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Sat Feb 24 21:40:30 2007 UTC (8 years, 2 months ago) by nigel
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Load pcre-4.5 into code/trunk.

1 nigel 3 ChangeLog for PCRE
2     ------------------
4 nigel 73 Version 4.5 01-Dec-03
5     ---------------------
7     1. There has been some re-arrangement of the code for the match() function so
8     that it can be compiled in a version that does not call itself recursively.
9     Instead, it keeps those local variables that need separate instances for
10     each "recursion" in a frame on the heap, and gets/frees frames whenever it
11     needs to "recurse". Keeping track of where control must go is done by means
12     of setjmp/longjmp. The whole thing is implemented by a set of macros that
13     hide most of the details from the main code, and operates only if
14     NO_RECURSE is defined while compiling pcre.c. If PCRE is built using the
15     "configure" mechanism, "--disable-stack-for-recursion" turns on this way of
16     operating.
18     To make it easier for callers to provide specially tailored get/free
19     functions for this usage, two new functions, pcre_stack_malloc, and
20     pcre_stack_free, are used. They are always called in strict stacking order,
21     and the size of block requested is always the same.
23     The PCRE_CONFIG_STACKRECURSE info parameter can be used to find out whether
24     PCRE has been compiled to use the stack or the heap for recursion. The
25     -C option of pcretest uses this to show which version is compiled.
27     A new data escape \S, is added to pcretest; it causes the amounts of store
28     obtained and freed by both kinds of malloc/free at match time to be added
29     to the output.
31     2. Changed the locale test to use "fr_FR" instead of "fr" because that's
32     what's available on my current Linux desktop machine.
34     3. When matching a UTF-8 string, the test for a valid string at the start has
35     been extended. If start_offset is not zero, PCRE now checks that it points
36     to a byte that is the start of a UTF-8 character. If not, it returns
37     PCRE_ERROR_BADUTF8_OFFSET (-11). Note: the whole string is still checked;
38     this is necessary because there may be backward assertions in the pattern.
39     When matching the same subject several times, it may save resources to use
40     PCRE_NO_UTF8_CHECK on all but the first call if the string is long.
42     4. The code for checking the validity of UTF-8 strings has been tightened so
43     that it rejects (a) strings containing 0xfe or 0xff bytes and (b) strings
44     containing "overlong sequences".
46     5. Fixed a bug (appearing twice) that I could not find any way of exploiting!
47     I had written "if ((digitab[*p++] && chtab_digit) == 0)" where the "&&"
48     should have been "&", but it just so happened that all the cases this let
49     through by mistake were picked up later in the function.
51     6. I had used a variable called "isblank" - this is a C99 function, causing
52     some compilers to warn. To avoid this, I renamed it (as "blankclass").
54     7. Cosmetic: (a) only output another newline at the end of pcretest if it is
55     prompting; (b) run "./pcretest /dev/null" at the start of the test script
56     so the version is shown; (c) stop "make test" echoing "./RunTest".
58     8. Added patches from David Burgess to enable PCRE to run on EBCDIC systems.
60     9. The prototype for memmove() for systems that don't have it was using
61     size_t, but the inclusion of the header that defines size_t was later. I've
62     moved the #includes for the C headers earlier to avoid this.
64     10. Added some adjustments to the code to make it easier to compiler on certain
65     special systems:
67     (a) Some "const" qualifiers were missing.
68     (b) Added the macro EXPORT before all exported functions; by default this
69     is defined to be empty.
70     (c) Changed the dftables auxiliary program (that builds chartables.c) so
71     that it reads its output file name as an argument instead of writing
72     to the standard output and assuming this can be redirected.
74     11. In UTF-8 mode, if a recursive reference (e.g. (?1)) followed a character
75     class containing characters with values greater than 255, PCRE compilation
76     went into a loop.
78     12. A recursive reference to a subpattern that was within another subpattern
79     that had a minimum quantifier of zero caused PCRE to crash. For example,
80     (x(y(?2))z)? provoked this bug with a subject that got as far as the
81     recursion. If the recursively-called subpattern itself had a zero repeat,
82     that was OK.
84     13. In pcretest, the buffer for reading a data line was set at 30K, but the
85     buffer into which it was copied (for escape processing) was still set at
86     1024, so long lines caused crashes.
88     14. A pattern such as /[ab]{1,3}+/ failed to compile, giving the error
89     "internal error: code overflow...". This applied to any character class
90     that was followed by a possessive quantifier.
92     15. Modified the Makefile to add libpcre.la as a prerequisite for
93     libpcreposix.la because I was told this is needed for a parallel build to
94     work.
96     16. If a pattern that contained .* following optional items at the start was
97     studied, the wrong optimizing data was generated, leading to matching
98     errors. For example, studying /[ab]*.*c/ concluded, erroneously, that any
99     matching string must start with a or b or c. The correct conclusion for
100     this pattern is that a match can start with any character.
103 nigel 71 Version 4.4 13-Aug-03
104     ---------------------
106     1. In UTF-8 mode, a character class containing characters with values between
107     127 and 255 was not handled correctly if the compiled pattern was studied.
108     In fixing this, I have also improved the studying algorithm for such
109     classes (slightly).
111     2. Three internal functions had redundant arguments passed to them. Removal
112     might give a very teeny performance improvement.
114     3. Documentation bug: the value of the capture_top field in a callout is *one
115     more than* the number of the hightest numbered captured substring.
117     4. The Makefile linked pcretest and pcregrep with -lpcre, which could result
118     in incorrectly linking with a previously installed version. They now link
119     explicitly with libpcre.la.
121     5. configure.in no longer needs to recognize Cygwin specially.
123     6. A problem in pcre.in for Windows platforms is fixed.
125     7. If a pattern was successfully studied, and the -d (or /D) flag was given to
126     pcretest, it used to include the size of the study block as part of its
127     output. Unfortunately, the structure contains a field that has a different
128     size on different hardware architectures. This meant that the tests that
129     showed this size failed. As the block is currently always of a fixed size,
130     this information isn't actually particularly useful in pcretest output, so
131     I have just removed it.
133     8. Three pre-processor statements accidentally did not start in column 1.
134     Sadly, there are *still* compilers around that complain, even though
135     standard C has not required this for well over a decade. Sigh.
137     9. In pcretest, the code for checking callouts passed small integers in the
138     callout_data field, which is a void * field. However, some picky compilers
139     complained about the casts involved for this on 64-bit systems. Now
140     pcretest passes the address of the small integer instead, which should get
141     rid of the warnings.
143     10. By default, when in UTF-8 mode, PCRE now checks for valid UTF-8 strings at
144     both compile and run time, and gives an error if an invalid UTF-8 sequence
145     is found. There is a option for disabling this check in cases where the
146     string is known to be correct and/or the maximum performance is wanted.
148     11. In response to a bug report, I changed one line in Makefile.in from
150     -Wl,--out-implib,.libs/lib@WIN_PREFIX@pcreposix.dll.a \
151     to
152     -Wl,--out-implib,.libs/@WIN_PREFIX@libpcreposix.dll.a \
154     to look similar to other lines, but I have no way of telling whether this
155     is the right thing to do, as I do not use Windows. No doubt I'll get told
156     if it's wrong...
159 nigel 69 Version 4.3 21-May-03
160     ---------------------
162     1. Two instances of @WIN_PREFIX@ omitted from the Windows targets in the
163     Makefile.
165     2. Some refactoring to improve the quality of the code:
167     (i) The utf8_table... variables are now declared "const".
169     (ii) The code for \cx, which used the "case flipping" table to upper case
170     lower case letters, now just substracts 32. This is ASCII-specific,
171     but the whole concept of \cx is ASCII-specific, so it seems
172     reasonable.
