25        characters when looking for a newline.
26    
27     3. A small performance improvement in the DOTALL UTF-8 mode .* case.
28    
29     4. Debugging: adjusted the names of opcodes for different kinds of parentheses
30        in debug output.
31    
32     5. Arrange to use "%I64d" instead of "%lld" and "%I64u" instead of "%llu" for
33        long printing in the pcrecpp unittest when running under MinGW.
34    
35     6. ESC_K was left out of the EBCDIC table.
36    
37     7. Change 7.0/38 introduced a new limit on the number of nested non-capturing
38        parentheses; I made it 1000, which seemed large enough. Unfortunately, the
39        limit also applies to "virtual nesting" when a pattern is recursive, and in
40        this case 1000 isn't so big. I have been able to remove this limit at the
41        expense of backing off one optimization in certain circumstances. Normally,
42        when pcre_exec() would call its internal match() function recursively and
43        immediately return the result unconditionally, it uses a "tail recursion"
44        feature to save stack. However, when a subpattern that can match an empty
45        string has an unlimited repetition quantifier, it no longer makes this
46        optimization. That gives it a stack frame in which to save the data for
47        checking that an empty string has been matched. Previously this was taken
48        from the 1000-entry workspace that had been reserved. So now there is no
49        explicit limit, but more stack is used.
50    
51     8. Applied Daniel's patches to solve problems with the import/export magic
52        syntax that is required for Windows, and which was going wrong for the
53        pcreposix and pcrecpp parts of the library. These were overlooked when this
54        problem was solved for the main library.
55    
56     9. There were some crude static tests to avoid integer overflow when computing
57        the size of patterns that contain repeated groups with explicit upper
58        limits. As the maximum quantifier is 65535, the maximum group length was
59        set at 30,000 so that the product of these two numbers did not overflow a
60        32-bit integer. However, it turns out that people want to use groups that
61        are longer than 30,000 bytes (though not repeat them that many times).
62        Change 7.0/17 (the refactoring of the way the pattern size is computed) has
63        made it possible to implement the integer overflow checks in a much more
64        dynamic way, which I have now done. The artificial limitation on group
65        length has been removed - we now have only the limit on the total length of
66        the compiled pattern, which depends on the LINK_SIZE setting.
67    
68    10. Fixed a bug in the documentation for get/copy named substring when
69        duplicate names are permitted. If none of the named substrings are set, the
70        functions return PCRE_ERROR_NOSUBSTRING (7); the doc said they returned an
71        empty string.
72    
73    11. Because Perl interprets \Q...\E at a high level, and ignores orphan \E
74        instances, patterns such as [\Q\E] or [\E] or even [^\E] cause an error,
75        because the ] is interpreted as the first data character and the
76        terminating ] is not found. PCRE has been made compatible with Perl in this
77        regard. Previously, it interpreted [\Q\E] as an empty class, and [\E] could
78        cause memory overwriting.
79    
80    10. Like Perl, PCRE automatically breaks an unlimited repeat after an empty
81        string has been matched (to stop an infinite loop). It was not recognizing
82        a conditional subpattern that could match an empty string if that
83        subpattern was within another subpattern. For example, it looped when
84        trying to match  (((?(1)X|))*)  but it was OK with  ((?(1)X|)*)  where the
85        condition was not nested. This bug has been fixed.
86    
87    12. A pattern like \X?\d or \P{L}?\d in non-UTF-8 mode could cause a backtrack
88        past the start of the subject in the presence of bytes with the top bit
89        set, for example "\x8aBCD".
90    
91    13. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
92        (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
93    
94    14. Optimized (?!) to (*FAIL).
95    
96    15. Updated the test for a valid UTF-8 string to conform to the later RFC 3629.
97        This restricts code points to be within the range 0 to 0x10FFFF, excluding
98        the "low surrogate" sequence 0xD800 to 0xDFFF. Previously, PCRE allowed the
99        full range 0 to 0x7FFFFFFF, as defined by RFC 2279. Internally, it still
100        does: it's just the validity check that is more restrictive.
