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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
4  Version 8.00 ??-???-??  Version 8.11 10-Oct-2010
5    ------------------------
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".
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).
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.)
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").
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.]
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().
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.
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.
60    9.  Added --match-limit and --recursion-limit to pcregrep.
62    10. Added two casts needed to build with Visual Studio when NO_RECURSE is set.
64    11. When the -o option was used, pcregrep was setting a return code of 1, even
65        when matches were found, and --line-buffered was not being honoured.
67    12. Added an optional parentheses number to the -o and --only-matching options
68        of pcregrep.
70    13. Imitating Perl's /g action for multiple matches is tricky when the pattern
71        can match an empty string. The code to do it in pcretest and pcredemo
72        needed fixing:
74        (a) When the newline convention was "crlf", pcretest got it wrong, skipping
75            only one byte after an empty string match just before CRLF (this case
76            just got forgotten; "any" and "anycrlf" were OK).
78        (b) The pcretest code also had a bug, causing it to loop forever in UTF-8
79            mode when an empty string match preceded an ASCII character followed by
80            a non-ASCII character. (The code for advancing by one character rather
81            than one byte was nonsense.)
83        (c) The pcredemo.c sample program did not have any code at all to handle
84            the cases when CRLF is a valid newline sequence.
86    14. Neither pcre_exec() nor pcre_dfa_exec() was checking that the value given
87        as a starting offset was within the subject string. There is now a new
88        error, PCRE_ERROR_BADOFFSET, which is returned if the starting offset is
89        negative or greater than the length of the string. In order to test this,
90        pcretest is extended to allow the setting of negative starting offsets.
92    15. In both pcre_exec() and pcre_dfa_exec() the code for checking that the
93        starting offset points to the beginning of a UTF-8 character was
94        unnecessarily clumsy. I tidied it up.
96    16. Added PCRE_ERROR_SHORTUTF8 to make it possible to distinguish between a
97        bad UTF-8 sequence and one that is incomplete.
99    17. Nobody had reported that the --include_dir option, which was added in
100        release 7.7 should have been called --include-dir (hyphen, not underscore)
101        for compatibility with GNU grep. I have changed it to --include-dir, but
102        left --include_dir as an undocumented synonym, and the same for
103        --exclude-dir, though that is not available in GNU grep, at least as of
104        release 2.5.4.
107    Version 8.10 25-Jun-2010
108    ------------------------
110    1.  Added support for (*MARK:ARG) and for ARG additions to PRUNE, SKIP, and
111        THEN.
113    2.  (*ACCEPT) was not working when inside an atomic group.
115    3.  Inside a character class, \B is treated as a literal by default, but
116        faulted if PCRE_EXTRA is set. This mimics Perl's behaviour (the -w option
117        causes the error). The code is unchanged, but I tidied the documentation.
119    4.  Inside a character class, PCRE always treated \R and \X as literals,
120        whereas Perl faults them if its -w option is set. I have changed PCRE so
121        that it faults them when PCRE_EXTRA is set.
123    5.  Added support for \N, which always matches any character other than
124        newline. (It is the same as "." when PCRE_DOTALL is not set.)
126    6.  When compiling pcregrep with newer versions of gcc which may have
127        FORTIFY_SOURCE set, several warnings "ignoring return value of 'fwrite',
128        declared with attribute warn_unused_result" were given. Just casting the
129        result to (void) does not stop the warnings; a more elaborate fudge is
130        needed. I've used a macro to implement this.
132    7.  Minor change to pcretest.c to avoid a compiler warning.
134    8.  Added four artifical Unicode properties to help with an option to make
135        \s etc use properties (see next item). The new properties are: Xan
136        (alphanumeric), Xsp (Perl space), Xps (POSIX space), and Xwd (word).
138    9.  Added PCRE_UCP to make \b, \d, \s, \w, and certain POSIX character classes
139        use Unicode properties. (*UCP) at the start of a pattern can be used to set
140        this option. Modified pcretest to add /W to test this facility. Added
141        REG_UCP to make it available via the POSIX interface.
143    10. Added --line-buffered to pcregrep.
