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revision 83 by nigel, Sat Feb 24 21:41:06 2007 UTC revision 216 by ph10, Wed Aug 15 14:35:57 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
4    Version 7.3 09-Aug-07
5    ---------------------
7     1. In the rejigging of the build system that eventually resulted in 7.1, the
8        line "#include <pcre.h>" was included in pcre_internal.h. The use of angle
9        brackets there is not right, since it causes compilers to look for an
10        installed pcre.h, not the version that is in the source that is being
11        compiled (which of course may be different). I have changed it back to:
13          #include "pcre.h"
15        I have a vague recollection that the change was concerned with compiling in
16        different directories, but in the new build system, that is taken care of
17        by the VPATH setting the Makefile.
19     2. The pattern .*$ when run in not-DOTALL UTF-8 mode with newline=any failed
20        when the subject happened to end in the byte 0x85 (e.g. if the last
21        character was \x{1ec5}). *Character* 0x85 is one of the "any" newline
22        characters but of course it shouldn't be taken as a newline when it is part
23        of another character. The bug was that, for an unlimited repeat of . in
24        not-DOTALL UTF-8 mode, PCRE was advancing by bytes rather than by
25        characters when looking for a newline.
27     3. A small performance improvement in the DOTALL UTF-8 mode .* case.
29     4. Debugging: adjusted the names of opcodes for different kinds of parentheses
30        in debug output.
32     5. Arrange to use "%I64d" instead of "%lld" and "%I64u" instead of "%llu" for
33        long printing in the pcrecpp unittest when running under MinGW.
35     6. ESC_K was left out of the EBCDIC table.
37     7. Change 7.0/38 introduced a new limit on the number of nested non-capturing
38        parentheses; I made it 1000, which seemed large enough. Unfortunately, the
39        limit also applies to "virtual nesting" when a pattern is recursive, and in
40        this case 1000 isn't so big. I have been able to remove this limit at the
41        expense of backing off one optimization in certain circumstances. Normally,
42        when pcre_exec() would call its internal match() function recursively and
43        immediately return the result unconditionally, it uses a "tail recursion"
44        feature to save stack. However, when a subpattern that can match an empty
45        string has an unlimited repetition quantifier, it no longer makes this
46        optimization. That gives it a stack frame in which to save the data for
47        checking that an empty string has been matched. Previously this was taken
48        from the 1000-entry workspace that had been reserved. So now there is no
49        explicit limit, but more stack is used.
51     8. Applied Daniel's patches to solve problems with the import/export magic
52        syntax that is required for Windows, and which was going wrong for the
53        pcreposix and pcrecpp parts of the library. These were overlooked when this
54        problem was solved for the main library.
56     9. There were some crude static tests to avoid integer overflow when computing
57        the size of patterns that contain repeated groups with explicit upper
58        limits. As the maximum quantifier is 65535, the maximum group length was
59        set at 30,000 so that the product of these two numbers did not overflow a
60        32-bit integer. However, it turns out that people want to use groups that
61        are longer than 30,000 bytes (though not repeat them that many times).
62        Change 7.0/17 (the refactoring of the way the pattern size is computed) has
63        made it possible to implement the integer overflow checks in a much more
64        dynamic way, which I have now done. The artificial limitation on group
65        length has been removed - we now have only the limit on the total length of
66        the compiled pattern, which depends on the LINK_SIZE setting.
68    10. Fixed a bug in the documentation for get/copy named substring when
69        duplicate names are permitted. If none of the named substrings are set, the
70        functions return PCRE_ERROR_NOSUBSTRING (7); the doc said they returned an
71        empty string.
73    11. Because Perl interprets \Q...\E at a high level, and ignores orphan \E
74        instances, patterns such as [\Q\E] or [\E] or even [^\E] cause an error,
75        because the ] is interpreted as the first data character and the
76        terminating ] is not found. PCRE has been made compatible with Perl in this
77        regard. Previously, it interpreted [\Q\E] as an empty class, and [\E] could
78        cause memory overwriting.
80    10. Like Perl, PCRE automatically breaks an unlimited repeat after an empty
81        string has been matched (to stop an infinite loop). It was not recognizing
82        a conditional subpattern that could match an empty string if that
83        subpattern was within another subpattern. For example, it looped when
84        trying to match  (((?(1)X|))*)  but it was OK with  ((?(1)X|)*)  where the
85        condition was not nested. This bug has been fixed.
87    12. A pattern like \X?\d or \P{L}?\d in non-UTF-8 mode could cause a backtrack
88        past the start of the subject in the presence of bytes with the top bit
89        set, for example "\x8aBCD".
91    13. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
92        (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
94    14. Optimized (?!) to (*FAIL).
96    15. Updated the test for a valid UTF-8 string to conform to the later RFC 3629.
97        This restricts code points to be within the range 0 to 0x10FFFF, excluding
98        the "low surrogate" sequence 0xD800 to 0xDFFF. Previously, PCRE allowed the
99        full range 0 to 0x7FFFFFFF, as defined by RFC 2279. Internally, it still
100        does: it's just the validity check that is more restrictive.