174     (iii) PCRE was using its character types table to recognize decimal and
175     hexadecimal digits in the pattern. This is silly, because it handles
176     only 0-9, a-f, and A-F, but the character types table is locale-
177     specific, which means strange things might happen. A private
178     table is now used for this - though it costs 256 bytes, a table is
179     much faster than multiple explicit tests. Of course, the standard
180     character types table is still used for matching digits in subject
181     strings against \d.
183     (iv) Strictly, the identifier ESC_t is reserved by POSIX (all identifiers
184     ending in _t are). So I've renamed it as ESC_tee.
186     3. The first argument for regexec() in the POSIX wrapper should have been
187     defined as "const".
189     4. Changed pcretest to use malloc() for its buffers so that they can be
190     Electric Fenced for debugging.
192     5. There were several places in the code where, in UTF-8 mode, PCRE would try
193     to read one or more bytes before the start of the subject string. Often this
194     had no effect on PCRE's behaviour, but in some circumstances it could
195     provoke a segmentation fault.
197     6. A lookbehind at the start of a pattern in UTF-8 mode could also cause PCRE
198     to try to read one or more bytes before the start of the subject string.
200     7. A lookbehind in a pattern matched in non-UTF-8 mode on a PCRE compiled with
201     UTF-8 support could misbehave in various ways if the subject string
202     contained bytes with the 0x80 bit set and the 0x40 bit unset in a lookbehind
203     area. (PCRE was not checking for the UTF-8 mode flag, and trying to move
204     back over UTF-8 characters.)
207 nigel 67 Version 4.2 14-Apr-03
208     ---------------------
210     1. Typo "#if SUPPORT_UTF8" instead of "#ifdef SUPPORT_UTF8" fixed.
212     2. Changes to the building process, supplied by Ronald Landheer-Cieslak
213     [ON_WINDOWS]: new variable, "#" on non-Windows platforms
214     [NOT_ON_WINDOWS]: new variable, "#" on Windows platforms
215     [WIN_PREFIX]: new variable, "cyg" for Cygwin
216     * Makefile.in: use autoconf substitution for OBJEXT, EXEEXT, BUILD_OBJEXT
217     and BUILD_EXEEXT
218     Note: automatic setting of the BUILD variables is not yet working
219     set CPPFLAGS and BUILD_CPPFLAGS (but don't use yet) - should be used at
220     compile-time but not at link-time
221     [LINK]: use for linking executables only
222     make different versions for Windows and non-Windows
223     [LINKLIB]: new variable, copy of UNIX-style LINK, used for linking
224     libraries
225     [LINK_FOR_BUILD]: new variable
226     [OBJEXT]: use throughout
227     [EXEEXT]: use throughout
228     <winshared>: new target
229     <wininstall>: new target
230     <dftables.o>: use native compiler
231     <dftables>: use native linker
232     <install>: handle Windows platform correctly
233     <clean>: ditto
234     <check>: ditto
235     copy DLL to top builddir before testing
237     As part of these changes, -no-undefined was removed again. This was reported
238     to give trouble on HP-UX 11.0, so getting rid of it seems like a good idea
239     in any case.
241     3. Some tidies to get rid of compiler warnings:
243     . In the match_data structure, match_limit was an unsigned long int, whereas
244     match_call_count was an int. I've made them both unsigned long ints.
246     . In pcretest the fact that a const uschar * doesn't automatically cast to
247     a void * provoked a warning.
249     . Turning on some more compiler warnings threw up some "shadow" variables
250     and a few more missing casts.
252     4. If PCRE was complied with UTF-8 support, but called without the PCRE_UTF8
253     option, a class that contained a single character with a value between 128
254     and 255 (e.g. /[\xFF]/) caused PCRE to crash.
256     5. If PCRE was compiled with UTF-8 support, but called without the PCRE_UTF8
257     option, a class that contained several characters, but with at least one
258     whose value was between 128 and 255 caused PCRE to crash.
261 nigel 65 Version 4.1 12-Mar-03
262     ---------------------
263 nigel 63
264 nigel 65 1. Compiling with gcc -pedantic found a couple of places where casts were
265     needed, and a string in dftables.c that was longer than standard compilers are
266     required to support.
268     2. Compiling with Sun's compiler found a few more places where the code could
269     be tidied up in order to avoid warnings.
271     3. The variables for cross-compiling were called HOST_CC and HOST_CFLAGS; the
272     first of these names is deprecated in the latest Autoconf in favour of the name
273     CC_FOR_BUILD, because "host" is typically used to mean the system on which the
274     compiled code will be run. I can't find a reference for HOST_CFLAGS, but by
275     analogy I have changed it to CFLAGS_FOR_BUILD.
277     4. Added -no-undefined to the linking command in the Makefile, because this is
278     apparently helpful for Windows. To make it work, also added "-L. -lpcre" to the
279     linking step for the pcreposix library.
281     5. PCRE was failing to diagnose the case of two named groups with the same
282     name.
284     6. A problem with one of PCRE's optimizations was discovered. PCRE remembers a
285     literal character that is needed in the subject for a match, and scans along to
286     ensure that it is present before embarking on the full matching process. This
287     saves time in cases of nested unlimited repeats that are never going to match.
288     Problem: the scan can take a lot of time if the subject is very long (e.g.
289     megabytes), thus penalizing straightforward matches. It is now done only if the
290     amount of subject to be scanned is less than 1000 bytes.
292     7. A lesser problem with the same optimization is that it was recording the
293     first character of an anchored pattern as "needed", thus provoking a search
294     right along the subject, even when the first match of the pattern was going to
295     fail. The "needed" character is now not set for anchored patterns, unless it
296     follows something in the pattern that is of non-fixed length. Thus, it still
297     fulfils its original purpose of finding quick non-matches in cases of nested
298     unlimited repeats, but isn't used for simple anchored patterns such as /^abc/.
301     Version 4.0 17-Feb-03
302     ---------------------
304 nigel 63 1. If a comment in an extended regex that started immediately after a meta-item
305     extended to the end of string, PCRE compiled incorrect data. This could lead to
306     all kinds of weird effects. Example: /#/ was bad; /()#/ was bad; /a#/ was not.
308     2. Moved to autoconf 2.53 and libtool 1.4.2.
310     3. Perl 5.8 no longer needs "use utf8" for doing UTF-8 things. Consequently,
311     the special perltest8 script is no longer needed - all the tests can be run
312     from a single perltest script.
314     4. From 5.004, Perl has not included the VT character (0x0b) in the set defined
315     by \s. It has now been removed in PCRE. This means it isn't recognized as
316     whitespace in /x regexes too, which is the same as Perl. Note that the POSIX
317     class [:space:] *does* include VT, thereby creating a mess.
319     5. Added the class [:blank:] (a GNU extension from Perl 5.8) to match only
320     space and tab.
322     6. Perl 5.005 was a long time ago. It's time to amalgamate the tests that use
323     its new features into the main test script, reducing the number of scripts.
325     7. Perl 5.8 has changed the meaning of patterns like /a(?i)b/. Earlier versions
326     were backward compatible, and made the (?i) apply to the whole pattern, as if
327     /i were given. Now it behaves more logically, and applies the option setting
328     only to what follows. PCRE has been changed to follow suit. However, if it
329     finds options settings right at the start of the pattern, it extracts them into
330     the global options, as before. Thus, they show up in the info data.
332     8. Added support for the \Q...\E escape sequence. Characters in between are
333     treated as literals. This is slightly different from Perl in that $ and @ are
334     also handled as literals inside the quotes. In Perl, they will cause variable
335     interpolation. Note the following examples:
337     Pattern PCRE matches Perl matches
339     \Qabc$xyz\E abc$xyz abc followed by the contents of $xyz
340     \Qabc\$xyz\E abc\$xyz abc\$xyz
341     \Qabc\E\$\Qxyz\E abc$xyz abc$xyz
343     For compatibility with Perl, \Q...\E sequences are recognized inside character
344     classes as well as outside them.
