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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.
64    Version 7.3 28-Aug-07
65    ---------------------
67     1. In the rejigging of the build system that eventually resulted in 7.1, the
68        line "#include <pcre.h>" was included in pcre_internal.h. The use of angle
69        brackets there is not right, since it causes compilers to look for an
70        installed pcre.h, not the version that is in the source that is being
71        compiled (which of course may be different). I have changed it back to:
73          #include "pcre.h"
75        I have a vague recollection that the change was concerned with compiling in
76        different directories, but in the new build system, that is taken care of
77        by the VPATH setting the Makefile.
79     2. The pattern .*$ when run in not-DOTALL UTF-8 mode with newline=any failed
80        when the subject happened to end in the byte 0x85 (e.g. if the last
81        character was \x{1ec5}). *Character* 0x85 is one of the "any" newline
82        characters but of course it shouldn't be taken as a newline when it is part
83        of another character. The bug was that, for an unlimited repeat of . in
84        not-DOTALL UTF-8 mode, PCRE was advancing by bytes rather than by
85        characters when looking for a newline.
87     3. A small performance improvement in the DOTALL UTF-8 mode .* case.
89     4. Debugging: adjusted the names of opcodes for different kinds of parentheses
90        in debug output.
92     5. Arrange to use "%I64d" instead of "%lld" and "%I64u" instead of "%llu" for
93        long printing in the pcrecpp unittest when running under MinGW.
95     6. ESC_K was left out of the EBCDIC table.
97     7. Change 7.0/38 introduced a new limit on the number of nested non-capturing
98        parentheses; I made it 1000, which seemed large enough. Unfortunately, the
99        limit also applies to "virtual nesting" when a pattern is recursive, and in
100        this case 1000 isn't so big. I have been able to remove this limit at the
101        expense of backing off one optimization in certain circumstances. Normally,
102        when pcre_exec() would call its internal match() function recursively and
103        immediately return the result unconditionally, it uses a "tail recursion"
104        feature to save stack. However, when a subpattern that can match an empty
105        string has an unlimited repetition quantifier, it no longer makes this
106        optimization. That gives it a stack frame in which to save the data for
107        checking that an empty string has been matched. Previously this was taken
108        from the 1000-entry workspace that had been reserved. So now there is no
109        explicit limit, but more stack is used.
111     8. Applied Daniel's patches to solve problems with the import/export magic
112        syntax that is required for Windows, and which was going wrong for the
113        pcreposix and pcrecpp parts of the library. These were overlooked when this
114        problem was solved for the main library.
116     9. There were some crude static tests to avoid integer overflow when computing
117        the size of patterns that contain repeated groups with explicit upper
118        limits. As the maximum quantifier is 65535, the maximum group length was
119        set at 30,000 so that the product of these two numbers did not overflow a
120        32-bit integer. However, it turns out that people want to use groups that
121        are longer than 30,000 bytes (though not repeat them that many times).
122        Change 7.0/17 (the refactoring of the way the pattern size is computed) has
123        made it possible to implement the integer overflow checks in a much more
124        dynamic way, which I have now done. The artificial limitation on group
125        length has been removed - we now have only the limit on the total length of
126        the compiled pattern, which depends on the LINK_SIZE setting.
128    10. Fixed a bug in the documentation for get/copy named substring when
129        duplicate names are permitted. If none of the named substrings are set, the
130        functions return PCRE_ERROR_NOSUBSTRING (7); the doc said they returned an
131        empty string.
133    11. Because Perl interprets \Q...\E at a high level, and ignores orphan \E
134        instances, patterns such as [\Q\E] or [\E] or even [^\E] cause an error,
135        because the ] is interpreted as the first data character and the
136        terminating ] is not found. PCRE has been made compatible with Perl in this
137        regard. Previously, it interpreted [\Q\E] as an empty class, and [\E] could
138        cause memory overwriting.
