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-revision 87 by nigel,
Sat Feb 24 21:41:21 2007 UTC
+revision 255 by ph10,
Wed Sep 19 08:50:04 2007 UTC
 Line 1
  ChangeLog for PCRE
  ------------------
+ Version 7.4 10-Sep-07
+ ---------------------
+.  Change 7.3/28 was implemented for classes by looking at the bitmap. This
+     means that a class such as [\s] counted as "explicit reference to CR or
+     LF". That isn't really right - the whole point of the change was to try to
+     help when there was an actual mention of one of the two characters. So now
+     the change happens only if \r or \n (or a literal CR or LF) character is
+     encountered.
+.  The 32-bit options word was also used for 6 internal flags, but the numbers
+     of both had grown to the point where there were only 3 bits left.
+     Fortunately, there was spare space in the data structure, and so I have
+     moved the internal flags into a new 16-bit field to free up more option
+     bits.
+.  The appearance of (?J) at the start of a pattern set the DUPNAMES option,
+     but did not set the internal JCHANGED flag - either of these is enough to
+     control the way the "get" function works - but the PCRE_INFO_JCHANGED
+     facility is supposed to tell if (?J) was ever used, so now (?J) at the
+     start sets both bits.
+.  Added options (at build time, compile time, exec time) to change \R from
+     matching any Unicode line ending sequence to just matching CR, LF, or CRLF.
+.  doc/pcresyntax.html was missing from the distribution.
+.  Put back the definition of PCRE_ERROR_NULLWSLIMIT, for backward
+     compatibility, even though it is no longer used.
+.  Added macro for snprintf to pcrecpp_unittest.cc and also for strtoll and
+     strtoull to pcrecpp.cc to select the available functions in WIN32 when the
+     windows.h file is present (where different names are used).
+.  Changed all #include <config.h> to #include "config.h". There were also
+     some further <pcre.h> cases that I changed to "pcre.h".
+.  When pcregrep was used with the --colour option, it missed the line ending
+     sequence off the lines that it output.
+. It was pointed out to me that arrays of string pointers cause lots of
+     relocations when a shared library is dynamically loaded. A technique of
+     using a single long string with a table of offsets can drastically reduce
+     these. I have refactored PCRE in four places to do this. The result is
+     dramatic:
+       Originally:                          290
+       After changing UCP table:            187
+       After changing error message table:   43
+       After changing table of "verbs"       36
+       After changing table of Posix names   22
+     Thanks to the folks working on Gregex for glib for this insight.
+. --disable-stack-for-recursion caused compiling to fail unless -enable-
+     unicode-properties was also set.
+. Updated the tests so that they work when \R is defaulted to ANYCRLF.
+. Added checks for ANY and ANYCRLF to pcrecpp.cc where it previously
+     checked only for CRLF.
+. Added casts to pcretest.c to avoid compiler warnings.
+ Version 7.3 28-Aug-07
+ ---------------------
+. In the rejigging of the build system that eventually resulted in 7.1, the
+     line "#include <pcre.h>" was included in pcre_internal.h. The use of angle
+     brackets there is not right, since it causes compilers to look for an
+     installed pcre.h, not the version that is in the source that is being
+     compiled (which of course may be different). I have changed it back to:
+       #include "pcre.h"
+     I have a vague recollection that the change was concerned with compiling in
+     different directories, but in the new build system, that is taken care of
+     by the VPATH setting the Makefile.
+. The pattern .*$ when run in not-DOTALL UTF-8 mode with newline=any failed
+     when the subject happened to end in the byte 0x85 (e.g. if the last
+     character was \x{1ec5}). *Character* 0x85 is one of the "any" newline
+     characters but of course it shouldn't be taken as a newline when it is part
+     of another character. The bug was that, for an unlimited repeat of . in
+     not-DOTALL UTF-8 mode, PCRE was advancing by bytes rather than by
+     characters when looking for a newline.
+. A small performance improvement in the DOTALL UTF-8 mode .* case.
+. Debugging: adjusted the names of opcodes for different kinds of parentheses
+     in debug output.
+. Arrange to use "%I64d" instead of "%lld" and "%I64u" instead of "%llu" for
+     long printing in the pcrecpp unittest when running under MinGW.
+. ESC_K was left out of the EBCDIC table.
+. Change 7.0/38 introduced a new limit on the number of nested non-capturing
+     parentheses; I made it 1000, which seemed large enough. Unfortunately, the
+     limit also applies to "virtual nesting" when a pattern is recursive, and in
+     this case 1000 isn't so big. I have been able to remove this limit at the
+     expense of backing off one optimization in certain circumstances. Normally,
+     when pcre_exec() would call its internal match() function recursively and
+     immediately return the result unconditionally, it uses a "tail recursion"
+     feature to save stack. However, when a subpattern that can match an empty
+     string has an unlimited repetition quantifier, it no longer makes this
+     optimization. That gives it a stack frame in which to save the data for
+     checking that an empty string has been matched. Previously this was taken
+     from the 1000-entry workspace that had been reserved. So now there is no
+     explicit limit, but more stack is used.
+. Applied Daniel's patches to solve problems with the import/export magic
+     syntax that is required for Windows, and which was going wrong for the
+     pcreposix and pcrecpp parts of the library. These were overlooked when this
+     problem was solved for the main library.
