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revision 89 by nigel, Sat Feb 24 21:41:27 2007 UTC revision 224 by ph10, Mon Aug 20 12:58:29 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4    Version 7.3 20-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    16. Inserted checks for integer overflows during escape sequence (backslash)
103        processing, and also fixed erroneous offset values for syntax errors during
104        backslash processing.
105    
106    17. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
107        for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
108    
109    18. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
110        caused an overrun.
111    
112    19. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
113        something other than just ASCII characters) inside a group that had an
114        unlimited repeat caused a loop at compile time (while checking to see
115        whether the group could match an empty string).
116    
117    20. Debugging a pattern containing \p or \P could cause a crash. For example,
118        [\P{Any}] did so. (Error in the code for printing property names.)
119    
120    21. An orphan \E inside a character class could cause a crash.
121    
122    22. A repeated capturing bracket such as (A)? could cause a wild memory
123        reference during compilation.
124    
125    23. There are several functions in pcre_compile() that scan along a compiled
126        expression for various reasons (e.g. to see if it's fixed length for look
127        behind). There were bugs in these functions when a repeated \p or \P was
128        present in the pattern. These operators have additional parameters compared
129        with \d, etc, and these were not being taken into account when moving along
130        the compiled data. Specifically:
131    
132        (a) A item such as \p{Yi}{3} in a lookbehind was not treated as fixed
133            length.
134    
135        (b) An item such as \pL+ within a repeated group could cause crashes or
136            loops.
137    
138        (c) A pattern such as \p{Yi}+(\P{Yi}+)(?1) could give an incorrect
139            "reference to non-existent subpattern" error.
140    
141        (d) A pattern like (\P{Yi}{2}\277)? could loop at compile time.
142    
143    24. A repeated \S or \W in UTF-8 mode could give wrong answers when multibyte
144        characters were involved (for example /\S{2}/8g with "A\x{a3}BC").
145    
146    25. Using pcregrep in multiline, inverted mode (-Mv) caused it to loop.
147    
148    26. Patterns such as [\P{Yi}A] which include \p or \P and just one other
149        character were causing crashes (broken optimization).
150    
151    27. Patterns such as (\P{Yi}*\277)* (group with possible zero repeat containing
152        \p or \P) caused a compile-time loop.
153    
154    
155    Version 7.2 19-Jun-07
156    ---------------------
157    
158     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
159        which is apparently normally available under Windows.
160    
161     2. Re-jig the pcregrep tests with different newline settings in an attempt
162        to make them independent of the local environment's newline setting.
163    
164     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
165    
166     4. Some of the "internals" tests were previously cut out when the link size
167        was not 2, because the output contained actual offsets. The recent new
168        "Z" feature of pcretest means that these can be cut out, making the tests
169        usable with all link sizes.
170    
171     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
172        stack recursion. This gives a massive performance boost under BSD, but just
173        a small improvement under Linux. However, it saves one field in the frame
174        in all cases.
175    
176     6. Added more features from the forthcoming Perl 5.10:
177    
178        (a) (?-n) (where n is a string of digits) is a relative subroutine or
179            recursion call. It refers to the nth most recently opened parentheses.
180    
181        (b) (?+n) is also a relative subroutine call; it refers to the nth next
182            to be opened parentheses.
183    
184        (c) Conditions that refer to capturing parentheses can be specified
185            relatively, for example, (?(-2)... or (?(+3)...
186    
187        (d) \K resets the start of the current match so that everything before
188            is not part of it.
189    
190        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
191    
192        (f) \g{name} is another synonym - part of Perl 5.10's unification of
193            reference syntax.
194    
195        (g) (?| introduces a group in which the numbering of parentheses in each
196            alternative starts with the same number.
197    
198        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
199    
200     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
201        PCRE_INFO_JCHANGED.
202    
203     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
204        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
205        for detecting groups that can match an empty string.
