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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
4  Version 8.00 ??-???-??  Version 8.21
5    ------------
7    1.  Updating the JIT compiler.
9    2.  JIT compiler now supports OP_NCREF, OP_RREF and OP_NRREF. New test cases
10        are added as well.
12    3.  Fix cache-flush issue on PowerPC (It is still an experimental JIT port).
13        PCRE_EXTRA_TABLES is not suported by JIT, and should be checked before
14        calling _pcre_jit_exec. Some extra comments are added.
16    4.  Mark settings inside atomic groups that do not contain any capturing
17        parentheses, for example, (?>a(*:m)), were not being passed out. This bug
18        was introduced by change 18 for 8.20.
20    5.  Supporting of \x, \U and \u in JavaScript compatibility mode based on the
21        ECMA-262 standard.
23    6.  Lookbehinds such as (?<=a{2}b) that contained a fixed repetition were
24        erroneously being rejected as "not fixed length" if PCRE_CASELESS was set.
25        This bug was probably introduced by change 9 of 8.13.
27    7.  While fixing 6 above, I noticed that a number of other items were being
28        incorrectly rejected as "not fixed length". This arose partly because newer
29        opcodes had not been added to the fixed-length checking code. I have (a)
30        corrected the bug and added tests for these items, and (b) arranged for an
31        error to occur if an unknown opcode is encountered while checking for fixed
32        length instead of just assuming "not fixed length". The items that were
33        rejected were: (*ACCEPT), (*COMMIT), (*FAIL), (*MARK), (*PRUNE), (*SKIP),
34        (*THEN), \h, \H, \v, \V, and single character negative classes with fixed
35        repetitions, e.g. [^a]{3}, with and without PCRE_CASELESS.
37    8.  A possessively repeated conditional subpattern such as (?(?=c)c|d)++ was
38        being incorrectly compiled and would have given unpredicatble results.
40    9.  A possessively repeated subpattern with minimum repeat count greater than
41        one behaved incorrectly. For example, (A){2,}+ behaved as if it was
42        (A)(A)++ which meant that, after a subsequent mismatch, backtracking into
43        the first (A) could occur when it should not.
45    10. Add a cast and remove a redundant test from the code.
47    11. JIT should use pcre_malloc/pcre_free for allocation.
49    12. Updated pcre-config so that it no longer shows -L/usr/lib, which seems
50        best practice nowadays, and helps with cross-compiling. (If the exec_prefix
51        is anything other than /usr, -L is still shown).
53    13. In non-UTF-8 mode, \C is now supported in lookbehinds and DFA matching.
55    14. Perl does not support \N without a following name in a [] class; PCRE now
56        also gives an error.
58    15. If a forward reference was repeated with an upper limit of around 2000,
59        it caused the error "internal error: overran compiling workspace". The
60        maximum number of forward references (including repeats) was limited by the
61        internal workspace, and dependent on the LINK_SIZE. The code has been
62        rewritten so that the workspace expands (via pcre_malloc) if necessary, and
63        the default depends on LINK_SIZE. There is a new upper limit (for safety)
64        of around 200,000 forward references. While doing this, I also speeded up
65        the filling in of repeated forward references.
67    16. A repeated forward reference in a pattern such as (a)(?2){2}(.) was
68        incorrectly expecting the subject to contain another "a" after the start.
70    17. When (*SKIP:name) is activated without a corresponding (*MARK:name) earlier
71        in the match, the SKIP should be ignored. This was not happening; instead
72        the SKIP was being treated as NOMATCH. For patterns such as
73        /A(*MARK:A)A+(*SKIP:B)Z|AAC/ this meant that the AAC branch was never
74        tested.
76    18. The behaviour of (*MARK), (*PRUNE), and (*THEN) has been reworked and is
77        now much more compatible with Perl, in particular in cases where the result
78        is a non-match for a non-anchored pattern. For example, if
79        /b(*:m)f|a(*:n)w/ is matched against "abc", the non-match returns the name
80        "m", where previously it did not return a name. A side effect of this
81        change is that for partial matches, the last encountered mark name is
82        returned, as for non matches. A number of tests that were previously not
83        Perl-compatible have been moved into the Perl-compatible test files. The
84        refactoring has had the pleasing side effect of removing one argument from
85        the match() function, thus reducing its stack requirements.
87    19. If the /S+ option was used in pcretest to study a pattern using JIT,
88        subsequent uses of /S (without +) incorrectly behaved like /S+.
90    21. Retrieve executable code size support for the JIT compiler and fixing
91        some warnings.
93    22. A caseless match of a UTF-8 character whose other case uses fewer bytes did
94        not work when the shorter character appeared right at the end of the
95        subject string.
97    23. Added some (int) casts to non-JIT modules to reduce warnings on 64-bit
98        systems.
100    24. Added PCRE_INFO_JITSIZE to pass on the value from (21) above, and also
101        output it when the /M option is used in pcretest.
104    Version 8.20 21-Oct-2011
105    ------------------------
107    1.  Change 37 of 8.13 broke patterns like [:a]...[b:] because it thought it had
108        a POSIX class. After further experiments with Perl, which convinced me that
109        Perl has bugs and confusions, a closing square bracket is no longer allowed
110        in a POSIX name. This bug also affected patterns with classes that started
111        with full stops.
113    2.  If a pattern such as /(a)b|ac/ is matched against "ac", there is no
114        captured substring, but while checking the failing first alternative,
115        substring 1 is temporarily captured. If the output vector supplied to
116        pcre_exec() was not big enough for this capture, the yield of the function
117        was still zero ("insufficient space for captured substrings"). This cannot
118        be totally fixed without adding another stack variable, which seems a lot
119        of expense for a edge case. However, I have improved the situation in cases
120        such as /(a)(b)x|abc/ matched against "abc", where the return code
121        indicates that fewer than the maximum number of slots in the ovector have
122        been set.
124    3.  Related to (2) above: when there are more back references in a pattern than
125        slots in the output vector, pcre_exec() uses temporary memory during
126        matching, and copies in the captures as far as possible afterwards. It was
127        using the entire output vector, but this conflicts with the specification
128        that only 2/3 is used for passing back captured substrings. Now it uses
129        only the first 2/3, for compatibility. This is, of course, another edge
130        case.
132    4.  Zoltan Herczeg's just-in-time compiler support has been integrated into the
133        main code base, and can be used by building with --enable-jit. When this is
134        done, pcregrep automatically uses it unless --disable-pcregrep-jit or the
135        runtime --no-jit option is given.
137    5.  When the number of matches in a pcre_dfa_exec() run exactly filled the
138        ovector, the return from the function was zero, implying that there were
139        other matches that did not fit. The correct "exactly full" value is now
140        returned.
