ChangeLog

Change Log for PCRE2
--------------------

Before the move to GitHub, this was the only record of changes to PCRE2. Now
there is often more detail in the pull requests.


Version 10.43 16-February-2024
------------------------------

1. The test program added by change 2 of 10.42 didn't work when the default
newline setting didn't include \n as a newline. One test needed (*LF) to ensure
that it worked.

2. Added the new freestanding POSIX test program to the ManyConfigTests script
in the maint directory (overlooked in 2 below). Also improved the selection
facilities in that script, and added a test with JIT in a non-source directory,
fixing an oversight that would have made such a test fail before.

3. Added pcre2_get_match_data_heapframes_size() and related pcre2test flags
to allow for finer control of the heap used when pcre2_match() without JIT is
used and the match_data might be reused. This began as PR #191, but has had
further refinement and documentation edits.

4. Applied PR #181, which tidies some casts in pcre2_valid_utf.c.

5. Applied PR #184, which avoids overflow issues with the heap limit
(introduced in 10.41/9).

6. Applied PR #192, which changes the timing units for pcre2test from
milliseconds to microseconds. This is more useful for modern CPUs.

7. Applied PR #193, which makes the requirement for C99 explicit in
configure.ac and CMakeLists.txt.

8. Fixed a bug in pcre2test when a ridiculously large string repeat required a
stupid amount of memory. It now gives a clean realloc() failure error.

9. Updates to restrict the interaction between ASCII and non-ASCII characters
for caseless matching and items like \d:

   (a) Added PCRE2_EXTRA_CASELESS_RESTRICT to lock out mixing of ASCII and
       non-ASCII when matching caselessly. This is also /r in pcre2test and
       (?r) within patterns.

   (b) Added PCRE2_EXTRA_ASCII_{BSD,BSS,BSW,POSIX} and corresponding (?aD) etc
       in patterns and /a in pcre2test.

   (c) Corresponding updates to pcre2test.

10. Unicode has been updated to 15.0.0.

11. The Python scripts and ucptest.c in maint have been updated (a) a minor
change needed for 9(a) above; (b) fix bugs in ucptest,

12. Integer overflow testing is now centralized in a new function.

13. Made PCRE2_UCP the default in UTF mode in pcre2grep, and added new options
--case-restrict and --no-ucp.

14. In the debugging printint module (which is normally only linked into
pcre2test), avoid the use of a variable called "not" because that's deprecated
in C and forbidden in C++. Also rewrite some code to avoid a goto into a block
that bypassed its initialization (though it didn't actually matter).

15. More minor code adjustments to avoid using reserved C++ words as variable
names ("new" and "typename") and another jump that bypassed an (irrelevant)
initialization.

16. Merged a pull request that removed pcre2_ucptables.c from the list of files
to compile in NON-AUTOTOOLS-BUILD because it is #included in pcre2_tables.c.
Also adjusted the BUILD.bazel and build.zig files, which had the same issue. At
the same time, fixed a typo in the Bazel file.

17. Add PCRE2_EXTRA_ASCII_DIGIT to allow [:digit:] to be kept on sync with \d
even in UCP mode.

18. Fix an invalid match of ascii word classes when invalid utf is enabled.

19. Add a --posix-digit to pcre2grep for compatibility with GNU grep, and
other tools that prefer the POSIX compatible unicode definition for \d.

20. Report the bit width of the library in use by pcre2test for usability.

21. A pathological pattern conversion test could result in a string longer than
the available input buffer. Cause such a test to fail.

22. Add a check that forces a compiler error if PCRE2_CODE_UNIT_WIDTH is not 8,
16, or 32 when compiling any of the library modules.

23. Update pcre2_compile() to treat a NULL pattern with zero length as an empty
string.

24. Add support for limited-length variable-length lookbehind assertions, with
default maximum length 255 characters (same as Perl) but with a function to
adjust the limit.

25. Applied pull request #262, which updates the zig configuration, and #278
which fixes a bug with out-of-source-tree CMake build testing.