206    
207     9. A pattern with a very large number of alternatives (more than several
208        hundred) was running out of internal workspace during the pre-compile
209        phase, where pcre_compile() figures out how much memory will be needed. A
210        bit of new cunning has reduced the workspace needed for groups with
211        alternatives. The 1000-alternative test pattern now uses 12 bytes of
212        workspace instead of running out of the 4096 that are available.
213    
214    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
215    
216    11. Applied patch from Google to remove an optimization that didn't quite work.
217        The report of the bug said:
218    
219          pcrecpp::RE("a*").FullMatch("aaa") matches, while
220          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
221          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
222    
223    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
224        it matched the wrong number of bytes.
225    
226    
227    Version 7.1 24-Apr-07
228    ---------------------
229    
230     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
231        that is more "standard", making use of automake and other Autotools. There
232        is some re-arrangement of the files and adjustment of comments consequent
233        on this.
234    
235     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
236        for recursive directory scanning broke on some systems because the files
237        are not scanned in any specific order and on different systems the order
238        was different. A call to "sort" has been inserted into RunGrepTest for the
239        approprate test as a short-term fix. In the longer term there may be an
240        alternative.
241    
242     3. I had an email from Eric Raymond about problems translating some of PCRE's
243        man pages to HTML (despite the fact that I distribute HTML pages, some
244        people do their own conversions for various reasons). The problems
245        concerned the use of low-level troff macros .br and .in. I have therefore
246        removed all such uses from the man pages (some were redundant, some could
247        be replaced by .nf/.fi pairs). The 132html script that I use to generate
248        HTML has been updated to handle .nf/.fi and to complain if it encounters
249        .br or .in.
250    
251     4. Updated comments in configure.ac that get placed in config.h.in and also
252        arranged for config.h to be included in the distribution, with the name
253        config.h.generic, for the benefit of those who have to compile without
254        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
255    
256     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
257        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
258        makevp.bat for the current PCRE, using the additional files
259        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
260    
261     6. A Windows user reported a minor discrepancy with test 2, which turned out
262        to be caused by a trailing space on an input line that had got lost in his
263        copy. The trailing space was an accident, so I've just removed it.
264    
265     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
266        that is needed.
267    
268     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
269        as "const" (a) because they are and (b) because it helps the PHP
270        maintainers who have recently made a script to detect big data structures
271        in the php code that should be moved to the .rodata section. I remembered
272        to update Builducptable as well, so it won't revert if ucptable.h is ever
273        re-created.
274    
275     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
276        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
277        order to be able to cut out the UTF-8 tables in the latter when UTF-8
278        support is not required. This saves 1.5-2K of code, which is important in
279        some applications.
280    
281        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
282        so as not to refer to the tables, even though these functions will never be
283        called when UTF-8 support is disabled. Otherwise there are problems with a
284        shared library.
285    
286    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
287    
288        (a) It was defining its arguments as char * instead of void *.
289    
290        (b) It was assuming that all moves were upwards in memory; this was true
291            a long time ago when I wrote it, but is no longer the case.
292    
293        The emulated memove() is provided for those environments that have neither
294        memmove() nor bcopy(). I didn't think anyone used it these days, but that
295        is clearly not the case, as these two bugs were recently reported.
296    
297    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
298        and Detrail to create the HTML documentation, the .txt form of the man
299        pages, and it removes trailing spaces from listed files. It also creates
300        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
301        case, it wraps all the #defines with #ifndefs. This script should be run
302        before "make dist".
303    
304    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
305        with Unicode property support.
306    
307        (a) For a maximizing quantifier, if the two different cases of the
308            character were of different lengths in their UTF-8 codings (there are
309            some cases like this - I found 11), and the matching function had to
310            back up over a mixture of the two cases, it incorrectly assumed they
311            were both the same length.
312    
313        (b) When PCRE was configured to use the heap rather than the stack for
314            recursion during matching, it was not correctly preserving the data for
315            the other case of a UTF-8 character when checking ahead for a match
316            while processing a minimizing repeat. If the check also involved
317            matching a wide character, but failed, corruption could cause an
318            erroneous result when trying to check for a repeat of the original
319            character.
