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revision 91 by nigel, Sat Feb 24 21:41:34 2007 UTC revision 236 by ph10, Tue Sep 11 12:57:06 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4    Version 7.4 10-Sep-07
5    ---------------------
6    
7    1.  Change 7.3/28 was implemented for classes by looking at the bitmap. This
8        means that a class such as [\s] counted as "explicit reference to CR or
9        LF". That isn't really right - the whole point of the change was to try to
10        help when there was an actual mention of one of the two characters. So now
11        the change happens only if \r or \n (or a literal CR or LF) character is
12        encountered.
13    
14    2.  The 32-bit options word was also used for 6 internal flags, but the numbers
15        of both had grown to the point where there were only 3 bits left.
16        Fortunately, there was spare space in the data structure, and so I have
17        moved the internal flags into a new 16-bit field to free up more option
18        bits.
19    
20    3.  The appearance of (?J) at the start of a pattern set the DUPNAMES option,
21        but did not set the internal JCHANGED flag - either of these is enough to
22        control the way the "get" function works - but the PCRE_INFO_JCHANGED
23        facility is supposed to tell if (?J) was ever used, so now (?J) at the
24        start sets both bits.
25    
26    4.  Added options (at build time, compile time, exec time) to change \R from
27        matching any Unicode line ending sequence to just matching CR, LF, or CRLF.
28    
29    5.  doc/pcresyntax.html was missing from the distribution.
30    
31    6.  Put back the definition of PCRE_ERROR_NULLWSLIMIT, for backward
32        compatibility, even though it is no longer used.
33    
34    7.  Added macro for snprintf to pcrecpp_unittest.cc and also for strtoll and
35        strtoull to pcrecpp.cc to select the available functions in WIN32 (where
36        different names are used).
37    
38    8.  Changed all #include <config.h> to #include "config.h". There were also
39        some further <pcre.h> cases that I changed to "pcre.h".
40    
41    
42    Version 7.3 28-Aug-07
43    ---------------------
44    
45     1. In the rejigging of the build system that eventually resulted in 7.1, the
46        line "#include <pcre.h>" was included in pcre_internal.h. The use of angle
47        brackets there is not right, since it causes compilers to look for an
48        installed pcre.h, not the version that is in the source that is being
49        compiled (which of course may be different). I have changed it back to:
50    
51          #include "pcre.h"
52    
53        I have a vague recollection that the change was concerned with compiling in
54        different directories, but in the new build system, that is taken care of
55        by the VPATH setting the Makefile.
56    
57     2. The pattern .*$ when run in not-DOTALL UTF-8 mode with newline=any failed
58        when the subject happened to end in the byte 0x85 (e.g. if the last
59        character was \x{1ec5}). *Character* 0x85 is one of the "any" newline
60        characters but of course it shouldn't be taken as a newline when it is part
61        of another character. The bug was that, for an unlimited repeat of . in
62        not-DOTALL UTF-8 mode, PCRE was advancing by bytes rather than by
63        characters when looking for a newline.
64    
65     3. A small performance improvement in the DOTALL UTF-8 mode .* case.
66    
67     4. Debugging: adjusted the names of opcodes for different kinds of parentheses
68        in debug output.
69    
70     5. Arrange to use "%I64d" instead of "%lld" and "%I64u" instead of "%llu" for
71        long printing in the pcrecpp unittest when running under MinGW.
72    
73     6. ESC_K was left out of the EBCDIC table.
74    
75     7. Change 7.0/38 introduced a new limit on the number of nested non-capturing
76        parentheses; I made it 1000, which seemed large enough. Unfortunately, the
77        limit also applies to "virtual nesting" when a pattern is recursive, and in
78        this case 1000 isn't so big. I have been able to remove this limit at the
79        expense of backing off one optimization in certain circumstances. Normally,
80        when pcre_exec() would call its internal match() function recursively and
81        immediately return the result unconditionally, it uses a "tail recursion"
82        feature to save stack. However, when a subpattern that can match an empty
83        string has an unlimited repetition quantifier, it no longer makes this
84        optimization. That gives it a stack frame in which to save the data for
85        checking that an empty string has been matched. Previously this was taken
86        from the 1000-entry workspace that had been reserved. So now there is no
87        explicit limit, but more stack is used.