101    
102    16. Inserted checks for integer overflows during escape sequence (backslash)
103        processing, and also fixed erroneous offset values for syntax errors during
104        backslash processing.
105    
106    17. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
107        for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
108    
109    18. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
110        caused an overrun.
111    
112    19. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
113        something other than just ASCII characters) inside a group that had an
114        unlimited repeat caused a loop at compile time (while checking to see
115        whether the group could match an empty string).
116    
117    20. Debugging a pattern containing \p or \P could cause a crash. For example,
118        [\P{Any}] did so. (Error in the code for printing property names.)
119    
120    21. An orphan \E inside a character class could cause a crash.
121    
122    22. A repeated capturing bracket such as (A)? could cause a wild memory
123        reference during compilation.
124    
125    23. There are several functions in pcre_compile() that scan along a compiled
126        expression for various reasons (e.g. to see if it's fixed length for look
127        behind). There were bugs in these functions when a repeated \p or \P was
128        present in the pattern. These operators have additional parameters compared
129        with \d, etc, and these were not being taken into account when moving along
130        the compiled data. Specifically:
131    
132        (a) A item such as \p{Yi}{3} in a lookbehind was not treated as fixed
133            length.
134    
135        (b) An item such as \pL+ within a repeated group could cause crashes or
136            loops.
137    
138        (c) A pattern such as \p{Yi}+(\P{Yi}+)(?1) could give an incorrect
139            "reference to non-existent subpattern" error.
140    
141        (d) A pattern like (\P{Yi}{2}\277)? could loop at compile time.
142    
143    24. A repeated \S or \W in UTF-8 mode could give wrong answers when multibyte
144        characters were involved (for example /\S{2}/8g with "A\x{a3}BC").
145    
146    25. Using pcregrep in multiline, inverted mode (-Mv) caused it to loop.
147    
148    
149    Version 7.2 19-Jun-07
150    ---------------------
151    
152     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
153        which is apparently normally available under Windows.
154    
155     2. Re-jig the pcregrep tests with different newline settings in an attempt
156        to make them independent of the local environment's newline setting.
157    
158     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
159    
160     4. Some of the "internals" tests were previously cut out when the link size
161        was not 2, because the output contained actual offsets. The recent new
162        "Z" feature of pcretest means that these can be cut out, making the tests
163        usable with all link sizes.
164    
165     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
166        stack recursion. This gives a massive performance boost under BSD, but just
167        a small improvement under Linux. However, it saves one field in the frame
168        in all cases.
169    
170     6. Added more features from the forthcoming Perl 5.10:
171    
172        (a) (?-n) (where n is a string of digits) is a relative subroutine or
173            recursion call. It refers to the nth most recently opened parentheses.
174    
175        (b) (?+n) is also a relative subroutine call; it refers to the nth next
176            to be opened parentheses.
177    
178        (c) Conditions that refer to capturing parentheses can be specified
179            relatively, for example, (?(-2)... or (?(+3)...
180    
181        (d) \K resets the start of the current match so that everything before
182            is not part of it.
183    
184        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
185    
186        (f) \g{name} is another synonym - part of Perl 5.10's unification of
187            reference syntax.
188    
189        (g) (?| introduces a group in which the numbering of parentheses in each
190            alternative starts with the same number.
191    
192        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
193    
194     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
195        PCRE_INFO_JCHANGED.
196    
197     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
198        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
199        for detecting groups that can match an empty string.
200    
201     9. A pattern with a very large number of alternatives (more than several
202        hundred) was running out of internal workspace during the pre-compile
203        phase, where pcre_compile() figures out how much memory will be needed. A
204        bit of new cunning has reduced the workspace needed for groups with
205        alternatives. The 1000-alternative test pattern now uses 12 bytes of
206        workspace instead of running out of the 4096 that are available.
207    
208    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
209    
210    11. Applied patch from Google to remove an optimization that didn't quite work.
211        The report of the bug said:
212    
213          pcrecpp::RE("a*").FullMatch("aaa") matches, while
214          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
215          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
216    
217    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
218        it matched the wrong number of bytes.
