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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
4    Version 7.4 10-Sep-07
5    ---------------------
7    1.  Change 7.3/28 was implemented for classes by looking at the bitmap. This
8        means that a class such as [\s] counted as "explicit reference to CR or
9        LF". That isn't really right - the whole point of the change was to try to
10        help when there was an actual mention of one of the two characters. So now
11        the change happens only if \r or \n (or a literal CR or LF) character is
12        encountered.
14    2.  The 32-bit options word was also used for 6 internal flags, but the numbers
15        of both had grown to the point where there were only 3 bits left.
16        Fortunately, there was spare space in the data structure, and so I have
17        moved the internal flags into a new 16-bit field to free up more option
18        bits.
20    3.  The appearance of (?J) at the start of a pattern set the DUPNAMES option,
21        but did not set the internal JCHANGED flag - either of these is enough to
22        control the way the "get" function works - but the PCRE_INFO_JCHANGED
23        facility is supposed to tell if (?J) was ever used, so now (?J) at the
24        start sets both bits.
26    4.  Added options (at build time, compile time, exec time) to change \R from
27        matching any Unicode line ending sequence to just matching CR, LF, or CRLF.
29    5.  doc/pcresyntax.html was missing from the distribution.
31    6.  Put back the definition of PCRE_ERROR_NULLWSLIMIT, for backward
32        compatibility, even though it is no longer used.
34    7.  Added macro for snprintf to pcrecpp_unittest.cc and also for strtoll and
35        strtoull to pcrecpp.cc to select the available functions in WIN32 when the
36        windows.h file is present (where different names are used).
38    8.  Changed all #include <config.h> to #include "config.h". There were also
39        some further <pcre.h> cases that I changed to "pcre.h".
41    9.  When pcregrep was used with the --colour option, it missed the line ending
42        sequence off the lines that it output.
44    10. It was pointed out to me that arrays of string pointers cause lots of
45        relocations when a shared library is dynamically loaded. A technique of
46        using a single long string with a table of offsets can drastically reduce
47        these. I have refactored PCRE in four places to do this. The result is
48        dramatic:
50          Originally:                          290
51          After changing UCP table:            187
52          After changing error message table:   43
53          After changing table of "verbs"       36
54          After changing table of Posix names   22
56        Thanks to the folks working on Gregex for glib for this insight.
58    11. --disable-stack-for-recursion caused compiling to fail unless -enable-
59        unicode-properties was also set.
61    12. Updated the tests so that they work when \R is defaulted to ANYCRLF.
63    13. Added checks for ANY and ANYCRLF to pcrecpp.cc where it previously
64        checked only for CRLF.
66    14. Added casts to pcretest.c to avoid compiler warnings.
69    Version 7.3 28-Aug-07
70    ---------------------
72     1. In the rejigging of the build system that eventually resulted in 7.1, the
73        line "#include <pcre.h>" was included in pcre_internal.h. The use of angle
74        brackets there is not right, since it causes compilers to look for an
75        installed pcre.h, not the version that is in the source that is being
76        compiled (which of course may be different). I have changed it back to:
78          #include "pcre.h"
80        I have a vague recollection that the change was concerned with compiling in
81        different directories, but in the new build system, that is taken care of
82        by the VPATH setting the Makefile.
84     2. The pattern .*$ when run in not-DOTALL UTF-8 mode with newline=any failed
85        when the subject happened to end in the byte 0x85 (e.g. if the last
86        character was \x{1ec5}). *Character* 0x85 is one of the "any" newline
87        characters but of course it shouldn't be taken as a newline when it is part
88        of another character. The bug was that, for an unlimited repeat of . in
89        not-DOTALL UTF-8 mode, PCRE was advancing by bytes rather than by
90        characters when looking for a newline.
92     3. A small performance improvement in the DOTALL UTF-8 mode .* case.
94     4. Debugging: adjusted the names of opcodes for different kinds of parentheses
95        in debug output.
97     5. Arrange to use "%I64d" instead of "%lld" and "%I64u" instead of "%llu" for
98        long printing in the pcrecpp unittest when running under MinGW.