102    16. Inserted checks for integer overflows during escape sequence (backslash)
103        processing, and also fixed erroneous offset values for syntax errors during
104        backslash processing.
106    17. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
107        for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
109    18. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
110        caused an overrun.
112    19. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
113        something other than just ASCII characters) inside a group that had an
114        unlimited repeat caused a loop at compile time (while checking to see
115        whether the group could match an empty string).
118    Version 7.2 19-Jun-07
119    ---------------------
121     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
122        which is apparently normally available under Windows.
124     2. Re-jig the pcregrep tests with different newline settings in an attempt
125        to make them independent of the local environment's newline setting.
127     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
129     4. Some of the "internals" tests were previously cut out when the link size
130        was not 2, because the output contained actual offsets. The recent new
131        "Z" feature of pcretest means that these can be cut out, making the tests
132        usable with all link sizes.
134     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
135        stack recursion. This gives a massive performance boost under BSD, but just
136        a small improvement under Linux. However, it saves one field in the frame
137        in all cases.
139     6. Added more features from the forthcoming Perl 5.10:
141        (a) (?-n) (where n is a string of digits) is a relative subroutine or
142            recursion call. It refers to the nth most recently opened parentheses.
144        (b) (?+n) is also a relative subroutine call; it refers to the nth next
145            to be opened parentheses.
147        (c) Conditions that refer to capturing parentheses can be specified
148            relatively, for example, (?(-2)... or (?(+3)...
150        (d) \K resets the start of the current match so that everything before
151            is not part of it.
153        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
155        (f) \g{name} is another synonym - part of Perl 5.10's unification of
156            reference syntax.
158        (g) (?| introduces a group in which the numbering of parentheses in each
159            alternative starts with the same number.
161        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
163     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
166     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
167        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
168        for detecting groups that can match an empty string.
170     9. A pattern with a very large number of alternatives (more than several
171        hundred) was running out of internal workspace during the pre-compile
172        phase, where pcre_compile() figures out how much memory will be needed. A
173        bit of new cunning has reduced the workspace needed for groups with
174        alternatives. The 1000-alternative test pattern now uses 12 bytes of
175        workspace instead of running out of the 4096 that are available.
177    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
179    11. Applied patch from Google to remove an optimization that didn't quite work.
180        The report of the bug said:
182          pcrecpp::RE("a*").FullMatch("aaa") matches, while
183          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
184          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
186    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
187        it matched the wrong number of bytes.
190    Version 7.1 24-Apr-07
191    ---------------------
193     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
194        that is more "standard", making use of automake and other Autotools. There
195        is some re-arrangement of the files and adjustment of comments consequent
196        on this.
198     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
199        for recursive directory scanning broke on some systems because the files
200        are not scanned in any specific order and on different systems the order
201        was different. A call to "sort" has been inserted into RunGrepTest for the
202        approprate test as a short-term fix. In the longer term there may be an
203        alternative.
205     3. I had an email from Eric Raymond about problems translating some of PCRE's
206        man pages to HTML (despite the fact that I distribute HTML pages, some
207        people do their own conversions for various reasons). The problems
208        concerned the use of low-level troff macros .br and .in. I have therefore
209        removed all such uses from the man pages (some were redundant, some could
210        be replaced by .nf/.fi pairs). The 132html script that I use to generate
211        HTML has been updated to handle .nf/.fi and to complain if it encounters
212        .br or .in.
214     4. Updated comments in configure.ac that get placed in config.h.in and also
215        arranged for config.h to be included in the distribution, with the name
216        config.h.generic, for the benefit of those who have to compile without
217        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
219     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
220        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
221        makevp.bat for the current PCRE, using the additional files
222        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
224     6. A Windows user reported a minor discrepancy with test 2, which turned out
225        to be caused by a trailing space on an input line that had got lost in his
226        copy. The trailing space was an accident, so I've just removed it.
228     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
229        that is needed.
231     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
232        as "const" (a) because they are and (b) because it helps the PHP
233        maintainers who have recently made a script to detect big data structures
234        in the php code that should be moved to the .rodata section. I remembered
235        to update Builducptable as well, so it won't revert if ucptable.h is ever
236        re-created.
238     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
239        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
240        order to be able to cut out the UTF-8 tables in the latter when UTF-8
241        support is not required. This saves 1.5-2K of code, which is important in
242        some applications.
244        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
245        so as not to refer to the tables, even though these functions will never be
246        called when UTF-8 support is disabled. Otherwise there are problems with a
247        shared library.
249    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
251        (a) It was defining its arguments as char * instead of void *.
253        (b) It was assuming that all moves were upwards in memory; this was true
254            a long time ago when I wrote it, but is no longer the case.
256        The emulated memove() is provided for those environments that have neither
257        memmove() nor bcopy(). I didn't think anyone used it these days, but that
258        is clearly not the case, as these two bugs were recently reported.
260    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
261        and Detrail to create the HTML documentation, the .txt form of the man
262        pages, and it removes trailing spaces from listed files. It also creates
263        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
264        case, it wraps all the #defines with #ifndefs. This script should be run
265        before "make dist".
267    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
268        with Unicode property support.
