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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4  Version 8.00 ??-???-??  Version 8.11 10-Oct-2010
5    ------------------------
6    
7    1.  (*THEN) was not working properly if there were untried alternatives prior
8        to it in the current branch. For example, in ((a|b)(*THEN)(*F)|c..) it
9        backtracked to try for "b" instead of moving to the next alternative branch
10        at the same level (in this case, to look for "c"). The Perl documentation
11        is clear that when (*THEN) is backtracked onto, it goes to the "next
12        alternative in the innermost enclosing group".
13    
14    2.  (*COMMIT) was not overriding (*THEN), as it does in Perl. In a pattern
15        such as   (A(*COMMIT)B(*THEN)C|D)  any failure after matching A should
16        result in overall failure. Similarly, (*COMMIT) now overrides (*PRUNE) and
17        (*SKIP), (*SKIP) overrides (*PRUNE) and (*THEN), and (*PRUNE) overrides
18        (*THEN).
19    
20    3.  If \s appeared in a character class, it removed the VT character from
21        the class, even if it had been included by some previous item, for example
22        in [\x00-\xff\s]. (This was a bug related to the fact that VT is not part
23        of \s, but is part of the POSIX "space" class.)
24    
25    4.  A partial match never returns an empty string (because you can always
26        match an empty string at the end of the subject); however the checking for
27        an empty string was starting at the "start of match" point. This has been
28        changed to the "earliest inspected character" point, because the returned
29        data for a partial match starts at this character. This means that, for
30        example, /(?<=abc)def/ gives a partial match for the subject "abc"
31        (previously it gave "no match").
32    
33    5.  Changes have been made to the way PCRE_PARTIAL_HARD affects the matching
34        of $, \z, \Z, \b, and \B. If the match point is at the end of the string,
35        previously a full match would be given. However, setting PCRE_PARTIAL_HARD
36        has an implication that the given string is incomplete (because a partial
37        match is preferred over a full match). For this reason, these items now
38        give a partial match in this situation. [Aside: previously, the one case
39        /t\b/ matched against "cat" with PCRE_PARTIAL_HARD set did return a partial
40        match rather than a full match, which was wrong by the old rules, but is
41        now correct.]
42    
43    6.  There was a bug in the handling of #-introduced comments, recognized when
44        PCRE_EXTENDED is set, when PCRE_NEWLINE_ANY and PCRE_UTF8 were also set.
45        If a UTF-8 multi-byte character included the byte 0x85 (e.g. +U0445, whose
46        UTF-8 encoding is 0xd1,0x85), this was misinterpreted as a newline when
47        scanning for the end of the comment. (*Character* 0x85 is an "any" newline,
48        but *byte* 0x85 is not, in UTF-8 mode). This bug was present in several
49        places in pcre_compile().
50    
51    7.  Related to (6) above, when pcre_compile() was skipping #-introduced
52        comments when looking ahead for named forward references to subpatterns,
53        the only newline sequence it recognized was NL. It now handles newlines
54        according to the set newline convention.
55    
56    8.  SunOS4 doesn't have strerror() or strtoul(); pcregrep dealt with the
57        former, but used strtoul(), whereas pcretest avoided strtoul() but did not
58        cater for a lack of strerror(). These oversights have been fixed.
59    
60    
61    Version 8.10 25-Jun-2010
62    ------------------------
63    
64    1.  Added support for (*MARK:ARG) and for ARG additions to PRUNE, SKIP, and
65        THEN.
66    
67    2.  (*ACCEPT) was not working when inside an atomic group.
68    
69    3.  Inside a character class, \B is treated as a literal by default, but
70        faulted if PCRE_EXTRA is set. This mimics Perl's behaviour (the -w option
71        causes the error). The code is unchanged, but I tidied the documentation.
72    
73    4.  Inside a character class, PCRE always treated \R and \X as literals,
74        whereas Perl faults them if its -w option is set. I have changed PCRE so
75        that it faults them when PCRE_EXTRA is set.
76    
77    5.  Added support for \N, which always matches any character other than
78        newline. (It is the same as "." when PCRE_DOTALL is not set.)
79    
80    6.  When compiling pcregrep with newer versions of gcc which may have
81        FORTIFY_SOURCE set, several warnings "ignoring return value of 'fwrite',
82        declared with attribute warn_unused_result" were given. Just casting the
83        result to (void) does not stop the warnings; a more elaborate fudge is
84        needed. I've used a macro to implement this.
