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revision 87 by nigel, Sat Feb 24 21:41:21 2007 UTC revision 210 by ph10, Wed Aug 8 14:24:50 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4    Version 7.3 05-Jul-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    
97    Version 7.2 19-Jun-07
98    ---------------------
99    
100     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
101        which is apparently normally available under Windows.
102    
103     2. Re-jig the pcregrep tests with different newline settings in an attempt
104        to make them independent of the local environment's newline setting.
105    
106     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
107    
108     4. Some of the "internals" tests were previously cut out when the link size
109        was not 2, because the output contained actual offsets. The recent new
110        "Z" feature of pcretest means that these can be cut out, making the tests
111        usable with all link sizes.
112    
113     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
114        stack recursion. This gives a massive performance boost under BSD, but just
115        a small improvement under Linux. However, it saves one field in the frame
116        in all cases.
117    
118     6. Added more features from the forthcoming Perl 5.10:
119    
120        (a) (?-n) (where n is a string of digits) is a relative subroutine or
121            recursion call. It refers to the nth most recently opened parentheses.
122    
123        (b) (?+n) is also a relative subroutine call; it refers to the nth next
124            to be opened parentheses.
125    
126        (c) Conditions that refer to capturing parentheses can be specified
127            relatively, for example, (?(-2)... or (?(+3)...
128    
129        (d) \K resets the start of the current match so that everything before
130            is not part of it.
131    
132        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
133    
134        (f) \g{name} is another synonym - part of Perl 5.10's unification of
135            reference syntax.
136    
137        (g) (?| introduces a group in which the numbering of parentheses in each
138            alternative starts with the same number.
139    
140        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
141    
142     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
143        PCRE_INFO_JCHANGED.
144    
145     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
146        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
147        for detecting groups that can match an empty string.
148    
149     9. A pattern with a very large number of alternatives (more than several
150        hundred) was running out of internal workspace during the pre-compile
151        phase, where pcre_compile() figures out how much memory will be needed. A
152        bit of new cunning has reduced the workspace needed for groups with
153        alternatives. The 1000-alternative test pattern now uses 12 bytes of
154        workspace instead of running out of the 4096 that are available.
155    
156    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
157    
158    11. Applied patch from Google to remove an optimization that didn't quite work.
159        The report of the bug said:
160    
161          pcrecpp::RE("a*").FullMatch("aaa") matches, while
162          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
163          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
164    
165    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
166        it matched the wrong number of bytes.
167    
168    
169    Version 7.1 24-Apr-07
170    ---------------------
171    
172     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
173        that is more "standard", making use of automake and other Autotools. There
174        is some re-arrangement of the files and adjustment of comments consequent
175        on this.
176    
177     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
178        for recursive directory scanning broke on some systems because the files
179        are not scanned in any specific order and on different systems the order
180        was different. A call to "sort" has been inserted into RunGrepTest for the
181        approprate test as a short-term fix. In the longer term there may be an
182        alternative.
183    
184     3. I had an email from Eric Raymond about problems translating some of PCRE's
185        man pages to HTML (despite the fact that I distribute HTML pages, some
186        people do their own conversions for various reasons). The problems
187        concerned the use of low-level troff macros .br and .in. I have therefore
188        removed all such uses from the man pages (some were redundant, some could
189        be replaced by .nf/.fi pairs). The 132html script that I use to generate
190        HTML has been updated to handle .nf/.fi and to complain if it encounters
191        .br or .in.
192    
193     4. Updated comments in configure.ac that get placed in config.h.in and also
194        arranged for config.h to be included in the distribution, with the name
195        config.h.generic, for the benefit of those who have to compile without
196        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
197    
198     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
199        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
200        makevp.bat for the current PCRE, using the additional files
201        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
202    
203     6. A Windows user reported a minor discrepancy with test 2, which turned out
204        to be caused by a trailing space on an input line that had got lost in his
205        copy. The trailing space was an accident, so I've just removed it.
206    
207     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
208        that is needed.
209    
210     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
211        as "const" (a) because they are and (b) because it helps the PHP
212        maintainers who have recently made a script to detect big data structures
213        in the php code that should be moved to the .rodata section. I remembered
214        to update Builducptable as well, so it won't revert if ucptable.h is ever
215        re-created.
216    
217     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
218        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
219        order to be able to cut out the UTF-8 tables in the latter when UTF-8
220        support is not required. This saves 1.5-2K of code, which is important in
221        some applications.
