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revision 91 by nigel, Sat Feb 24 21:41:34 2007 UTC revision 239 by ph10, Tue Sep 11 13:46:30 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    9.  When pcregrep was used with the --colour option, it missed the line ending
42        sequence off the lines that it output.
43    
44    
45    Version 7.3 28-Aug-07
46    ---------------------
47    
48     1. In the rejigging of the build system that eventually resulted in 7.1, the
49        line "#include <pcre.h>" was included in pcre_internal.h. The use of angle
50        brackets there is not right, since it causes compilers to look for an
51        installed pcre.h, not the version that is in the source that is being
52        compiled (which of course may be different). I have changed it back to:
53    
54          #include "pcre.h"
55    
56        I have a vague recollection that the change was concerned with compiling in
57        different directories, but in the new build system, that is taken care of
58        by the VPATH setting the Makefile.
59    
60     2. The pattern .*$ when run in not-DOTALL UTF-8 mode with newline=any failed
61        when the subject happened to end in the byte 0x85 (e.g. if the last
62        character was \x{1ec5}). *Character* 0x85 is one of the "any" newline
63        characters but of course it shouldn't be taken as a newline when it is part
64        of another character. The bug was that, for an unlimited repeat of . in
65        not-DOTALL UTF-8 mode, PCRE was advancing by bytes rather than by
66        characters when looking for a newline.
67    
68     3. A small performance improvement in the DOTALL UTF-8 mode .* case.
69    
70     4. Debugging: adjusted the names of opcodes for different kinds of parentheses
71        in debug output.
72    
73     5. Arrange to use "%I64d" instead of "%lld" and "%I64u" instead of "%llu" for
74        long printing in the pcrecpp unittest when running under MinGW.
75    
76     6. ESC_K was left out of the EBCDIC table.
77    
78     7. Change 7.0/38 introduced a new limit on the number of nested non-capturing
79        parentheses; I made it 1000, which seemed large enough. Unfortunately, the
80        limit also applies to "virtual nesting" when a pattern is recursive, and in
81        this case 1000 isn't so big. I have been able to remove this limit at the
82        expense of backing off one optimization in certain circumstances. Normally,
83        when pcre_exec() would call its internal match() function recursively and
84        immediately return the result unconditionally, it uses a "tail recursion"
85        feature to save stack. However, when a subpattern that can match an empty
86        string has an unlimited repetition quantifier, it no longer makes this
87        optimization. That gives it a stack frame in which to save the data for
88        checking that an empty string has been matched. Previously this was taken
89        from the 1000-entry workspace that had been reserved. So now there is no
90        explicit limit, but more stack is used.
91    
92     8. Applied Daniel's patches to solve problems with the import/export magic
93        syntax that is required for Windows, and which was going wrong for the
94        pcreposix and pcrecpp parts of the library. These were overlooked when this
95        problem was solved for the main library.
96    
97     9. There were some crude static tests to avoid integer overflow when computing
98        the size of patterns that contain repeated groups with explicit upper
99        limits. As the maximum quantifier is 65535, the maximum group length was
100        set at 30,000 so that the product of these two numbers did not overflow a
101        32-bit integer. However, it turns out that people want to use groups that
102        are longer than 30,000 bytes (though not repeat them that many times).
103        Change 7.0/17 (the refactoring of the way the pattern size is computed) has
104        made it possible to implement the integer overflow checks in a much more
105        dynamic way, which I have now done. The artificial limitation on group
106        length has been removed - we now have only the limit on the total length of
107        the compiled pattern, which depends on the LINK_SIZE setting.
108    
109    10. Fixed a bug in the documentation for get/copy named substring when
110        duplicate names are permitted. If none of the named substrings are set, the
111        functions return PCRE_ERROR_NOSUBSTRING (7); the doc said they returned an
112        empty string.
113    
114    11. Because Perl interprets \Q...\E at a high level, and ignores orphan \E
115        instances, patterns such as [\Q\E] or [\E] or even [^\E] cause an error,
116        because the ] is interpreted as the first data character and the
117        terminating ] is not found. PCRE has been made compatible with Perl in this
118        regard. Previously, it interpreted [\Q\E] as an empty class, and [\E] could
119        cause memory overwriting.
120    
121    10. Like Perl, PCRE automatically breaks an unlimited repeat after an empty
122        string has been matched (to stop an infinite loop). It was not recognizing
123        a conditional subpattern that could match an empty string if that
124        subpattern was within another subpattern. For example, it looped when
125        trying to match  (((?(1)X|))*)  but it was OK with  ((?(1)X|)*)  where the
126        condition was not nested. This bug has been fixed.
