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revision 87 by nigel, Sat Feb 24 21:41:21 2007 UTC revision 212 by ph10, Thu Aug 9 11:16:34 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4    Version 7.3 09-Aug-07
5    ---------------------
6    
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:
12    
13          #include "pcre.h"
14    
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.
18    
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.
26    
27     3. A small performance improvement in the DOTALL UTF-8 mode .* case.
28    
29     4. Debugging: adjusted the names of opcodes for different kinds of parentheses
30        in debug output.
31    
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.
34    
35     6. ESC_K was left out of the EBCDIC table.
36    
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.
50    
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.
55    
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.
67    
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.
72    
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.
79    
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.
86    
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".
90    
91    13. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
92        (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
93    
94    14. Optimized (?!) to (*FAIL).
95    
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.
101    
102    
103    Version 7.2 19-Jun-07
104    ---------------------
105    
106     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
107        which is apparently normally available under Windows.
108    
109     2. Re-jig the pcregrep tests with different newline settings in an attempt
110        to make them independent of the local environment's newline setting.
111    
112     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
113    
114     4. Some of the "internals" tests were previously cut out when the link size
115        was not 2, because the output contained actual offsets. The recent new
116        "Z" feature of pcretest means that these can be cut out, making the tests
117        usable with all link sizes.
118    
119     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
120        stack recursion. This gives a massive performance boost under BSD, but just
121        a small improvement under Linux. However, it saves one field in the frame
122        in all cases.
123    
124     6. Added more features from the forthcoming Perl 5.10:
125    
126        (a) (?-n) (where n is a string of digits) is a relative subroutine or
127            recursion call. It refers to the nth most recently opened parentheses.
128    
129        (b) (?+n) is also a relative subroutine call; it refers to the nth next
130            to be opened parentheses.
131    
132        (c) Conditions that refer to capturing parentheses can be specified
133            relatively, for example, (?(-2)... or (?(+3)...
134    
135        (d) \K resets the start of the current match so that everything before
136            is not part of it.
137    
138        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
139    
140        (f) \g{name} is another synonym - part of Perl 5.10's unification of
141            reference syntax.
142    
143        (g) (?| introduces a group in which the numbering of parentheses in each
144            alternative starts with the same number.
145    
146        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
147    
148     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
149        PCRE_INFO_JCHANGED.
150    
151     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
152        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
153        for detecting groups that can match an empty string.
154    
155     9. A pattern with a very large number of alternatives (more than several
156        hundred) was running out of internal workspace during the pre-compile
157        phase, where pcre_compile() figures out how much memory will be needed. A
158        bit of new cunning has reduced the workspace needed for groups with
159        alternatives. The 1000-alternative test pattern now uses 12 bytes of
160        workspace instead of running out of the 4096 that are available.
161    
162    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
163    
164    11. Applied patch from Google to remove an optimization that didn't quite work.
165        The report of the bug said:
166    
167          pcrecpp::RE("a*").FullMatch("aaa") matches, while
168          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
169          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
170    
171    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
172        it matched the wrong number of bytes.
173    
174    
175    Version 7.1 24-Apr-07
176    ---------------------
177    
178     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
179        that is more "standard", making use of automake and other Autotools. There
180        is some re-arrangement of the files and adjustment of comments consequent
181        on this.
182    
183     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
184        for recursive directory scanning broke on some systems because the files
185        are not scanned in any specific order and on different systems the order
186        was different. A call to "sort" has been inserted into RunGrepTest for the
187        approprate test as a short-term fix. In the longer term there may be an
188        alternative.
189    
190     3. I had an email from Eric Raymond about problems translating some of PCRE's
191        man pages to HTML (despite the fact that I distribute HTML pages, some
192        people do their own conversions for various reasons). The problems
193        concerned the use of low-level troff macros .br and .in. I have therefore
194        removed all such uses from the man pages (some were redundant, some could
195        be replaced by .nf/.fi pairs). The 132html script that I use to generate
196        HTML has been updated to handle .nf/.fi and to complain if it encounters
197        .br or .in.
198    
199     4. Updated comments in configure.ac that get placed in config.h.in and also
200        arranged for config.h to be included in the distribution, with the name
201        config.h.generic, for the benefit of those who have to compile without
202        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
203    
204     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
205        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
206        makevp.bat for the current PCRE, using the additional files
207        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
208    
209     6. A Windows user reported a minor discrepancy with test 2, which turned out
210        to be caused by a trailing space on an input line that had got lost in his
211        copy. The trailing space was an accident, so I've just removed it.