142    6.  If a subpattern that was called recursively or as a subroutine contained
143        (*PRUNE) or any other control that caused it to give a non-standard return,
144        invalid errors such as "Error -26 (nested recursion at the same subject
145        position)" or even infinite loops could occur.
147    7.  If a pattern such as /a(*SKIP)c|b(*ACCEPT)|/ was studied, it stopped
148        computing the minimum length on reaching *ACCEPT, and so ended up with the
149        wrong value of 1 rather than 0. Further investigation indicates that
150        computing a minimum subject length in the presence of *ACCEPT is difficult
151        (think back references, subroutine calls), and so I have changed the code
152        so that no minimum is registered for a pattern that contains *ACCEPT.
154    8.  If (*THEN) was present in the first (true) branch of a conditional group,
155        it was not handled as intended. [But see 16 below.]
157    9.  Replaced RunTest.bat and CMakeLists.txt with improved versions provided by
158        Sheri Pierce.
160    10. A pathological pattern such as /(*ACCEPT)a/ was miscompiled, thinking that
161        the first byte in a match must be "a".
163    11. Change 17 for 8.13 increased the recursion depth for patterns like
164        /a(?:.)*?a/ drastically. I've improved things by remembering whether a
165        pattern contains any instances of (*THEN). If it does not, the old
166        optimizations are restored. It would be nice to do this on a per-group
167        basis, but at the moment that is not feasible.
169    12. In some environments, the output of pcretest -C is CRLF terminated. This
170        broke RunTest's code that checks for the link size. A single white space
171        character after the value is now allowed for.
173    13. RunTest now checks for the "fr" locale as well as for "fr_FR" and "french".
174        For "fr", it uses the Windows-specific input and output files.
176    14. If (*THEN) appeared in a group that was called recursively or as a
177        subroutine, it did not work as intended. [But see next item.]
179    15. Consider the pattern /A (B(*THEN)C) | D/ where A, B, C, and D are complex
180        pattern fragments (but not containing any | characters). If A and B are
181        matched, but there is a failure in C so that it backtracks to (*THEN), PCRE
182        was behaving differently to Perl. PCRE backtracked into A, but Perl goes to
183        D. In other words, Perl considers parentheses that do not contain any |
184        characters to be part of a surrounding alternative, whereas PCRE was
185        treading (B(*THEN)C) the same as (B(*THEN)C|(*FAIL)) -- which Perl handles
186        differently. PCRE now behaves in the same way as Perl, except in the case
187        of subroutine/recursion calls such as (?1) which have in any case always
188        been different (but PCRE had them first :-).
190    16. Related to 15 above: Perl does not treat the | in a conditional group as
191        creating alternatives. Such a group is treated in the same way as an
192        ordinary group without any | characters when processing (*THEN). PCRE has
193        been changed to match Perl's behaviour.
195    17. If a user had set PCREGREP_COLO(U)R to something other than 1:31, the
196        RunGrepTest script failed.
198    18. Change 22 for version 13 caused atomic groups to use more stack. This is
199        inevitable for groups that contain captures, but it can lead to a lot of
200        stack use in large patterns. The old behaviour has been restored for atomic
201        groups that do not contain any capturing parentheses.
203    19. If the PCRE_NO_START_OPTIMIZE option was set for pcre_compile(), it did not
204        suppress the check for a minimum subject length at run time. (If it was
205        given to pcre_exec() or pcre_dfa_exec() it did work.)
207    20. Fixed an ASCII-dependent infelicity in pcretest that would have made it
208        fail to work when decoding hex characters in data strings in EBCDIC
209        environments.
211    21. It appears that in at least one Mac OS environment, the isxdigit() function
212        is implemented as a macro that evaluates to its argument more than once,
213        contravening the C 90 Standard (I haven't checked a later standard). There
214        was an instance in pcretest which caused it to go wrong when processing
215        \x{...} escapes in subject strings. The has been rewritten to avoid using
216        things like p++ in the argument of isxdigit().
219    Version 8.13 16-Aug-2011
220    ------------------------
222    1.  The Unicode data tables have been updated to Unicode 6.0.0.
224    2.  Two minor typos in pcre_internal.h have been fixed.
226    3.  Added #include <string.h> to pcre_scanner_unittest.cc, pcrecpp.cc, and
227        pcrecpp_unittest.cc. They are needed for strcmp(), memset(), and strchr()
228        in some environments (e.g. Solaris 10/SPARC using Sun Studio 12U2).
230    4.  There were a number of related bugs in the code for matching backrefences
231        caselessly in UTF-8 mode when codes for the characters concerned were
232        different numbers of bytes. For example, U+023A and U+2C65 are an upper
233        and lower case pair, using 2 and 3 bytes, respectively. The main bugs were:
234        (a) A reference to 3 copies of a 2-byte code matched only 2 of a 3-byte
235        code. (b) A reference to 2 copies of a 3-byte code would not match 2 of a
236        2-byte code at the end of the subject (it thought there wasn't enough data
237        left).
239    5.  Comprehensive information about what went wrong is now returned by
240        pcre_exec() and pcre_dfa_exec() when the UTF-8 string check fails, as long
241        as the output vector has at least 2 elements. The offset of the start of
242        the failing character and a reason code are placed in the vector.
244    6.  When the UTF-8 string check fails for pcre_compile(), the offset that is
245        now returned is for the first byte of the failing character, instead of the
246        last byte inspected. This is an incompatible change, but I hope it is small
247        enough not to be a problem. It makes the returned offset consistent with
248        pcre_exec() and pcre_dfa_exec().
250    7.  pcretest now gives a text phrase as well as the error number when
251        pcre_exec() or pcre_dfa_exec() fails; if the error is a UTF-8 check
252        failure, the offset and reason code are output.
254    8.  When \R was used with a maximizing quantifier it failed to skip backwards
255        over a \r\n pair if the subsequent match failed. Instead, it just skipped
256        back over a single character (\n). This seems wrong (because it treated the
257        two characters as a single entity when going forwards), conflicts with the
258        documentation that \R is equivalent to (?>\r\n|\n|...etc), and makes the
259        behaviour of \R* different to (\R)*, which also seems wrong. The behaviour
260        has been changed.
262    9.  Some internal refactoring has changed the processing so that the handling
263        of the PCRE_CASELESS and PCRE_MULTILINE options is done entirely at compile
264        time (the PCRE_DOTALL option was changed this way some time ago: version
265        7.7 change 16). This has made it possible to abolish the OP_OPT op code,
266        which was always a bit of a fudge. It also means that there is one less
267        argument for the match() function, which reduces its stack requirements
268        slightly. This change also fixes an incompatibility with Perl: the pattern
269        (?i:([^b]))(?1) should not match "ab", but previously PCRE gave a match.
