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revision 71 by nigel, Sat Feb 24 21:40:24 2007 UTC revision 230 by ph10, Mon Sep 10 13:23:56 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4    Version 7.4 10-Sep-07
5    ---------------------
6    
7    1.  Change 7.3/28 was implemented for classes by looking at the bitmap. This
8        means that a class such as [\s] counted as "explicit reference to CR or
9        LF". That isn't really right - the whole point of the change was to try to
10        help when there was an actual mention of one of the two characters. So now
11        the change happens only if \r or \n (or a literal CR or LF) character is
12        encountered.
13    
14    2.  The 32-bit options word was also used for 6 internal flags, but the numbers
15        of both had grown to the point where there were only 3 bits left.
16        Fortunately, there was spare space in the data structure, and so I have
17        moved the internal flags into a new 16-bit field to free up more option
18        bits.
19    
20    3.  The appearance of (?J) at the start of a pattern set the DUPNAMES option,
21        but did not set the internal JCHANGED flag - either of these is enough to
22        control the way the "get" function works - but the PCRE_INFO_JCHANGED
23        facility is supposed to tell if (?J) was ever used, so now (?J) at the
24        start sets both bits.
25    
26    
27    Version 7.3 28-Aug-07
28    ---------------------
29    
30     1. In the rejigging of the build system that eventually resulted in 7.1, the
31        line "#include <pcre.h>" was included in pcre_internal.h. The use of angle
32        brackets there is not right, since it causes compilers to look for an
33        installed pcre.h, not the version that is in the source that is being
34        compiled (which of course may be different). I have changed it back to:
35    
36          #include "pcre.h"
37    
38        I have a vague recollection that the change was concerned with compiling in
39        different directories, but in the new build system, that is taken care of
40        by the VPATH setting the Makefile.
41    
42     2. The pattern .*$ when run in not-DOTALL UTF-8 mode with newline=any failed
43        when the subject happened to end in the byte 0x85 (e.g. if the last
44        character was \x{1ec5}). *Character* 0x85 is one of the "any" newline
45        characters but of course it shouldn't be taken as a newline when it is part
46        of another character. The bug was that, for an unlimited repeat of . in
47        not-DOTALL UTF-8 mode, PCRE was advancing by bytes rather than by
48        characters when looking for a newline.
49    
50     3. A small performance improvement in the DOTALL UTF-8 mode .* case.
51    
52     4. Debugging: adjusted the names of opcodes for different kinds of parentheses
53        in debug output.
54    
55     5. Arrange to use "%I64d" instead of "%lld" and "%I64u" instead of "%llu" for
56        long printing in the pcrecpp unittest when running under MinGW.
57    
58     6. ESC_K was left out of the EBCDIC table.
59    
60     7. Change 7.0/38 introduced a new limit on the number of nested non-capturing
61        parentheses; I made it 1000, which seemed large enough. Unfortunately, the
62        limit also applies to "virtual nesting" when a pattern is recursive, and in
63        this case 1000 isn't so big. I have been able to remove this limit at the
64        expense of backing off one optimization in certain circumstances. Normally,
65        when pcre_exec() would call its internal match() function recursively and
66        immediately return the result unconditionally, it uses a "tail recursion"
67        feature to save stack. However, when a subpattern that can match an empty
68        string has an unlimited repetition quantifier, it no longer makes this
69        optimization. That gives it a stack frame in which to save the data for
70        checking that an empty string has been matched. Previously this was taken
71        from the 1000-entry workspace that had been reserved. So now there is no
72        explicit limit, but more stack is used.
73    
74     8. Applied Daniel's patches to solve problems with the import/export magic
75        syntax that is required for Windows, and which was going wrong for the
76        pcreposix and pcrecpp parts of the library. These were overlooked when this
77        problem was solved for the main library.
78    
79     9. There were some crude static tests to avoid integer overflow when computing
80        the size of patterns that contain repeated groups with explicit upper
81        limits. As the maximum quantifier is 65535, the maximum group length was
82        set at 30,000 so that the product of these two numbers did not overflow a
83        32-bit integer. However, it turns out that people want to use groups that
84        are longer than 30,000 bytes (though not repeat them that many times).
85        Change 7.0/17 (the refactoring of the way the pattern size is computed) has
86        made it possible to implement the integer overflow checks in a much more
87        dynamic way, which I have now done. The artificial limitation on group
88        length has been removed - we now have only the limit on the total length of
89        the compiled pattern, which depends on the LINK_SIZE setting.
90    
91    10. Fixed a bug in the documentation for get/copy named substring when
92        duplicate names are permitted. If none of the named substrings are set, the
93        functions return PCRE_ERROR_NOSUBSTRING (7); the doc said they returned an
94        empty string.
95    
96    11. Because Perl interprets \Q...\E at a high level, and ignores orphan \E
97        instances, patterns such as [\Q\E] or [\E] or even [^\E] cause an error,
98        because the ] is interpreted as the first data character and the
99        terminating ] is not found. PCRE has been made compatible with Perl in this
100        regard. Previously, it interpreted [\Q\E] as an empty class, and [\E] could
101        cause memory overwriting.
102    
103    10. Like Perl, PCRE automatically breaks an unlimited repeat after an empty
104        string has been matched (to stop an infinite loop). It was not recognizing
105        a conditional subpattern that could match an empty string if that
106        subpattern was within another subpattern. For example, it looped when
107        trying to match  (((?(1)X|))*)  but it was OK with  ((?(1)X|)*)  where the
108        condition was not nested. This bug has been fixed.
109    
110    12. A pattern like \X?\d or \P{L}?\d in non-UTF-8 mode could cause a backtrack
111        past the start of the subject in the presence of bytes with the top bit
112        set, for example "\x8aBCD".
113    
114    13. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
115        (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
116    
117    14. Optimized (?!) to (*FAIL).
118    
119    15. Updated the test for a valid UTF-8 string to conform to the later RFC 3629.
120        This restricts code points to be within the range 0 to 0x10FFFF, excluding
121        the "low surrogate" sequence 0xD800 to 0xDFFF. Previously, PCRE allowed the
122        full range 0 to 0x7FFFFFFF, as defined by RFC 2279. Internally, it still
123        does: it's just the validity check that is more restrictive.
124    
125    16. Inserted checks for integer overflows during escape sequence (backslash)
126        processing, and also fixed erroneous offset values for syntax errors during
127        backslash processing.
128    
129    17. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
130        for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
131    
132    18. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
133        caused an overrun.
134    
135    19. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
136        something other than just ASCII characters) inside a group that had an
137        unlimited repeat caused a loop at compile time (while checking to see
138        whether the group could match an empty string).
139    
140    20. Debugging a pattern containing \p or \P could cause a crash. For example,
141        [\P{Any}] did so. (Error in the code for printing property names.)
142    
143    21. An orphan \E inside a character class could cause a crash.
144    
145    22. A repeated capturing bracket such as (A)? could cause a wild memory
146        reference during compilation.
147    
148    23. There are several functions in pcre_compile() that scan along a compiled
149        expression for various reasons (e.g. to see if it's fixed length for look
150        behind). There were bugs in these functions when a repeated \p or \P was
151        present in the pattern. These operators have additional parameters compared
152        with \d, etc, and these were not being taken into account when moving along
153        the compiled data. Specifically:
154    
155        (a) A item such as \p{Yi}{3} in a lookbehind was not treated as fixed
156            length.
157    
158        (b) An item such as \pL+ within a repeated group could cause crashes or
159            loops.
160    
161        (c) A pattern such as \p{Yi}+(\P{Yi}+)(?1) could give an incorrect
162            "reference to non-existent subpattern" error.
163    
164        (d) A pattern like (\P{Yi}{2}\277)? could loop at compile time.
165    
166    24. A repeated \S or \W in UTF-8 mode could give wrong answers when multibyte
167        characters were involved (for example /\S{2}/8g with "A\x{a3}BC").
168    
169    25. Using pcregrep in multiline, inverted mode (-Mv) caused it to loop.
170    
171    26. Patterns such as [\P{Yi}A] which include \p or \P and just one other
172        character were causing crashes (broken optimization).
173    
174    27. Patterns such as (\P{Yi}*\277)* (group with possible zero repeat containing
175        \p or \P) caused a compile-time loop.
176    
177    28. More problems have arisen in unanchored patterns when CRLF is a valid line
178        break. For example, the unstudied pattern [\r\n]A does not match the string
179        "\r\nA" because change 7.0/46 below moves the current point on by two
180        characters after failing to match at the start. However, the pattern \nA
181        *does* match, because it doesn't start till \n, and if [\r\n]A is studied,
182        the same is true. There doesn't seem any very clean way out of this, but
183        what I have chosen to do makes the common cases work: PCRE now takes note
184        of whether there can be an explicit match for \r or \n anywhere in the
185        pattern, and if so, 7.0/46 no longer applies. As part of this change,
186        there's a new PCRE_INFO_HASCRORLF option for finding out whether a compiled
187        pattern has explicit CR or LF references.
