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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
4  Version 8.00 ??-???-??  Version 8.13 30-Apr-2011
5    ------------------------
7    1.  The Unicode data tables have been updated to Unicode 6.0.0.
9    2.  Two minor typos in pcre_internal.h have been fixed.
11    3.  Added #include <string.h> to pcre_scanner_unittest.cc, pcrecpp.cc, and
12        pcrecpp_unittest.cc. They are needed for strcmp(), memset(), and strchr()
13        in some environments (e.g. Solaris 10/SPARC using Sun Studio 12U2).
15    4.  There were a number of related bugs in the code for matching backrefences
16        caselessly in UTF-8 mode when codes for the characters concerned were
17        different numbers of bytes. For example, U+023A and U+2C65 are an upper
18        and lower case pair, using 2 and 3 bytes, respectively. The main bugs were:
19        (a) A reference to 3 copies of a 2-byte code matched only 2 of a 3-byte
20        code. (b) A reference to 2 copies of a 3-byte code would not match 2 of a
21        2-byte code at the end of the subject (it thought there wasn't enough data
22        left).
24    5.  Comprehensive information about what went wrong is now returned by
25        pcre_exec() and pcre_dfa_exec() when the UTF-8 string check fails, as long
26        as the output vector has at least 2 elements. The offset of the start of
27        the failing character and a reason code are placed in the vector.
29    6.  When the UTF-8 string check fails for pcre_compile(), the offset that is
30        now returned is for the first byte of the failing character, instead of the
31        last byte inspected. This is an incompatible change, but I hope it is small
32        enough not to be a problem. It makes the returned offset consistent with
33        pcre_exec() and pcre_dfa_exec().
35    7.  pcretest now gives a text phrase as well as the error number when
36        pcre_exec() or pcre_dfa_exec() fails; if the error is a UTF-8 check
37        failure, the offset and reason code are output.
39    8.  When \R was used with a maximizing quantifier it failed to skip backwards
40        over a \r\n pair if the subsequent match failed. Instead, it just skipped
41        back over a single character (\n). This seems wrong (because it treated the
42        two characters as a single entity when going forwards), conflicts with the
43        documentation that \R is equivalent to (?>\r\n|\n|...etc), and makes the
44        behaviour of \R* different to (\R)*, which also seems wrong. The behaviour
45        has been changed.
47    9.  Some internal refactoring has changed the processing so that the handling
48        of the PCRE_CASELESS and PCRE_MULTILINE options is done entirely at compile
49        time (the PCRE_DOTALL option was changed this way some time ago: version
50        7.7 change 16). This has made it possible to abolish the OP_OPT op code,
51        which was always a bit of a fudge. It also means that there is one less
52        argument for the match() function, which reduces its stack requirements
53        slightly. This change also fixes an incompatibility with Perl: the pattern
54        (?i:([^b]))(?1) should not match "ab", but previously PCRE gave a match.
56    10. More internal refactoring has drastically reduced the number of recursive
57        calls to match() for possessively repeated groups such as (abc)++ when
58        using pcre_exec().
60    11. While implementing 10, a number of bugs in the handling of groups were
61        discovered and fixed:
63        (?<=(a)+) was not diagnosed as invalid (non-fixed-length lookbehind).
64        (a|)*(?1) gave a compile-time internal error.
65        ((a|)+)+  did not notice that the outer group could match an empty string.
66        (^a|^)+   was not marked as anchored.
67        (.*a|.*)+ was not marked as matching at start or after a newline.
69    12. Yet more internal refactoring has removed another argument from the match()
70        function. Special calls to this function are now indicated by setting a
71        value in a variable in the "match data" data block.
73    13. Be more explicit in pcre_study() instead of relying on "default" for
74        opcodes that mean there is no starting character; this means that when new
75        ones are added and accidentally left out of pcre_study(), testing should
76        pick them up.
79    Version 8.12 15-Jan-2011
80    ------------------------
82    1.  Fixed some typos in the markup of the man pages, and wrote a script that
83        checks for such things as part of the documentation building process.
85    2.  On a big-endian 64-bit system, pcregrep did not correctly process the
86        --match-limit and --recursion-limit options (added for 8.11). In
87        particular, this made one of the standard tests fail. (The integer value
88        went into the wrong half of a long int.)