145    11. In UTF-8 mode, if a pattern that was compiled with PCRE_CASELESS was
146        studied, and the match started with a letter with a code point greater than
147        127 whose first byte was different to the first byte of the other case of
148        the letter, the other case of this starting letter was not recognized
149        (#976).
151    12. If a pattern that was studied started with a repeated Unicode property
152        test, for example, \p{Nd}+, there was the theoretical possibility of
153        setting up an incorrect bitmap of starting bytes, but fortunately it could
154        not have actually happened in practice until change 8 above was made (it
155        added property types that matched character-matching opcodes).
157    13. pcre_study() now recognizes \h, \v, and \R when constructing a bit map of
158        possible starting bytes for non-anchored patterns.
160    14. Extended the "auto-possessify" feature of pcre_compile(). It now recognizes
161        \R, and also a number of cases that involve Unicode properties, both
162        explicit and implicit when PCRE_UCP is set.
164    15. If a repeated Unicode property match (e.g. \p{Lu}*) was used with non-UTF-8
165        input, it could crash or give wrong results if characters with values
166        greater than 0xc0 were present in the subject string. (Detail: it assumed
167        UTF-8 input when processing these items.)
169    16. Added a lot of (int) casts to avoid compiler warnings in systems where
170        size_t is 64-bit (#991).
172    17. Added a check for running out of memory when PCRE is compiled with
173        --disable-stack-for-recursion (#990).
175    18. If the last data line in a file for pcretest does not have a newline on
176        the end, a newline was missing in the output.
178    19. The default pcre_chartables.c file recognizes only ASCII characters (values
179        less than 128) in its various bitmaps. However, there is a facility for
180        generating tables according to the current locale when PCRE is compiled. It
181        turns out that in some environments, 0x85 and 0xa0, which are Unicode space
182        characters, are recognized by isspace() and therefore were getting set in
183        these tables, and indeed these tables seem to approximate to ISO 8859. This
184        caused a problem in UTF-8 mode when pcre_study() was used to create a list
185        of bytes that can start a match. For \s, it was including 0x85 and 0xa0,
186        which of course cannot start UTF-8 characters. I have changed the code so
187        that only real ASCII characters (less than 128) and the correct starting
188        bytes for UTF-8 encodings are set for characters greater than 127 when in
189        UTF-8 mode. (When PCRE_UCP is set - see 9 above - the code is different
190        altogether.)
192    20. Added the /T option to pcretest so as to be able to run tests with non-
193        standard character tables, thus making it possible to include the tests
194        used for 19 above in the standard set of tests.
196    21. A pattern such as (?&t)(?#()(?(DEFINE)(?<t>a)) which has a forward
197        reference to a subpattern the other side of a comment that contains an
198        opening parenthesis caused either an internal compiling error, or a
199        reference to the wrong subpattern.
202    Version 8.02 19-Mar-2010
203    ------------------------
205    1.  The Unicode data tables have been updated to Unicode 5.2.0.
207    2.  Added the option --libs-cpp to pcre-config, but only when C++ support is
208        configured.
210    3.  Updated the licensing terms in the pcregexp.pas file, as agreed with the
211        original author of that file, following a query about its status.
213    4.  On systems that do not have stdint.h (e.g. Solaris), check for and include
214        inttypes.h instead. This fixes a bug that was introduced by change 8.01/8.
216    5.  A pattern such as (?&t)*+(?(DEFINE)(?<t>.)) which has a possessive
217        quantifier applied to a forward-referencing subroutine call, could compile
218        incorrect code or give the error "internal error: previously-checked
219        referenced subpattern not found".
221    6.  Both MS Visual Studio and Symbian OS have problems with initializing
222        variables to point to external functions. For these systems, therefore,
223        pcre_malloc etc. are now initialized to local functions that call the
224        relevant global functions.
226    7.  There were two entries missing in the vectors called coptable and poptable
227        in pcre_dfa_exec.c. This could lead to memory accesses outsize the vectors.
228        I've fixed the data, and added a kludgy way of testing at compile time that
229        the lengths are correct (equal to the number of opcodes).
231    8.  Following on from 7, I added a similar kludge to check the length of the
232        eint vector in pcreposix.c.
234    9.  Error texts for pcre_compile() are held as one long string to avoid too
235        much relocation at load time. To find a text, the string is searched,
236        counting zeros. There was no check for running off the end of the string,
237        which could happen if a new error number was added without updating the
238        string.