+. There were some crude static tests to avoid integer overflow when computing
+     the size of patterns that contain repeated groups with explicit upper
+     limits. As the maximum quantifier is 65535, the maximum group length was
+     set at 30,000 so that the product of these two numbers did not overflow a
+-bit integer. However, it turns out that people want to use groups that
+     are longer than 30,000 bytes (though not repeat them that many times).
+     Change 7.0/17 (the refactoring of the way the pattern size is computed) has
+     made it possible to implement the integer overflow checks in a much more
+     dynamic way, which I have now done. The artificial limitation on group
+     length has been removed - we now have only the limit on the total length of
+     the compiled pattern, which depends on the LINK_SIZE setting.
+. Fixed a bug in the documentation for get/copy named substring when
+     duplicate names are permitted. If none of the named substrings are set, the
+     functions return PCRE_ERROR_NOSUBSTRING (7); the doc said they returned an
+     empty string.
+. Because Perl interprets \Q...\E at a high level, and ignores orphan \E
+     instances, patterns such as [\Q\E] or [\E] or even [^\E] cause an error,
+     because the ] is interpreted as the first data character and the
+     terminating ] is not found. PCRE has been made compatible with Perl in this
+     regard. Previously, it interpreted [\Q\E] as an empty class, and [\E] could
+     cause memory overwriting.
+. Like Perl, PCRE automatically breaks an unlimited repeat after an empty
+     string has been matched (to stop an infinite loop). It was not recognizing
+     a conditional subpattern that could match an empty string if that
+     subpattern was within another subpattern. For example, it looped when
+     trying to match  (((?(1)X|))*)  but it was OK with  ((?(1)X|)*)  where the
+     condition was not nested. This bug has been fixed.
+. A pattern like \X?\d or \P{L}?\d in non-UTF-8 mode could cause a backtrack
+     past the start of the subject in the presence of bytes with the top bit
+     set, for example "\x8aBCD".
+. Added Perl 5.10 experimental backtracking controls (*FAIL), (*F), (*PRUNE),
+     (*SKIP), (*THEN), (*COMMIT), and (*ACCEPT).
+. Optimized (?!) to (*FAIL).
+. Updated the test for a valid UTF-8 string to conform to the later RFC 3629.
+     This restricts code points to be within the range 0 to 0x10FFFF, excluding
+     the "low surrogate" sequence 0xD800 to 0xDFFF. Previously, PCRE allowed the
+     full range 0 to 0x7FFFFFFF, as defined by RFC 2279. Internally, it still
+     does: it's just the validity check that is more restrictive.
+. Inserted checks for integer overflows during escape sequence (backslash)
+     processing, and also fixed erroneous offset values for syntax errors during
+     backslash processing.
+. Fixed another case of looking too far back in non-UTF-8 mode (cf 12 above)
+     for patterns like [\PPP\x8a]{1,}\x80 with the subject "A\x80".
+. An unterminated class in a pattern like (?1)\c[ with a "forward reference"
+     caused an overrun.
+. A pattern like (?:[\PPa*]*){8,} which had an "extended class" (one with
+     something other than just ASCII characters) inside a group that had an
+     unlimited repeat caused a loop at compile time (while checking to see
+     whether the group could match an empty string).
+. Debugging a pattern containing \p or \P could cause a crash. For example,
+     [\P{Any}] did so. (Error in the code for printing property names.)
+. An orphan \E inside a character class could cause a crash.
+. A repeated capturing bracket such as (A)? could cause a wild memory
+     reference during compilation.
+. There are several functions in pcre_compile() that scan along a compiled
+     expression for various reasons (e.g. to see if it's fixed length for look
+     behind). There were bugs in these functions when a repeated \p or \P was
+     present in the pattern. These operators have additional parameters compared
+     with \d, etc, and these were not being taken into account when moving along
+     the compiled data. Specifically:
+     (a) A item such as \p{Yi}{3} in a lookbehind was not treated as fixed
+         length.
+     (b) An item such as \pL+ within a repeated group could cause crashes or
+         loops.
+     (c) A pattern such as \p{Yi}+(\P{Yi}+)(?1) could give an incorrect
+         "reference to non-existent subpattern" error.
+     (d) A pattern like (\P{Yi}{2}\277)? could loop at compile time.
+. A repeated \S or \W in UTF-8 mode could give wrong answers when multibyte
+     characters were involved (for example /\S{2}/8g with "A\x{a3}BC").
+. Using pcregrep in multiline, inverted mode (-Mv) caused it to loop.
+. Patterns such as [\P{Yi}A] which include \p or \P and just one other
+     character were causing crashes (broken optimization).
+. Patterns such as (\P{Yi}*\277)* (group with possible zero repeat containing
+     \p or \P) caused a compile-time loop.
+. More problems have arisen in unanchored patterns when CRLF is a valid line
+     break. For example, the unstudied pattern [\r\n]A does not match the string
+     "\r\nA" because change 7.0/46 below moves the current point on by two
+     characters after failing to match at the start. However, the pattern \nA
+     *does* match, because it doesn't start till \n, and if [\r\n]A is studied,
+     the same is true. There doesn't seem any very clean way out of this, but
+     what I have chosen to do makes the common cases work: PCRE now takes note
+     of whether there can be an explicit match for \r or \n anywhere in the
+     pattern, and if so, 7.0/46 no longer applies. As part of this change,
+     there's a new PCRE_INFO_HASCRORLF option for finding out whether a compiled
+     pattern has explicit CR or LF references.