26. Add support for LoongArch to JIT.

27. Fixed a bug in pcre2_match() in the code for handling the vector of
backtracking frames on the heap, which caused a heap overflow if *LIMIT_HEAP
restricted an attempt to extend to less than the frame size. Generally tidy up
the code for extending the heap frames vector. This fixes GitHub issue #275.

28. Update pcre2_fuzzsupport.c to avoid clang sanitize complaint about shifting
left by 16 when there are non-zeros in the top 16 bits.

29. Perl 5.34.0 changed the meaning of (for example) {,3} which did not used to
be treated as a quantifier. Now it is interpreted as {0,3} and PCRE2 has
changed to match. Note that {,} is still not a quantifier.

30. Perl allows spaces and/or horizontal tabs after { or before } in all items
that use braces, and also before or after the comma in quantifiers. PCRE2 now
does the same, except for \u{...}, which is recognized only when
PCRE2_EXTRA_ALT_BSUX is set. This an ECMAScript, non-Perl compatible,
extension, so PCRE2 follows ECMAScript rather than Perl.

31. Applied pull request #300 by Carlo, which fixes #261. The bug was that
pcre2_match() was not fully resetting all captures that had been set within a
(possibly recursive) subroutine call such as (?3).

32. Changed the meaning of \w (and its synonyms) in UCP mode to match Perl. It
now matches characters whose general categories are L or N or whose particular
categories are Mn (non-spacing mark) or Pc (combining puntuation). The latter
includes underscore.

33. Changed the meaning of [:xdigit:] in UCP mode to match Perl. It now also
matches the "fullwidth" versions of the hex digits. Just like it is done for
[:digit:], PCRE2_EXTRA_ASCII_DIGIT can be used to keep this class ASCII only
without affecting other POSIX classes.

34. GitHub PR305 fixes a potential integer overflow in pcre2_dfa_match().

35. Updated handling of \b and \B in UCP mode to match the changes to \w in 32
above because \b and \B are defined in terms of \w.

36. Within a pattern (?aT) and (?-aT) set and reset the PCRE2_EXTRA_ASCII_DIGIT
option, and (?aP) also sets (?aT) so that (?-aP) disables all ASCII
restrictions on POSIX classes.

37. If PCRE2_FIRSTLINE was set on an anchored pattern, pcre2_match() and
pcre2_dfa_match() misbehaved. PCRE2_FIRSTLINE is now ignored for anchored
patterns.

38. Add a test for ridiculous ovector offset values to the substring extraction
functions.

39. Make OP_REVERSE use IMM2_SIZE for its data instead of LINK_SIZE, for
consistency with OP_VREVERSE.

40. In some legacy environments with a pre C99 snprintf, pcre2_regerror could
return an incorrect value when the provided buffer was too small.

41. Applied pull request #342 which adds sanity checks for ctype functions and
locks out any accidental sign-extension.

42. In the 32-bit library, in non-UTF mode, a quantifier that followed a
literal character with a value greater than or equal to 0x80000000u caused
undefined behaviour.

43. \z was misbehaving when matching fragments inside invalid UTF strings.

44. Implement --group-separator and --no-group-separator for pcre2grep.

45. Fix \X matching in 32 bit mode without UTF in JIT.

46. Fix backref iterators when PCRE2_MATCH_UNSET_BACKREF is set in JIT.

47. Refactor the handling of whole-pattern recursion (?0) in pcre2_match() so
that its end is handled similarly to other recursions. This has altered the
behaviour of   /|(?0)./endanchored   which was previously not right.

48. Improved the test for looping recursion by checking the last referenced
character as well as the current character. This allows some patterns that
previously triggered the check to run to completion instead of giving the loop
error.

49. In 32-bit mode, the compiler looped for the pattern /[\x{ffffffff}]/ when
PCRE2_CASELESS and PCRE2_UCP (but not PCRE2_UTF) were set. Fixed by not trying
to look for other cases for characters above the Unicode range.

50. In caseless 32-bit mode with UCP (but not UTF) set, the character
0xffffffff incorrectly matched any character that has more than one other case,
in particular k and s.

