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revision 87 by nigel, Sat Feb 24 21:41:21 2007 UTC revision 344 by ph10, Tue Apr 22 09:16:15 2008 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
4    Version 7.7 05-Mar-08
5    ---------------------
7    1.  Applied Craig's patch to sort out a long long problem: "If we can't convert
8        a string to a long long, pretend we don't even have a long long." This is
9        done by checking for the strtoq, strtoll, and _strtoi64 functions.
11    2.  Applied Craig's patch to pcrecpp.cc to restore ABI compatibility with
12        pre-7.6 versions, which defined a global no_arg variable instead of putting
13        it in the RE class. (See also #8 below.)
15    3.  Remove a line of dead code, identified by coverity and reported by Nuno
16        Lopes.
18    4.  Fixed two related pcregrep bugs involving -r with --include or --exclude:
20        (1) The include/exclude patterns were being applied to the whole pathnames
21            of files, instead of just to the final components.
23        (2) If there was more than one level of directory, the subdirectories were
24            skipped unless they satisfied the include/exclude conditions. This is
25            inconsistent with GNU grep (and could even be seen as contrary to the
26            pcregrep specification - which I improved to make it absolutely clear).
27            The action now is always to scan all levels of directory, and just
28            apply the include/exclude patterns to regular files.
30    5.  Added the --include_dir and --exclude_dir patterns to pcregrep, and used
31        --exclude_dir in the tests to avoid scanning .svn directories.
33    6.  Applied Craig's patch to the QuoteMeta function so that it escapes the
34        NUL character as backslash + 0 rather than backslash + NUL, because PCRE
35        doesn't support NULs in patterns.
37    7.  Added some missing "const"s to declarations of static tables in
38        pcre_compile.c and pcre_dfa_exec.c.
40    8.  Applied Craig's patch to pcrecpp.cc to fix a problem in OS X that was
41        caused by fix #2  above. (Subsequently also a second patch to fix the
42        first patch. And a third patch - this was a messy problem.)
44    9.  Applied Craig's patch to remove the use of push_back().
46    10. Applied Alan Lehotsky's patch to add REG_STARTEND support to the POSIX
47        matching function regexec().
49    11. Added support for the Oniguruma syntax \g<name>, \g<n>, \g'name', \g'n',
50        which, however, unlike Perl's \g{...}, are subroutine calls, not back
51        references. PCRE supports relative numbers with this syntax (I don't think
52        Oniguruma does).
54    12. Previously, a group with a zero repeat such as (...){0} was completely
55        omitted from the compiled regex. However, this means that if the group
56        was called as a subroutine from elsewhere in the pattern, things went wrong
57        (an internal error was given). Such groups are now left in the compiled
58        pattern, with a new opcode that causes them to be skipped at execution
59        time.
61    13. Added the PCRE_JAVASCRIPT_COMPAT option. This makes the following changes
62        to the way PCRE behaves:
64        (a) A lone ] character is dis-allowed (Perl treats it as data).
66        (b) A back reference to an unmatched subpattern matches an empty string
67            (Perl fails the current match path).
69        (c) A data ] in a character class must be notated as \] because if the
70            first data character in a class is ], it defines an empty class. (In
71            Perl it is not possible to have an empty class.) The empty class []
72            never matches; it forces failure and is equivalent to (*FAIL) or (?!).
73            The negative empty class [^] matches any one character, independently
74            of the DOTALL setting.
76    14. A pattern such as /(?2)[]a()b](abc)/ which had a forward reference to a
77        non-existent subpattern following a character class starting with ']' and
78        containing () gave an internal compiling error instead of "reference to
79        non-existent subpattern". Fortunately, when the pattern did exist, the
80        compiled code was correct. (When scanning forwards to check for the
81        existencd of the subpattern, it was treating the data ']' as terminating
82        the class, so got the count wrong. When actually compiling, the reference
83        was subsequently set up correctly.)
85    15. The "always fail" assertion (?!) is optimzed to (*FAIL) by pcre_compile;
86        it was being rejected as not supported by pcre_dfa_exec(), even though
87        other assertions are supported. I have made pcre_dfa_exec() support
88        (*FAIL).
90    16. The implementation of 13c above involved the invention of a new opcode,
91        OP_ALLANY, which is like OP_ANY but doesn't check the /s flag. Since /s
92        cannot be changed at match time, I realized I could make a small
93        improvement to matching performance by compiling OP_ALLANY instead of
94        OP_ANY for "." when DOTALL was set, and then removing the runtime tests
95        on the OP_ANY path.
97    17. Compiling pcretest on Windows with readline support failed without the
98        following two fixes: (1) Make the unistd.h include conditional on
99        HAVE_UNISTD_H; (2) #define isatty and fileno as _isatty and _fileno.
101    18. Changed CMakeLists.txt and cmake/FindReadline.cmake to arrange for the
102        ncurses library to be included for pcretest when ReadLine support is
103        requested, but also to allow for it to be overridden. This patch came from
104        Daniel Bergström.
107    Version 7.6 28-Jan-08
108    ---------------------
110    1.  A character class containing a very large number of characters with
111        codepoints greater than 255 (in UTF-8 mode, of course) caused a buffer
112        overflow.
114    2.  Patch to cut out the "long long" test in pcrecpp_unittest when
115        HAVE_LONG_LONG is not defined.
117    3.  Applied Christian Ehrlicher's patch to update the CMake build files to
118        bring them up to date and include new features. This patch includes:
120        - Fixed PH's badly added libz and libbz2 support.
121        - Fixed a problem with static linking.
122        - Added pcredemo. [But later removed - see 7 below.]
123        - Fixed dftables problem and added an option.
124        - Added a number of HAVE_XXX tests, including HAVE_WINDOWS_H and
125            HAVE_LONG_LONG.
126        - Added readline support for pcretest.
127        - Added an listing of the option settings after cmake has run.
129    4.  A user submitted a patch to Makefile that makes it easy to create
130        "pcre.dll" under mingw when using Configure/Make. I added stuff to
131        Makefile.am that cause it to include this special target, without
132        affecting anything else. Note that the same mingw target plus all
133        the other distribution libraries and programs are now supported
134        when configuring with CMake (see 6 below) instead of with
135        Configure/Make.
137    5.  Applied Craig's patch that moves no_arg into the RE class in the C++ code.
