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revision 49 by nigel, Sat Feb 24 21:39:33 2007 UTC revision 178 by ph10, Wed Jun 13 08:44:34 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
4    Version 7.2 05-June-07
5    ---------------------
7     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
8        which is apparently normally available under Windows.
10     2. Re-jig the pcregrep tests with different newline settings in an attempt
11        to make them independent of the local environment's newline setting.
13     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
15     4. Some of the "internals" tests were previously cut out when the link size
16        was not 2, because the output contained actual offsets. The recent new
17        "Z" feature of pcretest means that these can be cut out, making the tests
18        usable with all link sizes.
20     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
21        stack recursion. This gives a massive performance boost under BSD, but just
22        a small improvement under Linux. However, it saves one field in the frame
23        in all cases.
25     6. Added more features from the forthcoming Perl 5.10:
27        (a) (?-n) (where n is a string of digits) is a relative subroutine or
28            recursion call. It refers to the nth most recently opened parentheses.
30        (b) (?+n) is also a relative subroutine call; it refers to the nth next
31            to be opened parentheses.
33        (c) Conditions that refer to capturing parentheses can be specified
34            relatively, for example, (?(-2)... or (?(+3)...
36        (d) \K resets the start of the current match so that everything before
37            is not part of it.
39        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
41        (f) \g{name} is another synonym - part of Perl 5.10's unification of
42            reference syntax.
44        (g) (?| introduces a group in which the numbering of parentheses in each
45            alternative starts with the same number.
47        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
49     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
52     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
53        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
54        for detecting groups that can match an empty string.
56     9. A pattern with a very large number of alternatives (more than several
57        hundred) was running out of internal workspace during the pre-compile
58        phase, where pcre_compile() figures out how much memory will be needed. A
59        bit of new cunning has reduced the workspace needed for groups with
60        alternatives. The 1000-alternative test pattern now uses 12 bytes of
61        workspace instead of running out of the 4096 that are available.
63    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
66    Version 7.1 24-Apr-07
67    ---------------------
69     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
70        that is more "standard", making use of automake and other Autotools. There
71        is some re-arrangement of the files and adjustment of comments consequent
72        on this.
74     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
75        for recursive directory scanning broke on some systems because the files
76        are not scanned in any specific order and on different systems the order
77        was different. A call to "sort" has been inserted into RunGrepTest for the
78        approprate test as a short-term fix. In the longer term there may be an
79        alternative.
81     3. I had an email from Eric Raymond about problems translating some of PCRE's
82        man pages to HTML (despite the fact that I distribute HTML pages, some
83        people do their own conversions for various reasons). The problems
84        concerned the use of low-level troff macros .br and .in. I have therefore
85        removed all such uses from the man pages (some were redundant, some could
86        be replaced by .nf/.fi pairs). The 132html script that I use to generate
87        HTML has been updated to handle .nf/.fi and to complain if it encounters
88        .br or .in.
90     4. Updated comments in configure.ac that get placed in config.h.in and also
91        arranged for config.h to be included in the distribution, with the name
92        config.h.generic, for the benefit of those who have to compile without
93        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
95     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
96        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
97        makevp.bat for the current PCRE, using the additional files
98        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
100     6. A Windows user reported a minor discrepancy with test 2, which turned out
101        to be caused by a trailing space on an input line that had got lost in his
102        copy. The trailing space was an accident, so I've just removed it.
104     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
105        that is needed.
107     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
108        as "const" (a) because they are and (b) because it helps the PHP
109        maintainers who have recently made a script to detect big data structures
110        in the php code that should be moved to the .rodata section. I remembered
111        to update Builducptable as well, so it won't revert if ucptable.h is ever
112        re-created.
114     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
115        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
116        order to be able to cut out the UTF-8 tables in the latter when UTF-8
117        support is not required. This saves 1.5-2K of code, which is important in
118        some applications.
120        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
121        so as not to refer to the tables, even though these functions will never be
122        called when UTF-8 support is disabled. Otherwise there are problems with a
123        shared library.
125    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
127        (a) It was defining its arguments as char * instead of void *.
129        (b) It was assuming that all moves were upwards in memory; this was true
130            a long time ago when I wrote it, but is no longer the case.
132        The emulated memove() is provided for those environments that have neither
133        memmove() nor bcopy(). I didn't think anyone used it these days, but that
134        is clearly not the case, as these two bugs were recently reported.
136    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
137        and Detrail to create the HTML documentation, the .txt form of the man
138        pages, and it removes trailing spaces from listed files. It also creates
139        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
140        case, it wraps all the #defines with #ifndefs. This script should be run
141        before "make dist".
143    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
144        with Unicode property support.
146        (a) For a maximizing quantifier, if the two different cases of the
147            character were of different lengths in their UTF-8 codings (there are
148            some cases like this - I found 11), and the matching function had to
149            back up over a mixture of the two cases, it incorrectly assumed they
150            were both the same length.
152        (b) When PCRE was configured to use the heap rather than the stack for
153            recursion during matching, it was not correctly preserving the data for
154            the other case of a UTF-8 character when checking ahead for a match
155            while processing a minimizing repeat. If the check also involved
156            matching a wide character, but failed, corruption could cause an
157            erroneous result when trying to check for a repeat of the original
158            character.
160    13. Some tidying changes to the testing mechanism:
162        (a) The RunTest script now detects the internal link size and whether there
163            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
164            values substituted by "configure". (The RunGrepTest script already did
165            this for UTF-8.) The configure.ac script no longer substitutes the
166            relevant variables.
168        (b) The debugging options /B and /D in pcretest show the compiled bytecode
169            with length and offset values. This means that the output is different
170            for different internal link sizes. Test 2 is skipped for link sizes
171            other than 2 because of this, bypassing the problem. Unfortunately,
172            there was also a test in test 3 (the locale tests) that used /B and
173            failed for link sizes other than 2. Rather than cut the whole test out,
174            I have added a new /Z option to pcretest that replaces the length and
175            offset values with spaces. This is now used to make test 3 independent
176            of link size. (Test 2 will be tidied up later.)
178    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
179        segmentation fault instead of returning the appropriate error message.
181    15. In multiline mode when the newline sequence was set to "any", the pattern
182        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
183        This doesn't seem right; it now treats the CRLF combination as the line
184        ending, and so does not match in that case. It's only a pattern such as ^$
185        that would hit this one: something like ^ABC$ would have failed after \r
186        and then tried again after \r\n.
188    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
189        in an attempt to make files that differ only in their line terminators
190        compare equal. This works on Linux.
192    17. Under certain error circumstances pcregrep might try to free random memory
193        as it exited. This is now fixed, thanks to valgrind.
195    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
196        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
197        was because its rules for how to advance for /g after matching an empty
198        string at the end of a line did not allow for this case. They now check for
199        it specially.
201    20. pcretest is supposed to handle patterns and data of any length, by
202        extending its buffers when necessary. It was getting this wrong when the
203        buffer for a data line had to be extended.
205    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
206        CRLF as a newline sequence.
208    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
209        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
210        I have nevertheless tidied it up.
212    23. Added some casts to kill warnings from HP-UX ia64 compiler.
214    24. Added a man page for pcre-config.
217    Version 7.0 19-Dec-06
218    ---------------------
220     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
221        moving to gcc 4.1.1.
223     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
224        sys/time.h, which is documented as needed for this function. It doesn't
225        seem to matter on Linux, but it showed up on some releases of OS X.
227     3. It seems that there are systems where bytes whose values are greater than
228        127 match isprint() in the "C" locale. The "C" locale should be the
229        default when a C program starts up. In most systems, only ASCII printing
230        characters match isprint(). This difference caused the output from pcretest
231        to vary, making some of the tests fail. I have changed pcretest so that:
233        (a) When it is outputting text in the compiled version of a pattern, bytes
234            other than 32-126 are always shown as hex escapes.
236        (b) When it is outputting text that is a matched part of a subject string,
237            it does the same, unless a different locale has been set for the match
238            (using the /L modifier). In this case, it uses isprint() to decide.
240     4. Fixed a major bug that caused incorrect computation of the amount of memory
241        required for a compiled pattern when options that changed within the
242        pattern affected the logic of the preliminary scan that determines the
243        length. The relevant options are -x, and -i in UTF-8 mode. The result was
244        that the computed length was too small. The symptoms of this bug were
245        either the PCRE error "internal error: code overflow" from pcre_compile(),
246        or a glibc crash with a message such as "pcretest: free(): invalid next
247        size (fast)". Examples of patterns that provoked this bug (shown in
248        pcretest format) are:
250          /(?-x: )/x
251          /(?x)(?-x: \s*#\s*)/
252          /((?i)[\x{c0}])/8
253          /(?i:[\x{c0}])/8
255        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
256        is now done differently.
258     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
259        wrapper classes; (b) implement a new function in the C++ scanner that is
260        more efficient than the old way of doing things because it avoids levels of
261        recursion in the regex matching; (c) add a paragraph to the documentation
262        for the FullMatch() function.
264     6. The escape sequence \n was being treated as whatever was defined as
265        "newline". Not only was this contrary to the documentation, which states
266        that \n is character 10 (hex 0A), but it also went horribly wrong when
267        "newline" was defined as CRLF. This has been fixed.
269     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
270        was being set to -1 for the "end of line" case (supposedly a value that no
271        character can have). Though this value is never used (the check for end of
272        line is "zero bytes in current character"), it caused compiler complaints.
273        I've changed it to 0xffffffff.
275     8. In pcre_version.c, the version string was being built by a sequence of
276        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
277        string (as it is for production releases) called a macro with an empty
278        argument. The C standard says the result of this is undefined. The gcc
279        compiler treats it as an empty string (which was what was wanted) but it is
280        reported that Visual C gives an error. The source has been hacked around to
281        avoid this problem.
283     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
284        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
285        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
286        of them did).
288    10. Originally, pcretest opened its input and output without "b"; then I was
289        told that "b" was needed in some environments, so it was added for release
290        5.0 to both the input and output. (It makes no difference on Unix-like
291        systems.) Later I was told that it is wrong for the input on Windows. I've
292        now abstracted the modes into two macros, to make it easier to fiddle with
293        them, and removed "b" from the input mode under Windows.
295    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
297    12. Added -help and --help to pcretest as an official way of being reminded
298        of the options.
300    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
301        and pcrecpp.cc because they annoy compilers at high warning levels.
303    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
305    15. Fixed an occurrence of == in configure.ac that should have been = (shell
306        scripts are not C programs :-) and which was not noticed because it works
307        on Linux.
309    16. pcretest is supposed to handle any length of pattern and data line (as one
310        line or as a continued sequence of lines) by extending its input buffer if
311        necessary. This feature was broken for very long pattern lines, leading to
312        a string of junk being passed to pcre_compile() if the pattern was longer
313        than about 50K.
315    17. I have done a major re-factoring of the way pcre_compile() computes the
316        amount of memory needed for a compiled pattern. Previously, there was code
317        that made a preliminary scan of the pattern in order to do this. That was
318        OK when PCRE was new, but as the facilities have expanded, it has become
319        harder and harder to keep it in step with the real compile phase, and there
320        have been a number of bugs (see for example, 4 above). I have now found a
321        cunning way of running the real compile function in a "fake" mode that
322        enables it to compute how much memory it would need, while actually only
323        ever using a few hundred bytes of working memory and without too many
324        tests of the mode. This should make future maintenance and development
325        easier. A side effect of this work is that the limit of 200 on the nesting
326        depth of parentheses has been removed (though this was never a serious
327        limitation, I suspect). However, there is a downside: pcre_compile() now
328        runs more slowly than before (30% or more, depending on the pattern). I
329        hope this isn't a big issue. There is no effect on runtime performance.