90    3.  If the --colour option was given to pcregrep with -v (invert match), it
91        did strange things, either producing crazy output, or crashing. It should,
92        of course, ignore a request for colour when reporting lines that do not
93        match.
95    4.  Another pcregrep bug caused similar problems if --colour was specified with
96        -M (multiline) and the pattern match finished with a line ending.
98    5.  In pcregrep, when a pattern that ended with a literal newline sequence was
99        matched in multiline mode, the following line was shown as part of the
100        match. This seems wrong, so I have changed it.
102    6.  Another pcregrep bug in multiline mode, when --colour was specified, caused
103        the check for further matches in the same line (so they could be coloured)
104        to overrun the end of the current line. If another match was found, it was
105        incorrectly shown (and then shown again when found in the next line).
107    7.  If pcregrep was compiled under Windows, there was a reference to the
108        function pcregrep_exit() before it was defined. I am assuming this was
109        the cause of the "error C2371: 'pcregrep_exit' : redefinition;" that was
110        reported by a user. I've moved the definition above the reference.
113    Version 8.11 10-Dec-2010
114    ------------------------
116    1.  (*THEN) was not working properly if there were untried alternatives prior
117        to it in the current branch. For example, in ((a|b)(*THEN)(*F)|c..) it
118        backtracked to try for "b" instead of moving to the next alternative branch
119        at the same level (in this case, to look for "c"). The Perl documentation
120        is clear that when (*THEN) is backtracked onto, it goes to the "next
121        alternative in the innermost enclosing group".
123    2.  (*COMMIT) was not overriding (*THEN), as it does in Perl. In a pattern
124        such as   (A(*COMMIT)B(*THEN)C|D)  any failure after matching A should
125        result in overall failure. Similarly, (*COMMIT) now overrides (*PRUNE) and
126        (*SKIP), (*SKIP) overrides (*PRUNE) and (*THEN), and (*PRUNE) overrides
127        (*THEN).
129    3.  If \s appeared in a character class, it removed the VT character from
130        the class, even if it had been included by some previous item, for example
131        in [\x00-\xff\s]. (This was a bug related to the fact that VT is not part
132        of \s, but is part of the POSIX "space" class.)
134    4.  A partial match never returns an empty string (because you can always
135        match an empty string at the end of the subject); however the checking for
136        an empty string was starting at the "start of match" point. This has been
137        changed to the "earliest inspected character" point, because the returned
138        data for a partial match starts at this character. This means that, for
139        example, /(?<=abc)def/ gives a partial match for the subject "abc"
140        (previously it gave "no match").
142    5.  Changes have been made to the way PCRE_PARTIAL_HARD affects the matching
143        of $, \z, \Z, \b, and \B. If the match point is at the end of the string,
144        previously a full match would be given. However, setting PCRE_PARTIAL_HARD
145        has an implication that the given string is incomplete (because a partial
146        match is preferred over a full match). For this reason, these items now
147        give a partial match in this situation. [Aside: previously, the one case
148        /t\b/ matched against "cat" with PCRE_PARTIAL_HARD set did return a partial
149        match rather than a full match, which was wrong by the old rules, but is
150        now correct.]
152    6.  There was a bug in the handling of #-introduced comments, recognized when
153        PCRE_EXTENDED is set, when PCRE_NEWLINE_ANY and PCRE_UTF8 were also set.
154        If a UTF-8 multi-byte character included the byte 0x85 (e.g. +U0445, whose
155        UTF-8 encoding is 0xd1,0x85), this was misinterpreted as a newline when
156        scanning for the end of the comment. (*Character* 0x85 is an "any" newline,
157        but *byte* 0x85 is not, in UTF-8 mode). This bug was present in several
158        places in pcre_compile().
160    7.  Related to (6) above, when pcre_compile() was skipping #-introduced
161        comments when looking ahead for named forward references to subpatterns,
162        the only newline sequence it recognized was NL. It now handles newlines
163        according to the set newline convention.
165    8.  SunOS4 doesn't have strerror() or strtoul(); pcregrep dealt with the
166        former, but used strtoul(), whereas pcretest avoided strtoul() but did not
167        cater for a lack of strerror(). These oversights have been fixed.