138        This is an attempt to solve the reported problem "pcrecpp::no_arg is not
139        exported in the Windows port". It has not yet been confirmed that the patch
140        solves the problem, but it does no harm.
142    6.  Applied Sheri's patch to CMakeLists.txt to add NON_STANDARD_LIB_PREFIX and
143        NON_STANDARD_LIB_SUFFIX for dll names built with mingw when configured
144        with CMake, and also correct the comment about stack recursion.
146    7.  Remove the automatic building of pcredemo from the ./configure system and
147        from CMakeLists.txt. The whole idea of pcredemo.c is that it is an example
148        of a program that users should build themselves after PCRE is installed, so
149        building it automatically is not really right. What is more, it gave
150        trouble in some build environments.
152    8.  Further tidies to CMakeLists.txt from Sheri and Christian.
155    Version 7.5 10-Jan-08
156    ---------------------
158    1.  Applied a patch from Craig: "This patch makes it possible to 'ignore'
159        values in parens when parsing an RE using the C++ wrapper."
161    2.  Negative specials like \S did not work in character classes in UTF-8 mode.
162        Characters greater than 255 were excluded from the class instead of being
163        included.
165    3.  The same bug as (2) above applied to negated POSIX classes such as
166        [:^space:].
168    4.  PCRECPP_STATIC was referenced in pcrecpp_internal.h, but nowhere was it
169        defined or documented. It seems to have been a typo for PCRE_STATIC, so
170        I have changed it.
172    5.  The construct (?&) was not diagnosed as a syntax error (it referenced the
173        first named subpattern) and a construct such as (?&a) would reference the
174        first named subpattern whose name started with "a" (in other words, the
175        length check was missing). Both these problems are fixed. "Subpattern name
176        expected" is now given for (?&) (a zero-length name), and this patch also
177        makes it give the same error for \k'' (previously it complained that that
178        was a reference to a non-existent subpattern).
180    6.  The erroneous patterns (?+-a) and (?-+a) give different error messages;
181        this is right because (?- can be followed by option settings as well as by
182        digits. I have, however, made the messages clearer.
184    7.  Patterns such as (?(1)a|b) (a pattern that contains fewer subpatterns
185        than the number used in the conditional) now cause a compile-time error.
186        This is actually not compatible with Perl, which accepts such patterns, but
187        treats the conditional as always being FALSE (as PCRE used to), but it
188        seems to me that giving a diagnostic is better.
190    8.  Change "alphameric" to the more common word "alphanumeric" in comments
191        and messages.
193    9.  Fix two occurrences of "backslash" in comments that should have been
194        "backspace".
196    10. Remove two redundant lines of code that can never be obeyed (their function
197        was moved elsewhere).
199    11. The program that makes PCRE's Unicode character property table had a bug
200        which caused it to generate incorrect table entries for sequences of
201        characters that have the same character type, but are in different scripts.
202        It amalgamated them into a single range, with the script of the first of
203        them. In other words, some characters were in the wrong script. There were
204        thirteen such cases, affecting characters in the following ranges:
206          U+002b0 - U+002c1
207          U+0060c - U+0060d
208          U+0061e - U+00612
209          U+0064b - U+0065e
210          U+0074d - U+0076d
211          U+01800 - U+01805
212          U+01d00 - U+01d77
213          U+01d9b - U+01dbf
214          U+0200b - U+0200f
215          U+030fc - U+030fe
216          U+03260 - U+0327f
217          U+0fb46 - U+0fbb1
218          U+10450 - U+1049d
220    12. The -o option (show only the matching part of a line) for pcregrep was not
221        compatible with GNU grep in that, if there was more than one match in a
222        line, it showed only the first of them. It now behaves in the same way as
223        GNU grep.
225    13. If the -o and -v options were combined for pcregrep, it printed a blank
226        line for every non-matching line. GNU grep prints nothing, and pcregrep now
227        does the same. The return code can be used to tell if there were any
228        non-matching lines.
230    14. Added --file-offsets and --line-offsets to pcregrep.
232    15. The pattern (?=something)(?R) was not being diagnosed as a potentially
233        infinitely looping recursion. The bug was that positive lookaheads were not
234        being skipped when checking for a possible empty match (negative lookaheads
235        and both kinds of lookbehind were skipped).
237    16. Fixed two typos in the Windows-only code in pcregrep.c, and moved the
238        inclusion of <windows.h> to before rather than after the definition of
239        INVALID_FILE_ATTRIBUTES (patch from David Byron).
241    17. Specifying a possessive quantifier with a specific limit for a Unicode
242        character property caused pcre_compile() to compile bad code, which led at
243        runtime to PCRE_ERROR_INTERNAL (-14). Examples of patterns that caused this
244        are: /\p{Zl}{2,3}+/8 and /\p{Cc}{2}+/8. It was the possessive "+" that
245        caused the error; without that there was no problem.
247    18. Added --enable-pcregrep-libz and --enable-pcregrep-libbz2.
249    19. Added --enable-pcretest-libreadline.
251    20. In pcrecpp.cc, the variable 'count' was incremented twice in
252        RE::GlobalReplace(). As a result, the number of replacements returned was
253        double what it should be. I removed one of the increments, but Craig sent a
254        later patch that removed the other one (the right fix) and added unit tests
255        that check the return values (which was not done before).
257    21. Several CMake things:
259        (1) Arranged that, when cmake is used on Unix, the libraries end up with
260            the names libpcre and libpcreposix, not just pcre and pcreposix.
262        (2) The above change means that pcretest and pcregrep are now correctly
263            linked with the newly-built libraries, not previously installed ones.
267    22. In UTF-8 mode, with newline set to "any", a pattern such as .*a.*=.b.*
268        crashed when matching a string such as a\x{2029}b (note that \x{2029} is a
269        UTF-8 newline character). The key issue is that the pattern starts .*;
270        this means that the match must be either at the beginning, or after a
271        newline. The bug was in the code for advancing after a failed match and
272        checking that the new position followed a newline. It was not taking
273        account of UTF-8 characters correctly.