100     6. ESC_K was left out of the EBCDIC table.
102     7. Change 7.0/38 introduced a new limit on the number of nested non-capturing
103        parentheses; I made it 1000, which seemed large enough. Unfortunately, the
104        limit also applies to "virtual nesting" when a pattern is recursive, and in
105        this case 1000 isn't so big. I have been able to remove this limit at the
106        expense of backing off one optimization in certain circumstances. Normally,
107        when pcre_exec() would call its internal match() function recursively and
108        immediately return the result unconditionally, it uses a "tail recursion"
109        feature to save stack. However, when a subpattern that can match an empty
110        string has an unlimited repetition quantifier, it no longer makes this
111        optimization. That gives it a stack frame in which to save the data for
112        checking that an empty string has been matched. Previously this was taken
113        from the 1000-entry workspace that had been reserved. So now there is no
114        explicit limit, but more stack is used.
116     8. Applied Daniel's patches to solve problems with the import/export magic
117        syntax that is required for Windows, and which was going wrong for the
118        pcreposix and pcrecpp parts of the library. These were overlooked when this
119        problem was solved for the main library.
121     9. There were some crude static tests to avoid integer overflow when computing
122        the size of patterns that contain repeated groups with explicit upper
123        limits. As the maximum quantifier is 65535, the maximum group length was
124        set at 30,000 so that the product of these two numbers did not overflow a
125        32-bit integer. However, it turns out that people want to use groups that
126        are longer than 30,000 bytes (though not repeat them that many times).
127        Change 7.0/17 (the refactoring of the way the pattern size is computed) has
128        made it possible to implement the integer overflow checks in a much more
129        dynamic way, which I have now done. The artificial limitation on group
130        length has been removed - we now have only the limit on the total length of
131        the compiled pattern, which depends on the LINK_SIZE setting.
133    10. Fixed a bug in the documentation for get/copy named substring when
134        duplicate names are permitted. If none of the named substrings are set, the
135        functions return PCRE_ERROR_NOSUBSTRING (7); the doc said they returned an
136        empty string.
138    11. Because Perl interprets \Q...\E at a high level, and ignores orphan \E
139        instances, patterns such as [\Q\E] or [\E] or even [^\E] cause an error,
140        because the ] is interpreted as the first data character and the
141        terminating ] is not found. PCRE has been made compatible with Perl in this
142        regard. Previously, it interpreted [\Q\E] as an empty class, and [\E] could
143        cause memory overwriting.
145    10. Like Perl, PCRE automatically breaks an unlimited repeat after an empty
146        string has been matched (to stop an infinite loop). It was not recognizing
147        a conditional subpattern that could match an empty string if that
148        subpattern was within another subpattern. For example, it looped when
149        trying to match  (((?(1)X|))*)  but it was OK with  ((?(1)X|)*)  where the
150        condition was not nested. This bug has been fixed.
152    12. A pattern like \X?\d or \P{L}?\d in non-UTF-8 mode could cause a backtrack
153        past the start of the subject in the presence of bytes with the top bit
154        set, for example "\x8aBCD".
156    13. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
157        (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
159    14. Optimized (?!) to (*FAIL).
161    15. Updated the test for a valid UTF-8 string to conform to the later RFC 3629.
162        This restricts code points to be within the range 0 to 0x10FFFF, excluding
163        the "low surrogate" sequence 0xD800 to 0xDFFF. Previously, PCRE allowed the
164        full range 0 to 0x7FFFFFFF, as defined by RFC 2279. Internally, it still
165        does: it's just the validity check that is more restrictive.
167    16. Inserted checks for integer overflows during escape sequence (backslash)
168        processing, and also fixed erroneous offset values for syntax errors during
169        backslash processing.
171    17. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
172        for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
174    18. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
175        caused an overrun.
177    19. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
178        something other than just ASCII characters) inside a group that had an
179        unlimited repeat caused a loop at compile time (while checking to see
180        whether the group could match an empty string).