320    
321    13. Some tidying changes to the testing mechanism:
322    
323        (a) The RunTest script now detects the internal link size and whether there
324            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
325            values substituted by "configure". (The RunGrepTest script already did
326            this for UTF-8.) The configure.ac script no longer substitutes the
327            relevant variables.
328    
329        (b) The debugging options /B and /D in pcretest show the compiled bytecode
330            with length and offset values. This means that the output is different
331            for different internal link sizes. Test 2 is skipped for link sizes
332            other than 2 because of this, bypassing the problem. Unfortunately,
333            there was also a test in test 3 (the locale tests) that used /B and
334            failed for link sizes other than 2. Rather than cut the whole test out,
335            I have added a new /Z option to pcretest that replaces the length and
336            offset values with spaces. This is now used to make test 3 independent
337            of link size. (Test 2 will be tidied up later.)
338    
339    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
340        segmentation fault instead of returning the appropriate error message.
341    
342    15. In multiline mode when the newline sequence was set to "any", the pattern
343        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
344        This doesn't seem right; it now treats the CRLF combination as the line
345        ending, and so does not match in that case. It's only a pattern such as ^$
346        that would hit this one: something like ^ABC$ would have failed after \r
347        and then tried again after \r\n.
348    
349    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
350        in an attempt to make files that differ only in their line terminators
351        compare equal. This works on Linux.
352    
353    17. Under certain error circumstances pcregrep might try to free random memory
354        as it exited. This is now fixed, thanks to valgrind.
355    
356    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
357        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
358        was because its rules for how to advance for /g after matching an empty
359        string at the end of a line did not allow for this case. They now check for
360        it specially.
361    
362    20. pcretest is supposed to handle patterns and data of any length, by
363        extending its buffers when necessary. It was getting this wrong when the
364        buffer for a data line had to be extended.
365    
366    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
367        CRLF as a newline sequence.
368    
369    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
370        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
371        I have nevertheless tidied it up.
372    
373    23. Added some casts to kill warnings from HP-UX ia64 compiler.
374    
375    24. Added a man page for pcre-config.
376    
377    
378    Version 7.0 19-Dec-06
379    ---------------------
380    
381     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
382        moving to gcc 4.1.1.
383    
384     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
385        sys/time.h, which is documented as needed for this function. It doesn't
386        seem to matter on Linux, but it showed up on some releases of OS X.
387    
388     3. It seems that there are systems where bytes whose values are greater than
389        127 match isprint() in the "C" locale. The "C" locale should be the
390        default when a C program starts up. In most systems, only ASCII printing
391        characters match isprint(). This difference caused the output from pcretest
392        to vary, making some of the tests fail. I have changed pcretest so that:
393    
394        (a) When it is outputting text in the compiled version of a pattern, bytes
395            other than 32-126 are always shown as hex escapes.
396    
397        (b) When it is outputting text that is a matched part of a subject string,
398            it does the same, unless a different locale has been set for the match
399            (using the /L modifier). In this case, it uses isprint() to decide.
400    
401     4. Fixed a major bug that caused incorrect computation of the amount of memory
402        required for a compiled pattern when options that changed within the
403        pattern affected the logic of the preliminary scan that determines the
404        length. The relevant options are -x, and -i in UTF-8 mode. The result was
405        that the computed length was too small. The symptoms of this bug were
406        either the PCRE error "internal error: code overflow" from pcre_compile(),
407        or a glibc crash with a message such as "pcretest: free(): invalid next
408        size (fast)". Examples of patterns that provoked this bug (shown in
409        pcretest format) are:
410    
411          /(?-x: )/x
412          /(?x)(?-x: \s*#\s*)/
413          /((?i)[\x{c0}])/8
414          /(?i:[\x{c0}])/8
415    
416        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
417        is now done differently.
418    
419     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
420        wrapper classes; (b) implement a new function in the C++ scanner that is
421        more efficient than the old way of doing things because it avoids levels of
422        recursion in the regex matching; (c) add a paragraph to the documentation
423        for the FullMatch() function.
