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revision 591 by ph10, Sat Jan 15 17:26:57 2011 UTC revision 661 by ph10, Sun Aug 21 09:00:54 2011 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
4    Version 8.20
5    ------------
7    1. Change 37 of 8.13 broke patterns like [:a]...[b:] because it thought it had
8    a POSIX class. After further experiments with Perl, which convinced me that
9    Perl has bugs and confusions, a closing square bracket is no longer allowed in
10    a POSIX name.
13    Version 8.13 16-Aug-2011
14    ------------------------
16    1.  The Unicode data tables have been updated to Unicode 6.0.0.
18    2.  Two minor typos in pcre_internal.h have been fixed.
20    3.  Added #include <string.h> to pcre_scanner_unittest.cc, pcrecpp.cc, and
21        pcrecpp_unittest.cc. They are needed for strcmp(), memset(), and strchr()
22        in some environments (e.g. Solaris 10/SPARC using Sun Studio 12U2).
24    4.  There were a number of related bugs in the code for matching backrefences
25        caselessly in UTF-8 mode when codes for the characters concerned were
26        different numbers of bytes. For example, U+023A and U+2C65 are an upper
27        and lower case pair, using 2 and 3 bytes, respectively. The main bugs were:
28        (a) A reference to 3 copies of a 2-byte code matched only 2 of a 3-byte
29        code. (b) A reference to 2 copies of a 3-byte code would not match 2 of a
30        2-byte code at the end of the subject (it thought there wasn't enough data
31        left).
33    5.  Comprehensive information about what went wrong is now returned by
34        pcre_exec() and pcre_dfa_exec() when the UTF-8 string check fails, as long
35        as the output vector has at least 2 elements. The offset of the start of
36        the failing character and a reason code are placed in the vector.
38    6.  When the UTF-8 string check fails for pcre_compile(), the offset that is
39        now returned is for the first byte of the failing character, instead of the
40        last byte inspected. This is an incompatible change, but I hope it is small
41        enough not to be a problem. It makes the returned offset consistent with
42        pcre_exec() and pcre_dfa_exec().
44    7.  pcretest now gives a text phrase as well as the error number when
45        pcre_exec() or pcre_dfa_exec() fails; if the error is a UTF-8 check
46        failure, the offset and reason code are output.
48    8.  When \R was used with a maximizing quantifier it failed to skip backwards
49        over a \r\n pair if the subsequent match failed. Instead, it just skipped
50        back over a single character (\n). This seems wrong (because it treated the
51        two characters as a single entity when going forwards), conflicts with the
52        documentation that \R is equivalent to (?>\r\n|\n|...etc), and makes the
53        behaviour of \R* different to (\R)*, which also seems wrong. The behaviour
54        has been changed.
56    9.  Some internal refactoring has changed the processing so that the handling
57        of the PCRE_CASELESS and PCRE_MULTILINE options is done entirely at compile
58        time (the PCRE_DOTALL option was changed this way some time ago: version
59        7.7 change 16). This has made it possible to abolish the OP_OPT op code,
60        which was always a bit of a fudge. It also means that there is one less
61        argument for the match() function, which reduces its stack requirements
62        slightly. This change also fixes an incompatibility with Perl: the pattern
63        (?i:([^b]))(?1) should not match "ab", but previously PCRE gave a match.
65    10. More internal refactoring has drastically reduced the number of recursive
66        calls to match() for possessively repeated groups such as (abc)++ when
67        using pcre_exec().
69    11. While implementing 10, a number of bugs in the handling of groups were
70        discovered and fixed:
72        (?<=(a)+) was not diagnosed as invalid (non-fixed-length lookbehind).
73        (a|)*(?1) gave a compile-time internal error.
74        ((a|)+)+  did not notice that the outer group could match an empty string.
75        (^a|^)+   was not marked as anchored.
76        (.*a|.*)+ was not marked as matching at start or after a newline.
78    12. Yet more internal refactoring has removed another argument from the match()
79        function. Special calls to this function are now indicated by setting a
80        value in a variable in the "match data" data block.
82    13. Be more explicit in pcre_study() instead of relying on "default" for
83        opcodes that mean there is no starting character; this means that when new
84        ones are added and accidentally left out of pcre_study(), testing should
85        pick them up.