212    
213     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
214        that is needed.
215    
216     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
217        as "const" (a) because they are and (b) because it helps the PHP
218        maintainers who have recently made a script to detect big data structures
219        in the php code that should be moved to the .rodata section. I remembered
220        to update Builducptable as well, so it won't revert if ucptable.h is ever
221        re-created.
222    
223     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
224        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
225        order to be able to cut out the UTF-8 tables in the latter when UTF-8
226        support is not required. This saves 1.5-2K of code, which is important in
227        some applications.
228    
229        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
230        so as not to refer to the tables, even though these functions will never be
231        called when UTF-8 support is disabled. Otherwise there are problems with a
232        shared library.
233    
234    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
235    
236        (a) It was defining its arguments as char * instead of void *.
237    
238        (b) It was assuming that all moves were upwards in memory; this was true
239            a long time ago when I wrote it, but is no longer the case.
240    
241        The emulated memove() is provided for those environments that have neither
242        memmove() nor bcopy(). I didn't think anyone used it these days, but that
243        is clearly not the case, as these two bugs were recently reported.
244    
245    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
246        and Detrail to create the HTML documentation, the .txt form of the man
247        pages, and it removes trailing spaces from listed files. It also creates
248        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
249        case, it wraps all the #defines with #ifndefs. This script should be run
250        before "make dist".
251    
252    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
253        with Unicode property support.
254    
255        (a) For a maximizing quantifier, if the two different cases of the
256            character were of different lengths in their UTF-8 codings (there are
257            some cases like this - I found 11), and the matching function had to
258            back up over a mixture of the two cases, it incorrectly assumed they
259            were both the same length.
260    
261        (b) When PCRE was configured to use the heap rather than the stack for
262            recursion during matching, it was not correctly preserving the data for
263            the other case of a UTF-8 character when checking ahead for a match
264            while processing a minimizing repeat. If the check also involved
265            matching a wide character, but failed, corruption could cause an
266            erroneous result when trying to check for a repeat of the original
267            character.
268    
269    13. Some tidying changes to the testing mechanism:
270    
271        (a) The RunTest script now detects the internal link size and whether there
272            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
273            values substituted by "configure". (The RunGrepTest script already did
274            this for UTF-8.) The configure.ac script no longer substitutes the
275            relevant variables.
276    
277        (b) The debugging options /B and /D in pcretest show the compiled bytecode
278            with length and offset values. This means that the output is different
279            for different internal link sizes. Test 2 is skipped for link sizes
280            other than 2 because of this, bypassing the problem. Unfortunately,
281            there was also a test in test 3 (the locale tests) that used /B and
282            failed for link sizes other than 2. Rather than cut the whole test out,
283            I have added a new /Z option to pcretest that replaces the length and
284            offset values with spaces. This is now used to make test 3 independent
285            of link size. (Test 2 will be tidied up later.)
286    
287    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
288        segmentation fault instead of returning the appropriate error message.
289    
290    15. In multiline mode when the newline sequence was set to "any", the pattern
291        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
292        This doesn't seem right; it now treats the CRLF combination as the line
293        ending, and so does not match in that case. It's only a pattern such as ^$
294        that would hit this one: something like ^ABC$ would have failed after \r
295        and then tried again after \r\n.
296    
297    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
298        in an attempt to make files that differ only in their line terminators
299        compare equal. This works on Linux.
300    
301    17. Under certain error circumstances pcregrep might try to free random memory
302        as it exited. This is now fixed, thanks to valgrind.
303    
304    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
305        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
306        was because its rules for how to advance for /g after matching an empty
307        string at the end of a line did not allow for this case. They now check for
308        it specially.
309    
310    20. pcretest is supposed to handle patterns and data of any length, by
311        extending its buffers when necessary. It was getting this wrong when the
312        buffer for a data line had to be extended.
313    
314    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
315        CRLF as a newline sequence.
316    
317    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
318        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
319        I have nevertheless tidied it up.
320    
321    23. Added some casts to kill warnings from HP-UX ia64 compiler.
322    
323    24. Added a man page for pcre-config.
324    
325    
326    Version 7.0 19-Dec-06
327    ---------------------
328    
329     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
330        moving to gcc 4.1.1.
331    
332     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
333        sys/time.h, which is documented as needed for this function. It doesn't
334        seem to matter on Linux, but it showed up on some releases of OS X.