222    
223        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
224        so as not to refer to the tables, even though these functions will never be
225        called when UTF-8 support is disabled. Otherwise there are problems with a
226        shared library.
227    
228    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
229    
230        (a) It was defining its arguments as char * instead of void *.
231    
232        (b) It was assuming that all moves were upwards in memory; this was true
233            a long time ago when I wrote it, but is no longer the case.
234    
235        The emulated memove() is provided for those environments that have neither
236        memmove() nor bcopy(). I didn't think anyone used it these days, but that
237        is clearly not the case, as these two bugs were recently reported.
238    
239    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
240        and Detrail to create the HTML documentation, the .txt form of the man
241        pages, and it removes trailing spaces from listed files. It also creates
242        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
243        case, it wraps all the #defines with #ifndefs. This script should be run
244        before "make dist".
245    
246    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
247        with Unicode property support.
248    
249        (a) For a maximizing quantifier, if the two different cases of the
250            character were of different lengths in their UTF-8 codings (there are
251            some cases like this - I found 11), and the matching function had to
252            back up over a mixture of the two cases, it incorrectly assumed they
253            were both the same length.
254    
255        (b) When PCRE was configured to use the heap rather than the stack for
256            recursion during matching, it was not correctly preserving the data for
257            the other case of a UTF-8 character when checking ahead for a match
258            while processing a minimizing repeat. If the check also involved
259            matching a wide character, but failed, corruption could cause an
260            erroneous result when trying to check for a repeat of the original
261            character.
262    
263    13. Some tidying changes to the testing mechanism:
264    
265        (a) The RunTest script now detects the internal link size and whether there
266            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
267            values substituted by "configure". (The RunGrepTest script already did
268            this for UTF-8.) The configure.ac script no longer substitutes the
269            relevant variables.
270    
271        (b) The debugging options /B and /D in pcretest show the compiled bytecode
272            with length and offset values. This means that the output is different
273            for different internal link sizes. Test 2 is skipped for link sizes
274            other than 2 because of this, bypassing the problem. Unfortunately,
275            there was also a test in test 3 (the locale tests) that used /B and
276            failed for link sizes other than 2. Rather than cut the whole test out,
277            I have added a new /Z option to pcretest that replaces the length and
278            offset values with spaces. This is now used to make test 3 independent
279            of link size. (Test 2 will be tidied up later.)
280    
281    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
282        segmentation fault instead of returning the appropriate error message.
283    
284    15. In multiline mode when the newline sequence was set to "any", the pattern
285        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
286        This doesn't seem right; it now treats the CRLF combination as the line
287        ending, and so does not match in that case. It's only a pattern such as ^$
288        that would hit this one: something like ^ABC$ would have failed after \r
289        and then tried again after \r\n.
290    
291    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
292        in an attempt to make files that differ only in their line terminators
293        compare equal. This works on Linux.
294    
295    17. Under certain error circumstances pcregrep might try to free random memory
296        as it exited. This is now fixed, thanks to valgrind.
297    
298    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
299        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
300        was because its rules for how to advance for /g after matching an empty
301        string at the end of a line did not allow for this case. They now check for
302        it specially.
303    
304    20. pcretest is supposed to handle patterns and data of any length, by
305        extending its buffers when necessary. It was getting this wrong when the
306        buffer for a data line had to be extended.
307    
308    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
309        CRLF as a newline sequence.
310    
311    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
312        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
313        I have nevertheless tidied it up.
314    
315    23. Added some casts to kill warnings from HP-UX ia64 compiler.
316    
317    24. Added a man page for pcre-config.
318    
319    
320    Version 7.0 19-Dec-06
321    ---------------------
322    
323     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
324        moving to gcc 4.1.1.
325    
326     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
327        sys/time.h, which is documented as needed for this function. It doesn't
328        seem to matter on Linux, but it showed up on some releases of OS X.
329    
330     3. It seems that there are systems where bytes whose values are greater than
331        127 match isprint() in the "C" locale. The "C" locale should be the
332        default when a C program starts up. In most systems, only ASCII printing
333        characters match isprint(). This difference caused the output from pcretest
334        to vary, making some of the tests fail. I have changed pcretest so that:
335    
336        (a) When it is outputting text in the compiled version of a pattern, bytes
337            other than 32-126 are always shown as hex escapes.