331    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
332        newline (only possible for the last line of a file) and it was a
333        pattern that set a locale (followed by /Lsomething), pcretest crashed.
335    19. Added additional timing features to pcretest. (1) The -tm option now times
336        matching only, not compiling. (2) Both -t and -tm can be followed, as a
337        separate command line item, by a number that specifies the number of
338        repeats to use when timing. The default is 50000; this gives better
339        precision, but takes uncomfortably long for very large patterns.
341    20. Extended pcre_study() to be more clever in cases where a branch of a
342        subpattern has no definite first character. For example, (a*|b*)[cd] would
343        previously give no result from pcre_study(). Now it recognizes that the
344        first character must be a, b, c, or d.
346    21. There was an incorrect error "recursive call could loop indefinitely" if
347        a subpattern (or the entire pattern) that was being tested for matching an
348        empty string contained only one non-empty item after a nested subpattern.
349        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
350        incorrectly, because the \d was being skipped in the check.
352    22. The pcretest program now has a new pattern option /B and a command line
353        option -b, which is equivalent to adding /B to every pattern. This causes
354        it to show the compiled bytecode, without the additional information that
355        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
356        is the same as /B/I).
358    23. A new optimization is now able automatically to treat some sequences such
359        as a*b as a*+b. More specifically, if something simple (such as a character
360        or a simple class like \d) has an unlimited quantifier, and is followed by
361        something that cannot possibly match the quantified thing, the quantifier
362        is automatically "possessified".
364    24. A recursive reference to a subpattern whose number was greater than 39
365        went wrong under certain circumstances in UTF-8 mode. This bug could also
366        have affected the operation of pcre_study().
368    25. Realized that a little bit of performance could be had by replacing
369        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
371    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
373    27. Possessive quantifiers such as a++ were previously implemented by turning
374        them into atomic groups such as ($>a+). Now they have their own opcodes,
375        which improves performance. This includes the automatically created ones
376        from 23 above.
378    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
379        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
380        the first matched character to be a colon. This applied both to named and
381        numbered groups.
383    29. The ucpinternal.h header file was missing its idempotency #ifdef.
385    30. I was sent a "project" file called libpcre.a.dev which I understand makes
386        building PCRE on Windows easier, so I have included it in the distribution.
388    31. There is now a check in pcretest against a ridiculously large number being
389        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
390        loop, the loop is abandoned.
392    32. Forward references to subpatterns in conditions such as (?(2)...) where
393        subpattern 2 is defined later cause pcre_compile() to search forwards in
394        the pattern for the relevant set of parentheses. This search went wrong
395        when there were unescaped parentheses in a character class, parentheses
396        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
398    33. "Subroutine" calls and backreferences were previously restricted to
399        referencing subpatterns earlier in the regex. This restriction has now
400        been removed.
402    34. Added a number of extra features that are going to be in Perl 5.10. On the
403        whole, these are just syntactic alternatives for features that PCRE had
404        previously implemented using the Python syntax or my own invention. The
405        other formats are all retained for compatibility.
407        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
408            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
409            also .NET compatible.
411        (b) A recursion or subroutine call to a named group can now be defined as
412            (?&name) as well as (?P>name).
414        (c) A backreference to a named group can now be defined as \k<name> or
415            \k'name' as well as (?P=name). The new forms, as well as being in Perl
416            5.10, are also .NET compatible.
418        (d) A conditional reference to a named group can now use the syntax
419            (?(<name>) or (?('name') as well as (?(name).
421        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
422            groups (named and numbered) that are never evaluated inline, but can be
423            called as "subroutines" from elsewhere. In effect, the DEFINE condition
424            is always false. There may be only one alternative in such a group.
426        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
427            as the simple (?(R). The condition is true only if the most recent
428            recursion is that of the given number or name. It does not search out
429            through the entire recursion stack.
431        (g) The escape \gN or \g{N} has been added, where N is a positive or
432            negative number, specifying an absolute or relative reference.
434    35. Tidied to get rid of some further signed/unsigned compiler warnings and
435        some "unreachable code" warnings.
437    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
438        things, this adds five new scripts.
440    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
441        There were also incompatibilities regarding the handling of \Q..\E inside
442        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
443        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
445    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
446        matches an empty string, and forcibly breaks the loop. There were bugs in
447        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
448        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
449        separate and independent bugs (that affected different cases) have been
450        fixed.
452    39. Refactored the code to abolish the use of different opcodes for small
453        capturing bracket numbers. This is a tidy that I avoided doing when I
454        removed the limit on the number of capturing brackets for 3.5 back in 2001.
455        The new approach is not only tidier, it makes it possible to reduce the
456        memory needed to fix the previous bug (38).
458    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
459        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
460        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
461        mode.
463    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
464        report.
466    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
467        copy construction and assignment in the C++ wrapper.
469    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
470        couple of bugs that could have given wrong results in the "--newline=crlf"
471        case.
473    44. Added a number of casts and did some reorganization of signed/unsigned int
474        variables following suggestions from Dair Grant. Also renamed the variable
475        "this" as "item" because it is a C++ keyword.
477    45. Arranged for dftables to add
479          #include "pcre_internal.h"
481        to pcre_chartables.c because without it, gcc 4.x may remove the array
482        definition from the final binary if PCRE is built into a static library and
483        dead code stripping is activated.
485    46. For an unanchored pattern, if a match attempt fails at the start of a
486        newline sequence, and the newline setting is CRLF or ANY, and the next two
487        characters are CRLF, advance by two characters instead of one.
490    Version 6.7 04-Jul-06
491    ---------------------
493     1. In order to handle tests when input lines are enormously long, pcretest has
494        been re-factored so that it automatically extends its buffers when
495        necessary. The code is crude, but this _is_ just a test program. The
496        default size has been increased from 32K to 50K.
498     2. The code in pcre_study() was using the value of the re argument before
499        testing it for NULL. (Of course, in any sensible call of the function, it
500        won't be NULL.)
502     3. The memmove() emulation function in pcre_internal.h, which is used on
503        systems that lack both memmove() and bcopy() - that is, hardly ever -
504        was missing a "static" storage class specifier.
506     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
507        containing an extended class (one that cannot be represented by a bitmap
508        because it contains high-valued characters or Unicode property items, e.g.
509        [\pZ]). Almost always one would set UTF-8 mode when processing such a
510        pattern, but PCRE should not loop if you do not (it no longer does).
511        [Detail: two cases were found: (a) a repeated subpattern containing an
512        extended class; (b) a recursive reference to a subpattern that followed a
513        previous extended class. It wasn't skipping over the extended class
514        correctly when UTF-8 mode was not set.]
516     5. A negated single-character class was not being recognized as fixed-length
517        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
518        compile error "lookbehind assertion is not fixed length".
520     6. The RunPerlTest auxiliary script was showing an unexpected difference
521        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
522        write a Perl script that can interpret lines of an input file either as
523        byte characters or as UTF-8, which is what "perltest" was being required to
524        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
525        can't do is switch easily at run time between having the "use utf8;" pragma
526        or not. In the end, I fudged it by using the RunPerlTest script to insert
527        "use utf8;" explicitly for the UTF-8 tests.
529     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
530        the end of the subject string, contrary to the documentation and to what
531        Perl does. This was true of both matching functions. Now it matches only at
532        the start of the subject and immediately after *internal* newlines.
534     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
535        a pointer to an int instead of a pointer to an unsigned long int. This
536        caused problems on 64-bit systems.
538     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
539        instance of the 'standard' template library not being so standard".
541    10. There was no check on the number of named subpatterns nor the maximum
542        length of a subpattern name. The product of these values is used to compute
543        the size of the memory block for a compiled pattern. By supplying a very
544        long subpattern name and a large number of named subpatterns, the size
545        computation could be caused to overflow. This is now prevented by limiting
546        the length of names to 32 characters, and the number of named subpatterns
547        to 10,000.
549    11. Subpatterns that are repeated with specific counts have to be replicated in
550        the compiled pattern. The size of memory for this was computed from the
551        length of the subpattern and the repeat count. The latter is limited to
552        65535, but there was no limit on the former, meaning that integer overflow
553        could in principle occur. The compiled length of a repeated subpattern is
554        now limited to 30,000 bytes in order to prevent this.
556    12. Added the optional facility to have named substrings with the same name.
558    13. Added the ability to use a named substring as a condition, using the
559        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
560        are numbers (not recommended). Forward references are permitted.
562    14. Added forward references in named backreferences (if you see what I mean).
564    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
565        pattern could run off the end of the subject. For example, the pattern
566        "(?s)(.{1,5})"8 did this with the subject "ab".
568    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
569        PCRE_CASELESS was set when matching characters that were quantified with ?
570        or *.
572    17. A character class other than a single negated character that had a minimum
573        but no maximum quantifier - for example [ab]{6,} - was not handled
574        correctly by pce_dfa_exec(). It would match only one character.
576    18. A valid (though odd) pattern that looked like a POSIX character
577        class but used an invalid character after [ (for example [[,abc,]]) caused
578        pcre_compile() to give the error "Failed: internal error: code overflow" or
579        in some cases to crash with a glibc free() error. This could even happen if
580        the pattern terminated after [[ but there just happened to be a sequence of
581        letters, a binary zero, and a closing ] in the memory that followed.
583    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
584        over the years. Originally (before any Unicode support), just the bottom 8
585        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
586        output from "man perlunicode" includes this:
588          The regular expression compiler produces polymorphic opcodes.  That
589          is, the pattern adapts to the data and automatically switches to
590          the Unicode character scheme when presented with Unicode data--or
591          instead uses a traditional byte scheme when presented with byte
592          data.
594        Sadly, a wide octal escape does not cause a switch, and in a string with
595        no other multibyte characters, these octal escapes are treated as before.
596        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
597        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
598        Unicode string.
600        I have not perpetrated such confusion in PCRE. Up till now, it took just
601        the bottom 8 bits, as in old Perl. I have now made octal escapes with
602        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
603        translate to the appropriate multibyte character.
605    29. Applied some refactoring to reduce the number of warnings from Microsoft
606        and Borland compilers. This has included removing the fudge introduced
607        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
608        a warning about an unused variable.
610    21. PCRE has not included VT (character 0x0b) in the set of whitespace
611        characters since release 4.0, because Perl (from release 5.004) does not.
612        [Or at least, is documented not to: some releases seem to be in conflict
613        with the documentation.] However, when a pattern was studied with
614        pcre_study() and all its branches started with \s, PCRE still included VT
615        as a possible starting character. Of course, this did no harm; it just
616        caused an unnecessary match attempt.
618    22. Removed a now-redundant internal flag bit that recorded the fact that case
619        dependency changed within the pattern. This was once needed for "required
620        byte" processing, but is no longer used. This recovers a now-scarce options
621        bit. Also moved the least significant internal flag bit to the most-
622        significant bit of the word, which was not previously used (hangover from
623        the days when it was an int rather than a uint) to free up another bit for
624        the future.