140    10. Like Perl, PCRE automatically breaks an unlimited repeat after an empty
141        string has been matched (to stop an infinite loop). It was not recognizing
142        a conditional subpattern that could match an empty string if that
143        subpattern was within another subpattern. For example, it looped when
144        trying to match  (((?(1)X|))*)  but it was OK with  ((?(1)X|)*)  where the
145        condition was not nested. This bug has been fixed.
147    12. A pattern like \X?\d or \P{L}?\d in non-UTF-8 mode could cause a backtrack
148        past the start of the subject in the presence of bytes with the top bit
149        set, for example "\x8aBCD".
151    13. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
152        (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
154    14. Optimized (?!) to (*FAIL).
156    15. Updated the test for a valid UTF-8 string to conform to the later RFC 3629.
157        This restricts code points to be within the range 0 to 0x10FFFF, excluding
158        the "low surrogate" sequence 0xD800 to 0xDFFF. Previously, PCRE allowed the
159        full range 0 to 0x7FFFFFFF, as defined by RFC 2279. Internally, it still
160        does: it's just the validity check that is more restrictive.
162    16. Inserted checks for integer overflows during escape sequence (backslash)
163        processing, and also fixed erroneous offset values for syntax errors during
164        backslash processing.
166    17. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
167        for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
169    18. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
170        caused an overrun.
172    19. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
173        something other than just ASCII characters) inside a group that had an
174        unlimited repeat caused a loop at compile time (while checking to see
175        whether the group could match an empty string).
177    20. Debugging a pattern containing \p or \P could cause a crash. For example,
178        [\P{Any}] did so. (Error in the code for printing property names.)
180    21. An orphan \E inside a character class could cause a crash.
182    22. A repeated capturing bracket such as (A)? could cause a wild memory
183        reference during compilation.
185    23. There are several functions in pcre_compile() that scan along a compiled
186        expression for various reasons (e.g. to see if it's fixed length for look
187        behind). There were bugs in these functions when a repeated \p or \P was
188        present in the pattern. These operators have additional parameters compared
189        with \d, etc, and these were not being taken into account when moving along
190        the compiled data. Specifically:
192        (a) A item such as \p{Yi}{3} in a lookbehind was not treated as fixed
193            length.
195        (b) An item such as \pL+ within a repeated group could cause crashes or
196            loops.
198        (c) A pattern such as \p{Yi}+(\P{Yi}+)(?1) could give an incorrect
199            "reference to non-existent subpattern" error.
201        (d) A pattern like (\P{Yi}{2}\277)? could loop at compile time.
203    24. A repeated \S or \W in UTF-8 mode could give wrong answers when multibyte
204        characters were involved (for example /\S{2}/8g with "A\x{a3}BC").
206    25. Using pcregrep in multiline, inverted mode (-Mv) caused it to loop.
208    26. Patterns such as [\P{Yi}A] which include \p or \P and just one other
209        character were causing crashes (broken optimization).
211    27. Patterns such as (\P{Yi}*\277)* (group with possible zero repeat containing
212        \p or \P) caused a compile-time loop.
214    28. More problems have arisen in unanchored patterns when CRLF is a valid line
215        break. For example, the unstudied pattern [\r\n]A does not match the string
216        "\r\nA" because change 7.0/46 below moves the current point on by two
217        characters after failing to match at the start. However, the pattern \nA
218        *does* match, because it doesn't start till \n, and if [\r\n]A is studied,
219        the same is true. There doesn't seem any very clean way out of this, but
220        what I have chosen to do makes the common cases work: PCRE now takes note
221        of whether there can be an explicit match for \r or \n anywhere in the
222        pattern, and if so, 7.0/46 no longer applies. As part of this change,
223        there's a new PCRE_INFO_HASCRORLF option for finding out whether a compiled
224        pattern has explicit CR or LF references.
226    29. Added (*CR) etc for changing newline setting at start of pattern.
229    Version 7.2 19-Jun-07
230    ---------------------
232     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
233        which is apparently normally available under Windows.
235     2. Re-jig the pcregrep tests with different newline settings in an attempt
236        to make them independent of the local environment's newline setting.