424    
425     6. The escape sequence \n was being treated as whatever was defined as
426        "newline". Not only was this contrary to the documentation, which states
427        that \n is character 10 (hex 0A), but it also went horribly wrong when
428        "newline" was defined as CRLF. This has been fixed.
429    
430     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
431        was being set to -1 for the "end of line" case (supposedly a value that no
432        character can have). Though this value is never used (the check for end of
433        line is "zero bytes in current character"), it caused compiler complaints.
434        I've changed it to 0xffffffff.
435    
436     8. In pcre_version.c, the version string was being built by a sequence of
437        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
438        string (as it is for production releases) called a macro with an empty
439        argument. The C standard says the result of this is undefined. The gcc
440        compiler treats it as an empty string (which was what was wanted) but it is
441        reported that Visual C gives an error. The source has been hacked around to
442        avoid this problem.
443    
444     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
445        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
446        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
447        of them did).
448    
449    10. Originally, pcretest opened its input and output without "b"; then I was
450        told that "b" was needed in some environments, so it was added for release
451        5.0 to both the input and output. (It makes no difference on Unix-like
452        systems.) Later I was told that it is wrong for the input on Windows. I've
453        now abstracted the modes into two macros, to make it easier to fiddle with
454        them, and removed "b" from the input mode under Windows.
455    
456    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
457    
458    12. Added -help and --help to pcretest as an official way of being reminded
459        of the options.
460    
461    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
462        and pcrecpp.cc because they annoy compilers at high warning levels.
463    
464    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
465    
466    15. Fixed an occurrence of == in configure.ac that should have been = (shell
467        scripts are not C programs :-) and which was not noticed because it works
468        on Linux.
469    
470    16. pcretest is supposed to handle any length of pattern and data line (as one
471        line or as a continued sequence of lines) by extending its input buffer if
472        necessary. This feature was broken for very long pattern lines, leading to
473        a string of junk being passed to pcre_compile() if the pattern was longer
474        than about 50K.
475    
476    17. I have done a major re-factoring of the way pcre_compile() computes the
477        amount of memory needed for a compiled pattern. Previously, there was code
478        that made a preliminary scan of the pattern in order to do this. That was
479        OK when PCRE was new, but as the facilities have expanded, it has become
480        harder and harder to keep it in step with the real compile phase, and there
481        have been a number of bugs (see for example, 4 above). I have now found a
482        cunning way of running the real compile function in a "fake" mode that
483        enables it to compute how much memory it would need, while actually only
484        ever using a few hundred bytes of working memory and without too many
485        tests of the mode. This should make future maintenance and development
486        easier. A side effect of this work is that the limit of 200 on the nesting
487        depth of parentheses has been removed (though this was never a serious
488        limitation, I suspect). However, there is a downside: pcre_compile() now
489        runs more slowly than before (30% or more, depending on the pattern). I
490        hope this isn't a big issue. There is no effect on runtime performance.
491    
492    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
493        newline (only possible for the last line of a file) and it was a
494        pattern that set a locale (followed by /Lsomething), pcretest crashed.
495    
496    19. Added additional timing features to pcretest. (1) The -tm option now times
497        matching only, not compiling. (2) Both -t and -tm can be followed, as a
498        separate command line item, by a number that specifies the number of
499        repeats to use when timing. The default is 50000; this gives better
500        precision, but takes uncomfortably long for very large patterns.
501    
502    20. Extended pcre_study() to be more clever in cases where a branch of a
503        subpattern has no definite first character. For example, (a*|b*)[cd] would
504        previously give no result from pcre_study(). Now it recognizes that the
505        first character must be a, b, c, or d.
506    
507    21. There was an incorrect error "recursive call could loop indefinitely" if
508        a subpattern (or the entire pattern) that was being tested for matching an
509        empty string contained only one non-empty item after a nested subpattern.
510        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
511        incorrectly, because the \d was being skipped in the check.