169    9.  Added --match-limit and --recursion-limit to pcregrep.
171    10. Added two casts needed to build with Visual Studio when NO_RECURSE is set.
173    11. When the -o option was used, pcregrep was setting a return code of 1, even
174        when matches were found, and --line-buffered was not being honoured.
176    12. Added an optional parentheses number to the -o and --only-matching options
177        of pcregrep.
179    13. Imitating Perl's /g action for multiple matches is tricky when the pattern
180        can match an empty string. The code to do it in pcretest and pcredemo
181        needed fixing:
183        (a) When the newline convention was "crlf", pcretest got it wrong, skipping
184            only one byte after an empty string match just before CRLF (this case
185            just got forgotten; "any" and "anycrlf" were OK).
187        (b) The pcretest code also had a bug, causing it to loop forever in UTF-8
188            mode when an empty string match preceded an ASCII character followed by
189            a non-ASCII character. (The code for advancing by one character rather
190            than one byte was nonsense.)
192        (c) The pcredemo.c sample program did not have any code at all to handle
193            the cases when CRLF is a valid newline sequence.
195    14. Neither pcre_exec() nor pcre_dfa_exec() was checking that the value given
196        as a starting offset was within the subject string. There is now a new
197        error, PCRE_ERROR_BADOFFSET, which is returned if the starting offset is
198        negative or greater than the length of the string. In order to test this,
199        pcretest is extended to allow the setting of negative starting offsets.
201    15. In both pcre_exec() and pcre_dfa_exec() the code for checking that the
202        starting offset points to the beginning of a UTF-8 character was
203        unnecessarily clumsy. I tidied it up.
205    16. Added PCRE_ERROR_SHORTUTF8 to make it possible to distinguish between a
206        bad UTF-8 sequence and one that is incomplete when using PCRE_PARTIAL_HARD.
208    17. Nobody had reported that the --include_dir option, which was added in
209        release 7.7 should have been called --include-dir (hyphen, not underscore)
210        for compatibility with GNU grep. I have changed it to --include-dir, but
211        left --include_dir as an undocumented synonym, and the same for
212        --exclude-dir, though that is not available in GNU grep, at least as of
213        release 2.5.4.
215    18. At a user's suggestion, the macros GETCHAR and friends (which pick up UTF-8
216        characters from a string of bytes) have been redefined so as not to use
217        loops, in order to improve performance in some environments. At the same
218        time, I abstracted some of the common code into auxiliary macros to save
219        repetition (this should not affect the compiled code).
221    19. If \c was followed by a multibyte UTF-8 character, bad things happened. A
222        compile-time error is now given if \c is not followed by an ASCII
223        character, that is, a byte less than 128. (In EBCDIC mode, the code is
224        different, and any byte value is allowed.)
226    20. Recognize (*NO_START_OPT) at the start of a pattern to set the PCRE_NO_
227        START_OPTIMIZE option, which is now allowed at compile time - but just
228        passed through to pcre_exec() or pcre_dfa_exec(). This makes it available
229        to pcregrep and other applications that have no direct access to PCRE
230        options. The new /Y option in pcretest sets this option when calling
231        pcre_compile().
233    21. Change 18 of release 8.01 broke the use of named subpatterns for recursive
234        back references. Groups containing recursive back references were forced to
235        be atomic by that change, but in the case of named groups, the amount of
236        memory required was incorrectly computed, leading to "Failed: internal
237        error: code overflow". This has been fixed.
239    22. Some patches to pcre_stringpiece.h, pcre_stringpiece_unittest.cc, and
240        pcretest.c, to avoid build problems in some Borland environments.
243    Version 8.10 25-Jun-2010
244    ------------------------
246    1.  Added support for (*MARK:ARG) and for ARG additions to PRUNE, SKIP, and
247        THEN.
249    2.  (*ACCEPT) was not working when inside an atomic group.
251    3.  Inside a character class, \B is treated as a literal by default, but
252        faulted if PCRE_EXTRA is set. This mimics Perl's behaviour (the -w option
253        causes the error). The code is unchanged, but I tidied the documentation.
255    4.  Inside a character class, PCRE always treated \R and \X as literals,
256        whereas Perl faults them if its -w option is set. I have changed PCRE so
257        that it faults them when PCRE_EXTRA is set.