85    
86    7.  Minor change to pcretest.c to avoid a compiler warning.
87    
88    8.  Added four artifical Unicode properties to help with an option to make
89        \s etc use properties (see next item). The new properties are: Xan
90        (alphanumeric), Xsp (Perl space), Xps (POSIX space), and Xwd (word).
91    
92    9.  Added PCRE_UCP to make \b, \d, \s, \w, and certain POSIX character classes
93        use Unicode properties. (*UCP) at the start of a pattern can be used to set
94        this option. Modified pcretest to add /W to test this facility. Added
95        REG_UCP to make it available via the POSIX interface.
96    
97    10. Added --line-buffered to pcregrep.
98    
99    11. In UTF-8 mode, if a pattern that was compiled with PCRE_CASELESS was
100        studied, and the match started with a letter with a code point greater than
101        127 whose first byte was different to the first byte of the other case of
102        the letter, the other case of this starting letter was not recognized
103        (#976).
104    
105    12. If a pattern that was studied started with a repeated Unicode property
106        test, for example, \p{Nd}+, there was the theoretical possibility of
107        setting up an incorrect bitmap of starting bytes, but fortunately it could
108        not have actually happened in practice until change 8 above was made (it
109        added property types that matched character-matching opcodes).
110    
111    13. pcre_study() now recognizes \h, \v, and \R when constructing a bit map of
112        possible starting bytes for non-anchored patterns.
113    
114    14. Extended the "auto-possessify" feature of pcre_compile(). It now recognizes
115        \R, and also a number of cases that involve Unicode properties, both
116        explicit and implicit when PCRE_UCP is set.
117    
118    15. If a repeated Unicode property match (e.g. \p{Lu}*) was used with non-UTF-8
119        input, it could crash or give wrong results if characters with values
120        greater than 0xc0 were present in the subject string. (Detail: it assumed
121        UTF-8 input when processing these items.)
122    
123    16. Added a lot of (int) casts to avoid compiler warnings in systems where
124        size_t is 64-bit (#991).
125    
126    17. Added a check for running out of memory when PCRE is compiled with
127        --disable-stack-for-recursion (#990).
128    
129    18. If the last data line in a file for pcretest does not have a newline on
130        the end, a newline was missing in the output.
131    
132    19. The default pcre_chartables.c file recognizes only ASCII characters (values
133        less than 128) in its various bitmaps. However, there is a facility for
134        generating tables according to the current locale when PCRE is compiled. It
135        turns out that in some environments, 0x85 and 0xa0, which are Unicode space
136        characters, are recognized by isspace() and therefore were getting set in
137        these tables, and indeed these tables seem to approximate to ISO 8859. This
138        caused a problem in UTF-8 mode when pcre_study() was used to create a list
139        of bytes that can start a match. For \s, it was including 0x85 and 0xa0,
140        which of course cannot start UTF-8 characters. I have changed the code so
141        that only real ASCII characters (less than 128) and the correct starting
142        bytes for UTF-8 encodings are set for characters greater than 127 when in
143        UTF-8 mode. (When PCRE_UCP is set - see 9 above - the code is different
144        altogether.)
145    
146    20. Added the /T option to pcretest so as to be able to run tests with non-
147        standard character tables, thus making it possible to include the tests
148        used for 19 above in the standard set of tests.
149    
150    21. A pattern such as (?&t)(?#()(?(DEFINE)(?<t>a)) which has a forward
151        reference to a subpattern the other side of a comment that contains an
152        opening parenthesis caused either an internal compiling error, or a
153        reference to the wrong subpattern.
154    
155    
156    Version 8.02 19-Mar-2010
157    ------------------------
158    
159    1.  The Unicode data tables have been updated to Unicode 5.2.0.
160    
161    2.  Added the option --libs-cpp to pcre-config, but only when C++ support is
162        configured.
163    
164    3.  Updated the licensing terms in the pcregexp.pas file, as agreed with the
165        original author of that file, following a query about its status.
166    
167    4.  On systems that do not have stdint.h (e.g. Solaris), check for and include
168        inttypes.h instead. This fixes a bug that was introduced by change 8.01/8.
169    
170    5.  A pattern such as (?&t)*+(?(DEFINE)(?<t>.)) which has a possessive
171        quantifier applied to a forward-referencing subroutine call, could compile
172        incorrect code or give the error "internal error: previously-checked
173        referenced subpattern not found".
