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revision 89 by nigel, Sat Feb 24 21:41:27 2007 UTC revision 206 by ph10, Fri Aug 3 14:53:04 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    
88    Version 7.2 19-Jun-07
89    ---------------------
90    
91     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
92        which is apparently normally available under Windows.
93    
94     2. Re-jig the pcregrep tests with different newline settings in an attempt
95        to make them independent of the local environment's newline setting.
96    
97     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
98    
99     4. Some of the "internals" tests were previously cut out when the link size
100        was not 2, because the output contained actual offsets. The recent new
101        "Z" feature of pcretest means that these can be cut out, making the tests
102        usable with all link sizes.
103    
104     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
105        stack recursion. This gives a massive performance boost under BSD, but just
106        a small improvement under Linux. However, it saves one field in the frame
107        in all cases.
108    
109     6. Added more features from the forthcoming Perl 5.10:
110    
111        (a) (?-n) (where n is a string of digits) is a relative subroutine or
112            recursion call. It refers to the nth most recently opened parentheses.
113    
114        (b) (?+n) is also a relative subroutine call; it refers to the nth next
115            to be opened parentheses.
116    
117        (c) Conditions that refer to capturing parentheses can be specified
118            relatively, for example, (?(-2)... or (?(+3)...
119    
120        (d) \K resets the start of the current match so that everything before
121            is not part of it.
122    
123        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
124    
125        (f) \g{name} is another synonym - part of Perl 5.10's unification of
126            reference syntax.
127    
128        (g) (?| introduces a group in which the numbering of parentheses in each
129            alternative starts with the same number.
130    
131        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
132    
133     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
134        PCRE_INFO_JCHANGED.
135    
136     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
137        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
138        for detecting groups that can match an empty string.
139    
140     9. A pattern with a very large number of alternatives (more than several
141        hundred) was running out of internal workspace during the pre-compile
142        phase, where pcre_compile() figures out how much memory will be needed. A
143        bit of new cunning has reduced the workspace needed for groups with
144        alternatives. The 1000-alternative test pattern now uses 12 bytes of
145        workspace instead of running out of the 4096 that are available.
146    
147    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
148    
149    11. Applied patch from Google to remove an optimization that didn't quite work.
150        The report of the bug said:
151    
152          pcrecpp::RE("a*").FullMatch("aaa") matches, while
153          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
154          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
155    
156    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
157        it matched the wrong number of bytes.
158    
159    
160    Version 7.1 24-Apr-07
161    ---------------------
162    
163     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
164        that is more "standard", making use of automake and other Autotools. There
165        is some re-arrangement of the files and adjustment of comments consequent
166        on this.
167    
168     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
169        for recursive directory scanning broke on some systems because the files
170        are not scanned in any specific order and on different systems the order
171        was different. A call to "sort" has been inserted into RunGrepTest for the
172        approprate test as a short-term fix. In the longer term there may be an
173        alternative.
174    
175     3. I had an email from Eric Raymond about problems translating some of PCRE's
176        man pages to HTML (despite the fact that I distribute HTML pages, some
177        people do their own conversions for various reasons). The problems
178        concerned the use of low-level troff macros .br and .in. I have therefore
179        removed all such uses from the man pages (some were redundant, some could
180        be replaced by .nf/.fi pairs). The 132html script that I use to generate
181        HTML has been updated to handle .nf/.fi and to complain if it encounters
182        .br or .in.
183    
184     4. Updated comments in configure.ac that get placed in config.h.in and also
185        arranged for config.h to be included in the distribution, with the name
186        config.h.generic, for the benefit of those who have to compile without
187        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
188    
189     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
190        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
191        makevp.bat for the current PCRE, using the additional files
192        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
193    
194     6. A Windows user reported a minor discrepancy with test 2, which turned out
195        to be caused by a trailing space on an input line that had got lost in his
196        copy. The trailing space was an accident, so I've just removed it.
197    
198     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
199        that is needed.
200    
201     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
202        as "const" (a) because they are and (b) because it helps the PHP
203        maintainers who have recently made a script to detect big data structures
204        in the php code that should be moved to the .rodata section. I remembered
205        to update Builducptable as well, so it won't revert if ucptable.h is ever
206        re-created.
