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revision 91 by nigel, Sat Feb 24 21:41:34 2007 UTC revision 99 by ph10, Tue Mar 6 12:27:42 2007 UTC
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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
3    
4    Version 7.1 05-Mar-07
5    ---------------------
6    
7     1. Applied Bob Rossi and Daniel G's patches to convert the build system to one
8        that is more "standard", making use of automake and other autotools. There
9        is some re-arrangement of the files and adjustment of comments consequent
10        on this.
11    
12     2. I had an email from Eric Raymond about problems translating some of PCRE's
13        man pages to HTML (despite the fact that I distribute HTML pages, some
14        people do their own conversions for various reasons). The problems
15        concerned the use of low-level troff macros .br and .in. I have therefore
16        removed all such uses from the man pages (some were redundant, some could
17        be replaced by .nf/.fi pairs). The maintain/132html script that I use to
18        generate HTML has been updated to handle .nf/.fi and to complain if it
19        encounters .br or .in.
20    
21    
22    Version 7.0 19-Dec-06
23    ---------------------
24    
25     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
26        moving to gcc 4.1.1.
27    
28     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
29        sys/time.h, which is documented as needed for this function. It doesn't
30        seem to matter on Linux, but it showed up on some releases of OS X.
31    
32     3. It seems that there are systems where bytes whose values are greater than
33        127 match isprint() in the "C" locale. The "C" locale should be the
34        default when a C program starts up. In most systems, only ASCII printing
35        characters match isprint(). This difference caused the output from pcretest
36        to vary, making some of the tests fail. I have changed pcretest so that:
37    
38        (a) When it is outputting text in the compiled version of a pattern, bytes
39            other than 32-126 are always shown as hex escapes.
40    
41        (b) When it is outputting text that is a matched part of a subject string,
42            it does the same, unless a different locale has been set for the match
43            (using the /L modifier). In this case, it uses isprint() to decide.
44    
45     4. Fixed a major bug that caused incorrect computation of the amount of memory
46        required for a compiled pattern when options that changed within the
47        pattern affected the logic of the preliminary scan that determines the
48        length. The relevant options are -x, and -i in UTF-8 mode. The result was
49        that the computed length was too small. The symptoms of this bug were
50        either the PCRE error "internal error: code overflow" from pcre_compile(),
51        or a glibc crash with a message such as "pcretest: free(): invalid next
52        size (fast)". Examples of patterns that provoked this bug (shown in
53        pcretest format) are:
54    
55          /(?-x: )/x
56          /(?x)(?-x: \s*#\s*)/
57          /((?i)[\x{c0}])/8
58          /(?i:[\x{c0}])/8
59    
60        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
61        is now done differently.
62    
63     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
64        wrapper classes; (b) implement a new function in the C++ scanner that is
65        more efficient than the old way of doing things because it avoids levels of
66        recursion in the regex matching; (c) add a paragraph to the documentation
67        for the FullMatch() function.
68    
69     6. The escape sequence \n was being treated as whatever was defined as
70        "newline". Not only was this contrary to the documentation, which states
71        that \n is character 10 (hex 0A), but it also went horribly wrong when
72        "newline" was defined as CRLF. This has been fixed.
73    
74     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
75        was being set to -1 for the "end of line" case (supposedly a value that no
76        character can have). Though this value is never used (the check for end of
77        line is "zero bytes in current character"), it caused compiler complaints.
78        I've changed it to 0xffffffff.
79    
80     8. In pcre_version.c, the version string was being built by a sequence of
81        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
82        string (as it is for production releases) called a macro with an empty
83        argument. The C standard says the result of this is undefined. The gcc
84        compiler treats it as an empty string (which was what was wanted) but it is
85        reported that Visual C gives an error. The source has been hacked around to
86        avoid this problem.
87    
88     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
89        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
90        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
91        of them did).