240    10. \K gave a compile-time error if it appeared in a lookbehind assersion.
242    11. \K was not working if it appeared in an atomic group or in a group that
243        was called as a "subroutine", or in an assertion. Perl 5.11 documents that
244        \K is "not well defined" if used in an assertion. PCRE now accepts it if
245        the assertion is positive, but not if it is negative.
247    12. Change 11 fortuitously reduced the size of the stack frame used in the
248        "match()" function of pcre_exec.c by one pointer. Forthcoming
249        implementation of support for (*MARK) will need an extra pointer on the
250        stack; I have reserved it now, so that the stack frame size does not
251        decrease.
253    13. A pattern such as (?P<L1>(?P<L2>0)|(?P>L2)(?P>L1)) in which the only other
254        item in branch that calls a recursion is a subroutine call - as in the
255        second branch in the above example - was incorrectly given the compile-
256        time error "recursive call could loop indefinitely" because pcre_compile()
257        was not correctly checking the subroutine for matching a non-empty string.
259    14. The checks for overrunning compiling workspace could trigger after an
260        overrun had occurred. This is a "should never occur" error, but it can be
261        triggered by pathological patterns such as hundreds of nested parentheses.
262        The checks now trigger 100 bytes before the end of the workspace.
264    15. Fix typo in configure.ac: "srtoq" should be "strtoq".
267    Version 8.01 19-Jan-2010
268    ------------------------
270    1.  If a pattern contained a conditional subpattern with only one branch (in
271        particular, this includes all (*DEFINE) patterns), a call to pcre_study()
272        computed the wrong minimum data length (which is of course zero for such
273        subpatterns). This could cause incorrect "no match" results.
275    2.  For patterns such as (?i)a(?-i)b|c where an option setting at the start of
276        the pattern is reset in the first branch, pcre_compile() failed with
277        "internal error: code overflow at offset...". This happened only when
278        the reset was to the original external option setting. (An optimization
279        abstracts leading options settings into an external setting, which was the
280        cause of this.)
282    3.  A pattern such as ^(?!a(*SKIP)b) where a negative assertion contained one
283        of the verbs SKIP, PRUNE, or COMMIT, did not work correctly. When the
284        assertion pattern did not match (meaning that the assertion was true), it
285        was incorrectly treated as false if the SKIP had been reached during the
286        matching. This also applied to assertions used as conditions.
288    4.  If an item that is not supported by pcre_dfa_exec() was encountered in an
289        assertion subpattern, including such a pattern used as a condition,
290        unpredictable results occurred, instead of the error return
293    5.  The C++ GlobalReplace function was not working like Perl for the special
294        situation when an empty string is matched. It now does the fancy magic
295        stuff that is necessary.
297    6.  In pcre_internal.h, obsolete includes to setjmp.h and stdarg.h have been
298        removed. (These were left over from very, very early versions of PCRE.)
300    7.  Some cosmetic changes to the code to make life easier when compiling it
301        as part of something else:
303        (a) Change DEBUG to PCRE_DEBUG.
305        (b) In pcre_compile(), rename the member of the "branch_chain" structure
306            called "current" as "current_branch", to prevent a collision with the
307            Linux macro when compiled as a kernel module.
309        (c) In pcre_study(), rename the function set_bit() as set_table_bit(), to
310            prevent a collision with the Linux macro when compiled as a kernel
311            module.
313    8.  In pcre_compile() there are some checks for integer overflows that used to
314        cast potentially large values to (double). This has been changed to that
315        when building, a check for int64_t is made, and if it is found, it is used
316        instead, thus avoiding the use of floating point arithmetic. (There is no
317        other use of FP in PCRE.) If int64_t is not found, the fallback is to
318        double.
320    9.  Added two casts to avoid signed/unsigned warnings from VS Studio Express
321        2005 (difference between two addresses compared to an unsigned value).
323    10. Change the standard AC_CHECK_LIB test for libbz2 in configure.ac to a
324        custom one, because of the following reported problem in Windows:
326          - libbz2 uses the Pascal calling convention (WINAPI) for the functions
327              under Win32.
328          - The standard autoconf AC_CHECK_LIB fails to include "bzlib.h",
329              therefore missing the function definition.
