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revision 87 by nigel, Sat Feb 24 21:41:21 2007 UTC revision 207 by ph10, Mon Aug 6 09:32:14 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4    Version 7.3 05-Jul-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    
92    Version 7.2 19-Jun-07
93    ---------------------
94    
95     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
96        which is apparently normally available under Windows.
97    
98     2. Re-jig the pcregrep tests with different newline settings in an attempt
99        to make them independent of the local environment's newline setting.
100    
101     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
102    
103     4. Some of the "internals" tests were previously cut out when the link size
104        was not 2, because the output contained actual offsets. The recent new
105        "Z" feature of pcretest means that these can be cut out, making the tests
106        usable with all link sizes.
107    
108     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
109        stack recursion. This gives a massive performance boost under BSD, but just
110        a small improvement under Linux. However, it saves one field in the frame
111        in all cases.
112    
113     6. Added more features from the forthcoming Perl 5.10:
114    
115        (a) (?-n) (where n is a string of digits) is a relative subroutine or
116            recursion call. It refers to the nth most recently opened parentheses.
117    
118        (b) (?+n) is also a relative subroutine call; it refers to the nth next
119            to be opened parentheses.
120    
121        (c) Conditions that refer to capturing parentheses can be specified
122            relatively, for example, (?(-2)... or (?(+3)...
123    
124        (d) \K resets the start of the current match so that everything before
125            is not part of it.
126    
127        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
128    
129        (f) \g{name} is another synonym - part of Perl 5.10's unification of
130            reference syntax.
131    
132        (g) (?| introduces a group in which the numbering of parentheses in each
133            alternative starts with the same number.
134    
135        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
136    
137     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
138        PCRE_INFO_JCHANGED.
139    
140     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
141        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
142        for detecting groups that can match an empty string.
143    
144     9. A pattern with a very large number of alternatives (more than several
145        hundred) was running out of internal workspace during the pre-compile
146        phase, where pcre_compile() figures out how much memory will be needed. A
147        bit of new cunning has reduced the workspace needed for groups with
148        alternatives. The 1000-alternative test pattern now uses 12 bytes of
149        workspace instead of running out of the 4096 that are available.
150    
151    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
152    
153    11. Applied patch from Google to remove an optimization that didn't quite work.
154        The report of the bug said:
155    
156          pcrecpp::RE("a*").FullMatch("aaa") matches, while
157          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
158          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
159    
160    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
161        it matched the wrong number of bytes.
162    
163    
164    Version 7.1 24-Apr-07
165    ---------------------
166    
167     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
168        that is more "standard", making use of automake and other Autotools. There
169        is some re-arrangement of the files and adjustment of comments consequent
170        on this.
171    
172     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
173        for recursive directory scanning broke on some systems because the files
174        are not scanned in any specific order and on different systems the order
175        was different. A call to "sort" has been inserted into RunGrepTest for the
176        approprate test as a short-term fix. In the longer term there may be an
177        alternative.
178    
179     3. I had an email from Eric Raymond about problems translating some of PCRE's
180        man pages to HTML (despite the fact that I distribute HTML pages, some
181        people do their own conversions for various reasons). The problems
182        concerned the use of low-level troff macros .br and .in. I have therefore
183        removed all such uses from the man pages (some were redundant, some could
184        be replaced by .nf/.fi pairs). The 132html script that I use to generate
185        HTML has been updated to handle .nf/.fi and to complain if it encounters
186        .br or .in.
187    
188     4. Updated comments in configure.ac that get placed in config.h.in and also
189        arranged for config.h to be included in the distribution, with the name
190        config.h.generic, for the benefit of those who have to compile without
191        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
192    
193     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
194        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
195        makevp.bat for the current PCRE, using the additional files
196        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
197    
198     6. A Windows user reported a minor discrepancy with test 2, which turned out
199        to be caused by a trailing space on an input line that had got lost in his
200        copy. The trailing space was an accident, so I've just removed it.
201    
202     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
203        that is needed.
204    
205     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
206        as "const" (a) because they are and (b) because it helps the PHP
207        maintainers who have recently made a script to detect big data structures
208        in the php code that should be moved to the .rodata section. I remembered
209        to update Builducptable as well, so it won't revert if ucptable.h is ever
210        re-created.
211    
212     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
213        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
214        order to be able to cut out the UTF-8 tables in the latter when UTF-8
215        support is not required. This saves 1.5-2K of code, which is important in
216        some applications.
