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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4  Version 8.00 ??-???-??  Version 8.10 03 May-2010
5    ------------------------
6    
7    1.  Added support for (*MARK:ARG) and for ARG additions to PRUNE, SKIP, and
8        THEN.
9    
10    2.  (*ACCEPT) was not working when inside an atomic group.
11    
12    3.  Inside a character class, \B is treated as a literal by default, but
13        faulted if PCRE_EXTRA is set. This mimics Perl's behaviour (the -w option
14        causes the error). The code is unchanged, but I tidied the documentation.
15    
16    4.  Inside a character class, PCRE always treated \R and \X as literals,
17        whereas Perl faults them if its -w option is set. I have changed PCRE so
18        that it faults them when PCRE_EXTRA is set.
19    
20    5.  Added support for \N, which always matches any character other than
21        newline. (It is the same as "." when PCRE_DOTALL is not set.)
22    
23    6.  When compiling pcregrep with newer versions of gcc which may have
24        FORTIFY_SOURCE set, several warnings "ignoring return value of 'fwrite',
25        declared with attribute warn_unused_result" were given. Just casting the
26        result to (void) does not stop the warnings; a more elaborate fudge is
27        needed. I've used a macro to implement this.
28    
29    7.  Minor change to pcretest.c to avoid a compiler warning.
30    
31    8.  Added four artifical Unicode properties to help with an option to make
32        \s etc use properties (see next item). The new properties are: Xan
33        (alphanumeric), Xsp (Perl space), Xps (POSIX space), and Xwd (word).
34    
35    9.  Added PCRE_UCP to make \b, \d, \s, \w, and certain POSIX character classes
36        use Unicode properties. (*UCP) at the start of a pattern can be used to set
37        this option. Modified pcretest to add /W to test this facility. Added
38        REG_UCP to make it available via the POSIX interface.
39    
40    10. Added --line-buffered to pcregrep.
41    
42    11. In UTF-8 mode, if a pattern that was compiled with PCRE_CASELESS was
43        studied, and the match started with a letter with a code point greater than
44        127 whose first byte was different to the first byte of the other case of
45        the letter, the other case of this starting letter was not recognized.
46    
47    12. pcreposix.c included pcre.h before including pcre_internal.h. This caused a
48        conflict in the definition of PCRE_EXP_DECL. I have removed the include of
49        pcre.h as pcre_internal.h includes pcre.h itself. (This may be a bit of
50        historical tidying that never got done.)
51    
52    13. If a pattern that was studied started with a repeated Unicode property
53        test, for example, \p{Nd}+, there was the theoretical possibility of
54        setting up an incorrect bitmap of starting bytes, but fortunately it could
55        not have actually happened in practice until change 8 above was made (it
56        added property types that matched character-matching opcodes).
57    
58    
59    
60    Version 8.02 19-Mar-2010
61    ------------------------
62    
63    1.  The Unicode data tables have been updated to Unicode 5.2.0.
64    
65    2.  Added the option --libs-cpp to pcre-config, but only when C++ support is
66        configured.
67    
68    3.  Updated the licensing terms in the pcregexp.pas file, as agreed with the
69        original author of that file, following a query about its status.
70    
71    4.  On systems that do not have stdint.h (e.g. Solaris), check for and include
72        inttypes.h instead. This fixes a bug that was introduced by change 8.01/8.
73    
74    5.  A pattern such as (?&t)*+(?(DEFINE)(?<t>.)) which has a possessive
75        quantifier applied to a forward-referencing subroutine call, could compile
76        incorrect code or give the error "internal error: previously-checked
77        referenced subpattern not found".
78    
79    6.  Both MS Visual Studio and Symbian OS have problems with initializing
80        variables to point to external functions. For these systems, therefore,
81        pcre_malloc etc. are now initialized to local functions that call the
82        relevant global functions.
83    
84    7.  There were two entries missing in the vectors called coptable and poptable
85        in pcre_dfa_exec.c. This could lead to memory accesses outsize the vectors.