275    23. PCRE was behaving differently from Perl in the way it recognized POSIX
276        character classes. PCRE was not treating the sequence [:...:] as a
277        character class unless the ... were all letters. Perl, however, seems to
278        allow any characters between [: and :], though of course it rejects as
279        unknown any "names" that contain non-letters, because all the known class
280        names consist only of letters. Thus, Perl gives an error for [[:1234:]],
281        for example, whereas PCRE did not - it did not recognize a POSIX character
282        class. This seemed a bit dangerous, so the code has been changed to be
283        closer to Perl. The behaviour is not identical to Perl, because PCRE will
284        diagnose an unknown class for, for example, [[:l\ower:]] where Perl will
285        treat it as [[:lower:]]. However, PCRE does now give "unknown" errors where
286        Perl does, and where it didn't before.
288    24. Rewrite so as to remove the single use of %n from pcregrep because in some
289        Windows environments %n is disabled by default.
292    Version 7.4 21-Sep-07
293    ---------------------
295    1.  Change 7.3/28 was implemented for classes by looking at the bitmap. This
296        means that a class such as [\s] counted as "explicit reference to CR or
297        LF". That isn't really right - the whole point of the change was to try to
298        help when there was an actual mention of one of the two characters. So now
299        the change happens only if \r or \n (or a literal CR or LF) character is
300        encountered.
302    2.  The 32-bit options word was also used for 6 internal flags, but the numbers
303        of both had grown to the point where there were only 3 bits left.
304        Fortunately, there was spare space in the data structure, and so I have
305        moved the internal flags into a new 16-bit field to free up more option
306        bits.
308    3.  The appearance of (?J) at the start of a pattern set the DUPNAMES option,
309        but did not set the internal JCHANGED flag - either of these is enough to
310        control the way the "get" function works - but the PCRE_INFO_JCHANGED
311        facility is supposed to tell if (?J) was ever used, so now (?J) at the
312        start sets both bits.
314    4.  Added options (at build time, compile time, exec time) to change \R from
315        matching any Unicode line ending sequence to just matching CR, LF, or CRLF.
317    5.  doc/pcresyntax.html was missing from the distribution.
319    6.  Put back the definition of PCRE_ERROR_NULLWSLIMIT, for backward
320        compatibility, even though it is no longer used.
322    7.  Added macro for snprintf to pcrecpp_unittest.cc and also for strtoll and
323        strtoull to pcrecpp.cc to select the available functions in WIN32 when the
324        windows.h file is present (where different names are used). [This was
325        reversed later after testing - see 16 below.]
327    8.  Changed all #include <config.h> to #include "config.h". There were also
328        some further <pcre.h> cases that I changed to "pcre.h".
330    9.  When pcregrep was used with the --colour option, it missed the line ending
331        sequence off the lines that it output.
333    10. It was pointed out to me that arrays of string pointers cause lots of
334        relocations when a shared library is dynamically loaded. A technique of
335        using a single long string with a table of offsets can drastically reduce
336        these. I have refactored PCRE in four places to do this. The result is
337        dramatic:
339          Originally:                          290
340          After changing UCP table:            187
341          After changing error message table:   43
342          After changing table of "verbs"       36
343          After changing table of Posix names   22
345        Thanks to the folks working on Gregex for glib for this insight.
347    11. --disable-stack-for-recursion caused compiling to fail unless -enable-
348        unicode-properties was also set.
350    12. Updated the tests so that they work when \R is defaulted to ANYCRLF.
352    13. Added checks for ANY and ANYCRLF to pcrecpp.cc where it previously
353        checked only for CRLF.
355    14. Added casts to pcretest.c to avoid compiler warnings.
357    15. Added Craig's patch to various pcrecpp modules to avoid compiler warnings.
359    16. Added Craig's patch to remove the WINDOWS_H tests, that were not working,
360        and instead check for _strtoi64 explicitly, and avoid the use of snprintf()
361        entirely. This removes changes made in 7 above.
363    17. The CMake files have been updated, and there is now more information about
364        building with CMake in the NON-UNIX-USE document.
367    Version 7.3 28-Aug-07
368    ---------------------
370     1. In the rejigging of the build system that eventually resulted in 7.1, the
371        line "#include <pcre.h>" was included in pcre_internal.h. The use of angle
372        brackets there is not right, since it causes compilers to look for an
373        installed pcre.h, not the version that is in the source that is being
374        compiled (which of course may be different). I have changed it back to:
376          #include "pcre.h"
378        I have a vague recollection that the change was concerned with compiling in
379        different directories, but in the new build system, that is taken care of
380        by the VPATH setting the Makefile.
382     2. The pattern .*$ when run in not-DOTALL UTF-8 mode with newline=any failed
383        when the subject happened to end in the byte 0x85 (e.g. if the last
384        character was \x{1ec5}). *Character* 0x85 is one of the "any" newline
385        characters but of course it shouldn't be taken as a newline when it is part
386        of another character. The bug was that, for an unlimited repeat of . in
387        not-DOTALL UTF-8 mode, PCRE was advancing by bytes rather than by
388        characters when looking for a newline.
390     3. A small performance improvement in the DOTALL UTF-8 mode .* case.
392     4. Debugging: adjusted the names of opcodes for different kinds of parentheses
393        in debug output.
395     5. Arrange to use "%I64d" instead of "%lld" and "%I64u" instead of "%llu" for
396        long printing in the pcrecpp unittest when running under MinGW.
398     6. ESC_K was left out of the EBCDIC table.
400     7. Change 7.0/38 introduced a new limit on the number of nested non-capturing
401        parentheses; I made it 1000, which seemed large enough. Unfortunately, the
402        limit also applies to "virtual nesting" when a pattern is recursive, and in
403        this case 1000 isn't so big. I have been able to remove this limit at the
404        expense of backing off one optimization in certain circumstances. Normally,
405        when pcre_exec() would call its internal match() function recursively and
406        immediately return the result unconditionally, it uses a "tail recursion"
407        feature to save stack. However, when a subpattern that can match an empty
408        string has an unlimited repetition quantifier, it no longer makes this
409        optimization. That gives it a stack frame in which to save the data for
410        checking that an empty string has been matched. Previously this was taken
411        from the 1000-entry workspace that had been reserved. So now there is no
412        explicit limit, but more stack is used.