188    
189    29. Added (*CR) etc for changing newline setting at start of pattern.
190    
191    
192    Version 7.2 19-Jun-07
193    ---------------------
194    
195     1. If the fr_FR locale cannot be found for test 3, try the "french" locale,
196        which is apparently normally available under Windows.
197    
198     2. Re-jig the pcregrep tests with different newline settings in an attempt
199        to make them independent of the local environment's newline setting.
200    
201     3. Add code to configure.ac to remove -g from the CFLAGS default settings.
202    
203     4. Some of the "internals" tests were previously cut out when the link size
204        was not 2, because the output contained actual offsets. The recent new
205        "Z" feature of pcretest means that these can be cut out, making the tests
206        usable with all link sizes.
207    
208     5. Implemented Stan Switzer's goto replacement for longjmp() when not using
209        stack recursion. This gives a massive performance boost under BSD, but just
210        a small improvement under Linux. However, it saves one field in the frame
211        in all cases.
212    
213     6. Added more features from the forthcoming Perl 5.10:
214    
215        (a) (?-n) (where n is a string of digits) is a relative subroutine or
216            recursion call. It refers to the nth most recently opened parentheses.
217    
218        (b) (?+n) is also a relative subroutine call; it refers to the nth next
219            to be opened parentheses.
220    
221        (c) Conditions that refer to capturing parentheses can be specified
222            relatively, for example, (?(-2)... or (?(+3)...
223    
224        (d) \K resets the start of the current match so that everything before
225            is not part of it.
226    
227        (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
228    
229        (f) \g{name} is another synonym - part of Perl 5.10's unification of
230            reference syntax.
231    
232        (g) (?| introduces a group in which the numbering of parentheses in each
233            alternative starts with the same number.
234    
235        (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
236    
237     7. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
238        PCRE_INFO_JCHANGED.
239    
240     8. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
241        terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
242        for detecting groups that can match an empty string.
243    
244     9. A pattern with a very large number of alternatives (more than several
245        hundred) was running out of internal workspace during the pre-compile
246        phase, where pcre_compile() figures out how much memory will be needed. A
247        bit of new cunning has reduced the workspace needed for groups with
248        alternatives. The 1000-alternative test pattern now uses 12 bytes of
249        workspace instead of running out of the 4096 that are available.
250    
251    10. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
252    
253    11. Applied patch from Google to remove an optimization that didn't quite work.
254        The report of the bug said:
255    
256          pcrecpp::RE("a*").FullMatch("aaa") matches, while
257          pcrecpp::RE("a*?").FullMatch("aaa") does not, and
258          pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
259    
260    12. If \p or \P was used in non-UTF-8 mode on a character greater than 127
261        it matched the wrong number of bytes.
262    
263    
264    Version 7.1 24-Apr-07
265    ---------------------
266    
267     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
268        that is more "standard", making use of automake and other Autotools. There
269        is some re-arrangement of the files and adjustment of comments consequent
270        on this.
271    
272     2. Part of the patch fixed a problem with the pcregrep tests. The test of -r
273        for recursive directory scanning broke on some systems because the files
274        are not scanned in any specific order and on different systems the order
275        was different. A call to "sort" has been inserted into RunGrepTest for the
276        approprate test as a short-term fix. In the longer term there may be an
277        alternative.
278    
279     3. I had an email from Eric Raymond about problems translating some of PCRE's
280        man pages to HTML (despite the fact that I distribute HTML pages, some
281        people do their own conversions for various reasons). The problems
282        concerned the use of low-level troff macros .br and .in. I have therefore
283        removed all such uses from the man pages (some were redundant, some could
284        be replaced by .nf/.fi pairs). The 132html script that I use to generate
285        HTML has been updated to handle .nf/.fi and to complain if it encounters
286        .br or .in.
287    
288     4. Updated comments in configure.ac that get placed in config.h.in and also
289        arranged for config.h to be included in the distribution, with the name
290        config.h.generic, for the benefit of those who have to compile without
291        Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
292    
293     5. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
294        Weber: (1) pcre_internal.h was missing some function renames; (2) updated
295        makevp.bat for the current PCRE, using the additional files
296        makevp_c.txt, makevp_l.txt, and pcregexp.pas.
297    
298     6. A Windows user reported a minor discrepancy with test 2, which turned out
299        to be caused by a trailing space on an input line that had got lost in his
300        copy. The trailing space was an accident, so I've just removed it.
301    
302     7. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
303        that is needed.
304    
305     8. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
306        as "const" (a) because they are and (b) because it helps the PHP
307        maintainers who have recently made a script to detect big data structures
308        in the php code that should be moved to the .rodata section. I remembered
309        to update Builducptable as well, so it won't revert if ucptable.h is ever
310        re-created.
311    
312     9. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
313        pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
314        order to be able to cut out the UTF-8 tables in the latter when UTF-8
315        support is not required. This saves 1.5-2K of code, which is important in
316        some applications.
317    
318        Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
319        so as not to refer to the tables, even though these functions will never be
320        called when UTF-8 support is disabled. Otherwise there are problems with a
321        shared library.
322    
323    10. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
324    
325        (a) It was defining its arguments as char * instead of void *.
326    
327        (b) It was assuming that all moves were upwards in memory; this was true
328            a long time ago when I wrote it, but is no longer the case.
329    
330        The emulated memove() is provided for those environments that have neither
331        memmove() nor bcopy(). I didn't think anyone used it these days, but that
332        is clearly not the case, as these two bugs were recently reported.
333    
334    11. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
335        and Detrail to create the HTML documentation, the .txt form of the man
336        pages, and it removes trailing spaces from listed files. It also creates
337        pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
338        case, it wraps all the #defines with #ifndefs. This script should be run
339        before "make dist".
340    
341    12. Fixed two fairly obscure bugs concerned with quantified caseless matching
342        with Unicode property support.
343    
344        (a) For a maximizing quantifier, if the two different cases of the
345            character were of different lengths in their UTF-8 codings (there are
346            some cases like this - I found 11), and the matching function had to
347            back up over a mixture of the two cases, it incorrectly assumed they
348            were both the same length.
349    
350        (b) When PCRE was configured to use the heap rather than the stack for
351            recursion during matching, it was not correctly preserving the data for
352            the other case of a UTF-8 character when checking ahead for a match
353            while processing a minimizing repeat. If the check also involved
354            matching a wide character, but failed, corruption could cause an
355            erroneous result when trying to check for a repeat of the original
356            character.
357    
358    13. Some tidying changes to the testing mechanism:
359    
360        (a) The RunTest script now detects the internal link size and whether there
361            is UTF-8 and UCP support by running ./pcretest -C instead of relying on
362            values substituted by "configure". (The RunGrepTest script already did
363            this for UTF-8.) The configure.ac script no longer substitutes the
364            relevant variables.
365    
366        (b) The debugging options /B and /D in pcretest show the compiled bytecode
367            with length and offset values. This means that the output is different
368            for different internal link sizes. Test 2 is skipped for link sizes
369            other than 2 because of this, bypassing the problem. Unfortunately,
370            there was also a test in test 3 (the locale tests) that used /B and
371            failed for link sizes other than 2. Rather than cut the whole test out,
372            I have added a new /Z option to pcretest that replaces the length and
373            offset values with spaces. This is now used to make test 3 independent
374            of link size. (Test 2 will be tidied up later.)
375    
376    14. If erroroffset was passed as NULL to pcre_compile, it provoked a
377        segmentation fault instead of returning the appropriate error message.
378    
379    15. In multiline mode when the newline sequence was set to "any", the pattern
380        ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
381        This doesn't seem right; it now treats the CRLF combination as the line
382        ending, and so does not match in that case. It's only a pattern such as ^$
383        that would hit this one: something like ^ABC$ would have failed after \r
384        and then tried again after \r\n.
385    
386    16. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
387        in an attempt to make files that differ only in their line terminators
388        compare equal. This works on Linux.
389    
390    17. Under certain error circumstances pcregrep might try to free random memory
391        as it exited. This is now fixed, thanks to valgrind.
392    
393    19. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
394        "abc\r\n\r\n", it found an unwanted second match after the second \r. This
395        was because its rules for how to advance for /g after matching an empty
396        string at the end of a line did not allow for this case. They now check for
397        it specially.
398    
399    20. pcretest is supposed to handle patterns and data of any length, by
400        extending its buffers when necessary. It was getting this wrong when the
401        buffer for a data line had to be extended.
402    
403    21. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
404        CRLF as a newline sequence.
405    
406    22. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
407        out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
408        I have nevertheless tidied it up.
409    
410    23. Added some casts to kill warnings from HP-UX ia64 compiler.