270        (a) For a maximizing quantifier, if the two different cases of the
271            character were of different lengths in their UTF-8 codings (there are
272            some cases like this - I found 11), and the matching function had to
273            back up over a mixture of the two cases, it incorrectly assumed they
274            were both the same length.
276        (b) When PCRE was configured to use the heap rather than the stack for
277            recursion during matching, it was not correctly preserving the data for
278            the other case of a UTF-8 character when checking ahead for a match
279            while processing a minimizing repeat. If the check also involved
280            matching a wide character, but failed, corruption could cause an
281            erroneous result when trying to check for a repeat of the original
282            character.
284    13. Some tidying changes to the testing mechanism:
286        (a) The RunTest script now detects the internal link size and whether there
287            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
288            values substituted by "configure". (The RunGrepTest script already did
289            this for UTF-8.) The configure.ac script no longer substitutes the
290            relevant variables.
292        (b) The debugging options /B and /D in pcretest show the compiled bytecode
293            with length and offset values. This means that the output is different
294            for different internal link sizes. Test 2 is skipped for link sizes
295            other than 2 because of this, bypassing the problem. Unfortunately,
296            there was also a test in test 3 (the locale tests) that used /B and
297            failed for link sizes other than 2. Rather than cut the whole test out,
298            I have added a new /Z option to pcretest that replaces the length and
299            offset values with spaces. This is now used to make test 3 independent
300            of link size. (Test 2 will be tidied up later.)
302    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
303        segmentation fault instead of returning the appropriate error message.
305    15. In multiline mode when the newline sequence was set to "any", the pattern
306        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
307        This doesn't seem right; it now treats the CRLF combination as the line
308        ending, and so does not match in that case. It's only a pattern such as ^$
309        that would hit this one: something like ^ABC$ would have failed after \r
310        and then tried again after \r\n.
312    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
313        in an attempt to make files that differ only in their line terminators
314        compare equal. This works on Linux.
316    17. Under certain error circumstances pcregrep might try to free random memory
317        as it exited. This is now fixed, thanks to valgrind.
319    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
320        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
321        was because its rules for how to advance for /g after matching an empty
322        string at the end of a line did not allow for this case. They now check for
323        it specially.
325    20. pcretest is supposed to handle patterns and data of any length, by
326        extending its buffers when necessary. It was getting this wrong when the
327        buffer for a data line had to be extended.
329    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
330        CRLF as a newline sequence.
332    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
333        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
334        I have nevertheless tidied it up.
336    23. Added some casts to kill warnings from HP-UX ia64 compiler.
338    24. Added a man page for pcre-config.
341    Version 7.0 19-Dec-06
342    ---------------------
344     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
345        moving to gcc 4.1.1.
347     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
348        sys/time.h, which is documented as needed for this function. It doesn't
349        seem to matter on Linux, but it showed up on some releases of OS X.
351     3. It seems that there are systems where bytes whose values are greater than
352        127 match isprint() in the "C" locale. The "C" locale should be the
353        default when a C program starts up. In most systems, only ASCII printing
354        characters match isprint(). This difference caused the output from pcretest
355        to vary, making some of the tests fail. I have changed pcretest so that:
357        (a) When it is outputting text in the compiled version of a pattern, bytes
358            other than 32-126 are always shown as hex escapes.
360        (b) When it is outputting text that is a matched part of a subject string,
361            it does the same, unless a different locale has been set for the match
362            (using the /L modifier). In this case, it uses isprint() to decide.
364     4. Fixed a major bug that caused incorrect computation of the amount of memory
365        required for a compiled pattern when options that changed within the
366        pattern affected the logic of the preliminary scan that determines the
367        length. The relevant options are -x, and -i in UTF-8 mode. The result was
368        that the computed length was too small. The symptoms of this bug were
369        either the PCRE error "internal error: code overflow" from pcre_compile(),
370        or a glibc crash with a message such as "pcretest: free(): invalid next
371        size (fast)". Examples of patterns that provoked this bug (shown in
372        pcretest format) are:
374          /(?-x: )/x
375          /(?x)(?-x: \s*#\s*)/
376          /((?i)[\x{c0}])/8
377          /(?i:[\x{c0}])/8
379        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
380        is now done differently.
382     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
383        wrapper classes; (b) implement a new function in the C++ scanner that is
384        more efficient than the old way of doing things because it avoids levels of
385        recursion in the regex matching; (c) add a paragraph to the documentation
386        for the FullMatch() function.
388     6. The escape sequence \n was being treated as whatever was defined as
389        "newline". Not only was this contrary to the documentation, which states
390        that \n is character 10 (hex 0A), but it also went horribly wrong when
391        "newline" was defined as CRLF. This has been fixed.
393     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
394        was being set to -1 for the "end of line" case (supposedly a value that no
395        character can have). Though this value is never used (the check for end of
396        line is "zero bytes in current character"), it caused compiler complaints.
397        I've changed it to 0xffffffff.
399     8. In pcre_version.c, the version string was being built by a sequence of
400        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
401        string (as it is for production releases) called a macro with an empty
402        argument. The C standard says the result of this is undefined. The gcc
403        compiler treats it as an empty string (which was what was wanted) but it is
404        reported that Visual C gives an error. The source has been hacked around to
405        avoid this problem.