259    5.  Added support for \N, which always matches any character other than
260        newline. (It is the same as "." when PCRE_DOTALL is not set.)
262    6.  When compiling pcregrep with newer versions of gcc which may have
263        FORTIFY_SOURCE set, several warnings "ignoring return value of 'fwrite',
264        declared with attribute warn_unused_result" were given. Just casting the
265        result to (void) does not stop the warnings; a more elaborate fudge is
266        needed. I've used a macro to implement this.
268    7.  Minor change to pcretest.c to avoid a compiler warning.
270    8.  Added four artifical Unicode properties to help with an option to make
271        \s etc use properties (see next item). The new properties are: Xan
272        (alphanumeric), Xsp (Perl space), Xps (POSIX space), and Xwd (word).
274    9.  Added PCRE_UCP to make \b, \d, \s, \w, and certain POSIX character classes
275        use Unicode properties. (*UCP) at the start of a pattern can be used to set
276        this option. Modified pcretest to add /W to test this facility. Added
277        REG_UCP to make it available via the POSIX interface.
279    10. Added --line-buffered to pcregrep.
281    11. In UTF-8 mode, if a pattern that was compiled with PCRE_CASELESS was
282        studied, and the match started with a letter with a code point greater than
283        127 whose first byte was different to the first byte of the other case of
284        the letter, the other case of this starting letter was not recognized
285        (#976).
287    12. If a pattern that was studied started with a repeated Unicode property
288        test, for example, \p{Nd}+, there was the theoretical possibility of
289        setting up an incorrect bitmap of starting bytes, but fortunately it could
290        not have actually happened in practice until change 8 above was made (it
291        added property types that matched character-matching opcodes).
293    13. pcre_study() now recognizes \h, \v, and \R when constructing a bit map of
294        possible starting bytes for non-anchored patterns.
296    14. Extended the "auto-possessify" feature of pcre_compile(). It now recognizes
297        \R, and also a number of cases that involve Unicode properties, both
298        explicit and implicit when PCRE_UCP is set.
300    15. If a repeated Unicode property match (e.g. \p{Lu}*) was used with non-UTF-8
301        input, it could crash or give wrong results if characters with values
302        greater than 0xc0 were present in the subject string. (Detail: it assumed
303        UTF-8 input when processing these items.)
305    16. Added a lot of (int) casts to avoid compiler warnings in systems where
306        size_t is 64-bit (#991).
308    17. Added a check for running out of memory when PCRE is compiled with
309        --disable-stack-for-recursion (#990).
311    18. If the last data line in a file for pcretest does not have a newline on
312        the end, a newline was missing in the output.
314    19. The default pcre_chartables.c file recognizes only ASCII characters (values
315        less than 128) in its various bitmaps. However, there is a facility for
316        generating tables according to the current locale when PCRE is compiled. It
317        turns out that in some environments, 0x85 and 0xa0, which are Unicode space
318        characters, are recognized by isspace() and therefore were getting set in
319        these tables, and indeed these tables seem to approximate to ISO 8859. This
320        caused a problem in UTF-8 mode when pcre_study() was used to create a list
321        of bytes that can start a match. For \s, it was including 0x85 and 0xa0,
322        which of course cannot start UTF-8 characters. I have changed the code so
323        that only real ASCII characters (less than 128) and the correct starting
324        bytes for UTF-8 encodings are set for characters greater than 127 when in
325        UTF-8 mode. (When PCRE_UCP is set - see 9 above - the code is different
326        altogether.)
328    20. Added the /T option to pcretest so as to be able to run tests with non-
329        standard character tables, thus making it possible to include the tests
330        used for 19 above in the standard set of tests.
332    21. A pattern such as (?&t)(?#()(?(DEFINE)(?<t>a)) which has a forward
333        reference to a subpattern the other side of a comment that contains an
334        opening parenthesis caused either an internal compiling error, or a
335        reference to the wrong subpattern.
338    Version 8.02 19-Mar-2010
339    ------------------------
341    1.  The Unicode data tables have been updated to Unicode 5.2.0.
343    2.  Added the option --libs-cpp to pcre-config, but only when C++ support is
344        configured.
346    3.  Updated the licensing terms in the pcregexp.pas file, as agreed with the
347        original author of that file, following a query about its status.