414     8. Applied Daniel's patches to solve problems with the import/export magic
415        syntax that is required for Windows, and which was going wrong for the
416        pcreposix and pcrecpp parts of the library. These were overlooked when this
417        problem was solved for the main library.
419     9. There were some crude static tests to avoid integer overflow when computing
420        the size of patterns that contain repeated groups with explicit upper
421        limits. As the maximum quantifier is 65535, the maximum group length was
422        set at 30,000 so that the product of these two numbers did not overflow a
423        32-bit integer. However, it turns out that people want to use groups that
424        are longer than 30,000 bytes (though not repeat them that many times).
425        Change 7.0/17 (the refactoring of the way the pattern size is computed) has
426        made it possible to implement the integer overflow checks in a much more
427        dynamic way, which I have now done. The artificial limitation on group
428        length has been removed - we now have only the limit on the total length of
429        the compiled pattern, which depends on the LINK_SIZE setting.
431    10. Fixed a bug in the documentation for get/copy named substring when
432        duplicate names are permitted. If none of the named substrings are set, the
433        functions return PCRE_ERROR_NOSUBSTRING (7); the doc said they returned an
434        empty string.
436    11. Because Perl interprets \Q...\E at a high level, and ignores orphan \E
437        instances, patterns such as [\Q\E] or [\E] or even [^\E] cause an error,
438        because the ] is interpreted as the first data character and the
439        terminating ] is not found. PCRE has been made compatible with Perl in this
440        regard. Previously, it interpreted [\Q\E] as an empty class, and [\E] could
441        cause memory overwriting.
443    10. Like Perl, PCRE automatically breaks an unlimited repeat after an empty
444        string has been matched (to stop an infinite loop). It was not recognizing
445        a conditional subpattern that could match an empty string if that
446        subpattern was within another subpattern. For example, it looped when
447        trying to match  (((?(1)X|))*)  but it was OK with  ((?(1)X|)*)  where the
448        condition was not nested. This bug has been fixed.
450    12. A pattern like \X?\d or \P{L}?\d in non-UTF-8 mode could cause a backtrack
451        past the start of the subject in the presence of bytes with the top bit
452        set, for example "\x8aBCD".
454    13. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
455        (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
457    14. Optimized (?!) to (*FAIL).
459    15. Updated the test for a valid UTF-8 string to conform to the later RFC 3629.
460        This restricts code points to be within the range 0 to 0x10FFFF, excluding
461        the "low surrogate" sequence 0xD800 to 0xDFFF. Previously, PCRE allowed the
462        full range 0 to 0x7FFFFFFF, as defined by RFC 2279. Internally, it still
463        does: it's just the validity check that is more restrictive.
465    16. Inserted checks for integer overflows during escape sequence (backslash)
466        processing, and also fixed erroneous offset values for syntax errors during
467        backslash processing.
469    17. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
470        for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
472    18. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
473        caused an overrun.
475    19. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
476        something other than just ASCII characters) inside a group that had an
477        unlimited repeat caused a loop at compile time (while checking to see
478        whether the group could match an empty string).
480    20. Debugging a pattern containing \p or \P could cause a crash. For example,
481        [\P{Any}] did so. (Error in the code for printing property names.)
483    21. An orphan \E inside a character class could cause a crash.
485    22. A repeated capturing bracket such as (A)? could cause a wild memory
486        reference during compilation.
488    23. There are several functions in pcre_compile() that scan along a compiled
489        expression for various reasons (e.g. to see if it's fixed length for look
490        behind). There were bugs in these functions when a repeated \p or \P was
491        present in the pattern. These operators have additional parameters compared
492        with \d, etc, and these were not being taken into account when moving along
493        the compiled data. Specifically:
495        (a) A item such as \p{Yi}{3} in a lookbehind was not treated as fixed
496            length.
498        (b) An item such as \pL+ within a repeated group could cause crashes or
499            loops.
501        (c) A pattern such as \p{Yi}+(\P{Yi}+)(?1) could give an incorrect
502            "reference to non-existent subpattern" error.
504        (d) A pattern like (\P{Yi}{2}\277)? could loop at compile time.
506    24. A repeated \S or \W in UTF-8 mode could give wrong answers when multibyte
507        characters were involved (for example /\S{2}/8g with "A\x{a3}BC").
509    25. Using pcregrep in multiline, inverted mode (-Mv) caused it to loop.
511    26. Patterns such as [\P{Yi}A] which include \p or \P and just one other
512        character were causing crashes (broken optimization).
514    27. Patterns such as (\P{Yi}*\277)* (group with possible zero repeat containing
515        \p or \P) caused a compile-time loop.
517    28. More problems have arisen in unanchored patterns when CRLF is a valid line
518        break. For example, the unstudied pattern [\r\n]A does not match the string
519        "\r\nA" because change 7.0/46 below moves the current point on by two
520        characters after failing to match at the start. However, the pattern \nA
521        *does* match, because it doesn't start till \n, and if [\r\n]A is studied,
522        the same is true. There doesn't seem any very clean way out of this, but
523        what I have chosen to do makes the common cases work: PCRE now takes note
524        of whether there can be an explicit match for \r or \n anywhere in the
525        pattern, and if so, 7.0/46 no longer applies. As part of this change,
526        there's a new PCRE_INFO_HASCRORLF option for finding out whether a compiled
527        pattern has explicit CR or LF references.
529    29. Added (*CR) etc for changing newline setting at start of pattern.
532    Version 7.2 19-Jun-07
533    ---------------------
535     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
536        which is apparently normally available under Windows.
538     2. Re-jig the pcregrep tests with different newline settings in an attempt
539        to make them independent of the local environment's newline setting.
541     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
543     4. Some of the "internals" tests were previously cut out when the link size
544        was not 2, because the output contained actual offsets. The recent new
545        "Z" feature of pcretest means that these can be cut out, making the tests
546        usable with all link sizes.