346     9. Re-organized 3 code statements in pcretest to avoid "overflow in
347     floating-point constant arithmetic" warnings from a Microsoft compiler. Added a
348     (size_t) cast to one statement in pcretest and one in pcreposix to avoid
349     signed/unsigned warnings.
351     10. SunOS4 doesn't have strtoul(). This was used only for unpicking the -o
352     option for pcretest, so I've replaced it by a simple function that does just
353     that job.
355     11. pcregrep was ending with code 0 instead of 2 for the commands "pcregrep" or
356     "pcregrep -".
358     12. Added "possessive quantifiers" ?+, *+, ++, and {,}+ which come from Sun's
359     Java package. This provides some syntactic sugar for simple cases of what my
360     documentation calls "once-only subpatterns". A pattern such as x*+ is the same
361     as (?>x*). In other words, if what is inside (?>...) is just a single repeated
362     item, you can use this simplified notation. Note that only makes sense with
363     greedy quantifiers. Consequently, the use of the possessive quantifier forces
364     greediness, whatever the setting of the PCRE_UNGREEDY option.
366     13. A change of greediness default within a pattern was not taking effect at
367     the current level for patterns like /(b+(?U)a+)/. It did apply to parenthesized
368     subpatterns that followed. Patterns like /b+(?U)a+/ worked because the option
369     was abstracted outside.
371     14. PCRE now supports the \G assertion. It is true when the current matching
372     position is at the start point of the match. This differs from \A when the
373     starting offset is non-zero. Used with the /g option of pcretest (or similar
374     code), it works in the same way as it does for Perl's /g option. If all
375     alternatives of a regex begin with \G, the expression is anchored to the start
376     match position, and the "anchored" flag is set in the compiled expression.
378     15. Some bugs concerning the handling of certain option changes within patterns
379     have been fixed. These applied to options other than (?ims). For example,
380     "a(?x: b c )d" did not match "XabcdY" but did match "Xa b c dY". It should have
381     been the other way round. Some of this was related to change 7 above.
383     16. PCRE now gives errors for /[.x.]/ and /[=x=]/ as unsupported POSIX
384     features, as Perl does. Previously, PCRE gave the warnings only for /[[.x.]]/
385     and /[[=x=]]/. PCRE now also gives an error for /[:name:]/ because it supports
386     POSIX classes only within a class (e.g. /[[:alpha:]]/).
388     17. Added support for Perl's \C escape. This matches one byte, even in UTF8
389     mode. Unlike ".", it always matches newline, whatever the setting of
390     PCRE_DOTALL. However, PCRE does not permit \C to appear in lookbehind
391     assertions. Perl allows it, but it doesn't (in general) work because it can't
392     calculate the length of the lookbehind. At least, that's the case for Perl
393     5.8.0 - I've been told they are going to document that it doesn't work in
394     future.
396     18. Added an error diagnosis for escapes that PCRE does not support: these are
397     \L, \l, \N, \P, \p, \U, \u, and \X.
399     19. Although correctly diagnosing a missing ']' in a character class, PCRE was
400     reading past the end of the pattern in cases such as /[abcd/.
402     20. PCRE was getting more memory than necessary for patterns with classes that
403     contained both POSIX named classes and other characters, e.g. /[[:space:]abc/.
405     21. Added some code, conditional on #ifdef VPCOMPAT, to make life easier for
406     compiling PCRE for use with Virtual Pascal.
408     22. Small fix to the Makefile to make it work properly if the build is done
409     outside the source tree.
411     23. Added a new extension: a condition to go with recursion. If a conditional
412     subpattern starts with (?(R) the "true" branch is used if recursion has
413     happened, whereas the "false" branch is used only at the top level.
415     24. When there was a very long string of literal characters (over 255 bytes
416     without UTF support, over 250 bytes with UTF support), the computation of how
417     much memory was required could be incorrect, leading to segfaults or other
418     strange effects.
420     25. PCRE was incorrectly assuming anchoring (either to start of subject or to
421     start of line for a non-DOTALL pattern) when a pattern started with (.*) and
422     there was a subsequent back reference to those brackets. This meant that, for
423     example, /(.*)\d+\1/ failed to match "abc123bc". Unfortunately, it isn't
424     possible to check for precisely this case. All we can do is abandon the
425     optimization if .* occurs inside capturing brackets when there are any back
426     references whatsoever. (See below for a better fix that came later.)
428     26. The handling of the optimization for finding the first character of a
429     non-anchored pattern, and for finding a character that is required later in the
430     match were failing in some cases. This didn't break the matching; it just
431     failed to optimize when it could. The way this is done has been re-implemented.
433     27. Fixed typo in error message for invalid (?R item (it said "(?p").
435     28. Added a new feature that provides some of the functionality that Perl
436     provides with (?{...}). The facility is termed a "callout". The way it is done
437     in PCRE is for the caller to provide an optional function, by setting
438     pcre_callout to its entry point. Like pcre_malloc and pcre_free, this is a
439     global variable. By default it is unset, which disables all calling out. To get
440     the function called, the regex must include (?C) at appropriate points. This
441     is, in fact, equivalent to (?C0), and any number <= 255 may be given with (?C).
442     This provides a means of identifying different callout points. When PCRE
443     reaches such a point in the regex, if pcre_callout has been set, the external
444     function is called. It is provided with data in a structure called
445     pcre_callout_block, which is defined in pcre.h. If the function returns 0,
446     matching continues; if it returns a non-zero value, the match at the current
447     point fails. However, backtracking will occur if possible. [This was changed
448     later and other features added - see item 49 below.]
450     29. pcretest is upgraded to test the callout functionality. It provides a
451     callout function that displays information. By default, it shows the start of
452     the match and the current position in the text. There are some new data escapes
453     to vary what happens:
455     \C+ in addition, show current contents of captured substrings
456     \C- do not supply a callout function
457     \C!n return 1 when callout number n is reached
458     \C!n!m return 1 when callout number n is reached for the mth time
460     30. If pcregrep was called with the -l option and just a single file name, it
461     output "<stdin>" if a match was found, instead of the file name.
463     31. Improve the efficiency of the POSIX API to PCRE. If the number of capturing
464     slots is less than POSIX_MALLOC_THRESHOLD, use a block on the stack to pass to
465     pcre_exec(). This saves a malloc/free per call. The default value of
466     POSIX_MALLOC_THRESHOLD is 10; it can be changed by --with-posix-malloc-threshold
467     when configuring.
469     32. The default maximum size of a compiled pattern is 64K. There have been a
470     few cases of people hitting this limit. The code now uses macros to handle the
471     storing of links as offsets within the compiled pattern. It defaults to 2-byte
472     links, but this can be changed to 3 or 4 bytes by --with-link-size when
473     configuring. Tests 2 and 5 work only with 2-byte links because they output
474     debugging information about compiled patterns.
476     33. Internal code re-arrangements:
478     (a) Moved the debugging function for printing out a compiled regex into
479     its own source file (printint.c) and used #include to pull it into
480     pcretest.c and, when DEBUG is defined, into pcre.c, instead of having two
481     separate copies.
483     (b) Defined the list of op-code names for debugging as a macro in
484     internal.h so that it is next to the definition of the opcodes.
486     (c) Defined a table of op-code lengths for simpler skipping along compiled
487     code. This is again a macro in internal.h so that it is next to the
488     definition of the opcodes.
490     34. Added support for recursive calls to individual subpatterns, along the
491     lines of Robin Houston's patch (but implemented somewhat differently).
493     35. Further mods to the Makefile to help Win32. Also, added code to pcregrep to
494     allow it to read and process whole directories in Win32. This code was
495     contributed by Lionel Fourquaux; it has not been tested by me.