174    
175    6.  Both MS Visual Studio and Symbian OS have problems with initializing
176        variables to point to external functions. For these systems, therefore,
177        pcre_malloc etc. are now initialized to local functions that call the
178        relevant global functions.
179    
180    7.  There were two entries missing in the vectors called coptable and poptable
181        in pcre_dfa_exec.c. This could lead to memory accesses outsize the vectors.
182        I've fixed the data, and added a kludgy way of testing at compile time that
183        the lengths are correct (equal to the number of opcodes).
184    
185    8.  Following on from 7, I added a similar kludge to check the length of the
186        eint vector in pcreposix.c.
187    
188    9.  Error texts for pcre_compile() are held as one long string to avoid too
189        much relocation at load time. To find a text, the string is searched,
190        counting zeros. There was no check for running off the end of the string,
191        which could happen if a new error number was added without updating the
192        string.
193    
194    10. \K gave a compile-time error if it appeared in a lookbehind assersion.
195    
196    11. \K was not working if it appeared in an atomic group or in a group that
197        was called as a "subroutine", or in an assertion. Perl 5.11 documents that
198        \K is "not well defined" if used in an assertion. PCRE now accepts it if
199        the assertion is positive, but not if it is negative.
200    
201    12. Change 11 fortuitously reduced the size of the stack frame used in the
202        "match()" function of pcre_exec.c by one pointer. Forthcoming
203        implementation of support for (*MARK) will need an extra pointer on the
204        stack; I have reserved it now, so that the stack frame size does not
205        decrease.
206    
207    13. A pattern such as (?P<L1>(?P<L2>0)|(?P>L2)(?P>L1)) in which the only other
208        item in branch that calls a recursion is a subroutine call - as in the
209        second branch in the above example - was incorrectly given the compile-
210        time error "recursive call could loop indefinitely" because pcre_compile()
211        was not correctly checking the subroutine for matching a non-empty string.
212    
213    14. The checks for overrunning compiling workspace could trigger after an
214        overrun had occurred. This is a "should never occur" error, but it can be
215        triggered by pathological patterns such as hundreds of nested parentheses.
216        The checks now trigger 100 bytes before the end of the workspace.
217    
218    15. Fix typo in configure.ac: "srtoq" should be "strtoq".
219    
220    
221    Version 8.01 19-Jan-2010
222    ------------------------
223    
224    1.  If a pattern contained a conditional subpattern with only one branch (in
225        particular, this includes all (*DEFINE) patterns), a call to pcre_study()
226        computed the wrong minimum data length (which is of course zero for such
227        subpatterns). This could cause incorrect "no match" results.
228    
229    2.  For patterns such as (?i)a(?-i)b|c where an option setting at the start of
230        the pattern is reset in the first branch, pcre_compile() failed with
231        "internal error: code overflow at offset...". This happened only when
232        the reset was to the original external option setting. (An optimization
233        abstracts leading options settings into an external setting, which was the
234        cause of this.)
235    
236    3.  A pattern such as ^(?!a(*SKIP)b) where a negative assertion contained one
237        of the verbs SKIP, PRUNE, or COMMIT, did not work correctly. When the
238        assertion pattern did not match (meaning that the assertion was true), it
239        was incorrectly treated as false if the SKIP had been reached during the
240        matching. This also applied to assertions used as conditions.
241    
242    4.  If an item that is not supported by pcre_dfa_exec() was encountered in an
243        assertion subpattern, including such a pattern used as a condition,
244        unpredictable results occurred, instead of the error return
245        PCRE_ERROR_DFA_UITEM.
246    
247    5.  The C++ GlobalReplace function was not working like Perl for the special
248        situation when an empty string is matched. It now does the fancy magic
249        stuff that is necessary.
250    
251    6.  In pcre_internal.h, obsolete includes to setjmp.h and stdarg.h have been
252        removed. (These were left over from very, very early versions of PCRE.)
253    
254    7.  Some cosmetic changes to the code to make life easier when compiling it
255        as part of something else:
256    
257        (a) Change DEBUG to PCRE_DEBUG.
258    
259        (b) In pcre_compile(), rename the member of the "branch_chain" structure
260            called "current" as "current_branch", to prevent a collision with the
261            Linux macro when compiled as a kernel module.
262    
263        (c) In pcre_study(), rename the function set_bit() as set_table_bit(), to
264            prevent a collision with the Linux macro when compiled as a kernel
265            module.