217    
218        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
219        so as not to refer to the tables, even though these functions will never be
220        called when UTF-8 support is disabled. Otherwise there are problems with a
221        shared library.
222    
223    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
224    
225        (a) It was defining its arguments as char * instead of void *.
226    
227        (b) It was assuming that all moves were upwards in memory; this was true
228            a long time ago when I wrote it, but is no longer the case.
229    
230        The emulated memove() is provided for those environments that have neither
231        memmove() nor bcopy(). I didn't think anyone used it these days, but that
232        is clearly not the case, as these two bugs were recently reported.
233    
234    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
235        and Detrail to create the HTML documentation, the .txt form of the man
236        pages, and it removes trailing spaces from listed files. It also creates
237        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
238        case, it wraps all the #defines with #ifndefs. This script should be run
239        before "make dist".
240    
241    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
242        with Unicode property support.
243    
244        (a) For a maximizing quantifier, if the two different cases of the
245            character were of different lengths in their UTF-8 codings (there are
246            some cases like this - I found 11), and the matching function had to
247            back up over a mixture of the two cases, it incorrectly assumed they
248            were both the same length.
249    
250        (b) When PCRE was configured to use the heap rather than the stack for
251            recursion during matching, it was not correctly preserving the data for
252            the other case of a UTF-8 character when checking ahead for a match
253            while processing a minimizing repeat. If the check also involved
254            matching a wide character, but failed, corruption could cause an
255            erroneous result when trying to check for a repeat of the original
256            character.
257    
258    13. Some tidying changes to the testing mechanism:
259    
260        (a) The RunTest script now detects the internal link size and whether there
261            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
262            values substituted by "configure". (The RunGrepTest script already did
263            this for UTF-8.) The configure.ac script no longer substitutes the
264            relevant variables.
265    
266        (b) The debugging options /B and /D in pcretest show the compiled bytecode
267            with length and offset values. This means that the output is different
268            for different internal link sizes. Test 2 is skipped for link sizes
269            other than 2 because of this, bypassing the problem. Unfortunately,
270            there was also a test in test 3 (the locale tests) that used /B and
271            failed for link sizes other than 2. Rather than cut the whole test out,
272            I have added a new /Z option to pcretest that replaces the length and
273            offset values with spaces. This is now used to make test 3 independent
274            of link size. (Test 2 will be tidied up later.)
275    
276    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
277        segmentation fault instead of returning the appropriate error message.
278    
279    15. In multiline mode when the newline sequence was set to "any", the pattern
280        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
281        This doesn't seem right; it now treats the CRLF combination as the line
282        ending, and so does not match in that case. It's only a pattern such as ^$
283        that would hit this one: something like ^ABC$ would have failed after \r
284        and then tried again after \r\n.
285    
286    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
287        in an attempt to make files that differ only in their line terminators
288        compare equal. This works on Linux.
289    
290    17. Under certain error circumstances pcregrep might try to free random memory
291        as it exited. This is now fixed, thanks to valgrind.
292    
293    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
294        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
295        was because its rules for how to advance for /g after matching an empty
296        string at the end of a line did not allow for this case. They now check for
297        it specially.
298    
299    20. pcretest is supposed to handle patterns and data of any length, by
300        extending its buffers when necessary. It was getting this wrong when the
301        buffer for a data line had to be extended.
302    
303    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
304        CRLF as a newline sequence.
305    
306    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
307        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
308        I have nevertheless tidied it up.
309    
310    23. Added some casts to kill warnings from HP-UX ia64 compiler.
311    
312    24. Added a man page for pcre-config.
313    
314    
315    Version 7.0 19-Dec-06
316    ---------------------
317    
318     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
319        moving to gcc 4.1.1.
320    
321     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
322        sys/time.h, which is documented as needed for this function. It doesn't
323        seem to matter on Linux, but it showed up on some releases of OS X.
324    
325     3. It seems that there are systems where bytes whose values are greater than
326        127 match isprint() in the "C" locale. The "C" locale should be the
327        default when a C program starts up. In most systems, only ASCII printing
328        characters match isprint(). This difference caused the output from pcretest
329        to vary, making some of the tests fail. I have changed pcretest so that:
330    
331        (a) When it is outputting text in the compiled version of a pattern, bytes
332            other than 32-126 are always shown as hex escapes.