548     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
549        stack recursion. This gives a massive performance boost under BSD, but just
550        a small improvement under Linux. However, it saves one field in the frame
551        in all cases.
553     6. Added more features from the forthcoming Perl 5.10:
555        (a) (?-n) (where n is a string of digits) is a relative subroutine or
556            recursion call. It refers to the nth most recently opened parentheses.
558        (b) (?+n) is also a relative subroutine call; it refers to the nth next
559            to be opened parentheses.
561        (c) Conditions that refer to capturing parentheses can be specified
562            relatively, for example, (?(-2)... or (?(+3)...
564        (d) \K resets the start of the current match so that everything before
565            is not part of it.
567        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
569        (f) \g{name} is another synonym - part of Perl 5.10's unification of
570            reference syntax.
572        (g) (?| introduces a group in which the numbering of parentheses in each
573            alternative starts with the same number.
575        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
577     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
580     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
581        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
582        for detecting groups that can match an empty string.
584     9. A pattern with a very large number of alternatives (more than several
585        hundred) was running out of internal workspace during the pre-compile
586        phase, where pcre_compile() figures out how much memory will be needed. A
587        bit of new cunning has reduced the workspace needed for groups with
588        alternatives. The 1000-alternative test pattern now uses 12 bytes of
589        workspace instead of running out of the 4096 that are available.
591    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
593    11. Applied patch from Google to remove an optimization that didn't quite work.
594        The report of the bug said:
596          pcrecpp::RE("a*").FullMatch("aaa") matches, while
597          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
598          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
600    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
601        it matched the wrong number of bytes.
604    Version 7.1 24-Apr-07
605    ---------------------
607     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
608        that is more "standard", making use of automake and other Autotools. There
609        is some re-arrangement of the files and adjustment of comments consequent
610        on this.
612     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
613        for recursive directory scanning broke on some systems because the files
614        are not scanned in any specific order and on different systems the order
615        was different. A call to "sort" has been inserted into RunGrepTest for the
616        approprate test as a short-term fix. In the longer term there may be an
617        alternative.
619     3. I had an email from Eric Raymond about problems translating some of PCRE's
620        man pages to HTML (despite the fact that I distribute HTML pages, some
621        people do their own conversions for various reasons). The problems
622        concerned the use of low-level troff macros .br and .in. I have therefore
623        removed all such uses from the man pages (some were redundant, some could
624        be replaced by .nf/.fi pairs). The 132html script that I use to generate
625        HTML has been updated to handle .nf/.fi and to complain if it encounters
626        .br or .in.
628     4. Updated comments in configure.ac that get placed in config.h.in and also
629        arranged for config.h to be included in the distribution, with the name
630        config.h.generic, for the benefit of those who have to compile without
631        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
633     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
634        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
635        makevp.bat for the current PCRE, using the additional files
636        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
638     6. A Windows user reported a minor discrepancy with test 2, which turned out
639        to be caused by a trailing space on an input line that had got lost in his
640        copy. The trailing space was an accident, so I've just removed it.
642     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
643        that is needed.
645     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
646        as "const" (a) because they are and (b) because it helps the PHP
647        maintainers who have recently made a script to detect big data structures
648        in the php code that should be moved to the .rodata section. I remembered
649        to update Builducptable as well, so it won't revert if ucptable.h is ever
650        re-created.
652     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
653        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
654        order to be able to cut out the UTF-8 tables in the latter when UTF-8
655        support is not required. This saves 1.5-2K of code, which is important in
656        some applications.
658        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
659        so as not to refer to the tables, even though these functions will never be
660        called when UTF-8 support is disabled. Otherwise there are problems with a
661        shared library.
663    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
665        (a) It was defining its arguments as char * instead of void *.
667        (b) It was assuming that all moves were upwards in memory; this was true
668            a long time ago when I wrote it, but is no longer the case.
670        The emulated memove() is provided for those environments that have neither
671        memmove() nor bcopy(). I didn't think anyone used it these days, but that
672        is clearly not the case, as these two bugs were recently reported.
674    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
675        and Detrail to create the HTML documentation, the .txt form of the man
676        pages, and it removes trailing spaces from listed files. It also creates
677        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
678        case, it wraps all the #defines with #ifndefs. This script should be run
679        before "make dist".
681    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
682        with Unicode property support.
684        (a) For a maximizing quantifier, if the two different cases of the
685            character were of different lengths in their UTF-8 codings (there are
686            some cases like this - I found 11), and the matching function had to
687            back up over a mixture of the two cases, it incorrectly assumed they
688            were both the same length.
690        (b) When PCRE was configured to use the heap rather than the stack for
691            recursion during matching, it was not correctly preserving the data for
692            the other case of a UTF-8 character when checking ahead for a match
693            while processing a minimizing repeat. If the check also involved
694            matching a wide character, but failed, corruption could cause an
695            erroneous result when trying to check for a repeat of the original
696            character.
698    13. Some tidying changes to the testing mechanism:
700        (a) The RunTest script now detects the internal link size and whether there
701            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
702            values substituted by "configure". (The RunGrepTest script already did
703            this for UTF-8.) The configure.ac script no longer substitutes the
704            relevant variables.
706        (b) The debugging options /B and /D in pcretest show the compiled bytecode
707            with length and offset values. This means that the output is different
708            for different internal link sizes. Test 2 is skipped for link sizes
709            other than 2 because of this, bypassing the problem. Unfortunately,
710            there was also a test in test 3 (the locale tests) that used /B and
711            failed for link sizes other than 2. Rather than cut the whole test out,
712            I have added a new /Z option to pcretest that replaces the length and
713            offset values with spaces. This is now used to make test 3 independent
714            of link size. (Test 2 will be tidied up later.)
716    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
717        segmentation fault instead of returning the appropriate error message.
719    15. In multiline mode when the newline sequence was set to "any", the pattern
720        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
721        This doesn't seem right; it now treats the CRLF combination as the line
722        ending, and so does not match in that case. It's only a pattern such as ^$
723        that would hit this one: something like ^ABC$ would have failed after \r
724        and then tried again after \r\n.
726    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
727        in an attempt to make files that differ only in their line terminators
728        compare equal. This works on Linux.