512    
513    22. The pcretest program now has a new pattern option /B and a command line
514        option -b, which is equivalent to adding /B to every pattern. This causes
515        it to show the compiled bytecode, without the additional information that
516        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
517        is the same as /B/I).
518    
519    23. A new optimization is now able automatically to treat some sequences such
520        as a*b as a*+b. More specifically, if something simple (such as a character
521        or a simple class like \d) has an unlimited quantifier, and is followed by
522        something that cannot possibly match the quantified thing, the quantifier
523        is automatically "possessified".
524    
525    24. A recursive reference to a subpattern whose number was greater than 39
526        went wrong under certain circumstances in UTF-8 mode. This bug could also
527        have affected the operation of pcre_study().
528    
529    25. Realized that a little bit of performance could be had by replacing
530        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
531    
532    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
533    
534    27. Possessive quantifiers such as a++ were previously implemented by turning
535        them into atomic groups such as ($>a+). Now they have their own opcodes,
536        which improves performance. This includes the automatically created ones
537        from 23 above.
538    
539    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
540        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
541        the first matched character to be a colon. This applied both to named and
542        numbered groups.
543    
544    29. The ucpinternal.h header file was missing its idempotency #ifdef.
545    
546    30. I was sent a "project" file called libpcre.a.dev which I understand makes
547        building PCRE on Windows easier, so I have included it in the distribution.
548    
549    31. There is now a check in pcretest against a ridiculously large number being
550        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
551        loop, the loop is abandoned.
552    
553    32. Forward references to subpatterns in conditions such as (?(2)...) where
554        subpattern 2 is defined later cause pcre_compile() to search forwards in
555        the pattern for the relevant set of parentheses. This search went wrong
556        when there were unescaped parentheses in a character class, parentheses
557        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
558    
559    33. "Subroutine" calls and backreferences were previously restricted to
560        referencing subpatterns earlier in the regex. This restriction has now
561        been removed.
562    
563    34. Added a number of extra features that are going to be in Perl 5.10. On the
564        whole, these are just syntactic alternatives for features that PCRE had
565        previously implemented using the Python syntax or my own invention. The
566        other formats are all retained for compatibility.
567    
568        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
569            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
570            also .NET compatible.
571    
572        (b) A recursion or subroutine call to a named group can now be defined as
573            (?&name) as well as (?P>name).
574    
575        (c) A backreference to a named group can now be defined as \k<name> or
576            \k'name' as well as (?P=name). The new forms, as well as being in Perl
577            5.10, are also .NET compatible.
578    
579        (d) A conditional reference to a named group can now use the syntax
580            (?(<name>) or (?('name') as well as (?(name).
581    
582        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
583            groups (named and numbered) that are never evaluated inline, but can be
584            called as "subroutines" from elsewhere. In effect, the DEFINE condition
585            is always false. There may be only one alternative in such a group.
586    
587        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
588            as the simple (?(R). The condition is true only if the most recent
589            recursion is that of the given number or name. It does not search out
590            through the entire recursion stack.
591    
592        (g) The escape \gN or \g{N} has been added, where N is a positive or
593            negative number, specifying an absolute or relative reference.
594    
595    35. Tidied to get rid of some further signed/unsigned compiler warnings and
596        some "unreachable code" warnings.
597    
598    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
599        things, this adds five new scripts.
600    
601    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
602        There were also incompatibilities regarding the handling of \Q..\E inside
603        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
604        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
605    
606    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
607        matches an empty string, and forcibly breaks the loop. There were bugs in
608        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
609        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
610        separate and independent bugs (that affected different cases) have been
611        fixed.
612    
613    39. Refactored the code to abolish the use of different opcodes for small
614        capturing bracket numbers. This is a tidy that I avoided doing when I
615        removed the limit on the number of capturing brackets for 3.5 back in 2001.
616        The new approach is not only tidier, it makes it possible to reduce the
617        memory needed to fix the previous bug (38).
618    
619    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
620        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
621        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
622        mode.
623    
624    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
625        report.