338    
339        (b) When it is outputting text that is a matched part of a subject string,
340            it does the same, unless a different locale has been set for the match
341            (using the /L modifier). In this case, it uses isprint() to decide.
342    
343     4. Fixed a major bug that caused incorrect computation of the amount of memory
344        required for a compiled pattern when options that changed within the
345        pattern affected the logic of the preliminary scan that determines the
346        length. The relevant options are -x, and -i in UTF-8 mode. The result was
347        that the computed length was too small. The symptoms of this bug were
348        either the PCRE error "internal error: code overflow" from pcre_compile(),
349        or a glibc crash with a message such as "pcretest: free(): invalid next
350        size (fast)". Examples of patterns that provoked this bug (shown in
351        pcretest format) are:
352    
353          /(?-x: )/x
354          /(?x)(?-x: \s*#\s*)/
355          /((?i)[\x{c0}])/8
356          /(?i:[\x{c0}])/8
357    
358        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
359        is now done differently.
360    
361     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
362        wrapper classes; (b) implement a new function in the C++ scanner that is
363        more efficient than the old way of doing things because it avoids levels of
364        recursion in the regex matching; (c) add a paragraph to the documentation
365        for the FullMatch() function.
366    
367     6. The escape sequence \n was being treated as whatever was defined as
368        "newline". Not only was this contrary to the documentation, which states
369        that \n is character 10 (hex 0A), but it also went horribly wrong when
370        "newline" was defined as CRLF. This has been fixed.
371    
372     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
373        was being set to -1 for the "end of line" case (supposedly a value that no
374        character can have). Though this value is never used (the check for end of
375        line is "zero bytes in current character"), it caused compiler complaints.
376        I've changed it to 0xffffffff.
377    
378     8. In pcre_version.c, the version string was being built by a sequence of
379        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
380        string (as it is for production releases) called a macro with an empty
381        argument. The C standard says the result of this is undefined. The gcc
382        compiler treats it as an empty string (which was what was wanted) but it is
383        reported that Visual C gives an error. The source has been hacked around to
384        avoid this problem.
385    
386     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
387        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
388        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
389        of them did).
390    
391    10. Originally, pcretest opened its input and output without "b"; then I was
392        told that "b" was needed in some environments, so it was added for release
393        5.0 to both the input and output. (It makes no difference on Unix-like
394        systems.) Later I was told that it is wrong for the input on Windows. I've
395        now abstracted the modes into two macros, to make it easier to fiddle with
396        them, and removed "b" from the input mode under Windows.
397    
398    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
399    
400    12. Added -help and --help to pcretest as an official way of being reminded
401        of the options.
402    
403    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
404        and pcrecpp.cc because they annoy compilers at high warning levels.
405    
406    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
407    
408    15. Fixed an occurrence of == in configure.ac that should have been = (shell
409        scripts are not C programs :-) and which was not noticed because it works
410        on Linux.
411    
412    16. pcretest is supposed to handle any length of pattern and data line (as one
413        line or as a continued sequence of lines) by extending its input buffer if
414        necessary. This feature was broken for very long pattern lines, leading to
415        a string of junk being passed to pcre_compile() if the pattern was longer
416        than about 50K.
417    
418    17. I have done a major re-factoring of the way pcre_compile() computes the
419        amount of memory needed for a compiled pattern. Previously, there was code
420        that made a preliminary scan of the pattern in order to do this. That was
421        OK when PCRE was new, but as the facilities have expanded, it has become
422        harder and harder to keep it in step with the real compile phase, and there
423        have been a number of bugs (see for example, 4 above). I have now found a
424        cunning way of running the real compile function in a "fake" mode that
425        enables it to compute how much memory it would need, while actually only
426        ever using a few hundred bytes of working memory and without too many
427        tests of the mode. This should make future maintenance and development
428        easier. A side effect of this work is that the limit of 200 on the nesting
429        depth of parentheses has been removed (though this was never a serious
430        limitation, I suspect). However, there is a downside: pcre_compile() now
431        runs more slowly than before (30% or more, depending on the pattern). I
432        hope this isn't a big issue. There is no effect on runtime performance.
433    
434    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
435        newline (only possible for the last line of a file) and it was a
436        pattern that set a locale (followed by /Lsomething), pcretest crashed.