349    4.  On systems that do not have stdint.h (e.g. Solaris), check for and include
350        inttypes.h instead. This fixes a bug that was introduced by change 8.01/8.
352    5.  A pattern such as (?&t)*+(?(DEFINE)(?<t>.)) which has a possessive
353        quantifier applied to a forward-referencing subroutine call, could compile
354        incorrect code or give the error "internal error: previously-checked
355        referenced subpattern not found".
357    6.  Both MS Visual Studio and Symbian OS have problems with initializing
358        variables to point to external functions. For these systems, therefore,
359        pcre_malloc etc. are now initialized to local functions that call the
360        relevant global functions.
362    7.  There were two entries missing in the vectors called coptable and poptable
363        in pcre_dfa_exec.c. This could lead to memory accesses outsize the vectors.
364        I've fixed the data, and added a kludgy way of testing at compile time that
365        the lengths are correct (equal to the number of opcodes).
367    8.  Following on from 7, I added a similar kludge to check the length of the
368        eint vector in pcreposix.c.
370    9.  Error texts for pcre_compile() are held as one long string to avoid too
371        much relocation at load time. To find a text, the string is searched,
372        counting zeros. There was no check for running off the end of the string,
373        which could happen if a new error number was added without updating the
374        string.
376    10. \K gave a compile-time error if it appeared in a lookbehind assersion.
378    11. \K was not working if it appeared in an atomic group or in a group that
379        was called as a "subroutine", or in an assertion. Perl 5.11 documents that
380        \K is "not well defined" if used in an assertion. PCRE now accepts it if
381        the assertion is positive, but not if it is negative.
383    12. Change 11 fortuitously reduced the size of the stack frame used in the
384        "match()" function of pcre_exec.c by one pointer. Forthcoming
385        implementation of support for (*MARK) will need an extra pointer on the
386        stack; I have reserved it now, so that the stack frame size does not
387        decrease.
389    13. A pattern such as (?P<L1>(?P<L2>0)|(?P>L2)(?P>L1)) in which the only other
390        item in branch that calls a recursion is a subroutine call - as in the
391        second branch in the above example - was incorrectly given the compile-
392        time error "recursive call could loop indefinitely" because pcre_compile()
393        was not correctly checking the subroutine for matching a non-empty string.
395    14. The checks for overrunning compiling workspace could trigger after an
396        overrun had occurred. This is a "should never occur" error, but it can be
397        triggered by pathological patterns such as hundreds of nested parentheses.
398        The checks now trigger 100 bytes before the end of the workspace.
400    15. Fix typo in configure.ac: "srtoq" should be "strtoq".
403    Version 8.01 19-Jan-2010
404    ------------------------
406    1.  If a pattern contained a conditional subpattern with only one branch (in
407        particular, this includes all (*DEFINE) patterns), a call to pcre_study()
408        computed the wrong minimum data length (which is of course zero for such
409        subpatterns). This could cause incorrect "no match" results.
411    2.  For patterns such as (?i)a(?-i)b|c where an option setting at the start of
412        the pattern is reset in the first branch, pcre_compile() failed with
413        "internal error: code overflow at offset...". This happened only when
414        the reset was to the original external option setting. (An optimization
415        abstracts leading options settings into an external setting, which was the
416        cause of this.)
418    3.  A pattern such as ^(?!a(*SKIP)b) where a negative assertion contained one
419        of the verbs SKIP, PRUNE, or COMMIT, did not work correctly. When the
420        assertion pattern did not match (meaning that the assertion was true), it
421        was incorrectly treated as false if the SKIP had been reached during the
422        matching. This also applied to assertions used as conditions.
424    4.  If an item that is not supported by pcre_dfa_exec() was encountered in an
425        assertion subpattern, including such a pattern used as a condition,
426        unpredictable results occurred, instead of the error return
429    5.  The C++ GlobalReplace function was not working like Perl for the special
430        situation when an empty string is matched. It now does the fancy magic
431        stuff that is necessary.
433    6.  In pcre_internal.h, obsolete includes to setjmp.h and stdarg.h have been
434        removed. (These were left over from very, very early versions of PCRE.)