407     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
408        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
409        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
410        of them did).
412    10. Originally, pcretest opened its input and output without "b"; then I was
413        told that "b" was needed in some environments, so it was added for release
414        5.0 to both the input and output. (It makes no difference on Unix-like
415        systems.) Later I was told that it is wrong for the input on Windows. I've
416        now abstracted the modes into two macros, to make it easier to fiddle with
417        them, and removed "b" from the input mode under Windows.
419    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
421    12. Added -help and --help to pcretest as an official way of being reminded
422        of the options.
424    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
425        and pcrecpp.cc because they annoy compilers at high warning levels.
427    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
429    15. Fixed an occurrence of == in configure.ac that should have been = (shell
430        scripts are not C programs :-) and which was not noticed because it works
431        on Linux.
433    16. pcretest is supposed to handle any length of pattern and data line (as one
434        line or as a continued sequence of lines) by extending its input buffer if
435        necessary. This feature was broken for very long pattern lines, leading to
436        a string of junk being passed to pcre_compile() if the pattern was longer
437        than about 50K.
439    17. I have done a major re-factoring of the way pcre_compile() computes the
440        amount of memory needed for a compiled pattern. Previously, there was code
441        that made a preliminary scan of the pattern in order to do this. That was
442        OK when PCRE was new, but as the facilities have expanded, it has become
443        harder and harder to keep it in step with the real compile phase, and there
444        have been a number of bugs (see for example, 4 above). I have now found a
445        cunning way of running the real compile function in a "fake" mode that
446        enables it to compute how much memory it would need, while actually only
447        ever using a few hundred bytes of working memory and without too many
448        tests of the mode. This should make future maintenance and development
449        easier. A side effect of this work is that the limit of 200 on the nesting
450        depth of parentheses has been removed (though this was never a serious
451        limitation, I suspect). However, there is a downside: pcre_compile() now
452        runs more slowly than before (30% or more, depending on the pattern). I
453        hope this isn't a big issue. There is no effect on runtime performance.
455    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
456        newline (only possible for the last line of a file) and it was a
457        pattern that set a locale (followed by /Lsomething), pcretest crashed.
459    19. Added additional timing features to pcretest. (1) The -tm option now times
460        matching only, not compiling. (2) Both -t and -tm can be followed, as a
461        separate command line item, by a number that specifies the number of
462        repeats to use when timing. The default is 50000; this gives better
463        precision, but takes uncomfortably long for very large patterns.
465    20. Extended pcre_study() to be more clever in cases where a branch of a
466        subpattern has no definite first character. For example, (a*|b*)[cd] would
467        previously give no result from pcre_study(). Now it recognizes that the
468        first character must be a, b, c, or d.
470    21. There was an incorrect error "recursive call could loop indefinitely" if
471        a subpattern (or the entire pattern) that was being tested for matching an
472        empty string contained only one non-empty item after a nested subpattern.
473        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
474        incorrectly, because the \d was being skipped in the check.
476    22. The pcretest program now has a new pattern option /B and a command line
477        option -b, which is equivalent to adding /B to every pattern. This causes
478        it to show the compiled bytecode, without the additional information that
479        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
480        is the same as /B/I).
482    23. A new optimization is now able automatically to treat some sequences such
483        as a*b as a*+b. More specifically, if something simple (such as a character
484        or a simple class like \d) has an unlimited quantifier, and is followed by
485        something that cannot possibly match the quantified thing, the quantifier
486        is automatically "possessified".
488    24. A recursive reference to a subpattern whose number was greater than 39
489        went wrong under certain circumstances in UTF-8 mode. This bug could also
490        have affected the operation of pcre_study().
492    25. Realized that a little bit of performance could be had by replacing
493        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
495    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
497    27. Possessive quantifiers such as a++ were previously implemented by turning
498        them into atomic groups such as ($>a+). Now they have their own opcodes,
499        which improves performance. This includes the automatically created ones
500        from 23 above.
502    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
503        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
504        the first matched character to be a colon. This applied both to named and
505        numbered groups.
507    29. The ucpinternal.h header file was missing its idempotency #ifdef.
509    30. I was sent a "project" file called libpcre.a.dev which I understand makes
510        building PCRE on Windows easier, so I have included it in the distribution.
512    31. There is now a check in pcretest against a ridiculously large number being
513        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
514        loop, the loop is abandoned.
516    32. Forward references to subpatterns in conditions such as (?(2)...) where
517        subpattern 2 is defined later cause pcre_compile() to search forwards in
518        the pattern for the relevant set of parentheses. This search went wrong
519        when there were unescaped parentheses in a character class, parentheses
520        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
522    33. "Subroutine" calls and backreferences were previously restricted to
523        referencing subpatterns earlier in the regex. This restriction has now
524        been removed.
526    34. Added a number of extra features that are going to be in Perl 5.10. On the
527        whole, these are just syntactic alternatives for features that PCRE had
528        previously implemented using the Python syntax or my own invention. The
529        other formats are all retained for compatibility.
531        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
532            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
533            also .NET compatible.