182    20. Debugging a pattern containing \p or \P could cause a crash. For example,
183        [\P{Any}] did so. (Error in the code for printing property names.)
185    21. An orphan \E inside a character class could cause a crash.
187    22. A repeated capturing bracket such as (A)? could cause a wild memory
188        reference during compilation.
190    23. There are several functions in pcre_compile() that scan along a compiled
191        expression for various reasons (e.g. to see if it's fixed length for look
192        behind). There were bugs in these functions when a repeated \p or \P was
193        present in the pattern. These operators have additional parameters compared
194        with \d, etc, and these were not being taken into account when moving along
195        the compiled data. Specifically:
197        (a) A item such as \p{Yi}{3} in a lookbehind was not treated as fixed
198            length.
200        (b) An item such as \pL+ within a repeated group could cause crashes or
201            loops.
203        (c) A pattern such as \p{Yi}+(\P{Yi}+)(?1) could give an incorrect
204            "reference to non-existent subpattern" error.
206        (d) A pattern like (\P{Yi}{2}\277)? could loop at compile time.
208    24. A repeated \S or \W in UTF-8 mode could give wrong answers when multibyte
209        characters were involved (for example /\S{2}/8g with "A\x{a3}BC").
211    25. Using pcregrep in multiline, inverted mode (-Mv) caused it to loop.
213    26. Patterns such as [\P{Yi}A] which include \p or \P and just one other
214        character were causing crashes (broken optimization).
216    27. Patterns such as (\P{Yi}*\277)* (group with possible zero repeat containing
217        \p or \P) caused a compile-time loop.
219    28. More problems have arisen in unanchored patterns when CRLF is a valid line
220        break. For example, the unstudied pattern [\r\n]A does not match the string
221        "\r\nA" because change 7.0/46 below moves the current point on by two
222        characters after failing to match at the start. However, the pattern \nA
223        *does* match, because it doesn't start till \n, and if [\r\n]A is studied,
224        the same is true. There doesn't seem any very clean way out of this, but
225        what I have chosen to do makes the common cases work: PCRE now takes note
226        of whether there can be an explicit match for \r or \n anywhere in the
227        pattern, and if so, 7.0/46 no longer applies. As part of this change,
228        there's a new PCRE_INFO_HASCRORLF option for finding out whether a compiled
229        pattern has explicit CR or LF references.
231    29. Added (*CR) etc for changing newline setting at start of pattern.
234    Version 7.2 19-Jun-07
235    ---------------------
237     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
238        which is apparently normally available under Windows.
240     2. Re-jig the pcregrep tests with different newline settings in an attempt
241        to make them independent of the local environment's newline setting.
243     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
245     4. Some of the "internals" tests were previously cut out when the link size
246        was not 2, because the output contained actual offsets. The recent new
247        "Z" feature of pcretest means that these can be cut out, making the tests
248        usable with all link sizes.
250     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
251        stack recursion. This gives a massive performance boost under BSD, but just
252        a small improvement under Linux. However, it saves one field in the frame
253        in all cases.
255     6. Added more features from the forthcoming Perl 5.10:
257        (a) (?-n) (where n is a string of digits) is a relative subroutine or
258            recursion call. It refers to the nth most recently opened parentheses.
260        (b) (?+n) is also a relative subroutine call; it refers to the nth next
261            to be opened parentheses.
263        (c) Conditions that refer to capturing parentheses can be specified
264            relatively, for example, (?(-2)... or (?(+3)...
266        (d) \K resets the start of the current match so that everything before
267            is not part of it.
269        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
271        (f) \g{name} is another synonym - part of Perl 5.10's unification of
272            reference syntax.
274        (g) (?| introduces a group in which the numbering of parentheses in each
275            alternative starts with the same number.
277        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
279     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
282     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
283        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
284        for detecting groups that can match an empty string.
286     9. A pattern with a very large number of alternatives (more than several
287        hundred) was running out of internal workspace during the pre-compile
288        phase, where pcre_compile() figures out how much memory will be needed. A
289        bit of new cunning has reduced the workspace needed for groups with
290        alternatives. The 1000-alternative test pattern now uses 12 bytes of
291        workspace instead of running out of the 4096 that are available.