436    7.  Some cosmetic changes to the code to make life easier when compiling it
437        as part of something else:
439        (a) Change DEBUG to PCRE_DEBUG.
441        (b) In pcre_compile(), rename the member of the "branch_chain" structure
442            called "current" as "current_branch", to prevent a collision with the
443            Linux macro when compiled as a kernel module.
445        (c) In pcre_study(), rename the function set_bit() as set_table_bit(), to
446            prevent a collision with the Linux macro when compiled as a kernel
447            module.
449    8.  In pcre_compile() there are some checks for integer overflows that used to
450        cast potentially large values to (double). This has been changed to that
451        when building, a check for int64_t is made, and if it is found, it is used
452        instead, thus avoiding the use of floating point arithmetic. (There is no
453        other use of FP in PCRE.) If int64_t is not found, the fallback is to
454        double.
456    9.  Added two casts to avoid signed/unsigned warnings from VS Studio Express
457        2005 (difference between two addresses compared to an unsigned value).
459    10. Change the standard AC_CHECK_LIB test for libbz2 in configure.ac to a
460        custom one, because of the following reported problem in Windows:
462          - libbz2 uses the Pascal calling convention (WINAPI) for the functions
463              under Win32.
464          - The standard autoconf AC_CHECK_LIB fails to include "bzlib.h",
465              therefore missing the function definition.
466          - The compiler thus generates a "C" signature for the test function.
467          - The linker fails to find the "C" function.
468          - PCRE fails to configure if asked to do so against libbz2.
470    11. When running libtoolize from libtool-2.2.6b as part of autogen.sh, these
471        messages were output:
473          Consider adding `AC_CONFIG_MACRO_DIR([m4])' to configure.ac and
474          rerunning libtoolize, to keep the correct libtool macros in-tree.
475          Consider adding `-I m4' to ACLOCAL_AMFLAGS in Makefile.am.
477        I have done both of these things.
479    12. Although pcre_dfa_exec() does not use nearly as much stack as pcre_exec()
480        most of the time, it *can* run out if it is given a pattern that contains a
481        runaway infinite recursion. I updated the discussion in the pcrestack man
482        page.
484    13. Now that we have gone to the x.xx style of version numbers, the minor
485        version may start with zero. Using 08 or 09 is a bad idea because users
486        might check the value of PCRE_MINOR in their code, and 08 or 09 may be
487        interpreted as invalid octal numbers. I've updated the previous comment in
488        configure.ac, and also added a check that gives an error if 08 or 09 are
489        used.
491    14. Change 8.00/11 was not quite complete: code had been accidentally omitted,
492        causing partial matching to fail when the end of the subject matched \W
493        in a UTF-8 pattern where \W was quantified with a minimum of 3.
495    15. There were some discrepancies between the declarations in pcre_internal.h
496        of _pcre_is_newline(), _pcre_was_newline(), and _pcre_valid_utf8() and
497        their definitions. The declarations used "const uschar *" and the
498        definitions used USPTR. Even though USPTR is normally defined as "const
499        unsigned char *" (and uschar is typedeffed as "unsigned char"), it was
500        reported that: "This difference in casting confuses some C++ compilers, for
501        example, SunCC recognizes above declarations as different functions and
502        generates broken code for hbpcre." I have changed the declarations to use
503        USPTR.
505    16. GNU libtool is named differently on some systems. The autogen.sh script now
506        tries several variants such as glibtoolize (MacOSX) and libtoolize1x
507        (FreeBSD).
509    17. Applied Craig's patch that fixes an HP aCC compile error in pcre 8.00
510        (strtoXX undefined when compiling pcrecpp.cc). The patch contains this
511        comment: "Figure out how to create a longlong from a string: strtoll and
512        equivalent. It's not enough to call AC_CHECK_FUNCS: hpux has a strtoll, for
513        instance, but it only takes 2 args instead of 3!"
515    18. A subtle bug concerned with back references has been fixed by a change of
516        specification, with a corresponding code fix. A pattern such as
517        ^(xa|=?\1a)+$ which contains a back reference inside the group to which it
518        refers, was giving matches when it shouldn't. For example, xa=xaaa would
519        match that pattern. Interestingly, Perl (at least up to 5.11.3) has the
520        same bug. Such groups have to be quantified to be useful, or contained
521        inside another quantified group. (If there's no repetition, the reference
522        can never match.) The problem arises because, having left the group and
523        moved on to the rest of the pattern, a later failure that backtracks into
524        the group uses the captured value from the final iteration of the group
525        rather than the correct earlier one. I have fixed this in PCRE by forcing
526        any group that contains a reference to itself to be an atomic group; that
527        is, there cannot be any backtracking into it once it has completed. This is
528        similar to recursive and subroutine calls.