238     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
240     4. Some of the "internals" tests were previously cut out when the link size
241        was not 2, because the output contained actual offsets. The recent new
242        "Z" feature of pcretest means that these can be cut out, making the tests
243        usable with all link sizes.
245     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
246        stack recursion. This gives a massive performance boost under BSD, but just
247        a small improvement under Linux. However, it saves one field in the frame
248        in all cases.
250     6. Added more features from the forthcoming Perl 5.10:
252        (a) (?-n) (where n is a string of digits) is a relative subroutine or
253            recursion call. It refers to the nth most recently opened parentheses.
255        (b) (?+n) is also a relative subroutine call; it refers to the nth next
256            to be opened parentheses.
258        (c) Conditions that refer to capturing parentheses can be specified
259            relatively, for example, (?(-2)... or (?(+3)...
261        (d) \K resets the start of the current match so that everything before
262            is not part of it.
264        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
266        (f) \g{name} is another synonym - part of Perl 5.10's unification of
267            reference syntax.
269        (g) (?| introduces a group in which the numbering of parentheses in each
270            alternative starts with the same number.
272        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
274     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
277     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
278        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
279        for detecting groups that can match an empty string.
281     9. A pattern with a very large number of alternatives (more than several
282        hundred) was running out of internal workspace during the pre-compile
283        phase, where pcre_compile() figures out how much memory will be needed. A
284        bit of new cunning has reduced the workspace needed for groups with
285        alternatives. The 1000-alternative test pattern now uses 12 bytes of
286        workspace instead of running out of the 4096 that are available.
288    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
290    11. Applied patch from Google to remove an optimization that didn't quite work.
291        The report of the bug said:
293          pcrecpp::RE("a*").FullMatch("aaa") matches, while
294          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
295          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
297    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
298        it matched the wrong number of bytes.
301    Version 7.1 24-Apr-07
302    ---------------------
304     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
305        that is more "standard", making use of automake and other Autotools. There
306        is some re-arrangement of the files and adjustment of comments consequent
307        on this.
309     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
310        for recursive directory scanning broke on some systems because the files
311        are not scanned in any specific order and on different systems the order
312        was different. A call to "sort" has been inserted into RunGrepTest for the
313        approprate test as a short-term fix. In the longer term there may be an
314        alternative.
316     3. I had an email from Eric Raymond about problems translating some of PCRE's
317        man pages to HTML (despite the fact that I distribute HTML pages, some
318        people do their own conversions for various reasons). The problems
319        concerned the use of low-level troff macros .br and .in. I have therefore
320        removed all such uses from the man pages (some were redundant, some could
321        be replaced by .nf/.fi pairs). The 132html script that I use to generate
322        HTML has been updated to handle .nf/.fi and to complain if it encounters
323        .br or .in.
325     4. Updated comments in configure.ac that get placed in config.h.in and also
326        arranged for config.h to be included in the distribution, with the name
327        config.h.generic, for the benefit of those who have to compile without
328        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
330     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
331        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
332        makevp.bat for the current PCRE, using the additional files
333        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
335     6. A Windows user reported a minor discrepancy with test 2, which turned out
336        to be caused by a trailing space on an input line that had got lost in his
337        copy. The trailing space was an accident, so I've just removed it.
339     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
340        that is needed.
342     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
343        as "const" (a) because they are and (b) because it helps the PHP
344        maintainers who have recently made a script to detect big data structures
345        in the php code that should be moved to the .rodata section. I remembered
346        to update Builducptable as well, so it won't revert if ucptable.h is ever
347        re-created.
349     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
350        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
351        order to be able to cut out the UTF-8 tables in the latter when UTF-8
352        support is not required. This saves 1.5-2K of code, which is important in
353        some applications.
355        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
356        so as not to refer to the tables, even though these functions will never be
357        called when UTF-8 support is disabled. Otherwise there are problems with a
358        shared library.
360    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
362        (a) It was defining its arguments as char * instead of void *.
364        (b) It was assuming that all moves were upwards in memory; this was true
365            a long time ago when I wrote it, but is no longer the case.