535        (b) A recursion or subroutine call to a named group can now be defined as
536            (?&name) as well as (?P>name).
538        (c) A backreference to a named group can now be defined as \k<name> or
539            \k'name' as well as (?P=name). The new forms, as well as being in Perl
540            5.10, are also .NET compatible.
542        (d) A conditional reference to a named group can now use the syntax
543            (?(<name>) or (?('name') as well as (?(name).
545        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
546            groups (named and numbered) that are never evaluated inline, but can be
547            called as "subroutines" from elsewhere. In effect, the DEFINE condition
548            is always false. There may be only one alternative in such a group.
550        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
551            as the simple (?(R). The condition is true only if the most recent
552            recursion is that of the given number or name. It does not search out
553            through the entire recursion stack.
555        (g) The escape \gN or \g{N} has been added, where N is a positive or
556            negative number, specifying an absolute or relative reference.
558    35. Tidied to get rid of some further signed/unsigned compiler warnings and
559        some "unreachable code" warnings.
561    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
562        things, this adds five new scripts.
564    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
565        There were also incompatibilities regarding the handling of \Q..\E inside
566        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
567        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
569    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
570        matches an empty string, and forcibly breaks the loop. There were bugs in
571        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
572        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
573        separate and independent bugs (that affected different cases) have been
574        fixed.
576    39. Refactored the code to abolish the use of different opcodes for small
577        capturing bracket numbers. This is a tidy that I avoided doing when I
578        removed the limit on the number of capturing brackets for 3.5 back in 2001.
579        The new approach is not only tidier, it makes it possible to reduce the
580        memory needed to fix the previous bug (38).
582    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
583        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
584        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
585        mode.
587    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
588        report.
590    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
591        copy construction and assignment in the C++ wrapper.
593    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
594        couple of bugs that could have given wrong results in the "--newline=crlf"
595        case.
597    44. Added a number of casts and did some reorganization of signed/unsigned int
598        variables following suggestions from Dair Grant. Also renamed the variable
599        "this" as "item" because it is a C++ keyword.
601    45. Arranged for dftables to add
603          #include "pcre_internal.h"
605        to pcre_chartables.c because without it, gcc 4.x may remove the array
606        definition from the final binary if PCRE is built into a static library and
607        dead code stripping is activated.
609    46. For an unanchored pattern, if a match attempt fails at the start of a
610        newline sequence, and the newline setting is CRLF or ANY, and the next two
611        characters are CRLF, advance by two characters instead of one.
614    Version 6.7 04-Jul-06
615    ---------------------
617     1. In order to handle tests when input lines are enormously long, pcretest has
618        been re-factored so that it automatically extends its buffers when
619        necessary. The code is crude, but this _is_ just a test program. The
620        default size has been increased from 32K to 50K.
622     2. The code in pcre_study() was using the value of the re argument before
623        testing it for NULL. (Of course, in any sensible call of the function, it
624        won't be NULL.)
626     3. The memmove() emulation function in pcre_internal.h, which is used on
627        systems that lack both memmove() and bcopy() - that is, hardly ever -
628        was missing a "static" storage class specifier.
630     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
631        containing an extended class (one that cannot be represented by a bitmap
632        because it contains high-valued characters or Unicode property items, e.g.
633        [\pZ]). Almost always one would set UTF-8 mode when processing such a
634        pattern, but PCRE should not loop if you do not (it no longer does).
635        [Detail: two cases were found: (a) a repeated subpattern containing an
636        extended class; (b) a recursive reference to a subpattern that followed a
637        previous extended class. It wasn't skipping over the extended class
638        correctly when UTF-8 mode was not set.]
640     5. A negated single-character class was not being recognized as fixed-length
641        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
642        compile error "lookbehind assertion is not fixed length".
644     6. The RunPerlTest auxiliary script was showing an unexpected difference
645        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
646        write a Perl script that can interpret lines of an input file either as
647        byte characters or as UTF-8, which is what "perltest" was being required to
648        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
649        can't do is switch easily at run time between having the "use utf8;" pragma
650        or not. In the end, I fudged it by using the RunPerlTest script to insert
651        "use utf8;" explicitly for the UTF-8 tests.
653     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
654        the end of the subject string, contrary to the documentation and to what
655        Perl does. This was true of both matching functions. Now it matches only at
656        the start of the subject and immediately after *internal* newlines.
658     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
659        a pointer to an int instead of a pointer to an unsigned long int. This
660        caused problems on 64-bit systems.
662     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
663        instance of the 'standard' template library not being so standard".
665    10. There was no check on the number of named subpatterns nor the maximum
666        length of a subpattern name. The product of these values is used to compute
667        the size of the memory block for a compiled pattern. By supplying a very
668        long subpattern name and a large number of named subpatterns, the size
669        computation could be caused to overflow. This is now prevented by limiting
670        the length of names to 32 characters, and the number of named subpatterns
671        to 10,000.
673    11. Subpatterns that are repeated with specific counts have to be replicated in
674        the compiled pattern. The size of memory for this was computed from the
675        length of the subpattern and the repeat count. The latter is limited to
676        65535, but there was no limit on the former, meaning that integer overflow
677        could in principle occur. The compiled length of a repeated subpattern is
678        now limited to 30,000 bytes in order to prevent this.