531    Version 8.00 19-Oct-09
532  ----------------------  ----------------------
534  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
535      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
536      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
537      error.      error.
539  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,
540      "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
541      in a Windows environment.      in a Windows environment.
543  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
544      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
545      --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
546      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
547      prints the file name in this circumstance, but including the count seems      prints the file name in this circumstance, but including the count seems
548      more useful - otherwise, why use --count?) Also ensured that the      more useful - otherwise, why use --count?) Also ensured that the
549      combination -clh just lists non-zero counts, with no names.      combination -clh just lists non-zero counts, with no names.
551    4.  The long form of the pcregrep -F option was incorrectly implemented as
552        --fixed_strings instead of --fixed-strings. This is an incompatible change,
553        but it seems right to fix it, and I didn't think it was worth preserving
554        the old behaviour.
556    5.  The command line items --regex=pattern and --regexp=pattern were not
557        recognized by pcregrep, which required --regex pattern or --regexp pattern
558        (with a space rather than an '='). The man page documented the '=' forms,
559        which are compatible with GNU grep; these now work.
561    6.  No libpcreposix.pc file was created for pkg-config; there was just
562        libpcre.pc and libpcrecpp.pc. The omission has been rectified.
564    7.  Added #ifndef SUPPORT_UCP into the pcre_ucd.c module, to reduce its size
565        when UCP support is not needed, by modifying the Python script that
566        generates it from Unicode data files. This should not matter if the module
567        is correctly used as a library, but I received one complaint about 50K of
568        unwanted data. My guess is that the person linked everything into his
569        program rather than using a library. Anyway, it does no harm.
571    8.  A pattern such as /\x{123}{2,2}+/8 was incorrectly compiled; the trigger
572        was a minimum greater than 1 for a wide character in a possessive
573        repetition. The same bug could also affect patterns like /(\x{ff}{0,2})*/8
574        which had an unlimited repeat of a nested, fixed maximum repeat of a wide
575        character. Chaos in the form of incorrect output or a compiling loop could
576        result.
578    9.  The restrictions on what a pattern can contain when partial matching is
579        requested for pcre_exec() have been removed. All patterns can now be
580        partially matched by this function. In addition, if there are at least two
581        slots in the offset vector, the offset of the earliest inspected character
582        for the match and the offset of the end of the subject are set in them when
583        PCRE_ERROR_PARTIAL is returned.
585    10. Partial matching has been split into two forms: PCRE_PARTIAL_SOFT, which is
586        synonymous with PCRE_PARTIAL, for backwards compatibility, and
587        PCRE_PARTIAL_HARD, which causes a partial match to supersede a full match,
588        and may be more useful for multi-segment matching.
590    11. Partial matching with pcre_exec() is now more intuitive. A partial match
591        used to be given if ever the end of the subject was reached; now it is
592        given only if matching could not proceed because another character was
593        needed. This makes a difference in some odd cases such as Z(*FAIL) with the
594        string "Z", which now yields "no match" instead of "partial match". In the
595        case of pcre_dfa_exec(), "no match" is given if every matching path for the
596        final character ended with (*FAIL).
598    12. Restarting a match using pcre_dfa_exec() after a partial match did not work
599        if the pattern had a "must contain" character that was already found in the
600        earlier partial match, unless partial matching was again requested. For
601        example, with the pattern /dog.(body)?/, the "must contain" character is
602        "g". If the first part-match was for the string "dog", restarting with
603        "sbody" failed. This bug has been fixed.
605    13. The string returned by pcre_dfa_exec() after a partial match has been
606        changed so that it starts at the first inspected character rather than the
607        first character of the match. This makes a difference only if the pattern
608        starts with a lookbehind assertion or \b or \B (\K is not supported by
609        pcre_dfa_exec()). It's an incompatible change, but it makes the two
610        matching functions compatible, and I think it's the right thing to do.