87    14. The -s option of pcretest has been documented for ages as being an old
88        synonym of -m (show memory usage). I have changed it to mean "force study
89        for every regex", that is, assume /S for every regex. This is similar to -i
90        and -d etc. It's slightly incompatible, but I'm hoping nobody is still
91        using it. It makes it easier to run collections of tests with and without
92        study enabled, and thereby test pcre_study() more easily. All the standard
93        tests are now run with and without -s (but some patterns can be marked as
94        "never study" - see 20 below).
96    15. When (*ACCEPT) was used in a subpattern that was called recursively, the
97        restoration of the capturing data to the outer values was not happening
98        correctly.
100    16. If a recursively called subpattern ended with (*ACCEPT) and matched an
101        empty string, and PCRE_NOTEMPTY was set, pcre_exec() thought the whole
102        pattern had matched an empty string, and so incorrectly returned a no
103        match.
105    17. There was optimizing code for the last branch of non-capturing parentheses,
106        and also for the obeyed branch of a conditional subexpression, which used
107        tail recursion to cut down on stack usage. Unfortunately, now that there is
108        the possibility of (*THEN) occurring in these branches, tail recursion is
109        no longer possible because the return has to be checked for (*THEN). These
110        two optimizations have therefore been removed.
112    18. If a pattern containing \R was studied, it was assumed that \R always
113        matched two bytes, thus causing the minimum subject length to be
114        incorrectly computed because \R can also match just one byte.
116    19. If a pattern containing (*ACCEPT) was studied, the minimum subject length
117        was incorrectly computed.
119    20. If /S is present twice on a test pattern in pcretest input, it now
120        *disables* studying, thereby overriding the use of -s on the command line
121        (see 14 above). This is necessary for one or two tests to keep the output
122        identical in both cases.
124    21. When (*ACCEPT) was used in an assertion that matched an empty string and
125        PCRE_NOTEMPTY was set, PCRE applied the non-empty test to the assertion.
127    22. When an atomic group that contained a capturing parenthesis was
128        successfully matched, but the branch in which it appeared failed, the
129        capturing was not being forgotten if a higher numbered group was later
130        captured. For example, /(?>(a))b|(a)c/ when matching "ac" set capturing
131        group 1 to "a", when in fact it should be unset. This applied to multi-
132        branched capturing and non-capturing groups, repeated or not, and also to
133        positive assertions (capturing in negative assertions does not happen
134        in PCRE) and also to nested atomic groups.
136    23. Add the ++ qualifier feature to pcretest, to show the remainder of the
137        subject after a captured substring, to make it easier to tell which of a
138        number of identical substrings has been captured.
140    24. The way atomic groups are processed by pcre_exec() has been changed so that
141        if they are repeated, backtracking one repetition now resets captured
142        values correctly. For example, if ((?>(a+)b)+aabab) is matched against
143        "aaaabaaabaabab" the value of captured group 2 is now correctly recorded as
144        "aaa". Previously, it would have been "a". As part of this code
145        refactoring, the way recursive calls are handled has also been changed.
147    25. If an assertion condition captured any substrings, they were not passed
148        back unless some other capturing happened later. For example, if
149        (?(?=(a))a) was matched against "a", no capturing was returned.
151    26. When studying a pattern that contained subroutine calls or assertions,
152        the code for finding the minimum length of a possible match was handling
153        direct recursions such as (xxx(?1)|yyy) but not mutual recursions (where
154        group 1 called group 2 while simultaneously a separate group 2 called group
155        1). A stack overflow occurred in this case. I have fixed this by limiting
156        the recursion depth to 10.
158    27. Updated RunTest.bat in the distribution to the version supplied by Tom
159        Fortmann. This supports explicit test numbers on the command line, and has
160        argument validation and error reporting.
162    28. An instance of \X with an unlimited repeat could fail if at any point the
163        first character it looked at was a mark character.
165    29. Some minor code refactoring concerning Unicode properties and scripts
166        should reduce the stack requirement of match() slightly.
168    30. Added the '=' option to pcretest to check the setting of unused capturing
169        slots at the end of the pattern, which are documented as being -1, but are
170        not included in the return count.