497     36. Added support for named subpatterns. The Python syntax (?P<name>...) is
498     used to name a group. Names consist of alphanumerics and underscores, and must
499     be unique. Back references use the syntax (?P=name) and recursive calls use
500     (?P>name) which is a PCRE extension to the Python extension. Groups still have
501     numbers. The function pcre_fullinfo() can be used after compilation to extract
502     a name/number map. There are three relevant calls:
504     PCRE_INFO_NAMEENTRYSIZE yields the size of each entry in the map
505     PCRE_INFO_NAMECOUNT yields the number of entries
506     PCRE_INFO_NAMETABLE yields a pointer to the map.
508     The map is a vector of fixed-size entries. The size of each entry depends on
509     the length of the longest name used. The first two bytes of each entry are the
510     group number, most significant byte first. There follows the corresponding
511     name, zero terminated. The names are in alphabetical order.
513     37. Make the maximum literal string in the compiled code 250 for the non-UTF-8
514     case instead of 255. Making it the same both with and without UTF-8 support
515     means that the same test output works with both.
517     38. There was a case of malloc(0) in the POSIX testing code in pcretest. Avoid
518     calling malloc() with a zero argument.
520     39. Change 25 above had to resort to a heavy-handed test for the .* anchoring
521     optimization. I've improved things by keeping a bitmap of backreferences with
522     numbers 1-31 so that if .* occurs inside capturing brackets that are not in
523     fact referenced, the optimization can be applied. It is unlikely that a
524     relevant occurrence of .* (i.e. one which might indicate anchoring or forcing
525     the match to follow \n) will appear inside brackets with a number greater than
526     31, but if it does, any back reference > 31 suppresses the optimization.
528     40. Added a new compile-time option PCRE_NO_AUTO_CAPTURE. This has the effect
529     of disabling numbered capturing parentheses. Any opening parenthesis that is
530     not followed by ? behaves as if it were followed by ?: but named parentheses
531     can still be used for capturing (and they will acquire numbers in the usual
532     way).
534     41. Redesigned the return codes from the match() function into yes/no/error so
535     that errors can be passed back from deep inside the nested calls. A malloc
536     failure while inside a recursive subpattern call now causes the
537     PCRE_ERROR_NOMEMORY return instead of quietly going wrong.
539     42. It is now possible to set a limit on the number of times the match()
540     function is called in a call to pcre_exec(). This facility makes it possible to
541     limit the amount of recursion and backtracking, though not in a directly
542     obvious way, because the match() function is used in a number of different
543     circumstances. The count starts from zero for each position in the subject
544     string (for non-anchored patterns). The default limit is, for compatibility, a
545     large number, namely 10 000 000. You can change this in two ways:
547     (a) When configuring PCRE before making, you can use --with-match-limit=n
548     to set a default value for the compiled library.
550     (b) For each call to pcre_exec(), you can pass a pcre_extra block in which
551     a different value is set. See 45 below.
553     If the limit is exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
555     43. Added a new function pcre_config(int, void *) to enable run-time extraction
556     of things that can be changed at compile time. The first argument specifies
557     what is wanted and the second points to where the information is to be placed.
558     The current list of available information is:
562     The output is an integer that is set to one if UTF-8 support is available;
563     otherwise it is set to zero.
567     The output is an integer that it set to the value of the code that is used for
568     newline. It is either LF (10) or CR (13).
572     The output is an integer that contains the number of bytes used for internal
573     linkage in compiled expressions. The value is 2, 3, or 4. See item 32 above.
577     The output is an integer that contains the threshold above which the POSIX
578     interface uses malloc() for output vectors. See item 31 above.
582     The output is an unsigned integer that contains the default limit of the number
583     of match() calls in a pcre_exec() execution. See 42 above.
585     44. pcretest has been upgraded by the addition of the -C option. This causes it
586     to extract all the available output from the new pcre_config() function, and to
587     output it. The program then exits immediately.
589     45. A need has arisen to pass over additional data with calls to pcre_exec() in
590     order to support additional features. One way would have been to define
591     pcre_exec2() (for example) with extra arguments, but this would not have been
592     extensible, and would also have required all calls to the original function to
593     be mapped to the new one. Instead, I have chosen to extend the mechanism that
594     is used for passing in "extra" data from pcre_study().
596     The pcre_extra structure is now exposed and defined in pcre.h. It currently
597     contains the following fields:
599     flags a bitmap indicating which of the following fields are set
600     study_data opaque data from pcre_study()
601     match_limit a way of specifying a limit on match() calls for a specific
602     call to pcre_exec()
603     callout_data data for callouts (see 49 below)
605     The flag bits are also defined in pcre.h, and are
611     The pcre_study() function now returns one of these new pcre_extra blocks, with
612     the actual study data pointed to by the study_data field, and the
613     PCRE_EXTRA_STUDY_DATA flag set. This can be passed directly to pcre_exec() as
614     before. That is, this change is entirely upwards-compatible and requires no
615     change to existing code.
617     If you want to pass in additional data to pcre_exec(), you can either place it
618     in a pcre_extra block provided by pcre_study(), or create your own pcre_extra
619     block.
621     46. pcretest has been extended to test the PCRE_EXTRA_MATCH_LIMIT feature. If a
622     data string contains the escape sequence \M, pcretest calls pcre_exec() several
623     times with different match limits, until it finds the minimum value needed for
624     pcre_exec() to complete. The value is then output. This can be instructive; for
625     most simple matches the number is quite small, but for pathological cases it
626     gets very large very quickly.
628     47. There's a new option for pcre_fullinfo() called PCRE_INFO_STUDYSIZE. It
629     returns the size of the data block pointed to by the study_data field in a
630     pcre_extra block, that is, the value that was passed as the argument to
631     pcre_malloc() when PCRE was getting memory in which to place the information
632     created by pcre_study(). The fourth argument should point to a size_t variable.
633     pcretest has been extended so that this information is shown after a successful
634     pcre_study() call when information about the compiled regex is being displayed.
636     48. Cosmetic change to Makefile: there's no need to have / after $(DESTDIR)
637     because what follows is always an absolute path. (Later: it turns out that this
638     is more than cosmetic for MinGW, because it doesn't like empty path
639     components.)
641     49. Some changes have been made to the callout feature (see 28 above):
643     (i) A callout function now has three choices for what it returns:
645     0 => success, carry on matching
646     > 0 => failure at this point, but backtrack if possible
647     < 0 => serious error, return this value from pcre_exec()
649     Negative values should normally be chosen from the set of PCRE_ERROR_xxx
650     values. In particular, returning PCRE_ERROR_NOMATCH forces a standard
651     "match failed" error. The error number PCRE_ERROR_CALLOUT is reserved for
652     use by callout functions. It will never be used by PCRE itself.
654     (ii) The pcre_extra structure (see 45 above) has a void * field called
655     callout_data, with corresponding flag bit PCRE_EXTRA_CALLOUT_DATA. The
656     pcre_callout_block structure has a field of the same name. The contents of
657     the field passed in the pcre_extra structure are passed to the callout
658     function in the corresponding field in the callout block. This makes it
659     easier to use the same callout-containing regex from multiple threads. For
660     testing, the pcretest program has a new data escape
662     \C*n pass the number n (may be negative) as callout_data
664     If the callout function in pcretest receives a non-zero value as
665     callout_data, it returns that value.
667     50. Makefile wasn't handling CFLAGS properly when compiling dftables. Also,
668     there were some redundant $(CFLAGS) in commands that are now specified as
669     $(LINK), which already includes $(CFLAGS).
671     51. Extensions to UTF-8 support are listed below. These all apply when (a) PCRE
672     has been compiled with UTF-8 support *and* pcre_compile() has been compiled
673     with the PCRE_UTF8 flag. Patterns that are compiled without that flag assume
674     one-byte characters throughout. Note that case-insensitive matching applies
675     only to characters whose values are less than 256. PCRE doesn't support the
676     notion of cases for higher-valued characters.
678     (i) A character class whose characters are all within 0-255 is handled as
679     a bit map, and the map is inverted for negative classes. Previously, a
680     character > 255 always failed to match such a class; however it should
681     match if the class was a negative one (e.g. [^ab]). This has been fixed.