626    23. Added support for CRLF line endings as well as CR and LF. As well as the
627        default being selectable at build time, it can now be changed at runtime
628        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
629        specify that it is scanning data with non-default line endings.
631    24. Changed the definition of CXXLINK to make it agree with the definition of
632        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
634    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
635        recursions. This makes a big different to stack usage for some patterns.
637    26. If a subpattern containing a named recursion or subroutine reference such
638        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
639        the space required for the compiled pattern went wrong and gave too small a
640        value. Depending on the environment, this could lead to "Failed: internal
641        error: code overflow at offset 49" or "glibc detected double free or
642        corruption" errors.
644    27. Applied patches from Google (a) to support the new newline modes and (b) to
645        advance over multibyte UTF-8 characters in GlobalReplace.
647    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
648        difference for some implementation of PCRE in some Windows version.
650    29. Added some extra testing facilities to pcretest:
652        \q<number>   in a data line sets the "match limit" value
653        \Q<number>   in a data line sets the "match recursion limt" value
654        -S <number>  sets the stack size, where <number> is in megabytes
656        The -S option isn't available for Windows.
659    Version 6.6 06-Feb-06
660    ---------------------
662     1. Change 16(a) for 6.5 broke things, because PCRE_DATA_SCOPE was not defined
663        in pcreposix.h. I have copied the definition from pcre.h.
665     2. Change 25 for 6.5 broke compilation in a build directory out-of-tree
666        because pcre.h is no longer a built file.
668     3. Added Jeff Friedl's additional debugging patches to pcregrep. These are
669        not normally included in the compiled code.
672    Version 6.5 01-Feb-06
673    ---------------------
675     1. When using the partial match feature with pcre_dfa_exec(), it was not
676        anchoring the second and subsequent partial matches at the new starting
677        point. This could lead to incorrect results. For example, with the pattern
678        /1234/, partially matching against "123" and then "a4" gave a match.
680     2. Changes to pcregrep:
682        (a) All non-match returns from pcre_exec() were being treated as failures
683            to match the line. Now, unless the error is PCRE_ERROR_NOMATCH, an
684            error message is output. Some extra information is given for the
685            PCRE_ERROR_MATCHLIMIT and PCRE_ERROR_RECURSIONLIMIT errors, which are
686            probably the only errors that are likely to be caused by users (by
687            specifying a regex that has nested indefinite repeats, for instance).
688            If there are more than 20 of these errors, pcregrep is abandoned.
690        (b) A binary zero was treated as data while matching, but terminated the
691            output line if it was written out. This has been fixed: binary zeroes
692            are now no different to any other data bytes.
694        (c) Whichever of the LC_ALL or LC_CTYPE environment variables is set is
695            used to set a locale for matching. The --locale=xxxx long option has
696            been added (no short equivalent) to specify a locale explicitly on the
697            pcregrep command, overriding the environment variables.
699        (d) When -B was used with -n, some line numbers in the output were one less
700            than they should have been.
702        (e) Added the -o (--only-matching) option.
704        (f) If -A or -C was used with -c (count only), some lines of context were
705            accidentally printed for the final match.
707        (g) Added the -H (--with-filename) option.
709        (h) The combination of options -rh failed to suppress file names for files
710            that were found from directory arguments.
712        (i) Added the -D (--devices) and -d (--directories) options.
714        (j) Added the -F (--fixed-strings) option.
716        (k) Allow "-" to be used as a file name for -f as well as for a data file.
718        (l) Added the --colo(u)r option.
720        (m) Added Jeffrey Friedl's -S testing option, but within #ifdefs so that it
721            is not present by default.
723     3. A nasty bug was discovered in the handling of recursive patterns, that is,
724        items such as (?R) or (?1), when the recursion could match a number of
725        alternatives. If it matched one of the alternatives, but subsequently,
726        outside the recursion, there was a failure, the code tried to back up into
727        the recursion. However, because of the way PCRE is implemented, this is not
728        possible, and the result was an incorrect result from the match.
730        In order to prevent this happening, the specification of recursion has
731        been changed so that all such subpatterns are automatically treated as
732        atomic groups. Thus, for example, (?R) is treated as if it were (?>(?R)).
734     4. I had overlooked the fact that, in some locales, there are characters for
735        which isalpha() is true but neither isupper() nor islower() are true. In
736        the fr_FR locale, for instance, the \xAA and \xBA characters (ordmasculine
737        and ordfeminine) are like this. This affected the treatment of \w and \W
738        when they appeared in character classes, but not when they appeared outside
739        a character class. The bit map for "word" characters is now created
740        separately from the results of isalnum() instead of just taking it from the
741        upper, lower, and digit maps. (Plus the underscore character, of course.)
743     5. The above bug also affected the handling of POSIX character classes such as
744        [[:alpha:]] and [[:alnum:]]. These do not have their own bit maps in PCRE's
745        permanent tables. Instead, the bit maps for such a class were previously
746        created as the appropriate unions of the upper, lower, and digit bitmaps.
747        Now they are created by subtraction from the [[:word:]] class, which has
748        its own bitmap.
750     6. The [[:blank:]] character class matches horizontal, but not vertical space.
751        It is created by subtracting the vertical space characters (\x09, \x0a,
752        \x0b, \x0c) from the [[:space:]] bitmap. Previously, however, the
753        subtraction was done in the overall bitmap for a character class, meaning
754        that a class such as [\x0c[:blank:]] was incorrect because \x0c would not
755        be recognized. This bug has been fixed.
757     7. Patches from the folks at Google:
759          (a) pcrecpp.cc: "to handle a corner case that may or may not happen in
760          real life, but is still worth protecting against".
762          (b) pcrecpp.cc: "corrects a bug when negative radixes are used with
763          regular expressions".
765          (c) pcre_scanner.cc: avoid use of std::count() because not all systems
766          have it.
768          (d) Split off pcrecpparg.h from pcrecpp.h and had the former built by
769          "configure" and the latter not, in order to fix a problem somebody had
770          with compiling the Arg class on HP-UX.
772          (e) Improve the error-handling of the C++ wrapper a little bit.
774          (f) New tests for checking recursion limiting.
776     8. The pcre_memmove() function, which is used only if the environment does not
777        have a standard memmove() function (and is therefore rarely compiled),
778        contained two bugs: (a) use of int instead of size_t, and (b) it was not
779        returning a result (though PCRE never actually uses the result).
781     9. In the POSIX regexec() interface, if nmatch is specified as a ridiculously
782        large number - greater than INT_MAX/(3*sizeof(int)) - REG_ESPACE is
783        returned instead of calling malloc() with an overflowing number that would
784        most likely cause subsequent chaos.
786    10. The debugging option of pcretest was not showing the NO_AUTO_CAPTURE flag.
788    11. The POSIX flag REG_NOSUB is now supported. When a pattern that was compiled
789        with this option is matched, the nmatch and pmatch options of regexec() are
790        ignored.
792    12. Added REG_UTF8 to the POSIX interface. This is not defined by POSIX, but is
793        provided in case anyone wants to the the POSIX interface with UTF-8
794        strings.
796    13. Added CXXLDFLAGS to the Makefile parameters to provide settings only on the
797        C++ linking (needed for some HP-UX environments).
799    14. Avoid compiler warnings in get_ucpname() when compiled without UCP support
800        (unused parameter) and in the pcre_printint() function (omitted "default"
801        switch label when the default is to do nothing).
803    15. Added some code to make it possible, when PCRE is compiled as a C++
804        library, to replace subject pointers for pcre_exec() with a smart pointer
805        class, thus making it possible to process discontinuous strings.
807    16. The two macros PCRE_EXPORT and PCRE_DATA_SCOPE are confusing, and perform
808        much the same function. They were added by different people who were trying
809        to make PCRE easy to compile on non-Unix systems. It has been suggested
810        that PCRE_EXPORT be abolished now that there is more automatic apparatus
811        for compiling on Windows systems. I have therefore replaced it with
812        PCRE_DATA_SCOPE. This is set automatically for Windows; if not set it
813        defaults to "extern" for C or "extern C" for C++, which works fine on
814        Unix-like systems. It is now possible to override the value of PCRE_DATA_
815        SCOPE with something explicit in config.h. In addition:
817        (a) pcreposix.h still had just "extern" instead of either of these macros;
818            I have replaced it with PCRE_DATA_SCOPE.
820        (b) Functions such as _pcre_xclass(), which are internal to the library,
821            but external in the C sense, all had PCRE_EXPORT in their definitions.
822            This is apparently wrong for the Windows case, so I have removed it.
823            (It makes no difference on Unix-like systems.)
825    17. Added a new limit, MATCH_LIMIT_RECURSION, which limits the depth of nesting
826        of recursive calls to match(). This is different to MATCH_LIMIT because
827        that limits the total number of calls to match(), not all of which increase
828        the depth of recursion. Limiting the recursion depth limits the amount of
829        stack (or heap if NO_RECURSE is set) that is used. The default can be set
830        when PCRE is compiled, and changed at run time. A patch from Google adds
831        this functionality to the C++ interface.
833    18. Changes to the handling of Unicode character properties:
835        (a) Updated the table to Unicode 4.1.0.
837        (b) Recognize characters that are not in the table as "Cn" (undefined).
839        (c) I revised the way the table is implemented to a much improved format
840            which includes recognition of ranges. It now supports the ranges that
841            are defined in UnicodeData.txt, and it also amalgamates other
842            characters into ranges. This has reduced the number of entries in the
843            table from around 16,000 to around 3,000, thus reducing its size
844            considerably. I realized I did not need to use a tree structure after
845            all - a binary chop search is just as efficient. Having reduced the
846            number of entries, I extended their size from 6 bytes to 8 bytes to
847            allow for more data.
849        (d) Added support for Unicode script names via properties such as \p{Han}.
851    19. In UTF-8 mode, a backslash followed by a non-Ascii character was not
852        matching that character.
854    20. When matching a repeated Unicode property with a minimum greater than zero,
855        (for example \pL{2,}), PCRE could look past the end of the subject if it
856        reached it while seeking the minimum number of characters. This could
857        happen only if some of the characters were more than one byte long, because
858        there is a check for at least the minimum number of bytes.
860    21. Refactored the implementation of \p and \P so as to be more general, to
861        allow for more different types of property in future. This has changed the
862        compiled form incompatibly. Anybody with saved compiled patterns that use
863        \p or \P will have to recompile them.
865    22. Added "Any" and "L&" to the supported property types.
867    23. Recognize \x{...} as a code point specifier, even when not in UTF-8 mode,
868        but give a compile time error if the value is greater than 0xff.
870    24. The man pages for pcrepartial, pcreprecompile, and pcre_compile2 were
871        accidentally not being installed or uninstalled.
873    25. The pcre.h file was built from pcre.h.in, but the only changes that were
874        made were to insert the current release number. This seemed silly, because
875        it made things harder for people building PCRE on systems that don't run
876        "configure". I have turned pcre.h into a distributed file, no longer built
877        by "configure", with the version identification directly included. There is
878        no longer a pcre.h.in file.