+. Added (*CR) etc for changing newline setting at start of pattern.
+ Version 7.2 19-Jun-07
+ ---------------------
+. If the fr_FR locale cannot be found for test 3, try the "french" locale,
+     which is apparently normally available under Windows.
+. Re-jig the pcregrep tests with different newline settings in an attempt
+     to make them independent of the local environment's newline setting.
+. Add code to configure.ac to remove -g from the CFLAGS default settings.
+. Some of the "internals" tests were previously cut out when the link size
+     was not 2, because the output contained actual offsets. The recent new
+     "Z" feature of pcretest means that these can be cut out, making the tests
+     usable with all link sizes.
+. Implemented Stan Switzer's goto replacement for longjmp() when not using
+     stack recursion. This gives a massive performance boost under BSD, but just
+     a small improvement under Linux. However, it saves one field in the frame
+     in all cases.
+. Added more features from the forthcoming Perl 5.10:
+     (a) (?-n) (where n is a string of digits) is a relative subroutine or
+         recursion call. It refers to the nth most recently opened parentheses.
+     (b) (?+n) is also a relative subroutine call; it refers to the nth next
+         to be opened parentheses.
+     (c) Conditions that refer to capturing parentheses can be specified
+         relatively, for example, (?(-2)... or (?(+3)...
+     (d) \K resets the start of the current match so that everything before
+         is not part of it.
+     (e) \k{name} is synonymous with \k<name> and \k'name' (.NET compatible).
+     (f) \g{name} is another synonym - part of Perl 5.10's unification of
+         reference syntax.
+     (g) (?| introduces a group in which the numbering of parentheses in each
+         alternative starts with the same number.
+     (h) \h, \H, \v, and \V match horizontal and vertical whitespace.
+. Added two new calls to pcre_fullinfo(): PCRE_INFO_OKPARTIAL and
+     PCRE_INFO_JCHANGED.
+. A pattern such as  (.*(.)?)*  caused pcre_exec() to fail by either not
+     terminating or by crashing. Diagnosed by Viktor Griph; it was in the code
+     for detecting groups that can match an empty string.
+. A pattern with a very large number of alternatives (more than several
+     hundred) was running out of internal workspace during the pre-compile
+     phase, where pcre_compile() figures out how much memory will be needed. A
+     bit of new cunning has reduced the workspace needed for groups with
+     alternatives. The 1000-alternative test pattern now uses 12 bytes of
+     workspace instead of running out of the 4096 that are available.
+. Inserted some missing (unsigned int) casts to get rid of compiler warnings.
+. Applied patch from Google to remove an optimization that didn't quite work.
+     The report of the bug said:
+       pcrecpp::RE("a*").FullMatch("aaa") matches, while
+       pcrecpp::RE("a*?").FullMatch("aaa") does not, and
+       pcrecpp::RE("a*?\\z").FullMatch("aaa") does again.
+. If \p or \P was used in non-UTF-8 mode on a character greater than 127
+     it matched the wrong number of bytes.
+ Version 7.1 24-Apr-07
+ ---------------------
+. Applied Bob Rossi and Daniel G's patches to convert the build system to one
+     that is more "standard", making use of automake and other Autotools. There
+     is some re-arrangement of the files and adjustment of comments consequent
+     on this.
+. Part of the patch fixed a problem with the pcregrep tests. The test of -r
+     for recursive directory scanning broke on some systems because the files
+     are not scanned in any specific order and on different systems the order
+     was different. A call to "sort" has been inserted into RunGrepTest for the
+     approprate test as a short-term fix. In the longer term there may be an
+     alternative.
+. I had an email from Eric Raymond about problems translating some of PCRE's
+     man pages to HTML (despite the fact that I distribute HTML pages, some
+     people do their own conversions for various reasons). The problems
+     concerned the use of low-level troff macros .br and .in. I have therefore
+     removed all such uses from the man pages (some were redundant, some could
+     be replaced by .nf/.fi pairs). The 132html script that I use to generate
+     HTML has been updated to handle .nf/.fi and to complain if it encounters
+     .br or .in.
+. Updated comments in configure.ac that get placed in config.h.in and also
+     arranged for config.h to be included in the distribution, with the name
+     config.h.generic, for the benefit of those who have to compile without
+     Autotools (compare pcre.h, which is now distributed as pcre.h.generic).
+. Updated the support (such as it is) for Virtual Pascal, thanks to Stefan
+     Weber: (1) pcre_internal.h was missing some function renames; (2) updated
+     makevp.bat for the current PCRE, using the additional files
+     makevp_c.txt, makevp_l.txt, and pcregexp.pas.
+. A Windows user reported a minor discrepancy with test 2, which turned out
+     to be caused by a trailing space on an input line that had got lost in his
+     copy. The trailing space was an accident, so I've just removed it.
+. Add -Wl,-R... flags in pcre-config.in for *BSD* systems, as I'm told
+     that is needed.