266    
267    8.  In pcre_compile() there are some checks for integer overflows that used to
268        cast potentially large values to (double). This has been changed to that
269        when building, a check for int64_t is made, and if it is found, it is used
270        instead, thus avoiding the use of floating point arithmetic. (There is no
271        other use of FP in PCRE.) If int64_t is not found, the fallback is to
272        double.
273    
274    9.  Added two casts to avoid signed/unsigned warnings from VS Studio Express
275        2005 (difference between two addresses compared to an unsigned value).
276    
277    10. Change the standard AC_CHECK_LIB test for libbz2 in configure.ac to a
278        custom one, because of the following reported problem in Windows:
279    
280          - libbz2 uses the Pascal calling convention (WINAPI) for the functions
281              under Win32.
282          - The standard autoconf AC_CHECK_LIB fails to include "bzlib.h",
283              therefore missing the function definition.
284          - The compiler thus generates a "C" signature for the test function.
285          - The linker fails to find the "C" function.
286          - PCRE fails to configure if asked to do so against libbz2.
287    
288    11. When running libtoolize from libtool-2.2.6b as part of autogen.sh, these
289        messages were output:
290    
291          Consider adding `AC_CONFIG_MACRO_DIR([m4])' to configure.ac and
292          rerunning libtoolize, to keep the correct libtool macros in-tree.
293          Consider adding `-I m4' to ACLOCAL_AMFLAGS in Makefile.am.
294    
295        I have done both of these things.
296    
297    12. Although pcre_dfa_exec() does not use nearly as much stack as pcre_exec()
298        most of the time, it *can* run out if it is given a pattern that contains a
299        runaway infinite recursion. I updated the discussion in the pcrestack man
300        page.
301    
302    13. Now that we have gone to the x.xx style of version numbers, the minor
303        version may start with zero. Using 08 or 09 is a bad idea because users
304        might check the value of PCRE_MINOR in their code, and 08 or 09 may be
305        interpreted as invalid octal numbers. I've updated the previous comment in
306        configure.ac, and also added a check that gives an error if 08 or 09 are
307        used.
308    
309    14. Change 8.00/11 was not quite complete: code had been accidentally omitted,
310        causing partial matching to fail when the end of the subject matched \W
311        in a UTF-8 pattern where \W was quantified with a minimum of 3.
312    
313    15. There were some discrepancies between the declarations in pcre_internal.h
314        of _pcre_is_newline(), _pcre_was_newline(), and _pcre_valid_utf8() and
315        their definitions. The declarations used "const uschar *" and the
316        definitions used USPTR. Even though USPTR is normally defined as "const
317        unsigned char *" (and uschar is typedeffed as "unsigned char"), it was
318        reported that: "This difference in casting confuses some C++ compilers, for
319        example, SunCC recognizes above declarations as different functions and
320        generates broken code for hbpcre." I have changed the declarations to use
321        USPTR.
322    
323    16. GNU libtool is named differently on some systems. The autogen.sh script now
324        tries several variants such as glibtoolize (MacOSX) and libtoolize1x
325        (FreeBSD).
326    
327    17. Applied Craig's patch that fixes an HP aCC compile error in pcre 8.00
328        (strtoXX undefined when compiling pcrecpp.cc). The patch contains this
329        comment: "Figure out how to create a longlong from a string: strtoll and
330        equivalent. It's not enough to call AC_CHECK_FUNCS: hpux has a strtoll, for
331        instance, but it only takes 2 args instead of 3!"
332    
333    18. A subtle bug concerned with back references has been fixed by a change of
334        specification, with a corresponding code fix. A pattern such as
335        ^(xa|=?\1a)+$ which contains a back reference inside the group to which it
336        refers, was giving matches when it shouldn't. For example, xa=xaaa would
337        match that pattern. Interestingly, Perl (at least up to 5.11.3) has the
338        same bug. Such groups have to be quantified to be useful, or contained
339        inside another quantified group. (If there's no repetition, the reference
340        can never match.) The problem arises because, having left the group and
341        moved on to the rest of the pattern, a later failure that backtracks into
342        the group uses the captured value from the final iteration of the group
343        rather than the correct earlier one. I have fixed this in PCRE by forcing
344        any group that contains a reference to itself to be an atomic group; that
345        is, there cannot be any backtracking into it once it has completed. This is
346        similar to recursive and subroutine calls.