880        However, this change necessitated a change to the pcre-config script as
881        well. It is built from pcre-config.in, and one of the substitutions was the
882        release number. I have updated configure.ac so that ./configure now finds
883        the release number by grepping pcre.h.
885    26. Added the ability to run the tests under valgrind.
888    Version 6.4 05-Sep-05
889    ---------------------
891     1. Change 6.0/10/(l) to pcregrep introduced a bug that caused separator lines
892        "--" to be printed when multiple files were scanned, even when none of the
893        -A, -B, or -C options were used. This is not compatible with Gnu grep, so I
894        consider it to be a bug, and have restored the previous behaviour.
896     2. A couple of code tidies to get rid of compiler warnings.
898     3. The pcretest program used to cheat by referring to symbols in the library
899        whose names begin with _pcre_. These are internal symbols that are not
900        really supposed to be visible externally, and in some environments it is
901        possible to suppress them. The cheating is now confined to including
902        certain files from the library's source, which is a bit cleaner.
904     4. Renamed pcre.in as pcre.h.in to go with pcrecpp.h.in; it also makes the
905        file's purpose clearer.
907     5. Reorganized pcre_ucp_findchar().
910    Version 6.3 15-Aug-05
911    ---------------------
913     1. The file libpcre.pc.in did not have general read permission in the tarball.
915     2. There were some problems when building without C++ support:
917        (a) If C++ support was not built, "make install" and "make test" still
918            tried to test it.
920        (b) There were problems when the value of CXX was explicitly set. Some
921            changes have been made to try to fix these, and ...
923        (c) --disable-cpp can now be used to explicitly disable C++ support.
925        (d) The use of @CPP_OBJ@ directly caused a blank line preceded by a
926            backslash in a target when C++ was disabled. This confuses some
927            versions of "make", apparently. Using an intermediate variable solves
928            this. (Same for CPP_LOBJ.)
930     3. $(LINK_FOR_BUILD) now includes $(CFLAGS_FOR_BUILD) and $(LINK)
931        (non-Windows) now includes $(CFLAGS) because these flags are sometimes
932        necessary on certain architectures.
934     4. Added a setting of -export-symbols-regex to the link command to remove
935        those symbols that are exported in the C sense, but actually are local
936        within the library, and not documented. Their names all begin with
937        "_pcre_". This is not a perfect job, because (a) we have to except some
938        symbols that pcretest ("illegally") uses, and (b) the facility isn't always
939        available (and never for static libraries). I have made a note to try to
940        find a way round (a) in the future.
943    Version 6.2 01-Aug-05
944    ---------------------
946     1. There was no test for integer overflow of quantifier values. A construction
947        such as {1111111111111111} would give undefined results. What is worse, if
948        a minimum quantifier for a parenthesized subpattern overflowed and became
949        negative, the calculation of the memory size went wrong. This could have
950        led to memory overwriting.
952     2. Building PCRE using VPATH was broken. Hopefully it is now fixed.
954     3. Added "b" to the 2nd argument of fopen() in dftables.c, for non-Unix-like
955        operating environments where this matters.
957     4. Applied Giuseppe Maxia's patch to add additional features for controlling
958        PCRE options from within the C++ wrapper.
960     5. Named capturing subpatterns were not being correctly counted when a pattern
961        was compiled. This caused two problems: (a) If there were more than 100
962        such subpatterns, the calculation of the memory needed for the whole
963        compiled pattern went wrong, leading to an overflow error. (b) Numerical
964        back references of the form \12, where the number was greater than 9, were
965        not recognized as back references, even though there were sufficient
966        previous subpatterns.
968     6. Two minor patches to pcrecpp.cc in order to allow it to compile on older
969        versions of gcc, e.g. 2.95.4.
972    Version 6.1 21-Jun-05
973    ---------------------
975     1. There was one reference to the variable "posix" in pcretest.c that was not
976        surrounded by "#if !defined NOPOSIX".
978     2. Make it possible to compile pcretest without DFA support, UTF8 support, or
979        the cross-check on the old pcre_info() function, for the benefit of the
980        cut-down version of PCRE that is currently imported into Exim.
982     3. A (silly) pattern starting with (?i)(?-i) caused an internal space
983        allocation error. I've done the easy fix, which wastes 2 bytes for sensible
984        patterns that start (?i) but I don't think that matters. The use of (?i) is
985        just an example; this all applies to the other options as well.
987     4. Since libtool seems to echo the compile commands it is issuing, the output
988        from "make" can be reduced a bit by putting "@" in front of each libtool
989        compile command.
991     5. Patch from the folks at Google for configure.in to be a bit more thorough
992        in checking for a suitable C++ installation before trying to compile the
993        C++ stuff. This should fix a reported problem when a compiler was present,
994        but no suitable headers.
996     6. The man pages all had just "PCRE" as their title. I have changed them to
997        be the relevant file name. I have also arranged that these names are
998        retained in the file doc/pcre.txt, which is a concatenation in text format
999        of all the man pages except the little individual ones for each function.
1001     7. The NON-UNIX-USE file had not been updated for the different set of source
1002        files that come with release 6. I also added a few comments about the C++
1003        wrapper.
1006    Version 6.0 07-Jun-05
1007    ---------------------
1009     1. Some minor internal re-organization to help with my DFA experiments.
1011     2. Some missing #ifdef SUPPORT_UCP conditionals in pcretest and printint that
1012        didn't matter for the library itself when fully configured, but did matter
1013        when compiling without UCP support, or within Exim, where the ucp files are
1014        not imported.
1016     3. Refactoring of the library code to split up the various functions into
1017        different source modules. The addition of the new DFA matching code (see
1018        below) to a single monolithic source would have made it really too
1019        unwieldy, quite apart from causing all the code to be include in a
1020        statically linked application, when only some functions are used. This is
1021        relevant even without the DFA addition now that patterns can be compiled in
1022        one application and matched in another.
1024        The downside of splitting up is that there have to be some external
1025        functions and data tables that are used internally in different modules of
1026        the library but which are not part of the API. These have all had their
1027        names changed to start with "_pcre_" so that they are unlikely to clash
1028        with other external names.
1030     4. Added an alternate matching function, pcre_dfa_exec(), which matches using
1031        a different (DFA) algorithm. Although it is slower than the original
1032        function, it does have some advantages for certain types of matching
1033        problem.
1035     5. Upgrades to pcretest in order to test the features of pcre_dfa_exec(),
1036        including restarting after a partial match.
1038     6. A patch for pcregrep that defines INVALID_FILE_ATTRIBUTES if it is not
1039        defined when compiling for Windows was sent to me. I have put it into the
1040        code, though I have no means of testing or verifying it.
1042     7. Added the pcre_refcount() auxiliary function.
1044     8. Added the PCRE_FIRSTLINE option. This constrains an unanchored pattern to
1045        match before or at the first newline in the subject string. In pcretest,
1046        the /f option on a pattern can be used to set this.
1048     9. A repeated \w when used in UTF-8 mode with characters greater than 256
1049        would behave wrongly. This has been present in PCRE since release 4.0.
1051    10. A number of changes to the pcregrep command:
1053        (a) Refactored how -x works; insert ^(...)$ instead of setting
1054            PCRE_ANCHORED and checking the length, in preparation for adding
1055            something similar for -w.
1057        (b) Added the -w (match as a word) option.
1059        (c) Refactored the way lines are read and buffered so as to have more
1060            than one at a time available.
1062        (d) Implemented a pcregrep test script.
1064        (e) Added the -M (multiline match) option. This allows patterns to match
1065            over several lines of the subject. The buffering ensures that at least
1066            8K, or the rest of the document (whichever is the shorter) is available
1067            for matching (and similarly the previous 8K for lookbehind assertions).
1069        (f) Changed the --help output so that it now says
1071              -w, --word-regex(p)
1073            instead of two lines, one with "regex" and the other with "regexp"
1074            because that confused at least one person since the short forms are the
1075            same. (This required a bit of code, as the output is generated
1076            automatically from a table. It wasn't just a text change.)
1078        (g) -- can be used to terminate pcregrep options if the next thing isn't an
1079            option but starts with a hyphen. Could be a pattern or a path name
1080            starting with a hyphen, for instance.
1082        (h) "-" can be given as a file name to represent stdin.
1084        (i) When file names are being printed, "(standard input)" is used for
1085            the standard input, for compatibility with GNU grep. Previously
1086            "<stdin>" was used.
1088        (j) The option --label=xxx can be used to supply a name to be used for
1089            stdin when file names are being printed. There is no short form.
1091        (k) Re-factored the options decoding logic because we are going to add
1092            two more options that take data. Such options can now be given in four
1093            different ways, e.g. "-fname", "-f name", "--file=name", "--file name".
1095        (l) Added the -A, -B, and -C options for requesting that lines of context
1096            around matches be printed.
1098        (m) Added the -L option to print the names of files that do not contain
1099            any matching lines, that is, the complement of -l.
1101        (n) The return code is 2 if any file cannot be opened, but pcregrep does
1102            continue to scan other files.
1104        (o) The -s option was incorrectly implemented. For compatibility with other
1105            greps, it now suppresses the error message for a non-existent or non-
1106            accessible file (but not the return code). There is a new option called
1107            -q that suppresses the output of matching lines, which was what -s was
1108            previously doing.
1110        (p) Added --include and --exclude options to specify files for inclusion
1111            and exclusion when recursing.
1113    11. The Makefile was not using the Autoconf-supported LDFLAGS macro properly.
1114        Hopefully, it now does.
1116    12. Missing cast in pcre_study().
1118    13. Added an "uninstall" target to the makefile.
1120    14. Replaced "extern" in the function prototypes in Makefile.in with
1121        "PCRE_DATA_SCOPE", which defaults to 'extern' or 'extern "C"' in the Unix
1122        world, but is set differently for Windows.
1124    15. Added a second compiling function called pcre_compile2(). The only
1125        difference is that it has an extra argument, which is a pointer to an
1126        integer error code. When there is a compile-time failure, this is set
1127        non-zero, in addition to the error test pointer being set to point to an
1128        error message. The new argument may be NULL if no error number is required
1129        (but then you may as well call pcre_compile(), which is now just a
1130        wrapper). This facility is provided because some applications need a
1131        numeric error indication, but it has also enabled me to tidy up the way
1132        compile-time errors are handled in the POSIX wrapper.
1134    16. Added VPATH=.libs to the makefile; this should help when building with one
1135        prefix path and installing with another. (Or so I'm told by someone who
1136        knows more about this stuff than I do.)
1138    17. Added a new option, REG_DOTALL, to the POSIX function regcomp(). This
1139        passes PCRE_DOTALL to the pcre_compile() function, making the "." character
1140        match everything, including newlines. This is not POSIX-compatible, but
1141        somebody wanted the feature. From pcretest it can be activated by using
1142        both the P and the s flags.
1144    18. AC_PROG_LIBTOOL appeared twice in Makefile.in. Removed one.
1146    19. libpcre.pc was being incorrectly installed as executable.
1148    20. A couple of places in pcretest check for end-of-line by looking for '\n';
1149        it now also looks for '\r' so that it will work unmodified on Windows.
1151    21. Added Google's contributed C++ wrapper to the distribution.