437    
438    19. Added additional timing features to pcretest. (1) The -tm option now times
439        matching only, not compiling. (2) Both -t and -tm can be followed, as a
440        separate command line item, by a number that specifies the number of
441        repeats to use when timing. The default is 50000; this gives better
442        precision, but takes uncomfortably long for very large patterns.
443    
444    20. Extended pcre_study() to be more clever in cases where a branch of a
445        subpattern has no definite first character. For example, (a*|b*)[cd] would
446        previously give no result from pcre_study(). Now it recognizes that the
447        first character must be a, b, c, or d.
448    
449    21. There was an incorrect error "recursive call could loop indefinitely" if
450        a subpattern (or the entire pattern) that was being tested for matching an
451        empty string contained only one non-empty item after a nested subpattern.
452        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
453        incorrectly, because the \d was being skipped in the check.
454    
455    22. The pcretest program now has a new pattern option /B and a command line
456        option -b, which is equivalent to adding /B to every pattern. This causes
457        it to show the compiled bytecode, without the additional information that
458        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
459        is the same as /B/I).
460    
461    23. A new optimization is now able automatically to treat some sequences such
462        as a*b as a*+b. More specifically, if something simple (such as a character
463        or a simple class like \d) has an unlimited quantifier, and is followed by
464        something that cannot possibly match the quantified thing, the quantifier
465        is automatically "possessified".
466    
467    24. A recursive reference to a subpattern whose number was greater than 39
468        went wrong under certain circumstances in UTF-8 mode. This bug could also
469        have affected the operation of pcre_study().
470    
471    25. Realized that a little bit of performance could be had by replacing
472        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
473    
474    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
475    
476    27. Possessive quantifiers such as a++ were previously implemented by turning
477        them into atomic groups such as ($>a+). Now they have their own opcodes,
478        which improves performance. This includes the automatically created ones
479        from 23 above.
480    
481    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
482        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
483        the first matched character to be a colon. This applied both to named and
484        numbered groups.
485    
486    29. The ucpinternal.h header file was missing its idempotency #ifdef.
487    
488    30. I was sent a "project" file called libpcre.a.dev which I understand makes
489        building PCRE on Windows easier, so I have included it in the distribution.
490    
491    31. There is now a check in pcretest against a ridiculously large number being
492        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
493        loop, the loop is abandoned.
494    
495    32. Forward references to subpatterns in conditions such as (?(2)...) where
496        subpattern 2 is defined later cause pcre_compile() to search forwards in
497        the pattern for the relevant set of parentheses. This search went wrong
498        when there were unescaped parentheses in a character class, parentheses
499        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
500    
501    33. "Subroutine" calls and backreferences were previously restricted to
502        referencing subpatterns earlier in the regex. This restriction has now
503        been removed.
504    
505    34. Added a number of extra features that are going to be in Perl 5.10. On the
506        whole, these are just syntactic alternatives for features that PCRE had
507        previously implemented using the Python syntax or my own invention. The
508        other formats are all retained for compatibility.
509    
510        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
511            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
512            also .NET compatible.
513    
514        (b) A recursion or subroutine call to a named group can now be defined as
515            (?&name) as well as (?P>name).
516    
517        (c) A backreference to a named group can now be defined as \k<name> or
518            \k'name' as well as (?P=name). The new forms, as well as being in Perl
519            5.10, are also .NET compatible.
520    
521        (d) A conditional reference to a named group can now use the syntax
522            (?(<name>) or (?('name') as well as (?(name).
523    
524        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
525            groups (named and numbered) that are never evaluated inline, but can be
526            called as "subroutines" from elsewhere. In effect, the DEFINE condition
527            is always false. There may be only one alternative in such a group.
528    
529        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
530            as the simple (?(R). The condition is true only if the most recent
531            recursion is that of the given number or name. It does not search out
532            through the entire recursion stack.
533    
534        (g) The escape \gN or \g{N} has been added, where N is a positive or
535            negative number, specifying an absolute or relative reference.
536    
537    35. Tidied to get rid of some further signed/unsigned compiler warnings and
538        some "unreachable code" warnings.
539    
540    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
541        things, this adds five new scripts.
542    
543    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
544        There were also incompatibilities regarding the handling of \Q..\E inside
545        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
546        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
547    
548    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
549        matches an empty string, and forcibly breaks the loop. There were bugs in
550        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
551        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
552        separate and independent bugs (that affected different cases) have been
553        fixed.
554    
555    39. Refactored the code to abolish the use of different opcodes for small
556        capturing bracket numbers. This is a tidy that I avoided doing when I
557        removed the limit on the number of capturing brackets for 3.5 back in 2001.