683     (ii) A negated character class with a single character < 255 is coded as
684     "not this character" (OP_NOT). This wasn't working properly when the test
685     character was multibyte, either singly or repeated.
687     (iii) Repeats of multibyte characters are now handled correctly in UTF-8
688     mode, for example: \x{100}{2,3}.
690     (iv) The character escapes \b, \B, \d, \D, \s, \S, \w, and \W (either
691     singly or repeated) now correctly test multibyte characters. However,
692     PCRE doesn't recognize any characters with values greater than 255 as
693     digits, spaces, or word characters. Such characters always match \D, \S,
694     and \W, and never match \d, \s, or \w.
696     (v) Classes may now contain characters and character ranges with values
697     greater than 255. For example: [ab\x{100}-\x{400}].
699     (vi) pcregrep now has a --utf-8 option (synonym -u) which makes it call
700     PCRE in UTF-8 mode.
702     52. The info request value PCRE_INFO_FIRSTCHAR has been renamed
703     PCRE_INFO_FIRSTBYTE because it is a byte value. However, the old name is
704     retained for backwards compatibility. (Note that LASTLITERAL is also a byte
705     value.)
707     53. The single man page has become too large. I have therefore split it up into
708     a number of separate man pages. These also give rise to individual HTML pages;
709     these are now put in a separate directory, and there is an index.html page that
710     lists them all. Some hyperlinking between the pages has been installed.
712     54. Added convenience functions for handling named capturing parentheses.
714     55. Unknown escapes inside character classes (e.g. [\M]) and escapes that
715     aren't interpreted therein (e.g. [\C]) are literals in Perl. This is now also
716     true in PCRE, except when the PCRE_EXTENDED option is set, in which case they
717     are faulted.
719     56. Introduced HOST_CC and HOST_CFLAGS which can be set in the environment when
720     calling configure. These values are used when compiling the dftables.c program
721     which is run to generate the source of the default character tables. They
722     default to the values of CC and CFLAGS. If you are cross-compiling PCRE,
723     you will need to set these values.
725     57. Updated the building process for Windows DLL, as provided by Fred Cox.
728     Version 3.9 02-Jan-02
729 nigel 61 ---------------------
731     1. A bit of extraneous text had somehow crept into the pcregrep documentation.
733     2. If --disable-static was given, the building process failed when trying to
734     build pcretest and pcregrep. (For some reason it was using libtool to compile
735     them, which is not right, as they aren't part of the library.)
738 nigel 59 Version 3.8 18-Dec-01
739     ---------------------
741     1. The experimental UTF-8 code was completely screwed up. It was packing the
742     bytes in the wrong order. How dumb can you get?
745 nigel 57 Version 3.7 29-Oct-01
746     ---------------------
748     1. In updating pcretest to check change 1 of version 3.6, I screwed up.
749     This caused pcretest, when used on the test data, to segfault. Unfortunately,
750     this didn't happen under Solaris 8, where I normally test things.
752 nigel 59 2. The Makefile had to be changed to make it work on BSD systems, where 'make'
753     doesn't seem to recognize that ./xxx and xxx are the same file. (This entry
754     isn't in ChangeLog distributed with 3.7 because I forgot when I hastily made
755     this fix an hour or so after the initial 3.7 release.)
756 nigel 57
757 nigel 59
758 nigel 55 Version 3.6 23-Oct-01
759     ---------------------
761     1. Crashed with /(sens|respons)e and \1ibility/ and "sense and sensibility" if
762     offsets passed as NULL with zero offset count.
764     2. The config.guess and config.sub files had not been updated when I moved to
765     the latest autoconf.
768 nigel 53 Version 3.5 15-Aug-01
769     ---------------------
770 nigel 5
771 nigel 53 1. Added some missing #if !defined NOPOSIX conditionals in pcretest.c that
772     had been forgotten.
774     2. By using declared but undefined structures, we can avoid using "void"
775     definitions in pcre.h while keeping the internal definitions of the structures
776     private.
778     3. The distribution is now built using autoconf 2.50 and libtool 1.4. From a
779     user point of view, this means that both static and shared libraries are built
780     by default, but this can be individually controlled. More of the work of
781     handling this static/shared cases is now inside libtool instead of PCRE's make
782     file.
784     4. The pcretest utility is now installed along with pcregrep because it is
785     useful for users (to test regexs) and by doing this, it automatically gets
786     relinked by libtool. The documentation has been turned into a man page, so
787     there are now .1, .txt, and .html versions in /doc.
789     5. Upgrades to pcregrep:
790     (i) Added long-form option names like gnu grep.
791     (ii) Added --help to list all options with an explanatory phrase.
792     (iii) Added -r, --recursive to recurse into sub-directories.
793     (iv) Added -f, --file to read patterns from a file.
795     6. pcre_exec() was referring to its "code" argument before testing that
796     argument for NULL (and giving an error if it was NULL).
798     7. Upgraded Makefile.in to allow for compiling in a different directory from
799     the source directory.
801     8. Tiny buglet in pcretest: when pcre_fullinfo() was called to retrieve the
802     options bits, the pointer it was passed was to an int instead of to an unsigned
803     long int. This mattered only on 64-bit systems.
805     9. Fixed typo (3.4/1) in pcre.h again. Sigh. I had changed pcre.h (which is
806     generated) instead of pcre.in, which it its source. Also made the same change
807     in several of the .c files.
809     10. A new release of gcc defines printf() as a macro, which broke pcretest
810     because it had an ifdef in the middle of a string argument for printf(). Fixed
811     by using separate calls to printf().
813     11. Added --enable-newline-is-cr and --enable-newline-is-lf to the configure
814     script, to force use of CR or LF instead of \n in the source. On non-Unix
815     systems, the value can be set in config.h.
817     12. The limit of 200 on non-capturing parentheses is a _nesting_ limit, not an
818     absolute limit. Changed the text of the error message to make this clear, and
819     likewise updated the man page.
821     13. The limit of 99 on the number of capturing subpatterns has been removed.
822     The new limit is 65535, which I hope will not be a "real" limit.
825 nigel 51 Version 3.4 22-Aug-00
826     ---------------------
828     1. Fixed typo in pcre.h: unsigned const char * changed to const unsigned char *.
830     2. Diagnose condition (?(0) as an error instead of crashing on matching.
833 nigel 49 Version 3.3 01-Aug-00
834     ---------------------
836     1. If an octal character was given, but the value was greater than \377, it
837     was not getting masked to the least significant bits, as documented. This could
838     lead to crashes in some systems.
840     2. Perl 5.6 (if not earlier versions) accepts classes like [a-\d] and treats
841     the hyphen as a literal. PCRE used to give an error; it now behaves like Perl.
843     3. Added the functions pcre_free_substring() and pcre_free_substring_list().
844     These just pass their arguments on to (pcre_free)(), but they are provided
845     because some uses of PCRE bind it to non-C systems that can call its functions,
846     but cannot call free() or pcre_free() directly.
848     4. Add "make test" as a synonym for "make check". Corrected some comments in
849     the Makefile.
851     5. Add $(DESTDIR)/ in front of all the paths in the "install" target in the
852     Makefile.
854     6. Changed the name of pgrep to pcregrep, because Solaris has introduced a
855     command called pgrep for grepping around the active processes.
857     7. Added the beginnings of support for UTF-8 character strings.
859     8. Arranged for the Makefile to pass over the settings of CC, CFLAGS, and
860     RANLIB to ./ltconfig so that they are used by libtool. I think these are all
861     the relevant ones. (AR is not passed because ./ltconfig does its own figuring
862     out for the ar command.)
865 nigel 47 Version 3.2 12-May-00
866     ---------------------
868     This is purely a bug fixing release.
870     1. If the pattern /((Z)+|A)*/ was matched agained ZABCDEFG it matched Z instead
871     of ZA. This was just one example of several cases that could provoke this bug,
872     which was introduced by change 9 of version 2.00. The code for breaking
873     infinite loops after an iteration that matches an empty string was't working
874     correctly.