730    17. Under certain error circumstances pcregrep might try to free random memory
731        as it exited. This is now fixed, thanks to valgrind.
733    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
734        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
735        was because its rules for how to advance for /g after matching an empty
736        string at the end of a line did not allow for this case. They now check for
737        it specially.
739    20. pcretest is supposed to handle patterns and data of any length, by
740        extending its buffers when necessary. It was getting this wrong when the
741        buffer for a data line had to be extended.
743    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
744        CRLF as a newline sequence.
746    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
747        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
748        I have nevertheless tidied it up.
750    23. Added some casts to kill warnings from HP-UX ia64 compiler.
752    24. Added a man page for pcre-config.
755    Version 7.0 19-Dec-06
756    ---------------------
758     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
759        moving to gcc 4.1.1.
761     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
762        sys/time.h, which is documented as needed for this function. It doesn't
763        seem to matter on Linux, but it showed up on some releases of OS X.
765     3. It seems that there are systems where bytes whose values are greater than
766        127 match isprint() in the "C" locale. The "C" locale should be the
767        default when a C program starts up. In most systems, only ASCII printing
768        characters match isprint(). This difference caused the output from pcretest
769        to vary, making some of the tests fail. I have changed pcretest so that:
771        (a) When it is outputting text in the compiled version of a pattern, bytes
772            other than 32-126 are always shown as hex escapes.
774        (b) When it is outputting text that is a matched part of a subject string,
775            it does the same, unless a different locale has been set for the match
776            (using the /L modifier). In this case, it uses isprint() to decide.
778     4. Fixed a major bug that caused incorrect computation of the amount of memory
779        required for a compiled pattern when options that changed within the
780        pattern affected the logic of the preliminary scan that determines the
781        length. The relevant options are -x, and -i in UTF-8 mode. The result was
782        that the computed length was too small. The symptoms of this bug were
783        either the PCRE error "internal error: code overflow" from pcre_compile(),
784        or a glibc crash with a message such as "pcretest: free(): invalid next
785        size (fast)". Examples of patterns that provoked this bug (shown in
786        pcretest format) are:
788          /(?-x: )/x
789          /(?x)(?-x: \s*#\s*)/
790          /((?i)[\x{c0}])/8
791          /(?i:[\x{c0}])/8
793        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
794        is now done differently.
796     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
797        wrapper classes; (b) implement a new function in the C++ scanner that is
798        more efficient than the old way of doing things because it avoids levels of
799        recursion in the regex matching; (c) add a paragraph to the documentation
800        for the FullMatch() function.
802     6. The escape sequence \n was being treated as whatever was defined as
803        "newline". Not only was this contrary to the documentation, which states
804        that \n is character 10 (hex 0A), but it also went horribly wrong when
805        "newline" was defined as CRLF. This has been fixed.
807     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
808        was being set to -1 for the "end of line" case (supposedly a value that no
809        character can have). Though this value is never used (the check for end of
810        line is "zero bytes in current character"), it caused compiler complaints.
811        I've changed it to 0xffffffff.
813     8. In pcre_version.c, the version string was being built by a sequence of
814        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
815        string (as it is for production releases) called a macro with an empty
816        argument. The C standard says the result of this is undefined. The gcc
817        compiler treats it as an empty string (which was what was wanted) but it is
818        reported that Visual C gives an error. The source has been hacked around to
819        avoid this problem.
821     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
822        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
823        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
824        of them did).
826    10. Originally, pcretest opened its input and output without "b"; then I was
827        told that "b" was needed in some environments, so it was added for release
828        5.0 to both the input and output. (It makes no difference on Unix-like
829        systems.) Later I was told that it is wrong for the input on Windows. I've
830        now abstracted the modes into two macros, to make it easier to fiddle with
831        them, and removed "b" from the input mode under Windows.
833    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
835    12. Added -help and --help to pcretest as an official way of being reminded
836        of the options.
838    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
839        and pcrecpp.cc because they annoy compilers at high warning levels.
841    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
843    15. Fixed an occurrence of == in configure.ac that should have been = (shell
844        scripts are not C programs :-) and which was not noticed because it works
845        on Linux.
847    16. pcretest is supposed to handle any length of pattern and data line (as one
848        line or as a continued sequence of lines) by extending its input buffer if
849        necessary. This feature was broken for very long pattern lines, leading to
850        a string of junk being passed to pcre_compile() if the pattern was longer
851        than about 50K.
853    17. I have done a major re-factoring of the way pcre_compile() computes the
854        amount of memory needed for a compiled pattern. Previously, there was code
855        that made a preliminary scan of the pattern in order to do this. That was
856        OK when PCRE was new, but as the facilities have expanded, it has become
857        harder and harder to keep it in step with the real compile phase, and there
858        have been a number of bugs (see for example, 4 above). I have now found a
859        cunning way of running the real compile function in a "fake" mode that
860        enables it to compute how much memory it would need, while actually only
861        ever using a few hundred bytes of working memory and without too many
862        tests of the mode. This should make future maintenance and development
863        easier. A side effect of this work is that the limit of 200 on the nesting
864        depth of parentheses has been removed (though this was never a serious
865        limitation, I suspect). However, there is a downside: pcre_compile() now
866        runs more slowly than before (30% or more, depending on the pattern). I
867        hope this isn't a big issue. There is no effect on runtime performance.
869    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
870        newline (only possible for the last line of a file) and it was a
871        pattern that set a locale (followed by /Lsomething), pcretest crashed.
873    19. Added additional timing features to pcretest. (1) The -tm option now times
874        matching only, not compiling. (2) Both -t and -tm can be followed, as a
875        separate command line item, by a number that specifies the number of
876        repeats to use when timing. The default is 50000; this gives better
877        precision, but takes uncomfortably long for very large patterns.
879    20. Extended pcre_study() to be more clever in cases where a branch of a
880        subpattern has no definite first character. For example, (a*|b*)[cd] would
881        previously give no result from pcre_study(). Now it recognizes that the
882        first character must be a, b, c, or d.
884    21. There was an incorrect error "recursive call could loop indefinitely" if
885        a subpattern (or the entire pattern) that was being tested for matching an
886        empty string contained only one non-empty item after a nested subpattern.
