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revision 91 by nigel, Sat Feb 24 21:41:34 2007 UTC revision 100 by ph10, Tue Mar 6 14:53:10 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. Part of the patch fixed a problem with the pcregrep tests. The test of -r
13        for recursive directory scanning broke on some systems because the files
14        are not scanned in any specific order and on different systems the order
15        was different. A call to "sort" has been inserted into RunGrepTest for the
16        approprate test as a short-term fix. In the longer term there may be an
17        alternative.
18    
19     3. I had an email from Eric Raymond about problems translating some of PCRE's
20        man pages to HTML (despite the fact that I distribute HTML pages, some
21        people do their own conversions for various reasons). The problems
22        concerned the use of low-level troff macros .br and .in. I have therefore
23        removed all such uses from the man pages (some were redundant, some could
24        be replaced by .nf/.fi pairs). The maintain/132html script that I use to
25        generate HTML has been updated to handle .nf/.fi and to complain if it
26        encounters .br or .in.
27    
28     4. Updated comments in configure.ac that get placed in config.h.in and also
29        arranged for config.h to be included in the distribution, for the benefit
30        of those who have to compile without Autotools (compare pcre.h).
31    
32    
33    Version 7.0 19-Dec-06
34    ---------------------
35    
36     1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
37        moving to gcc 4.1.1.
38    
39     2. The -S option for pcretest uses setrlimit(); I had omitted to #include
40        sys/time.h, which is documented as needed for this function. It doesn't
41        seem to matter on Linux, but it showed up on some releases of OS X.
42    
43     3. It seems that there are systems where bytes whose values are greater than
44        127 match isprint() in the "C" locale. The "C" locale should be the
45        default when a C program starts up. In most systems, only ASCII printing
46        characters match isprint(). This difference caused the output from pcretest
47        to vary, making some of the tests fail. I have changed pcretest so that:
48    
49        (a) When it is outputting text in the compiled version of a pattern, bytes
50            other than 32-126 are always shown as hex escapes.
51    
52        (b) When it is outputting text that is a matched part of a subject string,
53            it does the same, unless a different locale has been set for the match
54            (using the /L modifier). In this case, it uses isprint() to decide.
55    
56     4. Fixed a major bug that caused incorrect computation of the amount of memory
57        required for a compiled pattern when options that changed within the
58        pattern affected the logic of the preliminary scan that determines the
59        length. The relevant options are -x, and -i in UTF-8 mode. The result was
60        that the computed length was too small. The symptoms of this bug were
61        either the PCRE error "internal error: code overflow" from pcre_compile(),
62        or a glibc crash with a message such as "pcretest: free(): invalid next
63        size (fast)". Examples of patterns that provoked this bug (shown in
64        pcretest format) are:
65    
66          /(?-x: )/x
67          /(?x)(?-x: \s*#\s*)/
68          /((?i)[\x{c0}])/8
69          /(?i:[\x{c0}])/8
70    
71        HOWEVER: Change 17 below makes this fix obsolete as the memory computation
72        is now done differently.
73    
74     5. Applied patches from Google to: (a) add a QuoteMeta function to the C++
75        wrapper classes; (b) implement a new function in the C++ scanner that is
76        more efficient than the old way of doing things because it avoids levels of
77        recursion in the regex matching; (c) add a paragraph to the documentation
78        for the FullMatch() function.
79    
80     6. The escape sequence \n was being treated as whatever was defined as
81        "newline". Not only was this contrary to the documentation, which states
82        that \n is character 10 (hex 0A), but it also went horribly wrong when
83        "newline" was defined as CRLF. This has been fixed.
84    
85     7. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
86        was being set to -1 for the "end of line" case (supposedly a value that no
87        character can have). Though this value is never used (the check for end of
88        line is "zero bytes in current character"), it caused compiler complaints.
89        I've changed it to 0xffffffff.
90    
91     8. In pcre_version.c, the version string was being built by a sequence of
92        C macros that, in the event of PCRE_PRERELEASE being defined as an empty
93        string (as it is for production releases) called a macro with an empty
94        argument. The C standard says the result of this is undefined. The gcc
95        compiler treats it as an empty string (which was what was wanted) but it is
96        reported that Visual C gives an error. The source has been hacked around to
97        avoid this problem.
98    
99     9. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
100        builds of pcretest, and changed the call to _setmode() to use _O_BINARY
101        instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
102        of them did).