330          - The compiler thus generates a "C" signature for the test function.
331          - The linker fails to find the "C" function.
332          - PCRE fails to configure if asked to do so against libbz2.
334    11. When running libtoolize from libtool-2.2.6b as part of autogen.sh, these
335        messages were output:
337          Consider adding `AC_CONFIG_MACRO_DIR([m4])' to configure.ac and
338          rerunning libtoolize, to keep the correct libtool macros in-tree.
339          Consider adding `-I m4' to ACLOCAL_AMFLAGS in Makefile.am.
341        I have done both of these things.
343    12. Although pcre_dfa_exec() does not use nearly as much stack as pcre_exec()
344        most of the time, it *can* run out if it is given a pattern that contains a
345        runaway infinite recursion. I updated the discussion in the pcrestack man
346        page.
348    13. Now that we have gone to the x.xx style of version numbers, the minor
349        version may start with zero. Using 08 or 09 is a bad idea because users
350        might check the value of PCRE_MINOR in their code, and 08 or 09 may be
351        interpreted as invalid octal numbers. I've updated the previous comment in
352        configure.ac, and also added a check that gives an error if 08 or 09 are
353        used.
355    14. Change 8.00/11 was not quite complete: code had been accidentally omitted,
356        causing partial matching to fail when the end of the subject matched \W
357        in a UTF-8 pattern where \W was quantified with a minimum of 3.
359    15. There were some discrepancies between the declarations in pcre_internal.h
360        of _pcre_is_newline(), _pcre_was_newline(), and _pcre_valid_utf8() and
361        their definitions. The declarations used "const uschar *" and the
362        definitions used USPTR. Even though USPTR is normally defined as "const
363        unsigned char *" (and uschar is typedeffed as "unsigned char"), it was
364        reported that: "This difference in casting confuses some C++ compilers, for
365        example, SunCC recognizes above declarations as different functions and
366        generates broken code for hbpcre." I have changed the declarations to use
367        USPTR.
369    16. GNU libtool is named differently on some systems. The autogen.sh script now
370        tries several variants such as glibtoolize (MacOSX) and libtoolize1x
371        (FreeBSD).
373    17. Applied Craig's patch that fixes an HP aCC compile error in pcre 8.00
374        (strtoXX undefined when compiling pcrecpp.cc). The patch contains this
375        comment: "Figure out how to create a longlong from a string: strtoll and
376        equivalent. It's not enough to call AC_CHECK_FUNCS: hpux has a strtoll, for
377        instance, but it only takes 2 args instead of 3!"
379    18. A subtle bug concerned with back references has been fixed by a change of
380        specification, with a corresponding code fix. A pattern such as
381        ^(xa|=?\1a)+$ which contains a back reference inside the group to which it
382        refers, was giving matches when it shouldn't. For example, xa=xaaa would
383        match that pattern. Interestingly, Perl (at least up to 5.11.3) has the
384        same bug. Such groups have to be quantified to be useful, or contained
385        inside another quantified group. (If there's no repetition, the reference
386        can never match.) The problem arises because, having left the group and
387        moved on to the rest of the pattern, a later failure that backtracks into
388        the group uses the captured value from the final iteration of the group
389        rather than the correct earlier one. I have fixed this in PCRE by forcing
390        any group that contains a reference to itself to be an atomic group; that
391        is, there cannot be any backtracking into it once it has completed. This is
392        similar to recursive and subroutine calls.
395    Version 8.00 19-Oct-09
396  ----------------------  ----------------------
398  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
399      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
400      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
401      error.      error.
403  2.  Changed the call to open a subject file in pcregrep from fopen(pathname,  2.  Changed the call to open a subject file in pcregrep from fopen(pathname,
404      "r") to fopen(pathname, "rb"), which fixed a problem with some of the tests      "r") to fopen(pathname, "rb"), which fixed a problem with some of the tests
405      in a Windows environment.      in a Windows environment.