887        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
888        incorrectly, because the \d was being skipped in the check.
890    22. The pcretest program now has a new pattern option /B and a command line
891        option -b, which is equivalent to adding /B to every pattern. This causes
892        it to show the compiled bytecode, without the additional information that
893        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
894        is the same as /B/I).
896    23. A new optimization is now able automatically to treat some sequences such
897        as a*b as a*+b. More specifically, if something simple (such as a character
898        or a simple class like \d) has an unlimited quantifier, and is followed by
899        something that cannot possibly match the quantified thing, the quantifier
900        is automatically "possessified".
902    24. A recursive reference to a subpattern whose number was greater than 39
903        went wrong under certain circumstances in UTF-8 mode. This bug could also
904        have affected the operation of pcre_study().
906    25. Realized that a little bit of performance could be had by replacing
907        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
909    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
911    27. Possessive quantifiers such as a++ were previously implemented by turning
912        them into atomic groups such as ($>a+). Now they have their own opcodes,
913        which improves performance. This includes the automatically created ones
914        from 23 above.
916    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
917        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
918        the first matched character to be a colon. This applied both to named and
919        numbered groups.
921    29. The ucpinternal.h header file was missing its idempotency #ifdef.
923    30. I was sent a "project" file called libpcre.a.dev which I understand makes
924        building PCRE on Windows easier, so I have included it in the distribution.
926    31. There is now a check in pcretest against a ridiculously large number being
927        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
928        loop, the loop is abandoned.
930    32. Forward references to subpatterns in conditions such as (?(2)...) where
931        subpattern 2 is defined later cause pcre_compile() to search forwards in
932        the pattern for the relevant set of parentheses. This search went wrong
933        when there were unescaped parentheses in a character class, parentheses
934        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
936    33. "Subroutine" calls and backreferences were previously restricted to
937        referencing subpatterns earlier in the regex. This restriction has now
938        been removed.
940    34. Added a number of extra features that are going to be in Perl 5.10. On the
941        whole, these are just syntactic alternatives for features that PCRE had
942        previously implemented using the Python syntax or my own invention. The
943        other formats are all retained for compatibility.
945        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
946            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
947            also .NET compatible.
949        (b) A recursion or subroutine call to a named group can now be defined as
950            (?&name) as well as (?P>name).
952        (c) A backreference to a named group can now be defined as \k<name> or
953            \k'name' as well as (?P=name). The new forms, as well as being in Perl
954            5.10, are also .NET compatible.
956        (d) A conditional reference to a named group can now use the syntax
957            (?(<name>) or (?('name') as well as (?(name).
959        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
960            groups (named and numbered) that are never evaluated inline, but can be
961            called as "subroutines" from elsewhere. In effect, the DEFINE condition
962            is always false. There may be only one alternative in such a group.
964        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
965            as the simple (?(R). The condition is true only if the most recent
966            recursion is that of the given number or name. It does not search out
967            through the entire recursion stack.
969        (g) The escape \gN or \g{N} has been added, where N is a positive or
970            negative number, specifying an absolute or relative reference.
972    35. Tidied to get rid of some further signed/unsigned compiler warnings and
973        some "unreachable code" warnings.
975    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
976        things, this adds five new scripts.
978    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
979        There were also incompatibilities regarding the handling of \Q..\E inside
980        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
981        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
983    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
984        matches an empty string, and forcibly breaks the loop. There were bugs in
985        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
986        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
987        separate and independent bugs (that affected different cases) have been
988        fixed.
990    39. Refactored the code to abolish the use of different opcodes for small
991        capturing bracket numbers. This is a tidy that I avoided doing when I
992        removed the limit on the number of capturing brackets for 3.5 back in 2001.
993        The new approach is not only tidier, it makes it possible to reduce the
994        memory needed to fix the previous bug (38).
996    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
997        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
998        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
999        mode.
1001    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
1002        report.
1004    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
1005        copy construction and assignment in the C++ wrapper.
1007    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
1008        couple of bugs that could have given wrong results in the "--newline=crlf"
1009        case.
1011    44. Added a number of casts and did some reorganization of signed/unsigned int
1012        variables following suggestions from Dair Grant. Also renamed the variable
1013        "this" as "item" because it is a C++ keyword.
1015    45. Arranged for dftables to add
1017          #include "pcre_internal.h"
1019        to pcre_chartables.c because without it, gcc 4.x may remove the array
1020        definition from the final binary if PCRE is built into a static library and
1021        dead code stripping is activated.
1023    46. For an unanchored pattern, if a match attempt fails at the start of a
1024        newline sequence, and the newline setting is CRLF or ANY, and the next two
1025        characters are CRLF, advance by two characters instead of one.
1028    Version 6.7 04-Jul-06
1029    ---------------------
1031     1. In order to handle tests when input lines are enormously long, pcretest has
1032        been re-factored so that it automatically extends its buffers when
1033        necessary. The code is crude, but this _is_ just a test program. The
1034        default size has been increased from 32K to 50K.
1036     2. The code in pcre_study() was using the value of the re argument before
1037        testing it for NULL. (Of course, in any sensible call of the function, it
1038        won't be NULL.)
1040     3. The memmove() emulation function in pcre_internal.h, which is used on
1041        systems that lack both memmove() and bcopy() - that is, hardly ever -
1042        was missing a "static" storage class specifier.
1044     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
1045        containing an extended class (one that cannot be represented by a bitmap
1046        because it contains high-valued characters or Unicode property items, e.g.
1047        [\pZ]). Almost always one would set UTF-8 mode when processing such a
1048        pattern, but PCRE should not loop if you do not (it no longer does).
1049        [Detail: two cases were found: (a) a repeated subpattern containing an
1050        extended class; (b) a recursive reference to a subpattern that followed a
1051        previous extended class. It wasn't skipping over the extended class
1052        correctly when UTF-8 mode was not set.]
1054     5. A negated single-character class was not being recognized as fixed-length
1055        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
1056        compile error "lookbehind assertion is not fixed length".