88    
89     8. Applied Daniel's patches to solve problems with the import/export magic
90        syntax that is required for Windows, and which was going wrong for the
91        pcreposix and pcrecpp parts of the library. These were overlooked when this
92        problem was solved for the main library.
93    
94     9. There were some crude static tests to avoid integer overflow when computing
95        the size of patterns that contain repeated groups with explicit upper
96        limits. As the maximum quantifier is 65535, the maximum group length was
97        set at 30,000 so that the product of these two numbers did not overflow a
98        32-bit integer. However, it turns out that people want to use groups that
99        are longer than 30,000 bytes (though not repeat them that many times).
100        Change 7.0/17 (the refactoring of the way the pattern size is computed) has
101        made it possible to implement the integer overflow checks in a much more
102        dynamic way, which I have now done. The artificial limitation on group
103        length has been removed - we now have only the limit on the total length of
104        the compiled pattern, which depends on the LINK_SIZE setting.
105    
106    10. Fixed a bug in the documentation for get/copy named substring when
107        duplicate names are permitted. If none of the named substrings are set, the
108        functions return PCRE_ERROR_NOSUBSTRING (7); the doc said they returned an
109        empty string.
110    
111    11. Because Perl interprets \Q...\E at a high level, and ignores orphan \E
112        instances, patterns such as [\Q\E] or [\E] or even [^\E] cause an error,
113        because the ] is interpreted as the first data character and the
114        terminating ] is not found. PCRE has been made compatible with Perl in this
115        regard. Previously, it interpreted [\Q\E] as an empty class, and [\E] could
116        cause memory overwriting.
117    
118    10. Like Perl, PCRE automatically breaks an unlimited repeat after an empty
119        string has been matched (to stop an infinite loop). It was not recognizing
120        a conditional subpattern that could match an empty string if that
121        subpattern was within another subpattern. For example, it looped when
122        trying to match  (((?(1)X|))*)  but it was OK with  ((?(1)X|)*)  where the
123        condition was not nested. This bug has been fixed.
124    
125    12. A pattern like \X?\d or \P{L}?\d in non-UTF-8 mode could cause a backtrack
126        past the start of the subject in the presence of bytes with the top bit
127        set, for example "\x8aBCD".
128    
129    13. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
130        (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
131    
132    14. Optimized (?!) to (*FAIL).
133    
134    15. Updated the test for a valid UTF-8 string to conform to the later RFC 3629.
135        This restricts code points to be within the range 0 to 0x10FFFF, excluding
136        the "low surrogate" sequence 0xD800 to 0xDFFF. Previously, PCRE allowed the
137        full range 0 to 0x7FFFFFFF, as defined by RFC 2279. Internally, it still
138        does: it's just the validity check that is more restrictive.
139    
140    16. Inserted checks for integer overflows during escape sequence (backslash)
141        processing, and also fixed erroneous offset values for syntax errors during
142        backslash processing.
143    
144    17. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
145        for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
146    
147    18. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
148        caused an overrun.
149    
150    19. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
151        something other than just ASCII characters) inside a group that had an
152        unlimited repeat caused a loop at compile time (while checking to see
153        whether the group could match an empty string).
154    
155    20. Debugging a pattern containing \p or \P could cause a crash. For example,
156        [\P{Any}] did so. (Error in the code for printing property names.)
157    
158    21. An orphan \E inside a character class could cause a crash.
159    
160    22. A repeated capturing bracket such as (A)? could cause a wild memory
161        reference during compilation.
162    
163    23. There are several functions in pcre_compile() that scan along a compiled
164        expression for various reasons (e.g. to see if it's fixed length for look
165        behind). There were bugs in these functions when a repeated \p or \P was
166        present in the pattern. These operators have additional parameters compared
167        with \d, etc, and these were not being taken into account when moving along
168        the compiled data. Specifically:
169    
170        (a) A item such as \p{Yi}{3} in a lookbehind was not treated as fixed
171            length.