207    
208     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
209        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
210        order to be able to cut out the UTF-8 tables in the latter when UTF-8
211        support is not required. This saves 1.5-2K of code, which is important in
212        some applications.
213    
214        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
215        so as not to refer to the tables, even though these functions will never be
216        called when UTF-8 support is disabled. Otherwise there are problems with a
217        shared library.
218    
219    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
220    
221        (a) It was defining its arguments as char * instead of void *.
222    
223        (b) It was assuming that all moves were upwards in memory; this was true
224            a long time ago when I wrote it, but is no longer the case.
225    
226        The emulated memove() is provided for those environments that have neither
227        memmove() nor bcopy(). I didn't think anyone used it these days, but that
228        is clearly not the case, as these two bugs were recently reported.
229    
230    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
231        and Detrail to create the HTML documentation, the .txt form of the man
232        pages, and it removes trailing spaces from listed files. It also creates
233        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
234        case, it wraps all the #defines with #ifndefs. This script should be run
235        before "make dist".
236    
237    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
238        with Unicode property support.
239    
240        (a) For a maximizing quantifier, if the two different cases of the
241            character were of different lengths in their UTF-8 codings (there are
242            some cases like this - I found 11), and the matching function had to
243            back up over a mixture of the two cases, it incorrectly assumed they
244            were both the same length.
245    
246        (b) When PCRE was configured to use the heap rather than the stack for
247            recursion during matching, it was not correctly preserving the data for
248            the other case of a UTF-8 character when checking ahead for a match
249            while processing a minimizing repeat. If the check also involved
250            matching a wide character, but failed, corruption could cause an
251            erroneous result when trying to check for a repeat of the original
252            character.
253    
254    13. Some tidying changes to the testing mechanism:
255    
256        (a) The RunTest script now detects the internal link size and whether there
257            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
258            values substituted by "configure". (The RunGrepTest script already did
259            this for UTF-8.) The configure.ac script no longer substitutes the
260            relevant variables.
261    
262        (b) The debugging options /B and /D in pcretest show the compiled bytecode
263            with length and offset values. This means that the output is different
264            for different internal link sizes. Test 2 is skipped for link sizes
265            other than 2 because of this, bypassing the problem. Unfortunately,
266            there was also a test in test 3 (the locale tests) that used /B and
267            failed for link sizes other than 2. Rather than cut the whole test out,
268            I have added a new /Z option to pcretest that replaces the length and
269            offset values with spaces. This is now used to make test 3 independent
270            of link size. (Test 2 will be tidied up later.)
271    
272    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
273        segmentation fault instead of returning the appropriate error message.
274    
275    15. In multiline mode when the newline sequence was set to "any", the pattern
276        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
277        This doesn't seem right; it now treats the CRLF combination as the line
278        ending, and so does not match in that case. It's only a pattern such as ^$
279        that would hit this one: something like ^ABC$ would have failed after \r
280        and then tried again after \r\n.
281    
282    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
283        in an attempt to make files that differ only in their line terminators
284        compare equal. This works on Linux.
285    
286    17. Under certain error circumstances pcregrep might try to free random memory
287        as it exited. This is now fixed, thanks to valgrind.
288    
289    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
290        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
291        was because its rules for how to advance for /g after matching an empty
292        string at the end of a line did not allow for this case. They now check for
293        it specially.
294    
295    20. pcretest is supposed to handle patterns and data of any length, by
296        extending its buffers when necessary. It was getting this wrong when the
297        buffer for a data line had to be extended.
298    
299    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
300        CRLF as a newline sequence.
301    
302    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
303        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
304        I have nevertheless tidied it up.
305    
306    23. Added some casts to kill warnings from HP-UX ia64 compiler.
307    
308    24. Added a man page for pcre-config.
309    
310    
311    Version 7.0 19-Dec-06
312    ---------------------
313    
314     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
315        moving to gcc 4.1.1.
316    
317     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
318        sys/time.h, which is documented as needed for this function. It doesn't
319        seem to matter on Linux, but it showed up on some releases of OS X.
320    
321     3. It seems that there are systems where bytes whose values are greater than
322        127 match isprint() in the "C" locale. The "C" locale should be the
323        default when a C program starts up. In most systems, only ASCII printing
324        characters match isprint(). This difference caused the output from pcretest
325        to vary, making some of the tests fail. I have changed pcretest so that:
326    
327        (a) When it is outputting text in the compiled version of a pattern, bytes
328            other than 32-126 are always shown as hex escapes.