411    
412    24. Added a man page for pcre-config.
413    
414    
415    Version 7.0 19-Dec-06
416    ---------------------
417    
418     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
419        moving to gcc 4.1.1.
420    
421     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
422        sys/time.h, which is documented as needed for this function. It doesn't
423        seem to matter on Linux, but it showed up on some releases of OS X.
424    
425     3. It seems that there are systems where bytes whose values are greater than
426        127 match isprint() in the "C" locale. The "C" locale should be the
427        default when a C program starts up. In most systems, only ASCII printing
428        characters match isprint(). This difference caused the output from pcretest
429        to vary, making some of the tests fail. I have changed pcretest so that:
430    
431        (a) When it is outputting text in the compiled version of a pattern, bytes
432            other than 32-126 are always shown as hex escapes.
433    
434        (b) When it is outputting text that is a matched part of a subject string,
435            it does the same, unless a different locale has been set for the match
436            (using the /L modifier). In this case, it uses isprint() to decide.
437    
438     4. Fixed a major bug that caused incorrect computation of the amount of memory
439        required for a compiled pattern when options that changed within the
440        pattern affected the logic of the preliminary scan that determines the
441        length. The relevant options are -x, and -i in UTF-8 mode. The result was
442        that the computed length was too small. The symptoms of this bug were
443        either the PCRE error "internal error: code overflow" from pcre_compile(),
444        or a glibc crash with a message such as "pcretest: free(): invalid next
445        size (fast)". Examples of patterns that provoked this bug (shown in
446        pcretest format) are:
447    
448          /(?-x: )/x
449          /(?x)(?-x: \s*#\s*)/
450          /((?i)[\x{c0}])/8
451          /(?i:[\x{c0}])/8
452    
453        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
454        is now done differently.
455    
456     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
457        wrapper classes; (b) implement a new function in the C++ scanner that is
458        more efficient than the old way of doing things because it avoids levels of
459        recursion in the regex matching; (c) add a paragraph to the documentation
460        for the FullMatch() function.
461    
462     6. The escape sequence \n was being treated as whatever was defined as
463        "newline". Not only was this contrary to the documentation, which states
464        that \n is character 10 (hex 0A), but it also went horribly wrong when
465        "newline" was defined as CRLF. This has been fixed.
466    
467     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
468        was being set to -1 for the "end of line" case (supposedly a value that no
469        character can have). Though this value is never used (the check for end of
470        line is "zero bytes in current character"), it caused compiler complaints.
471        I've changed it to 0xffffffff.
472    
473     8. In pcre_version.c, the version string was being built by a sequence of
474        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
475        string (as it is for production releases) called a macro with an empty
476        argument. The C standard says the result of this is undefined. The gcc
477        compiler treats it as an empty string (which was what was wanted) but it is
478        reported that Visual C gives an error. The source has been hacked around to
479        avoid this problem.
480    
481     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
482        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
483        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
484        of them did).
485    
486    10. Originally, pcretest opened its input and output without "b"; then I was
487        told that "b" was needed in some environments, so it was added for release
488        5.0 to both the input and output. (It makes no difference on Unix-like
489        systems.) Later I was told that it is wrong for the input on Windows. I've
490        now abstracted the modes into two macros, to make it easier to fiddle with
491        them, and removed "b" from the input mode under Windows.
492    
493    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
494    
495    12. Added -help and --help to pcretest as an official way of being reminded
496        of the options.
497    
498    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
499        and pcrecpp.cc because they annoy compilers at high warning levels.
500    
501    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
502    
503    15. Fixed an occurrence of == in configure.ac that should have been = (shell
504        scripts are not C programs :-) and which was not noticed because it works
505        on Linux.
506    
507    16. pcretest is supposed to handle any length of pattern and data line (as one
508        line or as a continued sequence of lines) by extending its input buffer if
509        necessary. This feature was broken for very long pattern lines, leading to
510        a string of junk being passed to pcre_compile() if the pattern was longer
511        than about 50K.
512    
513    17. I have done a major re-factoring of the way pcre_compile() computes the
514        amount of memory needed for a compiled pattern. Previously, there was code
515        that made a preliminary scan of the pattern in order to do this. That was
516        OK when PCRE was new, but as the facilities have expanded, it has become
517        harder and harder to keep it in step with the real compile phase, and there
518        have been a number of bugs (see for example, 4 above). I have now found a
519        cunning way of running the real compile function in a "fake" mode that
520        enables it to compute how much memory it would need, while actually only
521        ever using a few hundred bytes of working memory and without too many
522        tests of the mode. This should make future maintenance and development
523        easier. A side effect of this work is that the limit of 200 on the nesting
524        depth of parentheses has been removed (though this was never a serious
525        limitation, I suspect). However, there is a downside: pcre_compile() now
526        runs more slowly than before (30% or more, depending on the pattern). I
527        hope this isn't a big issue. There is no effect on runtime performance.
528    
529    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
530        newline (only possible for the last line of a file) and it was a
531        pattern that set a locale (followed by /Lsomething), pcretest crashed.
532    
533    19. Added additional timing features to pcretest. (1) The -tm option now times
534        matching only, not compiling. (2) Both -t and -tm can be followed, as a
535        separate command line item, by a number that specifies the number of
536        repeats to use when timing. The default is 50000; this gives better
537        precision, but takes uncomfortably long for very large patterns.
538    
539    20. Extended pcre_study() to be more clever in cases where a branch of a
540        subpattern has no definite first character. For example, (a*|b*)[cd] would
541        previously give no result from pcre_study(). Now it recognizes that the
542        first character must be a, b, c, or d.
543    
544    21. There was an incorrect error "recursive call could loop indefinitely" if
545        a subpattern (or the entire pattern) that was being tested for matching an
546        empty string contained only one non-empty item after a nested subpattern.
547        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
548        incorrectly, because the \d was being skipped in the check.
549    
550    22. The pcretest program now has a new pattern option /B and a command line
551        option -b, which is equivalent to adding /B to every pattern. This causes
552        it to show the compiled bytecode, without the additional information that
553        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
554        is the same as /B/I).
555    
556    23. A new optimization is now able automatically to treat some sequences such
557        as a*b as a*+b. More specifically, if something simple (such as a character
558        or a simple class like \d) has an unlimited quantifier, and is followed by
559        something that cannot possibly match the quantified thing, the quantifier
560        is automatically "possessified".
561    
562    24. A recursive reference to a subpattern whose number was greater than 39
563        went wrong under certain circumstances in UTF-8 mode. This bug could also
564        have affected the operation of pcre_study().
565    
566    25. Realized that a little bit of performance could be had by replacing
567        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
568    
569    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
570    
571    27. Possessive quantifiers such as a++ were previously implemented by turning
572        them into atomic groups such as ($>a+). Now they have their own opcodes,
573        which improves performance. This includes the automatically created ones
574        from 23 above.
575    
576    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
577        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
578        the first matched character to be a colon. This applied both to named and
579        numbered groups.
580    
581    29. The ucpinternal.h header file was missing its idempotency #ifdef.
582    
583    30. I was sent a "project" file called libpcre.a.dev which I understand makes
584        building PCRE on Windows easier, so I have included it in the distribution.
585    
586    31. There is now a check in pcretest against a ridiculously large number being
587        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
588        loop, the loop is abandoned.
589    
590    32. Forward references to subpatterns in conditions such as (?(2)...) where
591        subpattern 2 is defined later cause pcre_compile() to search forwards in
592        the pattern for the relevant set of parentheses. This search went wrong
593        when there were unescaped parentheses in a character class, parentheses
594        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
595    
596    33. "Subroutine" calls and backreferences were previously restricted to
597        referencing subpatterns earlier in the regex. This restriction has now
598        been removed.
599    
600    34. Added a number of extra features that are going to be in Perl 5.10. On the
601        whole, these are just syntactic alternatives for features that PCRE had
602        previously implemented using the Python syntax or my own invention. The
603        other formats are all retained for compatibility.
604    
605        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
606            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
607            also .NET compatible.
608    
609        (b) A recursion or subroutine call to a named group can now be defined as
610            (?&name) as well as (?P>name).
611    
612        (c) A backreference to a named group can now be defined as \k<name> or
613            \k'name' as well as (?P=name). The new forms, as well as being in Perl
614            5.10, are also .NET compatible.
615    
616        (d) A conditional reference to a named group can now use the syntax
617            (?(<name>) or (?('name') as well as (?(name).
618    
619        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
620            groups (named and numbered) that are never evaluated inline, but can be
621            called as "subroutines" from elsewhere. In effect, the DEFINE condition
622            is always false. There may be only one alternative in such a group.
623    
624        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
625            as the simple (?(R). The condition is true only if the most recent
626            recursion is that of the given number or name. It does not search out
627            through the entire recursion stack.