86        I've fixed the data, and added a kludgy way of testing at compile time that
87        the lengths are correct (equal to the number of opcodes).
88    
89    8.  Following on from 7, I added a similar kludge to check the length of the
90        eint vector in pcreposix.c.
91    
92    9.  Error texts for pcre_compile() are held as one long string to avoid too
93        much relocation at load time. To find a text, the string is searched,
94        counting zeros. There was no check for running off the end of the string,
95        which could happen if a new error number was added without updating the
96        string.
97    
98    10. \K gave a compile-time error if it appeared in a lookbehind assersion.
99    
100    11. \K was not working if it appeared in an atomic group or in a group that
101        was called as a "subroutine", or in an assertion. Perl 5.11 documents that
102        \K is "not well defined" if used in an assertion. PCRE now accepts it if
103        the assertion is positive, but not if it is negative.
104    
105    12. Change 11 fortuitously reduced the size of the stack frame used in the
106        "match()" function of pcre_exec.c by one pointer. Forthcoming
107        implementation of support for (*MARK) will need an extra pointer on the
108        stack; I have reserved it now, so that the stack frame size does not
109        decrease.
110    
111    13. A pattern such as (?P<L1>(?P<L2>0)|(?P>L2)(?P>L1)) in which the only other
112        item in branch that calls a recursion is a subroutine call - as in the
113        second branch in the above example - was incorrectly given the compile-
114        time error "recursive call could loop indefinitely" because pcre_compile()
115        was not correctly checking the subroutine for matching a non-empty string.
116    
117    14. The checks for overrunning compiling workspace could trigger after an
118        overrun had occurred. This is a "should never occur" error, but it can be
119        triggered by pathological patterns such as hundreds of nested parentheses.
120        The checks now trigger 100 bytes before the end of the workspace.
121    
122    15. Fix typo in configure.ac: "srtoq" should be "strtoq".
123    
124    
125    Version 8.01 19-Jan-2010
126    ------------------------
127    
128    1.  If a pattern contained a conditional subpattern with only one branch (in
129        particular, this includes all (*DEFINE) patterns), a call to pcre_study()
130        computed the wrong minimum data length (which is of course zero for such
131        subpatterns). This could cause incorrect "no match" results.
132    
133    2.  For patterns such as (?i)a(?-i)b|c where an option setting at the start of
134        the pattern is reset in the first branch, pcre_compile() failed with
135        "internal error: code overflow at offset...". This happened only when
136        the reset was to the original external option setting. (An optimization
137        abstracts leading options settings into an external setting, which was the
138        cause of this.)
139    
140    3.  A pattern such as ^(?!a(*SKIP)b) where a negative assertion contained one
141        of the verbs SKIP, PRUNE, or COMMIT, did not work correctly. When the
142        assertion pattern did not match (meaning that the assertion was true), it
143        was incorrectly treated as false if the SKIP had been reached during the
144        matching. This also applied to assertions used as conditions.
145    
146    4.  If an item that is not supported by pcre_dfa_exec() was encountered in an
147        assertion subpattern, including such a pattern used as a condition,
148        unpredictable results occurred, instead of the error return
149        PCRE_ERROR_DFA_UITEM.
150    
151    5.  The C++ GlobalReplace function was not working like Perl for the special
152        situation when an empty string is matched. It now does the fancy magic
153        stuff that is necessary.
154    
155    6.  In pcre_internal.h, obsolete includes to setjmp.h and stdarg.h have been
156        removed. (These were left over from very, very early versions of PCRE.)
157    
158    7.  Some cosmetic changes to the code to make life easier when compiling it
159        as part of something else:
160    
161        (a) Change DEBUG to PCRE_DEBUG.
162    
163        (b) In pcre_compile(), rename the member of the "branch_chain" structure
164            called "current" as "current_branch", to prevent a collision with the
165            Linux macro when compiled as a kernel module.
166    
167        (c) In pcre_study(), rename the function set_bit() as set_table_bit(), to
168            prevent a collision with the Linux macro when compiled as a kernel
169            module.