333    
334        (b) When it is outputting text that is a matched part of a subject string,
335            it does the same, unless a different locale has been set for the match
336            (using the /L modifier). In this case, it uses isprint() to decide.
337    
338     4. Fixed a major bug that caused incorrect computation of the amount of memory
339        required for a compiled pattern when options that changed within the
340        pattern affected the logic of the preliminary scan that determines the
341        length. The relevant options are -x, and -i in UTF-8 mode. The result was
342        that the computed length was too small. The symptoms of this bug were
343        either the PCRE error "internal error: code overflow" from pcre_compile(),
344        or a glibc crash with a message such as "pcretest: free(): invalid next
345        size (fast)". Examples of patterns that provoked this bug (shown in
346        pcretest format) are:
347    
348          /(?-x: )/x
349          /(?x)(?-x: \s*#\s*)/
350          /((?i)[\x{c0}])/8
351          /(?i:[\x{c0}])/8
352    
353        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
354        is now done differently.
355    
356     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
357        wrapper classes; (b) implement a new function in the C++ scanner that is
358        more efficient than the old way of doing things because it avoids levels of
359        recursion in the regex matching; (c) add a paragraph to the documentation
360        for the FullMatch() function.
361    
362     6. The escape sequence \n was being treated as whatever was defined as
363        "newline". Not only was this contrary to the documentation, which states
364        that \n is character 10 (hex 0A), but it also went horribly wrong when
365        "newline" was defined as CRLF. This has been fixed.
366    
367     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
368        was being set to -1 for the "end of line" case (supposedly a value that no
369        character can have). Though this value is never used (the check for end of
370        line is "zero bytes in current character"), it caused compiler complaints.
371        I've changed it to 0xffffffff.
372    
373     8. In pcre_version.c, the version string was being built by a sequence of
374        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
375        string (as it is for production releases) called a macro with an empty
376        argument. The C standard says the result of this is undefined. The gcc
377        compiler treats it as an empty string (which was what was wanted) but it is
378        reported that Visual C gives an error. The source has been hacked around to
379        avoid this problem.
380    
381     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
382        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
383        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
384        of them did).
385    
386    10. Originally, pcretest opened its input and output without "b"; then I was
387        told that "b" was needed in some environments, so it was added for release
388        5.0 to both the input and output. (It makes no difference on Unix-like
389        systems.) Later I was told that it is wrong for the input on Windows. I've
390        now abstracted the modes into two macros, to make it easier to fiddle with
391        them, and removed "b" from the input mode under Windows.
392    
393    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
394    
395    12. Added -help and --help to pcretest as an official way of being reminded
396        of the options.
397    
398    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
399        and pcrecpp.cc because they annoy compilers at high warning levels.
400    
401    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
402    
403    15. Fixed an occurrence of == in configure.ac that should have been = (shell
404        scripts are not C programs :-) and which was not noticed because it works
405        on Linux.
406    
407    16. pcretest is supposed to handle any length of pattern and data line (as one
408        line or as a continued sequence of lines) by extending its input buffer if
409        necessary. This feature was broken for very long pattern lines, leading to
410        a string of junk being passed to pcre_compile() if the pattern was longer
411        than about 50K.
412    
413    17. I have done a major re-factoring of the way pcre_compile() computes the
414        amount of memory needed for a compiled pattern. Previously, there was code
415        that made a preliminary scan of the pattern in order to do this. That was
416        OK when PCRE was new, but as the facilities have expanded, it has become
417        harder and harder to keep it in step with the real compile phase, and there
418        have been a number of bugs (see for example, 4 above). I have now found a
419        cunning way of running the real compile function in a "fake" mode that
420        enables it to compute how much memory it would need, while actually only
421        ever using a few hundred bytes of working memory and without too many
422        tests of the mode. This should make future maintenance and development
423        easier. A side effect of this work is that the limit of 200 on the nesting
424        depth of parentheses has been removed (though this was never a serious
425        limitation, I suspect). However, there is a downside: pcre_compile() now
426        runs more slowly than before (30% or more, depending on the pattern). I
427        hope this isn't a big issue. There is no effect on runtime performance.
428    
429    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
430        newline (only possible for the last line of a file) and it was a
431        pattern that set a locale (followed by /Lsomething), pcretest crashed.