271    10. More internal refactoring has drastically reduced the number of recursive
272        calls to match() for possessively repeated groups such as (abc)++ when
273        using pcre_exec().
275    11. While implementing 10, a number of bugs in the handling of groups were
276        discovered and fixed:
278        (?<=(a)+) was not diagnosed as invalid (non-fixed-length lookbehind).
279        (a|)*(?1) gave a compile-time internal error.
280        ((a|)+)+  did not notice that the outer group could match an empty string.
281        (^a|^)+   was not marked as anchored.
282        (.*a|.*)+ was not marked as matching at start or after a newline.
284    12. Yet more internal refactoring has removed another argument from the match()
285        function. Special calls to this function are now indicated by setting a
286        value in a variable in the "match data" data block.
288    13. Be more explicit in pcre_study() instead of relying on "default" for
289        opcodes that mean there is no starting character; this means that when new
290        ones are added and accidentally left out of pcre_study(), testing should
291        pick them up.
293    14. The -s option of pcretest has been documented for ages as being an old
294        synonym of -m (show memory usage). I have changed it to mean "force study
295        for every regex", that is, assume /S for every regex. This is similar to -i
296        and -d etc. It's slightly incompatible, but I'm hoping nobody is still
297        using it. It makes it easier to run collections of tests with and without
298        study enabled, and thereby test pcre_study() more easily. All the standard
299        tests are now run with and without -s (but some patterns can be marked as
300        "never study" - see 20 below).
302    15. When (*ACCEPT) was used in a subpattern that was called recursively, the
303        restoration of the capturing data to the outer values was not happening
304        correctly.
306    16. If a recursively called subpattern ended with (*ACCEPT) and matched an
307        empty string, and PCRE_NOTEMPTY was set, pcre_exec() thought the whole
308        pattern had matched an empty string, and so incorrectly returned a no
309        match.
311    17. There was optimizing code for the last branch of non-capturing parentheses,
312        and also for the obeyed branch of a conditional subexpression, which used
313        tail recursion to cut down on stack usage. Unfortunately, now that there is
314        the possibility of (*THEN) occurring in these branches, tail recursion is
315        no longer possible because the return has to be checked for (*THEN). These
316        two optimizations have therefore been removed. [But see 8.20/11 above.]
318    18. If a pattern containing \R was studied, it was assumed that \R always
319        matched two bytes, thus causing the minimum subject length to be
320        incorrectly computed because \R can also match just one byte.
322    19. If a pattern containing (*ACCEPT) was studied, the minimum subject length
323        was incorrectly computed.
325    20. If /S is present twice on a test pattern in pcretest input, it now
326        *disables* studying, thereby overriding the use of -s on the command line
327        (see 14 above). This is necessary for one or two tests to keep the output
328        identical in both cases.
330    21. When (*ACCEPT) was used in an assertion that matched an empty string and
331        PCRE_NOTEMPTY was set, PCRE applied the non-empty test to the assertion.
333    22. When an atomic group that contained a capturing parenthesis was
334        successfully matched, but the branch in which it appeared failed, the
335        capturing was not being forgotten if a higher numbered group was later
336        captured. For example, /(?>(a))b|(a)c/ when matching "ac" set capturing
337        group 1 to "a", when in fact it should be unset. This applied to multi-
338        branched capturing and non-capturing groups, repeated or not, and also to
339        positive assertions (capturing in negative assertions does not happen
340        in PCRE) and also to nested atomic groups.
342    23. Add the ++ qualifier feature to pcretest, to show the remainder of the
343        subject after a captured substring, to make it easier to tell which of a
344        number of identical substrings has been captured.
346    24. The way atomic groups are processed by pcre_exec() has been changed so that
347        if they are repeated, backtracking one repetition now resets captured
348        values correctly. For example, if ((?>(a+)b)+aabab) is matched against
349        "aaaabaaabaabab" the value of captured group 2 is now correctly recorded as
350        "aaa". Previously, it would have been "a". As part of this code
351        refactoring, the way recursive calls are handled has also been changed.
353    25. If an assertion condition captured any substrings, they were not passed
354        back unless some other capturing happened later. For example, if
355        (?(?=(a))a) was matched against "a", no capturing was returned.
357    26. When studying a pattern that contained subroutine calls or assertions,
358        the code for finding the minimum length of a possible match was handling
359        direct recursions such as (xxx(?1)|yyy) but not mutual recursions (where
360        group 1 called group 2 while simultaneously a separate group 2 called group
361        1). A stack overflow occurred in this case. I have fixed this by limiting
362        the recursion depth to 10.
364    27. Updated RunTest.bat in the distribution to the version supplied by Tom
365        Fortmann. This supports explicit test numbers on the command line, and has
366        argument validation and error reporting.
368    28. An instance of \X with an unlimited repeat could fail if at any point the
369        first character it looked at was a mark character.
371    29. Some minor code refactoring concerning Unicode properties and scripts
372        should reduce the stack requirement of match() slightly.
374    30. Added the '=' option to pcretest to check the setting of unused capturing
375        slots at the end of the pattern, which are documented as being -1, but are
376        not included in the return count.
378    31. If \k was not followed by a braced, angle-bracketed, or quoted name, PCRE
379        compiled something random. Now it gives a compile-time error (as does
380        Perl).
382    32. A *MARK encountered during the processing of a positive assertion is now
383        recorded and passed back (compatible with Perl).
385    33. If --only-matching or --colour was set on a pcregrep call whose pattern
386        had alternative anchored branches, the search for a second match in a line
387        was done as if at the line start. Thus, for example, /^01|^02/ incorrectly
388        matched the line "0102" twice. The same bug affected patterns that started
389        with a backwards assertion. For example /\b01|\b02/ also matched "0102"
390        twice.
392    34. Previously, PCRE did not allow quantification of assertions. However, Perl
393        does, and because of capturing effects, quantifying parenthesized
394        assertions may at times be useful. Quantifiers are now allowed for
395        parenthesized assertions.
397    35. A minor code tidy in pcre_compile() when checking options for \R usage.
399    36. \g was being checked for fancy things in a character class, when it should
400        just be a literal "g".
402    37. PCRE was rejecting [:a[:digit:]] whereas Perl was not. It seems that the
403        appearance of a nested POSIX class supersedes an apparent external class.