172    
173        (b) An item such as \pL+ within a repeated group could cause crashes or
174            loops.
175    
176        (c) A pattern such as \p{Yi}+(\P{Yi}+)(?1) could give an incorrect
177            "reference to non-existent subpattern" error.
178    
179        (d) A pattern like (\P{Yi}{2}\277)? could loop at compile time.
180    
181    24. A repeated \S or \W in UTF-8 mode could give wrong answers when multibyte
182        characters were involved (for example /\S{2}/8g with "A\x{a3}BC").
183    
184    25. Using pcregrep in multiline, inverted mode (-Mv) caused it to loop.
185    
186    26. Patterns such as [\P{Yi}A] which include \p or \P and just one other
187        character were causing crashes (broken optimization).
188    
189    27. Patterns such as (\P{Yi}*\277)* (group with possible zero repeat containing
190        \p or \P) caused a compile-time loop.
191    
192    28. More problems have arisen in unanchored patterns when CRLF is a valid line
193        break. For example, the unstudied pattern [\r\n]A does not match the string
194        "\r\nA" because change 7.0/46 below moves the current point on by two
195        characters after failing to match at the start. However, the pattern \nA
196        *does* match, because it doesn't start till \n, and if [\r\n]A is studied,
197        the same is true. There doesn't seem any very clean way out of this, but
198        what I have chosen to do makes the common cases work: PCRE now takes note
199        of whether there can be an explicit match for \r or \n anywhere in the
200        pattern, and if so, 7.0/46 no longer applies. As part of this change,
201        there's a new PCRE_INFO_HASCRORLF option for finding out whether a compiled
202        pattern has explicit CR or LF references.
203    
204    29. Added (*CR) etc for changing newline setting at start of pattern.
205    
206    
207    Version 7.2 19-Jun-07
208    ---------------------
209    
210     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
211        which is apparently normally available under Windows.
212    
213     2. Re-jig the pcregrep tests with different newline settings in an attempt
214        to make them independent of the local environment's newline setting.
215    
216     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
217    
218     4. Some of the "internals" tests were previously cut out when the link size
219        was not 2, because the output contained actual offsets. The recent new
220        "Z" feature of pcretest means that these can be cut out, making the tests
221        usable with all link sizes.
222    
223     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
224        stack recursion. This gives a massive performance boost under BSD, but just
225        a small improvement under Linux. However, it saves one field in the frame
226        in all cases.
227    
228     6. Added more features from the forthcoming Perl 5.10:
229    
230        (a) (?-n) (where n is a string of digits) is a relative subroutine or
231            recursion call. It refers to the nth most recently opened parentheses.
232    
233        (b) (?+n) is also a relative subroutine call; it refers to the nth next
234            to be opened parentheses.
235    
236        (c) Conditions that refer to capturing parentheses can be specified
237            relatively, for example, (?(-2)... or (?(+3)...
238    
239        (d) \K resets the start of the current match so that everything before
240            is not part of it.
241    
242        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
243    
244        (f) \g{name} is another synonym - part of Perl 5.10's unification of
245            reference syntax.
246    
247        (g) (?| introduces a group in which the numbering of parentheses in each
248            alternative starts with the same number.
249    
250        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
251    
252     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
253        PCRE_INFO_JCHANGED.
254    
255     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
256        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
257        for detecting groups that can match an empty string.
258    
259     9. A pattern with a very large number of alternatives (more than several
260        hundred) was running out of internal workspace during the pre-compile
261        phase, where pcre_compile() figures out how much memory will be needed. A
262        bit of new cunning has reduced the workspace needed for groups with
263        alternatives. The 1000-alternative test pattern now uses 12 bytes of
264        workspace instead of running out of the 4096 that are available.
265    
266    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
267    
268    11. Applied patch from Google to remove an optimization that didn't quite work.
269        The report of the bug said:
270    
271          pcrecpp::RE("a*").FullMatch("aaa") matches, while
272          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
273          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
274    
275    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
276        it matched the wrong number of bytes.