432    
433    19. Added additional timing features to pcretest. (1) The -tm option now times
434        matching only, not compiling. (2) Both -t and -tm can be followed, as a
435        separate command line item, by a number that specifies the number of
436        repeats to use when timing. The default is 50000; this gives better
437        precision, but takes uncomfortably long for very large patterns.
438    
439    20. Extended pcre_study() to be more clever in cases where a branch of a
440        subpattern has no definite first character. For example, (a*|b*)[cd] would
441        previously give no result from pcre_study(). Now it recognizes that the
442        first character must be a, b, c, or d.
443    
444    21. There was an incorrect error "recursive call could loop indefinitely" if
445        a subpattern (or the entire pattern) that was being tested for matching an
446        empty string contained only one non-empty item after a nested subpattern.
447        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
448        incorrectly, because the \d was being skipped in the check.
449    
450    22. The pcretest program now has a new pattern option /B and a command line
451        option -b, which is equivalent to adding /B to every pattern. This causes
452        it to show the compiled bytecode, without the additional information that
453        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
454        is the same as /B/I).
455    
456    23. A new optimization is now able automatically to treat some sequences such
457        as a*b as a*+b. More specifically, if something simple (such as a character
458        or a simple class like \d) has an unlimited quantifier, and is followed by
459        something that cannot possibly match the quantified thing, the quantifier
460        is automatically "possessified".
461    
462    24. A recursive reference to a subpattern whose number was greater than 39
463        went wrong under certain circumstances in UTF-8 mode. This bug could also
464        have affected the operation of pcre_study().
465    
466    25. Realized that a little bit of performance could be had by replacing
467        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
468    
469    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
470    
471    27. Possessive quantifiers such as a++ were previously implemented by turning
472        them into atomic groups such as ($>a+). Now they have their own opcodes,
473        which improves performance. This includes the automatically created ones
474        from 23 above.
475    
476    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
477        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
478        the first matched character to be a colon. This applied both to named and
479        numbered groups.
480    
481    29. The ucpinternal.h header file was missing its idempotency #ifdef.
482    
483    30. I was sent a "project" file called libpcre.a.dev which I understand makes
484        building PCRE on Windows easier, so I have included it in the distribution.
485    
486    31. There is now a check in pcretest against a ridiculously large number being
487        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
488        loop, the loop is abandoned.
489    
490    32. Forward references to subpatterns in conditions such as (?(2)...) where
491        subpattern 2 is defined later cause pcre_compile() to search forwards in
492        the pattern for the relevant set of parentheses. This search went wrong
493        when there were unescaped parentheses in a character class, parentheses
494        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
495    
496    33. "Subroutine" calls and backreferences were previously restricted to
497        referencing subpatterns earlier in the regex. This restriction has now
498        been removed.
499    
500    34. Added a number of extra features that are going to be in Perl 5.10. On the
501        whole, these are just syntactic alternatives for features that PCRE had
502        previously implemented using the Python syntax or my own invention. The
503        other formats are all retained for compatibility.
504    
505        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
506            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
507            also .NET compatible.
508    
509        (b) A recursion or subroutine call to a named group can now be defined as
510            (?&name) as well as (?P>name).
511    
512        (c) A backreference to a named group can now be defined as \k<name> or
513            \k'name' as well as (?P=name). The new forms, as well as being in Perl
514            5.10, are also .NET compatible.
515    
516        (d) A conditional reference to a named group can now use the syntax
517            (?(<name>) or (?('name') as well as (?(name).
518    
519        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
520            groups (named and numbered) that are never evaluated inline, but can be
521            called as "subroutines" from elsewhere. In effect, the DEFINE condition
522            is always false. There may be only one alternative in such a group.
523    
524        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
525            as the simple (?(R). The condition is true only if the most recent
526            recursion is that of the given number or name. It does not search out
527            through the entire recursion stack.
528    
529        (g) The escape \gN or \g{N} has been added, where N is a positive or
530            negative number, specifying an absolute or relative reference.
531    
532    35. Tidied to get rid of some further signed/unsigned compiler warnings and
533        some "unreachable code" warnings.
534    
535    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
536        things, this adds five new scripts.
537    
538    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
539        There were also incompatibilities regarding the handling of \Q..\E inside
540        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
541        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
542    
543    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
544        matches an empty string, and forcibly breaks the loop. There were bugs in
545        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
546        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
547        separate and independent bugs (that affected different cases) have been
548        fixed.
549    
550    39. Refactored the code to abolish the use of different opcodes for small
551        capturing bracket numbers. This is a tidy that I avoided doing when I
552        removed the limit on the number of capturing brackets for 3.5 back in 2001.