407  3.  The pcregrep --count option prints the count for each file even when it is  3.  The pcregrep --count option prints the count for each file even when it is
408      zero, as does GNU grep. However, pcregrep was also printing all files when      zero, as does GNU grep. However, pcregrep was also printing all files when
409      --files-with-matches was added. Now, when both options are given, it prints      --files-with-matches was added. Now, when both options are given, it prints
410      counts only for those files that have at least one match. (GNU grep just      counts only for those files that have at least one match. (GNU grep just
411      prints the file name in this circumstance, but including the count seems      prints the file name in this circumstance, but including the count seems
412      more useful - otherwise, why use --count?) Also ensured that the      more useful - otherwise, why use --count?) Also ensured that the
413      combination -clh just lists non-zero counts, with no names.      combination -clh just lists non-zero counts, with no names.
415  4.  The long form of the pcregrep -F option was incorrectly implemented as  4.  The long form of the pcregrep -F option was incorrectly implemented as
416      --fixed_strings instead of --fixed-strings. This is an incompatible change,      --fixed_strings instead of --fixed-strings. This is an incompatible change,
417      but it seems right to fix it, and I didn't think it was worth preserving      but it seems right to fix it, and I didn't think it was worth preserving
418      the old behaviour.      the old behaviour.
420  5.  The command line items --regex=pattern and --regexp=pattern were not  5.  The command line items --regex=pattern and --regexp=pattern were not
421      recognized by pcregrep, which required --regex pattern or --regexp pattern      recognized by pcregrep, which required --regex pattern or --regexp pattern
422      (with a space rather than an '='). The man page documented the '=' forms,      (with a space rather than an '='). The man page documented the '=' forms,
423      which are compatible with GNU grep; these now work.      which are compatible with GNU grep; these now work.
425    6.  No libpcreposix.pc file was created for pkg-config; there was just
426        libpcre.pc and libpcrecpp.pc. The omission has been rectified.
428    7.  Added #ifndef SUPPORT_UCP into the pcre_ucd.c module, to reduce its size
429        when UCP support is not needed, by modifying the Python script that
430        generates it from Unicode data files. This should not matter if the module
431        is correctly used as a library, but I received one complaint about 50K of
432        unwanted data. My guess is that the person linked everything into his
433        program rather than using a library. Anyway, it does no harm.
435    8.  A pattern such as /\x{123}{2,2}+/8 was incorrectly compiled; the trigger
436        was a minimum greater than 1 for a wide character in a possessive
437        repetition. The same bug could also affect patterns like /(\x{ff}{0,2})*/8
438        which had an unlimited repeat of a nested, fixed maximum repeat of a wide
439        character. Chaos in the form of incorrect output or a compiling loop could
440        result.
442    9.  The restrictions on what a pattern can contain when partial matching is
443        requested for pcre_exec() have been removed. All patterns can now be
444        partially matched by this function. In addition, if there are at least two
445        slots in the offset vector, the offset of the earliest inspected character
446        for the match and the offset of the end of the subject are set in them when
447        PCRE_ERROR_PARTIAL is returned.
449    10. Partial matching has been split into two forms: PCRE_PARTIAL_SOFT, which is
450        synonymous with PCRE_PARTIAL, for backwards compatibility, and
451        PCRE_PARTIAL_HARD, which causes a partial match to supersede a full match,
452        and may be more useful for multi-segment matching.
454    11. Partial matching with pcre_exec() is now more intuitive. A partial match
455        used to be given if ever the end of the subject was reached; now it is
456        given only if matching could not proceed because another character was
457        needed. This makes a difference in some odd cases such as Z(*FAIL) with the
458        string "Z", which now yields "no match" instead of "partial match". In the
459        case of pcre_dfa_exec(), "no match" is given if every matching path for the
460        final character ended with (*FAIL).
462    12. Restarting a match using pcre_dfa_exec() after a partial match did not work
463        if the pattern had a "must contain" character that was already found in the
464        earlier partial match, unless partial matching was again requested. For
465        example, with the pattern /dog.(body)?/, the "must contain" character is
466        "g". If the first part-match was for the string "dog", restarting with
467        "sbody" failed. This bug has been fixed.
469    13. The string returned by pcre_dfa_exec() after a partial match has been
470        changed so that it starts at the first inspected character rather than the
471        first character of the match. This makes a difference only if the pattern
472        starts with a lookbehind assertion or \b or \B (\K is not supported by
473        pcre_dfa_exec()). It's an incompatible change, but it makes the two
474        matching functions compatible, and I think it's the right thing to do.