127    
128    12. A pattern like \X?\d or \P{L}?\d in non-UTF-8 mode could cause a backtrack
129        past the start of the subject in the presence of bytes with the top bit
130        set, for example "\x8aBCD".
131    
132    13. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
133        (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
134    
135    14. Optimized (?!) to (*FAIL).
136    
137    15. Updated the test for a valid UTF-8 string to conform to the later RFC 3629.
138        This restricts code points to be within the range 0 to 0x10FFFF, excluding
139        the "low surrogate" sequence 0xD800 to 0xDFFF. Previously, PCRE allowed the
140        full range 0 to 0x7FFFFFFF, as defined by RFC 2279. Internally, it still
141        does: it's just the validity check that is more restrictive.
142    
143    16. Inserted checks for integer overflows during escape sequence (backslash)
144        processing, and also fixed erroneous offset values for syntax errors during
145        backslash processing.
146    
147    17. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
148        for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
149    
150    18. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
151        caused an overrun.
152    
153    19. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
154        something other than just ASCII characters) inside a group that had an
155        unlimited repeat caused a loop at compile time (while checking to see
156        whether the group could match an empty string).
157    
158    20. Debugging a pattern containing \p or \P could cause a crash. For example,
159        [\P{Any}] did so. (Error in the code for printing property names.)
160    
161    21. An orphan \E inside a character class could cause a crash.
162    
163    22. A repeated capturing bracket such as (A)? could cause a wild memory
164        reference during compilation.
165    
166    23. There are several functions in pcre_compile() that scan along a compiled
167        expression for various reasons (e.g. to see if it's fixed length for look
168        behind). There were bugs in these functions when a repeated \p or \P was
169        present in the pattern. These operators have additional parameters compared
170        with \d, etc, and these were not being taken into account when moving along
171        the compiled data. Specifically:
172    
173        (a) A item such as \p{Yi}{3} in a lookbehind was not treated as fixed
174            length.
175    
176        (b) An item such as \pL+ within a repeated group could cause crashes or
177            loops.
178    
179        (c) A pattern such as \p{Yi}+(\P{Yi}+)(?1) could give an incorrect
180            "reference to non-existent subpattern" error.
181    
182        (d) A pattern like (\P{Yi}{2}\277)? could loop at compile time.
183    
184    24. A repeated \S or \W in UTF-8 mode could give wrong answers when multibyte
185        characters were involved (for example /\S{2}/8g with "A\x{a3}BC").
186    
187    25. Using pcregrep in multiline, inverted mode (-Mv) caused it to loop.
188    
189    26. Patterns such as [\P{Yi}A] which include \p or \P and just one other
190        character were causing crashes (broken optimization).
191    
192    27. Patterns such as (\P{Yi}*\277)* (group with possible zero repeat containing
193        \p or \P) caused a compile-time loop.
194    
195    28. More problems have arisen in unanchored patterns when CRLF is a valid line
196        break. For example, the unstudied pattern [\r\n]A does not match the string
197        "\r\nA" because change 7.0/46 below moves the current point on by two
198        characters after failing to match at the start. However, the pattern \nA
199        *does* match, because it doesn't start till \n, and if [\r\n]A is studied,
200        the same is true. There doesn't seem any very clean way out of this, but
201        what I have chosen to do makes the common cases work: PCRE now takes note
202        of whether there can be an explicit match for \r or \n anywhere in the
203        pattern, and if so, 7.0/46 no longer applies. As part of this change,
204        there's a new PCRE_INFO_HASCRORLF option for finding out whether a compiled
205        pattern has explicit CR or LF references.
206    
207    29. Added (*CR) etc for changing newline setting at start of pattern.
208    
209    
210    Version 7.2 19-Jun-07
211    ---------------------
212    
213     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
214        which is apparently normally available under Windows.
215    
216     2. Re-jig the pcregrep tests with different newline settings in an attempt
217        to make them independent of the local environment's newline setting.
218    
219     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
220    
221     4. Some of the "internals" tests were previously cut out when the link size
222        was not 2, because the output contained actual offsets. The recent new
223        "Z" feature of pcretest means that these can be cut out, making the tests
224        usable with all link sizes.
225    
226     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
227        stack recursion. This gives a massive performance boost under BSD, but just
228        a small improvement under Linux. However, it saves one field in the frame
229        in all cases.