626    
627    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
628        copy construction and assignment in the C++ wrapper.
629    
630    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
631        couple of bugs that could have given wrong results in the "--newline=crlf"
632        case.
633    
634    44. Added a number of casts and did some reorganization of signed/unsigned int
635        variables following suggestions from Dair Grant. Also renamed the variable
636        "this" as "item" because it is a C++ keyword.
637    
638    45. Arranged for dftables to add
639    
640          #include "pcre_internal.h"
641    
642        to pcre_chartables.c because without it, gcc 4.x may remove the array
643        definition from the final binary if PCRE is built into a static library and
644        dead code stripping is activated.
645    
646    46. For an unanchored pattern, if a match attempt fails at the start of a
647        newline sequence, and the newline setting is CRLF or ANY, and the next two
648        characters are CRLF, advance by two characters instead of one.
649    
650    
651    Version 6.7 04-Jul-06
652    ---------------------
653    
654     1. In order to handle tests when input lines are enormously long, pcretest has
655        been re-factored so that it automatically extends its buffers when
656        necessary. The code is crude, but this _is_ just a test program. The
657        default size has been increased from 32K to 50K.
658    
659     2. The code in pcre_study() was using the value of the re argument before
660        testing it for NULL. (Of course, in any sensible call of the function, it
661        won't be NULL.)
662    
663     3. The memmove() emulation function in pcre_internal.h, which is used on
664        systems that lack both memmove() and bcopy() - that is, hardly ever -
665        was missing a "static" storage class specifier.
666    
667     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
668        containing an extended class (one that cannot be represented by a bitmap
669        because it contains high-valued characters or Unicode property items, e.g.
670        [\pZ]). Almost always one would set UTF-8 mode when processing such a
671        pattern, but PCRE should not loop if you do not (it no longer does).
672        [Detail: two cases were found: (a) a repeated subpattern containing an
673        extended class; (b) a recursive reference to a subpattern that followed a
674        previous extended class. It wasn't skipping over the extended class
675        correctly when UTF-8 mode was not set.]
676    
677     5. A negated single-character class was not being recognized as fixed-length
678        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
679        compile error "lookbehind assertion is not fixed length".
680    
681     6. The RunPerlTest auxiliary script was showing an unexpected difference
682        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
683        write a Perl script that can interpret lines of an input file either as
684        byte characters or as UTF-8, which is what "perltest" was being required to
685        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
686        can't do is switch easily at run time between having the "use utf8;" pragma
687        or not. In the end, I fudged it by using the RunPerlTest script to insert
688        "use utf8;" explicitly for the UTF-8 tests.
689    
690     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
691        the end of the subject string, contrary to the documentation and to what
692        Perl does. This was true of both matching functions. Now it matches only at
693        the start of the subject and immediately after *internal* newlines.
694    
695     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
696        a pointer to an int instead of a pointer to an unsigned long int. This
697        caused problems on 64-bit systems.
698    
699     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
700        instance of the 'standard' template library not being so standard".
701    
702    10. There was no check on the number of named subpatterns nor the maximum
703        length of a subpattern name. The product of these values is used to compute
704        the size of the memory block for a compiled pattern. By supplying a very
705        long subpattern name and a large number of named subpatterns, the size
706        computation could be caused to overflow. This is now prevented by limiting
707        the length of names to 32 characters, and the number of named subpatterns
708        to 10,000.
709    
710    11. Subpatterns that are repeated with specific counts have to be replicated in
711        the compiled pattern. The size of memory for this was computed from the
712        length of the subpattern and the repeat count. The latter is limited to
713        65535, but there was no limit on the former, meaning that integer overflow
714        could in principle occur. The compiled length of a repeated subpattern is
715        now limited to 30,000 bytes in order to prevent this.
716    
717    12. Added the optional facility to have named substrings with the same name.
718    
719    13. Added the ability to use a named substring as a condition, using the
720        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
721        are numbers (not recommended). Forward references are permitted.
722    
723    14. Added forward references in named backreferences (if you see what I mean).