277    
278    
279    Version 7.1 24-Apr-07
280    ---------------------
281    
282     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
283        that is more "standard", making use of automake and other Autotools. There
284        is some re-arrangement of the files and adjustment of comments consequent
285        on this.
286    
287     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
288        for recursive directory scanning broke on some systems because the files
289        are not scanned in any specific order and on different systems the order
290        was different. A call to "sort" has been inserted into RunGrepTest for the
291        approprate test as a short-term fix. In the longer term there may be an
292        alternative.
293    
294     3. I had an email from Eric Raymond about problems translating some of PCRE's
295        man pages to HTML (despite the fact that I distribute HTML pages, some
296        people do their own conversions for various reasons). The problems
297        concerned the use of low-level troff macros .br and .in. I have therefore
298        removed all such uses from the man pages (some were redundant, some could
299        be replaced by .nf/.fi pairs). The 132html script that I use to generate
300        HTML has been updated to handle .nf/.fi and to complain if it encounters
301        .br or .in.
302    
303     4. Updated comments in configure.ac that get placed in config.h.in and also
304        arranged for config.h to be included in the distribution, with the name
305        config.h.generic, for the benefit of those who have to compile without
306        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
307    
308     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
309        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
310        makevp.bat for the current PCRE, using the additional files
311        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
312    
313     6. A Windows user reported a minor discrepancy with test 2, which turned out
314        to be caused by a trailing space on an input line that had got lost in his
315        copy. The trailing space was an accident, so I've just removed it.
316    
317     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
318        that is needed.
319    
320     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
321        as "const" (a) because they are and (b) because it helps the PHP
322        maintainers who have recently made a script to detect big data structures
323        in the php code that should be moved to the .rodata section. I remembered
324        to update Builducptable as well, so it won't revert if ucptable.h is ever
325        re-created.
326    
327     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
328        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
329        order to be able to cut out the UTF-8 tables in the latter when UTF-8
330        support is not required. This saves 1.5-2K of code, which is important in
331        some applications.
332    
333        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
334        so as not to refer to the tables, even though these functions will never be
335        called when UTF-8 support is disabled. Otherwise there are problems with a
336        shared library.
337    
338    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
339    
340        (a) It was defining its arguments as char * instead of void *.
341    
342        (b) It was assuming that all moves were upwards in memory; this was true
343            a long time ago when I wrote it, but is no longer the case.
344    
345        The emulated memove() is provided for those environments that have neither
346        memmove() nor bcopy(). I didn't think anyone used it these days, but that
347        is clearly not the case, as these two bugs were recently reported.
348    
349    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
350        and Detrail to create the HTML documentation, the .txt form of the man
351        pages, and it removes trailing spaces from listed files. It also creates
352        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
353        case, it wraps all the #defines with #ifndefs. This script should be run
354        before "make dist".
355    
356    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
357        with Unicode property support.
358    
359        (a) For a maximizing quantifier, if the two different cases of the
360            character were of different lengths in their UTF-8 codings (there are
361            some cases like this - I found 11), and the matching function had to
362            back up over a mixture of the two cases, it incorrectly assumed they
363            were both the same length.
364    
365        (b) When PCRE was configured to use the heap rather than the stack for
366            recursion during matching, it was not correctly preserving the data for
367            the other case of a UTF-8 character when checking ahead for a match
368            while processing a minimizing repeat. If the check also involved
369            matching a wide character, but failed, corruption could cause an
370            erroneous result when trying to check for a repeat of the original
371            character.
372    
373    13. Some tidying changes to the testing mechanism:
374    
375        (a) The RunTest script now detects the internal link size and whether there
376            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
377            values substituted by "configure". (The RunGrepTest script already did
378            this for UTF-8.) The configure.ac script no longer substitutes the
379            relevant variables.
380    
381        (b) The debugging options /B and /D in pcretest show the compiled bytecode
382            with length and offset values. This means that the output is different
383            for different internal link sizes. Test 2 is skipped for link sizes
384            other than 2 because of this, bypassing the problem. Unfortunately,
385            there was also a test in test 3 (the locale tests) that used /B and
386            failed for link sizes other than 2. Rather than cut the whole test out,
387            I have added a new /Z option to pcretest that replaces the length and
388            offset values with spaces. This is now used to make test 3 independent
389            of link size. (Test 2 will be tidied up later.)