170    
171    8.  In pcre_compile() there are some checks for integer overflows that used to
172        cast potentially large values to (double). This has been changed to that
173        when building, a check for int64_t is made, and if it is found, it is used
174        instead, thus avoiding the use of floating point arithmetic. (There is no
175        other use of FP in PCRE.) If int64_t is not found, the fallback is to
176        double.
177    
178    9.  Added two casts to avoid signed/unsigned warnings from VS Studio Express
179        2005 (difference between two addresses compared to an unsigned value).
180    
181    10. Change the standard AC_CHECK_LIB test for libbz2 in configure.ac to a
182        custom one, because of the following reported problem in Windows:
183    
184          - libbz2 uses the Pascal calling convention (WINAPI) for the functions
185              under Win32.
186          - The standard autoconf AC_CHECK_LIB fails to include "bzlib.h",
187              therefore missing the function definition.
188          - The compiler thus generates a "C" signature for the test function.
189          - The linker fails to find the "C" function.
190          - PCRE fails to configure if asked to do so against libbz2.
191    
192    11. When running libtoolize from libtool-2.2.6b as part of autogen.sh, these
193        messages were output:
194    
195          Consider adding `AC_CONFIG_MACRO_DIR([m4])' to configure.ac and
196          rerunning libtoolize, to keep the correct libtool macros in-tree.
197          Consider adding `-I m4' to ACLOCAL_AMFLAGS in Makefile.am.
198    
199        I have done both of these things.
200    
201    12. Although pcre_dfa_exec() does not use nearly as much stack as pcre_exec()
202        most of the time, it *can* run out if it is given a pattern that contains a
203        runaway infinite recursion. I updated the discussion in the pcrestack man
204        page.
205    
206    13. Now that we have gone to the x.xx style of version numbers, the minor
207        version may start with zero. Using 08 or 09 is a bad idea because users
208        might check the value of PCRE_MINOR in their code, and 08 or 09 may be
209        interpreted as invalid octal numbers. I've updated the previous comment in
210        configure.ac, and also added a check that gives an error if 08 or 09 are
211        used.
212    
213    14. Change 8.00/11 was not quite complete: code had been accidentally omitted,
214        causing partial matching to fail when the end of the subject matched \W
215        in a UTF-8 pattern where \W was quantified with a minimum of 3.
216    
217    15. There were some discrepancies between the declarations in pcre_internal.h
218        of _pcre_is_newline(), _pcre_was_newline(), and _pcre_valid_utf8() and
219        their definitions. The declarations used "const uschar *" and the
220        definitions used USPTR. Even though USPTR is normally defined as "const
221        unsigned char *" (and uschar is typedeffed as "unsigned char"), it was
222        reported that: "This difference in casting confuses some C++ compilers, for
223        example, SunCC recognizes above declarations as different functions and
224        generates broken code for hbpcre." I have changed the declarations to use
225        USPTR.
226    
227    16. GNU libtool is named differently on some systems. The autogen.sh script now
228        tries several variants such as glibtoolize (MacOSX) and libtoolize1x
229        (FreeBSD).
230    
231    17. Applied Craig's patch that fixes an HP aCC compile error in pcre 8.00
232        (strtoXX undefined when compiling pcrecpp.cc). The patch contains this
233        comment: "Figure out how to create a longlong from a string: strtoll and
234        equivalent. It's not enough to call AC_CHECK_FUNCS: hpux has a strtoll, for
235        instance, but it only takes 2 args instead of 3!"
236    
237    18. A subtle bug concerned with back references has been fixed by a change of
238        specification, with a corresponding code fix. A pattern such as
239        ^(xa|=?\1a)+$ which contains a back reference inside the group to which it
240        refers, was giving matches when it shouldn't. For example, xa=xaaa would
241        match that pattern. Interestingly, Perl (at least up to 5.11.3) has the
242        same bug. Such groups have to be quantified to be useful, or contained
243        inside another quantified group. (If there's no repetition, the reference
244        can never match.) The problem arises because, having left the group and
245        moved on to the rest of the pattern, a later failure that backtracks into
246        the group uses the captured value from the final iteration of the group
247        rather than the correct earlier one. I have fixed this in PCRE by forcing
248        any group that contains a reference to itself to be an atomic group; that
249        is, there cannot be any backtracking into it once it has completed. This is
250        similar to recursive and subroutine calls.