347    
348    
349    Version 8.00 19-Oct-09
350  ----------------------  ----------------------
351    
352  1.  The table for translating pcre_compile() error codes into POSIX error codes  1.  The table for translating pcre_compile() error codes into POSIX error codes
353      was out-of-date, and there was no check on the pcre_compile() error code      was out-of-date, and there was no check on the pcre_compile() error code
354      being within the table. This could lead to an OK return being given in      being within the table. This could lead to an OK return being given in
355      error.      error.
356    
357    2.  Changed the call to open a subject file in pcregrep from fopen(pathname,
358        "r") to fopen(pathname, "rb"), which fixed a problem with some of the tests
359        in a Windows environment.
360    
361    3.  The pcregrep --count option prints the count for each file even when it is
362        zero, as does GNU grep. However, pcregrep was also printing all files when
363        --files-with-matches was added. Now, when both options are given, it prints
364        counts only for those files that have at least one match. (GNU grep just
365        prints the file name in this circumstance, but including the count seems
366        more useful - otherwise, why use --count?) Also ensured that the
367        combination -clh just lists non-zero counts, with no names.
368    
369    4.  The long form of the pcregrep -F option was incorrectly implemented as
370        --fixed_strings instead of --fixed-strings. This is an incompatible change,
371        but it seems right to fix it, and I didn't think it was worth preserving
372        the old behaviour.
373    
374    5.  The command line items --regex=pattern and --regexp=pattern were not
375        recognized by pcregrep, which required --regex pattern or --regexp pattern
376        (with a space rather than an '='). The man page documented the '=' forms,
377        which are compatible with GNU grep; these now work.
378    
379    6.  No libpcreposix.pc file was created for pkg-config; there was just
380        libpcre.pc and libpcrecpp.pc. The omission has been rectified.
381    
382    7.  Added #ifndef SUPPORT_UCP into the pcre_ucd.c module, to reduce its size
383        when UCP support is not needed, by modifying the Python script that
384        generates it from Unicode data files. This should not matter if the module
385        is correctly used as a library, but I received one complaint about 50K of
386        unwanted data. My guess is that the person linked everything into his
387        program rather than using a library. Anyway, it does no harm.
388    
389    8.  A pattern such as /\x{123}{2,2}+/8 was incorrectly compiled; the trigger
390        was a minimum greater than 1 for a wide character in a possessive
391        repetition. The same bug could also affect patterns like /(\x{ff}{0,2})*/8
392        which had an unlimited repeat of a nested, fixed maximum repeat of a wide
393        character. Chaos in the form of incorrect output or a compiling loop could
394        result.
395    
396    9.  The restrictions on what a pattern can contain when partial matching is
397        requested for pcre_exec() have been removed. All patterns can now be
398        partially matched by this function. In addition, if there are at least two
399        slots in the offset vector, the offset of the earliest inspected character
400        for the match and the offset of the end of the subject are set in them when
401        PCRE_ERROR_PARTIAL is returned.
402    
403    10. Partial matching has been split into two forms: PCRE_PARTIAL_SOFT, which is
404        synonymous with PCRE_PARTIAL, for backwards compatibility, and
405        PCRE_PARTIAL_HARD, which causes a partial match to supersede a full match,
406        and may be more useful for multi-segment matching.
407    
408    11. Partial matching with pcre_exec() is now more intuitive. A partial match
409        used to be given if ever the end of the subject was reached; now it is
410        given only if matching could not proceed because another character was
411        needed. This makes a difference in some odd cases such as Z(*FAIL) with the
412        string "Z", which now yields "no match" instead of "partial match". In the
413        case of pcre_dfa_exec(), "no match" is given if every matching path for the
414        final character ended with (*FAIL).
415    
416    12. Restarting a match using pcre_dfa_exec() after a partial match did not work
417        if the pattern had a "must contain" character that was already found in the
418        earlier partial match, unless partial matching was again requested. For
419        example, with the pattern /dog.(body)?/, the "must contain" character is
420        "g". If the first part-match was for the string "dog", restarting with
421        "sbody" failed. This bug has been fixed.
422    
423    13. The string returned by pcre_dfa_exec() after a partial match has been
424        changed so that it starts at the first inspected character rather than the
425        first character of the match. This makes a difference only if the pattern
426        starts with a lookbehind assertion or \b or \B (\K is not supported by
427        pcre_dfa_exec()). It's an incompatible change, but it makes the two
428        matching functions compatible, and I think it's the right thing to do.