553        The new approach is not only tidier, it makes it possible to reduce the
554        memory needed to fix the previous bug (38).
555    
556    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
557        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
558        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
559        mode.
560    
561    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
562        report.
563    
564    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
565        copy construction and assignment in the C++ wrapper.
566    
567    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
568        couple of bugs that could have given wrong results in the "--newline=crlf"
569        case.
570    
571    44. Added a number of casts and did some reorganization of signed/unsigned int
572        variables following suggestions from Dair Grant. Also renamed the variable
573        "this" as "item" because it is a C++ keyword.
574    
575    45. Arranged for dftables to add
576    
577          #include "pcre_internal.h"
578    
579        to pcre_chartables.c because without it, gcc 4.x may remove the array
580        definition from the final binary if PCRE is built into a static library and
581        dead code stripping is activated.
582    
583    46. For an unanchored pattern, if a match attempt fails at the start of a
584        newline sequence, and the newline setting is CRLF or ANY, and the next two
585        characters are CRLF, advance by two characters instead of one.
586    
587    
588    Version 6.7 04-Jul-06
589    ---------------------
590    
591     1. In order to handle tests when input lines are enormously long, pcretest has
592        been re-factored so that it automatically extends its buffers when
593        necessary. The code is crude, but this _is_ just a test program. The
594        default size has been increased from 32K to 50K.
595    
596     2. The code in pcre_study() was using the value of the re argument before
597        testing it for NULL. (Of course, in any sensible call of the function, it
598        won't be NULL.)
599    
600     3. The memmove() emulation function in pcre_internal.h, which is used on
601        systems that lack both memmove() and bcopy() - that is, hardly ever -
602        was missing a "static" storage class specifier.
603    
604     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
605        containing an extended class (one that cannot be represented by a bitmap
606        because it contains high-valued characters or Unicode property items, e.g.
607        [\pZ]). Almost always one would set UTF-8 mode when processing such a
608        pattern, but PCRE should not loop if you do not (it no longer does).
609        [Detail: two cases were found: (a) a repeated subpattern containing an
610        extended class; (b) a recursive reference to a subpattern that followed a
611        previous extended class. It wasn't skipping over the extended class
612        correctly when UTF-8 mode was not set.]
613    
614     5. A negated single-character class was not being recognized as fixed-length
615        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
616        compile error "lookbehind assertion is not fixed length".
617    
618     6. The RunPerlTest auxiliary script was showing an unexpected difference
619        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
620        write a Perl script that can interpret lines of an input file either as
621        byte characters or as UTF-8, which is what "perltest" was being required to
622        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
623        can't do is switch easily at run time between having the "use utf8;" pragma
624        or not. In the end, I fudged it by using the RunPerlTest script to insert
625        "use utf8;" explicitly for the UTF-8 tests.
626    
627     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
628        the end of the subject string, contrary to the documentation and to what
629        Perl does. This was true of both matching functions. Now it matches only at
630        the start of the subject and immediately after *internal* newlines.
631    
632     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
633        a pointer to an int instead of a pointer to an unsigned long int. This
634        caused problems on 64-bit systems.
635    
636     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
637        instance of the 'standard' template library not being so standard".
638    
639    10. There was no check on the number of named subpatterns nor the maximum
640        length of a subpattern name. The product of these values is used to compute
641        the size of the memory block for a compiled pattern. By supplying a very
642        long subpattern name and a large number of named subpatterns, the size
643        computation could be caused to overflow. This is now prevented by limiting
644        the length of names to 32 characters, and the number of named subpatterns
645        to 10,000.
646    
647    11. Subpatterns that are repeated with specific counts have to be replicated in
648        the compiled pattern. The size of memory for this was computed from the
649        length of the subpattern and the repeat count. The latter is limited to
650        65535, but there was no limit on the former, meaning that integer overflow
651        could in principle occur. The compiled length of a repeated subpattern is
652        now limited to 30,000 bytes in order to prevent this.
653    
654    12. Added the optional facility to have named substrings with the same name.
655    
656    13. Added the ability to use a named substring as a condition, using the
657        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
658        are numbers (not recommended). Forward references are permitted.
659    
660    14. Added forward references in named backreferences (if you see what I mean).
661    
662    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
663        pattern could run off the end of the subject. For example, the pattern
664        "(?s)(.{1,5})"8 did this with the subject "ab".