680    12. Added the optional facility to have named substrings with the same name.
682    13. Added the ability to use a named substring as a condition, using the
683        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
684        are numbers (not recommended). Forward references are permitted.
686    14. Added forward references in named backreferences (if you see what I mean).
688    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
689        pattern could run off the end of the subject. For example, the pattern
690        "(?s)(.{1,5})"8 did this with the subject "ab".
692    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
693        PCRE_CASELESS was set when matching characters that were quantified with ?
694        or *.
696    17. A character class other than a single negated character that had a minimum
697        but no maximum quantifier - for example [ab]{6,} - was not handled
698        correctly by pce_dfa_exec(). It would match only one character.
700    18. A valid (though odd) pattern that looked like a POSIX character
701        class but used an invalid character after [ (for example [[,abc,]]) caused
702        pcre_compile() to give the error "Failed: internal error: code overflow" or
703        in some cases to crash with a glibc free() error. This could even happen if
704        the pattern terminated after [[ but there just happened to be a sequence of
705        letters, a binary zero, and a closing ] in the memory that followed.
707    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
708        over the years. Originally (before any Unicode support), just the bottom 8
709        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
710        output from "man perlunicode" includes this:
712          The regular expression compiler produces polymorphic opcodes.  That
713          is, the pattern adapts to the data and automatically switches to
714          the Unicode character scheme when presented with Unicode data--or
715          instead uses a traditional byte scheme when presented with byte
716          data.
718        Sadly, a wide octal escape does not cause a switch, and in a string with
719        no other multibyte characters, these octal escapes are treated as before.
720        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
721        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
722        Unicode string.
724        I have not perpetrated such confusion in PCRE. Up till now, it took just
725        the bottom 8 bits, as in old Perl. I have now made octal escapes with
726        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
727        translate to the appropriate multibyte character.
729    29. Applied some refactoring to reduce the number of warnings from Microsoft
730        and Borland compilers. This has included removing the fudge introduced
731        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
732        a warning about an unused variable.
734    21. PCRE has not included VT (character 0x0b) in the set of whitespace
735        characters since release 4.0, because Perl (from release 5.004) does not.
736        [Or at least, is documented not to: some releases seem to be in conflict
737        with the documentation.] However, when a pattern was studied with
738        pcre_study() and all its branches started with \s, PCRE still included VT
739        as a possible starting character. Of course, this did no harm; it just
740        caused an unnecessary match attempt.
742    22. Removed a now-redundant internal flag bit that recorded the fact that case
743        dependency changed within the pattern. This was once needed for "required
744        byte" processing, but is no longer used. This recovers a now-scarce options
745        bit. Also moved the least significant internal flag bit to the most-
746        significant bit of the word, which was not previously used (hangover from
747        the days when it was an int rather than a uint) to free up another bit for
748        the future.
750    23. Added support for CRLF line endings as well as CR and LF. As well as the
751        default being selectable at build time, it can now be changed at runtime
752        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
753        specify that it is scanning data with non-default line endings.
755    24. Changed the definition of CXXLINK to make it agree with the definition of
756        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
758    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
759        recursions. This makes a big different to stack usage for some patterns.
761    26. If a subpattern containing a named recursion or subroutine reference such
762        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
763        the space required for the compiled pattern went wrong and gave too small a
764        value. Depending on the environment, this could lead to "Failed: internal
765        error: code overflow at offset 49" or "glibc detected double free or
766        corruption" errors.
768    27. Applied patches from Google (a) to support the new newline modes and (b) to
769        advance over multibyte UTF-8 characters in GlobalReplace.
771    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
772        difference for some implementation of PCRE in some Windows version.
774    29. Added some extra testing facilities to pcretest:
776        \q<number>   in a data line sets the "match limit" value
777        \Q<number>   in a data line sets the "match recursion limt" value
778        -S <number>  sets the stack size, where <number> is in megabytes
780        The -S option isn't available for Windows.
783    Version 6.6 06-Feb-06
784    ---------------------
786     1. Change 16(a) for 6.5 broke things, because PCRE_DATA_SCOPE was not defined
787        in pcreposix.h. I have copied the definition from pcre.h.
789     2. Change 25 for 6.5 broke compilation in a build directory out-of-tree
790        because pcre.h is no longer a built file.
792     3. Added Jeff Friedl's additional debugging patches to pcregrep. These are
793        not normally included in the compiled code.
796    Version 6.5 01-Feb-06
797    ---------------------
799     1. When using the partial match feature with pcre_dfa_exec(), it was not
800        anchoring the second and subsequent partial matches at the new starting
801        point. This could lead to incorrect results. For example, with the pattern
802        /1234/, partially matching against "123" and then "a4" gave a match.
804     2. Changes to pcregrep:
806        (a) All non-match returns from pcre_exec() were being treated as failures
807            to match the line. Now, unless the error is PCRE_ERROR_NOMATCH, an
808            error message is output. Some extra information is given for the
809            PCRE_ERROR_MATCHLIMIT and PCRE_ERROR_RECURSIONLIMIT errors, which are
810            probably the only errors that are likely to be caused by users (by
811            specifying a regex that has nested indefinite repeats, for instance).