404        For example, [:a[:digit:]b:] matches "a", "b", ":", or a digit. Also,
405        unescaped square brackets may also appear as part of class names. For
406        example, [:a[:abc]b:] gives unknown class "[:abc]b:]". PCRE now behaves
407        more like Perl. (But see 8.20/1 above.)
409    38. PCRE was giving an error for \N with a braced quantifier such as {1,} (this
410        was because it thought it was \N{name}, which is not supported).
412    39. Add minix to OS list not supporting the -S option in pcretest.
414    40. PCRE tries to detect cases of infinite recursion at compile time, but it
415        cannot analyze patterns in sufficient detail to catch mutual recursions
416        such as ((?1))((?2)). There is now a runtime test that gives an error if a
417        subgroup is called recursively as a subpattern for a second time at the
418        same position in the subject string. In previous releases this might have
419        been caught by the recursion limit, or it might have run out of stack.
421    41. A pattern such as /(?(R)a+|(?R)b)/ is quite safe, as the recursion can
422        happen only once. PCRE was, however incorrectly giving a compile time error
423        "recursive call could loop indefinitely" because it cannot analyze the
424        pattern in sufficient detail. The compile time test no longer happens when
425        PCRE is compiling a conditional subpattern, but actual runaway loops are
426        now caught at runtime (see 40 above).
428    42. It seems that Perl allows any characters other than a closing parenthesis
429        to be part of the NAME in (*MARK:NAME) and other backtracking verbs. PCRE
430        has been changed to be the same.
432    43. Updated configure.ac to put in more quoting round AC_LANG_PROGRAM etc. so
433        as not to get warnings when autogen.sh is called. Also changed
434        AC_PROG_LIBTOOL (deprecated) to LT_INIT (the current macro).
436    44. To help people who use pcregrep to scan files containing exceedingly long
437        lines, the following changes have been made:
439        (a) The default value of the buffer size parameter has been increased from
440            8K to 20K. (The actual buffer used is three times this size.)
442        (b) The default can be changed by ./configure --with-pcregrep-bufsize when
443            PCRE is built.
445        (c) A --buffer-size=n option has been added to pcregrep, to allow the size
446            to be set at run time.
448        (d) Numerical values in pcregrep options can be followed by K or M, for
449            example --buffer-size=50K.
451        (e) If a line being scanned overflows pcregrep's buffer, an error is now
452            given and the return code is set to 2.
454    45. Add a pointer to the latest mark to the callout data block.
456    46. The pattern /.(*F)/, when applied to "abc" with PCRE_PARTIAL_HARD, gave a
457        partial match of an empty string instead of no match. This was specific to
458        the use of ".".
460    47. The pattern /f.*/8s, when applied to "for" with PCRE_PARTIAL_HARD, gave a
461        complete match instead of a partial match. This bug was dependent on both
462        the PCRE_UTF8 and PCRE_DOTALL options being set.
464    48. For a pattern such as /\babc|\bdef/ pcre_study() was failing to set up the
465        starting byte set, because \b was not being ignored.
468    Version 8.12 15-Jan-2011
469    ------------------------
471    1.  Fixed some typos in the markup of the man pages, and wrote a script that
472        checks for such things as part of the documentation building process.
474    2.  On a big-endian 64-bit system, pcregrep did not correctly process the
475        --match-limit and --recursion-limit options (added for 8.11). In
476        particular, this made one of the standard tests fail. (The integer value
477        went into the wrong half of a long int.)
479    3.  If the --colour option was given to pcregrep with -v (invert match), it
480        did strange things, either producing crazy output, or crashing. It should,
481        of course, ignore a request for colour when reporting lines that do not
482        match.
484    4.  Another pcregrep bug caused similar problems if --colour was specified with
485        -M (multiline) and the pattern match finished with a line ending.
487    5.  In pcregrep, when a pattern that ended with a literal newline sequence was
488        matched in multiline mode, the following line was shown as part of the
489        match. This seems wrong, so I have changed it.
491    6.  Another pcregrep bug in multiline mode, when --colour was specified, caused
492        the check for further matches in the same line (so they could be coloured)
493        to overrun the end of the current line. If another match was found, it was
494        incorrectly shown (and then shown again when found in the next line).
496    7.  If pcregrep was compiled under Windows, there was a reference to the
497        function pcregrep_exit() before it was defined. I am assuming this was
498        the cause of the "error C2371: 'pcregrep_exit' : redefinition;" that was
499        reported by a user. I've moved the definition above the reference.
502    Version 8.11 10-Dec-2010
503    ------------------------
505    1.  (*THEN) was not working properly if there were untried alternatives prior
506        to it in the current branch. For example, in ((a|b)(*THEN)(*F)|c..) it
507        backtracked to try for "b" instead of moving to the next alternative branch
508        at the same level (in this case, to look for "c"). The Perl documentation
509        is clear that when (*THEN) is backtracked onto, it goes to the "next
510        alternative in the innermost enclosing group".
512    2.  (*COMMIT) was not overriding (*THEN), as it does in Perl. In a pattern
513        such as   (A(*COMMIT)B(*THEN)C|D)  any failure after matching A should
514        result in overall failure. Similarly, (*COMMIT) now overrides (*PRUNE) and
515        (*SKIP), (*SKIP) overrides (*PRUNE) and (*THEN), and (*PRUNE) overrides
516        (*THEN).
518    3.  If \s appeared in a character class, it removed the VT character from
519        the class, even if it had been included by some previous item, for example
520        in [\x00-\xff\s]. (This was a bug related to the fact that VT is not part
521        of \s, but is part of the POSIX "space" class.)
523    4.  A partial match never returns an empty string (because you can always
524        match an empty string at the end of the subject); however the checking for
525        an empty string was starting at the "start of match" point. This has been
526        changed to the "earliest inspected character" point, because the returned
527        data for a partial match starts at this character. This means that, for
528        example, /(?<=abc)def/ gives a partial match for the subject "abc"
529        (previously it gave "no match").
531    5.  Changes have been made to the way PCRE_PARTIAL_HARD affects the matching
532        of $, \z, \Z, \b, and \B. If the match point is at the end of the string,
533        previously a full match would be given. However, setting PCRE_PARTIAL_HARD
534        has an implication that the given string is incomplete (because a partial
535        match is preferred over a full match). For this reason, these items now
536        give a partial match in this situation. [Aside: previously, the one case
537        /t\b/ matched against "cat" with PCRE_PARTIAL_HARD set did return a partial
538        match rather than a full match, which was wrong by the old rules, but is
539        now correct.]