876     2. The pcretest program was not imitating Perl correctly for the pattern /a*/g
877     when matched against abbab (for example). After matching an empty string, it
878     wasn't forcing anchoring when setting PCRE_NOTEMPTY for the next attempt; this
879     caused it to match further down the string than it should.
881     3. The code contained an inclusion of sys/types.h. It isn't clear why this
882     was there because it doesn't seem to be needed, and it causes trouble on some
883     systems, as it is not a Standard C header. It has been removed.
885     4. Made 4 silly changes to the source to avoid stupid compiler warnings that
886     were reported on the Macintosh. The changes were from
888     while ((c = *(++ptr)) != 0 && c != '\n');
889     to
890     while ((c = *(++ptr)) != 0 && c != '\n') ;
892     Totally extraordinary, but if that's what it takes...
894     5. PCRE is being used in one environment where neither memmove() nor bcopy() is
895     available. Added HAVE_BCOPY and an autoconf test for it; if neither
896     HAVE_MEMMOVE nor HAVE_BCOPY is set, use a built-in emulation function which
897     assumes the way PCRE uses memmove() (always moving upwards).
899     6. PCRE is being used in one environment where strchr() is not available. There
900     was only one use in pcre.c, and writing it out to avoid strchr() probably gives
901     faster code anyway.
904 nigel 45 Version 3.1 09-Feb-00
905     ---------------------
907     The only change in this release is the fixing of some bugs in Makefile.in for
908     the "install" target:
910     (1) It was failing to install pcreposix.h.
912     (2) It was overwriting the pcre.3 man page with the pcreposix.3 man page.
915 nigel 43 Version 3.0 01-Feb-00
916     ---------------------
917 nigel 41
918     1. Add support for the /+ modifier to perltest (to output $` like it does in
919     pcretest).
921     2. Add support for the /g modifier to perltest.
923     3. Fix pcretest so that it behaves even more like Perl for /g when the pattern
924     matches null strings.
926     4. Fix perltest so that it doesn't do unwanted things when fed an empty
927     pattern. Perl treats empty patterns specially - it reuses the most recent
928     pattern, which is not what we want. Replace // by /(?#)/ in order to avoid this
929     effect.
931     5. The POSIX interface was broken in that it was just handing over the POSIX
932     captured string vector to pcre_exec(), but (since release 2.00) PCRE has
933     required a bigger vector, with some working space on the end. This means that
934     the POSIX wrapper now has to get and free some memory, and copy the results.
936 nigel 43 6. Added some simple autoconf support, placing the test data and the
937     documentation in separate directories, re-organizing some of the
938     information files, and making it build pcre-config (a GNU standard). Also added
939     libtool support for building PCRE as a shared library, which is now the
940     default.
941 nigel 41
942 nigel 43 7. Got rid of the leading zero in the definition of PCRE_MINOR because 08 and
943     09 are not valid octal constants. Single digits will be used for minor values
944     less than 10.
946     8. Defined REG_EXTENDED and REG_NOSUB as zero in the POSIX header, so that
947     existing programs that set these in the POSIX interface can use PCRE without
948     modification.
950     9. Added a new function, pcre_fullinfo() with an extensible interface. It can
951     return all that pcre_info() returns, plus additional data. The pcre_info()
952     function is retained for compatibility, but is considered to be obsolete.
954     10. Added experimental recursion feature (?R) to handle one common case that
955     Perl 5.6 will be able to do with (?p{...}).
957     11. Added support for POSIX character classes like [:alpha:], which Perl is
958     adopting.
961 nigel 39 Version 2.08 31-Aug-99
962     ----------------------
964     1. When startoffset was not zero and the pattern began with ".*", PCRE was not
965     trying to match at the startoffset position, but instead was moving forward to
966     the next newline as if a previous match had failed.
968     2. pcretest was not making use of PCRE_NOTEMPTY when repeating for /g and /G,
969     and could get into a loop if a null string was matched other than at the start
970     of the subject.
972     3. Added definitions of PCRE_MAJOR and PCRE_MINOR to pcre.h so the version can
973     be distinguished at compile time, and for completeness also added PCRE_DATE.
975     5. Added Paul Sokolovsky's minor changes to make it easy to compile a Win32 DLL
976     in GnuWin32 environments.
979 nigel 37 Version 2.07 29-Jul-99
980     ----------------------
982     1. The documentation is now supplied in plain text form and HTML as well as in
983     the form of man page sources.
985     2. C++ compilers don't like assigning (void *) values to other pointer types.
986     In particular this affects malloc(). Although there is no problem in Standard
987     C, I've put in casts to keep C++ compilers happy.
989     3. Typo on pcretest.c; a cast of (unsigned char *) in the POSIX regexec() call
990     should be (const char *).
992     4. If NOPOSIX is defined, pcretest.c compiles without POSIX support. This may
993     be useful for non-Unix systems who don't want to bother with the POSIX stuff.
994     However, I haven't made this a standard facility. The documentation doesn't
995     mention it, and the Makefile doesn't support it.
997     5. The Makefile now contains an "install" target, with editable destinations at
998     the top of the file. The pcretest program is not installed.
1000     6. pgrep -V now gives the PCRE version number and date.
1002     7. Fixed bug: a zero repetition after a literal string (e.g. /abcde{0}/) was
1003     causing the entire string to be ignored, instead of just the last character.
1005     8. If a pattern like /"([^\\"]+|\\.)*"/ is applied in the normal way to a
1006     non-matching string, it can take a very, very long time, even for strings of
1007     quite modest length, because of the nested recursion. PCRE now does better in
1008     some of these cases. It does this by remembering the last required literal
1009     character in the pattern, and pre-searching the subject to ensure it is present
1010     before running the real match. In other words, it applies a heuristic to detect
1011     some types of certain failure quickly, and in the above example, if presented
1012     with a string that has no trailing " it gives "no match" very quickly.
1014     9. A new runtime option PCRE_NOTEMPTY causes null string matches to be ignored;
1015     other alternatives are tried instead.
1018 nigel 35 Version 2.06 09-Jun-99
1019     ----------------------
1021     1. Change pcretest's output for amount of store used to show just the code
1022     space, because the remainder (the data block) varies in size between 32-bit and
1023     64-bit systems.
1025     2. Added an extra argument to pcre_exec() to supply an offset in the subject to
1026     start matching at. This allows lookbehinds to work when searching for multiple
1027     occurrences in a string.
1029     3. Added additional options to pcretest for testing multiple occurrences:
1031     /+ outputs the rest of the string that follows a match
1032     /g loops for multiple occurrences, using the new startoffset argument
1033     /G loops for multiple occurrences by passing an incremented pointer
1035     4. PCRE wasn't doing the "first character" optimization for patterns starting
1036     with \b or \B, though it was doing it for other lookbehind assertions. That is,
1037     it wasn't noticing that a match for a pattern such as /\bxyz/ has to start with
1038     the letter 'x'. On long subject strings, this gives a significant speed-up.
1041 nigel 33 Version 2.05 21-Apr-99
1042     ----------------------
1044     1. Changed the type of magic_number from int to long int so that it works
1045     properly on 16-bit systems.
1047     2. Fixed a bug which caused patterns starting with .* not to work correctly
1048     when the subject string contained newline characters. PCRE was assuming
1049     anchoring for such patterns in all cases, which is not correct because .* will
1050     not pass a newline unless PCRE_DOTALL is set. It now assumes anchoring only if
1051     DOTALL is set at top level; otherwise it knows that patterns starting with .*
1052     must be retried after every newline in the subject.
1055 nigel 31 Version 2.04 18-Feb-99
1056     ----------------------
1058     1. For parenthesized subpatterns with repeats whose minimum was zero, the
1059     computation of the store needed to hold the pattern was incorrect (too large).
1060     If such patterns were nested a few deep, this could multiply and become a real
1061     problem.