329    
330        (b) When it is outputting text that is a matched part of a subject string,
331            it does the same, unless a different locale has been set for the match
332            (using the /L modifier). In this case, it uses isprint() to decide.
333    
334     4. Fixed a major bug that caused incorrect computation of the amount of memory
335        required for a compiled pattern when options that changed within the
336        pattern affected the logic of the preliminary scan that determines the
337        length. The relevant options are -x, and -i in UTF-8 mode. The result was
338        that the computed length was too small. The symptoms of this bug were
339        either the PCRE error "internal error: code overflow" from pcre_compile(),
340        or a glibc crash with a message such as "pcretest: free(): invalid next
341        size (fast)". Examples of patterns that provoked this bug (shown in
342        pcretest format) are:
343    
344          /(?-x: )/x
345          /(?x)(?-x: \s*#\s*)/
346          /((?i)[\x{c0}])/8
347          /(?i:[\x{c0}])/8
348    
349        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
350        is now done differently.
351    
352     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
353        wrapper classes; (b) implement a new function in the C++ scanner that is
354        more efficient than the old way of doing things because it avoids levels of
355        recursion in the regex matching; (c) add a paragraph to the documentation
356        for the FullMatch() function.
357    
358     6. The escape sequence \n was being treated as whatever was defined as
359        "newline". Not only was this contrary to the documentation, which states
360        that \n is character 10 (hex 0A), but it also went horribly wrong when
361        "newline" was defined as CRLF. This has been fixed.
362    
363     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
364        was being set to -1 for the "end of line" case (supposedly a value that no
365        character can have). Though this value is never used (the check for end of
366        line is "zero bytes in current character"), it caused compiler complaints.
367        I've changed it to 0xffffffff.
368    
369     8. In pcre_version.c, the version string was being built by a sequence of
370        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
371        string (as it is for production releases) called a macro with an empty
372        argument. The C standard says the result of this is undefined. The gcc
373        compiler treats it as an empty string (which was what was wanted) but it is
374        reported that Visual C gives an error. The source has been hacked around to
375        avoid this problem.
376    
377     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
378        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
379        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
380        of them did).
381    
382    10. Originally, pcretest opened its input and output without "b"; then I was
383        told that "b" was needed in some environments, so it was added for release
384        5.0 to both the input and output. (It makes no difference on Unix-like
385        systems.) Later I was told that it is wrong for the input on Windows. I've
386        now abstracted the modes into two macros, to make it easier to fiddle with
387        them, and removed "b" from the input mode under Windows.
388    
389    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
390    
391    12. Added -help and --help to pcretest as an official way of being reminded
392        of the options.
393    
394    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
395        and pcrecpp.cc because they annoy compilers at high warning levels.
396    
397    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
398    
399    15. Fixed an occurrence of == in configure.ac that should have been = (shell
400        scripts are not C programs :-) and which was not noticed because it works
401        on Linux.
402    
403    16. pcretest is supposed to handle any length of pattern and data line (as one
404        line or as a continued sequence of lines) by extending its input buffer if
405        necessary. This feature was broken for very long pattern lines, leading to
406        a string of junk being passed to pcre_compile() if the pattern was longer
407        than about 50K.
408    
409    17. I have done a major re-factoring of the way pcre_compile() computes the
410        amount of memory needed for a compiled pattern. Previously, there was code
411        that made a preliminary scan of the pattern in order to do this. That was
412        OK when PCRE was new, but as the facilities have expanded, it has become
413        harder and harder to keep it in step with the real compile phase, and there
414        have been a number of bugs (see for example, 4 above). I have now found a
415        cunning way of running the real compile function in a "fake" mode that
416        enables it to compute how much memory it would need, while actually only
417        ever using a few hundred bytes of working memory and without too many
418        tests of the mode. This should make future maintenance and development
419        easier. A side effect of this work is that the limit of 200 on the nesting
420        depth of parentheses has been removed (though this was never a serious
421        limitation, I suspect). However, there is a downside: pcre_compile() now
422        runs more slowly than before (30% or more, depending on the pattern). I
423        hope this isn't a big issue. There is no effect on runtime performance.