541    6.  There was a bug in the handling of #-introduced comments, recognized when
542        PCRE_EXTENDED is set, when PCRE_NEWLINE_ANY and PCRE_UTF8 were also set.
543        If a UTF-8 multi-byte character included the byte 0x85 (e.g. +U0445, whose
544        UTF-8 encoding is 0xd1,0x85), this was misinterpreted as a newline when
545        scanning for the end of the comment. (*Character* 0x85 is an "any" newline,
546        but *byte* 0x85 is not, in UTF-8 mode). This bug was present in several
547        places in pcre_compile().
549    7.  Related to (6) above, when pcre_compile() was skipping #-introduced
550        comments when looking ahead for named forward references to subpatterns,
551        the only newline sequence it recognized was NL. It now handles newlines
552        according to the set newline convention.
554    8.  SunOS4 doesn't have strerror() or strtoul(); pcregrep dealt with the
555        former, but used strtoul(), whereas pcretest avoided strtoul() but did not
556        cater for a lack of strerror(). These oversights have been fixed.
558    9.  Added --match-limit and --recursion-limit to pcregrep.
560    10. Added two casts needed to build with Visual Studio when NO_RECURSE is set.
562    11. When the -o option was used, pcregrep was setting a return code of 1, even
563        when matches were found, and --line-buffered was not being honoured.
565    12. Added an optional parentheses number to the -o and --only-matching options
566        of pcregrep.
568    13. Imitating Perl's /g action for multiple matches is tricky when the pattern
569        can match an empty string. The code to do it in pcretest and pcredemo
570        needed fixing:
572        (a) When the newline convention was "crlf", pcretest got it wrong, skipping
573            only one byte after an empty string match just before CRLF (this case
574            just got forgotten; "any" and "anycrlf" were OK).
576        (b) The pcretest code also had a bug, causing it to loop forever in UTF-8
577            mode when an empty string match preceded an ASCII character followed by
578            a non-ASCII character. (The code for advancing by one character rather
579            than one byte was nonsense.)
581        (c) The pcredemo.c sample program did not have any code at all to handle
582            the cases when CRLF is a valid newline sequence.
584    14. Neither pcre_exec() nor pcre_dfa_exec() was checking that the value given
585        as a starting offset was within the subject string. There is now a new
586        error, PCRE_ERROR_BADOFFSET, which is returned if the starting offset is
587        negative or greater than the length of the string. In order to test this,
588        pcretest is extended to allow the setting of negative starting offsets.
590    15. In both pcre_exec() and pcre_dfa_exec() the code for checking that the
591        starting offset points to the beginning of a UTF-8 character was
592        unnecessarily clumsy. I tidied it up.
594    16. Added PCRE_ERROR_SHORTUTF8 to make it possible to distinguish between a
595        bad UTF-8 sequence and one that is incomplete when using PCRE_PARTIAL_HARD.
597    17. Nobody had reported that the --include_dir option, which was added in
598        release 7.7 should have been called --include-dir (hyphen, not underscore)
599        for compatibility with GNU grep. I have changed it to --include-dir, but
600        left --include_dir as an undocumented synonym, and the same for
601        --exclude-dir, though that is not available in GNU grep, at least as of
602        release 2.5.4.
604    18. At a user's suggestion, the macros GETCHAR and friends (which pick up UTF-8
605        characters from a string of bytes) have been redefined so as not to use
606        loops, in order to improve performance in some environments. At the same
607        time, I abstracted some of the common code into auxiliary macros to save
608        repetition (this should not affect the compiled code).
610    19. If \c was followed by a multibyte UTF-8 character, bad things happened. A
611        compile-time error is now given if \c is not followed by an ASCII
612        character, that is, a byte less than 128. (In EBCDIC mode, the code is
613        different, and any byte value is allowed.)
615    20. Recognize (*NO_START_OPT) at the start of a pattern to set the PCRE_NO_
616        START_OPTIMIZE option, which is now allowed at compile time - but just
617        passed through to pcre_exec() or pcre_dfa_exec(). This makes it available
618        to pcregrep and other applications that have no direct access to PCRE
619        options. The new /Y option in pcretest sets this option when calling
620        pcre_compile().
622    21. Change 18 of release 8.01 broke the use of named subpatterns for recursive
623        back references. Groups containing recursive back references were forced to
624        be atomic by that change, but in the case of named groups, the amount of
625        memory required was incorrectly computed, leading to "Failed: internal
626        error: code overflow". This has been fixed.
628    22. Some patches to pcre_stringpiece.h, pcre_stringpiece_unittest.cc, and
629        pcretest.c, to avoid build problems in some Borland environments.
632    Version 8.10 25-Jun-2010
633    ------------------------
635    1.  Added support for (*MARK:ARG) and for ARG additions to PRUNE, SKIP, and
636        THEN.
638    2.  (*ACCEPT) was not working when inside an atomic group.
640    3.  Inside a character class, \B is treated as a literal by default, but
641        faulted if PCRE_EXTRA is set. This mimics Perl's behaviour (the -w option
642        causes the error). The code is unchanged, but I tidied the documentation.
644    4.  Inside a character class, PCRE always treated \R and \X as literals,
645        whereas Perl faults them if its -w option is set. I have changed PCRE so
646        that it faults them when PCRE_EXTRA is set.
648    5.  Added support for \N, which always matches any character other than
649        newline. (It is the same as "." when PCRE_DOTALL is not set.)
651    6.  When compiling pcregrep with newer versions of gcc which may have
652        FORTIFY_SOURCE set, several warnings "ignoring return value of 'fwrite',
653        declared with attribute warn_unused_result" were given. Just casting the
654        result to (void) does not stop the warnings; a more elaborate fudge is
655        needed. I've used a macro to implement this.
657    7.  Minor change to pcretest.c to avoid a compiler warning.
659    8.  Added four artifical Unicode properties to help with an option to make
660        \s etc use properties (see next item). The new properties are: Xan
661        (alphanumeric), Xsp (Perl space), Xps (POSIX space), and Xwd (word).
663    9.  Added PCRE_UCP to make \b, \d, \s, \w, and certain POSIX character classes
664        use Unicode properties. (*UCP) at the start of a pattern can be used to set
665        this option. Modified pcretest to add /W to test this facility. Added
666        REG_UCP to make it available via the POSIX interface.
668    10. Added --line-buffered to pcregrep.
670    11. In UTF-8 mode, if a pattern that was compiled with PCRE_CASELESS was
671        studied, and the match started with a letter with a code point greater than
672        127 whose first byte was different to the first byte of the other case of
673        the letter, the other case of this starting letter was not recognized
674        (#976).