230    
231     6. Added more features from the forthcoming Perl 5.10:
232    
233        (a) (?-n) (where n is a string of digits) is a relative subroutine or
234            recursion call. It refers to the nth most recently opened parentheses.
235    
236        (b) (?+n) is also a relative subroutine call; it refers to the nth next
237            to be opened parentheses.
238    
239        (c) Conditions that refer to capturing parentheses can be specified
240            relatively, for example, (?(-2)... or (?(+3)...
241    
242        (d) \K resets the start of the current match so that everything before
243            is not part of it.
244    
245        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
246    
247        (f) \g{name} is another synonym - part of Perl 5.10's unification of
248            reference syntax.
249    
250        (g) (?| introduces a group in which the numbering of parentheses in each
251            alternative starts with the same number.
252    
253        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
254    
255     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
256        PCRE_INFO_JCHANGED.
257    
258     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
259        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
260        for detecting groups that can match an empty string.
261    
262     9. A pattern with a very large number of alternatives (more than several
263        hundred) was running out of internal workspace during the pre-compile
264        phase, where pcre_compile() figures out how much memory will be needed. A
265        bit of new cunning has reduced the workspace needed for groups with
266        alternatives. The 1000-alternative test pattern now uses 12 bytes of
267        workspace instead of running out of the 4096 that are available.
268    
269    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
270    
271    11. Applied patch from Google to remove an optimization that didn't quite work.
272        The report of the bug said:
273    
274          pcrecpp::RE("a*").FullMatch("aaa") matches, while
275          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
276          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
277    
278    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
279        it matched the wrong number of bytes.
280    
281    
282    Version 7.1 24-Apr-07
283    ---------------------
284    
285     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
286        that is more "standard", making use of automake and other Autotools. There
287        is some re-arrangement of the files and adjustment of comments consequent
288        on this.
289    
290     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
291        for recursive directory scanning broke on some systems because the files
292        are not scanned in any specific order and on different systems the order
293        was different. A call to "sort" has been inserted into RunGrepTest for the
294        approprate test as a short-term fix. In the longer term there may be an
295        alternative.
296    
297     3. I had an email from Eric Raymond about problems translating some of PCRE's
298        man pages to HTML (despite the fact that I distribute HTML pages, some
299        people do their own conversions for various reasons). The problems
300        concerned the use of low-level troff macros .br and .in. I have therefore
301        removed all such uses from the man pages (some were redundant, some could
302        be replaced by .nf/.fi pairs). The 132html script that I use to generate
303        HTML has been updated to handle .nf/.fi and to complain if it encounters
304        .br or .in.
305    
306     4. Updated comments in configure.ac that get placed in config.h.in and also
307        arranged for config.h to be included in the distribution, with the name
308        config.h.generic, for the benefit of those who have to compile without
309        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
310    
311     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
312        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
313        makevp.bat for the current PCRE, using the additional files
314        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
315    
316     6. A Windows user reported a minor discrepancy with test 2, which turned out
317        to be caused by a trailing space on an input line that had got lost in his
318        copy. The trailing space was an accident, so I've just removed it.
319    
320     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
321        that is needed.
322    
323     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
324        as "const" (a) because they are and (b) because it helps the PHP
325        maintainers who have recently made a script to detect big data structures
326        in the php code that should be moved to the .rodata section. I remembered
327        to update Builducptable as well, so it won't revert if ucptable.h is ever
328        re-created.
329    
330     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
331        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
332        order to be able to cut out the UTF-8 tables in the latter when UTF-8
333        support is not required. This saves 1.5-2K of code, which is important in
334        some applications.
335    
336        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
337        so as not to refer to the tables, even though these functions will never be
338        called when UTF-8 support is disabled. Otherwise there are problems with a
339        shared library.
340    
341    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
342    
343        (a) It was defining its arguments as char * instead of void *.
344    
345        (b) It was assuming that all moves were upwards in memory; this was true
346            a long time ago when I wrote it, but is no longer the case.
347    
348        The emulated memove() is provided for those environments that have neither
349        memmove() nor bcopy(). I didn't think anyone used it these days, but that
350        is clearly not the case, as these two bugs were recently reported.
351    
352    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
353        and Detrail to create the HTML documentation, the .txt form of the man
354        pages, and it removes trailing spaces from listed files. It also creates
355        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
356        case, it wraps all the #defines with #ifndefs. This script should be run
357        before "make dist".
358    
359    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
360        with Unicode property support.