219    
220    
221    Version 7.1 24-Apr-07
222    ---------------------
223    
224     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
225        that is more "standard", making use of automake and other Autotools. There
226        is some re-arrangement of the files and adjustment of comments consequent
227        on this.
228    
229     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
230        for recursive directory scanning broke on some systems because the files
231        are not scanned in any specific order and on different systems the order
232        was different. A call to "sort" has been inserted into RunGrepTest for the
233        approprate test as a short-term fix. In the longer term there may be an
234        alternative.
235    
236     3. I had an email from Eric Raymond about problems translating some of PCRE's
237        man pages to HTML (despite the fact that I distribute HTML pages, some
238        people do their own conversions for various reasons). The problems
239        concerned the use of low-level troff macros .br and .in. I have therefore
240        removed all such uses from the man pages (some were redundant, some could
241        be replaced by .nf/.fi pairs). The 132html script that I use to generate
242        HTML has been updated to handle .nf/.fi and to complain if it encounters
243        .br or .in.
244    
245     4. Updated comments in configure.ac that get placed in config.h.in and also
246        arranged for config.h to be included in the distribution, with the name
247        config.h.generic, for the benefit of those who have to compile without
248        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
249    
250     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
251        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
252        makevp.bat for the current PCRE, using the additional files
253        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
254    
255     6. A Windows user reported a minor discrepancy with test 2, which turned out
256        to be caused by a trailing space on an input line that had got lost in his
257        copy. The trailing space was an accident, so I've just removed it.
258    
259     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
260        that is needed.
261    
262     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
263        as "const" (a) because they are and (b) because it helps the PHP
264        maintainers who have recently made a script to detect big data structures
265        in the php code that should be moved to the .rodata section. I remembered
266        to update Builducptable as well, so it won't revert if ucptable.h is ever
267        re-created.
268    
269     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
270        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
271        order to be able to cut out the UTF-8 tables in the latter when UTF-8
272        support is not required. This saves 1.5-2K of code, which is important in
273        some applications.
274    
275        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
276        so as not to refer to the tables, even though these functions will never be
277        called when UTF-8 support is disabled. Otherwise there are problems with a
278        shared library.
279    
280    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
281    
282        (a) It was defining its arguments as char * instead of void *.
283    
284        (b) It was assuming that all moves were upwards in memory; this was true
285            a long time ago when I wrote it, but is no longer the case.
286    
287        The emulated memove() is provided for those environments that have neither
288        memmove() nor bcopy(). I didn't think anyone used it these days, but that
289        is clearly not the case, as these two bugs were recently reported.
290    
291    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
292        and Detrail to create the HTML documentation, the .txt form of the man
293        pages, and it removes trailing spaces from listed files. It also creates
294        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
295        case, it wraps all the #defines with #ifndefs. This script should be run
296        before "make dist".
297    
298    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
299        with Unicode property support.
300    
301        (a) For a maximizing quantifier, if the two different cases of the
302            character were of different lengths in their UTF-8 codings (there are
303            some cases like this - I found 11), and the matching function had to
304            back up over a mixture of the two cases, it incorrectly assumed they
305            were both the same length.
306    
307        (b) When PCRE was configured to use the heap rather than the stack for
308            recursion during matching, it was not correctly preserving the data for
309            the other case of a UTF-8 character when checking ahead for a match
310            while processing a minimizing repeat. If the check also involved
311            matching a wide character, but failed, corruption could cause an
312            erroneous result when trying to check for a repeat of the original
313            character.
314    
315    13. Some tidying changes to the testing mechanism:
316    
317        (a) The RunTest script now detects the internal link size and whether there
318            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
319            values substituted by "configure". (The RunGrepTest script already did
320            this for UTF-8.) The configure.ac script no longer substitutes the
321            relevant variables.
322    
323        (b) The debugging options /B and /D in pcretest show the compiled bytecode
324            with length and offset values. This means that the output is different
325            for different internal link sizes. Test 2 is skipped for link sizes
326            other than 2 because of this, bypassing the problem. Unfortunately,
327            there was also a test in test 3 (the locale tests) that used /B and
328            failed for link sizes other than 2. Rather than cut the whole test out,
329            I have added a new /Z option to pcretest that replaces the length and
330            offset values with spaces. This is now used to make test 3 independent
331            of link size. (Test 2 will be tidied up later.)
