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ChangeLog for PCRE
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Version 7.0 19-Dec-06
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 1. Fixed a signed/unsigned compiler warning in pcre_compile.c, shown up by
    moving to gcc 4.1.1.

 2. 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.

 3. It seems that there are systems where bytes whose values are greater than
    127 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.

 4. 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.

 5. 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.

 6. 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.

 7. 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.

 8. 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.

 9. 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).

10. 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
    5.0 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.

11. Added pkgconfig support for the C++ wrapper library, libpcrecpp.

12. Added -help and --help to pcretest as an official way of being reminded
    of the options.

13. Removed some redundant semicolons after macro calls in pcrecpparg.h.in
    and pcrecpp.cc because they annoy compilers at high warning levels.

14. A bit of tidying/refactoring in pcre_exec.c in the main bumpalong loop.

15. 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.

16. 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.

17. 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.

18. 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.

19. 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.

20. 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.

21. 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.

22. 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).

23. 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".

24. 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().

25. Realized that a little bit of performance could be had by replacing
    (c & 0xc0) == 0xc0 with c >= 0xc0 when processing UTF-8 characters.

26. Timing data from pcretest is now shown to 4 decimal places instead of 3.

27. 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.

28. 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.

29. The ucpinternal.h header file was missing its idempotency #ifdef.

30. 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.

31. 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.

32. 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.

33. "Subroutine" calls and backreferences were previously restricted to
    referencing subpatterns earlier in the regex. This restriction has now
    been removed.

34. 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
        5.10, 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.

35. Tidied to get rid of some further signed/unsigned compiler warnings and
    some "unreachable code" warnings.

36. Updated the Unicode property tables to Unicode version 5.0.0. Amongst other
    things, this adds five new scripts.

37. 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.

38. 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.

39. 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).

40. 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.

41. Add \R to match any Unicode newline sequence, as suggested in the Unicode
    report.

42. Applied patch, originally from Ari Pollak, modified by Google, to allow
    copy construction and assignment in the C++ wrapper.

43. 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.

44. 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.

45. Arranged for dftables to add