361    
362        (a) For a maximizing quantifier, if the two different cases of the
363            character were of different lengths in their UTF-8 codings (there are
364            some cases like this - I found 11), and the matching function had to
365            back up over a mixture of the two cases, it incorrectly assumed they
366            were both the same length.
367    
368        (b) When PCRE was configured to use the heap rather than the stack for
369            recursion during matching, it was not correctly preserving the data for
370            the other case of a UTF-8 character when checking ahead for a match
371            while processing a minimizing repeat. If the check also involved
372            matching a wide character, but failed, corruption could cause an
373            erroneous result when trying to check for a repeat of the original
374            character.
375    
376    13. Some tidying changes to the testing mechanism:
377    
378        (a) The RunTest script now detects the internal link size and whether there
379            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
380            values substituted by "configure". (The RunGrepTest script already did
381            this for UTF-8.) The configure.ac script no longer substitutes the
382            relevant variables.
383    
384        (b) The debugging options /B and /D in pcretest show the compiled bytecode
385            with length and offset values. This means that the output is different
386            for different internal link sizes. Test 2 is skipped for link sizes
387            other than 2 because of this, bypassing the problem. Unfortunately,
388            there was also a test in test 3 (the locale tests) that used /B and
389            failed for link sizes other than 2. Rather than cut the whole test out,
390            I have added a new /Z option to pcretest that replaces the length and
391            offset values with spaces. This is now used to make test 3 independent
392            of link size. (Test 2 will be tidied up later.)
393    
394    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
395        segmentation fault instead of returning the appropriate error message.
396    
397    15. In multiline mode when the newline sequence was set to "any", the pattern
398        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
399        This doesn't seem right; it now treats the CRLF combination as the line
400        ending, and so does not match in that case. It's only a pattern such as ^$
401        that would hit this one: something like ^ABC$ would have failed after \r
402        and then tried again after \r\n.
403    
404    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
405        in an attempt to make files that differ only in their line terminators
406        compare equal. This works on Linux.
407    
408    17. Under certain error circumstances pcregrep might try to free random memory
409        as it exited. This is now fixed, thanks to valgrind.
410    
411    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
412        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
413        was because its rules for how to advance for /g after matching an empty
414        string at the end of a line did not allow for this case. They now check for
415        it specially.
416    
417    20. pcretest is supposed to handle patterns and data of any length, by
418        extending its buffers when necessary. It was getting this wrong when the
419        buffer for a data line had to be extended.
420    
421    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
422        CRLF as a newline sequence.
423    
424    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
425        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
426        I have nevertheless tidied it up.
427    
428    23. Added some casts to kill warnings from HP-UX ia64 compiler.
429    
430    24. Added a man page for pcre-config.
431    
432    
433    Version 7.0 19-Dec-06
434    ---------------------
435    
436     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
437        moving to gcc 4.1.1.
438    
439     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
440        sys/time.h, which is documented as needed for this function. It doesn't
441        seem to matter on Linux, but it showed up on some releases of OS X.
442    
443     3. It seems that there are systems where bytes whose values are greater than
444        127 match isprint() in the "C" locale. The "C" locale should be the
445        default when a C program starts up. In most systems, only ASCII printing
446        characters match isprint(). This difference caused the output from pcretest
447        to vary, making some of the tests fail. I have changed pcretest so that:
448    
449        (a) When it is outputting text in the compiled version of a pattern, bytes
450            other than 32-126 are always shown as hex escapes.
451    
452        (b) When it is outputting text that is a matched part of a subject string,
453            it does the same, unless a different locale has been set for the match
454            (using the /L modifier). In this case, it uses isprint() to decide.
455    
456     4. Fixed a major bug that caused incorrect computation of the amount of memory
457        required for a compiled pattern when options that changed within the
458        pattern affected the logic of the preliminary scan that determines the
459        length. The relevant options are -x, and -i in UTF-8 mode. The result was
460        that the computed length was too small. The symptoms of this bug were
461        either the PCRE error "internal error: code overflow" from pcre_compile(),
462        or a glibc crash with a message such as "pcretest: free(): invalid next
463        size (fast)". Examples of patterns that provoked this bug (shown in
464        pcretest format) are:
465    
466          /(?-x: )/x
467          /(?x)(?-x: \s*#\s*)/
468          /((?i)[\x{c0}])/8
469          /(?i:[\x{c0}])/8
470    
471        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
472        is now done differently.
473    
474     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
475        wrapper classes; (b) implement a new function in the C++ scanner that is
476        more efficient than the old way of doing things because it avoids levels of
477        recursion in the regex matching; (c) add a paragraph to the documentation
478        for the FullMatch() function.