676    12. If a pattern that was studied started with a repeated Unicode property
677        test, for example, \p{Nd}+, there was the theoretical possibility of
678        setting up an incorrect bitmap of starting bytes, but fortunately it could
679        not have actually happened in practice until change 8 above was made (it
680        added property types that matched character-matching opcodes).
682    13. pcre_study() now recognizes \h, \v, and \R when constructing a bit map of
683        possible starting bytes for non-anchored patterns.
685    14. Extended the "auto-possessify" feature of pcre_compile(). It now recognizes
686        \R, and also a number of cases that involve Unicode properties, both
687        explicit and implicit when PCRE_UCP is set.
689    15. If a repeated Unicode property match (e.g. \p{Lu}*) was used with non-UTF-8
690        input, it could crash or give wrong results if characters with values
691        greater than 0xc0 were present in the subject string. (Detail: it assumed
692        UTF-8 input when processing these items.)
694    16. Added a lot of (int) casts to avoid compiler warnings in systems where
695        size_t is 64-bit (#991).
697    17. Added a check for running out of memory when PCRE is compiled with
698        --disable-stack-for-recursion (#990).
700    18. If the last data line in a file for pcretest does not have a newline on
701        the end, a newline was missing in the output.
703    19. The default pcre_chartables.c file recognizes only ASCII characters (values
704        less than 128) in its various bitmaps. However, there is a facility for
705        generating tables according to the current locale when PCRE is compiled. It
706        turns out that in some environments, 0x85 and 0xa0, which are Unicode space
707        characters, are recognized by isspace() and therefore were getting set in
708        these tables, and indeed these tables seem to approximate to ISO 8859. This
709        caused a problem in UTF-8 mode when pcre_study() was used to create a list
710        of bytes that can start a match. For \s, it was including 0x85 and 0xa0,
711        which of course cannot start UTF-8 characters. I have changed the code so
712        that only real ASCII characters (less than 128) and the correct starting
713        bytes for UTF-8 encodings are set for characters greater than 127 when in
714        UTF-8 mode. (When PCRE_UCP is set - see 9 above - the code is different
715        altogether.)
717    20. Added the /T option to pcretest so as to be able to run tests with non-
718        standard character tables, thus making it possible to include the tests
719        used for 19 above in the standard set of tests.
721    21. A pattern such as (?&t)(?#()(?(DEFINE)(?<t>a)) which has a forward
722        reference to a subpattern the other side of a comment that contains an
723        opening parenthesis caused either an internal compiling error, or a
724        reference to the wrong subpattern.
727    Version 8.02 19-Mar-2010
728    ------------------------
730    1.  The Unicode data tables have been updated to Unicode 5.2.0.
732    2.  Added the option --libs-cpp to pcre-config, but only when C++ support is
733        configured.
735    3.  Updated the licensing terms in the pcregexp.pas file, as agreed with the
736        original author of that file, following a query about its status.
738    4.  On systems that do not have stdint.h (e.g. Solaris), check for and include
739        inttypes.h instead. This fixes a bug that was introduced by change 8.01/8.
741    5.  A pattern such as (?&t)*+(?(DEFINE)(?<t>.)) which has a possessive
742        quantifier applied to a forward-referencing subroutine call, could compile
743        incorrect code or give the error "internal error: previously-checked
744        referenced subpattern not found".
746    6.  Both MS Visual Studio and Symbian OS have problems with initializing
747        variables to point to external functions. For these systems, therefore,
748        pcre_malloc etc. are now initialized to local functions that call the
749        relevant global functions.
751    7.  There were two entries missing in the vectors called coptable and poptable
752        in pcre_dfa_exec.c. This could lead to memory accesses outsize the vectors.
753        I've fixed the data, and added a kludgy way of testing at compile time that
754        the lengths are correct (equal to the number of opcodes).
756    8.  Following on from 7, I added a similar kludge to check the length of the
757        eint vector in pcreposix.c.
759    9.  Error texts for pcre_compile() are held as one long string to avoid too
760        much relocation at load time. To find a text, the string is searched,
761        counting zeros. There was no check for running off the end of the string,
762        which could happen if a new error number was added without updating the
763        string.
765    10. \K gave a compile-time error if it appeared in a lookbehind assersion.
767    11. \K was not working if it appeared in an atomic group or in a group that
768        was called as a "subroutine", or in an assertion. Perl 5.11 documents that
769        \K is "not well defined" if used in an assertion. PCRE now accepts it if
770        the assertion is positive, but not if it is negative.
772    12. Change 11 fortuitously reduced the size of the stack frame used in the
773        "match()" function of pcre_exec.c by one pointer. Forthcoming
774        implementation of support for (*MARK) will need an extra pointer on the
775        stack; I have reserved it now, so that the stack frame size does not
776        decrease.
778    13. A pattern such as (?P<L1>(?P<L2>0)|(?P>L2)(?P>L1)) in which the only other
779        item in branch that calls a recursion is a subroutine call - as in the
780        second branch in the above example - was incorrectly given the compile-
781        time error "recursive call could loop indefinitely" because pcre_compile()
782        was not correctly checking the subroutine for matching a non-empty string.
784    14. The checks for overrunning compiling workspace could trigger after an
785        overrun had occurred. This is a "should never occur" error, but it can be
786        triggered by pathological patterns such as hundreds of nested parentheses.
787        The checks now trigger 100 bytes before the end of the workspace.
789    15. Fix typo in configure.ac: "srtoq" should be "strtoq".
792    Version 8.01 19-Jan-2010
793    ------------------------
795    1.  If a pattern contained a conditional subpattern with only one branch (in
796        particular, this includes all (*DEFINE) patterns), a call to pcre_study()
797        computed the wrong minimum data length (which is of course zero for such
798        subpatterns). This could cause incorrect "no match" results.
800    2.  For patterns such as (?i)a(?-i)b|c where an option setting at the start of
801        the pattern is reset in the first branch, pcre_compile() failed with
802        "internal error: code overflow at offset...". This happened only when
803        the reset was to the original external option setting. (An optimization
804        abstracts leading options settings into an external setting, which was the
805        cause of this.)
807    3.  A pattern such as ^(?!a(*SKIP)b) where a negative assertion contained one
808        of the verbs SKIP, PRUNE, or COMMIT, did not work correctly. When the
809        assertion pattern did not match (meaning that the assertion was true), it
810        was incorrectly treated as false if the SKIP had been reached during the
811        matching. This also applied to assertions used as conditions.
813    4.  If an item that is not supported by pcre_dfa_exec() was encountered in an
814        assertion subpattern, including such a pattern used as a condition,
815        unpredictable results occurred, instead of the error return
818    5.  The C++ GlobalReplace function was not working like Perl for the special
819        situation when an empty string is matched. It now does the fancy magic
820        stuff that is necessary.