1063     2. Added /M option to pcretest to show the memory requirement of a specific
1064     pattern. Made -m a synonym of -s (which does this globally) for compatibility.
1066     3. Subpatterns of the form (regex){n,m} (i.e. limited maximum) were being
1067     compiled in such a way that the backtracking after subsequent failure was
1068     pessimal. Something like (a){0,3} was compiled as (a)?(a)?(a)? instead of
1069     ((a)((a)(a)?)?)? with disastrous performance if the maximum was of any size.
1072 nigel 29 Version 2.03 02-Feb-99
1073     ----------------------
1075     1. Fixed typo and small mistake in man page.
1077 nigel 31 2. Added 4th condition (GPL supersedes if conflict) and created separate
1078     LICENCE file containing the conditions.
1079 nigel 29
1080     3. Updated pcretest so that patterns such as /abc\/def/ work like they do in
1081     Perl, that is the internal \ allows the delimiter to be included in the
1082     pattern. Locked out the use of \ as a delimiter. If \ immediately follows
1083     the final delimiter, add \ to the end of the pattern (to test the error).
1085     4. Added the convenience functions for extracting substrings after a successful
1086     match. Updated pcretest to make it able to test these functions.
1089 nigel 27 Version 2.02 14-Jan-99
1090     ----------------------
1092     1. Initialized the working variables associated with each extraction so that
1093     their saving and restoring doesn't refer to uninitialized store.
1095     2. Put dummy code into study.c in order to trick the optimizer of the IBM C
1096     compiler for OS/2 into generating correct code. Apparently IBM isn't going to
1097     fix the problem.
1099     3. Pcretest: the timing code wasn't using LOOPREPEAT for timing execution
1100     calls, and wasn't printing the correct value for compiling calls. Increased the
1101     default value of LOOPREPEAT, and the number of significant figures in the
1102     times.
1104     4. Changed "/bin/rm" in the Makefile to "-rm" so it works on Windows NT.
1106     5. Renamed "deftables" as "dftables" to get it down to 8 characters, to avoid
1107     a building problem on Windows NT with a FAT file system.
1110 nigel 25 Version 2.01 21-Oct-98
1111     ----------------------
1113     1. Changed the API for pcre_compile() to allow for the provision of a pointer
1114     to character tables built by pcre_maketables() in the current locale. If NULL
1115     is passed, the default tables are used.
1118 nigel 23 Version 2.00 24-Sep-98
1119 nigel 21 ----------------------
1121 nigel 23 1. Since the (>?) facility is in Perl 5.005, don't require PCRE_EXTRA to enable
1122     it any more.
1124     2. Allow quantification of (?>) groups, and make it work correctly.
1126     3. The first character computation wasn't working for (?>) groups.
1128     4. Correct the implementation of \Z (it is permitted to match on the \n at the
1129     end of the subject) and add 5.005's \z, which really does match only at the
1130     very end of the subject.
1132     5. Remove the \X "cut" facility; Perl doesn't have it, and (?> is neater.
1134     6. Remove the ability to specify CASELESS, MULTILINE, DOTALL, and
1135     DOLLAR_END_ONLY at runtime, to make it possible to implement the Perl 5.005
1136     localized options. All options to pcre_study() were also removed.
1138     7. Add other new features from 5.005:
1140     $(?<= positive lookbehind
1141     $(?<! negative lookbehind
1142     (?imsx-imsx) added the unsetting capability
1143     such a setting is global if at outer level; local otherwise
1144     (?imsx-imsx:) non-capturing groups with option setting
1145     (?(cond)re|re) conditional pattern matching
1147     A backreference to itself in a repeated group matches the previous
1148     captured string.
1150     8. General tidying up of studying (both automatic and via "study")
1151     consequential on the addition of new assertions.
1153     9. As in 5.005, unlimited repeated groups that could match an empty substring
1154     are no longer faulted at compile time. Instead, the loop is forcibly broken at
1155     runtime if any iteration does actually match an empty substring.
1157     10. Include the RunTest script in the distribution.
1159     11. Added tests from the Perl 5.005_02 distribution. This showed up a few
1160     discrepancies, some of which were old and were also with respect to 5.004. They
1161     have now been fixed.
1164     Version 1.09 28-Apr-98
1165     ----------------------
1167 nigel 21 1. A negated single character class followed by a quantifier with a minimum
1168     value of one (e.g. [^x]{1,6} ) was not compiled correctly. This could lead to
1169     program crashes, or just wrong answers. This did not apply to negated classes
1170     containing more than one character, or to minima other than one.
1173 nigel 19 Version 1.08 27-Mar-98
1174     ----------------------
1176     1. Add PCRE_UNGREEDY to invert the greediness of quantifiers.
1178     2. Add (?U) and (?X) to set PCRE_UNGREEDY and PCRE_EXTRA respectively. The
1179     latter must appear before anything that relies on it in the pattern.
1182 nigel 17 Version 1.07 16-Feb-98
1183     ----------------------
1185     1. A pattern such as /((a)*)*/ was not being diagnosed as in error (unlimited
1186     repeat of a potentially empty string).
1189 nigel 15 Version 1.06 23-Jan-98
1190     ----------------------
1192     1. Added Markus Oberhumer's little patches for C++.
1194     2. Literal strings longer than 255 characters were broken.
1197 nigel 13 Version 1.05 23-Dec-97
1198     ----------------------
1200     1. Negated character classes containing more than one character were failing if
1201     PCRE_CASELESS was set at run time.
1204 nigel 11 Version 1.04 19-Dec-97
1205     ----------------------
1207     1. Corrected the man page, where some "const" qualifiers had been omitted.
1209     2. Made debugging output print "{0,xxx}" instead of just "{,xxx}" to agree with
1210     input syntax.
1212     3. Fixed memory leak which occurred when a regex with back references was
1213     matched with an offsets vector that wasn't big enough. The temporary memory
1214     that is used in this case wasn't being freed if the match failed.
1216     4. Tidied pcretest to ensure it frees memory that it gets.
1218     5. Temporary memory was being obtained in the case where the passed offsets
1219     vector was exactly big enough.
1221     6. Corrected definition of offsetof() from change 5 below.
1223     7. I had screwed up change 6 below and broken the rules for the use of
1224     setjmp(). Now fixed.
1227 nigel 9 Version 1.03 18-Dec-97
1228     ----------------------
1230     1. A erroneous regex with a missing opening parenthesis was correctly
1231     diagnosed, but PCRE attempted to access brastack[-1], which could cause crashes
1232     on some systems.
1234     2. Replaced offsetof(real_pcre, code) by offsetof(real_pcre, code[0]) because
1235     it was reported that one broken compiler failed on the former because "code" is
1236     also an independent variable.
1238     3. The erroneous regex a[]b caused an array overrun reference.
1240     4. A regex ending with a one-character negative class (e.g. /[^k]$/) did not
1241     fail on data ending with that character. (It was going on too far, and checking
1242     the next character, typically a binary zero.) This was specific to the
1243     optimized code for single-character negative classes.
1245     5. Added a contributed patch from the TIN world which does the following:
1247     + Add an undef for memmove, in case the the system defines a macro for it.
1249     + Add a definition of offsetof(), in case there isn't one. (I don't know
1250     the reason behind this - offsetof() is part of the ANSI standard - but
1251     it does no harm).
1253     + Reduce the ifdef's in pcre.c using macro DPRINTF, thereby eliminating
1254     most of the places where whitespace preceded '#'. I have given up and
1255     allowed the remaining 2 cases to be at the margin.
1257     + Rename some variables in pcre to eliminate shadowing. This seems very
1258     pedantic, but does no harm, of course.
1260     6. Moved the call to setjmp() into its own function, to get rid of warnings
1261     from gcc -Wall, and avoided calling it at all unless PCRE_EXTRA is used.