479    
480     6. The escape sequence \n was being treated as whatever was defined as
481        "newline". Not only was this contrary to the documentation, which states
482        that \n is character 10 (hex 0A), but it also went horribly wrong when
483        "newline" was defined as CRLF. This has been fixed.
484    
485     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
486        was being set to -1 for the "end of line" case (supposedly a value that no
487        character can have). Though this value is never used (the check for end of
488        line is "zero bytes in current character"), it caused compiler complaints.
489        I've changed it to 0xffffffff.
490    
491     8. In pcre_version.c, the version string was being built by a sequence of
492        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
493        string (as it is for production releases) called a macro with an empty
494        argument. The C standard says the result of this is undefined. The gcc
495        compiler treats it as an empty string (which was what was wanted) but it is
496        reported that Visual C gives an error. The source has been hacked around to
497        avoid this problem.
498    
499     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
500        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
501        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
502        of them did).
503    
504    10. Originally, pcretest opened its input and output without "b"; then I was
505        told that "b" was needed in some environments, so it was added for release
506        5.0 to both the input and output. (It makes no difference on Unix-like
507        systems.) Later I was told that it is wrong for the input on Windows. I've
508        now abstracted the modes into two macros, to make it easier to fiddle with
509        them, and removed "b" from the input mode under Windows.
510    
511    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
512    
513    12. Added -help and --help to pcretest as an official way of being reminded
514        of the options.
515    
516    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
517        and pcrecpp.cc because they annoy compilers at high warning levels.
518    
519    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
520    
521    15. Fixed an occurrence of == in configure.ac that should have been = (shell
522        scripts are not C programs :-) and which was not noticed because it works
523        on Linux.
524    
525    16. pcretest is supposed to handle any length of pattern and data line (as one
526        line or as a continued sequence of lines) by extending its input buffer if
527        necessary. This feature was broken for very long pattern lines, leading to
528        a string of junk being passed to pcre_compile() if the pattern was longer
529        than about 50K.
530    
531    17. I have done a major re-factoring of the way pcre_compile() computes the
532        amount of memory needed for a compiled pattern. Previously, there was code
533        that made a preliminary scan of the pattern in order to do this. That was
534        OK when PCRE was new, but as the facilities have expanded, it has become
535        harder and harder to keep it in step with the real compile phase, and there
536        have been a number of bugs (see for example, 4 above). I have now found a
537        cunning way of running the real compile function in a "fake" mode that
538        enables it to compute how much memory it would need, while actually only
539        ever using a few hundred bytes of working memory and without too many
540        tests of the mode. This should make future maintenance and development
541        easier. A side effect of this work is that the limit of 200 on the nesting
542        depth of parentheses has been removed (though this was never a serious
543        limitation, I suspect). However, there is a downside: pcre_compile() now
544        runs more slowly than before (30% or more, depending on the pattern). I
545        hope this isn't a big issue. There is no effect on runtime performance.
546    
547    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
548        newline (only possible for the last line of a file) and it was a
549        pattern that set a locale (followed by /Lsomething), pcretest crashed.
550    
551    19. Added additional timing features to pcretest. (1) The -tm option now times
552        matching only, not compiling. (2) Both -t and -tm can be followed, as a
553        separate command line item, by a number that specifies the number of
554        repeats to use when timing. The default is 50000; this gives better
555        precision, but takes uncomfortably long for very large patterns.
556    
557    20. Extended pcre_study() to be more clever in cases where a branch of a
558        subpattern has no definite first character. For example, (a*|b*)[cd] would
559        previously give no result from pcre_study(). Now it recognizes that the
560        first character must be a, b, c, or d.
561    
562    21. There was an incorrect error "recursive call could loop indefinitely" if
563        a subpattern (or the entire pattern) that was being tested for matching an
564        empty string contained only one non-empty item after a nested subpattern.
565        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
566        incorrectly, because the \d was being skipped in the check.
567    
568    22. The pcretest program now has a new pattern option /B and a command line
569        option -b, which is equivalent to adding /B to every pattern. This causes
570        it to show the compiled bytecode, without the additional information that
571        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
572        is the same as /B/I).
573    
574    23. A new optimization is now able automatically to treat some sequences such
575        as a*b as a*+b. More specifically, if something simple (such as a character
576        or a simple class like \d) has an unlimited quantifier, and is followed by
577        something that cannot possibly match the quantified thing, the quantifier
578        is automatically "possessified".