103    
104    10. Originally, pcretest opened its input and output without "b"; then I was
105        told that "b" was needed in some environments, so it was added for release
106        5.0 to both the input and output. (It makes no difference on Unix-like
107        systems.) Later I was told that it is wrong for the input on Windows. I've
108        now abstracted the modes into two macros, to make it easier to fiddle with
109        them, and removed "b" from the input mode under Windows.
110    
111    11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
112    
113    12. Added -help and --help to pcretest as an official way of being reminded
114        of the options.
115    
116    13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
117        and pcrecpp.cc because they annoy compilers at high warning levels.
118    
119    14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
120    
121    15. Fixed an occurrence of == in configure.ac that should have been = (shell
122        scripts are not C programs :-) and which was not noticed because it works
123        on Linux.
124    
125    16. pcretest is supposed to handle any length of pattern and data line (as one
126        line or as a continued sequence of lines) by extending its input buffer if
127        necessary. This feature was broken for very long pattern lines, leading to
128        a string of junk being passed to pcre_compile() if the pattern was longer
129        than about 50K.
130    
131    17. I have done a major re-factoring of the way pcre_compile() computes the
132        amount of memory needed for a compiled pattern. Previously, there was code
133        that made a preliminary scan of the pattern in order to do this. That was
134        OK when PCRE was new, but as the facilities have expanded, it has become
135        harder and harder to keep it in step with the real compile phase, and there
136        have been a number of bugs (see for example, 4 above). I have now found a
137        cunning way of running the real compile function in a "fake" mode that
138        enables it to compute how much memory it would need, while actually only
139        ever using a few hundred bytes of working memory and without too many
140        tests of the mode. This should make future maintenance and development
141        easier. A side effect of this work is that the limit of 200 on the nesting
142        depth of parentheses has been removed (though this was never a serious
143        limitation, I suspect). However, there is a downside: pcre_compile() now
144        runs more slowly than before (30% or more, depending on the pattern). I
145        hope this isn't a big issue. There is no effect on runtime performance.
146    
147    18. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
148        newline (only possible for the last line of a file) and it was a
149        pattern that set a locale (followed by /Lsomething), pcretest crashed.
150    
151    19. Added additional timing features to pcretest. (1) The -tm option now times
152        matching only, not compiling. (2) Both -t and -tm can be followed, as a
153        separate command line item, by a number that specifies the number of
154        repeats to use when timing. The default is 50000; this gives better
155        precision, but takes uncomfortably long for very large patterns.
156    
157    20. Extended pcre_study() to be more clever in cases where a branch of a
158        subpattern has no definite first character. For example, (a*|b*)[cd] would
159        previously give no result from pcre_study(). Now it recognizes that the
160        first character must be a, b, c, or d.
161    
162    21. There was an incorrect error "recursive call could loop indefinitely" if
163        a subpattern (or the entire pattern) that was being tested for matching an
164        empty string contained only one non-empty item after a nested subpattern.
165        For example, the pattern (?>\x{100}*)\d(?R) provoked this error
166        incorrectly, because the \d was being skipped in the check.
167    
168    22. The pcretest program now has a new pattern option /B and a command line
169        option -b, which is equivalent to adding /B to every pattern. This causes
170        it to show the compiled bytecode, without the additional information that
171        -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
172        is the same as /B/I).
173    
174    23. A new optimization is now able automatically to treat some sequences such
175        as a*b as a*+b. More specifically, if something simple (such as a character
176        or a simple class like \d) has an unlimited quantifier, and is followed by
177        something that cannot possibly match the quantified thing, the quantifier
178        is automatically "possessified".
179    
180    24. A recursive reference to a subpattern whose number was greater than 39
181        went wrong under certain circumstances in UTF-8 mode. This bug could also
182        have affected the operation of pcre_study().
183    
184    25. Realized that a little bit of performance could be had by replacing
185        (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
186    
187    26. Timing data from pcretest is now shown to 4 decimal places instead of 3.
188    
189    27. Possessive quantifiers such as a++ were previously implemented by turning
190        them into atomic groups such as ($>a+). Now they have their own opcodes,
191        which improves performance. This includes the automatically created ones
192        from 23 above.
193    
194    28. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
195        lookahead was broken if it was not anchored. PCRE was mistakenly expecting
196        the first matched character to be a colon. This applied both to named and
197        numbered groups.