812            If there are more than 20 of these errors, pcregrep is abandoned.
814        (b) A binary zero was treated as data while matching, but terminated the
815            output line if it was written out. This has been fixed: binary zeroes
816            are now no different to any other data bytes.
818        (c) Whichever of the LC_ALL or LC_CTYPE environment variables is set is
819            used to set a locale for matching. The --locale=xxxx long option has
820            been added (no short equivalent) to specify a locale explicitly on the
821            pcregrep command, overriding the environment variables.
823        (d) When -B was used with -n, some line numbers in the output were one less
824            than they should have been.
826        (e) Added the -o (--only-matching) option.
828        (f) If -A or -C was used with -c (count only), some lines of context were
829            accidentally printed for the final match.
831        (g) Added the -H (--with-filename) option.
833        (h) The combination of options -rh failed to suppress file names for files
834            that were found from directory arguments.
836        (i) Added the -D (--devices) and -d (--directories) options.
838        (j) Added the -F (--fixed-strings) option.
840        (k) Allow "-" to be used as a file name for -f as well as for a data file.
842        (l) Added the --colo(u)r option.
844        (m) Added Jeffrey Friedl's -S testing option, but within #ifdefs so that it
845            is not present by default.
847     3. A nasty bug was discovered in the handling of recursive patterns, that is,
848        items such as (?R) or (?1), when the recursion could match a number of
849        alternatives. If it matched one of the alternatives, but subsequently,
850        outside the recursion, there was a failure, the code tried to back up into
851        the recursion. However, because of the way PCRE is implemented, this is not
852        possible, and the result was an incorrect result from the match.
854        In order to prevent this happening, the specification of recursion has
855        been changed so that all such subpatterns are automatically treated as
856        atomic groups. Thus, for example, (?R) is treated as if it were (?>(?R)).
858     4. I had overlooked the fact that, in some locales, there are characters for
859        which isalpha() is true but neither isupper() nor islower() are true. In
860        the fr_FR locale, for instance, the \xAA and \xBA characters (ordmasculine
861        and ordfeminine) are like this. This affected the treatment of \w and \W
862        when they appeared in character classes, but not when they appeared outside
863        a character class. The bit map for "word" characters is now created
864        separately from the results of isalnum() instead of just taking it from the
865        upper, lower, and digit maps. (Plus the underscore character, of course.)
867     5. The above bug also affected the handling of POSIX character classes such as
868        [[:alpha:]] and [[:alnum:]]. These do not have their own bit maps in PCRE's
869        permanent tables. Instead, the bit maps for such a class were previously
870        created as the appropriate unions of the upper, lower, and digit bitmaps.
871        Now they are created by subtraction from the [[:word:]] class, which has
872        its own bitmap.
874     6. The [[:blank:]] character class matches horizontal, but not vertical space.
875        It is created by subtracting the vertical space characters (\x09, \x0a,
876        \x0b, \x0c) from the [[:space:]] bitmap. Previously, however, the
877        subtraction was done in the overall bitmap for a character class, meaning
878        that a class such as [\x0c[:blank:]] was incorrect because \x0c would not
879        be recognized. This bug has been fixed.
881     7. Patches from the folks at Google:
883          (a) pcrecpp.cc: "to handle a corner case that may or may not happen in
884          real life, but is still worth protecting against".
886          (b) pcrecpp.cc: "corrects a bug when negative radixes are used with
887          regular expressions".
889          (c) pcre_scanner.cc: avoid use of std::count() because not all systems
890          have it.
892          (d) Split off pcrecpparg.h from pcrecpp.h and had the former built by
893          "configure" and the latter not, in order to fix a problem somebody had
894          with compiling the Arg class on HP-UX.
896          (e) Improve the error-handling of the C++ wrapper a little bit.
898          (f) New tests for checking recursion limiting.
900     8. The pcre_memmove() function, which is used only if the environment does not
901        have a standard memmove() function (and is therefore rarely compiled),
902        contained two bugs: (a) use of int instead of size_t, and (b) it was not
903        returning a result (though PCRE never actually uses the result).
905     9. In the POSIX regexec() interface, if nmatch is specified as a ridiculously
906        large number - greater than INT_MAX/(3*sizeof(int)) - REG_ESPACE is
907        returned instead of calling malloc() with an overflowing number that would
908        most likely cause subsequent chaos.
910    10. The debugging option of pcretest was not showing the NO_AUTO_CAPTURE flag.
912    11. The POSIX flag REG_NOSUB is now supported. When a pattern that was compiled
913        with this option is matched, the nmatch and pmatch options of regexec() are
914        ignored.
916    12. Added REG_UTF8 to the POSIX interface. This is not defined by POSIX, but is
917        provided in case anyone wants to the the POSIX interface with UTF-8
918        strings.
920    13. Added CXXLDFLAGS to the Makefile parameters to provide settings only on the
921        C++ linking (needed for some HP-UX environments).
923    14. Avoid compiler warnings in get_ucpname() when compiled without UCP support
924        (unused parameter) and in the pcre_printint() function (omitted "default"
925        switch label when the default is to do nothing).