1153    22. Added some untidy missing memory free() calls in pcretest, to keep
1154        Electric Fence happy when testing.
1158    Version 5.0 13-Sep-04
1159    ---------------------
1161     1. Internal change: literal characters are no longer packed up into items
1162        containing multiple characters in a single byte-string. Each character
1163        is now matched using a separate opcode. However, there may be more than one
1164        byte in the character in UTF-8 mode.
1166     2. The pcre_callout_block structure has two new fields: pattern_position and
1167        next_item_length. These contain the offset in the pattern to the next match
1168        item, and its length, respectively.
1170     3. The PCRE_AUTO_CALLOUT option for pcre_compile() requests the automatic
1171        insertion of callouts before each pattern item. Added the /C option to
1172        pcretest to make use of this.
1174     4. On the advice of a Windows user, the lines
1176          #if defined(_WIN32) || defined(WIN32)
1177          _setmode( _fileno( stdout ), 0x8000 );
1178          #endif  /* defined(_WIN32) || defined(WIN32) */
1180        have been added to the source of pcretest. This apparently does useful
1181        magic in relation to line terminators.
1183     5. Changed "r" and "w" in the calls to fopen() in pcretest to "rb" and "wb"
1184        for the benefit of those environments where the "b" makes a difference.
1186     6. The icc compiler has the same options as gcc, but "configure" doesn't seem
1187        to know about it. I have put a hack into configure.in that adds in code
1188        to set GCC=yes if CC=icc. This seems to end up at a point in the
1189        generated configure script that is early enough to affect the setting of
1190        compiler options, which is what is needed, but I have no means of testing
1191        whether it really works. (The user who reported this had patched the
1192        generated configure script, which of course I cannot do.)
1194        LATER: After change 22 below (new libtool files), the configure script
1195        seems to know about icc (and also ecc). Therefore, I have commented out
1196        this hack in configure.in.
1198     7. Added support for pkg-config (2 patches were sent in).
1200     8. Negated POSIX character classes that used a combination of internal tables
1201        were completely broken. These were [[:^alpha:]], [[:^alnum:]], and
1202        [[:^ascii]]. Typically, they would match almost any characters. The other
1203        POSIX classes were not broken in this way.
1205     9. Matching the pattern "\b.*?" against "ab cd", starting at offset 1, failed
1206        to find the match, as PCRE was deluded into thinking that the match had to
1207        start at the start point or following a newline. The same bug applied to
1208        patterns with negative forward assertions or any backward assertions
1209        preceding ".*" at the start, unless the pattern required a fixed first
1210        character. This was a failing pattern: "(?!.bcd).*". The bug is now fixed.
1212    10. In UTF-8 mode, when moving forwards in the subject after a failed match
1213        starting at the last subject character, bytes beyond the end of the subject
1214        string were read.
1216    11. Renamed the variable "class" as "classbits" to make life easier for C++
1217        users. (Previously there was a macro definition, but it apparently wasn't
1218        enough.)
1220    12. Added the new field "tables" to the extra data so that tables can be passed
1221        in at exec time, or the internal tables can be re-selected. This allows
1222        a compiled regex to be saved and re-used at a later time by a different
1223        program that might have everything at different addresses.
1225    13. Modified the pcre-config script so that, when run on Solaris, it shows a
1226        -R library as well as a -L library.
1228    14. The debugging options of pcretest (-d on the command line or D on a
1229        pattern) showed incorrect output for anything following an extended class
1230        that contained multibyte characters and which was followed by a quantifier.
1232    15. Added optional support for general category Unicode character properties
1233        via the \p, \P, and \X escapes. Unicode property support implies UTF-8
1234        support. It adds about 90K to the size of the library. The meanings of the
1235        inbuilt class escapes such as \d and \s have NOT been changed.
1237    16. Updated pcredemo.c to include calls to free() to release the memory for the
1238        compiled pattern.
1240    17. The generated file chartables.c was being created in the source directory
1241        instead of in the building directory. This caused the build to fail if the
1242        source directory was different from the building directory, and was
1243        read-only.
1245    18. Added some sample Win commands from Mark Tetrode into the NON-UNIX-USE
1246        file. No doubt somebody will tell me if they don't make sense... Also added
1247        Dan Mooney's comments about building on OpenVMS.
1249    19. Added support for partial matching via the PCRE_PARTIAL option for
1250        pcre_exec() and the \P data escape in pcretest.
1252    20. Extended pcretest with 3 new pattern features:
1254        (i)   A pattern option of the form ">rest-of-line" causes pcretest to
1255              write the compiled pattern to the file whose name is "rest-of-line".
1256              This is a straight binary dump of the data, with the saved pointer to
1257              the character tables forced to be NULL. The study data, if any, is
1258              written too. After writing, pcretest reads a new pattern.
1260        (ii)  If, instead of a pattern, "<rest-of-line" is given, pcretest reads a
1261              compiled pattern from the given file. There must not be any
1262              occurrences of "<" in the file name (pretty unlikely); if there are,
1263              pcretest will instead treat the initial "<" as a pattern delimiter.
1264              After reading in the pattern, pcretest goes on to read data lines as
1265              usual.
1267        (iii) The F pattern option causes pcretest to flip the bytes in the 32-bit
1268              and 16-bit fields in a compiled pattern, to simulate a pattern that
1269              was compiled on a host of opposite endianness.
1271    21. The pcre-exec() function can now cope with patterns that were compiled on
1272        hosts of opposite endianness, with this restriction:
1274          As for any compiled expression that is saved and used later, the tables
1275          pointer field cannot be preserved; the extra_data field in the arguments
1276          to pcre_exec() should be used to pass in a tables address if a value
1277          other than the default internal tables were used at compile time.
1279    22. Calling pcre_exec() with a negative value of the "ovecsize" parameter is
1280        now diagnosed as an error. Previously, most of the time, a negative number
1281        would have been treated as zero, but if in addition "ovector" was passed as
1282        NULL, a crash could occur.
1284    23. Updated the files ltmain.sh, config.sub, config.guess, and aclocal.m4 with
1285        new versions from the libtool 1.5 distribution (the last one is a copy of
1286        a file called libtool.m4). This seems to have fixed the need to patch
1287        "configure" to support Darwin 1.3 (which I used to do). However, I still
1288        had to patch ltmain.sh to ensure that ${SED} is set (it isn't on my
1289        workstation).
1291    24. Changed the PCRE licence to be the more standard "BSD" licence.
1294    Version 4.5 01-Dec-03
1295    ---------------------
1297     1. There has been some re-arrangement of the code for the match() function so
1298        that it can be compiled in a version that does not call itself recursively.
1299        Instead, it keeps those local variables that need separate instances for
1300        each "recursion" in a frame on the heap, and gets/frees frames whenever it
1301        needs to "recurse". Keeping track of where control must go is done by means
1302        of setjmp/longjmp. The whole thing is implemented by a set of macros that
1303        hide most of the details from the main code, and operates only if
1304        NO_RECURSE is defined while compiling pcre.c. If PCRE is built using the
1305        "configure" mechanism, "--disable-stack-for-recursion" turns on this way of
1306        operating.
1308        To make it easier for callers to provide specially tailored get/free
1309        functions for this usage, two new functions, pcre_stack_malloc, and
1310        pcre_stack_free, are used. They are always called in strict stacking order,
1311        and the size of block requested is always the same.
1313        The PCRE_CONFIG_STACKRECURSE info parameter can be used to find out whether
1314        PCRE has been compiled to use the stack or the heap for recursion. The
1315        -C option of pcretest uses this to show which version is compiled.
1317        A new data escape \S, is added to pcretest; it causes the amounts of store
1318        obtained and freed by both kinds of malloc/free at match time to be added
1319        to the output.
1321     2. Changed the locale test to use "fr_FR" instead of "fr" because that's
1322        what's available on my current Linux desktop machine.
1324     3. When matching a UTF-8 string, the test for a valid string at the start has
1325        been extended. If start_offset is not zero, PCRE now checks that it points
1326        to a byte that is the start of a UTF-8 character. If not, it returns
1327        PCRE_ERROR_BADUTF8_OFFSET (-11). Note: the whole string is still checked;
1328        this is necessary because there may be backward assertions in the pattern.
1329        When matching the same subject several times, it may save resources to use
1330        PCRE_NO_UTF8_CHECK on all but the first call if the string is long.
1332     4. The code for checking the validity of UTF-8 strings has been tightened so
1333        that it rejects (a) strings containing 0xfe or 0xff bytes and (b) strings
1334        containing "overlong sequences".
1336     5. Fixed a bug (appearing twice) that I could not find any way of exploiting!
1337        I had written "if ((digitab[*p++] && chtab_digit) == 0)" where the "&&"
1338        should have been "&", but it just so happened that all the cases this let
1339        through by mistake were picked up later in the function.
1341     6. I had used a variable called "isblank" - this is a C99 function, causing
1342        some compilers to warn. To avoid this, I renamed it (as "blankclass").
1344     7. Cosmetic: (a) only output another newline at the end of pcretest if it is
1345        prompting; (b) run "./pcretest /dev/null" at the start of the test script
1346        so the version is shown; (c) stop "make test" echoing "./RunTest".
1348     8. Added patches from David Burgess to enable PCRE to run on EBCDIC systems.
1350     9. The prototype for memmove() for systems that don't have it was using
1351        size_t, but the inclusion of the header that defines size_t was later. I've
1352        moved the #includes for the C headers earlier to avoid this.
1354    10. Added some adjustments to the code to make it easier to compiler on certain
1355        special systems:
1357          (a) Some "const" qualifiers were missing.
1358          (b) Added the macro EXPORT before all exported functions; by default this
1359              is defined to be empty.
1360          (c) Changed the dftables auxiliary program (that builds chartables.c) so
1361              that it reads its output file name as an argument instead of writing
1362              to the standard output and assuming this can be redirected.
1364    11. In UTF-8 mode, if a recursive reference (e.g. (?1)) followed a character
1365        class containing characters with values greater than 255, PCRE compilation
1366        went into a loop.
1368    12. A recursive reference to a subpattern that was within another subpattern
1369        that had a minimum quantifier of zero caused PCRE to crash. For example,
1370        (x(y(?2))z)? provoked this bug with a subject that got as far as the
1371        recursion. If the recursively-called subpattern itself had a zero repeat,
1372        that was OK.
1374    13. In pcretest, the buffer for reading a data line was set at 30K, but the
1375        buffer into which it was copied (for escape processing) was still set at
1376        1024, so long lines caused crashes.
1378    14. A pattern such as /[ab]{1,3}+/ failed to compile, giving the error
1379        "internal error: code overflow...". This applied to any character class
1380        that was followed by a possessive quantifier.
1382    15. Modified the Makefile to add libpcre.la as a prerequisite for
1383        libpcreposix.la because I was told this is needed for a parallel build to
1384        work.
1386    16. If a pattern that contained .* following optional items at the start was
1387        studied, the wrong optimizing data was generated, leading to matching
1388        errors. For example, studying /[ab]*.*c/ concluded, erroneously, that any
1389        matching string must start with a or b or c. The correct conclusion for
1390        this pattern is that a match can start with any character.
1393    Version 4.4 13-Aug-03
1394    ---------------------
1396     1. In UTF-8 mode, a character class containing characters with values between
1397        127 and 255 was not handled correctly if the compiled pattern was studied.