335    
336     3. It seems that there are systems where bytes whose values are greater than
337        127 match isprint() in the "C" locale. The "C" locale should be the
338        default when a C program starts up. In most systems, only ASCII printing
339        characters match isprint(). This difference caused the output from pcretest
340        to vary, making some of the tests fail. I have changed pcretest so that:
341    
342        (a) When it is outputting text in the compiled version of a pattern, bytes
343            other than 32-126 are always shown as hex escapes.
344    
345        (b) When it is outputting text that is a matched part of a subject string,
346            it does the same, unless a different locale has been set for the match
347            (using the /L modifier). In this case, it uses isprint() to decide.
348    
349     4. Fixed a major bug that caused incorrect computation of the amount of memory
350        required for a compiled pattern when options that changed within the
351        pattern affected the logic of the preliminary scan that determines the
352        length. The relevant options are -x, and -i in UTF-8 mode. The result was
353        that the computed length was too small. The symptoms of this bug were
354        either the PCRE error "internal error: code overflow" from pcre_compile(),
355        or a glibc crash with a message such as "pcretest: free(): invalid next
356        size (fast)". Examples of patterns that provoked this bug (shown in
357        pcretest format) are:
358    
359          /(?-x: )/x
360          /(?x)(?-x: \s*#\s*)/
361          /((?i)[\x{c0}])/8
362          /(?i:[\x{c0}])/8
363    
364        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
365        is now done differently.
366    
367     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
368        wrapper classes; (b) implement a new function in the C++ scanner that is
369        more efficient than the old way of doing things because it avoids levels of
370        recursion in the regex matching; (c) add a paragraph to the documentation
371        for the FullMatch() function.
372    
373     6. The escape sequence \n was being treated as whatever was defined as
374        "newline". Not only was this contrary to the documentation, which states
375        that \n is character 10 (hex 0A), but it also went horribly wrong when
376        "newline" was defined as CRLF. This has been fixed.
377    
378     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
379        was being set to -1 for the "end of line" case (supposedly a value that no
380        character can have). Though this value is never used (the check for end of
381        line is "zero bytes in current character"), it caused compiler complaints.
382        I've changed it to 0xffffffff.
383    
384     8. In pcre_version.c, the version string was being built by a sequence of
385        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
386        string (as it is for production releases) called a macro with an empty
387        argument. The C standard says the result of this is undefined. The gcc
388        compiler treats it as an empty string (which was what was wanted) but it is
389        reported that Visual C gives an error. The source has been hacked around to
390        avoid this problem.
391    
392     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
393        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
394        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
395        of them did).
396    
397    10. Originally, pcretest opened its input and output without "b"; then I was
398        told that "b" was needed in some environments, so it was added for release
399        5.0 to both the input and output. (It makes no difference on Unix-like
400        systems.) Later I was told that it is wrong for the input on Windows. I've
401        now abstracted the modes into two macros, to make it easier to fiddle with
402        them, and removed "b" from the input mode under Windows.
403    
404    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
405    
406    12. Added -help and --help to pcretest as an official way of being reminded
407        of the options.
408    
409    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
410        and pcrecpp.cc because they annoy compilers at high warning levels.
411    
412    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
413    
414    15. Fixed an occurrence of == in configure.ac that should have been = (shell
415        scripts are not C programs :-) and which was not noticed because it works
416        on Linux.
417    
418    16. pcretest is supposed to handle any length of pattern and data line (as one
419        line or as a continued sequence of lines) by extending its input buffer if
420        necessary. This feature was broken for very long pattern lines, leading to
421        a string of junk being passed to pcre_compile() if the pattern was longer
422        than about 50K.
423    
424    17. I have done a major re-factoring of the way pcre_compile() computes the
425        amount of memory needed for a compiled pattern. Previously, there was code
426        that made a preliminary scan of the pattern in order to do this. That was
427        OK when PCRE was new, but as the facilities have expanded, it has become
428        harder and harder to keep it in step with the real compile phase, and there
429        have been a number of bugs (see for example, 4 above). I have now found a
430        cunning way of running the real compile function in a "fake" mode that
431        enables it to compute how much memory it would need, while actually only
432        ever using a few hundred bytes of working memory and without too many
433        tests of the mode. This should make future maintenance and development
434        easier. A side effect of this work is that the limit of 200 on the nesting
435        depth of parentheses has been removed (though this was never a serious
436        limitation, I suspect). However, there is a downside: pcre_compile() now
437        runs more slowly than before (30% or more, depending on the pattern). I
438        hope this isn't a big issue. There is no effect on runtime performance.