558        The new approach is not only tidier, it makes it possible to reduce the
559        memory needed to fix the previous bug (38).
560    
561    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
562        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
563        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
564        mode.
565    
566    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
567        report.
568    
569    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
570        copy construction and assignment in the C++ wrapper.
571    
572    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
573        couple of bugs that could have given wrong results in the "--newline=crlf"
574        case.
575    
576    44. Added a number of casts and did some reorganization of signed/unsigned int
577        variables following suggestions from Dair Grant. Also renamed the variable
578        "this" as "item" because it is a C++ keyword.
579    
580    45. Arranged for dftables to add
581    
582          #include "pcre_internal.h"
583    
584        to pcre_chartables.c because without it, gcc 4.x may remove the array
585        definition from the final binary if PCRE is built into a static library and
586        dead code stripping is activated.
587    
588    46. For an unanchored pattern, if a match attempt fails at the start of a
589        newline sequence, and the newline setting is CRLF or ANY, and the next two
590        characters are CRLF, advance by two characters instead of one.
591    
592    
593    Version 6.7 04-Jul-06
594    ---------------------
595    
596     1. In order to handle tests when input lines are enormously long, pcretest has
597        been re-factored so that it automatically extends its buffers when
598        necessary. The code is crude, but this _is_ just a test program. The
599        default size has been increased from 32K to 50K.
600    
601     2. The code in pcre_study() was using the value of the re argument before
602        testing it for NULL. (Of course, in any sensible call of the function, it
603        won't be NULL.)
604    
605     3. The memmove() emulation function in pcre_internal.h, which is used on
606        systems that lack both memmove() and bcopy() - that is, hardly ever -
607        was missing a "static" storage class specifier.
608    
609     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
610        containing an extended class (one that cannot be represented by a bitmap
611        because it contains high-valued characters or Unicode property items, e.g.
612        [\pZ]). Almost always one would set UTF-8 mode when processing such a
613        pattern, but PCRE should not loop if you do not (it no longer does).
614        [Detail: two cases were found: (a) a repeated subpattern containing an
615        extended class; (b) a recursive reference to a subpattern that followed a
616        previous extended class. It wasn't skipping over the extended class
617        correctly when UTF-8 mode was not set.]
618    
619     5. A negated single-character class was not being recognized as fixed-length
620        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
621        compile error "lookbehind assertion is not fixed length".
622    
623     6. The RunPerlTest auxiliary script was showing an unexpected difference
624        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
625        write a Perl script that can interpret lines of an input file either as
626        byte characters or as UTF-8, which is what "perltest" was being required to
627        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
628        can't do is switch easily at run time between having the "use utf8;" pragma
629        or not. In the end, I fudged it by using the RunPerlTest script to insert
630        "use utf8;" explicitly for the UTF-8 tests.
631    
632     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
633        the end of the subject string, contrary to the documentation and to what
634        Perl does. This was true of both matching functions. Now it matches only at
635        the start of the subject and immediately after *internal* newlines.
636    
637     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
638        a pointer to an int instead of a pointer to an unsigned long int. This
639        caused problems on 64-bit systems.
640    
641     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
642        instance of the 'standard' template library not being so standard".
643    
644    10. There was no check on the number of named subpatterns nor the maximum
645        length of a subpattern name. The product of these values is used to compute
646        the size of the memory block for a compiled pattern. By supplying a very
647        long subpattern name and a large number of named subpatterns, the size
648        computation could be caused to overflow. This is now prevented by limiting
649        the length of names to 32 characters, and the number of named subpatterns
650        to 10,000.
651    
652    11. Subpatterns that are repeated with specific counts have to be replicated in
653        the compiled pattern. The size of memory for this was computed from the
654        length of the subpattern and the repeat count. The latter is limited to
655        65535, but there was no limit on the former, meaning that integer overflow
656        could in principle occur. The compiled length of a repeated subpattern is
657        now limited to 30,000 bytes in order to prevent this.
658    
659    12. Added the optional facility to have named substrings with the same name.
660    
661    13. Added the ability to use a named substring as a condition, using the
662        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
663        are numbers (not recommended). Forward references are permitted.
664    
665    14. Added forward references in named backreferences (if you see what I mean).
666    
667    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
668        pattern could run off the end of the subject. For example, the pattern
669        "(?s)(.{1,5})"8 did this with the subject "ab".