367        The emulated memove() is provided for those environments that have neither
368        memmove() nor bcopy(). I didn't think anyone used it these days, but that
369        is clearly not the case, as these two bugs were recently reported.
371    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
372        and Detrail to create the HTML documentation, the .txt form of the man
373        pages, and it removes trailing spaces from listed files. It also creates
374        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
375        case, it wraps all the #defines with #ifndefs. This script should be run
376        before "make dist".
378    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
379        with Unicode property support.
381        (a) For a maximizing quantifier, if the two different cases of the
382            character were of different lengths in their UTF-8 codings (there are
383            some cases like this - I found 11), and the matching function had to
384            back up over a mixture of the two cases, it incorrectly assumed they
385            were both the same length.
387        (b) When PCRE was configured to use the heap rather than the stack for
388            recursion during matching, it was not correctly preserving the data for
389            the other case of a UTF-8 character when checking ahead for a match
390            while processing a minimizing repeat. If the check also involved
391            matching a wide character, but failed, corruption could cause an
392            erroneous result when trying to check for a repeat of the original
393            character.
395    13. Some tidying changes to the testing mechanism:
397        (a) The RunTest script now detects the internal link size and whether there
398            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
399            values substituted by "configure". (The RunGrepTest script already did
400            this for UTF-8.) The configure.ac script no longer substitutes the
401            relevant variables.
403        (b) The debugging options /B and /D in pcretest show the compiled bytecode
404            with length and offset values. This means that the output is different
405            for different internal link sizes. Test 2 is skipped for link sizes
406            other than 2 because of this, bypassing the problem. Unfortunately,
407            there was also a test in test 3 (the locale tests) that used /B and
408            failed for link sizes other than 2. Rather than cut the whole test out,
409            I have added a new /Z option to pcretest that replaces the length and
410            offset values with spaces. This is now used to make test 3 independent
411            of link size. (Test 2 will be tidied up later.)
413    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
414        segmentation fault instead of returning the appropriate error message.
416    15. In multiline mode when the newline sequence was set to "any", the pattern
417        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
418        This doesn't seem right; it now treats the CRLF combination as the line
419        ending, and so does not match in that case. It's only a pattern such as ^$
420        that would hit this one: something like ^ABC$ would have failed after \r
421        and then tried again after \r\n.
423    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
424        in an attempt to make files that differ only in their line terminators
425        compare equal. This works on Linux.
427    17. Under certain error circumstances pcregrep might try to free random memory
428        as it exited. This is now fixed, thanks to valgrind.
430    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
431        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
432        was because its rules for how to advance for /g after matching an empty
433        string at the end of a line did not allow for this case. They now check for
434        it specially.
436    20. pcretest is supposed to handle patterns and data of any length, by
437        extending its buffers when necessary. It was getting this wrong when the
438        buffer for a data line had to be extended.
440    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
441        CRLF as a newline sequence.
443    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
444        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
445        I have nevertheless tidied it up.
447    23. Added some casts to kill warnings from HP-UX ia64 compiler.
449    24. Added a man page for pcre-config.
452    Version 7.0 19-Dec-06
453    ---------------------
455     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
456        moving to gcc 4.1.1.
458     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
459        sys/time.h, which is documented as needed for this function. It doesn't
460        seem to matter on Linux, but it showed up on some releases of OS X.
462     3. It seems that there are systems where bytes whose values are greater than
463        127 match isprint() in the "C" locale. The "C" locale should be the
464        default when a C program starts up. In most systems, only ASCII printing
465        characters match isprint(). This difference caused the output from pcretest
466        to vary, making some of the tests fail. I have changed pcretest so that:
468        (a) When it is outputting text in the compiled version of a pattern, bytes
469            other than 32-126 are always shown as hex escapes.
471        (b) When it is outputting text that is a matched part of a subject string,
472            it does the same, unless a different locale has been set for the match
473            (using the /L modifier). In this case, it uses isprint() to decide.