822    6.  In pcre_internal.h, obsolete includes to setjmp.h and stdarg.h have been
823        removed. (These were left over from very, very early versions of PCRE.)
825    7.  Some cosmetic changes to the code to make life easier when compiling it
826        as part of something else:
828        (a) Change DEBUG to PCRE_DEBUG.
830        (b) In pcre_compile(), rename the member of the "branch_chain" structure
831            called "current" as "current_branch", to prevent a collision with the
832            Linux macro when compiled as a kernel module.
834        (c) In pcre_study(), rename the function set_bit() as set_table_bit(), to
835            prevent a collision with the Linux macro when compiled as a kernel
836            module.
838    8.  In pcre_compile() there are some checks for integer overflows that used to
839        cast potentially large values to (double). This has been changed to that
840        when building, a check for int64_t is made, and if it is found, it is used
841        instead, thus avoiding the use of floating point arithmetic. (There is no
842        other use of FP in PCRE.) If int64_t is not found, the fallback is to
843        double.
845    9.  Added two casts to avoid signed/unsigned warnings from VS Studio Express
846        2005 (difference between two addresses compared to an unsigned value).
848    10. Change the standard AC_CHECK_LIB test for libbz2 in configure.ac to a
849        custom one, because of the following reported problem in Windows:
851          - libbz2 uses the Pascal calling convention (WINAPI) for the functions
852              under Win32.
853          - The standard autoconf AC_CHECK_LIB fails to include "bzlib.h",
854              therefore missing the function definition.
855          - The compiler thus generates a "C" signature for the test function.
856          - The linker fails to find the "C" function.
857          - PCRE fails to configure if asked to do so against libbz2.
859    11. When running libtoolize from libtool-2.2.6b as part of autogen.sh, these
860        messages were output:
862          Consider adding `AC_CONFIG_MACRO_DIR([m4])' to configure.ac and
863          rerunning libtoolize, to keep the correct libtool macros in-tree.
864          Consider adding `-I m4' to ACLOCAL_AMFLAGS in Makefile.am.
866        I have done both of these things.
868    12. Although pcre_dfa_exec() does not use nearly as much stack as pcre_exec()
869        most of the time, it *can* run out if it is given a pattern that contains a
870        runaway infinite recursion. I updated the discussion in the pcrestack man
871        page.
873    13. Now that we have gone to the x.xx style of version numbers, the minor
874        version may start with zero. Using 08 or 09 is a bad idea because users
875        might check the value of PCRE_MINOR in their code, and 08 or 09 may be
876        interpreted as invalid octal numbers. I've updated the previous comment in
877        configure.ac, and also added a check that gives an error if 08 or 09 are
878        used.
880    14. Change 8.00/11 was not quite complete: code had been accidentally omitted,
881        causing partial matching to fail when the end of the subject matched \W
882        in a UTF-8 pattern where \W was quantified with a minimum of 3.
884    15. There were some discrepancies between the declarations in pcre_internal.h
885        of _pcre_is_newline(), _pcre_was_newline(), and _pcre_valid_utf8() and
886        their definitions. The declarations used "const uschar *" and the
887        definitions used USPTR. Even though USPTR is normally defined as "const
888        unsigned char *" (and uschar is typedeffed as "unsigned char"), it was
889        reported that: "This difference in casting confuses some C++ compilers, for
890        example, SunCC recognizes above declarations as different functions and
891        generates broken code for hbpcre." I have changed the declarations to use
892        USPTR.
894    16. GNU libtool is named differently on some systems. The autogen.sh script now
895        tries several variants such as glibtoolize (MacOSX) and libtoolize1x
896        (FreeBSD).
898    17. Applied Craig's patch that fixes an HP aCC compile error in pcre 8.00
899        (strtoXX undefined when compiling pcrecpp.cc). The patch contains this
900        comment: "Figure out how to create a longlong from a string: strtoll and
901        equivalent. It's not enough to call AC_CHECK_FUNCS: hpux has a strtoll, for
902        instance, but it only takes 2 args instead of 3!"
904    18. A subtle bug concerned with back references has been fixed by a change of
905        specification, with a corresponding code fix. A pattern such as
906        ^(xa|=?\1a)+$ which contains a back reference inside the group to which it
907        refers, was giving matches when it shouldn't. For example, xa=xaaa would
908        match that pattern. Interestingly, Perl (at least up to 5.11.3) has the
909        same bug. Such groups have to be quantified to be useful, or contained
910        inside another quantified group. (If there's no repetition, the reference
911        can never match.) The problem arises because, having left the group and
912        moved on to the rest of the pattern, a later failure that backtracks into
913        the group uses the captured value from the final iteration of the group
914        rather than the correct earlier one. I have fixed this in PCRE by forcing
915        any group that contains a reference to itself to be an atomic group; that
916        is, there cannot be any backtracking into it once it has completed. This is
917        similar to recursive and subroutine calls.
920    Version 8.00 19-Oct-09
921  ----------------------  ----------------------
923  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
924      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
925      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
926      error.      error.
928    2.  Changed the call to open a subject file in pcregrep from fopen(pathname,
929        "r") to fopen(pathname, "rb"), which fixed a problem with some of the tests
930        in a Windows environment.
932    3.  The pcregrep --count option prints the count for each file even when it is
933        zero, as does GNU grep. However, pcregrep was also printing all files when
934        --files-with-matches was added. Now, when both options are given, it prints
935        counts only for those files that have at least one match. (GNU grep just
936        prints the file name in this circumstance, but including the count seems
937        more useful - otherwise, why use --count?) Also ensured that the
938        combination -clh just lists non-zero counts, with no names.
940    4.  The long form of the pcregrep -F option was incorrectly implemented as
941        --fixed_strings instead of --fixed-strings. This is an incompatible change,
942        but it seems right to fix it, and I didn't think it was worth preserving
943        the old behaviour.
945    5.  The command line items --regex=pattern and --regexp=pattern were not
946        recognized by pcregrep, which required --regex pattern or --regexp pattern
947        (with a space rather than an '='). The man page documented the '=' forms,
948        which are compatible with GNU grep; these now work.
950    6.  No libpcreposix.pc file was created for pkg-config; there was just
951        libpcre.pc and libpcrecpp.pc. The omission has been rectified.
953    7.  Added #ifndef SUPPORT_UCP into the pcre_ucd.c module, to reduce its size
954        when UCP support is not needed, by modifying the Python script that
955        generates it from Unicode data files. This should not matter if the module
956        is correctly used as a library, but I received one complaint about 50K of
957        unwanted data. My guess is that the person linked everything into his
958        program rather than using a library. Anyway, it does no harm.