670    
671    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
672        PCRE_CASELESS was set when matching characters that were quantified with ?
673        or *.
674    
675    17. A character class other than a single negated character that had a minimum
676        but no maximum quantifier - for example [ab]{6,} - was not handled
677        correctly by pce_dfa_exec(). It would match only one character.
678    
679    18. A valid (though odd) pattern that looked like a POSIX character
680        class but used an invalid character after [ (for example [[,abc,]]) caused
681        pcre_compile() to give the error "Failed: internal error: code overflow" or
682        in some cases to crash with a glibc free() error. This could even happen if
683        the pattern terminated after [[ but there just happened to be a sequence of
684        letters, a binary zero, and a closing ] in the memory that followed.
685    
686    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
687        over the years. Originally (before any Unicode support), just the bottom 8
688        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
689        output from "man perlunicode" includes this:
690    
691          The regular expression compiler produces polymorphic opcodes.  That
692          is, the pattern adapts to the data and automatically switches to
693          the Unicode character scheme when presented with Unicode data--or
694          instead uses a traditional byte scheme when presented with byte
695          data.
696    
697        Sadly, a wide octal escape does not cause a switch, and in a string with
698        no other multibyte characters, these octal escapes are treated as before.
699        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
700        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
701        Unicode string.
702    
703        I have not perpetrated such confusion in PCRE. Up till now, it took just
704        the bottom 8 bits, as in old Perl. I have now made octal escapes with
705        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
706        translate to the appropriate multibyte character.
707    
708    29. Applied some refactoring to reduce the number of warnings from Microsoft
709        and Borland compilers. This has included removing the fudge introduced
710        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
711        a warning about an unused variable.
712    
713    21. PCRE has not included VT (character 0x0b) in the set of whitespace
714        characters since release 4.0, because Perl (from release 5.004) does not.
715        [Or at least, is documented not to: some releases seem to be in conflict
716        with the documentation.] However, when a pattern was studied with
717        pcre_study() and all its branches started with \s, PCRE still included VT
718        as a possible starting character. Of course, this did no harm; it just
719        caused an unnecessary match attempt.
720    
721    22. Removed a now-redundant internal flag bit that recorded the fact that case
722        dependency changed within the pattern. This was once needed for "required
723        byte" processing, but is no longer used. This recovers a now-scarce options
724        bit. Also moved the least significant internal flag bit to the most-
725        significant bit of the word, which was not previously used (hangover from
726        the days when it was an int rather than a uint) to free up another bit for
727        the future.
728    
729    23. Added support for CRLF line endings as well as CR and LF. As well as the
730        default being selectable at build time, it can now be changed at runtime
731        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
732        specify that it is scanning data with non-default line endings.
733    
734    24. Changed the definition of CXXLINK to make it agree with the definition of
735        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
736    
737    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
738        recursions. This makes a big different to stack usage for some patterns.
739    
740    26. If a subpattern containing a named recursion or subroutine reference such
741        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
742        the space required for the compiled pattern went wrong and gave too small a
743        value. Depending on the environment, this could lead to "Failed: internal
744        error: code overflow at offset 49" or "glibc detected double free or
745        corruption" errors.
746    
747    27. Applied patches from Google (a) to support the new newline modes and (b) to
748        advance over multibyte UTF-8 characters in GlobalReplace.
749    
750    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
751        difference for some implementation of PCRE in some Windows version.
752    
753    29. Added some extra testing facilities to pcretest:
754    
755        \q<number>   in a data line sets the "match limit" value
756        \Q<number>   in a data line sets the "match recursion limt" value
757        -S <number>  sets the stack size, where <number> is in megabytes
758    
759        The -S option isn't available for Windows.
760    
761    
762    Version 6.6 06-Feb-06
763    ---------------------
764    
765     1. Change 16(a) for 6.5 broke things, because PCRE_DATA_SCOPE was not defined
766        in pcreposix.h. I have copied the definition from pcre.h.
767    
768     2. Change 25 for 6.5 broke compilation in a build directory out-of-tree
769        because pcre.h is no longer a built file.
770    
771     3. Added Jeff Friedl's additional debugging patches to pcregrep. These are
772        not normally included in the compiled code.
773    
774    
775  Version 6.5 01-Feb-06  Version 6.5 01-Feb-06
776  ---------------------  ---------------------
777    

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