1398        In fixing this, I have also improved the studying algorithm for such
1399        classes (slightly).
1401     2. Three internal functions had redundant arguments passed to them. Removal
1402        might give a very teeny performance improvement.
1404     3. Documentation bug: the value of the capture_top field in a callout is *one
1405        more than* the number of the hightest numbered captured substring.
1407     4. The Makefile linked pcretest and pcregrep with -lpcre, which could result
1408        in incorrectly linking with a previously installed version. They now link
1409        explicitly with libpcre.la.
1411     5. configure.in no longer needs to recognize Cygwin specially.
1413     6. A problem in pcre.in for Windows platforms is fixed.
1415     7. If a pattern was successfully studied, and the -d (or /D) flag was given to
1416        pcretest, it used to include the size of the study block as part of its
1417        output. Unfortunately, the structure contains a field that has a different
1418        size on different hardware architectures. This meant that the tests that
1419        showed this size failed. As the block is currently always of a fixed size,
1420        this information isn't actually particularly useful in pcretest output, so
1421        I have just removed it.
1423     8. Three pre-processor statements accidentally did not start in column 1.
1424        Sadly, there are *still* compilers around that complain, even though
1425        standard C has not required this for well over a decade. Sigh.
1427     9. In pcretest, the code for checking callouts passed small integers in the
1428        callout_data field, which is a void * field. However, some picky compilers
1429        complained about the casts involved for this on 64-bit systems. Now
1430        pcretest passes the address of the small integer instead, which should get
1431        rid of the warnings.
1433    10. By default, when in UTF-8 mode, PCRE now checks for valid UTF-8 strings at
1434        both compile and run time, and gives an error if an invalid UTF-8 sequence
1435        is found. There is a option for disabling this check in cases where the
1436        string is known to be correct and/or the maximum performance is wanted.
1438    11. In response to a bug report, I changed one line in Makefile.in from
1440            -Wl,--out-implib,.libs/lib@WIN_PREFIX@pcreposix.dll.a \
1441        to
1442            -Wl,--out-implib,.libs/@WIN_PREFIX@libpcreposix.dll.a \
1444        to look similar to other lines, but I have no way of telling whether this
1445        is the right thing to do, as I do not use Windows. No doubt I'll get told
1446        if it's wrong...
1449    Version 4.3 21-May-03
1450    ---------------------
1452    1. Two instances of @WIN_PREFIX@ omitted from the Windows targets in the
1453       Makefile.
1455    2. Some refactoring to improve the quality of the code:
1457       (i)   The utf8_table... variables are now declared "const".
1459       (ii)  The code for \cx, which used the "case flipping" table to upper case
1460             lower case letters, now just substracts 32. This is ASCII-specific,
1461             but the whole concept of \cx is ASCII-specific, so it seems
1462             reasonable.
1464       (iii) PCRE was using its character types table to recognize decimal and
1465             hexadecimal digits in the pattern. This is silly, because it handles
1466             only 0-9, a-f, and A-F, but the character types table is locale-
1467             specific, which means strange things might happen. A private
1468             table is now used for this - though it costs 256 bytes, a table is
1469             much faster than multiple explicit tests. Of course, the standard
1470             character types table is still used for matching digits in subject
1471             strings against \d.
1473       (iv)  Strictly, the identifier ESC_t is reserved by POSIX (all identifiers
1474             ending in _t are). So I've renamed it as ESC_tee.
1476    3. The first argument for regexec() in the POSIX wrapper should have been
1477       defined as "const".
1479    4. Changed pcretest to use malloc() for its buffers so that they can be
1480       Electric Fenced for debugging.
1482    5. There were several places in the code where, in UTF-8 mode, PCRE would try
1483       to read one or more bytes before the start of the subject string. Often this
1484       had no effect on PCRE's behaviour, but in some circumstances it could
1485       provoke a segmentation fault.
1487    6. A lookbehind at the start of a pattern in UTF-8 mode could also cause PCRE
1488       to try to read one or more bytes before the start of the subject string.
1490    7. A lookbehind in a pattern matched in non-UTF-8 mode on a PCRE compiled with
1491       UTF-8 support could misbehave in various ways if the subject string
1492       contained bytes with the 0x80 bit set and the 0x40 bit unset in a lookbehind
1493       area. (PCRE was not checking for the UTF-8 mode flag, and trying to move
1494       back over UTF-8 characters.)
1497    Version 4.2 14-Apr-03
1498    ---------------------
1500    1. Typo "#if SUPPORT_UTF8" instead of "#ifdef SUPPORT_UTF8" fixed.
1502    2. Changes to the building process, supplied by Ronald Landheer-Cieslak
1503         [ON_WINDOWS]: new variable, "#" on non-Windows platforms
1504         [NOT_ON_WINDOWS]: new variable, "#" on Windows platforms
1505         [WIN_PREFIX]: new variable, "cyg" for Cygwin
1506         * Makefile.in: use autoconf substitution for OBJEXT, EXEEXT, BUILD_OBJEXT
1507           and BUILD_EXEEXT
1508         Note: automatic setting of the BUILD variables is not yet working
1509         set CPPFLAGS and BUILD_CPPFLAGS (but don't use yet) - should be used at
1510           compile-time but not at link-time
1511         [LINK]: use for linking executables only
1512         make different versions for Windows and non-Windows
1513         [LINKLIB]: new variable, copy of UNIX-style LINK, used for linking
1514           libraries
1515         [LINK_FOR_BUILD]: new variable
1516         [OBJEXT]: use throughout
1517         [EXEEXT]: use throughout
1518         <winshared>: new target
1519         <wininstall>: new target
1520         <dftables.o>: use native compiler
1521         <dftables>: use native linker
1522         <install>: handle Windows platform correctly
1523         <clean>: ditto
1524         <check>: ditto
1525         copy DLL to top builddir before testing
1527       As part of these changes, -no-undefined was removed again. This was reported
1528       to give trouble on HP-UX 11.0, so getting rid of it seems like a good idea
1529       in any case.
1531    3. Some tidies to get rid of compiler warnings:
1533       . In the match_data structure, match_limit was an unsigned long int, whereas
1534         match_call_count was an int. I've made them both unsigned long ints.
1536       . In pcretest the fact that a const uschar * doesn't automatically cast to
1537         a void * provoked a warning.
1539       . Turning on some more compiler warnings threw up some "shadow" variables
1540         and a few more missing casts.
1542    4. If PCRE was complied with UTF-8 support, but called without the PCRE_UTF8
1543       option, a class that contained a single character with a value between 128
1544       and 255 (e.g. /[\xFF]/) caused PCRE to crash.
1546    5. If PCRE was compiled with UTF-8 support, but called without the PCRE_UTF8
1547       option, a class that contained several characters, but with at least one
1548       whose value was between 128 and 255 caused PCRE to crash.
1551    Version 4.1 12-Mar-03
1552    ---------------------
1554    1. Compiling with gcc -pedantic found a couple of places where casts were
1555    needed, and a string in dftables.c that was longer than standard compilers are
1556    required to support.
1558    2. Compiling with Sun's compiler found a few more places where the code could
1559    be tidied up in order to avoid warnings.
1561    3. The variables for cross-compiling were called HOST_CC and HOST_CFLAGS; the
1562    first of these names is deprecated in the latest Autoconf in favour of the name
1563    CC_FOR_BUILD, because "host" is typically used to mean the system on which the
1564    compiled code will be run. I can't find a reference for HOST_CFLAGS, but by
1565    analogy I have changed it to CFLAGS_FOR_BUILD.
1567    4. Added -no-undefined to the linking command in the Makefile, because this is
1568    apparently helpful for Windows. To make it work, also added "-L. -lpcre" to the
1569    linking step for the pcreposix library.
1571    5. PCRE was failing to diagnose the case of two named groups with the same
1572    name.
1574    6. A problem with one of PCRE's optimizations was discovered. PCRE remembers a
1575    literal character that is needed in the subject for a match, and scans along to
1576    ensure that it is present before embarking on the full matching process. This
1577    saves time in cases of nested unlimited repeats that are never going to match.
1578    Problem: the scan can take a lot of time if the subject is very long (e.g.
1579    megabytes), thus penalizing straightforward matches. It is now done only if the
1580    amount of subject to be scanned is less than 1000 bytes.
1582    7. A lesser problem with the same optimization is that it was recording the
1583    first character of an anchored pattern as "needed", thus provoking a search
1584    right along the subject, even when the first match of the pattern was going to
1585    fail. The "needed" character is now not set for anchored patterns, unless it
1586    follows something in the pattern that is of non-fixed length. Thus, it still
1587    fulfils its original purpose of finding quick non-matches in cases of nested
1588    unlimited repeats, but isn't used for simple anchored patterns such as /^abc/.
1591    Version 4.0 17-Feb-03
1592    ---------------------
1594    1. If a comment in an extended regex that started immediately after a meta-item
1595    extended to the end of string, PCRE compiled incorrect data. This could lead to
1596    all kinds of weird effects. Example: /#/ was bad; /()#/ was bad; /a#/ was not.
1598    2. Moved to autoconf 2.53 and libtool 1.4.2.
1600    3. Perl 5.8 no longer needs "use utf8" for doing UTF-8 things. Consequently,
1601    the special perltest8 script is no longer needed - all the tests can be run
1602    from a single perltest script.
1604    4. From 5.004, Perl has not included the VT character (0x0b) in the set defined
1605    by \s. It has now been removed in PCRE. This means it isn't recognized as
1606    whitespace in /x regexes too, which is the same as Perl. Note that the POSIX
1607    class [:space:] *does* include VT, thereby creating a mess.
1609    5. Added the class [:blank:] (a GNU extension from Perl 5.8) to match only
1610    space and tab.
1612    6. Perl 5.005 was a long time ago. It's time to amalgamate the tests that use
1613    its new features into the main test script, reducing the number of scripts.
1615    7. Perl 5.8 has changed the meaning of patterns like /a(?i)b/. Earlier versions
1616    were backward compatible, and made the (?i) apply to the whole pattern, as if
1617    /i were given. Now it behaves more logically, and applies the option setting
1618    only to what follows. PCRE has been changed to follow suit. However, if it
1619    finds options settings right at the start of the pattern, it extracts them into
1620    the global options, as before. Thus, they show up in the info data.
1622    8. Added support for the \Q...\E escape sequence. Characters in between are
1623    treated as literals. This is slightly different from Perl in that $ and @ are
1624    also handled as literals inside the quotes. In Perl, they will cause variable
1625    interpolation. Note the following examples:
1627        Pattern            PCRE matches      Perl matches
1629        \Qabc$xyz\E        abc$xyz           abc followed by the contents of $xyz
1630        \Qabc\$xyz\E       abc\$xyz          abc\$xyz
1631        \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
1633    For compatibility with Perl, \Q...\E sequences are recognized inside character
1634    classes as well as outside them.
1636    9. Re-organized 3 code statements in pcretest to avoid "overflow in
1637    floating-point constant arithmetic" warnings from a Microsoft compiler. Added a
1638    (size_t) cast to one statement in pcretest and one in pcreposix to avoid
1639    signed/unsigned warnings.
1641    10. SunOS4 doesn't have strtoul(). This was used only for unpicking the -o
1642    option for pcretest, so I've replaced it by a simple function that does just
1643    that job.