92    
93    10. Originally, pcretest opened its input and output without "b"; then I was
94        told that "b" was needed in some environments, so it was added for release
95        5.0 to both the input and output. (It makes no difference on Unix-like
96        systems.) Later I was told that it is wrong for the input on Windows. I've
97        now abstracted the modes into two macros, to make it easier to fiddle with
98        them, and removed "b" from the input mode under Windows.
99    
100    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
101    
102    12. Added -help and --help to pcretest as an official way of being reminded
103        of the options.
104    
105    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
106        and pcrecpp.cc because they annoy compilers at high warning levels.
107    
108    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
109    
110    15. Fixed an occurrence of == in configure.ac that should have been = (shell
111        scripts are not C programs :-) and which was not noticed because it works
112        on Linux.
113    
114    16. pcretest is supposed to handle any length of pattern and data line (as one
115        line or as a continued sequence of lines) by extending its input buffer if
116        necessary. This feature was broken for very long pattern lines, leading to
117        a string of junk being passed to pcre_compile() if the pattern was longer
118        than about 50K.
119    
120    17. I have done a major re-factoring of the way pcre_compile() computes the
121        amount of memory needed for a compiled pattern. Previously, there was code
122        that made a preliminary scan of the pattern in order to do this. That was
123        OK when PCRE was new, but as the facilities have expanded, it has become
124        harder and harder to keep it in step with the real compile phase, and there
125        have been a number of bugs (see for example, 4 above). I have now found a
126        cunning way of running the real compile function in a "fake" mode that
127        enables it to compute how much memory it would need, while actually only
128        ever using a few hundred bytes of working memory and without too many
129        tests of the mode. This should make future maintenance and development
130        easier. A side effect of this work is that the limit of 200 on the nesting
131        depth of parentheses has been removed (though this was never a serious
132        limitation, I suspect). However, there is a downside: pcre_compile() now
133        runs more slowly than before (30% or more, depending on the pattern). I
134        hope this isn't a big issue. There is no effect on runtime performance.
135    
136    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
137        newline (only possible for the last line of a file) and it was a
138        pattern that set a locale (followed by /Lsomething), pcretest crashed.
139    
140    19. Added additional timing features to pcretest. (1) The -tm option now times
141        matching only, not compiling. (2) Both -t and -tm can be followed, as a
142        separate command line item, by a number that specifies the number of
143        repeats to use when timing. The default is 50000; this gives better
144        precision, but takes uncomfortably long for very large patterns.
145    
146    20. Extended pcre_study() to be more clever in cases where a branch of a
147        subpattern has no definite first character. For example, (a*|b*)[cd] would
148        previously give no result from pcre_study(). Now it recognizes that the
149        first character must be a, b, c, or d.
150    
151    21. There was an incorrect error "recursive call could loop indefinitely" if
152        a subpattern (or the entire pattern) that was being tested for matching an
153        empty string contained only one non-empty item after a nested subpattern.
154        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
155        incorrectly, because the \d was being skipped in the check.
156    
157    22. The pcretest program now has a new pattern option /B and a command line
158        option -b, which is equivalent to adding /B to every pattern. This causes
159        it to show the compiled bytecode, without the additional information that
160        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
161        is the same as /B/I).
162    
163    23. A new optimization is now able automatically to treat some sequences such
164        as a*b as a*+b. More specifically, if something simple (such as a character
165        or a simple class like \d) has an unlimited quantifier, and is followed by
166        something that cannot possibly match the quantified thing, the quantifier
167        is automatically "possessified".
168    
169    24. A recursive reference to a subpattern whose number was greater than 39
170        went wrong under certain circumstances in UTF-8 mode. This bug could also
171        have affected the operation of pcre_study().
172    
173    25. Realized that a little bit of performance could be had by replacing
174        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
175    
176    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
177    
178    27. Possessive quantifiers such as a++ were previously implemented by turning
179        them into atomic groups such as ($>a+). Now they have their own opcodes,
180        which improves performance. This includes the automatically created ones
181        from 23 above.