332    
333    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
334        segmentation fault instead of returning the appropriate error message.
335    
336    15. In multiline mode when the newline sequence was set to "any", the pattern
337        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
338        This doesn't seem right; it now treats the CRLF combination as the line
339        ending, and so does not match in that case. It's only a pattern such as ^$
340        that would hit this one: something like ^ABC$ would have failed after \r
341        and then tried again after \r\n.
342    
343    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
344        in an attempt to make files that differ only in their line terminators
345        compare equal. This works on Linux.
346    
347    17. Under certain error circumstances pcregrep might try to free random memory
348        as it exited. This is now fixed, thanks to valgrind.
349    
350    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
351        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
352        was because its rules for how to advance for /g after matching an empty
353        string at the end of a line did not allow for this case. They now check for
354        it specially.
355    
356    20. pcretest is supposed to handle patterns and data of any length, by
357        extending its buffers when necessary. It was getting this wrong when the
358        buffer for a data line had to be extended.
359    
360    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
361        CRLF as a newline sequence.
362    
363    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
364        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
365        I have nevertheless tidied it up.
366    
367    23. Added some casts to kill warnings from HP-UX ia64 compiler.
368    
369    24. Added a man page for pcre-config.
370    
371    
372    Version 7.0 19-Dec-06
373    ---------------------
374    
375     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
376        moving to gcc 4.1.1.
377    
378     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
379        sys/time.h, which is documented as needed for this function. It doesn't
380        seem to matter on Linux, but it showed up on some releases of OS X.
381    
382     3. It seems that there are systems where bytes whose values are greater than
383        127 match isprint() in the "C" locale. The "C" locale should be the
384        default when a C program starts up. In most systems, only ASCII printing
385        characters match isprint(). This difference caused the output from pcretest
386        to vary, making some of the tests fail. I have changed pcretest so that:
387    
388        (a) When it is outputting text in the compiled version of a pattern, bytes
389            other than 32-126 are always shown as hex escapes.
390    
391        (b) When it is outputting text that is a matched part of a subject string,
392            it does the same, unless a different locale has been set for the match
393            (using the /L modifier). In this case, it uses isprint() to decide.
394    
395     4. Fixed a major bug that caused incorrect computation of the amount of memory
396        required for a compiled pattern when options that changed within the
397        pattern affected the logic of the preliminary scan that determines the
398        length. The relevant options are -x, and -i in UTF-8 mode. The result was
399        that the computed length was too small. The symptoms of this bug were
400        either the PCRE error "internal error: code overflow" from pcre_compile(),
401        or a glibc crash with a message such as "pcretest: free(): invalid next
402        size (fast)". Examples of patterns that provoked this bug (shown in
403        pcretest format) are:
404    
405          /(?-x: )/x
406          /(?x)(?-x: \s*#\s*)/
407          /((?i)[\x{c0}])/8
408          /(?i:[\x{c0}])/8
409    
410        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
411        is now done differently.
412    
413     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
414        wrapper classes; (b) implement a new function in the C++ scanner that is
415        more efficient than the old way of doing things because it avoids levels of
416        recursion in the regex matching; (c) add a paragraph to the documentation
417        for the FullMatch() function.
418    
419     6. The escape sequence \n was being treated as whatever was defined as
420        "newline". Not only was this contrary to the documentation, which states
421        that \n is character 10 (hex 0A), but it also went horribly wrong when
422        "newline" was defined as CRLF. This has been fixed.
423    
424     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
425        was being set to -1 for the "end of line" case (supposedly a value that no
426        character can have). Though this value is never used (the check for end of
427        line is "zero bytes in current character"), it caused compiler complaints.
428        I've changed it to 0xffffffff.
429    
430     8. In pcre_version.c, the version string was being built by a sequence of
431        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
432        string (as it is for production releases) called a macro with an empty
433        argument. The C standard says the result of this is undefined. The gcc
434        compiler treats it as an empty string (which was what was wanted) but it is
435        reported that Visual C gives an error. The source has been hacked around to
436        avoid this problem.