+. Mark ucp_table (in ucptable.h) and ucp_gentype (in pcre_ucp_searchfuncs.c)
+     as "const" (a) because they are and (b) because it helps the PHP
+     maintainers who have recently made a script to detect big data structures
+     in the php code that should be moved to the .rodata section. I remembered
+     to update Builducptable as well, so it won't revert if ucptable.h is ever
+     re-created.
+. Added some extra #ifdef SUPPORT_UTF8 conditionals into pcretest.c,
+     pcre_printint.src, pcre_compile.c, pcre_study.c, and pcre_tables.c, in
+     order to be able to cut out the UTF-8 tables in the latter when UTF-8
+     support is not required. This saves 1.5-2K of code, which is important in
+     some applications.
+     Later: more #ifdefs are needed in pcre_ord2utf8.c and pcre_valid_utf8.c
+     so as not to refer to the tables, even though these functions will never be
+     called when UTF-8 support is disabled. Otherwise there are problems with a
+     shared library.
+. Fixed two bugs in the emulated memmove() function in pcre_internal.h:
+     (a) It was defining its arguments as char * instead of void *.
+     (b) It was assuming that all moves were upwards in memory; this was true
+         a long time ago when I wrote it, but is no longer the case.
+     The emulated memove() is provided for those environments that have neither
+     memmove() nor bcopy(). I didn't think anyone used it these days, but that
+     is clearly not the case, as these two bugs were recently reported.
+. The script PrepareRelease is now distributed: it calls 132html, CleanTxt,
+     and Detrail to create the HTML documentation, the .txt form of the man
+     pages, and it removes trailing spaces from listed files. It also creates
+     pcre.h.generic and config.h.generic from pcre.h and config.h. In the latter
+     case, it wraps all the #defines with #ifndefs. This script should be run
+     before "make dist".
+. Fixed two fairly obscure bugs concerned with quantified caseless matching
+     with Unicode property support.
+     (a) For a maximizing quantifier, if the two different cases of the
+         character were of different lengths in their UTF-8 codings (there are
+         some cases like this - I found 11), and the matching function had to
+         back up over a mixture of the two cases, it incorrectly assumed they
+         were both the same length.
+     (b) When PCRE was configured to use the heap rather than the stack for
+         recursion during matching, it was not correctly preserving the data for
+         the other case of a UTF-8 character when checking ahead for a match
+         while processing a minimizing repeat. If the check also involved
+         matching a wide character, but failed, corruption could cause an
+         erroneous result when trying to check for a repeat of the original
+         character.
+. Some tidying changes to the testing mechanism:
+     (a) The RunTest script now detects the internal link size and whether there
+         is UTF-8 and UCP support by running ./pcretest -C instead of relying on
+         values substituted by "configure". (The RunGrepTest script already did
+         this for UTF-8.) The configure.ac script no longer substitutes the
+         relevant variables.
+     (b) The debugging options /B and /D in pcretest show the compiled bytecode
+         with length and offset values. This means that the output is different
+         for different internal link sizes. Test 2 is skipped for link sizes
+         other than 2 because of this, bypassing the problem. Unfortunately,
+         there was also a test in test 3 (the locale tests) that used /B and
+         failed for link sizes other than 2. Rather than cut the whole test out,
+         I have added a new /Z option to pcretest that replaces the length and
+         offset values with spaces. This is now used to make test 3 independent
+         of link size. (Test 2 will be tidied up later.)
+. If erroroffset was passed as NULL to pcre_compile, it provoked a
+     segmentation fault instead of returning the appropriate error message.
+. In multiline mode when the newline sequence was set to "any", the pattern
+     ^$ would give a match between the \r and \n of a subject such as "A\r\nB".
+     This doesn't seem right; it now treats the CRLF combination as the line
+     ending, and so does not match in that case. It's only a pattern such as ^$
+     that would hit this one: something like ^ABC$ would have failed after \r
+     and then tried again after \r\n.
+. Changed the comparison command for RunGrepTest from "diff -u" to "diff -ub"
+     in an attempt to make files that differ only in their line terminators
+     compare equal. This works on Linux.
+. Under certain error circumstances pcregrep might try to free random memory
+     as it exited. This is now fixed, thanks to valgrind.
+. In pcretest, if the pattern /(?m)^$/g<any> was matched against the string
+     "abc\r\n\r\n", it found an unwanted second match after the second \r. This
+     was because its rules for how to advance for /g after matching an empty
+     string at the end of a line did not allow for this case. They now check for
+     it specially.
+. pcretest is supposed to handle patterns and data of any length, by
+     extending its buffers when necessary. It was getting this wrong when the
+     buffer for a data line had to be extended.
+. Added PCRE_NEWLINE_ANYCRLF which is like ANY, but matches only CR, LF, or
+     CRLF as a newline sequence.
+. Code for handling Unicode properties in pcre_dfa_exec() wasn't being cut
+     out by #ifdef SUPPORT_UCP. This did no harm, as it could never be used, but
+     I have nevertheless tidied it up.
+. Added some casts to kill warnings from HP-UX ia64 compiler.
+. Added a man page for pcre-config.
+ Version 7.0 19-Dec-06
+ ---------------------
+. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
+     moving to gcc 4.1.1.