182    
183    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
184        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
185        the first matched character to be a colon. This applied both to named and
186        numbered groups.
187    
188    29. The ucpinternal.h header file was missing its idempotency #ifdef.
189    
190    30. I was sent a "project" file called libpcre.a.dev which I understand makes
191        building PCRE on Windows easier, so I have included it in the distribution.
192    
193    31. There is now a check in pcretest against a ridiculously large number being
194        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
195        loop, the loop is abandoned.
196    
197    32. Forward references to subpatterns in conditions such as (?(2)...) where
198        subpattern 2 is defined later cause pcre_compile() to search forwards in
199        the pattern for the relevant set of parentheses. This search went wrong
200        when there were unescaped parentheses in a character class, parentheses
201        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
202    
203    33. "Subroutine" calls and backreferences were previously restricted to
204        referencing subpatterns earlier in the regex. This restriction has now
205        been removed.
206    
207    34. Added a number of extra features that are going to be in Perl 5.10. On the
208        whole, these are just syntactic alternatives for features that PCRE had
209        previously implemented using the Python syntax or my own invention. The
210        other formats are all retained for compatibility.
211    
212        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
213            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
214            also .NET compatible.
215    
216        (b) A recursion or subroutine call to a named group can now be defined as
217            (?&name) as well as (?P>name).
218    
219        (c) A backreference to a named group can now be defined as \k<name> or
220            \k'name' as well as (?P=name). The new forms, as well as being in Perl
221            5.10, are also .NET compatible.
222    
223        (d) A conditional reference to a named group can now use the syntax
224            (?(<name>) or (?('name') as well as (?(name).
225    
226        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
227            groups (named and numbered) that are never evaluated inline, but can be
228            called as "subroutines" from elsewhere. In effect, the DEFINE condition
229            is always false. There may be only one alternative in such a group.
230    
231        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
232            as the simple (?(R). The condition is true only if the most recent
233            recursion is that of the given number or name. It does not search out
234            through the entire recursion stack.
235    
236        (g) The escape \gN or \g{N} has been added, where N is a positive or
237            negative number, specifying an absolute or relative reference.
238    
239    35. Tidied to get rid of some further signed/unsigned compiler warnings and
240        some "unreachable code" warnings.
241    
242    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
243        things, this adds five new scripts.
244    
245    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
246        There were also incompatibilities regarding the handling of \Q..\E inside
247        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
248        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
249    
250    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
251        matches an empty string, and forcibly breaks the loop. There were bugs in
252        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
253        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
254        separate and independent bugs (that affected different cases) have been
255        fixed.
256    
257    39. Refactored the code to abolish the use of different opcodes for small
258        capturing bracket numbers. This is a tidy that I avoided doing when I
259        removed the limit on the number of capturing brackets for 3.5 back in 2001.
260        The new approach is not only tidier, it makes it possible to reduce the
261        memory needed to fix the previous bug (38).
262    
263    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
264        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
265        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
266        mode.
267    
268    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
269        report.
270    
271    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
272        copy construction and assignment in the C++ wrapper.
273    
274    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
275        couple of bugs that could have given wrong results in the "--newline=crlf"
276        case.
277    
278    44. Added a number of casts and did some reorganization of signed/unsigned int
279        variables following suggestions from Dair Grant. Also renamed the variable
280        "this" as "item" because it is a C++ keyword.
281    
282    45. Arranged for dftables to add
283    
284          #include "pcre_internal.h"
285    
286        to pcre_chartables.c because without it, gcc 4.x may remove the array
287        definition from the final binary if PCRE is built into a static library and
288        dead code stripping is activated.
289    
290    46. For an unanchored pattern, if a match attempt fails at the start of a
291        newline sequence, and the newline setting is CRLF or ANY, and the next two
292        characters are CRLF, advance by two characters instead of one.
293    
294    
295  Version 6.7 04-Jul-06  Version 6.7 04-Jul-06
296  ---------------------  ---------------------
297    

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