424    
425    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
426        newline (only possible for the last line of a file) and it was a
427        pattern that set a locale (followed by /Lsomething), pcretest crashed.
428    
429    19. Added additional timing features to pcretest. (1) The -tm option now times
430        matching only, not compiling. (2) Both -t and -tm can be followed, as a
431        separate command line item, by a number that specifies the number of
432        repeats to use when timing. The default is 50000; this gives better
433        precision, but takes uncomfortably long for very large patterns.
434    
435    20. Extended pcre_study() to be more clever in cases where a branch of a
436        subpattern has no definite first character. For example, (a*|b*)[cd] would
437        previously give no result from pcre_study(). Now it recognizes that the
438        first character must be a, b, c, or d.
439    
440    21. There was an incorrect error "recursive call could loop indefinitely" if
441        a subpattern (or the entire pattern) that was being tested for matching an
442        empty string contained only one non-empty item after a nested subpattern.
443        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
444        incorrectly, because the \d was being skipped in the check.
445    
446    22. The pcretest program now has a new pattern option /B and a command line
447        option -b, which is equivalent to adding /B to every pattern. This causes
448        it to show the compiled bytecode, without the additional information that
449        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
450        is the same as /B/I).
451    
452    23. A new optimization is now able automatically to treat some sequences such
453        as a*b as a*+b. More specifically, if something simple (such as a character
454        or a simple class like \d) has an unlimited quantifier, and is followed by
455        something that cannot possibly match the quantified thing, the quantifier
456        is automatically "possessified".
457    
458    24. A recursive reference to a subpattern whose number was greater than 39
459        went wrong under certain circumstances in UTF-8 mode. This bug could also
460        have affected the operation of pcre_study().
461    
462    25. Realized that a little bit of performance could be had by replacing
463        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
464    
465    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
466    
467    27. Possessive quantifiers such as a++ were previously implemented by turning
468        them into atomic groups such as ($>a+). Now they have their own opcodes,
469        which improves performance. This includes the automatically created ones
470        from 23 above.
471    
472    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
473        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
474        the first matched character to be a colon. This applied both to named and
475        numbered groups.
476    
477    29. The ucpinternal.h header file was missing its idempotency #ifdef.
478    
479    30. I was sent a "project" file called libpcre.a.dev which I understand makes
480        building PCRE on Windows easier, so I have included it in the distribution.
481    
482    31. There is now a check in pcretest against a ridiculously large number being
483        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
484        loop, the loop is abandoned.
485    
486    32. Forward references to subpatterns in conditions such as (?(2)...) where
487        subpattern 2 is defined later cause pcre_compile() to search forwards in
488        the pattern for the relevant set of parentheses. This search went wrong
489        when there were unescaped parentheses in a character class, parentheses
490        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
491    
492    33. "Subroutine" calls and backreferences were previously restricted to
493        referencing subpatterns earlier in the regex. This restriction has now
494        been removed.
495    
496    34. Added a number of extra features that are going to be in Perl 5.10. On the
497        whole, these are just syntactic alternatives for features that PCRE had
498        previously implemented using the Python syntax or my own invention. The
499        other formats are all retained for compatibility.
500    
501        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
502            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
503            also .NET compatible.
504    
505        (b) A recursion or subroutine call to a named group can now be defined as
506            (?&name) as well as (?P>name).
507    
508        (c) A backreference to a named group can now be defined as \k<name> or
509            \k'name' as well as (?P=name). The new forms, as well as being in Perl
510            5.10, are also .NET compatible.
511    
512        (d) A conditional reference to a named group can now use the syntax
513            (?(<name>) or (?('name') as well as (?(name).
514    
515        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
516            groups (named and numbered) that are never evaluated inline, but can be
517            called as "subroutines" from elsewhere. In effect, the DEFINE condition
518            is always false. There may be only one alternative in such a group.
519    
520        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
521            as the simple (?(R). The condition is true only if the most recent
522            recursion is that of the given number or name. It does not search out
523            through the entire recursion stack.
524    
525        (g) The escape \gN or \g{N} has been added, where N is a positive or
526            negative number, specifying an absolute or relative reference.
527    
528    35. Tidied to get rid of some further signed/unsigned compiler warnings and
529        some "unreachable code" warnings.
530    
531    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
532        things, this adds five new scripts.