1645    11. pcregrep was ending with code 0 instead of 2 for the commands "pcregrep" or
1646    "pcregrep -".
1648    12. Added "possessive quantifiers" ?+, *+, ++, and {,}+ which come from Sun's
1649    Java package. This provides some syntactic sugar for simple cases of what my
1650    documentation calls "once-only subpatterns". A pattern such as x*+ is the same
1651    as (?>x*). In other words, if what is inside (?>...) is just a single repeated
1652    item, you can use this simplified notation. Note that only makes sense with
1653    greedy quantifiers. Consequently, the use of the possessive quantifier forces
1654    greediness, whatever the setting of the PCRE_UNGREEDY option.
1656    13. A change of greediness default within a pattern was not taking effect at
1657    the current level for patterns like /(b+(?U)a+)/. It did apply to parenthesized
1658    subpatterns that followed. Patterns like /b+(?U)a+/ worked because the option
1659    was abstracted outside.
1661    14. PCRE now supports the \G assertion. It is true when the current matching
1662    position is at the start point of the match. This differs from \A when the
1663    starting offset is non-zero. Used with the /g option of pcretest (or similar
1664    code), it works in the same way as it does for Perl's /g option. If all
1665    alternatives of a regex begin with \G, the expression is anchored to the start
1666    match position, and the "anchored" flag is set in the compiled expression.
1668    15. Some bugs concerning the handling of certain option changes within patterns
1669    have been fixed. These applied to options other than (?ims). For example,
1670    "a(?x: b c )d" did not match "XabcdY" but did match "Xa b c dY". It should have
1671    been the other way round. Some of this was related to change 7 above.
1673    16. PCRE now gives errors for /[.x.]/ and /[=x=]/ as unsupported POSIX
1674    features, as Perl does. Previously, PCRE gave the warnings only for /[[.x.]]/
1675    and /[[=x=]]/. PCRE now also gives an error for /[:name:]/ because it supports
1676    POSIX classes only within a class (e.g. /[[:alpha:]]/).
1678    17. Added support for Perl's \C escape. This matches one byte, even in UTF8
1679    mode. Unlike ".", it always matches newline, whatever the setting of
1680    PCRE_DOTALL. However, PCRE does not permit \C to appear in lookbehind
1681    assertions. Perl allows it, but it doesn't (in general) work because it can't
1682    calculate the length of the lookbehind. At least, that's the case for Perl
1683    5.8.0 - I've been told they are going to document that it doesn't work in
1684    future.
1686    18. Added an error diagnosis for escapes that PCRE does not support: these are
1687    \L, \l, \N, \P, \p, \U, \u, and \X.
1689    19. Although correctly diagnosing a missing ']' in a character class, PCRE was
1690    reading past the end of the pattern in cases such as /[abcd/.
1692    20. PCRE was getting more memory than necessary for patterns with classes that
1693    contained both POSIX named classes and other characters, e.g. /[[:space:]abc/.
1695    21. Added some code, conditional on #ifdef VPCOMPAT, to make life easier for
1696    compiling PCRE for use with Virtual Pascal.
1698    22. Small fix to the Makefile to make it work properly if the build is done
1699    outside the source tree.
1701    23. Added a new extension: a condition to go with recursion. If a conditional
1702    subpattern starts with (?(R) the "true" branch is used if recursion has
1703    happened, whereas the "false" branch is used only at the top level.
1705    24. When there was a very long string of literal characters (over 255 bytes
1706    without UTF support, over 250 bytes with UTF support), the computation of how
1707    much memory was required could be incorrect, leading to segfaults or other
1708    strange effects.
1710    25. PCRE was incorrectly assuming anchoring (either to start of subject or to
1711    start of line for a non-DOTALL pattern) when a pattern started with (.*) and
1712    there was a subsequent back reference to those brackets. This meant that, for
1713    example, /(.*)\d+\1/ failed to match "abc123bc". Unfortunately, it isn't
1714    possible to check for precisely this case. All we can do is abandon the
1715    optimization if .* occurs inside capturing brackets when there are any back
1716    references whatsoever. (See below for a better fix that came later.)
1718    26. The handling of the optimization for finding the first character of a
1719    non-anchored pattern, and for finding a character that is required later in the
1720    match were failing in some cases. This didn't break the matching; it just
1721    failed to optimize when it could. The way this is done has been re-implemented.
1723    27. Fixed typo in error message for invalid (?R item (it said "(?p").
1725    28. Added a new feature that provides some of the functionality that Perl
1726    provides with (?{...}). The facility is termed a "callout". The way it is done
1727    in PCRE is for the caller to provide an optional function, by setting
1728    pcre_callout to its entry point. Like pcre_malloc and pcre_free, this is a
1729    global variable. By default it is unset, which disables all calling out. To get
1730    the function called, the regex must include (?C) at appropriate points. This
1731    is, in fact, equivalent to (?C0), and any number <= 255 may be given with (?C).
1732    This provides a means of identifying different callout points. When PCRE
1733    reaches such a point in the regex, if pcre_callout has been set, the external
1734    function is called. It is provided with data in a structure called
1735    pcre_callout_block, which is defined in pcre.h. If the function returns 0,
1736    matching continues; if it returns a non-zero value, the match at the current
1737    point fails. However, backtracking will occur if possible. [This was changed
1738    later and other features added - see item 49 below.]
1740    29. pcretest is upgraded to test the callout functionality. It provides a
1741    callout function that displays information. By default, it shows the start of
1742    the match and the current position in the text. There are some new data escapes
1743    to vary what happens:
1745        \C+         in addition, show current contents of captured substrings
1746        \C-         do not supply a callout function
1747        \C!n        return 1 when callout number n is reached
1748        \C!n!m      return 1 when callout number n is reached for the mth time
1750    30. If pcregrep was called with the -l option and just a single file name, it
1751    output "<stdin>" if a match was found, instead of the file name.
1753    31. Improve the efficiency of the POSIX API to PCRE. If the number of capturing
1754    slots is less than POSIX_MALLOC_THRESHOLD, use a block on the stack to pass to
1755    pcre_exec(). This saves a malloc/free per call. The default value of
1756    POSIX_MALLOC_THRESHOLD is 10; it can be changed by --with-posix-malloc-threshold
1757    when configuring.
1759    32. The default maximum size of a compiled pattern is 64K. There have been a
1760    few cases of people hitting this limit. The code now uses macros to handle the
1761    storing of links as offsets within the compiled pattern. It defaults to 2-byte
1762    links, but this can be changed to 3 or 4 bytes by --with-link-size when
1763    configuring. Tests 2 and 5 work only with 2-byte links because they output
1764    debugging information about compiled patterns.
1766    33. Internal code re-arrangements:
1768    (a) Moved the debugging function for printing out a compiled regex into
1769        its own source file (printint.c) and used #include to pull it into
1770        pcretest.c and, when DEBUG is defined, into pcre.c, instead of having two
1771        separate copies.
1773    (b) Defined the list of op-code names for debugging as a macro in
1774        internal.h so that it is next to the definition of the opcodes.
1776    (c) Defined a table of op-code lengths for simpler skipping along compiled
1777        code. This is again a macro in internal.h so that it is next to the
1778        definition of the opcodes.
1780    34. Added support for recursive calls to individual subpatterns, along the
1781    lines of Robin Houston's patch (but implemented somewhat differently).
1783    35. Further mods to the Makefile to help Win32. Also, added code to pcregrep to
1784    allow it to read and process whole directories in Win32. This code was
1785    contributed by Lionel Fourquaux; it has not been tested by me.
1787    36. Added support for named subpatterns. The Python syntax (?P<name>...) is
1788    used to name a group. Names consist of alphanumerics and underscores, and must
1789    be unique. Back references use the syntax (?P=name) and recursive calls use
1790    (?P>name) which is a PCRE extension to the Python extension. Groups still have
1791    numbers. The function pcre_fullinfo() can be used after compilation to extract
1792    a name/number map. There are three relevant calls:
1794      PCRE_INFO_NAMEENTRYSIZE        yields the size of each entry in the map
1795      PCRE_INFO_NAMECOUNT            yields the number of entries
1796      PCRE_INFO_NAMETABLE            yields a pointer to the map.
1798    The map is a vector of fixed-size entries. The size of each entry depends on
1799    the length of the longest name used. The first two bytes of each entry are the
1800    group number, most significant byte first. There follows the corresponding
1801    name, zero terminated. The names are in alphabetical order.
1803    37. Make the maximum literal string in the compiled code 250 for the non-UTF-8
1804    case instead of 255. Making it the same both with and without UTF-8 support
1805    means that the same test output works with both.
1807    38. There was a case of malloc(0) in the POSIX testing code in pcretest. Avoid
1808    calling malloc() with a zero argument.
1810    39. Change 25 above had to resort to a heavy-handed test for the .* anchoring
1811    optimization. I've improved things by keeping a bitmap of backreferences with
1812    numbers 1-31 so that if .* occurs inside capturing brackets that are not in
1813    fact referenced, the optimization can be applied. It is unlikely that a
1814    relevant occurrence of .* (i.e. one which might indicate anchoring or forcing
1815    the match to follow \n) will appear inside brackets with a number greater than
1816    31, but if it does, any back reference > 31 suppresses the optimization.
1818    40. Added a new compile-time option PCRE_NO_AUTO_CAPTURE. This has the effect
1819    of disabling numbered capturing parentheses. Any opening parenthesis that is
1820    not followed by ? behaves as if it were followed by ?: but named parentheses
1821    can still be used for capturing (and they will acquire numbers in the usual
1822    way).
1824    41. Redesigned the return codes from the match() function into yes/no/error so
1825    that errors can be passed back from deep inside the nested calls. A malloc
1826    failure while inside a recursive subpattern call now causes the
1827    PCRE_ERROR_NOMEMORY return instead of quietly going wrong.
1829    42. It is now possible to set a limit on the number of times the match()
1830    function is called in a call to pcre_exec(). This facility makes it possible to
1831    limit the amount of recursion and backtracking, though not in a directly
1832    obvious way, because the match() function is used in a number of different
1833    circumstances. The count starts from zero for each position in the subject
1834    string (for non-anchored patterns). The default limit is, for compatibility, a
1835    large number, namely 10 000 000. You can change this in two ways:
1837    (a) When configuring PCRE before making, you can use --with-match-limit=n
1838        to set a default value for the compiled library.
1840    (b) For each call to pcre_exec(), you can pass a pcre_extra block in which
1841        a different value is set. See 45 below.
1843    If the limit is exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
1845    43. Added a new function pcre_config(int, void *) to enable run-time extraction
1846    of things that can be changed at compile time. The first argument specifies
1847    what is wanted and the second points to where the information is to be placed.
1848    The current list of available information is:
1850      PCRE_CONFIG_UTF8
1852    The output is an integer that is set to one if UTF-8 support is available;
1853    otherwise it is set to zero.
1857    The output is an integer that it set to the value of the code that is used for
1858    newline. It is either LF (10) or CR (13).
1862    The output is an integer that contains the number of bytes used for internal
1863    linkage in compiled expressions. The value is 2, 3, or 4. See item 32 above.
1867    The output is an integer that contains the threshold above which the POSIX
1868    interface uses malloc() for output vectors. See item 31 above.