475     4. Fixed a major bug that caused incorrect computation of the amount of memory
476        required for a compiled pattern when options that changed within the
477        pattern affected the logic of the preliminary scan that determines the
478        length. The relevant options are -x, and -i in UTF-8 mode. The result was
479        that the computed length was too small. The symptoms of this bug were
480        either the PCRE error "internal error: code overflow" from pcre_compile(),
481        or a glibc crash with a message such as "pcretest: free(): invalid next
482        size (fast)". Examples of patterns that provoked this bug (shown in
483        pcretest format) are:
485          /(?-x: )/x
486          /(?x)(?-x: \s*#\s*)/
487          /((?i)[\x{c0}])/8
488          /(?i:[\x{c0}])/8
490        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
491        is now done differently.
493     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
494        wrapper classes; (b) implement a new function in the C++ scanner that is
495        more efficient than the old way of doing things because it avoids levels of
496        recursion in the regex matching; (c) add a paragraph to the documentation
497        for the FullMatch() function.
499     6. The escape sequence \n was being treated as whatever was defined as
500        "newline". Not only was this contrary to the documentation, which states
501        that \n is character 10 (hex 0A), but it also went horribly wrong when
502        "newline" was defined as CRLF. This has been fixed.
504     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
505        was being set to -1 for the "end of line" case (supposedly a value that no
506        character can have). Though this value is never used (the check for end of
507        line is "zero bytes in current character"), it caused compiler complaints.
508        I've changed it to 0xffffffff.
510     8. In pcre_version.c, the version string was being built by a sequence of
511        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
512        string (as it is for production releases) called a macro with an empty
513        argument. The C standard says the result of this is undefined. The gcc
514        compiler treats it as an empty string (which was what was wanted) but it is
515        reported that Visual C gives an error. The source has been hacked around to
516        avoid this problem.
518     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
519        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
520        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
521        of them did).
523    10. Originally, pcretest opened its input and output without "b"; then I was
524        told that "b" was needed in some environments, so it was added for release
525        5.0 to both the input and output. (It makes no difference on Unix-like
526        systems.) Later I was told that it is wrong for the input on Windows. I've
527        now abstracted the modes into two macros, to make it easier to fiddle with
528        them, and removed "b" from the input mode under Windows.
530    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
532    12. Added -help and --help to pcretest as an official way of being reminded
533        of the options.
535    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
536        and pcrecpp.cc because they annoy compilers at high warning levels.
538    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
540    15. Fixed an occurrence of == in configure.ac that should have been = (shell
541        scripts are not C programs :-) and which was not noticed because it works
542        on Linux.
544    16. pcretest is supposed to handle any length of pattern and data line (as one
545        line or as a continued sequence of lines) by extending its input buffer if
546        necessary. This feature was broken for very long pattern lines, leading to
547        a string of junk being passed to pcre_compile() if the pattern was longer
548        than about 50K.
550    17. I have done a major re-factoring of the way pcre_compile() computes the
551        amount of memory needed for a compiled pattern. Previously, there was code
552        that made a preliminary scan of the pattern in order to do this. That was
553        OK when PCRE was new, but as the facilities have expanded, it has become
554        harder and harder to keep it in step with the real compile phase, and there
555        have been a number of bugs (see for example, 4 above). I have now found a
556        cunning way of running the real compile function in a "fake" mode that
557        enables it to compute how much memory it would need, while actually only
558        ever using a few hundred bytes of working memory and without too many
559        tests of the mode. This should make future maintenance and development
560        easier. A side effect of this work is that the limit of 200 on the nesting
561        depth of parentheses has been removed (though this was never a serious
562        limitation, I suspect). However, there is a downside: pcre_compile() now
563        runs more slowly than before (30% or more, depending on the pattern). I
564        hope this isn't a big issue. There is no effect on runtime performance.
566    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
567        newline (only possible for the last line of a file) and it was a
568        pattern that set a locale (followed by /Lsomething), pcretest crashed.
570    19. Added additional timing features to pcretest. (1) The -tm option now times
571        matching only, not compiling. (2) Both -t and -tm can be followed, as a
572        separate command line item, by a number that specifies the number of
573        repeats to use when timing. The default is 50000; this gives better
574        precision, but takes uncomfortably long for very large patterns.