251    
252    
253    Version 8.00 19-Oct-09
254  ----------------------  ----------------------
255    
256  1.  The table for translating pcre_compile() error codes into POSIX error codes  1.  The table for translating pcre_compile() error codes into POSIX error codes
257      was out-of-date, and there was no check on the pcre_compile() error code      was out-of-date, and there was no check on the pcre_compile() error code
258      being within the table. This could lead to an OK return being given in      being within the table. This could lead to an OK return being given in
259      error.      error.
260    
261  2.  Changed the call to open a subject file in pcregrep from fopen(pathname,  2.  Changed the call to open a subject file in pcregrep from fopen(pathname,
262      "r") to fopen(pathname, "rb"), which fixed a problem with some of the tests      "r") to fopen(pathname, "rb"), which fixed a problem with some of the tests
263      in a Windows environment.      in a Windows environment.
264    
265  3.  The pcregrep --count option prints the count for each file even when it is  3.  The pcregrep --count option prints the count for each file even when it is
266      zero, as does GNU grep. However, pcregrep was also printing all files when      zero, as does GNU grep. However, pcregrep was also printing all files when
267      --files-with-matches was added. Now, when both options are given, it prints      --files-with-matches was added. Now, when both options are given, it prints
268      counts only for those files that have at least one match. (GNU grep just      counts only for those files that have at least one match. (GNU grep just
269      prints the file name in this circumstance, but including the count seems      prints the file name in this circumstance, but including the count seems
270      more useful - otherwise, why use --count?) Also ensured that the      more useful - otherwise, why use --count?) Also ensured that the
271      combination -clh just lists non-zero counts, with no names.      combination -clh just lists non-zero counts, with no names.
272    
273  4.  The long form of the pcregrep -F option was incorrectly implemented as  4.  The long form of the pcregrep -F option was incorrectly implemented as
274      --fixed_strings instead of --fixed-strings. This is an incompatible change,      --fixed_strings instead of --fixed-strings. This is an incompatible change,
275      but it seems right to fix it, and I didn't think it was worth preserving      but it seems right to fix it, and I didn't think it was worth preserving
276      the old behaviour.      the old behaviour.
277    
278  5.  The command line items --regex=pattern and --regexp=pattern were not  5.  The command line items --regex=pattern and --regexp=pattern were not
279      recognized by pcregrep, which required --regex pattern or --regexp pattern      recognized by pcregrep, which required --regex pattern or --regexp pattern
280      (with a space rather than an '='). The man page documented the '=' forms,      (with a space rather than an '='). The man page documented the '=' forms,
281      which are compatible with GNU grep; these now work.      which are compatible with GNU grep; these now work.
282    
283  6.  No libpcreposix.pc file was created for pkg-config; there was just  6.  No libpcreposix.pc file was created for pkg-config; there was just
284      libpcre.pc and libpcrecpp.pc. The omission has been rectified.      libpcre.pc and libpcrecpp.pc. The omission has been rectified.
285    
286  7.  Added #ifndef SUPPORT_UCP into the pcre_ucd.c module, to reduce its size  7.  Added #ifndef SUPPORT_UCP into the pcre_ucd.c module, to reduce its size
287      when UCP support is not needed, by modifying the Python script that      when UCP support is not needed, by modifying the Python script that
288      generates it from Unicode data files. This should not matter if the module      generates it from Unicode data files. This should not matter if the module
289      is correctly used as a library, but I received one complaint about 50K of      is correctly used as a library, but I received one complaint about 50K of
290      unwanted data. My guess is that the person linked everything into his      unwanted data. My guess is that the person linked everything into his
291      program rather than using a library. Anyway, it does no harm.      program rather than using a library. Anyway, it does no harm.