724    
725    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
726        pattern could run off the end of the subject. For example, the pattern
727        "(?s)(.{1,5})"8 did this with the subject "ab".
728    
729    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
730        PCRE_CASELESS was set when matching characters that were quantified with ?
731        or *.
732    
733    17. A character class other than a single negated character that had a minimum
734        but no maximum quantifier - for example [ab]{6,} - was not handled
735        correctly by pce_dfa_exec(). It would match only one character.
736    
737    18. A valid (though odd) pattern that looked like a POSIX character
738        class but used an invalid character after [ (for example [[,abc,]]) caused
739        pcre_compile() to give the error "Failed: internal error: code overflow" or
740        in some cases to crash with a glibc free() error. This could even happen if
741        the pattern terminated after [[ but there just happened to be a sequence of
742        letters, a binary zero, and a closing ] in the memory that followed.
743    
744    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
745        over the years. Originally (before any Unicode support), just the bottom 8
746        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
747        output from "man perlunicode" includes this:
748    
749          The regular expression compiler produces polymorphic opcodes.  That
750          is, the pattern adapts to the data and automatically switches to
751          the Unicode character scheme when presented with Unicode data--or
752          instead uses a traditional byte scheme when presented with byte
753          data.
754    
755        Sadly, a wide octal escape does not cause a switch, and in a string with
756        no other multibyte characters, these octal escapes are treated as before.
757        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
758        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
759        Unicode string.
760    
761        I have not perpetrated such confusion in PCRE. Up till now, it took just
762        the bottom 8 bits, as in old Perl. I have now made octal escapes with
763        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
764        translate to the appropriate multibyte character.
765    
766    29. Applied some refactoring to reduce the number of warnings from Microsoft
767        and Borland compilers. This has included removing the fudge introduced
768        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
769        a warning about an unused variable.
770    
771    21. PCRE has not included VT (character 0x0b) in the set of whitespace
772        characters since release 4.0, because Perl (from release 5.004) does not.
773        [Or at least, is documented not to: some releases seem to be in conflict
774        with the documentation.] However, when a pattern was studied with
775        pcre_study() and all its branches started with \s, PCRE still included VT
776        as a possible starting character. Of course, this did no harm; it just
777        caused an unnecessary match attempt.
778    
779    22. Removed a now-redundant internal flag bit that recorded the fact that case
780        dependency changed within the pattern. This was once needed for "required
781        byte" processing, but is no longer used. This recovers a now-scarce options
782        bit. Also moved the least significant internal flag bit to the most-
783        significant bit of the word, which was not previously used (hangover from
784        the days when it was an int rather than a uint) to free up another bit for
785        the future.
786    
787    23. Added support for CRLF line endings as well as CR and LF. As well as the
788        default being selectable at build time, it can now be changed at runtime
789        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
790        specify that it is scanning data with non-default line endings.
791    
792    24. Changed the definition of CXXLINK to make it agree with the definition of
793        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
794    
795    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
796        recursions. This makes a big different to stack usage for some patterns.
797    
798    26. If a subpattern containing a named recursion or subroutine reference such
799        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
800        the space required for the compiled pattern went wrong and gave too small a
801        value. Depending on the environment, this could lead to "Failed: internal
802        error: code overflow at offset 49" or "glibc detected double free or
803        corruption" errors.
804    
805    27. Applied patches from Google (a) to support the new newline modes and (b) to
806        advance over multibyte UTF-8 characters in GlobalReplace.
807    
808    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
809        difference for some implementation of PCRE in some Windows version.
810    
811    29. Added some extra testing facilities to pcretest:
812    
813        \q<number>   in a data line sets the "match limit" value
814        \Q<number>   in a data line sets the "match recursion limt" value
815        -S <number>  sets the stack size, where <number> is in megabytes
816    
817        The -S option isn't available for Windows.
818    
819    
820  Version 6.6 06-Feb-06  Version 6.6 06-Feb-06
821  ---------------------  ---------------------
822    

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