+. The -S option for pcretest uses setrlimit(); I had omitted to #include
+     sys/time.h, which is documented as needed for this function. It doesn't
+     seem to matter on Linux, but it showed up on some releases of OS X.
+. It seems that there are systems where bytes whose values are greater than
+match isprint() in the "C" locale. The "C" locale should be the
+     default when a C program starts up. In most systems, only ASCII printing
+     characters match isprint(). This difference caused the output from pcretest
+     to vary, making some of the tests fail. I have changed pcretest so that:
+     (a) When it is outputting text in the compiled version of a pattern, bytes
+         other than 32-126 are always shown as hex escapes.
+     (b) When it is outputting text that is a matched part of a subject string,
+         it does the same, unless a different locale has been set for the match
+         (using the /L modifier). In this case, it uses isprint() to decide.
+. Fixed a major bug that caused incorrect computation of the amount of memory
+     required for a compiled pattern when options that changed within the
+     pattern affected the logic of the preliminary scan that determines the
+     length. The relevant options are -x, and -i in UTF-8 mode. The result was
+     that the computed length was too small. The symptoms of this bug were
+     either the PCRE error "internal error: code overflow" from pcre_compile(),
+     or a glibc crash with a message such as "pcretest: free(): invalid next
+     size (fast)". Examples of patterns that provoked this bug (shown in
+     pcretest format) are:
+       /(?-x: )/x
+       /(?x)(?-x: \s*#\s*)/
+       /((?i)[\x{c0}])/8
+       /(?i:[\x{c0}])/8
+     HOWEVER: Change 17 below makes this fix obsolete as the memory computation
+     is now done differently.
+. Applied patches from Google to: (a) add a QuoteMeta function to the C++
+     wrapper classes; (b) implement a new function in the C++ scanner that is
+     more efficient than the old way of doing things because it avoids levels of
+     recursion in the regex matching; (c) add a paragraph to the documentation
+     for the FullMatch() function.
+. The escape sequence \n was being treated as whatever was defined as
+     "newline". Not only was this contrary to the documentation, which states
+     that \n is character 10 (hex 0A), but it also went horribly wrong when
+     "newline" was defined as CRLF. This has been fixed.
+. In pcre_dfa_exec.c the value of an unsigned integer (the variable called c)
+     was being set to -1 for the "end of line" case (supposedly a value that no
+     character can have). Though this value is never used (the check for end of
+     line is "zero bytes in current character"), it caused compiler complaints.
+     I've changed it to 0xffffffff.
+. In pcre_version.c, the version string was being built by a sequence of
+     C macros that, in the event of PCRE_PRERELEASE being defined as an empty
+     string (as it is for production releases) called a macro with an empty
+     argument. The C standard says the result of this is undefined. The gcc
+     compiler treats it as an empty string (which was what was wanted) but it is
+     reported that Visual C gives an error. The source has been hacked around to
+     avoid this problem.
+. On the advice of a Windows user, included <io.h> and <fcntl.h> in Windows
+     builds of pcretest, and changed the call to _setmode() to use _O_BINARY
+     instead of 0x8000. Made all the #ifdefs test both _WIN32 and WIN32 (not all
+     of them did).
+. Originally, pcretest opened its input and output without "b"; then I was
+     told that "b" was needed in some environments, so it was added for release
+.0 to both the input and output. (It makes no difference on Unix-like
+     systems.) Later I was told that it is wrong for the input on Windows. I've
+     now abstracted the modes into two macros, to make it easier to fiddle with
+     them, and removed "b" from the input mode under Windows.
+. Added pkgconfig support for the C++ wrapper library, libpcrecpp.
+. Added -help and --help to pcretest as an official way of being reminded
+     of the options.
+. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
+     and pcrecpp.cc because they annoy compilers at high warning levels.
+. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.
+. Fixed an occurrence of == in configure.ac that should have been = (shell
+     scripts are not C programs :-) and which was not noticed because it works
+     on Linux.
+. pcretest is supposed to handle any length of pattern and data line (as one
+     line or as a continued sequence of lines) by extending its input buffer if
+     necessary. This feature was broken for very long pattern lines, leading to
+     a string of junk being passed to pcre_compile() if the pattern was longer
+     than about 50K.
+. I have done a major re-factoring of the way pcre_compile() computes the
+     amount of memory needed for a compiled pattern. Previously, there was code
+     that made a preliminary scan of the pattern in order to do this. That was
+     OK when PCRE was new, but as the facilities have expanded, it has become
+     harder and harder to keep it in step with the real compile phase, and there
+     have been a number of bugs (see for example, 4 above). I have now found a
+     cunning way of running the real compile function in a "fake" mode that
+     enables it to compute how much memory it would need, while actually only
+     ever using a few hundred bytes of working memory and without too many
+     tests of the mode. This should make future maintenance and development
+     easier. A side effect of this work is that the limit of 200 on the nesting
+     depth of parentheses has been removed (though this was never a serious
+     limitation, I suspect). However, there is a downside: pcre_compile() now
+     runs more slowly than before (30% or more, depending on the pattern). I
+     hope this isn't a big issue. There is no effect on runtime performance.