439    
440    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
441        newline (only possible for the last line of a file) and it was a
442        pattern that set a locale (followed by /Lsomething), pcretest crashed.
443    
444    19. Added additional timing features to pcretest. (1) The -tm option now times
445        matching only, not compiling. (2) Both -t and -tm can be followed, as a
446        separate command line item, by a number that specifies the number of
447        repeats to use when timing. The default is 50000; this gives better
448        precision, but takes uncomfortably long for very large patterns.
449    
450    20. Extended pcre_study() to be more clever in cases where a branch of a
451        subpattern has no definite first character. For example, (a*|b*)[cd] would
452        previously give no result from pcre_study(). Now it recognizes that the
453        first character must be a, b, c, or d.
454    
455    21. There was an incorrect error "recursive call could loop indefinitely" if
456        a subpattern (or the entire pattern) that was being tested for matching an
457        empty string contained only one non-empty item after a nested subpattern.
458        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
459        incorrectly, because the \d was being skipped in the check.
460    
461    22. The pcretest program now has a new pattern option /B and a command line
462        option -b, which is equivalent to adding /B to every pattern. This causes
463        it to show the compiled bytecode, without the additional information that
464        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
465        is the same as /B/I).
466    
467    23. A new optimization is now able automatically to treat some sequences such
468        as a*b as a*+b. More specifically, if something simple (such as a character
469        or a simple class like \d) has an unlimited quantifier, and is followed by
470        something that cannot possibly match the quantified thing, the quantifier
471        is automatically "possessified".
472    
473    24. A recursive reference to a subpattern whose number was greater than 39
474        went wrong under certain circumstances in UTF-8 mode. This bug could also
475        have affected the operation of pcre_study().
476    
477    25. Realized that a little bit of performance could be had by replacing
478        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
479    
480    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
481    
482    27. Possessive quantifiers such as a++ were previously implemented by turning
483        them into atomic groups such as ($>a+). Now they have their own opcodes,
484        which improves performance. This includes the automatically created ones
485        from 23 above.
486    
487    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
488        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
489        the first matched character to be a colon. This applied both to named and
490        numbered groups.
491    
492    29. The ucpinternal.h header file was missing its idempotency #ifdef.
493    
494    30. I was sent a "project" file called libpcre.a.dev which I understand makes
495        building PCRE on Windows easier, so I have included it in the distribution.
496    
497    31. There is now a check in pcretest against a ridiculously large number being
498        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
499        loop, the loop is abandoned.
500    
501    32. Forward references to subpatterns in conditions such as (?(2)...) where
502        subpattern 2 is defined later cause pcre_compile() to search forwards in
503        the pattern for the relevant set of parentheses. This search went wrong
504        when there were unescaped parentheses in a character class, parentheses
505        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
506    
507    33. "Subroutine" calls and backreferences were previously restricted to
508        referencing subpatterns earlier in the regex. This restriction has now
509        been removed.
510    
511    34. Added a number of extra features that are going to be in Perl 5.10. On the
512        whole, these are just syntactic alternatives for features that PCRE had
513        previously implemented using the Python syntax or my own invention. The
514        other formats are all retained for compatibility.
515    
516        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
517            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
518            also .NET compatible.
519    
520        (b) A recursion or subroutine call to a named group can now be defined as
521            (?&name) as well as (?P>name).
522    
523        (c) A backreference to a named group can now be defined as \k<name> or
524            \k'name' as well as (?P=name). The new forms, as well as being in Perl
525            5.10, are also .NET compatible.
526    
527        (d) A conditional reference to a named group can now use the syntax
528            (?(<name>) or (?('name') as well as (?(name).
529    
530        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
531            groups (named and numbered) that are never evaluated inline, but can be
532            called as "subroutines" from elsewhere. In effect, the DEFINE condition
533            is always false. There may be only one alternative in such a group.
534    
535        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
536            as the simple (?(R). The condition is true only if the most recent
537            recursion is that of the given number or name. It does not search out
538            through the entire recursion stack.
539    
540        (g) The escape \gN or \g{N} has been added, where N is a positive or
541            negative number, specifying an absolute or relative reference.
542    
543    35. Tidied to get rid of some further signed/unsigned compiler warnings and
544        some "unreachable code" warnings.
545    
546    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
547        things, this adds five new scripts.
548    
549    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
550        There were also incompatibilities regarding the handling of \Q..\E inside
551        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
552        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
553    
554    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
555        matches an empty string, and forcibly breaks the loop. There were bugs in
556        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
557        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
558        separate and independent bugs (that affected different cases) have been
559        fixed.