612    14. Added a pcredemo man page, created automatically from the pcredemo.c file,
613        so that the demonstration program is easily available in environments where
614        PCRE has not been installed from source.
616    15. Arranged to add -DPCRE_STATIC to cflags in libpcre.pc, libpcreposix.cp,
617        libpcrecpp.pc and pcre-config when PCRE is not compiled as a shared
618        library.
620    16. Added REG_UNGREEDY to the pcreposix interface, at the request of a user.
621        It maps to PCRE_UNGREEDY. It is not, of course, POSIX-compatible, but it
622        is not the first non-POSIX option to be added. Clearly some people find
623        these options useful.
625    17. If a caller to the POSIX matching function regexec() passes a non-zero
626        value for nmatch with a NULL value for pmatch, the value of
627        nmatch is forced to zero.
629    18. RunGrepTest did not have a test for the availability of the -u option of
630        the diff command, as RunTest does. It now checks in the same way as
631        RunTest, and also checks for the -b option.
633    19. If an odd number of negated classes containing just a single character
634        interposed, within parentheses, between a forward reference to a named
635        subpattern and the definition of the subpattern, compilation crashed with
636        an internal error, complaining that it could not find the referenced
637        subpattern. An example of a crashing pattern is /(?&A)(([^m])(?<A>))/.
638        [The bug was that it was starting one character too far in when skipping
639        over the character class, thus treating the ] as data rather than
640        terminating the class. This meant it could skip too much.]
642    20. Added PCRE_NOTEMPTY_ATSTART in order to be able to correctly implement the
643        /g option in pcretest when the pattern contains \K, which makes it possible
644        to have an empty string match not at the start, even when the pattern is
645        anchored. Updated pcretest and pcredemo to use this option.
647    21. If the maximum number of capturing subpatterns in a recursion was greater
648        than the maximum at the outer level, the higher number was returned, but
649        with unset values at the outer level. The correct (outer level) value is
650        now given.
652    22. If (*ACCEPT) appeared inside capturing parentheses, previous releases of
653        PCRE did not set those parentheses (unlike Perl). I have now found a way to
654        make it do so. The string so far is captured, making this feature
655        compatible with Perl.
657    23. The tests have been re-organized, adding tests 11 and 12, to make it
658        possible to check the Perl 5.10 features against Perl 5.10.
660    24. Perl 5.10 allows subroutine calls in lookbehinds, as long as the subroutine
661        pattern matches a fixed length string. PCRE did not allow this; now it
662        does. Neither allows recursion.
664    25. I finally figured out how to implement a request to provide the minimum
665        length of subject string that was needed in order to match a given pattern.
666        (It was back references and recursion that I had previously got hung up
667        on.) This code has now been added to pcre_study(); it finds a lower bound
668        to the length of subject needed. It is not necessarily the greatest lower
669        bound, but using it to avoid searching strings that are too short does give
670        some useful speed-ups. The value is available to calling programs via
671        pcre_fullinfo().
673    26. While implementing 25, I discovered to my embarrassment that pcretest had
674        not been passing the result of pcre_study() to pcre_dfa_exec(), so the
675        study optimizations had never been tested with that matching function.
676        Oops. What is worse, even when it was passed study data, there was a bug in
677        pcre_dfa_exec() that meant it never actually used it. Double oops. There
678        were also very few tests of studied patterns with pcre_dfa_exec().
680    27. If (?| is used to create subpatterns with duplicate numbers, they are now
681        allowed to have the same name, even if PCRE_DUPNAMES is not set. However,
682        on the other side of the coin, they are no longer allowed to have different
683        names, because these cannot be distinguished in PCRE, and this has caused
684        confusion. (This is a difference from Perl.)
686    28. When duplicate subpattern names are present (necessarily with different
687        numbers, as required by 27 above), and a test is made by name in a
688        conditional pattern, either for a subpattern having been matched, or for
689        recursion in such a pattern, all the associated numbered subpatterns are
690        tested, and the overall condition is true if the condition is true for any
691        one of them. This is the way Perl works, and is also more like the way
692        testing by number works.
695  Version 7.9 11-Apr-09  Version 7.9 11-Apr-09
696  ---------------------  ---------------------

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