437    
438     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
439        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
440        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
441        of them did).
442    
443    10. Originally, pcretest opened its input and output without "b"; then I was
444        told that "b" was needed in some environments, so it was added for release
445        5.0 to both the input and output. (It makes no difference on Unix-like
446        systems.) Later I was told that it is wrong for the input on Windows. I've
447        now abstracted the modes into two macros, to make it easier to fiddle with
448        them, and removed "b" from the input mode under Windows.
449    
450    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
451    
452    12. Added -help and --help to pcretest as an official way of being reminded
453        of the options.
454    
455    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
456        and pcrecpp.cc because they annoy compilers at high warning levels.
457    
458    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
459    
460    15. Fixed an occurrence of == in configure.ac that should have been = (shell
461        scripts are not C programs :-) and which was not noticed because it works
462        on Linux.
463    
464    16. pcretest is supposed to handle any length of pattern and data line (as one
465        line or as a continued sequence of lines) by extending its input buffer if
466        necessary. This feature was broken for very long pattern lines, leading to
467        a string of junk being passed to pcre_compile() if the pattern was longer
468        than about 50K.
469    
470    17. I have done a major re-factoring of the way pcre_compile() computes the
471        amount of memory needed for a compiled pattern. Previously, there was code
472        that made a preliminary scan of the pattern in order to do this. That was
473        OK when PCRE was new, but as the facilities have expanded, it has become
474        harder and harder to keep it in step with the real compile phase, and there
475        have been a number of bugs (see for example, 4 above). I have now found a
476        cunning way of running the real compile function in a "fake" mode that
477        enables it to compute how much memory it would need, while actually only
478        ever using a few hundred bytes of working memory and without too many
479        tests of the mode. This should make future maintenance and development
480        easier. A side effect of this work is that the limit of 200 on the nesting
481        depth of parentheses has been removed (though this was never a serious
482        limitation, I suspect). However, there is a downside: pcre_compile() now
483        runs more slowly than before (30% or more, depending on the pattern). I
484        hope this isn't a big issue. There is no effect on runtime performance.
485    
486    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
487        newline (only possible for the last line of a file) and it was a
488        pattern that set a locale (followed by /Lsomething), pcretest crashed.
489    
490    19. Added additional timing features to pcretest. (1) The -tm option now times
491        matching only, not compiling. (2) Both -t and -tm can be followed, as a
492        separate command line item, by a number that specifies the number of
493        repeats to use when timing. The default is 50000; this gives better
494        precision, but takes uncomfortably long for very large patterns.
495    
496    20. Extended pcre_study() to be more clever in cases where a branch of a
497        subpattern has no definite first character. For example, (a*|b*)[cd] would
498        previously give no result from pcre_study(). Now it recognizes that the
499        first character must be a, b, c, or d.
500    
501    21. There was an incorrect error "recursive call could loop indefinitely" if
502        a subpattern (or the entire pattern) that was being tested for matching an
503        empty string contained only one non-empty item after a nested subpattern.
504        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
505        incorrectly, because the \d was being skipped in the check.
506    
507    22. The pcretest program now has a new pattern option /B and a command line
508        option -b, which is equivalent to adding /B to every pattern. This causes
509        it to show the compiled bytecode, without the additional information that
510        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
511        is the same as /B/I).
512    
513    23. A new optimization is now able automatically to treat some sequences such
514        as a*b as a*+b. More specifically, if something simple (such as a character
515        or a simple class like \d) has an unlimited quantifier, and is followed by
516        something that cannot possibly match the quantified thing, the quantifier
517        is automatically "possessified".
518    
519    24. A recursive reference to a subpattern whose number was greater than 39
520        went wrong under certain circumstances in UTF-8 mode. This bug could also
521        have affected the operation of pcre_study().
522    
523    25. Realized that a little bit of performance could be had by replacing
524        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
525    
526    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
527    
528    27. Possessive quantifiers such as a++ were previously implemented by turning
529        them into atomic groups such as ($>a+). Now they have their own opcodes,
530        which improves performance. This includes the automatically created ones
531        from 23 above.