293    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
295    11. Applied patch from Google to remove an optimization that didn't quite work.
296        The report of the bug said:
298          pcrecpp::RE("a*").FullMatch("aaa") matches, while
299          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
300          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
302    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
303        it matched the wrong number of bytes.
306    Version 7.1 24-Apr-07
307    ---------------------
309     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
310        that is more "standard", making use of automake and other Autotools. There
311        is some re-arrangement of the files and adjustment of comments consequent
312        on this.
314     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
315        for recursive directory scanning broke on some systems because the files
316        are not scanned in any specific order and on different systems the order
317        was different. A call to "sort" has been inserted into RunGrepTest for the
318        approprate test as a short-term fix. In the longer term there may be an
319        alternative.
321     3. I had an email from Eric Raymond about problems translating some of PCRE's
322        man pages to HTML (despite the fact that I distribute HTML pages, some
323        people do their own conversions for various reasons). The problems
324        concerned the use of low-level troff macros .br and .in. I have therefore
325        removed all such uses from the man pages (some were redundant, some could
326        be replaced by .nf/.fi pairs). The 132html script that I use to generate
327        HTML has been updated to handle .nf/.fi and to complain if it encounters
328        .br or .in.
330     4. Updated comments in configure.ac that get placed in config.h.in and also
331        arranged for config.h to be included in the distribution, with the name
332        config.h.generic, for the benefit of those who have to compile without
333        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
335     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
336        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
337        makevp.bat for the current PCRE, using the additional files
338        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
340     6. A Windows user reported a minor discrepancy with test 2, which turned out
341        to be caused by a trailing space on an input line that had got lost in his
342        copy. The trailing space was an accident, so I've just removed it.
344     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
345        that is needed.
347     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
348        as "const" (a) because they are and (b) because it helps the PHP
349        maintainers who have recently made a script to detect big data structures
350        in the php code that should be moved to the .rodata section. I remembered
351        to update Builducptable as well, so it won't revert if ucptable.h is ever
352        re-created.
354     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
355        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
356        order to be able to cut out the UTF-8 tables in the latter when UTF-8
357        support is not required. This saves 1.5-2K of code, which is important in
358        some applications.
360        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
361        so as not to refer to the tables, even though these functions will never be
362        called when UTF-8 support is disabled. Otherwise there are problems with a
363        shared library.
365    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
367        (a) It was defining its arguments as char * instead of void *.
369        (b) It was assuming that all moves were upwards in memory; this was true
370            a long time ago when I wrote it, but is no longer the case.
372        The emulated memove() is provided for those environments that have neither
373        memmove() nor bcopy(). I didn't think anyone used it these days, but that
374        is clearly not the case, as these two bugs were recently reported.
376    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
377        and Detrail to create the HTML documentation, the .txt form of the man
378        pages, and it removes trailing spaces from listed files. It also creates
379        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
380        case, it wraps all the #defines with #ifndefs. This script should be run
381        before "make dist".
383    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
384        with Unicode property support.
386        (a) For a maximizing quantifier, if the two different cases of the
387            character were of different lengths in their UTF-8 codings (there are
388            some cases like this - I found 11), and the matching function had to
389            back up over a mixture of the two cases, it incorrectly assumed they
390            were both the same length.
392        (b) When PCRE was configured to use the heap rather than the stack for
393            recursion during matching, it was not correctly preserving the data for
394            the other case of a UTF-8 character when checking ahead for a match
395            while processing a minimizing repeat. If the check also involved
396            matching a wide character, but failed, corruption could cause an
397            erroneous result when trying to check for a repeat of the original
398            character.
400    13. Some tidying changes to the testing mechanism:
402        (a) The RunTest script now detects the internal link size and whether there
403            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
404            values substituted by "configure". (The RunGrepTest script already did
405            this for UTF-8.) The configure.ac script no longer substitutes the
406            relevant variables.