476    14. Added a pcredemo man page, created automatically from the pcredemo.c file,
477        so that the demonstration program is easily available in environments where
478        PCRE has not been installed from source.
480    15. Arranged to add -DPCRE_STATIC to cflags in libpcre.pc, libpcreposix.cp,
481        libpcrecpp.pc and pcre-config when PCRE is not compiled as a shared
482        library.
484    16. Added REG_UNGREEDY to the pcreposix interface, at the request of a user.
485        It maps to PCRE_UNGREEDY. It is not, of course, POSIX-compatible, but it
486        is not the first non-POSIX option to be added. Clearly some people find
487        these options useful.
489    17. If a caller to the POSIX matching function regexec() passes a non-zero
490        value for nmatch with a NULL value for pmatch, the value of
491        nmatch is forced to zero.
493    18. RunGrepTest did not have a test for the availability of the -u option of
494        the diff command, as RunTest does. It now checks in the same way as
495        RunTest, and also checks for the -b option.
497    19. If an odd number of negated classes containing just a single character
498        interposed, within parentheses, between a forward reference to a named
499        subpattern and the definition of the subpattern, compilation crashed with
500        an internal error, complaining that it could not find the referenced
501        subpattern. An example of a crashing pattern is /(?&A)(([^m])(?<A>))/.
502        [The bug was that it was starting one character too far in when skipping
503        over the character class, thus treating the ] as data rather than
504        terminating the class. This meant it could skip too much.]
506    20. Added PCRE_NOTEMPTY_ATSTART in order to be able to correctly implement the
507        /g option in pcretest when the pattern contains \K, which makes it possible
508        to have an empty string match not at the start, even when the pattern is
509        anchored. Updated pcretest and pcredemo to use this option.
511    21. If the maximum number of capturing subpatterns in a recursion was greater
512        than the maximum at the outer level, the higher number was returned, but
513        with unset values at the outer level. The correct (outer level) value is
514        now given.
516    22. If (*ACCEPT) appeared inside capturing parentheses, previous releases of
517        PCRE did not set those parentheses (unlike Perl). I have now found a way to
518        make it do so. The string so far is captured, making this feature
519        compatible with Perl.
521    23. The tests have been re-organized, adding tests 11 and 12, to make it
522        possible to check the Perl 5.10 features against Perl 5.10.
524    24. Perl 5.10 allows subroutine calls in lookbehinds, as long as the subroutine
525        pattern matches a fixed length string. PCRE did not allow this; now it
526        does. Neither allows recursion.
528    25. I finally figured out how to implement a request to provide the minimum
529        length of subject string that was needed in order to match a given pattern.
530        (It was back references and recursion that I had previously got hung up
531        on.) This code has now been added to pcre_study(); it finds a lower bound
532        to the length of subject needed. It is not necessarily the greatest lower
533        bound, but using it to avoid searching strings that are too short does give
534        some useful speed-ups. The value is available to calling programs via
535        pcre_fullinfo().
537    26. While implementing 25, I discovered to my embarrassment that pcretest had
538        not been passing the result of pcre_study() to pcre_dfa_exec(), so the
539        study optimizations had never been tested with that matching function.
540        Oops. What is worse, even when it was passed study data, there was a bug in
541        pcre_dfa_exec() that meant it never actually used it. Double oops. There
542        were also very few tests of studied patterns with pcre_dfa_exec().
544    27. If (?| is used to create subpatterns with duplicate numbers, they are now
545        allowed to have the same name, even if PCRE_DUPNAMES is not set. However,
546        on the other side of the coin, they are no longer allowed to have different
547        names, because these cannot be distinguished in PCRE, and this has caused
548        confusion. (This is a difference from Perl.)
550    28. When duplicate subpattern names are present (necessarily with different
551        numbers, as required by 27 above), and a test is made by name in a
552        conditional pattern, either for a subpattern having been matched, or for
553        recursion in such a pattern, all the associated numbered subpatterns are
554        tested, and the overall condition is true if the condition is true for any
555        one of them. This is the way Perl works, and is also more like the way
556        testing by number works.
559  Version 7.9 11-Apr-09  Version 7.9 11-Apr-09
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