+. Fixed a minor bug in pcretest: if a pattern line was not terminated by a
+     newline (only possible for the last line of a file) and it was a
+     pattern that set a locale (followed by /Lsomething), pcretest crashed.
+. Added additional timing features to pcretest. (1) The -tm option now times
+     matching only, not compiling. (2) Both -t and -tm can be followed, as a
+     separate command line item, by a number that specifies the number of
+     repeats to use when timing. The default is 50000; this gives better
+     precision, but takes uncomfortably long for very large patterns.
+. Extended pcre_study() to be more clever in cases where a branch of a
+     subpattern has no definite first character. For example, (a*|b*)[cd] would
+     previously give no result from pcre_study(). Now it recognizes that the
+     first character must be a, b, c, or d.
+. There was an incorrect error "recursive call could loop indefinitely" if
+     a subpattern (or the entire pattern) that was being tested for matching an
+     empty string contained only one non-empty item after a nested subpattern.
+     For example, the pattern (?>\x{100}*)\d(?R) provoked this error
+     incorrectly, because the \d was being skipped in the check.
+. The pcretest program now has a new pattern option /B and a command line
+     option -b, which is equivalent to adding /B to every pattern. This causes
+     it to show the compiled bytecode, without the additional information that
+     -d shows. The effect of -d is now the same as -b with -i (and similarly, /D
+     is the same as /B/I).
+. A new optimization is now able automatically to treat some sequences such
+     as a*b as a*+b. More specifically, if something simple (such as a character
+     or a simple class like \d) has an unlimited quantifier, and is followed by
+     something that cannot possibly match the quantified thing, the quantifier
+     is automatically "possessified".
+. A recursive reference to a subpattern whose number was greater than 39
+     went wrong under certain circumstances in UTF-8 mode. This bug could also
+     have affected the operation of pcre_study().
+. Realized that a little bit of performance could be had by replacing
+     (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.
+. Timing data from pcretest is now shown to 4 decimal places instead of 3.
+. Possessive quantifiers such as a++ were previously implemented by turning
+     them into atomic groups such as ($>a+). Now they have their own opcodes,
+     which improves performance. This includes the automatically created ones
+     from 23 above.
+. A pattern such as (?=(\w+))\1: which simulates an atomic group using a
+     lookahead was broken if it was not anchored. PCRE was mistakenly expecting
+     the first matched character to be a colon. This applied both to named and
+     numbered groups.
+. The ucpinternal.h header file was missing its idempotency #ifdef.
+. I was sent a "project" file called libpcre.a.dev which I understand makes
+     building PCRE on Windows easier, so I have included it in the distribution.
+. There is now a check in pcretest against a ridiculously large number being
+     returned by pcre_exec() or pcre_dfa_exec(). If this happens in a /g or /G
+     loop, the loop is abandoned.
+. Forward references to subpatterns in conditions such as (?(2)...) where
+     subpattern 2 is defined later cause pcre_compile() to search forwards in
+     the pattern for the relevant set of parentheses. This search went wrong
+     when there were unescaped parentheses in a character class, parentheses
+     escaped with \Q...\E, or parentheses in a #-comment in /x mode.
+. "Subroutine" calls and backreferences were previously restricted to
+     referencing subpatterns earlier in the regex. This restriction has now
+     been removed.
+. Added a number of extra features that are going to be in Perl 5.10. On the
+     whole, these are just syntactic alternatives for features that PCRE had
+     previously implemented using the Python syntax or my own invention. The
+     other formats are all retained for compatibility.
+     (a) Named groups can now be defined as (?<name>...) or (?'name'...) as well
+         as (?P<name>...). The new forms, as well as being in Perl 5.10, are
+         also .NET compatible.
+     (b) A recursion or subroutine call to a named group can now be defined as
+         (?&name) as well as (?P>name).
+     (c) A backreference to a named group can now be defined as \k<name> or
+         \k'name' as well as (?P=name). The new forms, as well as being in Perl
+.10, are also .NET compatible.
+     (d) A conditional reference to a named group can now use the syntax
+         (?(<name>) or (?('name') as well as (?(name).
+     (e) A "conditional group" of the form (?(DEFINE)...) can be used to define
+         groups (named and numbered) that are never evaluated inline, but can be
+         called as "subroutines" from elsewhere. In effect, the DEFINE condition
+         is always false. There may be only one alternative in such a group.
+     (f) A test for recursion can be given as (?(R1).. or (?(R&name)... as well
+         as the simple (?(R). The condition is true only if the most recent
+         recursion is that of the given number or name. It does not search out
+         through the entire recursion stack.
+     (g) The escape \gN or \g{N} has been added, where N is a positive or
+         negative number, specifying an absolute or relative reference.
+. Tidied to get rid of some further signed/unsigned compiler warnings and
+     some "unreachable code" warnings.
+. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
+     things, this adds five new scripts.
+. Perl ignores orphaned \E escapes completely. PCRE now does the same.
+     There were also incompatibilities regarding the handling of \Q..\E inside
+     character classes, for example with patterns like [\Qa\E-\Qz\E] where the
+     hyphen was adjacent to \Q or \E. I hope I've cleared all this up now.