576    20. Extended pcre_study() to be more clever in cases where a branch of a
577        subpattern has no definite first character. For example, (a*|b*)[cd] would
578        previously give no result from pcre_study(). Now it recognizes that the
579        first character must be a, b, c, or d.
581    21. There was an incorrect error "recursive call could loop indefinitely" if
582        a subpattern (or the entire pattern) that was being tested for matching an
583        empty string contained only one non-empty item after a nested subpattern.
584        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
585        incorrectly, because the \d was being skipped in the check.
587    22. The pcretest program now has a new pattern option /B and a command line
588        option -b, which is equivalent to adding /B to every pattern. This causes
589        it to show the compiled bytecode, without the additional information that
590        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
591        is the same as /B/I).
593    23. A new optimization is now able automatically to treat some sequences such
594        as a*b as a*+b. More specifically, if something simple (such as a character
595        or a simple class like \d) has an unlimited quantifier, and is followed by
596        something that cannot possibly match the quantified thing, the quantifier
597        is automatically "possessified".
599    24. A recursive reference to a subpattern whose number was greater than 39
600        went wrong under certain circumstances in UTF-8 mode. This bug could also
601        have affected the operation of pcre_study().
603    25. Realized that a little bit of performance could be had by replacing
604        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
606    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
608    27. Possessive quantifiers such as a++ were previously implemented by turning
609        them into atomic groups such as ($>a+). Now they have their own opcodes,
610        which improves performance. This includes the automatically created ones
611        from 23 above.
613    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
614        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
615        the first matched character to be a colon. This applied both to named and
616        numbered groups.
618    29. The ucpinternal.h header file was missing its idempotency #ifdef.
620    30. I was sent a "project" file called libpcre.a.dev which I understand makes
621        building PCRE on Windows easier, so I have included it in the distribution.
623    31. There is now a check in pcretest against a ridiculously large number being
624        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
625        loop, the loop is abandoned.
627    32. Forward references to subpatterns in conditions such as (?(2)...) where
628        subpattern 2 is defined later cause pcre_compile() to search forwards in
629        the pattern for the relevant set of parentheses. This search went wrong
630        when there were unescaped parentheses in a character class, parentheses
631        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
633    33. "Subroutine" calls and backreferences were previously restricted to
634        referencing subpatterns earlier in the regex. This restriction has now
635        been removed.
637    34. Added a number of extra features that are going to be in Perl 5.10. On the
638        whole, these are just syntactic alternatives for features that PCRE had
639        previously implemented using the Python syntax or my own invention. The
640        other formats are all retained for compatibility.
642        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
643            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
644            also .NET compatible.
646        (b) A recursion or subroutine call to a named group can now be defined as
647            (?&name) as well as (?P>name).
649        (c) A backreference to a named group can now be defined as \k<name> or
650            \k'name' as well as (?P=name). The new forms, as well as being in Perl
651            5.10, are also .NET compatible.
653        (d) A conditional reference to a named group can now use the syntax
654            (?(<name>) or (?('name') as well as (?(name).
656        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
657            groups (named and numbered) that are never evaluated inline, but can be
658            called as "subroutines" from elsewhere. In effect, the DEFINE condition
659            is always false. There may be only one alternative in such a group.
661        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
662            as the simple (?(R). The condition is true only if the most recent
663            recursion is that of the given number or name. It does not search out
664            through the entire recursion stack.
666        (g) The escape \gN or \g{N} has been added, where N is a positive or
667            negative number, specifying an absolute or relative reference.
669    35. Tidied to get rid of some further signed/unsigned compiler warnings and
670        some "unreachable code" warnings.
672    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
673        things, this adds five new scripts.
675    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
676        There were also incompatibilities regarding the handling of \Q..\E inside
677        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
678        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
680    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
681        matches an empty string, and forcibly breaks the loop. There were bugs in
682        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
683        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
684        separate and independent bugs (that affected different cases) have been
685        fixed.