408        (b) The debugging options /B and /D in pcretest show the compiled bytecode
409            with length and offset values. This means that the output is different
410            for different internal link sizes. Test 2 is skipped for link sizes
411            other than 2 because of this, bypassing the problem. Unfortunately,
412            there was also a test in test 3 (the locale tests) that used /B and
413            failed for link sizes other than 2. Rather than cut the whole test out,
414            I have added a new /Z option to pcretest that replaces the length and
415            offset values with spaces. This is now used to make test 3 independent
416            of link size. (Test 2 will be tidied up later.)
418    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
419        segmentation fault instead of returning the appropriate error message.
421    15. In multiline mode when the newline sequence was set to "any", the pattern
422        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
423        This doesn't seem right; it now treats the CRLF combination as the line
424        ending, and so does not match in that case. It's only a pattern such as ^$
425        that would hit this one: something like ^ABC$ would have failed after \r
426        and then tried again after \r\n.
428    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
429        in an attempt to make files that differ only in their line terminators
430        compare equal. This works on Linux.
432    17. Under certain error circumstances pcregrep might try to free random memory
433        as it exited. This is now fixed, thanks to valgrind.
435    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
436        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
437        was because its rules for how to advance for /g after matching an empty
438        string at the end of a line did not allow for this case. They now check for
439        it specially.
441    20. pcretest is supposed to handle patterns and data of any length, by
442        extending its buffers when necessary. It was getting this wrong when the
443        buffer for a data line had to be extended.
445    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
446        CRLF as a newline sequence.
448    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
449        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
450        I have nevertheless tidied it up.
452    23. Added some casts to kill warnings from HP-UX ia64 compiler.
454    24. Added a man page for pcre-config.
457    Version 7.0 19-Dec-06
458    ---------------------
460     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
461        moving to gcc 4.1.1.
463     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
464        sys/time.h, which is documented as needed for this function. It doesn't
465        seem to matter on Linux, but it showed up on some releases of OS X.
467     3. It seems that there are systems where bytes whose values are greater than
468        127 match isprint() in the "C" locale. The "C" locale should be the
469        default when a C program starts up. In most systems, only ASCII printing
470        characters match isprint(). This difference caused the output from pcretest
471        to vary, making some of the tests fail. I have changed pcretest so that:
473        (a) When it is outputting text in the compiled version of a pattern, bytes
474            other than 32-126 are always shown as hex escapes.
476        (b) When it is outputting text that is a matched part of a subject string,
477            it does the same, unless a different locale has been set for the match
478            (using the /L modifier). In this case, it uses isprint() to decide.
480     4. Fixed a major bug that caused incorrect computation of the amount of memory
481        required for a compiled pattern when options that changed within the
482        pattern affected the logic of the preliminary scan that determines the
483        length. The relevant options are -x, and -i in UTF-8 mode. The result was
484        that the computed length was too small. The symptoms of this bug were
485        either the PCRE error "internal error: code overflow" from pcre_compile(),
486        or a glibc crash with a message such as "pcretest: free(): invalid next
487        size (fast)". Examples of patterns that provoked this bug (shown in
488        pcretest format) are:
490          /(?-x: )/x
491          /(?x)(?-x: \s*#\s*)/
492          /((?i)[\x{c0}])/8
493          /(?i:[\x{c0}])/8
495        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
496        is now done differently.
498     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
499        wrapper classes; (b) implement a new function in the C++ scanner that is
500        more efficient than the old way of doing things because it avoids levels of
501        recursion in the regex matching; (c) add a paragraph to the documentation
502        for the FullMatch() function.
504     6. The escape sequence \n was being treated as whatever was defined as
505        "newline". Not only was this contrary to the documentation, which states
506        that \n is character 10 (hex 0A), but it also went horribly wrong when
507        "newline" was defined as CRLF. This has been fixed.
509     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
510        was being set to -1 for the "end of line" case (supposedly a value that no
511        character can have). Though this value is never used (the check for end of
512        line is "zero bytes in current character"), it caused compiler complaints.