+. Like Perl, PCRE detects when an indefinitely repeated parenthesized group
+     matches an empty string, and forcibly breaks the loop. There were bugs in
+     this code in non-simple cases. For a pattern such as  ^(a()*)*  matched
+     against  aaaa  the result was just "a" rather than "aaaa", for example. Two
+     separate and independent bugs (that affected different cases) have been
+     fixed.
+. Refactored the code to abolish the use of different opcodes for small
+     capturing bracket numbers. This is a tidy that I avoided doing when I
+     removed the limit on the number of capturing brackets for 3.5 back in 2001.
+     The new approach is not only tidier, it makes it possible to reduce the
+     memory needed to fix the previous bug (38).
+. Implemented PCRE_NEWLINE_ANY to recognize any of the Unicode newline
+     sequences (http://unicode.org/unicode/reports/tr18/) as "newline" when
+     processing dot, circumflex, or dollar metacharacters, or #-comments in /x
+     mode.
+. Add \R to match any Unicode newline sequence, as suggested in the Unicode
+     report.
+. Applied patch, originally from Ari Pollak, modified by Google, to allow
+     copy construction and assignment in the C++ wrapper.
+. Updated pcregrep to support "--newline=any". In the process, I fixed a
+     couple of bugs that could have given wrong results in the "--newline=crlf"
+     case.
+. Added a number of casts and did some reorganization of signed/unsigned int
+     variables following suggestions from Dair Grant. Also renamed the variable
+     "this" as "item" because it is a C++ keyword.
+. Arranged for dftables to add
+       #include "pcre_internal.h"
+     to pcre_chartables.c because without it, gcc 4.x may remove the array
+     definition from the final binary if PCRE is built into a static library and
+     dead code stripping is activated.
+. For an unanchored pattern, if a match attempt fails at the start of a
+     newline sequence, and the newline setting is CRLF or ANY, and the next two
+     characters are CRLF, advance by two characters instead of one.
+ Version 6.7 04-Jul-06
+ ---------------------
+. In order to handle tests when input lines are enormously long, pcretest has
+     been re-factored so that it automatically extends its buffers when
+     necessary. The code is crude, but this _is_ just a test program. The
+     default size has been increased from 32K to 50K.
+. The code in pcre_study() was using the value of the re argument before
+     testing it for NULL. (Of course, in any sensible call of the function, it
+     won't be NULL.)
+. The memmove() emulation function in pcre_internal.h, which is used on
+     systems that lack both memmove() and bcopy() - that is, hardly ever -
+     was missing a "static" storage class specifier.
+. When UTF-8 mode was not set, PCRE looped when compiling certain patterns
+     containing an extended class (one that cannot be represented by a bitmap
+     because it contains high-valued characters or Unicode property items, e.g.
+     [\pZ]). Almost always one would set UTF-8 mode when processing such a
+     pattern, but PCRE should not loop if you do not (it no longer does).
+     [Detail: two cases were found: (a) a repeated subpattern containing an
+     extended class; (b) a recursive reference to a subpattern that followed a
+     previous extended class. It wasn't skipping over the extended class
+     correctly when UTF-8 mode was not set.]
+. A negated single-character class was not being recognized as fixed-length
+     in lookbehind assertions such as (?<=[^f]), leading to an incorrect
+     compile error "lookbehind assertion is not fixed length".
+. The RunPerlTest auxiliary script was showing an unexpected difference
+     between PCRE and Perl for UTF-8 tests. It turns out that it is hard to
+     write a Perl script that can interpret lines of an input file either as
+     byte characters or as UTF-8, which is what "perltest" was being required to
+     do for the non-UTF-8 and UTF-8 tests, respectively. Essentially what you
+     can't do is switch easily at run time between having the "use utf8;" pragma
+     or not. In the end, I fudged it by using the RunPerlTest script to insert
+     "use utf8;" explicitly for the UTF-8 tests.
+. In multiline (/m) mode, PCRE was matching ^ after a terminating newline at
+     the end of the subject string, contrary to the documentation and to what
+     Perl does. This was true of both matching functions. Now it matches only at
+     the start of the subject and immediately after *internal* newlines.
+. A call of pcre_fullinfo() from pcretest to get the option bits was passing
+     a pointer to an int instead of a pointer to an unsigned long int. This
+     caused problems on 64-bit systems.
+. Applied a patch from the folks at Google to pcrecpp.cc, to fix "another
+     instance of the 'standard' template library not being so standard".
+. There was no check on the number of named subpatterns nor the maximum
+     length of a subpattern name. The product of these values is used to compute
+     the size of the memory block for a compiled pattern. By supplying a very
+     long subpattern name and a large number of named subpatterns, the size
+     computation could be caused to overflow. This is now prevented by limiting
+     the length of names to 32 characters, and the number of named subpatterns
+     to 10,000.
+. Subpatterns that are repeated with specific counts have to be replicated in
+     the compiled pattern. The size of memory for this was computed from the
+     length of the subpattern and the repeat count. The latter is limited to
+, but there was no limit on the former, meaning that integer overflow
+     could in principle occur. The compiled length of a repeated subpattern is
+     now limited to 30,000 bytes in order to prevent this.
+. Added the optional facility to have named substrings with the same name.
+. Added the ability to use a named substring as a condition, using the
+     Python syntax: (?(name)yes|no). This overloads (?(R)... and names that
+     are numbers (not recommended). Forward references are permitted.