429    
430    14. Added a pcredemo man page, created automatically from the pcredemo.c file,
431        so that the demonstration program is easily available in environments where
432        PCRE has not been installed from source.
433    
434    15. Arranged to add -DPCRE_STATIC to cflags in libpcre.pc, libpcreposix.cp,
435        libpcrecpp.pc and pcre-config when PCRE is not compiled as a shared
436        library.
437    
438    16. Added REG_UNGREEDY to the pcreposix interface, at the request of a user.
439        It maps to PCRE_UNGREEDY. It is not, of course, POSIX-compatible, but it
440        is not the first non-POSIX option to be added. Clearly some people find
441        these options useful.
442    
443    17. If a caller to the POSIX matching function regexec() passes a non-zero
444        value for nmatch with a NULL value for pmatch, the value of
445        nmatch is forced to zero.
446    
447    18. RunGrepTest did not have a test for the availability of the -u option of
448        the diff command, as RunTest does. It now checks in the same way as
449        RunTest, and also checks for the -b option.
450    
451    19. If an odd number of negated classes containing just a single character
452        interposed, within parentheses, between a forward reference to a named
453        subpattern and the definition of the subpattern, compilation crashed with
454        an internal error, complaining that it could not find the referenced
455        subpattern. An example of a crashing pattern is /(?&A)(([^m])(?<A>))/.
456        [The bug was that it was starting one character too far in when skipping
457        over the character class, thus treating the ] as data rather than
458        terminating the class. This meant it could skip too much.]
459    
460    20. Added PCRE_NOTEMPTY_ATSTART in order to be able to correctly implement the
461        /g option in pcretest when the pattern contains \K, which makes it possible
462        to have an empty string match not at the start, even when the pattern is
463        anchored. Updated pcretest and pcredemo to use this option.
464    
465    21. If the maximum number of capturing subpatterns in a recursion was greater
466        than the maximum at the outer level, the higher number was returned, but
467        with unset values at the outer level. The correct (outer level) value is
468        now given.
469    
470    22. If (*ACCEPT) appeared inside capturing parentheses, previous releases of
471        PCRE did not set those parentheses (unlike Perl). I have now found a way to
472        make it do so. The string so far is captured, making this feature
473        compatible with Perl.
474    
475    23. The tests have been re-organized, adding tests 11 and 12, to make it
476        possible to check the Perl 5.10 features against Perl 5.10.
477    
478    24. Perl 5.10 allows subroutine calls in lookbehinds, as long as the subroutine
479        pattern matches a fixed length string. PCRE did not allow this; now it
480        does. Neither allows recursion.
481    
482    25. I finally figured out how to implement a request to provide the minimum
483        length of subject string that was needed in order to match a given pattern.
484        (It was back references and recursion that I had previously got hung up
485        on.) This code has now been added to pcre_study(); it finds a lower bound
486        to the length of subject needed. It is not necessarily the greatest lower
487        bound, but using it to avoid searching strings that are too short does give
488        some useful speed-ups. The value is available to calling programs via
489        pcre_fullinfo().
490    
491    26. While implementing 25, I discovered to my embarrassment that pcretest had
492        not been passing the result of pcre_study() to pcre_dfa_exec(), so the
493        study optimizations had never been tested with that matching function.
494        Oops. What is worse, even when it was passed study data, there was a bug in
495        pcre_dfa_exec() that meant it never actually used it. Double oops. There
496        were also very few tests of studied patterns with pcre_dfa_exec().
497    
498    27. If (?| is used to create subpatterns with duplicate numbers, they are now
499        allowed to have the same name, even if PCRE_DUPNAMES is not set. However,
500        on the other side of the coin, they are no longer allowed to have different
501        names, because these cannot be distinguished in PCRE, and this has caused
502        confusion. (This is a difference from Perl.)
503    
504    28. When duplicate subpattern names are present (necessarily with different
505        numbers, as required by 27 above), and a test is made by name in a
506        conditional pattern, either for a subpattern having been matched, or for
507        recursion in such a pattern, all the associated numbered subpatterns are
508        tested, and the overall condition is true if the condition is true for any
509        one of them. This is the way Perl works, and is also more like the way
510        testing by number works.
511    
512    
513  Version 7.9 11-Apr-09  Version 7.9 11-Apr-09
514  ---------------------  ---------------------

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