628    
629        (g) The escape \gN or \g{N} has been added, where N is a positive or
630            negative number, specifying an absolute or relative reference.
631    
632    35. Tidied to get rid of some further signed/unsigned compiler warnings and
633        some "unreachable code" warnings.
634    
635    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
636        things, this adds five new scripts.
637    
638    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
639        There were also incompatibilities regarding the handling of \Q..\E inside
640        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
641        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
642    
643    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
644        matches an empty string, and forcibly breaks the loop. There were bugs in
645        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
646        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
647        separate and independent bugs (that affected different cases) have been
648        fixed.
649    
650    39. Refactored the code to abolish the use of different opcodes for small
651        capturing bracket numbers. This is a tidy that I avoided doing when I
652        removed the limit on the number of capturing brackets for 3.5 back in 2001.
653        The new approach is not only tidier, it makes it possible to reduce the
654        memory needed to fix the previous bug (38).
655    
656    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
657        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
658        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
659        mode.
660    
661    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
662        report.
663    
664    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
665        copy construction and assignment in the C++ wrapper.
666    
667    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
668        couple of bugs that could have given wrong results in the "--newline=crlf"
669        case.
670    
671    44. Added a number of casts and did some reorganization of signed/unsigned int
672        variables following suggestions from Dair Grant. Also renamed the variable
673        "this" as "item" because it is a C++ keyword.
674    
675    45. Arranged for dftables to add
676    
677          #include "pcre_internal.h"
678    
679        to pcre_chartables.c because without it, gcc 4.x may remove the array
680        definition from the final binary if PCRE is built into a static library and
681        dead code stripping is activated.
682    
683    46. For an unanchored pattern, if a match attempt fails at the start of a
684        newline sequence, and the newline setting is CRLF or ANY, and the next two
685        characters are CRLF, advance by two characters instead of one.
686    
687    
688    Version 6.7 04-Jul-06
689    ---------------------
690    
691     1. In order to handle tests when input lines are enormously long, pcretest has
692        been re-factored so that it automatically extends its buffers when
693        necessary. The code is crude, but this _is_ just a test program. The
694        default size has been increased from 32K to 50K.
695    
696     2. The code in pcre_study() was using the value of the re argument before
697        testing it for NULL. (Of course, in any sensible call of the function, it
698        won't be NULL.)
699    
700     3. The memmove() emulation function in pcre_internal.h, which is used on
701        systems that lack both memmove() and bcopy() - that is, hardly ever -
702        was missing a "static" storage class specifier.
703    
704     4. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
705        containing an extended class (one that cannot be represented by a bitmap
706        because it contains high-valued characters or Unicode property items, e.g.
707        [\pZ]). Almost always one would set UTF-8 mode when processing such a
708        pattern, but PCRE should not loop if you do not (it no longer does).
709        [Detail: two cases were found: (a) a repeated subpattern containing an
710        extended class; (b) a recursive reference to a subpattern that followed a
711        previous extended class. It wasn't skipping over the extended class
712        correctly when UTF-8 mode was not set.]
713    
714     5. A negated single-character class was not being recognized as fixed-length
715        in lookbehind assertions such as (?<=[^f]), leading to an incorrect
716        compile error "lookbehind assertion is not fixed length".
717    
718     6. The RunPerlTest auxiliary script was showing an unexpected difference
719        between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
720        write a Perl script that can interpret lines of an input file either as
721        byte characters or as UTF-8, which is what "perltest" was being required to
722        do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
723        can't do is switch easily at run time between having the "use utf8;" pragma
724        or not. In the end, I fudged it by using the RunPerlTest script to insert
725        "use utf8;" explicitly for the UTF-8 tests.
726    
727     7. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
728        the end of the subject string, contrary to the documentation and to what
729        Perl does. This was true of both matching functions. Now it matches only at
730        the start of the subject and immediately after *internal* newlines.
731    
732     8. A call of pcre_fullinfo() from pcretest to get the option bits was passing
733        a pointer to an int instead of a pointer to an unsigned long int. This
734        caused problems on 64-bit systems.
735    
736     9. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
737        instance of the 'standard' template library not being so standard".
738    
739    10. There was no check on the number of named subpatterns nor the maximum
740        length of a subpattern name. The product of these values is used to compute
741        the size of the memory block for a compiled pattern. By supplying a very
742        long subpattern name and a large number of named subpatterns, the size
743        computation could be caused to overflow. This is now prevented by limiting
744        the length of names to 32 characters, and the number of named subpatterns
745        to 10,000.
746    
747    11. Subpatterns that are repeated with specific counts have to be replicated in
748        the compiled pattern. The size of memory for this was computed from the
749        length of the subpattern and the repeat count. The latter is limited to
750        65535, but there was no limit on the former, meaning that integer overflow
751        could in principle occur. The compiled length of a repeated subpattern is
752        now limited to 30,000 bytes in order to prevent this.
753    
754    12. Added the optional facility to have named substrings with the same name.
755    
756    13. Added the ability to use a named substring as a condition, using the
757        Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
758        are numbers (not recommended). Forward references are permitted.
759    
760    14. Added forward references in named backreferences (if you see what I mean).
761    
762    15. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
763        pattern could run off the end of the subject. For example, the pattern
764        "(?s)(.{1,5})"8 did this with the subject "ab".
765    
766    16. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
767        PCRE_CASELESS was set when matching characters that were quantified with ?
768        or *.
769    
770    17. A character class other than a single negated character that had a minimum
771        but no maximum quantifier - for example [ab]{6,} - was not handled
772        correctly by pce_dfa_exec(). It would match only one character.
773    
774    18. A valid (though odd) pattern that looked like a POSIX character
775        class but used an invalid character after [ (for example [[,abc,]]) caused
776        pcre_compile() to give the error "Failed: internal error: code overflow" or
777        in some cases to crash with a glibc free() error. This could even happen if
778        the pattern terminated after [[ but there just happened to be a sequence of
779        letters, a binary zero, and a closing ] in the memory that followed.
780    
781    19. Perl's treatment of octal escapes in the range \400 to \777 has changed
782        over the years. Originally (before any Unicode support), just the bottom 8
783        bits were taken. Thus, for example, \500 really meant \100. Nowadays the
784        output from "man perlunicode" includes this:
785    
786          The regular expression compiler produces polymorphic opcodes.  That
787          is, the pattern adapts to the data and automatically switches to
788          the Unicode character scheme when presented with Unicode data--or
789          instead uses a traditional byte scheme when presented with byte
790          data.
791    
792        Sadly, a wide octal escape does not cause a switch, and in a string with
793        no other multibyte characters, these octal escapes are treated as before.
794        Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
795        /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
796        Unicode string.
797    
798        I have not perpetrated such confusion in PCRE. Up till now, it took just
799        the bottom 8 bits, as in old Perl. I have now made octal escapes with
800        values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
801        translate to the appropriate multibyte character.
802    
803    29. Applied some refactoring to reduce the number of warnings from Microsoft
804        and Borland compilers. This has included removing the fudge introduced
805        seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
806        a warning about an unused variable.
807    
808    21. PCRE has not included VT (character 0x0b) in the set of whitespace
809        characters since release 4.0, because Perl (from release 5.004) does not.
810        [Or at least, is documented not to: some releases seem to be in conflict
811        with the documentation.] However, when a pattern was studied with
812        pcre_study() and all its branches started with \s, PCRE still included VT
813        as a possible starting character. Of course, this did no harm; it just
814        caused an unnecessary match attempt.
815    
816    22. Removed a now-redundant internal flag bit that recorded the fact that case
817        dependency changed within the pattern. This was once needed for "required
818        byte" processing, but is no longer used. This recovers a now-scarce options
819        bit. Also moved the least significant internal flag bit to the most-
820        significant bit of the word, which was not previously used (hangover from
821        the days when it was an int rather than a uint) to free up another bit for
822        the future.
823    
824    23. Added support for CRLF line endings as well as CR and LF. As well as the
825        default being selectable at build time, it can now be changed at runtime
826        via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
827        specify that it is scanning data with non-default line endings.
828    
829    24. Changed the definition of CXXLINK to make it agree with the definition of
830        LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
831    
832    25. Applied Ian Taylor's patches to avoid using another stack frame for tail
833        recursions. This makes a big different to stack usage for some patterns.
834    
835    26. If a subpattern containing a named recursion or subroutine reference such
836        as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
837        the space required for the compiled pattern went wrong and gave too small a
838        value. Depending on the environment, this could lead to "Failed: internal
839        error: code overflow at offset 49" or "glibc detected double free or
840        corruption" errors.
841    
842    27. Applied patches from Google (a) to support the new newline modes and (b) to
843        advance over multibyte UTF-8 characters in GlobalReplace.