292    
293  8.  A pattern such as /\x{123}{2,2}+/8 was incorrectly compiled; the trigger  8.  A pattern such as /\x{123}{2,2}+/8 was incorrectly compiled; the trigger
294      was a minimum greater than 1 for a wide character in a possessive      was a minimum greater than 1 for a wide character in a possessive
295      repetition. The same bug could also affect patterns like /(\x{ff}{0,2})*/8      repetition. The same bug could also affect patterns like /(\x{ff}{0,2})*/8
296      which had an unlimited repeat of a nested, fixed maximum repeat of a wide      which had an unlimited repeat of a nested, fixed maximum repeat of a wide
297      character. Chaos in the form of incorrect output or a compiling loop could      character. Chaos in the form of incorrect output or a compiling loop could
298      result.      result.
299    
300  9.  The restrictions on what a pattern can contain when partial matching is  9.  The restrictions on what a pattern can contain when partial matching is
301      requested for pcre_exec() have been removed. All patterns can now be      requested for pcre_exec() have been removed. All patterns can now be
302      partially matched by this function. In addition, if there are at least two      partially matched by this function. In addition, if there are at least two
303      slots in the offset vector, the offset of the earliest inspected character      slots in the offset vector, the offset of the earliest inspected character
304      for the match and the offset of the end of the subject are set in them when      for the match and the offset of the end of the subject are set in them when
305      PCRE_ERROR_PARTIAL is returned.      PCRE_ERROR_PARTIAL is returned.
306    
307  10. Partial matching has been split into two forms: PCRE_PARTIAL_SOFT, which is  10. Partial matching has been split into two forms: PCRE_PARTIAL_SOFT, which is
308      synonymous with PCRE_PARTIAL, for backwards compatibility, and      synonymous with PCRE_PARTIAL, for backwards compatibility, and
309      PCRE_PARTIAL_HARD, which causes a partial match to supersede a full match,      PCRE_PARTIAL_HARD, which causes a partial match to supersede a full match,
310      and may be more useful for multi-segment matching, especially with      and may be more useful for multi-segment matching.
311      pcre_exec().  
312    11. Partial matching with pcre_exec() is now more intuitive. A partial match
313  11. Partial matching with pcre_exec() is now more intuitive. A partial match      used to be given if ever the end of the subject was reached; now it is
314      used to be given if ever the end of the subject was reached; now it is      given only if matching could not proceed because another character was
315      given only if matching could not proceed because another character was      needed. This makes a difference in some odd cases such as Z(*FAIL) with the
316      needed. This makes a difference in some odd cases such as Z(*FAIL) with the      string "Z", which now yields "no match" instead of "partial match". In the
317      string "Z", which now yields "no match" instead of "partial match". In the      case of pcre_dfa_exec(), "no match" is given if every matching path for the
318      case of pcre_dfa_exec(), "no match" is given if every matching path for the      final character ended with (*FAIL).
319      final character ended with (*FAIL).  
   
320  12. Restarting a match using pcre_dfa_exec() after a partial match did not work  12. Restarting a match using pcre_dfa_exec() after a partial match did not work
321      if the pattern had a "must contain" character that was already found in the      if the pattern had a "must contain" character that was already found in the
322      earlier partial match, unless partial matching was again requested. For      earlier partial match, unless partial matching was again requested. For
323      example, with the pattern /dog.(body)?/, the "must contain" character is      example, with the pattern /dog.(body)?/, the "must contain" character is
324      "g". If the first part-match was for the string "dog", restarting with      "g". If the first part-match was for the string "dog", restarting with
325      "sbody" failed. This bug has been fixed.      "sbody" failed. This bug has been fixed.
326    
327  13. The string returned by pcre_dfa_exec() after a partial match has been  13. The string returned by pcre_dfa_exec() after a partial match has been
328      changed so that it starts at the first inspected character rather than the      changed so that it starts at the first inspected character rather than the
329      first character of the match. This makes a difference only if the pattern      first character of the match. This makes a difference only if the pattern
330      starts with a lookbehind assertion or \b or \B (\K is not supported by      starts with a lookbehind assertion or \b or \B (\K is not supported by
331      pcre_dfa_exec()). It's an incompatible change, but it makes the two      pcre_dfa_exec()). It's an incompatible change, but it makes the two
332      matching functions compatible, and I think it's the right thing to do.      matching functions compatible, and I think it's the right thing to do.