172    31. If \k was not followed by a braced, angle-bracketed, or quoted name, PCRE
173        compiled something random. Now it gives a compile-time error (as does
174        Perl).
176    32. A *MARK encountered during the processing of a positive assertion is now
177        recorded and passed back (compatible with Perl).
179    33. If --only-matching or --colour was set on a pcregrep call whose pattern
180        had alternative anchored branches, the search for a second match in a line
181        was done as if at the line start. Thus, for example, /^01|^02/ incorrectly
182        matched the line "0102" twice. The same bug affected patterns that started
183        with a backwards assertion. For example /\b01|\b02/ also matched "0102"
184        twice.
186    34. Previously, PCRE did not allow quantification of assertions. However, Perl
187        does, and because of capturing effects, quantifying parenthesized
188        assertions may at times be useful. Quantifiers are now allowed for
189        parenthesized assertions.
191    35. A minor code tidy in pcre_compile() when checking options for \R usage.
193    36. \g was being checked for fancy things in a character class, when it should
194        just be a literal "g".
196    37. PCRE was rejecting [:a[:digit:]] whereas Perl was not. It seems that the
197        appearance of a nested POSIX class supersedes an apparent external class.
198        For example, [:a[:digit:]b:] matches "a", "b", ":", or a digit. Also,
199        unescaped square brackets may also appear as part of class names. For
200        example, [:a[:abc]b:] gives unknown class "[:abc]b:]". PCRE now behaves
201        more like Perl. (But see 8.20/1 above.)
203    38. PCRE was giving an error for \N with a braced quantifier such as {1,} (this
204        was because it thought it was \N{name}, which is not supported).
206    39. Add minix to OS list not supporting the -S option in pcretest.
208    40. PCRE tries to detect cases of infinite recursion at compile time, but it
209        cannot analyze patterns in sufficient detail to catch mutual recursions
210        such as ((?1))((?2)). There is now a runtime test that gives an error if a
211        subgroup is called recursively as a subpattern for a second time at the
212        same position in the subject string. In previous releases this might have
213        been caught by the recursion limit, or it might have run out of stack.
215    41. A pattern such as /(?(R)a+|(?R)b)/ is quite safe, as the recursion can
216        happen only once. PCRE was, however incorrectly giving a compile time error
217        "recursive call could loop indefinitely" because it cannot analyze the
218        pattern in sufficient detail. The compile time test no longer happens when
219        PCRE is compiling a conditional subpattern, but actual runaway loops are
220        now caught at runtime (see 40 above).
222    42. It seems that Perl allows any characters other than a closing parenthesis
223        to be part of the NAME in (*MARK:NAME) and other backtracking verbs. PCRE
224        has been changed to be the same.
226    43. Updated configure.ac to put in more quoting round AC_LANG_PROGRAM etc. so
227        as not to get warnings when autogen.sh is called. Also changed
228        AC_PROG_LIBTOOL (deprecated) to LT_INIT (the current macro).
230    44. To help people who use pcregrep to scan files containing exceedingly long
231        lines, the following changes have been made:
233        (a) The default value of the buffer size parameter has been increased from
234            8K to 20K. (The actual buffer used is three times this size.)
236        (b) The default can be changed by ./configure --with-pcregrep-bufsize when
237            PCRE is built.
239        (c) A --buffer-size=n option has been added to pcregrep, to allow the size
240            to be set at run time.
242        (d) Numerical values in pcregrep options can be followed by K or M, for
243            example --buffer-size=50K.
245        (e) If a line being scanned overflows pcregrep's buffer, an error is now
246            given and the return code is set to 2.
248    45. Add a pointer to the latest mark to the callout data block.
250    46. The pattern /.(*F)/, when applied to "abc" with PCRE_PARTIAL_HARD, gave a
251        partial match of an empty string instead of no match. This was specific to
252        the use of ".".
254    47. The pattern /f.*/8s, when applied to "for" with PCRE_PARTIAL_HARD, gave a
255        complete match instead of a partial match. This bug was dependent on both
256        the PCRE_UTF8 and PCRE_DOTALL options being set.
258    48. For a pattern such as /\babc|\bdef/ pcre_study() was failing to set up the
259        starting byte set, because \b was not being ignored.
262  Version 8.12 15-Jan-2011  Version 8.12 15-Jan-2011
263  ------------------------  ------------------------

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