+. Added forward references in named backreferences (if you see what I mean).
+. In UTF-8 mode, with the PCRE_DOTALL option set, a quantified dot in the
+     pattern could run off the end of the subject. For example, the pattern
+     "(?s)(.{1,5})"8 did this with the subject "ab".
+. If PCRE_DOTALL or PCRE_MULTILINE were set, pcre_dfa_exec() behaved as if
+     PCRE_CASELESS was set when matching characters that were quantified with ?
+     or *.
+. A character class other than a single negated character that had a minimum
+     but no maximum quantifier - for example [ab]{6,} - was not handled
+     correctly by pce_dfa_exec(). It would match only one character.
+. A valid (though odd) pattern that looked like a POSIX character
+     class but used an invalid character after [ (for example [[,abc,]]) caused
+     pcre_compile() to give the error "Failed: internal error: code overflow" or
+     in some cases to crash with a glibc free() error. This could even happen if
+     the pattern terminated after [[ but there just happened to be a sequence of
+     letters, a binary zero, and a closing ] in the memory that followed.
+. Perl's treatment of octal escapes in the range \400 to \777 has changed
+     over the years. Originally (before any Unicode support), just the bottom 8
+     bits were taken. Thus, for example, \500 really meant \100. Nowadays the
+     output from "man perlunicode" includes this:
+       The regular expression compiler produces polymorphic opcodes.  That
+       is, the pattern adapts to the data and automatically switches to
+       the Unicode character scheme when presented with Unicode data--or
+       instead uses a traditional byte scheme when presented with byte
+       data.
+     Sadly, a wide octal escape does not cause a switch, and in a string with
+     no other multibyte characters, these octal escapes are treated as before.
+     Thus, in Perl, the pattern  /\500/ actually matches \100 but the pattern
+     /\500|\x{1ff}/ matches \500 or \777 because the whole thing is treated as a
+     Unicode string.
+     I have not perpetrated such confusion in PCRE. Up till now, it took just
+     the bottom 8 bits, as in old Perl. I have now made octal escapes with
+     values greater than \377 illegal in non-UTF-8 mode. In UTF-8 mode they
+     translate to the appropriate multibyte character.
+. Applied some refactoring to reduce the number of warnings from Microsoft
+     and Borland compilers. This has included removing the fudge introduced
+     seven years ago for the OS/2 compiler (see 2.02/2 below) because it caused
+     a warning about an unused variable.
+. PCRE has not included VT (character 0x0b) in the set of whitespace
+     characters since release 4.0, because Perl (from release 5.004) does not.
+     [Or at least, is documented not to: some releases seem to be in conflict
+     with the documentation.] However, when a pattern was studied with
+     pcre_study() and all its branches started with \s, PCRE still included VT
+     as a possible starting character. Of course, this did no harm; it just
+     caused an unnecessary match attempt.
+. Removed a now-redundant internal flag bit that recorded the fact that case
+     dependency changed within the pattern. This was once needed for "required
+     byte" processing, but is no longer used. This recovers a now-scarce options
+     bit. Also moved the least significant internal flag bit to the most-
+     significant bit of the word, which was not previously used (hangover from
+     the days when it was an int rather than a uint) to free up another bit for
+     the future.
+. Added support for CRLF line endings as well as CR and LF. As well as the
+     default being selectable at build time, it can now be changed at runtime
+     via the PCRE_NEWLINE_xxx flags. There are now options for pcregrep to
+     specify that it is scanning data with non-default line endings.
+. Changed the definition of CXXLINK to make it agree with the definition of
+     LINK in the Makefile, by replacing LDFLAGS to CXXFLAGS.
+. Applied Ian Taylor's patches to avoid using another stack frame for tail
+     recursions. This makes a big different to stack usage for some patterns.
+. If a subpattern containing a named recursion or subroutine reference such
+     as (?P>B) was quantified, for example (xxx(?P>B)){3}, the calculation of
+     the space required for the compiled pattern went wrong and gave too small a
+     value. Depending on the environment, this could lead to "Failed: internal
+     error: code overflow at offset 49" or "glibc detected double free or
+     corruption" errors.
+. Applied patches from Google (a) to support the new newline modes and (b) to
+     advance over multibyte UTF-8 characters in GlobalReplace.
+. Change free() to pcre_free() in pcredemo.c. Apparently this makes a
+     difference for some implementation of PCRE in some Windows version.
+. Added some extra testing facilities to pcretest:
+     \q<number>   in a data line sets the "match limit" value
+     \Q<number>   in a data line sets the "match recursion limt" value
+     -S <number>  sets the stack size, where <number> is in megabytes
+     The -S option isn't available for Windows.
+ Version 6.6 06-Feb-06
+ ---------------------
+. Change 16(a) for 6.5 broke things, because PCRE_DATA_SCOPE was not defined
+     in pcreposix.h. I have copied the definition from pcre.h.
+. Change 25 for 6.5 broke compilation in a build directory out-of-tree
+     because pcre.h is no longer a built file.
+. Added Jeff Friedl's additional debugging patches to pcregrep. These are
+     not normally included in the compiled code.
  Version 6.5 01-Feb-06
  ---------------------

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