333    
334  14. Added a pcredemo man page, created automatically from the pcredemo.c file,  14. Added a pcredemo man page, created automatically from the pcredemo.c file,
335      so that the demonstration program is easily available in environments where      so that the demonstration program is easily available in environments where
336      PCRE has not been installed from source.      PCRE has not been installed from source.
337    
338  15. Arranged to add -DPCRE_STATIC to cflags in libpcre.pc, libpcreposix.cp,  15. Arranged to add -DPCRE_STATIC to cflags in libpcre.pc, libpcreposix.cp,
339      libpcrecpp.pc and pcre-config when PCRE is not compiled as a shared      libpcrecpp.pc and pcre-config when PCRE is not compiled as a shared
340      library.      library.
341    
342  16. Added REG_UNGREEDY to the pcreposix interface, at the request of a user.  16. Added REG_UNGREEDY to the pcreposix interface, at the request of a user.
343      It maps to PCRE_UNGREEDY. It is not, of course, POSIX-compatible, but it      It maps to PCRE_UNGREEDY. It is not, of course, POSIX-compatible, but it
344      is not the first non-POSIX option to be added. Clearly some people find      is not the first non-POSIX option to be added. Clearly some people find
345      these options useful.      these options useful.
346    
347  17. If a caller to the POSIX matching function regexec() passes a non-zero  17. If a caller to the POSIX matching function regexec() passes a non-zero
348      value for nmatch with a NULL value for pmatch, the value of      value for nmatch with a NULL value for pmatch, the value of
349      nmatch is forced to zero.      nmatch is forced to zero.
350    
351  18. RunGrepTest did not have a test for the availability of the -u option of  18. RunGrepTest did not have a test for the availability of the -u option of
352      the diff command, as RunTest does. It now checks in the same way as      the diff command, as RunTest does. It now checks in the same way as
353      RunTest, and also checks for the -b option.      RunTest, and also checks for the -b option.
354    
355  19. If an odd number of negated classes containing just a single character  19. If an odd number of negated classes containing just a single character
356      interposed, within parentheses, between a forward reference to a named      interposed, within parentheses, between a forward reference to a named
357      subpattern and the definition of the subpattern, compilation crashed with      subpattern and the definition of the subpattern, compilation crashed with
358      an internal error, complaining that it could not find the referenced      an internal error, complaining that it could not find the referenced
359      subpattern. An example of a crashing pattern is /(?&A)(([^m])(?<A>))/.      subpattern. An example of a crashing pattern is /(?&A)(([^m])(?<A>))/.
360      [The bug was that it was starting one character too far in when skipping      [The bug was that it was starting one character too far in when skipping
361      over the character class, thus treating the ] as data rather than      over the character class, thus treating the ] as data rather than
362      terminating the class. This meant it could skip too much.]      terminating the class. This meant it could skip too much.]
363    
364  20. Added PCRE_NOTEMPTY_ATSTART in order to be able to correctly implement the  20. Added PCRE_NOTEMPTY_ATSTART in order to be able to correctly implement the
365      /g option in pcretest when the pattern contains \K, which makes it possible      /g option in pcretest when the pattern contains \K, which makes it possible
366      to have an empty string match not at the start, even when the pattern is      to have an empty string match not at the start, even when the pattern is
367      anchored. Updated pcretest and pcredemo to use this option.      anchored. Updated pcretest and pcredemo to use this option.
368    
369  21. If the maximum number of capturing subpatterns in a recursion was greater  21. If the maximum number of capturing subpatterns in a recursion was greater
370      than the maximum at the outer level, the higher number was returned, but      than the maximum at the outer level, the higher number was returned, but
371      with unset values at the outer level. The correct (outer level) value is      with unset values at the outer level. The correct (outer level) value is
372      now given.      now given.