533    
534    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
535        There were also incompatibilities regarding the handling of \Q..\E inside
536        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
537        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
538    
539    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
540        matches an empty string, and forcibly breaks the loop. There were bugs in
541        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
542        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
543        separate and independent bugs (that affected different cases) have been
544        fixed.
545    
546    39. Refactored the code to abolish the use of different opcodes for small
547        capturing bracket numbers. This is a tidy that I avoided doing when I
548        removed the limit on the number of capturing brackets for 3.5 back in 2001.
549        The new approach is not only tidier, it makes it possible to reduce the
550        memory needed to fix the previous bug (38).
551    
552    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
553        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
554        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
555        mode.
556    
557    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
558        report.
559    
560    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
561        copy construction and assignment in the C++ wrapper.
562    
563    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
564        couple of bugs that could have given wrong results in the "--newline=crlf"
565        case.
566    
567    44. Added a number of casts and did some reorganization of signed/unsigned int
568        variables following suggestions from Dair Grant. Also renamed the variable
569        "this" as "item" because it is a C++ keyword.
570    
571    45. Arranged for dftables to add
572    
573          #include "pcre_internal.h"
574    
575        to pcre_chartables.c because without it, gcc 4.x may remove the array
576        definition from the final binary if PCRE is built into a static library and
577        dead code stripping is activated.
578    
579    46. For an unanchored pattern, if a match attempt fails at the start of a
580        newline sequence, and the newline setting is CRLF or ANY, and the next two
581        characters are CRLF, advance by two characters instead of one.
582    
583    
584    Version 6.7 04-Jul-06
585    ---------------------
586    
587     1. In order to handle tests when input lines are enormously long, pcretest has
588        been re-factored so that it automatically extends its buffers when
589        necessary. The code is crude, but this _is_ just a test program. The
590        default size has been increased from 32K to 50K.
591    
592     2. The code in pcre_study() was using the value of the re argument before
593        testing it for NULL. (Of course, in any sensible call of the function, it
594        won't be NULL.)
595    
596     3. The memmove() emulation function in pcre_internal.h, which is used on
597        systems that lack both memmove() and bcopy() - that is, hardly ever -
598        was missing a "static" storage class specifier.
599    
600     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
601        containing an extended class (one that cannot be represented by a bitmap
602        because it contains high-valued characters or Unicode property items, e.g.
603        [\pZ]). Almost always one would set UTF-8 mode when processing such a
604        pattern, but PCRE should not loop if you do not (it no longer does).
605        [Detail: two cases were found: (a) a repeated subpattern containing an
606        extended class; (b) a recursive reference to a subpattern that followed a
607        previous extended class. It wasn't skipping over the extended class
608        correctly when UTF-8 mode was not set.]
609    
610     5. A negated single-character class was not being recognized as fixed-length
611        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
612        compile error "lookbehind assertion is not fixed length".
613    
614     6. The RunPerlTest auxiliary script was showing an unexpected difference
615        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
616        write a Perl script that can interpret lines of an input file either as
617        byte characters or as UTF-8, which is what "perltest" was being required to
618        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
619        can't do is switch easily at run time between having the "use utf8;" pragma
620        or not. In the end, I fudged it by using the RunPerlTest script to insert
621        "use utf8;" explicitly for the UTF-8 tests.
622    
623     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
624        the end of the subject string, contrary to the documentation and to what
625        Perl does. This was true of both matching functions. Now it matches only at
626        the start of the subject and immediately after *internal* newlines.
627    
628     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
629        a pointer to an int instead of a pointer to an unsigned long int. This
630        caused problems on 64-bit systems.
631    
632     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
633        instance of the 'standard' template library not being so standard".
634    
635    10. There was no check on the number of named subpatterns nor the maximum
636        length of a subpattern name. The product of these values is used to compute
637        the size of the memory block for a compiled pattern. By supplying a very
638        long subpattern name and a large number of named subpatterns, the size
639        computation could be caused to overflow. This is now prevented by limiting
640        the length of names to 32 characters, and the number of named subpatterns
641        to 10,000.
642    
643    11. Subpatterns that are repeated with specific counts have to be replicated in
644        the compiled pattern. The size of memory for this was computed from the
645        length of the subpattern and the repeat count. The latter is limited to
646        65535, but there was no limit on the former, meaning that integer overflow
647        could in principle occur. The compiled length of a repeated subpattern is
648        now limited to 30,000 bytes in order to prevent this.