198    
199    29. The ucpinternal.h header file was missing its idempotency #ifdef.
200    
201    30. I was sent a "project" file called libpcre.a.dev which I understand makes
202        building PCRE on Windows easier, so I have included it in the distribution.
203    
204    31. There is now a check in pcretest against a ridiculously large number being
205        returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
206        loop, the loop is abandoned.
207    
208    32. Forward references to subpatterns in conditions such as (?(2)...) where
209        subpattern 2 is defined later cause pcre_compile() to search forwards in
210        the pattern for the relevant set of parentheses. This search went wrong
211        when there were unescaped parentheses in a character class, parentheses
212        escaped with \Q...\E, or parentheses in a #-comment in /x mode.
213    
214    33. "Subroutine" calls and backreferences were previously restricted to
215        referencing subpatterns earlier in the regex. This restriction has now
216        been removed.
217    
218    34. Added a number of extra features that are going to be in Perl 5.10. On the
219        whole, these are just syntactic alternatives for features that PCRE had
220        previously implemented using the Python syntax or my own invention. The
221        other formats are all retained for compatibility.
222    
223        (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
224            as (?P<name>...). The new forms, as well as being in Perl 5.10, are
225            also .NET compatible.
226    
227        (b) A recursion or subroutine call to a named group can now be defined as
228            (?&name) as well as (?P>name).
229    
230        (c) A backreference to a named group can now be defined as \k<name> or
231            \k'name' as well as (?P=name). The new forms, as well as being in Perl
232            5.10, are also .NET compatible.
233    
234        (d) A conditional reference to a named group can now use the syntax
235            (?(<name>) or (?('name') as well as (?(name).
236    
237        (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
238            groups (named and numbered) that are never evaluated inline, but can be
239            called as "subroutines" from elsewhere. In effect, the DEFINE condition
240            is always false. There may be only one alternative in such a group.
241    
242        (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
243            as the simple (?(R). The condition is true only if the most recent
244            recursion is that of the given number or name. It does not search out
245            through the entire recursion stack.
246    
247        (g) The escape \gN or \g{N} has been added, where N is a positive or
248            negative number, specifying an absolute or relative reference.
249    
250    35. Tidied to get rid of some further signed/unsigned compiler warnings and
251        some "unreachable code" warnings.
252    
253    36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
254        things, this adds five new scripts.
255    
256    37. Perl ignores orphaned \E escapes completely. PCRE now does the same.
257        There were also incompatibilities regarding the handling of \Q..\E inside
258        character classes, for example with patterns like [\Qa\E-\Qz\E] where the
259        hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
260    
261    38. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
262        matches an empty string, and forcibly breaks the loop. There were bugs in
263        this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
264        against  aaaa  the result was just "a" rather than "aaaa", for example. Two
265        separate and independent bugs (that affected different cases) have been
266        fixed.
267    
268    39. Refactored the code to abolish the use of different opcodes for small
269        capturing bracket numbers. This is a tidy that I avoided doing when I
270        removed the limit on the number of capturing brackets for 3.5 back in 2001.
271        The new approach is not only tidier, it makes it possible to reduce the
272        memory needed to fix the previous bug (38).
273    
274    40. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
275        sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
276        processing dot, circumflex, or dollar metacharacters, or #-comments in /x
277        mode.
278    
279    41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
280        report.
281    
282    42. Applied patch, originally from Ari Pollak, modified by Google, to allow
283        copy construction and assignment in the C++ wrapper.
284    
285    43. Updated pcregrep to support "--newline=any". In the process, I fixed a
286        couple of bugs that could have given wrong results in the "--newline=crlf"
287        case.
288    
289    44. Added a number of casts and did some reorganization of signed/unsigned int
290        variables following suggestions from Dair Grant. Also renamed the variable
291        "this" as "item" because it is a C++ keyword.
292    
293    45. Arranged for dftables to add
294    
295          #include "pcre_internal.h"
296    
297        to pcre_chartables.c because without it, gcc 4.x may remove the array
298        definition from the final binary if PCRE is built into a static library and
299        dead code stripping is activated.
300    
301    46. For an unanchored pattern, if a match attempt fails at the start of a
302        newline sequence, and the newline setting is CRLF or ANY, and the next two
303        characters are CRLF, advance by two characters instead of one.
304    
305    
306  Version 6.7 04-Jul-06  Version 6.7 04-Jul-06
307  ---------------------  ---------------------
308    

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