579    
580    24. A recursive reference to a subpattern whose number was greater than 39
581        went wrong under certain circumstances in UTF-8 mode. This bug could also
582        have affected the operation of pcre_study().
583    
584    25. Realized that a little bit of performance could be had by replacing
585        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
586    
587    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
588    
589    27. Possessive quantifiers such as a++ were previously implemented by turning
590        them into atomic groups such as ($>a+). Now they have their own opcodes,
591        which improves performance. This includes the automatically created ones
592        from 23 above.
593    
594    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
595        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
596        the first matched character to be a colon. This applied both to named and
597        numbered groups.
598    
599    29. The ucpinternal.h header file was missing its idempotency #ifdef.
600    
601    30. I was sent a "project" file called libpcre.a.dev which I understand makes
602        building PCRE on Windows easier, so I have included it in the distribution.
603    
604    31. There is now a check in pcretest against a ridiculously large number being
605        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
606        loop, the loop is abandoned.
607    
608    32. Forward references to subpatterns in conditions such as (?(2)...) where
609        subpattern 2 is defined later cause pcre_compile() to search forwards in
610        the pattern for the relevant set of parentheses. This search went wrong
611        when there were unescaped parentheses in a character class, parentheses
612        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
613    
614    33. "Subroutine" calls and backreferences were previously restricted to
615        referencing subpatterns earlier in the regex. This restriction has now
616        been removed.
617    
618    34. Added a number of extra features that are going to be in Perl 5.10. On the
619        whole, these are just syntactic alternatives for features that PCRE had
620        previously implemented using the Python syntax or my own invention. The
621        other formats are all retained for compatibility.
622    
623        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
624            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
625            also .NET compatible.
626    
627        (b) A recursion or subroutine call to a named group can now be defined as
628            (?&name) as well as (?P>name).
629    
630        (c) A backreference to a named group can now be defined as \k<name> or
631            \k'name' as well as (?P=name). The new forms, as well as being in Perl
632            5.10, are also .NET compatible.
633    
634        (d) A conditional reference to a named group can now use the syntax
635            (?(<name>) or (?('name') as well as (?(name).
636    
637        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
638            groups (named and numbered) that are never evaluated inline, but can be
639            called as "subroutines" from elsewhere. In effect, the DEFINE condition
640            is always false. There may be only one alternative in such a group.
641    
642        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
643            as the simple (?(R). The condition is true only if the most recent
644            recursion is that of the given number or name. It does not search out
645            through the entire recursion stack.
646    
647        (g) The escape \gN or \g{N} has been added, where N is a positive or
648            negative number, specifying an absolute or relative reference.
649    
650    35. Tidied to get rid of some further signed/unsigned compiler warnings and
651        some "unreachable code" warnings.
652    
653    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
654        things, this adds five new scripts.
655    
656    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
657        There were also incompatibilities regarding the handling of \Q..\E inside
658        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
659        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
660    
661    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
662        matches an empty string, and forcibly breaks the loop. There were bugs in
663        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
664        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
665        separate and independent bugs (that affected different cases) have been
666        fixed.
667    
668    39. Refactored the code to abolish the use of different opcodes for small
669        capturing bracket numbers. This is a tidy that I avoided doing when I
670        removed the limit on the number of capturing brackets for 3.5 back in 2001.
671        The new approach is not only tidier, it makes it possible to reduce the
672        memory needed to fix the previous bug (38).
673    
674    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
675        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
676        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
677        mode.
678    
679    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
680        report.
681    
682    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
683        copy construction and assignment in the C++ wrapper.
684    
685    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
686        couple of bugs that could have given wrong results in the "--newline=crlf"
687        case.
688    
689    44. Added a number of casts and did some reorganization of signed/unsigned int
690        variables following suggestions from Dair Grant. Also renamed the variable
691        "this" as "item" because it is a C++ keyword.
692    
693    45. Arranged for dftables to add
694    
695          #include "pcre_internal.h"
696    
697        to pcre_chartables.c because without it, gcc 4.x may remove the array
698        definition from the final binary if PCRE is built into a static library and
699        dead code stripping is activated.
700    
701    46. For an unanchored pattern, if a match attempt fails at the start of a
702        newline sequence, and the newline setting is CRLF or ANY, and the next two
703        characters are CRLF, advance by two characters instead of one.
704    
705    
706  Version 6.7 04-Jul-06  Version 6.7 04-Jul-06
707  ---------------------  ---------------------
708    

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