844    
845    28. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
846        difference for some implementation of PCRE in some Windows version.
847    
848    29. Added some extra testing facilities to pcretest:
849    
850        \q<number>   in a data line sets the "match limit" value
851        \Q<number>   in a data line sets the "match recursion limt" value
852        -S <number>  sets the stack size, where <number> is in megabytes
853    
854        The -S option isn't available for Windows.
855    
856    
857    Version 6.6 06-Feb-06
858    ---------------------
859    
860     1. Change 16(a) for 6.5 broke things, because PCRE_DATA_SCOPE was not defined
861        in pcreposix.h. I have copied the definition from pcre.h.
862    
863     2. Change 25 for 6.5 broke compilation in a build directory out-of-tree
864        because pcre.h is no longer a built file.
865    
866     3. Added Jeff Friedl's additional debugging patches to pcregrep. These are
867        not normally included in the compiled code.
868    
869    
870    Version 6.5 01-Feb-06
871    ---------------------
872    
873     1. When using the partial match feature with pcre_dfa_exec(), it was not
874        anchoring the second and subsequent partial matches at the new starting
875        point. This could lead to incorrect results. For example, with the pattern
876        /1234/, partially matching against "123" and then "a4" gave a match.
877    
878     2. Changes to pcregrep:
879    
880        (a) All non-match returns from pcre_exec() were being treated as failures
881            to match the line. Now, unless the error is PCRE_ERROR_NOMATCH, an
882            error message is output. Some extra information is given for the
883            PCRE_ERROR_MATCHLIMIT and PCRE_ERROR_RECURSIONLIMIT errors, which are
884            probably the only errors that are likely to be caused by users (by
885            specifying a regex that has nested indefinite repeats, for instance).
886            If there are more than 20 of these errors, pcregrep is abandoned.
887    
888        (b) A binary zero was treated as data while matching, but terminated the
889            output line if it was written out. This has been fixed: binary zeroes
890            are now no different to any other data bytes.
891    
892        (c) Whichever of the LC_ALL or LC_CTYPE environment variables is set is
893            used to set a locale for matching. The --locale=xxxx long option has
894            been added (no short equivalent) to specify a locale explicitly on the
895            pcregrep command, overriding the environment variables.
896    
897        (d) When -B was used with -n, some line numbers in the output were one less
898            than they should have been.
899    
900        (e) Added the -o (--only-matching) option.
901    
902        (f) If -A or -C was used with -c (count only), some lines of context were
903            accidentally printed for the final match.
904    
905        (g) Added the -H (--with-filename) option.
906    
907        (h) The combination of options -rh failed to suppress file names for files
908            that were found from directory arguments.
909    
910        (i) Added the -D (--devices) and -d (--directories) options.
911    
912        (j) Added the -F (--fixed-strings) option.
913    
914        (k) Allow "-" to be used as a file name for -f as well as for a data file.
915    
916        (l) Added the --colo(u)r option.
917    
918        (m) Added Jeffrey Friedl's -S testing option, but within #ifdefs so that it
919            is not present by default.
920    
921     3. A nasty bug was discovered in the handling of recursive patterns, that is,
922        items such as (?R) or (?1), when the recursion could match a number of
923        alternatives. If it matched one of the alternatives, but subsequently,
924        outside the recursion, there was a failure, the code tried to back up into
925        the recursion. However, because of the way PCRE is implemented, this is not
926        possible, and the result was an incorrect result from the match.
927    
928        In order to prevent this happening, the specification of recursion has
929        been changed so that all such subpatterns are automatically treated as
930        atomic groups. Thus, for example, (?R) is treated as if it were (?>(?R)).
931    
932     4. I had overlooked the fact that, in some locales, there are characters for
933        which isalpha() is true but neither isupper() nor islower() are true. In
934        the fr_FR locale, for instance, the \xAA and \xBA characters (ordmasculine
935        and ordfeminine) are like this. This affected the treatment of \w and \W
936        when they appeared in character classes, but not when they appeared outside
937        a character class. The bit map for "word" characters is now created
938        separately from the results of isalnum() instead of just taking it from the
939        upper, lower, and digit maps. (Plus the underscore character, of course.)
940    
941     5. The above bug also affected the handling of POSIX character classes such as
942        [[:alpha:]] and [[:alnum:]]. These do not have their own bit maps in PCRE's
943        permanent tables. Instead, the bit maps for such a class were previously
944        created as the appropriate unions of the upper, lower, and digit bitmaps.
945        Now they are created by subtraction from the [[:word:]] class, which has
946        its own bitmap.
947    
948     6. The [[:blank:]] character class matches horizontal, but not vertical space.
949        It is created by subtracting the vertical space characters (\x09, \x0a,
950        \x0b, \x0c) from the [[:space:]] bitmap. Previously, however, the
951        subtraction was done in the overall bitmap for a character class, meaning
952        that a class such as [\x0c[:blank:]] was incorrect because \x0c would not
953        be recognized. This bug has been fixed.
954    
955     7. Patches from the folks at Google:
956    
957          (a) pcrecpp.cc: "to handle a corner case that may or may not happen in
958          real life, but is still worth protecting against".
959    
960          (b) pcrecpp.cc: "corrects a bug when negative radixes are used with
961          regular expressions".
962    
963          (c) pcre_scanner.cc: avoid use of std::count() because not all systems
964          have it.
965    
966          (d) Split off pcrecpparg.h from pcrecpp.h and had the former built by
967          "configure" and the latter not, in order to fix a problem somebody had
968          with compiling the Arg class on HP-UX.
969    
970          (e) Improve the error-handling of the C++ wrapper a little bit.
971    
972          (f) New tests for checking recursion limiting.
973    
974     8. The pcre_memmove() function, which is used only if the environment does not
975        have a standard memmove() function (and is therefore rarely compiled),
976        contained two bugs: (a) use of int instead of size_t, and (b) it was not
977        returning a result (though PCRE never actually uses the result).
978    
979     9. In the POSIX regexec() interface, if nmatch is specified as a ridiculously
980        large number - greater than INT_MAX/(3*sizeof(int)) - REG_ESPACE is
981        returned instead of calling malloc() with an overflowing number that would
982        most likely cause subsequent chaos.
983    
984    10. The debugging option of pcretest was not showing the NO_AUTO_CAPTURE flag.
985    
986    11. The POSIX flag REG_NOSUB is now supported. When a pattern that was compiled
987        with this option is matched, the nmatch and pmatch options of regexec() are
988        ignored.
989    
990    12. Added REG_UTF8 to the POSIX interface. This is not defined by POSIX, but is
991        provided in case anyone wants to the the POSIX interface with UTF-8
992        strings.
993    
994    13. Added CXXLDFLAGS to the Makefile parameters to provide settings only on the
995        C++ linking (needed for some HP-UX environments).
996    
997    14. Avoid compiler warnings in get_ucpname() when compiled without UCP support
998        (unused parameter) and in the pcre_printint() function (omitted "default"
999        switch label when the default is to do nothing).
1000    
1001    15. Added some code to make it possible, when PCRE is compiled as a C++
1002        library, to replace subject pointers for pcre_exec() with a smart pointer
1003        class, thus making it possible to process discontinuous strings.
1004    
1005    16. The two macros PCRE_EXPORT and PCRE_DATA_SCOPE are confusing, and perform
1006        much the same function. They were added by different people who were trying
1007        to make PCRE easy to compile on non-Unix systems. It has been suggested
1008        that PCRE_EXPORT be abolished now that there is more automatic apparatus
1009        for compiling on Windows systems. I have therefore replaced it with
1010        PCRE_DATA_SCOPE. This is set automatically for Windows; if not set it
1011        defaults to "extern" for C or "extern C" for C++, which works fine on
1012        Unix-like systems. It is now possible to override the value of PCRE_DATA_
1013        SCOPE with something explicit in config.h. In addition:
1014    
1015        (a) pcreposix.h still had just "extern" instead of either of these macros;
1016            I have replaced it with PCRE_DATA_SCOPE.
1017    
1018        (b) Functions such as _pcre_xclass(), which are internal to the library,
1019            but external in the C sense, all had PCRE_EXPORT in their definitions.
1020            This is apparently wrong for the Windows case, so I have removed it.
1021            (It makes no difference on Unix-like systems.)
1022    
1023    17. Added a new limit, MATCH_LIMIT_RECURSION, which limits the depth of nesting
1024        of recursive calls to match(). This is different to MATCH_LIMIT because
1025        that limits the total number of calls to match(), not all of which increase
1026        the depth of recursion. Limiting the recursion depth limits the amount of
1027        stack (or heap if NO_RECURSE is set) that is used. The default can be set
1028        when PCRE is compiled, and changed at run time. A patch from Google adds
1029        this functionality to the C++ interface.