513        I've changed it to 0xffffffff.
515     8. In pcre_version.c, the version string was being built by a sequence of
516        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
517        string (as it is for production releases) called a macro with an empty
518        argument. The C standard says the result of this is undefined. The gcc
519        compiler treats it as an empty string (which was what was wanted) but it is
520        reported that Visual C gives an error. The source has been hacked around to
521        avoid this problem.
523     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
524        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
525        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
526        of them did).
528    10. Originally, pcretest opened its input and output without "b"; then I was
529        told that "b" was needed in some environments, so it was added for release
530        5.0 to both the input and output. (It makes no difference on Unix-like
531        systems.) Later I was told that it is wrong for the input on Windows. I've
532        now abstracted the modes into two macros, to make it easier to fiddle with
533        them, and removed "b" from the input mode under Windows.
535    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
537    12. Added -help and --help to pcretest as an official way of being reminded
538        of the options.
540    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
541        and pcrecpp.cc because they annoy compilers at high warning levels.
543    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
545    15. Fixed an occurrence of == in configure.ac that should have been = (shell
546        scripts are not C programs :-) and which was not noticed because it works
547        on Linux.
549    16. pcretest is supposed to handle any length of pattern and data line (as one
550        line or as a continued sequence of lines) by extending its input buffer if
551        necessary. This feature was broken for very long pattern lines, leading to
552        a string of junk being passed to pcre_compile() if the pattern was longer
553        than about 50K.
555    17. I have done a major re-factoring of the way pcre_compile() computes the
556        amount of memory needed for a compiled pattern. Previously, there was code
557        that made a preliminary scan of the pattern in order to do this. That was
558        OK when PCRE was new, but as the facilities have expanded, it has become
559        harder and harder to keep it in step with the real compile phase, and there
560        have been a number of bugs (see for example, 4 above). I have now found a
561        cunning way of running the real compile function in a "fake" mode that
562        enables it to compute how much memory it would need, while actually only
563        ever using a few hundred bytes of working memory and without too many
564        tests of the mode. This should make future maintenance and development
565        easier. A side effect of this work is that the limit of 200 on the nesting
566        depth of parentheses has been removed (though this was never a serious
567        limitation, I suspect). However, there is a downside: pcre_compile() now
568        runs more slowly than before (30% or more, depending on the pattern). I
569        hope this isn't a big issue. There is no effect on runtime performance.
571    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
572        newline (only possible for the last line of a file) and it was a
573        pattern that set a locale (followed by /Lsomething), pcretest crashed.
575    19. Added additional timing features to pcretest. (1) The -tm option now times
576        matching only, not compiling. (2) Both -t and -tm can be followed, as a
577        separate command line item, by a number that specifies the number of
578        repeats to use when timing. The default is 50000; this gives better
579        precision, but takes uncomfortably long for very large patterns.
581    20. Extended pcre_study() to be more clever in cases where a branch of a
582        subpattern has no definite first character. For example, (a*|b*)[cd] would
583        previously give no result from pcre_study(). Now it recognizes that the
584        first character must be a, b, c, or d.
586    21. There was an incorrect error "recursive call could loop indefinitely" if
587        a subpattern (or the entire pattern) that was being tested for matching an
588        empty string contained only one non-empty item after a nested subpattern.
589        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
590        incorrectly, because the \d was being skipped in the check.
592    22. The pcretest program now has a new pattern option /B and a command line
593        option -b, which is equivalent to adding /B to every pattern. This causes
594        it to show the compiled bytecode, without the additional information that
595        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
596        is the same as /B/I).
598    23. A new optimization is now able automatically to treat some sequences such
599        as a*b as a*+b. More specifically, if something simple (such as a character
600        or a simple class like \d) has an unlimited quantifier, and is followed by
601        something that cannot possibly match the quantified thing, the quantifier
602        is automatically "possessified".
604    24. A recursive reference to a subpattern whose number was greater than 39
605        went wrong under certain circumstances in UTF-8 mode. This bug could also
606        have affected the operation of pcre_study().