927    15. Added some code to make it possible, when PCRE is compiled as a C++
928        library, to replace subject pointers for pcre_exec() with a smart pointer
929        class, thus making it possible to process discontinuous strings.
931    16. The two macros PCRE_EXPORT and PCRE_DATA_SCOPE are confusing, and perform
932        much the same function. They were added by different people who were trying
933        to make PCRE easy to compile on non-Unix systems. It has been suggested
934        that PCRE_EXPORT be abolished now that there is more automatic apparatus
935        for compiling on Windows systems. I have therefore replaced it with
936        PCRE_DATA_SCOPE. This is set automatically for Windows; if not set it
937        defaults to "extern" for C or "extern C" for C++, which works fine on
938        Unix-like systems. It is now possible to override the value of PCRE_DATA_
939        SCOPE with something explicit in config.h. In addition:
941        (a) pcreposix.h still had just "extern" instead of either of these macros;
942            I have replaced it with PCRE_DATA_SCOPE.
944        (b) Functions such as _pcre_xclass(), which are internal to the library,
945            but external in the C sense, all had PCRE_EXPORT in their definitions.
946            This is apparently wrong for the Windows case, so I have removed it.
947            (It makes no difference on Unix-like systems.)
949    17. Added a new limit, MATCH_LIMIT_RECURSION, which limits the depth of nesting
950        of recursive calls to match(). This is different to MATCH_LIMIT because
951        that limits the total number of calls to match(), not all of which increase
952        the depth of recursion. Limiting the recursion depth limits the amount of
953        stack (or heap if NO_RECURSE is set) that is used. The default can be set
954        when PCRE is compiled, and changed at run time. A patch from Google adds
955        this functionality to the C++ interface.
957    18. Changes to the handling of Unicode character properties:
959        (a) Updated the table to Unicode 4.1.0.
961        (b) Recognize characters that are not in the table as "Cn" (undefined).
963        (c) I revised the way the table is implemented to a much improved format
964            which includes recognition of ranges. It now supports the ranges that
965            are defined in UnicodeData.txt, and it also amalgamates other
966            characters into ranges. This has reduced the number of entries in the
967            table from around 16,000 to around 3,000, thus reducing its size
968            considerably. I realized I did not need to use a tree structure after
969            all - a binary chop search is just as efficient. Having reduced the
970            number of entries, I extended their size from 6 bytes to 8 bytes to
971            allow for more data.
973        (d) Added support for Unicode script names via properties such as \p{Han}.
975    19. In UTF-8 mode, a backslash followed by a non-Ascii character was not
976        matching that character.
978    20. When matching a repeated Unicode property with a minimum greater than zero,
979        (for example \pL{2,}), PCRE could look past the end of the subject if it
980        reached it while seeking the minimum number of characters. This could
981        happen only if some of the characters were more than one byte long, because
982        there is a check for at least the minimum number of bytes.
984    21. Refactored the implementation of \p and \P so as to be more general, to
985        allow for more different types of property in future. This has changed the
986        compiled form incompatibly. Anybody with saved compiled patterns that use
987        \p or \P will have to recompile them.
989    22. Added "Any" and "L&" to the supported property types.
991    23. Recognize \x{...} as a code point specifier, even when not in UTF-8 mode,
992        but give a compile time error if the value is greater than 0xff.
994    24. The man pages for pcrepartial, pcreprecompile, and pcre_compile2 were
995        accidentally not being installed or uninstalled.
997    25. The pcre.h file was built from pcre.h.in, but the only changes that were
998        made were to insert the current release number. This seemed silly, because
999        it made things harder for people building PCRE on systems that don't run
1000        "configure". I have turned pcre.h into a distributed file, no longer built
1001        by "configure", with the version identification directly included. There is
1002        no longer a pcre.h.in file.
1004        However, this change necessitated a change to the pcre-config script as
1005        well. It is built from pcre-config.in, and one of the substitutions was the
1006        release number. I have updated configure.ac so that ./configure now finds
1007        the release number by grepping pcre.h.
1009    26. Added the ability to run the tests under valgrind.
1012    Version 6.4 05-Sep-05
1013    ---------------------
1015     1. Change 6.0/10/(l) to pcregrep introduced a bug that caused separator lines
1016        "--" to be printed when multiple files were scanned, even when none of the
1017        -A, -B, or -C options were used. This is not compatible with Gnu grep, so I
1018        consider it to be a bug, and have restored the previous behaviour.
1020     2. A couple of code tidies to get rid of compiler warnings.
1022     3. The pcretest program used to cheat by referring to symbols in the library
1023        whose names begin with _pcre_. These are internal symbols that are not
1024        really supposed to be visible externally, and in some environments it is
1025        possible to suppress them. The cheating is now confined to including
1026        certain files from the library's source, which is a bit cleaner.
1028     4. Renamed pcre.in as pcre.h.in to go with pcrecpp.h.in; it also makes the
1029        file's purpose clearer.
1031     5. Reorganized pcre_ucp_findchar().
1034  Version 6.3 15-Aug-05  Version 6.3 15-Aug-05
1035  ---------------------  ---------------------

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