1872    The output is an unsigned integer that contains the default limit of the number
1873    of match() calls in a pcre_exec() execution. See 42 above.
1875    44. pcretest has been upgraded by the addition of the -C option. This causes it
1876    to extract all the available output from the new pcre_config() function, and to
1877    output it. The program then exits immediately.
1879    45. A need has arisen to pass over additional data with calls to pcre_exec() in
1880    order to support additional features. One way would have been to define
1881    pcre_exec2() (for example) with extra arguments, but this would not have been
1882    extensible, and would also have required all calls to the original function to
1883    be mapped to the new one. Instead, I have chosen to extend the mechanism that
1884    is used for passing in "extra" data from pcre_study().
1886    The pcre_extra structure is now exposed and defined in pcre.h. It currently
1887    contains the following fields:
1889      flags         a bitmap indicating which of the following fields are set
1890      study_data    opaque data from pcre_study()
1891      match_limit   a way of specifying a limit on match() calls for a specific
1892                      call to pcre_exec()
1893      callout_data  data for callouts (see 49 below)
1895    The flag bits are also defined in pcre.h, and are
1901    The pcre_study() function now returns one of these new pcre_extra blocks, with
1902    the actual study data pointed to by the study_data field, and the
1903    PCRE_EXTRA_STUDY_DATA flag set. This can be passed directly to pcre_exec() as
1904    before. That is, this change is entirely upwards-compatible and requires no
1905    change to existing code.
1907    If you want to pass in additional data to pcre_exec(), you can either place it
1908    in a pcre_extra block provided by pcre_study(), or create your own pcre_extra
1909    block.
1911    46. pcretest has been extended to test the PCRE_EXTRA_MATCH_LIMIT feature. If a
1912    data string contains the escape sequence \M, pcretest calls pcre_exec() several
1913    times with different match limits, until it finds the minimum value needed for
1914    pcre_exec() to complete. The value is then output. This can be instructive; for
1915    most simple matches the number is quite small, but for pathological cases it
1916    gets very large very quickly.
1918    47. There's a new option for pcre_fullinfo() called PCRE_INFO_STUDYSIZE. It
1919    returns the size of the data block pointed to by the study_data field in a
1920    pcre_extra block, that is, the value that was passed as the argument to
1921    pcre_malloc() when PCRE was getting memory in which to place the information
1922    created by pcre_study(). The fourth argument should point to a size_t variable.
1923    pcretest has been extended so that this information is shown after a successful
1924    pcre_study() call when information about the compiled regex is being displayed.
1926    48. Cosmetic change to Makefile: there's no need to have / after $(DESTDIR)
1927    because what follows is always an absolute path. (Later: it turns out that this
1928    is more than cosmetic for MinGW, because it doesn't like empty path
1929    components.)
1931    49. Some changes have been made to the callout feature (see 28 above):
1933    (i)  A callout function now has three choices for what it returns:
1935           0  =>  success, carry on matching
1936         > 0  =>  failure at this point, but backtrack if possible
1937         < 0  =>  serious error, return this value from pcre_exec()
1939         Negative values should normally be chosen from the set of PCRE_ERROR_xxx
1940         values. In particular, returning PCRE_ERROR_NOMATCH forces a standard
1941         "match failed" error. The error number PCRE_ERROR_CALLOUT is reserved for
1942         use by callout functions. It will never be used by PCRE itself.
1944    (ii) The pcre_extra structure (see 45 above) has a void * field called
1945         callout_data, with corresponding flag bit PCRE_EXTRA_CALLOUT_DATA. The
1946         pcre_callout_block structure has a field of the same name. The contents of
1947         the field passed in the pcre_extra structure are passed to the callout
1948         function in the corresponding field in the callout block. This makes it
1949         easier to use the same callout-containing regex from multiple threads. For
1950         testing, the pcretest program has a new data escape
1952           \C*n        pass the number n (may be negative) as callout_data
1954         If the callout function in pcretest receives a non-zero value as
1955         callout_data, it returns that value.
1957    50. Makefile wasn't handling CFLAGS properly when compiling dftables. Also,
1958    there were some redundant $(CFLAGS) in commands that are now specified as
1959    $(LINK), which already includes $(CFLAGS).
1961    51. Extensions to UTF-8 support are listed below. These all apply when (a) PCRE
1962    has been compiled with UTF-8 support *and* pcre_compile() has been compiled
1963    with the PCRE_UTF8 flag. Patterns that are compiled without that flag assume
1964    one-byte characters throughout. Note that case-insensitive matching applies
1965    only to characters whose values are less than 256. PCRE doesn't support the
1966    notion of cases for higher-valued characters.
1968    (i)   A character class whose characters are all within 0-255 is handled as
1969          a bit map, and the map is inverted for negative classes. Previously, a
1970          character > 255 always failed to match such a class; however it should
1971          match if the class was a negative one (e.g. [^ab]). This has been fixed.
1973    (ii)  A negated character class with a single character < 255 is coded as
1974          "not this character" (OP_NOT). This wasn't working properly when the test
1975          character was multibyte, either singly or repeated.
1977    (iii) Repeats of multibyte characters are now handled correctly in UTF-8
1978          mode, for example: \x{100}{2,3}.
1980    (iv)  The character escapes \b, \B, \d, \D, \s, \S, \w, and \W (either
1981          singly or repeated) now correctly test multibyte characters. However,
1982          PCRE doesn't recognize any characters with values greater than 255 as
1983          digits, spaces, or word characters. Such characters always match \D, \S,
1984          and \W, and never match \d, \s, or \w.
1986    (v)   Classes may now contain characters and character ranges with values
1987          greater than 255. For example: [ab\x{100}-\x{400}].
1989    (vi)  pcregrep now has a --utf-8 option (synonym -u) which makes it call
1990          PCRE in UTF-8 mode.
1992    52. The info request value PCRE_INFO_FIRSTCHAR has been renamed
1993    PCRE_INFO_FIRSTBYTE because it is a byte value. However, the old name is
1994    retained for backwards compatibility. (Note that LASTLITERAL is also a byte
1995    value.)
1997    53. The single man page has become too large. I have therefore split it up into
1998    a number of separate man pages. These also give rise to individual HTML pages;
1999    these are now put in a separate directory, and there is an index.html page that
2000    lists them all. Some hyperlinking between the pages has been installed.
2002    54. Added convenience functions for handling named capturing parentheses.
2004    55. Unknown escapes inside character classes (e.g. [\M]) and escapes that
2005    aren't interpreted therein (e.g. [\C]) are literals in Perl. This is now also
2006    true in PCRE, except when the PCRE_EXTENDED option is set, in which case they
2007    are faulted.
2009    56. Introduced HOST_CC and HOST_CFLAGS which can be set in the environment when
2010    calling configure. These values are used when compiling the dftables.c program
2011    which is run to generate the source of the default character tables. They
2012    default to the values of CC and CFLAGS. If you are cross-compiling PCRE,
2013    you will need to set these values.
2015    57. Updated the building process for Windows DLL, as provided by Fred Cox.
2018    Version 3.9 02-Jan-02
2019    ---------------------
2021    1. A bit of extraneous text had somehow crept into the pcregrep documentation.
2023    2. If --disable-static was given, the building process failed when trying to
2024    build pcretest and pcregrep. (For some reason it was using libtool to compile
2025    them, which is not right, as they aren't part of the library.)
2028    Version 3.8 18-Dec-01
2029    ---------------------
2031    1. The experimental UTF-8 code was completely screwed up. It was packing the
2032    bytes in the wrong order. How dumb can you get?
2035    Version 3.7 29-Oct-01
2036    ---------------------
2038    1. In updating pcretest to check change 1 of version 3.6, I screwed up.
2039    This caused pcretest, when used on the test data, to segfault. Unfortunately,
2040    this didn't happen under Solaris 8, where I normally test things.
2042    2. The Makefile had to be changed to make it work on BSD systems, where 'make'
2043    doesn't seem to recognize that ./xxx and xxx are the same file. (This entry
2044    isn't in ChangeLog distributed with 3.7 because I forgot when I hastily made
2045    this fix an hour or so after the initial 3.7 release.)
2048    Version 3.6 23-Oct-01
2049    ---------------------
2051    1. Crashed with /(sens|respons)e and \1ibility/ and "sense and sensibility" if
2052    offsets passed as NULL with zero offset count.
2054    2. The config.guess and config.sub files had not been updated when I moved to
2055    the latest autoconf.
2058    Version 3.5 15-Aug-01
2059    ---------------------
2061    1. Added some missing #if !defined NOPOSIX conditionals in pcretest.c that
2062    had been forgotten.
2064    2. By using declared but undefined structures, we can avoid using "void"
2065    definitions in pcre.h while keeping the internal definitions of the structures
2066    private.
2068    3. The distribution is now built using autoconf 2.50 and libtool 1.4. From a
2069    user point of view, this means that both static and shared libraries are built
2070    by default, but this can be individually controlled. More of the work of
2071    handling this static/shared cases is now inside libtool instead of PCRE's make
2072    file.
2074    4. The pcretest utility is now installed along with pcregrep because it is
2075    useful for users (to test regexs) and by doing this, it automatically gets
2076    relinked by libtool. The documentation has been turned into a man page, so
2077    there are now .1, .txt, and .html versions in /doc.
2079    5. Upgrades to pcregrep:
2080       (i)   Added long-form option names like gnu grep.
2081       (ii)  Added --help to list all options with an explanatory phrase.
2082       (iii) Added -r, --recursive to recurse into sub-directories.
2083       (iv)  Added -f, --file to read patterns from a file.
2085    6. pcre_exec() was referring to its "code" argument before testing that
2086    argument for NULL (and giving an error if it was NULL).
2088    7. Upgraded Makefile.in to allow for compiling in a different directory from
2089    the source directory.
2091    8. Tiny buglet in pcretest: when pcre_fullinfo() was called to retrieve the
2092    options bits, the pointer it was passed was to an int instead of to an unsigned
2093    long int. This mattered only on 64-bit systems.
2095    9. Fixed typo (3.4/1) in pcre.h again. Sigh. I had changed pcre.h (which is
2096    generated) instead of pcre.in, which it its source. Also made the same change
2097    in several of the .c files.
2099    10. A new release of gcc defines printf() as a macro, which broke pcretest
2100    because it had an ifdef in the middle of a string argument for printf(). Fixed
2101    by using separate calls to printf().
2103    11. Added --enable-newline-is-cr and --enable-newline-is-lf to the configure
2104    script, to force use of CR or LF instead of \n in the source. On non-Unix
2105    systems, the value can be set in config.h.
2107    12. The limit of 200 on non-capturing parentheses is a _nesting_ limit, not an
2108    absolute limit. Changed the text of the error message to make this clear, and
2109    likewise updated the man page.
2111    13. The limit of 99 on the number of capturing subpatterns has been removed.
2112    The new limit is 65535, which I hope will not be a "real" limit.
2115    Version 3.4 22-Aug-00
2116    ---------------------
2118    1. Fixed typo in pcre.h: unsigned const char * changed to const unsigned char *.
2120    2. Diagnose condition (?(0) as an error instead of crashing on matching.
2123  Version 3.3 01-Aug-00  Version 3.3 01-Aug-00
2124  ---------------------  ---------------------

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