532    
533    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
534        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
535        the first matched character to be a colon. This applied both to named and
536        numbered groups.
537    
538    29. The ucpinternal.h header file was missing its idempotency #ifdef.
539    
540    30. I was sent a "project" file called libpcre.a.dev which I understand makes
541        building PCRE on Windows easier, so I have included it in the distribution.
542    
543    31. There is now a check in pcretest against a ridiculously large number being
544        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
545        loop, the loop is abandoned.
546    
547    32. Forward references to subpatterns in conditions such as (?(2)...) where
548        subpattern 2 is defined later cause pcre_compile() to search forwards in
549        the pattern for the relevant set of parentheses. This search went wrong
550        when there were unescaped parentheses in a character class, parentheses
551        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
552    
553    33. "Subroutine" calls and backreferences were previously restricted to
554        referencing subpatterns earlier in the regex. This restriction has now
555        been removed.
556    
557    34. Added a number of extra features that are going to be in Perl 5.10. On the
558        whole, these are just syntactic alternatives for features that PCRE had
559        previously implemented using the Python syntax or my own invention. The
560        other formats are all retained for compatibility.
561    
562        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
563            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
564            also .NET compatible.
565    
566        (b) A recursion or subroutine call to a named group can now be defined as
567            (?&name) as well as (?P>name).
568    
569        (c) A backreference to a named group can now be defined as \k<name> or
570            \k'name' as well as (?P=name). The new forms, as well as being in Perl
571            5.10, are also .NET compatible.
572    
573        (d) A conditional reference to a named group can now use the syntax
574            (?(<name>) or (?('name') as well as (?(name).
575    
576        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
577            groups (named and numbered) that are never evaluated inline, but can be
578            called as "subroutines" from elsewhere. In effect, the DEFINE condition
579            is always false. There may be only one alternative in such a group.
580    
581        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
582            as the simple (?(R). The condition is true only if the most recent
583            recursion is that of the given number or name. It does not search out
584            through the entire recursion stack.
585    
586        (g) The escape \gN or \g{N} has been added, where N is a positive or
587            negative number, specifying an absolute or relative reference.
588    
589    35. Tidied to get rid of some further signed/unsigned compiler warnings and
590        some "unreachable code" warnings.
591    
592    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
593        things, this adds five new scripts.
594    
595    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
596        There were also incompatibilities regarding the handling of \Q..\E inside
597        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
598        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
599    
600    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
601        matches an empty string, and forcibly breaks the loop. There were bugs in
602        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
603        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
604        separate and independent bugs (that affected different cases) have been
605        fixed.
606    
607    39. Refactored the code to abolish the use of different opcodes for small
608        capturing bracket numbers. This is a tidy that I avoided doing when I
609        removed the limit on the number of capturing brackets for 3.5 back in 2001.
610        The new approach is not only tidier, it makes it possible to reduce the
611        memory needed to fix the previous bug (38).
612    
613    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
614        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
615        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
616        mode.
617    
618    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
619        report.
620    
621    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
622        copy construction and assignment in the C++ wrapper.
623    
624    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
625        couple of bugs that could have given wrong results in the "--newline=crlf"
626        case.
627    
628    44. Added a number of casts and did some reorganization of signed/unsigned int
629        variables following suggestions from Dair Grant. Also renamed the variable
630        "this" as "item" because it is a C++ keyword.
631    
632    45. Arranged for dftables to add
633    
634          #include "pcre_internal.h"
635    
636        to pcre_chartables.c because without it, gcc 4.x may remove the array
637        definition from the final binary if PCRE is built into a static library and
638        dead code stripping is activated.
639    
640    46. For an unanchored pattern, if a match attempt fails at the start of a
641        newline sequence, and the newline setting is CRLF or ANY, and the next two
642        characters are CRLF, advance by two characters instead of one.
643    
644    
645  Version 6.7 04-Jul-06  Version 6.7 04-Jul-06
646  ---------------------  ---------------------
647    

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