1030    
1031    18. Changes to the handling of Unicode character properties:
1032    
1033        (a) Updated the table to Unicode 4.1.0.
1034    
1035        (b) Recognize characters that are not in the table as "Cn" (undefined).
1036    
1037        (c) I revised the way the table is implemented to a much improved format
1038            which includes recognition of ranges. It now supports the ranges that
1039            are defined in UnicodeData.txt, and it also amalgamates other
1040            characters into ranges. This has reduced the number of entries in the
1041            table from around 16,000 to around 3,000, thus reducing its size
1042            considerably. I realized I did not need to use a tree structure after
1043            all - a binary chop search is just as efficient. Having reduced the
1044            number of entries, I extended their size from 6 bytes to 8 bytes to
1045            allow for more data.
1046    
1047        (d) Added support for Unicode script names via properties such as \p{Han}.
1048    
1049    19. In UTF-8 mode, a backslash followed by a non-Ascii character was not
1050        matching that character.
1051    
1052    20. When matching a repeated Unicode property with a minimum greater than zero,
1053        (for example \pL{2,}), PCRE could look past the end of the subject if it
1054        reached it while seeking the minimum number of characters. This could
1055        happen only if some of the characters were more than one byte long, because
1056        there is a check for at least the minimum number of bytes.
1057    
1058    21. Refactored the implementation of \p and \P so as to be more general, to
1059        allow for more different types of property in future. This has changed the
1060        compiled form incompatibly. Anybody with saved compiled patterns that use
1061        \p or \P will have to recompile them.
1062    
1063    22. Added "Any" and "L&" to the supported property types.
1064    
1065    23. Recognize \x{...} as a code point specifier, even when not in UTF-8 mode,
1066        but give a compile time error if the value is greater than 0xff.
1067    
1068    24. The man pages for pcrepartial, pcreprecompile, and pcre_compile2 were
1069        accidentally not being installed or uninstalled.
1070    
1071    25. The pcre.h file was built from pcre.h.in, but the only changes that were
1072        made were to insert the current release number. This seemed silly, because
1073        it made things harder for people building PCRE on systems that don't run
1074        "configure". I have turned pcre.h into a distributed file, no longer built
1075        by "configure", with the version identification directly included. There is
1076        no longer a pcre.h.in file.
1077    
1078        However, this change necessitated a change to the pcre-config script as
1079        well. It is built from pcre-config.in, and one of the substitutions was the
1080        release number. I have updated configure.ac so that ./configure now finds
1081        the release number by grepping pcre.h.
1082    
1083    26. Added the ability to run the tests under valgrind.
1084    
1085    
1086    Version 6.4 05-Sep-05
1087    ---------------------
1088    
1089     1. Change 6.0/10/(l) to pcregrep introduced a bug that caused separator lines
1090        "--" to be printed when multiple files were scanned, even when none of the
1091        -A, -B, or -C options were used. This is not compatible with Gnu grep, so I
1092        consider it to be a bug, and have restored the previous behaviour.
1093    
1094     2. A couple of code tidies to get rid of compiler warnings.
1095    
1096     3. The pcretest program used to cheat by referring to symbols in the library
1097        whose names begin with _pcre_. These are internal symbols that are not
1098        really supposed to be visible externally, and in some environments it is
1099        possible to suppress them. The cheating is now confined to including
1100        certain files from the library's source, which is a bit cleaner.
1101    
1102     4. Renamed pcre.in as pcre.h.in to go with pcrecpp.h.in; it also makes the
1103        file's purpose clearer.
1104    
1105     5. Reorganized pcre_ucp_findchar().
1106    
1107    
1108    Version 6.3 15-Aug-05
1109    ---------------------
1110    
1111     1. The file libpcre.pc.in did not have general read permission in the tarball.
1112    
1113     2. There were some problems when building without C++ support:
1114    
1115        (a) If C++ support was not built, "make install" and "make test" still
1116            tried to test it.
1117    
1118        (b) There were problems when the value of CXX was explicitly set. Some
1119            changes have been made to try to fix these, and ...
1120    
1121        (c) --disable-cpp can now be used to explicitly disable C++ support.
1122    
1123        (d) The use of @CPP_OBJ@ directly caused a blank line preceded by a
1124            backslash in a target when C++ was disabled. This confuses some
1125            versions of "make", apparently. Using an intermediate variable solves
1126            this. (Same for CPP_LOBJ.)
1127    
1128     3. $(LINK_FOR_BUILD) now includes $(CFLAGS_FOR_BUILD) and $(LINK)
1129        (non-Windows) now includes $(CFLAGS) because these flags are sometimes
1130        necessary on certain architectures.
1131    
1132     4. Added a setting of -export-symbols-regex to the link command to remove
1133        those symbols that are exported in the C sense, but actually are local
1134        within the library, and not documented. Their names all begin with
1135        "_pcre_". This is not a perfect job, because (a) we have to except some
1136        symbols that pcretest ("illegally") uses, and (b) the facility isn't always
1137        available (and never for static libraries). I have made a note to try to
1138        find a way round (a) in the future.
1139    
1140    
1141    Version 6.2 01-Aug-05
1142    ---------------------
1143    
1144     1. There was no test for integer overflow of quantifier values. A construction
1145        such as {1111111111111111} would give undefined results. What is worse, if
1146        a minimum quantifier for a parenthesized subpattern overflowed and became
1147        negative, the calculation of the memory size went wrong. This could have
1148        led to memory overwriting.
1149    
1150     2. Building PCRE using VPATH was broken. Hopefully it is now fixed.
1151    
1152     3. Added "b" to the 2nd argument of fopen() in dftables.c, for non-Unix-like
1153        operating environments where this matters.
1154    
1155     4. Applied Giuseppe Maxia's patch to add additional features for controlling
1156        PCRE options from within the C++ wrapper.
1157    
1158     5. Named capturing subpatterns were not being correctly counted when a pattern
1159        was compiled. This caused two problems: (a) If there were more than 100
1160        such subpatterns, the calculation of the memory needed for the whole
1161        compiled pattern went wrong, leading to an overflow error. (b) Numerical
1162        back references of the form \12, where the number was greater than 9, were
1163        not recognized as back references, even though there were sufficient
1164        previous subpatterns.
1165    
1166     6. Two minor patches to pcrecpp.cc in order to allow it to compile on older
1167        versions of gcc, e.g. 2.95.4.
1168    
1169    
1170    Version 6.1 21-Jun-05
1171    ---------------------
1172    
1173     1. There was one reference to the variable "posix" in pcretest.c that was not
1174        surrounded by "#if !defined NOPOSIX".
1175    
1176     2. Make it possible to compile pcretest without DFA support, UTF8 support, or
1177        the cross-check on the old pcre_info() function, for the benefit of the
1178        cut-down version of PCRE that is currently imported into Exim.
1179    
1180     3. A (silly) pattern starting with (?i)(?-i) caused an internal space
1181        allocation error. I've done the easy fix, which wastes 2 bytes for sensible
1182        patterns that start (?i) but I don't think that matters. The use of (?i) is
1183        just an example; this all applies to the other options as well.
1184    
1185     4. Since libtool seems to echo the compile commands it is issuing, the output
1186        from "make" can be reduced a bit by putting "@" in front of each libtool
1187        compile command.
1188    
1189     5. Patch from the folks at Google for configure.in to be a bit more thorough
1190        in checking for a suitable C++ installation before trying to compile the
1191        C++ stuff. This should fix a reported problem when a compiler was present,
1192        but no suitable headers.
1193    
1194     6. The man pages all had just "PCRE" as their title. I have changed them to
1195        be the relevant file name. I have also arranged that these names are
1196        retained in the file doc/pcre.txt, which is a concatenation in text format
1197        of all the man pages except the little individual ones for each function.
1198    
1199     7. The NON-UNIX-USE file had not been updated for the different set of source
1200        files that come with release 6. I also added a few comments about the C++
1201        wrapper.
1202    
1203    
1204    Version 6.0 07-Jun-05
1205    ---------------------
1206    
1207     1. Some minor internal re-organization to help with my DFA experiments.
1208    
1209     2. Some missing #ifdef SUPPORT_UCP conditionals in pcretest and printint that
1210        didn't matter for the library itself when fully configured, but did matter
1211        when compiling without UCP support, or within Exim, where the ucp files are
1212        not imported.
1213    
1214     3. Refactoring of the library code to split up the various functions into
1215        different source modules. The addition of the new DFA matching code (see
1216        below) to a single monolithic source would have made it really too
1217        unwieldy, quite apart from causing all the code to be include in a
1218        statically linked application, when only some functions are used. This is
1219        relevant even without the DFA addition now that patterns can be compiled in
1220        one application and matched in another.
1221    
1222        The downside of splitting up is that there have to be some external
1223        functions and data tables that are used internally in different modules of
1224        the library but which are not part of the API. These have all had their
1225        names changed to start with "_pcre_" so that they are unlikely to clash
1226        with other external names.