1058     6. The RunPerlTest auxiliary script was showing an unexpected difference
1059        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
1060        write a Perl script that can interpret lines of an input file either as
1061        byte characters or as UTF-8, which is what "perltest" was being required to
1062        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
1063        can't do is switch easily at run time between having the "use utf8;" pragma
1064        or not. In the end, I fudged it by using the RunPerlTest script to insert
1065        "use utf8;" explicitly for the UTF-8 tests.
1067     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
1068        the end of the subject string, contrary to the documentation and to what
1069        Perl does. This was true of both matching functions. Now it matches only at
1070        the start of the subject and immediately after *internal* newlines.
1072     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
1073        a pointer to an int instead of a pointer to an unsigned long int. This
1074        caused problems on 64-bit systems.
1076     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
1077        instance of the 'standard' template library not being so standard".
1079    10. There was no check on the number of named subpatterns nor the maximum
1080        length of a subpattern name. The product of these values is used to compute
1081        the size of the memory block for a compiled pattern. By supplying a very
1082        long subpattern name and a large number of named subpatterns, the size
1083        computation could be caused to overflow. This is now prevented by limiting
1084        the length of names to 32 characters, and the number of named subpatterns
1085        to 10,000.
1087    11. Subpatterns that are repeated with specific counts have to be replicated in
1088        the compiled pattern. The size of memory for this was computed from the
1089        length of the subpattern and the repeat count. The latter is limited to
1090        65535, but there was no limit on the former, meaning that integer overflow
1091        could in principle occur. The compiled length of a repeated subpattern is
1092        now limited to 30,000 bytes in order to prevent this.
1094    12. Added the optional facility to have named substrings with the same name.
1096    13. Added the ability to use a named substring as a condition, using the
1097        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
1098        are numbers (not recommended). Forward references are permitted.
1100    14. Added forward references in named backreferences (if you see what I mean).
1102    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
1103        pattern could run off the end of the subject. For example, the pattern
1104        "(?s)(.{1,5})"8 did this with the subject "ab".
1106    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
1107        PCRE_CASELESS was set when matching characters that were quantified with ?
1108        or *.
1110    17. A character class other than a single negated character that had a minimum
1111        but no maximum quantifier - for example [ab]{6,} - was not handled
1112        correctly by pce_dfa_exec(). It would match only one character.
1114    18. A valid (though odd) pattern that looked like a POSIX character
1115        class but used an invalid character after [ (for example [[,abc,]]) caused
1116        pcre_compile() to give the error "Failed: internal error: code overflow" or
1117        in some cases to crash with a glibc free() error. This could even happen if
1118        the pattern terminated after [[ but there just happened to be a sequence of
1119        letters, a binary zero, and a closing ] in the memory that followed.
1121    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
1122        over the years. Originally (before any Unicode support), just the bottom 8
1123        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
1124        output from "man perlunicode" includes this:
1126          The regular expression compiler produces polymorphic opcodes.  That
1127          is, the pattern adapts to the data and automatically switches to
1128          the Unicode character scheme when presented with Unicode data--or
1129          instead uses a traditional byte scheme when presented with byte
1130          data.
1132        Sadly, a wide octal escape does not cause a switch, and in a string with
1133        no other multibyte characters, these octal escapes are treated as before.
1134        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
1135        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
1136        Unicode string.
1138        I have not perpetrated such confusion in PCRE. Up till now, it took just
1139        the bottom 8 bits, as in old Perl. I have now made octal escapes with
1140        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
1141        translate to the appropriate multibyte character.
1143    29. Applied some refactoring to reduce the number of warnings from Microsoft
1144        and Borland compilers. This has included removing the fudge introduced
1145        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
1146        a warning about an unused variable.
1148    21. PCRE has not included VT (character 0x0b) in the set of whitespace
1149        characters since release 4.0, because Perl (from release 5.004) does not.
1150        [Or at least, is documented not to: some releases seem to be in conflict
1151        with the documentation.] However, when a pattern was studied with
1152        pcre_study() and all its branches started with \s, PCRE still included VT
1153        as a possible starting character. Of course, this did no harm; it just
1154        caused an unnecessary match attempt.
1156    22. Removed a now-redundant internal flag bit that recorded the fact that case
1157        dependency changed within the pattern. This was once needed for "required
1158        byte" processing, but is no longer used. This recovers a now-scarce options
1159        bit. Also moved the least significant internal flag bit to the most-
1160        significant bit of the word, which was not previously used (hangover from
1161        the days when it was an int rather than a uint) to free up another bit for
1162        the future.
1164    23. Added support for CRLF line endings as well as CR and LF. As well as the
1165        default being selectable at build time, it can now be changed at runtime
1166        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
1167        specify that it is scanning data with non-default line endings.
1169    24. Changed the definition of CXXLINK to make it agree with the definition of
1170        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
1172    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
1173        recursions. This makes a big different to stack usage for some patterns.
1175    26. If a subpattern containing a named recursion or subroutine reference such
1176        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
1177        the space required for the compiled pattern went wrong and gave too small a
1178        value. Depending on the environment, this could lead to "Failed: internal
1179        error: code overflow at offset 49" or "glibc detected double free or
1180        corruption" errors.
1182    27. Applied patches from Google (a) to support the new newline modes and (b) to
1183        advance over multibyte UTF-8 characters in GlobalReplace.
1185    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
1186        difference for some implementation of PCRE in some Windows version.
1188    29. Added some extra testing facilities to pcretest:
1190        \q<number>   in a data line sets the "match limit" value
1191        \Q<number>   in a data line sets the "match recursion limt" value
1192        -S <number>  sets the stack size, where <number> is in megabytes
1194        The -S option isn't available for Windows.
1197    Version 6.6 06-Feb-06
1198    ---------------------
1200     1. Change 16(a) for 6.5 broke things, because PCRE_DATA_SCOPE was not defined
1201        in pcreposix.h. I have copied the definition from pcre.h.
1203     2. Change 25 for 6.5 broke compilation in a build directory out-of-tree
1204        because pcre.h is no longer a built file.
1206     3. Added Jeff Friedl's additional debugging patches to pcregrep. These are
1207        not normally included in the compiled code.
1210  Version 6.5 01-Feb-06  Version 6.5 01-Feb-06
1211  ---------------------  ---------------------

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