1263     7. Constructs such as \d{8,} were compiling into the equivalent of
1264 nigel 11 \d{8}\d{0,65527} instead of \d{8}\d* which didn't make much difference to the
1265 nigel 9 outcome, but in this particular case used more store than had been allocated,
1266     which caused the bug to be discovered because it threw up an internal error.
1268     8. The debugging code in both pcre and pcretest for outputting the compiled
1269     form of a regex was going wrong in the case of back references followed by
1270     curly-bracketed repeats.
1273 nigel 7 Version 1.02 12-Dec-97
1274     ----------------------
1276     1. Typos in pcre.3 and comments in the source fixed.
1278     2. Applied a contributed patch to get rid of places where it used to remove
1279     'const' from variables, and fixed some signed/unsigned and uninitialized
1280     variable warnings.
1282     3. Added the "runtest" target to Makefile.
1284     4. Set default compiler flag to -O2 rather than just -O.
1287 nigel 5 Version 1.01 19-Nov-97
1288     ----------------------
1290     1. PCRE was failing to diagnose unlimited repeat of empty string for patterns
1291     like /([ab]*)*/, that is, for classes with more than one character in them.
1293     2. Likewise, it wasn't diagnosing patterns with "once-only" subpatterns, such
1294     as /((?>a*))*/ (a PCRE_EXTRA facility).
1297     Version 1.00 18-Nov-97
1298     ----------------------
1300     1. Added compile-time macros to support systems such as SunOS4 which don't have
1301     memmove() or strerror() but have other things that can be used instead.
1303     2. Arranged that "make clean" removes the executables.
1306 nigel 3 Version 0.99 27-Oct-97
1307     ----------------------
1309     1. Fixed bug in code for optimizing classes with only one character. It was
1310     initializing a 32-byte map regardless, which could cause it to run off the end
1311     of the memory it had got.
1313     2. Added, conditional on PCRE_EXTRA, the proposed (?>REGEX) construction.
1316     Version 0.98 22-Oct-97
1317     ----------------------
1319     1. Fixed bug in code for handling temporary memory usage when there are more
1320     back references than supplied space in the ovector. This could cause segfaults.
1323     Version 0.97 21-Oct-97
1324     ----------------------
1326     1. Added the \X "cut" facility, conditional on PCRE_EXTRA.
1328     2. Optimized negated single characters not to use a bit map.
1330     3. Brought error texts together as macro definitions; clarified some of them;
1331     fixed one that was wrong - it said "range out of order" when it meant "invalid
1332     escape sequence".
1334     4. Changed some char * arguments to const char *.
1336     5. Added PCRE_NOTBOL and PCRE_NOTEOL (from POSIX).
1338     6. Added the POSIX-style API wrapper in pcreposix.a and testing facilities in
1339     pcretest.
1342     Version 0.96 16-Oct-97
1343     ----------------------
1345     1. Added a simple "pgrep" utility to the distribution.
1347     2. Fixed an incompatibility with Perl: "{" is now treated as a normal character
1348     unless it appears in one of the precise forms "{ddd}", "{ddd,}", or "{ddd,ddd}"
1349     where "ddd" means "one or more decimal digits".
1351     3. Fixed serious bug. If a pattern had a back reference, but the call to
1352     pcre_exec() didn't supply a large enough ovector to record the related
1353     identifying subpattern, the match always failed. PCRE now remembers the number
1354     of the largest back reference, and gets some temporary memory in which to save
1355     the offsets during matching if necessary, in order to ensure that
1356     backreferences always work.
1358     4. Increased the compatibility with Perl in a number of ways:
1360     (a) . no longer matches \n by default; an option PCRE_DOTALL is provided
1361     to request this handling. The option can be set at compile or exec time.
1363     (b) $ matches before a terminating newline by default; an option
1364     PCRE_DOLLAR_ENDONLY is provided to override this (but not in multiline
1365     mode). The option can be set at compile or exec time.
1367     (c) The handling of \ followed by a digit other than 0 is now supposed to be
1368     the same as Perl's. If the decimal number it represents is less than 10
1369     or there aren't that many previous left capturing parentheses, an octal
1370     escape is read. Inside a character class, it's always an octal escape,
1371     even if it is a single digit.
1373     (d) An escaped but undefined alphabetic character is taken as a literal,
1374     unless PCRE_EXTRA is set. Currently this just reserves the remaining
1375     escapes.
1377     (e) {0} is now permitted. (The previous item is removed from the compiled
1378     pattern).
1380     5. Changed all the names of code files so that the basic parts are no longer
1381     than 10 characters, and abolished the teeny "globals.c" file.
1383     6. Changed the handling of character classes; they are now done with a 32-byte
1384     bit map always.
1386     7. Added the -d and /D options to pcretest to make it possible to look at the
1387     internals of compilation without having to recompile pcre.
1390     Version 0.95 23-Sep-97
1391     ----------------------
1393     1. Fixed bug in pre-pass concerning escaped "normal" characters such as \x5c or
1394     \x20 at the start of a run of normal characters. These were being treated as
1395     real characters, instead of the source characters being re-checked.
1398     Version 0.94 18-Sep-97
1399     ----------------------
1401     1. The functions are now thread-safe, with the caveat that the global variables
1402     containing pointers to malloc() and free() or alternative functions are the
1403     same for all threads.
1405     2. Get pcre_study() to generate a bitmap of initial characters for non-
1406     anchored patterns when this is possible, and use it if passed to pcre_exec().
1409     Version 0.93 15-Sep-97
1410     ----------------------
1412     1. /(b)|(:+)/ was computing an incorrect first character.
1414     2. Add pcre_study() to the API and the passing of pcre_extra to pcre_exec(),
1415     but not actually doing anything yet.
1417     3. Treat "-" characters in classes that cannot be part of ranges as literals,
1418     as Perl does (e.g. [-az] or [az-]).
1420     4. Set the anchored flag if a branch starts with .* or .*? because that tests
1421     all possible positions.
1423     5. Split up into different modules to avoid including unneeded functions in a
1424     compiled binary. However, compile and exec are still in one module. The "study"
1425     function is split off.
1427     6. The character tables are now in a separate module whose source is generated
1428     by an auxiliary program - but can then be edited by hand if required. There are
1429     now no calls to isalnum(), isspace(), isdigit(), isxdigit(), tolower() or
1430     toupper() in the code.
1432     7. Turn the malloc/free funtions variables into pcre_malloc and pcre_free and
1433     make them global. Abolish the function for setting them, as the caller can now
1434     set them directly.
1437     Version 0.92 11-Sep-97
1438     ----------------------
1440     1. A repeat with a fixed maximum and a minimum of 1 for an ordinary character
1441     (e.g. /a{1,3}/) was broken (I mis-optimized it).
1443     2. Caseless matching was not working in character classes if the characters in
1444     the pattern were in upper case.
1446     3. Make ranges like [W-c] work in the same way as Perl for caseless matching.
1448     4. Make PCRE_ANCHORED public and accept as a compile option.
1450     5. Add an options word to pcre_exec() and accept PCRE_ANCHORED and
1451     PCRE_CASELESS at run time. Add escapes \A and \I to pcretest to cause it to
1452     pass them.
1454     6. Give an error if bad option bits passed at compile or run time.
1456     7. Add PCRE_MULTILINE at compile and exec time, and (?m) as well. Add \M to
1457     pcretest to cause it to pass that flag.
1459     8. Add pcre_info(), to get the number of identifying subpatterns, the stored
1460     options, and the first character, if set.
1462     9. Recognize C+ or C{n,m} where n >= 1 as providing a fixed starting character.
1465     Version 0.91 10-Sep-97
1466     ----------------------
1468     1. PCRE was failing to diagnose unlimited repeats of subpatterns that could
1469     match the empty string as in /(a*)*/. It was looping and ultimately crashing.
1471     2. PCRE was looping on encountering an indefinitely repeated back reference to
1472     a subpattern that had matched an empty string, e.g. /(a|)\1*/. It now does what
1473     Perl does - treats the match as successful.
1475     ****

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