649    
650    12. Added the optional facility to have named substrings with the same name.
651    
652    13. Added the ability to use a named substring as a condition, using the
653        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
654        are numbers (not recommended). Forward references are permitted.
655    
656    14. Added forward references in named backreferences (if you see what I mean).
657    
658    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
659        pattern could run off the end of the subject. For example, the pattern
660        "(?s)(.{1,5})"8 did this with the subject "ab".
661    
662    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
663        PCRE_CASELESS was set when matching characters that were quantified with ?
664        or *.
665    
666    17. A character class other than a single negated character that had a minimum
667        but no maximum quantifier - for example [ab]{6,} - was not handled
668        correctly by pce_dfa_exec(). It would match only one character.
669    
670    18. A valid (though odd) pattern that looked like a POSIX character
671        class but used an invalid character after [ (for example [[,abc,]]) caused
672        pcre_compile() to give the error "Failed: internal error: code overflow" or
673        in some cases to crash with a glibc free() error. This could even happen if
674        the pattern terminated after [[ but there just happened to be a sequence of
675        letters, a binary zero, and a closing ] in the memory that followed.
676    
677    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
678        over the years. Originally (before any Unicode support), just the bottom 8
679        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
680        output from "man perlunicode" includes this:
681    
682          The regular expression compiler produces polymorphic opcodes.  That
683          is, the pattern adapts to the data and automatically switches to
684          the Unicode character scheme when presented with Unicode data--or
685          instead uses a traditional byte scheme when presented with byte
686          data.
687    
688        Sadly, a wide octal escape does not cause a switch, and in a string with
689        no other multibyte characters, these octal escapes are treated as before.
690        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
691        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
692        Unicode string.
693    
694        I have not perpetrated such confusion in PCRE. Up till now, it took just
695        the bottom 8 bits, as in old Perl. I have now made octal escapes with
696        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
697        translate to the appropriate multibyte character.
698    
699    29. Applied some refactoring to reduce the number of warnings from Microsoft
700        and Borland compilers. This has included removing the fudge introduced
701        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
702        a warning about an unused variable.
703    
704    21. PCRE has not included VT (character 0x0b) in the set of whitespace
705        characters since release 4.0, because Perl (from release 5.004) does not.
706        [Or at least, is documented not to: some releases seem to be in conflict
707        with the documentation.] However, when a pattern was studied with
708        pcre_study() and all its branches started with \s, PCRE still included VT
709        as a possible starting character. Of course, this did no harm; it just
710        caused an unnecessary match attempt.
711    
712    22. Removed a now-redundant internal flag bit that recorded the fact that case
713        dependency changed within the pattern. This was once needed for "required
714        byte" processing, but is no longer used. This recovers a now-scarce options
715        bit. Also moved the least significant internal flag bit to the most-
716        significant bit of the word, which was not previously used (hangover from
717        the days when it was an int rather than a uint) to free up another bit for
718        the future.
719    
720    23. Added support for CRLF line endings as well as CR and LF. As well as the
721        default being selectable at build time, it can now be changed at runtime
722        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
723        specify that it is scanning data with non-default line endings.
724    
725    24. Changed the definition of CXXLINK to make it agree with the definition of
726        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
727    
728    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
729        recursions. This makes a big different to stack usage for some patterns.
730    
731    26. If a subpattern containing a named recursion or subroutine reference such
732        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
733        the space required for the compiled pattern went wrong and gave too small a
734        value. Depending on the environment, this could lead to "Failed: internal
735        error: code overflow at offset 49" or "glibc detected double free or
736        corruption" errors.
737    
738    27. Applied patches from Google (a) to support the new newline modes and (b) to
739        advance over multibyte UTF-8 characters in GlobalReplace.
740    
741    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
742        difference for some implementation of PCRE in some Windows version.
743    
744    29. Added some extra testing facilities to pcretest:
745    
746        \q<number>   in a data line sets the "match limit" value
747        \Q<number>   in a data line sets the "match recursion limt" value
748        -S <number>  sets the stack size, where <number> is in megabytes
749    
750        The -S option isn't available for Windows.
751    
752    
753  Version 6.6 06-Feb-06  Version 6.6 06-Feb-06
754  ---------------------  ---------------------
755    

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