390    
391    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
392        segmentation fault instead of returning the appropriate error message.
393    
394    15. In multiline mode when the newline sequence was set to "any", the pattern
395        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
396        This doesn't seem right; it now treats the CRLF combination as the line
397        ending, and so does not match in that case. It's only a pattern such as ^$
398        that would hit this one: something like ^ABC$ would have failed after \r
399        and then tried again after \r\n.
400    
401    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
402        in an attempt to make files that differ only in their line terminators
403        compare equal. This works on Linux.
404    
405    17. Under certain error circumstances pcregrep might try to free random memory
406        as it exited. This is now fixed, thanks to valgrind.
407    
408    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
409        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
410        was because its rules for how to advance for /g after matching an empty
411        string at the end of a line did not allow for this case. They now check for
412        it specially.
413    
414    20. pcretest is supposed to handle patterns and data of any length, by
415        extending its buffers when necessary. It was getting this wrong when the
416        buffer for a data line had to be extended.
417    
418    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
419        CRLF as a newline sequence.
420    
421    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
422        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
423        I have nevertheless tidied it up.
424    
425    23. Added some casts to kill warnings from HP-UX ia64 compiler.
426    
427    24. Added a man page for pcre-config.
428    
429    
430    Version 7.0 19-Dec-06
431    ---------------------
432    
433     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
434        moving to gcc 4.1.1.
435    
436     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
437        sys/time.h, which is documented as needed for this function. It doesn't
438        seem to matter on Linux, but it showed up on some releases of OS X.
439    
440     3. It seems that there are systems where bytes whose values are greater than
441        127 match isprint() in the "C" locale. The "C" locale should be the
442        default when a C program starts up. In most systems, only ASCII printing
443        characters match isprint(). This difference caused the output from pcretest
444        to vary, making some of the tests fail. I have changed pcretest so that:
445    
446        (a) When it is outputting text in the compiled version of a pattern, bytes
447            other than 32-126 are always shown as hex escapes.
448    
449        (b) When it is outputting text that is a matched part of a subject string,
450            it does the same, unless a different locale has been set for the match
451            (using the /L modifier). In this case, it uses isprint() to decide.
452    
453     4. Fixed a major bug that caused incorrect computation of the amount of memory
454        required for a compiled pattern when options that changed within the
455        pattern affected the logic of the preliminary scan that determines the
456        length. The relevant options are -x, and -i in UTF-8 mode. The result was
457        that the computed length was too small. The symptoms of this bug were
458        either the PCRE error "internal error: code overflow" from pcre_compile(),
459        or a glibc crash with a message such as "pcretest: free(): invalid next
460        size (fast)". Examples of patterns that provoked this bug (shown in
461        pcretest format) are:
462    
463          /(?-x: )/x
464          /(?x)(?-x: \s*#\s*)/
465          /((?i)[\x{c0}])/8
466          /(?i:[\x{c0}])/8
467    
468        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
469        is now done differently.
470    
471     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
472        wrapper classes; (b) implement a new function in the C++ scanner that is
473        more efficient than the old way of doing things because it avoids levels of
474        recursion in the regex matching; (c) add a paragraph to the documentation
475        for the FullMatch() function.
476    
477     6. The escape sequence \n was being treated as whatever was defined as
478        "newline". Not only was this contrary to the documentation, which states
479        that \n is character 10 (hex 0A), but it also went horribly wrong when
480        "newline" was defined as CRLF. This has been fixed.
481    
482     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
483        was being set to -1 for the "end of line" case (supposedly a value that no
484        character can have). Though this value is never used (the check for end of
485        line is "zero bytes in current character"), it caused compiler complaints.
486        I've changed it to 0xffffffff.
487    
488     8. In pcre_version.c, the version string was being built by a sequence of
489        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
490        string (as it is for production releases) called a macro with an empty
491        argument. The C standard says the result of this is undefined. The gcc
492        compiler treats it as an empty string (which was what was wanted) but it is
493        reported that Visual C gives an error. The source has been hacked around to
494        avoid this problem.