560    
561    39. Refactored the code to abolish the use of different opcodes for small
562        capturing bracket numbers. This is a tidy that I avoided doing when I
563        removed the limit on the number of capturing brackets for 3.5 back in 2001.
564        The new approach is not only tidier, it makes it possible to reduce the
565        memory needed to fix the previous bug (38).
566    
567    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
568        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
569        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
570        mode.
571    
572    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
573        report.
574    
575    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
576        copy construction and assignment in the C++ wrapper.
577    
578    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
579        couple of bugs that could have given wrong results in the "--newline=crlf"
580        case.
581    
582    44. Added a number of casts and did some reorganization of signed/unsigned int
583        variables following suggestions from Dair Grant. Also renamed the variable
584        "this" as "item" because it is a C++ keyword.
585    
586    45. Arranged for dftables to add
587    
588          #include "pcre_internal.h"
589    
590        to pcre_chartables.c because without it, gcc 4.x may remove the array
591        definition from the final binary if PCRE is built into a static library and
592        dead code stripping is activated.
593    
594    46. For an unanchored pattern, if a match attempt fails at the start of a
595        newline sequence, and the newline setting is CRLF or ANY, and the next two
596        characters are CRLF, advance by two characters instead of one.
597    
598    
599    Version 6.7 04-Jul-06
600    ---------------------
601    
602     1. In order to handle tests when input lines are enormously long, pcretest has
603        been re-factored so that it automatically extends its buffers when
604        necessary. The code is crude, but this _is_ just a test program. The
605        default size has been increased from 32K to 50K.
606    
607     2. The code in pcre_study() was using the value of the re argument before
608        testing it for NULL. (Of course, in any sensible call of the function, it
609        won't be NULL.)
610    
611     3. The memmove() emulation function in pcre_internal.h, which is used on
612        systems that lack both memmove() and bcopy() - that is, hardly ever -
613        was missing a "static" storage class specifier.
614    
615     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
616        containing an extended class (one that cannot be represented by a bitmap
617        because it contains high-valued characters or Unicode property items, e.g.
618        [\pZ]). Almost always one would set UTF-8 mode when processing such a
619        pattern, but PCRE should not loop if you do not (it no longer does).
620        [Detail: two cases were found: (a) a repeated subpattern containing an
621        extended class; (b) a recursive reference to a subpattern that followed a
622        previous extended class. It wasn't skipping over the extended class
623        correctly when UTF-8 mode was not set.]
624    
625     5. A negated single-character class was not being recognized as fixed-length
626        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
627        compile error "lookbehind assertion is not fixed length".
628    
629     6. The RunPerlTest auxiliary script was showing an unexpected difference
630        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
631        write a Perl script that can interpret lines of an input file either as
632        byte characters or as UTF-8, which is what "perltest" was being required to
633        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
634        can't do is switch easily at run time between having the "use utf8;" pragma
635        or not. In the end, I fudged it by using the RunPerlTest script to insert
636        "use utf8;" explicitly for the UTF-8 tests.
637    
638     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
639        the end of the subject string, contrary to the documentation and to what
640        Perl does. This was true of both matching functions. Now it matches only at
641        the start of the subject and immediately after *internal* newlines.
642    
643     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
644        a pointer to an int instead of a pointer to an unsigned long int. This
645        caused problems on 64-bit systems.
646    
647     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
648        instance of the 'standard' template library not being so standard".
649    
650    10. There was no check on the number of named subpatterns nor the maximum
651        length of a subpattern name. The product of these values is used to compute
652        the size of the memory block for a compiled pattern. By supplying a very
653        long subpattern name and a large number of named subpatterns, the size
654        computation could be caused to overflow. This is now prevented by limiting
655        the length of names to 32 characters, and the number of named subpatterns
656        to 10,000.
657    
658    11. Subpatterns that are repeated with specific counts have to be replicated in
659        the compiled pattern. The size of memory for this was computed from the
660        length of the subpattern and the repeat count. The latter is limited to
661        65535, but there was no limit on the former, meaning that integer overflow
662        could in principle occur. The compiled length of a repeated subpattern is
663        now limited to 30,000 bytes in order to prevent this.
664    
665    12. Added the optional facility to have named substrings with the same name.
666    
667    13. Added the ability to use a named substring as a condition, using the
668        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
669        are numbers (not recommended). Forward references are permitted.
670    
671    14. Added forward references in named backreferences (if you see what I mean).