1227    
1228     4. Added an alternate matching function, pcre_dfa_exec(), which matches using
1229        a different (DFA) algorithm. Although it is slower than the original
1230        function, it does have some advantages for certain types of matching
1231        problem.
1232    
1233     5. Upgrades to pcretest in order to test the features of pcre_dfa_exec(),
1234        including restarting after a partial match.
1235    
1236     6. A patch for pcregrep that defines INVALID_FILE_ATTRIBUTES if it is not
1237        defined when compiling for Windows was sent to me. I have put it into the
1238        code, though I have no means of testing or verifying it.
1239    
1240     7. Added the pcre_refcount() auxiliary function.
1241    
1242     8. Added the PCRE_FIRSTLINE option. This constrains an unanchored pattern to
1243        match before or at the first newline in the subject string. In pcretest,
1244        the /f option on a pattern can be used to set this.
1245    
1246     9. A repeated \w when used in UTF-8 mode with characters greater than 256
1247        would behave wrongly. This has been present in PCRE since release 4.0.
1248    
1249    10. A number of changes to the pcregrep command:
1250    
1251        (a) Refactored how -x works; insert ^(...)$ instead of setting
1252            PCRE_ANCHORED and checking the length, in preparation for adding
1253            something similar for -w.
1254    
1255        (b) Added the -w (match as a word) option.
1256    
1257        (c) Refactored the way lines are read and buffered so as to have more
1258            than one at a time available.
1259    
1260        (d) Implemented a pcregrep test script.
1261    
1262        (e) Added the -M (multiline match) option. This allows patterns to match
1263            over several lines of the subject. The buffering ensures that at least
1264            8K, or the rest of the document (whichever is the shorter) is available
1265            for matching (and similarly the previous 8K for lookbehind assertions).
1266    
1267        (f) Changed the --help output so that it now says
1268    
1269              -w, --word-regex(p)
1270    
1271            instead of two lines, one with "regex" and the other with "regexp"
1272            because that confused at least one person since the short forms are the
1273            same. (This required a bit of code, as the output is generated
1274            automatically from a table. It wasn't just a text change.)
1275    
1276        (g) -- can be used to terminate pcregrep options if the next thing isn't an
1277            option but starts with a hyphen. Could be a pattern or a path name
1278            starting with a hyphen, for instance.
1279    
1280        (h) "-" can be given as a file name to represent stdin.
1281    
1282        (i) When file names are being printed, "(standard input)" is used for
1283            the standard input, for compatibility with GNU grep. Previously
1284            "<stdin>" was used.
1285    
1286        (j) The option --label=xxx can be used to supply a name to be used for
1287            stdin when file names are being printed. There is no short form.
1288    
1289        (k) Re-factored the options decoding logic because we are going to add
1290            two more options that take data. Such options can now be given in four
1291            different ways, e.g. "-fname", "-f name", "--file=name", "--file name".
1292    
1293        (l) Added the -A, -B, and -C options for requesting that lines of context
1294            around matches be printed.
1295    
1296        (m) Added the -L option to print the names of files that do not contain
1297            any matching lines, that is, the complement of -l.
1298    
1299        (n) The return code is 2 if any file cannot be opened, but pcregrep does
1300            continue to scan other files.
1301    
1302        (o) The -s option was incorrectly implemented. For compatibility with other
1303            greps, it now suppresses the error message for a non-existent or non-
1304            accessible file (but not the return code). There is a new option called
1305            -q that suppresses the output of matching lines, which was what -s was
1306            previously doing.
1307    
1308        (p) Added --include and --exclude options to specify files for inclusion
1309            and exclusion when recursing.
1310    
1311    11. The Makefile was not using the Autoconf-supported LDFLAGS macro properly.
1312        Hopefully, it now does.
1313    
1314    12. Missing cast in pcre_study().
1315    
1316    13. Added an "uninstall" target to the makefile.
1317    
1318    14. Replaced "extern" in the function prototypes in Makefile.in with
1319        "PCRE_DATA_SCOPE", which defaults to 'extern' or 'extern "C"' in the Unix
1320        world, but is set differently for Windows.
1321    
1322    15. Added a second compiling function called pcre_compile2(). The only
1323        difference is that it has an extra argument, which is a pointer to an
1324        integer error code. When there is a compile-time failure, this is set
1325        non-zero, in addition to the error test pointer being set to point to an
1326        error message. The new argument may be NULL if no error number is required
1327        (but then you may as well call pcre_compile(), which is now just a
1328        wrapper). This facility is provided because some applications need a
1329        numeric error indication, but it has also enabled me to tidy up the way
1330        compile-time errors are handled in the POSIX wrapper.
1331    
1332    16. Added VPATH=.libs to the makefile; this should help when building with one
1333        prefix path and installing with another. (Or so I'm told by someone who
1334        knows more about this stuff than I do.)
1335    
1336    17. Added a new option, REG_DOTALL, to the POSIX function regcomp(). This
1337        passes PCRE_DOTALL to the pcre_compile() function, making the "." character
1338        match everything, including newlines. This is not POSIX-compatible, but
1339        somebody wanted the feature. From pcretest it can be activated by using
1340        both the P and the s flags.
1341    
1342    18. AC_PROG_LIBTOOL appeared twice in Makefile.in. Removed one.
1343    
1344    19. libpcre.pc was being incorrectly installed as executable.
1345    
1346    20. A couple of places in pcretest check for end-of-line by looking for '\n';
1347        it now also looks for '\r' so that it will work unmodified on Windows.
1348    
1349    21. Added Google's contributed C++ wrapper to the distribution.
1350    
1351    22. Added some untidy missing memory free() calls in pcretest, to keep
1352        Electric Fence happy when testing.
1353    
1354    
1355    
1356    Version 5.0 13-Sep-04
1357    ---------------------
1358    
1359     1. Internal change: literal characters are no longer packed up into items
1360        containing multiple characters in a single byte-string. Each character
1361        is now matched using a separate opcode. However, there may be more than one
1362        byte in the character in UTF-8 mode.
1363    
1364     2. The pcre_callout_block structure has two new fields: pattern_position and
1365        next_item_length. These contain the offset in the pattern to the next match
1366        item, and its length, respectively.
1367    
1368     3. The PCRE_AUTO_CALLOUT option for pcre_compile() requests the automatic
1369        insertion of callouts before each pattern item. Added the /C option to
1370        pcretest to make use of this.
1371    
1372     4. On the advice of a Windows user, the lines
1373    
1374          #if defined(_WIN32) || defined(WIN32)
1375          _setmode( _fileno( stdout ), 0x8000 );
1376          #endif  /* defined(_WIN32) || defined(WIN32) */
1377    
1378        have been added to the source of pcretest. This apparently does useful
1379        magic in relation to line terminators.
1380    
1381     5. Changed "r" and "w" in the calls to fopen() in pcretest to "rb" and "wb"
1382        for the benefit of those environments where the "b" makes a difference.
1383    
1384     6. The icc compiler has the same options as gcc, but "configure" doesn't seem
1385        to know about it. I have put a hack into configure.in that adds in code
1386        to set GCC=yes if CC=icc. This seems to end up at a point in the
1387        generated configure script that is early enough to affect the setting of
1388        compiler options, which is what is needed, but I have no means of testing
1389        whether it really works. (The user who reported this had patched the
1390        generated configure script, which of course I cannot do.)
1391    
1392        LATER: After change 22 below (new libtool files), the configure script
1393        seems to know about icc (and also ecc). Therefore, I have commented out
1394        this hack in configure.in.
1395    
1396     7. Added support for pkg-config (2 patches were sent in).
1397    
1398     8. Negated POSIX character classes that used a combination of internal tables
1399        were completely broken. These were [[:^alpha:]], [[:^alnum:]], and
1400        [[:^ascii]]. Typically, they would match almost any characters. The other
1401        POSIX classes were not broken in this way.
1402    
1403     9. Matching the pattern "\b.*?" against "ab cd", starting at offset 1, failed
1404        to find the match, as PCRE was deluded into thinking that the match had to
1405        start at the start point or following a newline. The same bug applied to
1406        patterns with negative forward assertions or any backward assertions
1407        preceding ".*" at the start, unless the pattern required a fixed first
1408        character. This was a failing pattern: "(?!.bcd).*". The bug is now fixed.
1409    
1410    10. In UTF-8 mode, when moving forwards in the subject after a failed match
1411        starting at the last subject character, bytes beyond the end of the subject
1412        string were read.
1413    
1414    11. Renamed the variable "class" as "classbits" to make life easier for C++
1415        users. (Previously there was a macro definition, but it apparently wasn't
1416        enough.)