665    
666    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
667        PCRE_CASELESS was set when matching characters that were quantified with ?
668        or *.
669    
670    17. A character class other than a single negated character that had a minimum
671        but no maximum quantifier - for example [ab]{6,} - was not handled
672        correctly by pce_dfa_exec(). It would match only one character.
673    
674    18. A valid (though odd) pattern that looked like a POSIX character
675        class but used an invalid character after [ (for example [[,abc,]]) caused
676        pcre_compile() to give the error "Failed: internal error: code overflow" or
677        in some cases to crash with a glibc free() error. This could even happen if
678        the pattern terminated after [[ but there just happened to be a sequence of
679        letters, a binary zero, and a closing ] in the memory that followed.
680    
681    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
682        over the years. Originally (before any Unicode support), just the bottom 8
683        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
684        output from "man perlunicode" includes this:
685    
686          The regular expression compiler produces polymorphic opcodes.  That
687          is, the pattern adapts to the data and automatically switches to
688          the Unicode character scheme when presented with Unicode data--or
689          instead uses a traditional byte scheme when presented with byte
690          data.
691    
692        Sadly, a wide octal escape does not cause a switch, and in a string with
693        no other multibyte characters, these octal escapes are treated as before.
694        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
695        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
696        Unicode string.
697    
698        I have not perpetrated such confusion in PCRE. Up till now, it took just
699        the bottom 8 bits, as in old Perl. I have now made octal escapes with
700        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
701        translate to the appropriate multibyte character.
702    
703    29. Applied some refactoring to reduce the number of warnings from Microsoft
704        and Borland compilers. This has included removing the fudge introduced
705        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
706        a warning about an unused variable.
707    
708    21. PCRE has not included VT (character 0x0b) in the set of whitespace
709        characters since release 4.0, because Perl (from release 5.004) does not.
710        [Or at least, is documented not to: some releases seem to be in conflict
711        with the documentation.] However, when a pattern was studied with
712        pcre_study() and all its branches started with \s, PCRE still included VT
713        as a possible starting character. Of course, this did no harm; it just
714        caused an unnecessary match attempt.
715    
716    22. Removed a now-redundant internal flag bit that recorded the fact that case
717        dependency changed within the pattern. This was once needed for "required
718        byte" processing, but is no longer used. This recovers a now-scarce options
719        bit. Also moved the least significant internal flag bit to the most-
720        significant bit of the word, which was not previously used (hangover from
721        the days when it was an int rather than a uint) to free up another bit for
722        the future.
723    
724    23. Added support for CRLF line endings as well as CR and LF. As well as the
725        default being selectable at build time, it can now be changed at runtime
726        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
727        specify that it is scanning data with non-default line endings.
728    
729    24. Changed the definition of CXXLINK to make it agree with the definition of
730        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
731    
732    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
733        recursions. This makes a big different to stack usage for some patterns.
734    
735    26. If a subpattern containing a named recursion or subroutine reference such
736        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
737        the space required for the compiled pattern went wrong and gave too small a
738        value. Depending on the environment, this could lead to "Failed: internal
739        error: code overflow at offset 49" or "glibc detected double free or
740        corruption" errors.
741    
742    27. Applied patches from Google (a) to support the new newline modes and (b) to
743        advance over multibyte UTF-8 characters in GlobalReplace.
744    
745    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
746        difference for some implementation of PCRE in some Windows version.
747    
748    29. Added some extra testing facilities to pcretest:
749    
750        \q<number>   in a data line sets the "match limit" value
751        \Q<number>   in a data line sets the "match recursion limt" value
752        -S <number>  sets the stack size, where <number> is in megabytes
753    
754        The -S option isn't available for Windows.
755    
756    
757    Version 6.6 06-Feb-06
758    ---------------------
759    
760     1. Change 16(a) for 6.5 broke things, because PCRE_DATA_SCOPE was not defined
761        in pcreposix.h. I have copied the definition from pcre.h.
762    
763     2. Change 25 for 6.5 broke compilation in a build directory out-of-tree
764        because pcre.h is no longer a built file.
765    
766     3. Added Jeff Friedl's additional debugging patches to pcregrep. These are
767        not normally included in the compiled code.
768    
769    
770  Version 6.5 01-Feb-06  Version 6.5 01-Feb-06
771  ---------------------  ---------------------
772    

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