495    
496     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
497        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
498        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
499        of them did).
500    
501    10. Originally, pcretest opened its input and output without "b"; then I was
502        told that "b" was needed in some environments, so it was added for release
503        5.0 to both the input and output. (It makes no difference on Unix-like
504        systems.) Later I was told that it is wrong for the input on Windows. I've
505        now abstracted the modes into two macros, to make it easier to fiddle with
506        them, and removed "b" from the input mode under Windows.
507    
508    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
509    
510    12. Added -help and --help to pcretest as an official way of being reminded
511        of the options.
512    
513    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
514        and pcrecpp.cc because they annoy compilers at high warning levels.
515    
516    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
517    
518    15. Fixed an occurrence of == in configure.ac that should have been = (shell
519        scripts are not C programs :-) and which was not noticed because it works
520        on Linux.
521    
522    16. pcretest is supposed to handle any length of pattern and data line (as one
523        line or as a continued sequence of lines) by extending its input buffer if
524        necessary. This feature was broken for very long pattern lines, leading to
525        a string of junk being passed to pcre_compile() if the pattern was longer
526        than about 50K.
527    
528    17. I have done a major re-factoring of the way pcre_compile() computes the
529        amount of memory needed for a compiled pattern. Previously, there was code
530        that made a preliminary scan of the pattern in order to do this. That was
531        OK when PCRE was new, but as the facilities have expanded, it has become
532        harder and harder to keep it in step with the real compile phase, and there
533        have been a number of bugs (see for example, 4 above). I have now found a
534        cunning way of running the real compile function in a "fake" mode that
535        enables it to compute how much memory it would need, while actually only
536        ever using a few hundred bytes of working memory and without too many
537        tests of the mode. This should make future maintenance and development
538        easier. A side effect of this work is that the limit of 200 on the nesting
539        depth of parentheses has been removed (though this was never a serious
540        limitation, I suspect). However, there is a downside: pcre_compile() now
541        runs more slowly than before (30% or more, depending on the pattern). I
542        hope this isn't a big issue. There is no effect on runtime performance.
543    
544    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
545        newline (only possible for the last line of a file) and it was a
546        pattern that set a locale (followed by /Lsomething), pcretest crashed.
547    
548    19. Added additional timing features to pcretest. (1) The -tm option now times
549        matching only, not compiling. (2) Both -t and -tm can be followed, as a
550        separate command line item, by a number that specifies the number of
551        repeats to use when timing. The default is 50000; this gives better
552        precision, but takes uncomfortably long for very large patterns.
553    
554    20. Extended pcre_study() to be more clever in cases where a branch of a
555        subpattern has no definite first character. For example, (a*|b*)[cd] would
556        previously give no result from pcre_study(). Now it recognizes that the
557        first character must be a, b, c, or d.
558    
559    21. There was an incorrect error "recursive call could loop indefinitely" if
560        a subpattern (or the entire pattern) that was being tested for matching an
561        empty string contained only one non-empty item after a nested subpattern.
562        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
563        incorrectly, because the \d was being skipped in the check.
564    
565    22. The pcretest program now has a new pattern option /B and a command line
566        option -b, which is equivalent to adding /B to every pattern. This causes
567        it to show the compiled bytecode, without the additional information that
568        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
569        is the same as /B/I).
570    
571    23. A new optimization is now able automatically to treat some sequences such
572        as a*b as a*+b. More specifically, if something simple (such as a character
573        or a simple class like \d) has an unlimited quantifier, and is followed by
574        something that cannot possibly match the quantified thing, the quantifier
575        is automatically "possessified".
576    
577    24. A recursive reference to a subpattern whose number was greater than 39
578        went wrong under certain circumstances in UTF-8 mode. This bug could also
579        have affected the operation of pcre_study().
580    
581    25. Realized that a little bit of performance could be had by replacing
582        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
583    
584    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
585    
586    27. Possessive quantifiers such as a++ were previously implemented by turning
587        them into atomic groups such as ($>a+). Now they have their own opcodes,
588        which improves performance. This includes the automatically created ones
589        from 23 above.