672    
673    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
674        pattern could run off the end of the subject. For example, the pattern
675        "(?s)(.{1,5})"8 did this with the subject "ab".
676    
677    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
678        PCRE_CASELESS was set when matching characters that were quantified with ?
679        or *.
680    
681    17. A character class other than a single negated character that had a minimum
682        but no maximum quantifier - for example [ab]{6,} - was not handled
683        correctly by pce_dfa_exec(). It would match only one character.
684    
685    18. A valid (though odd) pattern that looked like a POSIX character
686        class but used an invalid character after [ (for example [[,abc,]]) caused
687        pcre_compile() to give the error "Failed: internal error: code overflow" or
688        in some cases to crash with a glibc free() error. This could even happen if
689        the pattern terminated after [[ but there just happened to be a sequence of
690        letters, a binary zero, and a closing ] in the memory that followed.
691    
692    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
693        over the years. Originally (before any Unicode support), just the bottom 8
694        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
695        output from "man perlunicode" includes this:
696    
697          The regular expression compiler produces polymorphic opcodes.  That
698          is, the pattern adapts to the data and automatically switches to
699          the Unicode character scheme when presented with Unicode data--or
700          instead uses a traditional byte scheme when presented with byte
701          data.
702    
703        Sadly, a wide octal escape does not cause a switch, and in a string with
704        no other multibyte characters, these octal escapes are treated as before.
705        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
706        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
707        Unicode string.
708    
709        I have not perpetrated such confusion in PCRE. Up till now, it took just
710        the bottom 8 bits, as in old Perl. I have now made octal escapes with
711        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
712        translate to the appropriate multibyte character.
713    
714    29. Applied some refactoring to reduce the number of warnings from Microsoft
715        and Borland compilers. This has included removing the fudge introduced
716        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
717        a warning about an unused variable.
718    
719    21. PCRE has not included VT (character 0x0b) in the set of whitespace
720        characters since release 4.0, because Perl (from release 5.004) does not.
721        [Or at least, is documented not to: some releases seem to be in conflict
722        with the documentation.] However, when a pattern was studied with
723        pcre_study() and all its branches started with \s, PCRE still included VT
724        as a possible starting character. Of course, this did no harm; it just
725        caused an unnecessary match attempt.
726    
727    22. Removed a now-redundant internal flag bit that recorded the fact that case
728        dependency changed within the pattern. This was once needed for "required
729        byte" processing, but is no longer used. This recovers a now-scarce options
730        bit. Also moved the least significant internal flag bit to the most-
731        significant bit of the word, which was not previously used (hangover from
732        the days when it was an int rather than a uint) to free up another bit for
733        the future.
734    
735    23. Added support for CRLF line endings as well as CR and LF. As well as the
736        default being selectable at build time, it can now be changed at runtime
737        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
738        specify that it is scanning data with non-default line endings.
739    
740    24. Changed the definition of CXXLINK to make it agree with the definition of
741        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
742    
743    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
744        recursions. This makes a big different to stack usage for some patterns.
745    
746    26. If a subpattern containing a named recursion or subroutine reference such
747        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
748        the space required for the compiled pattern went wrong and gave too small a
749        value. Depending on the environment, this could lead to "Failed: internal
750        error: code overflow at offset 49" or "glibc detected double free or
751        corruption" errors.
752    
753    27. Applied patches from Google (a) to support the new newline modes and (b) to
754        advance over multibyte UTF-8 characters in GlobalReplace.
755    
756    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
757        difference for some implementation of PCRE in some Windows version.
758    
759    29. Added some extra testing facilities to pcretest:
760    
761        \q<number>   in a data line sets the "match limit" value
762        \Q<number>   in a data line sets the "match recursion limt" value
763        -S <number>  sets the stack size, where <number> is in megabytes
764    
765        The -S option isn't available for Windows.
766    
767    
768    Version 6.6 06-Feb-06
769    ---------------------
770    
771     1. Change 16(a) for 6.5 broke things, because PCRE_DATA_SCOPE was not defined
772        in pcreposix.h. I have copied the definition from pcre.h.
773    
774     2. Change 25 for 6.5 broke compilation in a build directory out-of-tree
775        because pcre.h is no longer a built file.
776    
777     3. Added Jeff Friedl's additional debugging patches to pcregrep. These are
778        not normally included in the compiled code.
779    
780    
781  Version 6.5 01-Feb-06  Version 6.5 01-Feb-06
782  ---------------------  ---------------------
783    

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