373    
374  22. If (*ACCEPT) appeared inside capturing parentheses, previous releases of  22. If (*ACCEPT) appeared inside capturing parentheses, previous releases of
375      PCRE did not set those parentheses (unlike Perl). I have now found a way to      PCRE did not set those parentheses (unlike Perl). I have now found a way to
376      make it do so. The string so far is captured, making this feature      make it do so. The string so far is captured, making this feature
377      compatible with Perl.      compatible with Perl.
378    
379  23. The tests have been re-organized, adding tests 11 and 12, to make it  23. The tests have been re-organized, adding tests 11 and 12, to make it
380      possible to check the Perl 5.10 features against Perl 5.10.      possible to check the Perl 5.10 features against Perl 5.10.
381    
382  24. Perl 5.10 allows subroutine calls in lookbehinds, as long as the subroutine  24. Perl 5.10 allows subroutine calls in lookbehinds, as long as the subroutine
383      pattern matches a fixed length string. PCRE did not allow this; now it      pattern matches a fixed length string. PCRE did not allow this; now it
384      does. Neither allows recursion.      does. Neither allows recursion.
385    
386  25. I finally figured out how to implement a request to provide the minimum  25. I finally figured out how to implement a request to provide the minimum
387      length of subject string that was needed in order to match a given pattern.      length of subject string that was needed in order to match a given pattern.
388      (It was back references and recursion that I had previously got hung up      (It was back references and recursion that I had previously got hung up
389      on.) This code has now been added to pcre_study(); it finds a lower bound      on.) This code has now been added to pcre_study(); it finds a lower bound
390      to the length of subject needed. It is not necessarily the greatest lower      to the length of subject needed. It is not necessarily the greatest lower
391      bound, but using it to avoid searching strings that are too short does give      bound, but using it to avoid searching strings that are too short does give
392      some useful speed-ups. The value is available to calling programs via      some useful speed-ups. The value is available to calling programs via
393      pcre_fullinfo().      pcre_fullinfo().
394    
395  26. While implementing 25, I discovered to my embarrassment that pcretest had  26. While implementing 25, I discovered to my embarrassment that pcretest had
396      not been passing the result of pcre_study() to pcre_dfa_exec(), so the      not been passing the result of pcre_study() to pcre_dfa_exec(), so the
397      study optimizations had never been tested with that matching function.      study optimizations had never been tested with that matching function.
398      Oops. What is worse, even when it was passed study data, there was a bug in      Oops. What is worse, even when it was passed study data, there was a bug in
399      pcre_dfa_exec() that meant it never actually used it. Double oops. There      pcre_dfa_exec() that meant it never actually used it. Double oops. There
400      were also very few tests of studied patterns with pcre_dfa_exec().      were also very few tests of studied patterns with pcre_dfa_exec().
401    
402  27. If (?| is used to create subpatterns with duplicate numbers, they are now  27. If (?| is used to create subpatterns with duplicate numbers, they are now
403      allowed to have the same name, even if PCRE_DUPNAMES is not set. However,      allowed to have the same name, even if PCRE_DUPNAMES is not set. However,
404      on the other side of the coin, they are no longer allowed to have different      on the other side of the coin, they are no longer allowed to have different
405      names, because these cannot be distinguished in PCRE, and this has caused      names, because these cannot be distinguished in PCRE, and this has caused
406      confusion. (This is a difference from Perl.)      confusion. (This is a difference from Perl.)
407    
408    28. When duplicate subpattern names are present (necessarily with different
409        numbers, as required by 27 above), and a test is made by name in a
410        conditional pattern, either for a subpattern having been matched, or for
411        recursion in such a pattern, all the associated numbered subpatterns are
412        tested, and the overall condition is true if the condition is true for any
413        one of them. This is the way Perl works, and is also more like the way
414        testing by number works.
415    
416    
417  Version 7.9 11-Apr-09  Version 7.9 11-Apr-09
418  ---------------------  ---------------------

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