687    39. Refactored the code to abolish the use of different opcodes for small
688        capturing bracket numbers. This is a tidy that I avoided doing when I
689        removed the limit on the number of capturing brackets for 3.5 back in 2001.
690        The new approach is not only tidier, it makes it possible to reduce the
691        memory needed to fix the previous bug (38).
693    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
694        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
695        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
696        mode.
698    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
699        report.
701    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
702        copy construction and assignment in the C++ wrapper.
704    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
705        couple of bugs that could have given wrong results in the "--newline=crlf"
706        case.
708    44. Added a number of casts and did some reorganization of signed/unsigned int
709        variables following suggestions from Dair Grant. Also renamed the variable
710        "this" as "item" because it is a C++ keyword.
712    45. Arranged for dftables to add
714          #include "pcre_internal.h"
716        to pcre_chartables.c because without it, gcc 4.x may remove the array
717        definition from the final binary if PCRE is built into a static library and
718        dead code stripping is activated.
720    46. For an unanchored pattern, if a match attempt fails at the start of a
721        newline sequence, and the newline setting is CRLF or ANY, and the next two
722        characters are CRLF, advance by two characters instead of one.
725    Version 6.7 04-Jul-06
726    ---------------------
728     1. In order to handle tests when input lines are enormously long, pcretest has
729        been re-factored so that it automatically extends its buffers when
730        necessary. The code is crude, but this _is_ just a test program. The
731        default size has been increased from 32K to 50K.
733     2. The code in pcre_study() was using the value of the re argument before
734        testing it for NULL. (Of course, in any sensible call of the function, it
735        won't be NULL.)
737     3. The memmove() emulation function in pcre_internal.h, which is used on
738        systems that lack both memmove() and bcopy() - that is, hardly ever -
739        was missing a "static" storage class specifier.
741     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
742        containing an extended class (one that cannot be represented by a bitmap
743        because it contains high-valued characters or Unicode property items, e.g.
744        [\pZ]). Almost always one would set UTF-8 mode when processing such a
745        pattern, but PCRE should not loop if you do not (it no longer does).
746        [Detail: two cases were found: (a) a repeated subpattern containing an
747        extended class; (b) a recursive reference to a subpattern that followed a
748        previous extended class. It wasn't skipping over the extended class
749        correctly when UTF-8 mode was not set.]
751     5. A negated single-character class was not being recognized as fixed-length
752        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
753        compile error "lookbehind assertion is not fixed length".
755     6. The RunPerlTest auxiliary script was showing an unexpected difference
756        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
757        write a Perl script that can interpret lines of an input file either as
758        byte characters or as UTF-8, which is what "perltest" was being required to
759        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
760        can't do is switch easily at run time between having the "use utf8;" pragma
761        or not. In the end, I fudged it by using the RunPerlTest script to insert
762        "use utf8;" explicitly for the UTF-8 tests.
764     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
765        the end of the subject string, contrary to the documentation and to what
766        Perl does. This was true of both matching functions. Now it matches only at
767        the start of the subject and immediately after *internal* newlines.
769     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
770        a pointer to an int instead of a pointer to an unsigned long int. This
771        caused problems on 64-bit systems.
773     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
774        instance of the 'standard' template library not being so standard".
776    10. There was no check on the number of named subpatterns nor the maximum
777        length of a subpattern name. The product of these values is used to compute
778        the size of the memory block for a compiled pattern. By supplying a very
779        long subpattern name and a large number of named subpatterns, the size
780        computation could be caused to overflow. This is now prevented by limiting
781        the length of names to 32 characters, and the number of named subpatterns
782        to 10,000.
784    11. Subpatterns that are repeated with specific counts have to be replicated in
785        the compiled pattern. The size of memory for this was computed from the
786        length of the subpattern and the repeat count. The latter is limited to
787        65535, but there was no limit on the former, meaning that integer overflow
788        could in principle occur. The compiled length of a repeated subpattern is
789        now limited to 30,000 bytes in order to prevent this.