590    
591    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
592        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
593        the first matched character to be a colon. This applied both to named and
594        numbered groups.
595    
596    29. The ucpinternal.h header file was missing its idempotency #ifdef.
597    
598    30. I was sent a "project" file called libpcre.a.dev which I understand makes
599        building PCRE on Windows easier, so I have included it in the distribution.
600    
601    31. There is now a check in pcretest against a ridiculously large number being
602        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
603        loop, the loop is abandoned.
604    
605    32. Forward references to subpatterns in conditions such as (?(2)...) where
606        subpattern 2 is defined later cause pcre_compile() to search forwards in
607        the pattern for the relevant set of parentheses. This search went wrong
608        when there were unescaped parentheses in a character class, parentheses
609        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
610    
611    33. "Subroutine" calls and backreferences were previously restricted to
612        referencing subpatterns earlier in the regex. This restriction has now
613        been removed.
614    
615    34. Added a number of extra features that are going to be in Perl 5.10. On the
616        whole, these are just syntactic alternatives for features that PCRE had
617        previously implemented using the Python syntax or my own invention. The
618        other formats are all retained for compatibility.
619    
620        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
621            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
622            also .NET compatible.
623    
624        (b) A recursion or subroutine call to a named group can now be defined as
625            (?&name) as well as (?P>name).
626    
627        (c) A backreference to a named group can now be defined as \k<name> or
628            \k'name' as well as (?P=name). The new forms, as well as being in Perl
629            5.10, are also .NET compatible.
630    
631        (d) A conditional reference to a named group can now use the syntax
632            (?(<name>) or (?('name') as well as (?(name).
633    
634        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
635            groups (named and numbered) that are never evaluated inline, but can be
636            called as "subroutines" from elsewhere. In effect, the DEFINE condition
637            is always false. There may be only one alternative in such a group.
638    
639        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
640            as the simple (?(R). The condition is true only if the most recent
641            recursion is that of the given number or name. It does not search out
642            through the entire recursion stack.
643    
644        (g) The escape \gN or \g{N} has been added, where N is a positive or
645            negative number, specifying an absolute or relative reference.
646    
647    35. Tidied to get rid of some further signed/unsigned compiler warnings and
648        some "unreachable code" warnings.
649    
650    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
651        things, this adds five new scripts.
652    
653    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
654        There were also incompatibilities regarding the handling of \Q..\E inside
655        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
656        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
657    
658    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
659        matches an empty string, and forcibly breaks the loop. There were bugs in
660        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
661        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
662        separate and independent bugs (that affected different cases) have been
663        fixed.
664    
665    39. Refactored the code to abolish the use of different opcodes for small
666        capturing bracket numbers. This is a tidy that I avoided doing when I
667        removed the limit on the number of capturing brackets for 3.5 back in 2001.
668        The new approach is not only tidier, it makes it possible to reduce the
669        memory needed to fix the previous bug (38).
670    
671    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
672        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
673        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
674        mode.
675    
676    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
677        report.
678    
679    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
680        copy construction and assignment in the C++ wrapper.
681    
682    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
683        couple of bugs that could have given wrong results in the "--newline=crlf"
684        case.
685    
686    44. Added a number of casts and did some reorganization of signed/unsigned int
687        variables following suggestions from Dair Grant. Also renamed the variable
688        "this" as "item" because it is a C++ keyword.
689    
690    45. Arranged for dftables to add
691    
692          #include "pcre_internal.h"
693    
694        to pcre_chartables.c because without it, gcc 4.x may remove the array
695        definition from the final binary if PCRE is built into a static library and
696        dead code stripping is activated.
697    
698    46. For an unanchored pattern, if a match attempt fails at the start of a
699        newline sequence, and the newline setting is CRLF or ANY, and the next two
700        characters are CRLF, advance by two characters instead of one.
701    
702    
703  Version 6.7 04-Jul-06  Version 6.7 04-Jul-06
704  ---------------------  ---------------------
705    

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