1417    
1418    12. Added the new field "tables" to the extra data so that tables can be passed
1419        in at exec time, or the internal tables can be re-selected. This allows
1420        a compiled regex to be saved and re-used at a later time by a different
1421        program that might have everything at different addresses.
1422    
1423    13. Modified the pcre-config script so that, when run on Solaris, it shows a
1424        -R library as well as a -L library.
1425    
1426    14. The debugging options of pcretest (-d on the command line or D on a
1427        pattern) showed incorrect output for anything following an extended class
1428        that contained multibyte characters and which was followed by a quantifier.
1429    
1430    15. Added optional support for general category Unicode character properties
1431        via the \p, \P, and \X escapes. Unicode property support implies UTF-8
1432        support. It adds about 90K to the size of the library. The meanings of the
1433        inbuilt class escapes such as \d and \s have NOT been changed.
1434    
1435    16. Updated pcredemo.c to include calls to free() to release the memory for the
1436        compiled pattern.
1437    
1438    17. The generated file chartables.c was being created in the source directory
1439        instead of in the building directory. This caused the build to fail if the
1440        source directory was different from the building directory, and was
1441        read-only.
1442    
1443    18. Added some sample Win commands from Mark Tetrode into the NON-UNIX-USE
1444        file. No doubt somebody will tell me if they don't make sense... Also added
1445        Dan Mooney's comments about building on OpenVMS.
1446    
1447    19. Added support for partial matching via the PCRE_PARTIAL option for
1448        pcre_exec() and the \P data escape in pcretest.
1449    
1450    20. Extended pcretest with 3 new pattern features:
1451    
1452        (i)   A pattern option of the form ">rest-of-line" causes pcretest to
1453              write the compiled pattern to the file whose name is "rest-of-line".
1454              This is a straight binary dump of the data, with the saved pointer to
1455              the character tables forced to be NULL. The study data, if any, is
1456              written too. After writing, pcretest reads a new pattern.
1457    
1458        (ii)  If, instead of a pattern, "<rest-of-line" is given, pcretest reads a
1459              compiled pattern from the given file. There must not be any
1460              occurrences of "<" in the file name (pretty unlikely); if there are,
1461              pcretest will instead treat the initial "<" as a pattern delimiter.
1462              After reading in the pattern, pcretest goes on to read data lines as
1463              usual.
1464    
1465        (iii) The F pattern option causes pcretest to flip the bytes in the 32-bit
1466              and 16-bit fields in a compiled pattern, to simulate a pattern that
1467              was compiled on a host of opposite endianness.
1468    
1469    21. The pcre-exec() function can now cope with patterns that were compiled on
1470        hosts of opposite endianness, with this restriction:
1471    
1472          As for any compiled expression that is saved and used later, the tables
1473          pointer field cannot be preserved; the extra_data field in the arguments
1474          to pcre_exec() should be used to pass in a tables address if a value
1475          other than the default internal tables were used at compile time.
1476    
1477    22. Calling pcre_exec() with a negative value of the "ovecsize" parameter is
1478        now diagnosed as an error. Previously, most of the time, a negative number
1479        would have been treated as zero, but if in addition "ovector" was passed as
1480        NULL, a crash could occur.
1481    
1482    23. Updated the files ltmain.sh, config.sub, config.guess, and aclocal.m4 with
1483        new versions from the libtool 1.5 distribution (the last one is a copy of
1484        a file called libtool.m4). This seems to have fixed the need to patch
1485        "configure" to support Darwin 1.3 (which I used to do). However, I still
1486        had to patch ltmain.sh to ensure that ${SED} is set (it isn't on my
1487        workstation).
1488    
1489    24. Changed the PCRE licence to be the more standard "BSD" licence.
1490    
1491    
1492    Version 4.5 01-Dec-03
1493    ---------------------
1494    
1495     1. There has been some re-arrangement of the code for the match() function so
1496        that it can be compiled in a version that does not call itself recursively.
1497        Instead, it keeps those local variables that need separate instances for
1498        each "recursion" in a frame on the heap, and gets/frees frames whenever it
1499        needs to "recurse". Keeping track of where control must go is done by means
1500        of setjmp/longjmp. The whole thing is implemented by a set of macros that
1501        hide most of the details from the main code, and operates only if
1502        NO_RECURSE is defined while compiling pcre.c. If PCRE is built using the
1503        "configure" mechanism, "--disable-stack-for-recursion" turns on this way of
1504        operating.
1505    
1506        To make it easier for callers to provide specially tailored get/free
1507        functions for this usage, two new functions, pcre_stack_malloc, and
1508        pcre_stack_free, are used. They are always called in strict stacking order,
1509        and the size of block requested is always the same.
1510    
1511        The PCRE_CONFIG_STACKRECURSE info parameter can be used to find out whether
1512        PCRE has been compiled to use the stack or the heap for recursion. The
1513        -C option of pcretest uses this to show which version is compiled.
1514    
1515        A new data escape \S, is added to pcretest; it causes the amounts of store
1516        obtained and freed by both kinds of malloc/free at match time to be added
1517        to the output.
1518    
1519     2. Changed the locale test to use "fr_FR" instead of "fr" because that's
1520        what's available on my current Linux desktop machine.
1521    
1522     3. When matching a UTF-8 string, the test for a valid string at the start has
1523        been extended. If start_offset is not zero, PCRE now checks that it points
1524        to a byte that is the start of a UTF-8 character. If not, it returns
1525        PCRE_ERROR_BADUTF8_OFFSET (-11). Note: the whole string is still checked;
1526        this is necessary because there may be backward assertions in the pattern.
1527        When matching the same subject several times, it may save resources to use
1528        PCRE_NO_UTF8_CHECK on all but the first call if the string is long.
1529    
1530     4. The code for checking the validity of UTF-8 strings has been tightened so
1531        that it rejects (a) strings containing 0xfe or 0xff bytes and (b) strings
1532        containing "overlong sequences".
1533    
1534     5. Fixed a bug (appearing twice) that I could not find any way of exploiting!
1535        I had written "if ((digitab[*p++] && chtab_digit) == 0)" where the "&&"
1536        should have been "&", but it just so happened that all the cases this let
1537        through by mistake were picked up later in the function.
1538    
1539     6. I had used a variable called "isblank" - this is a C99 function, causing
1540        some compilers to warn. To avoid this, I renamed it (as "blankclass").
1541    
1542     7. Cosmetic: (a) only output another newline at the end of pcretest if it is
1543        prompting; (b) run "./pcretest /dev/null" at the start of the test script
1544        so the version is shown; (c) stop "make test" echoing "./RunTest".
1545    
1546     8. Added patches from David Burgess to enable PCRE to run on EBCDIC systems.
1547    
1548     9. The prototype for memmove() for systems that don't have it was using
1549        size_t, but the inclusion of the header that defines size_t was later. I've
1550        moved the #includes for the C headers earlier to avoid this.
1551    
1552    10. Added some adjustments to the code to make it easier to compiler on certain
1553        special systems:
1554    
1555          (a) Some "const" qualifiers were missing.
1556          (b) Added the macro EXPORT before all exported functions; by default this
1557              is defined to be empty.
1558          (c) Changed the dftables auxiliary program (that builds chartables.c) so
1559              that it reads its output file name as an argument instead of writing
1560              to the standard output and assuming this can be redirected.
1561    
1562    11. In UTF-8 mode, if a recursive reference (e.g. (?1)) followed a character
1563        class containing characters with values greater than 255, PCRE compilation
1564        went into a loop.
1565    
1566    12. A recursive reference to a subpattern that was within another subpattern
1567        that had a minimum quantifier of zero caused PCRE to crash. For example,
1568        (x(y(?2))z)? provoked this bug with a subject that got as far as the
1569        recursion. If the recursively-called subpattern itself had a zero repeat,
1570        that was OK.
1571    
1572    13. In pcretest, the buffer for reading a data line was set at 30K, but the
1573        buffer into which it was copied (for escape processing) was still set at
1574        1024, so long lines caused crashes.
1575    
1576    14. A pattern such as /[ab]{1,3}+/ failed to compile, giving the error
1577        "internal error: code overflow...". This applied to any character class
1578        that was followed by a possessive quantifier.
1579    
1580    15. Modified the Makefile to add libpcre.la as a prerequisite for
1581        libpcreposix.la because I was told this is needed for a parallel build to
1582        work.
1583    
1584    16. If a pattern that contained .* following optional items at the start was
1585        studied, the wrong optimizing data was generated, leading to matching
1586        errors. For example, studying /[ab]*.*c/ concluded, erroneously, that any
1587        matching string must start with a or b or c. The correct conclusion for
1588        this pattern is that a match can start with any character.
1589    
1590    
1591  Version 4.4 13-Aug-03  Version 4.4 13-Aug-03
1592  ---------------------  ---------------------
1593    

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