960    8.  A pattern such as /\x{123}{2,2}+/8 was incorrectly compiled; the trigger
961        was a minimum greater than 1 for a wide character in a possessive
962        repetition. The same bug could also affect patterns like /(\x{ff}{0,2})*/8
963        which had an unlimited repeat of a nested, fixed maximum repeat of a wide
964        character. Chaos in the form of incorrect output or a compiling loop could
965        result.
967    9.  The restrictions on what a pattern can contain when partial matching is
968        requested for pcre_exec() have been removed. All patterns can now be
969        partially matched by this function. In addition, if there are at least two
970        slots in the offset vector, the offset of the earliest inspected character
971        for the match and the offset of the end of the subject are set in them when
972        PCRE_ERROR_PARTIAL is returned.
974    10. Partial matching has been split into two forms: PCRE_PARTIAL_SOFT, which is
975        synonymous with PCRE_PARTIAL, for backwards compatibility, and
976        PCRE_PARTIAL_HARD, which causes a partial match to supersede a full match,
977        and may be more useful for multi-segment matching.
979    11. Partial matching with pcre_exec() is now more intuitive. A partial match
980        used to be given if ever the end of the subject was reached; now it is
981        given only if matching could not proceed because another character was
982        needed. This makes a difference in some odd cases such as Z(*FAIL) with the
983        string "Z", which now yields "no match" instead of "partial match". In the
984        case of pcre_dfa_exec(), "no match" is given if every matching path for the
985        final character ended with (*FAIL).
987    12. Restarting a match using pcre_dfa_exec() after a partial match did not work
988        if the pattern had a "must contain" character that was already found in the
989        earlier partial match, unless partial matching was again requested. For
990        example, with the pattern /dog.(body)?/, the "must contain" character is
991        "g". If the first part-match was for the string "dog", restarting with
992        "sbody" failed. This bug has been fixed.
994    13. The string returned by pcre_dfa_exec() after a partial match has been
995        changed so that it starts at the first inspected character rather than the
996        first character of the match. This makes a difference only if the pattern
997        starts with a lookbehind assertion or \b or \B (\K is not supported by
998        pcre_dfa_exec()). It's an incompatible change, but it makes the two
999        matching functions compatible, and I think it's the right thing to do.
1001    14. Added a pcredemo man page, created automatically from the pcredemo.c file,
1002        so that the demonstration program is easily available in environments where
1003        PCRE has not been installed from source.
1005    15. Arranged to add -DPCRE_STATIC to cflags in libpcre.pc, libpcreposix.cp,
1006        libpcrecpp.pc and pcre-config when PCRE is not compiled as a shared
1007        library.
1009    16. Added REG_UNGREEDY to the pcreposix interface, at the request of a user.
1010        It maps to PCRE_UNGREEDY. It is not, of course, POSIX-compatible, but it
1011        is not the first non-POSIX option to be added. Clearly some people find
1012        these options useful.
1014    17. If a caller to the POSIX matching function regexec() passes a non-zero
1015        value for nmatch with a NULL value for pmatch, the value of
1016        nmatch is forced to zero.
1018    18. RunGrepTest did not have a test for the availability of the -u option of
1019        the diff command, as RunTest does. It now checks in the same way as
1020        RunTest, and also checks for the -b option.
1022    19. If an odd number of negated classes containing just a single character
1023        interposed, within parentheses, between a forward reference to a named
1024        subpattern and the definition of the subpattern, compilation crashed with
1025        an internal error, complaining that it could not find the referenced
1026        subpattern. An example of a crashing pattern is /(?&A)(([^m])(?<A>))/.
1027        [The bug was that it was starting one character too far in when skipping
1028        over the character class, thus treating the ] as data rather than
1029        terminating the class. This meant it could skip too much.]
1031    20. Added PCRE_NOTEMPTY_ATSTART in order to be able to correctly implement the
1032        /g option in pcretest when the pattern contains \K, which makes it possible
1033        to have an empty string match not at the start, even when the pattern is
1034        anchored. Updated pcretest and pcredemo to use this option.
1036    21. If the maximum number of capturing subpatterns in a recursion was greater
1037        than the maximum at the outer level, the higher number was returned, but
1038        with unset values at the outer level. The correct (outer level) value is
1039        now given.
1041    22. If (*ACCEPT) appeared inside capturing parentheses, previous releases of
1042        PCRE did not set those parentheses (unlike Perl). I have now found a way to
1043        make it do so. The string so far is captured, making this feature
1044        compatible with Perl.
1046    23. The tests have been re-organized, adding tests 11 and 12, to make it
1047        possible to check the Perl 5.10 features against Perl 5.10.
1049    24. Perl 5.10 allows subroutine calls in lookbehinds, as long as the subroutine
1050        pattern matches a fixed length string. PCRE did not allow this; now it
1051        does. Neither allows recursion.
1053    25. I finally figured out how to implement a request to provide the minimum
1054        length of subject string that was needed in order to match a given pattern.
1055        (It was back references and recursion that I had previously got hung up
1056        on.) This code has now been added to pcre_study(); it finds a lower bound
1057        to the length of subject needed. It is not necessarily the greatest lower
1058        bound, but using it to avoid searching strings that are too short does give
1059        some useful speed-ups. The value is available to calling programs via
1060        pcre_fullinfo().
1062    26. While implementing 25, I discovered to my embarrassment that pcretest had
1063        not been passing the result of pcre_study() to pcre_dfa_exec(), so the
1064        study optimizations had never been tested with that matching function.
1065        Oops. What is worse, even when it was passed study data, there was a bug in
1066        pcre_dfa_exec() that meant it never actually used it. Double oops. There
1067        were also very few tests of studied patterns with pcre_dfa_exec().
1069    27. If (?| is used to create subpatterns with duplicate numbers, they are now
1070        allowed to have the same name, even if PCRE_DUPNAMES is not set. However,
1071        on the other side of the coin, they are no longer allowed to have different
1072        names, because these cannot be distinguished in PCRE, and this has caused
1073        confusion. (This is a difference from Perl.)
1075    28. When duplicate subpattern names are present (necessarily with different
1076        numbers, as required by 27 above), and a test is made by name in a
1077        conditional pattern, either for a subpattern having been matched, or for
1078        recursion in such a pattern, all the associated numbered subpatterns are
1079        tested, and the overall condition is true if the condition is true for any
1080        one of them. This is the way Perl works, and is also more like the way
1081        testing by number works.
1084  Version 7.9 11-Apr-09  Version 7.9 11-Apr-09
1085  ---------------------  ---------------------

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