608    25. Realized that a little bit of performance could be had by replacing
609        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
611    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
613    27. Possessive quantifiers such as a++ were previously implemented by turning
614        them into atomic groups such as ($>a+). Now they have their own opcodes,
615        which improves performance. This includes the automatically created ones
616        from 23 above.
618    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
619        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
620        the first matched character to be a colon. This applied both to named and
621        numbered groups.
623    29. The ucpinternal.h header file was missing its idempotency #ifdef.
625    30. I was sent a "project" file called libpcre.a.dev which I understand makes
626        building PCRE on Windows easier, so I have included it in the distribution.
628    31. There is now a check in pcretest against a ridiculously large number being
629        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
630        loop, the loop is abandoned.
632    32. Forward references to subpatterns in conditions such as (?(2)...) where
633        subpattern 2 is defined later cause pcre_compile() to search forwards in
634        the pattern for the relevant set of parentheses. This search went wrong
635        when there were unescaped parentheses in a character class, parentheses
636        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
638    33. "Subroutine" calls and backreferences were previously restricted to
639        referencing subpatterns earlier in the regex. This restriction has now
640        been removed.
642    34. Added a number of extra features that are going to be in Perl 5.10. On the
643        whole, these are just syntactic alternatives for features that PCRE had
644        previously implemented using the Python syntax or my own invention. The
645        other formats are all retained for compatibility.
647        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
648            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
649            also .NET compatible.
651        (b) A recursion or subroutine call to a named group can now be defined as
652            (?&name) as well as (?P>name).
654        (c) A backreference to a named group can now be defined as \k<name> or
655            \k'name' as well as (?P=name). The new forms, as well as being in Perl
656            5.10, are also .NET compatible.
658        (d) A conditional reference to a named group can now use the syntax
659            (?(<name>) or (?('name') as well as (?(name).
661        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
662            groups (named and numbered) that are never evaluated inline, but can be
663            called as "subroutines" from elsewhere. In effect, the DEFINE condition
664            is always false. There may be only one alternative in such a group.
666        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
667            as the simple (?(R). The condition is true only if the most recent
668            recursion is that of the given number or name. It does not search out
669            through the entire recursion stack.
671        (g) The escape \gN or \g{N} has been added, where N is a positive or
672            negative number, specifying an absolute or relative reference.
674    35. Tidied to get rid of some further signed/unsigned compiler warnings and
675        some "unreachable code" warnings.
677    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
678        things, this adds five new scripts.
680    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
681        There were also incompatibilities regarding the handling of \Q..\E inside
682        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
683        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
685    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
686        matches an empty string, and forcibly breaks the loop. There were bugs in
687        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
688        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
689        separate and independent bugs (that affected different cases) have been
690        fixed.
692    39. Refactored the code to abolish the use of different opcodes for small
693        capturing bracket numbers. This is a tidy that I avoided doing when I
694        removed the limit on the number of capturing brackets for 3.5 back in 2001.
695        The new approach is not only tidier, it makes it possible to reduce the
696        memory needed to fix the previous bug (38).
698    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
699        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
700        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
701        mode.
703    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
704        report.
706    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
707        copy construction and assignment in the C++ wrapper.
709    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
710        couple of bugs that could have given wrong results in the "--newline=crlf"
711        case.
713    44. Added a number of casts and did some reorganization of signed/unsigned int
714        variables following suggestions from Dair Grant. Also renamed the variable
715        "this" as "item" because it is a C++ keyword.
717    45. Arranged for dftables to add
719          #include "pcre_internal.h"
721        to pcre_chartables.c because without it, gcc 4.x may remove the array
722        definition from the final binary if PCRE is built into a static library and
723        dead code stripping is activated.
725    46. For an unanchored pattern, if a match attempt fails at the start of a
726        newline sequence, and the newline setting is CRLF or ANY, and the next two
727        characters are CRLF, advance by two characters instead of one.
730  Version 6.7 04-Jul-06  Version 6.7 04-Jul-06
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