791    12. Added the optional facility to have named substrings with the same name.
793    13. Added the ability to use a named substring as a condition, using the
794        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
795        are numbers (not recommended). Forward references are permitted.
797    14. Added forward references in named backreferences (if you see what I mean).
799    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
800        pattern could run off the end of the subject. For example, the pattern
801        "(?s)(.{1,5})"8 did this with the subject "ab".
803    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
804        PCRE_CASELESS was set when matching characters that were quantified with ?
805        or *.
807    17. A character class other than a single negated character that had a minimum
808        but no maximum quantifier - for example [ab]{6,} - was not handled
809        correctly by pce_dfa_exec(). It would match only one character.
811    18. A valid (though odd) pattern that looked like a POSIX character
812        class but used an invalid character after [ (for example [[,abc,]]) caused
813        pcre_compile() to give the error "Failed: internal error: code overflow" or
814        in some cases to crash with a glibc free() error. This could even happen if
815        the pattern terminated after [[ but there just happened to be a sequence of
816        letters, a binary zero, and a closing ] in the memory that followed.
818    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
819        over the years. Originally (before any Unicode support), just the bottom 8
820        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
821        output from "man perlunicode" includes this:
823          The regular expression compiler produces polymorphic opcodes.  That
824          is, the pattern adapts to the data and automatically switches to
825          the Unicode character scheme when presented with Unicode data--or
826          instead uses a traditional byte scheme when presented with byte
827          data.
829        Sadly, a wide octal escape does not cause a switch, and in a string with
830        no other multibyte characters, these octal escapes are treated as before.
831        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
832        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
833        Unicode string.
835        I have not perpetrated such confusion in PCRE. Up till now, it took just
836        the bottom 8 bits, as in old Perl. I have now made octal escapes with
837        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
838        translate to the appropriate multibyte character.
840    29. Applied some refactoring to reduce the number of warnings from Microsoft
841        and Borland compilers. This has included removing the fudge introduced
842        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
843        a warning about an unused variable.
845    21. PCRE has not included VT (character 0x0b) in the set of whitespace
846        characters since release 4.0, because Perl (from release 5.004) does not.
847        [Or at least, is documented not to: some releases seem to be in conflict
848        with the documentation.] However, when a pattern was studied with
849        pcre_study() and all its branches started with \s, PCRE still included VT
850        as a possible starting character. Of course, this did no harm; it just
851        caused an unnecessary match attempt.
853    22. Removed a now-redundant internal flag bit that recorded the fact that case
854        dependency changed within the pattern. This was once needed for "required
855        byte" processing, but is no longer used. This recovers a now-scarce options
856        bit. Also moved the least significant internal flag bit to the most-
857        significant bit of the word, which was not previously used (hangover from
858        the days when it was an int rather than a uint) to free up another bit for
859        the future.
861    23. Added support for CRLF line endings as well as CR and LF. As well as the
862        default being selectable at build time, it can now be changed at runtime
863        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
864        specify that it is scanning data with non-default line endings.
866    24. Changed the definition of CXXLINK to make it agree with the definition of
867        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
869    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
870        recursions. This makes a big different to stack usage for some patterns.
872    26. If a subpattern containing a named recursion or subroutine reference such
873        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
874        the space required for the compiled pattern went wrong and gave too small a
875        value. Depending on the environment, this could lead to "Failed: internal
876        error: code overflow at offset 49" or "glibc detected double free or
877        corruption" errors.
879    27. Applied patches from Google (a) to support the new newline modes and (b) to
880        advance over multibyte UTF-8 characters in GlobalReplace.
882    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
883        difference for some implementation of PCRE in some Windows version.
885    29. Added some extra testing facilities to pcretest:
887        \q<number>   in a data line sets the "match limit" value
888        \Q<number>   in a data line sets the "match recursion limt" value
889        -S <number>  sets the stack size, where <number> is in megabytes
891        The -S option isn't available for Windows.
894  Version 6.6 06-Feb-06  Version 6.6 06-Feb-06
895  ---------------------  ---------------------

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