51. Fix accept and endanchored interaction in JIT.

52. Fix backreferences with unset backref and non-greedy iterators in JIT.

53. Improve the logic that checks for a list of starting code units -- positive
lookahead assertions are now ignored if the immediately following item is one
that sets a mandatory starting character. For example, /a?(?=bc|)d/ used to set
all of a, b, and d as possible starting code units; now it sets only a and d.

54. Fix incorrect class character matches in JIT.

55. In pcre2test, ensure pcre2_jit_match() is used when jitfast is used with
substitution testing.

56. Insert omitted setting of subject length in match data at the end of
pcre2_jit_match().

57. Implemented PCRE2_DISABLE_RECURSELOOP_CHECK for pcre2_match() to enable
some apparently looping recursions to run to completion and therefore match the
JIT behaviour. With this set, real loops will eventually get caught by match or
heap limits or run out of resource.

58. AC did a lot of work on pcre2_fuzzsupport.c to extend it to 16-bit and
32-bit libraries and to compare JIT and non-JIT matching.


Version 10.42 11-December-2022
------------------------------

1. Change 19 of 10.41 wasn't quite right; it put the definition of a default,
empty value for PCRE2_CALL_CONVENTION in src/pcre2posix.c instead of
src/pcre2posix.h, which meant that programs that included pcre2posix.h but not
pcre2.h failed to compile.

2. To catch similar issues to the above in future, a new small test program
that includes pcre2posix.h but not pcre2.h has been added to the test suite.

3. When the -S option of pcre2test was used to set a stack size greater than
the allowed maximum, the error message displayed the hard limit incorrectly.
This was pointed out on GitHub pull request #171, but the suggested patch
didn't cope with all cases. Some further modification was required.

4. Supplying an ovector count of more than 65535 to pcre2_match_data_create()
caused a crash because the field in the match data block is only 16 bits. A
maximum of 65535 is now silently applied.

5. Merged @carenas patch #175 which fixes #86 - segfault on aarch64 (ARM),

6. The prototype for pcre2_substring_list_free() specified its argument as
PCRE2_SPTR * which is a const data type, whereas the yield from
pcre2_substring_list() is not const. This caused compiler warnings. I have
changed the argument of pcre2_substring_list_free() to be PCRE2_UCHAR ** to
remove this anomaly. This might cause new warnings in existing code where a
cast has been used to avoid previous ones.


Version 10.41 06-December-2022
------------------------------

1. Add fflush() before and after a fork callout in pcre2grep to get its output
to be the same on all systems. (There were previously ordering differences in
Alpine Linux).

2. Merged patch from @carenas (GitHub #110) for pthreads support in CMake.

3. SSF scorecards grumbled about possible overflow in an expression in
pcre2test. It never would have overflowed in practice, but some casts have been
added and at the some time there's been some tidying of fprints that output
size_t values.

4. PR #94 showed up an unused enum in pcre2_convert.c, which is now removed.

5. Minor code re-arrangement to remove gcc warning about realloc() in
pcre2test.

6. Change a number of int variables that hold buffer and line lengths in
pcre2grep to PCRE2_SIZE (aka size_t).

7. Added an #ifdef to cut out a call to PRIV(jit_free) when JIT is not
supported (even though that function would do nothing in that case) at the
request of a user who doesn't even want to link with pcre_jit_compile.o. Also
tidied up an untidy #ifdef arrangement in pcre2test.

8. Fixed an issue in the backtracking optimization of character repeats in
JIT. Furthermore optimize star repetitions, not just plus repetitions.

9. Removed the use of an initial backtracking frames vector on the system stack
in pcre2_match() so that it now always uses the heap. (In a multi-thread
environment with very small stacks there had been an issue.) This also is
tidier for JIT matching, which didn't need that vector. The heap vector is now
remembered in the match data block and re-used if that block itself is re-used.
It is freed with the match data block.

10. Adjusted the find_limits code in pcre2test to work with change 9 above.

11. Added find_limits_noheap to pcre2test, because the heap limits are now
different in different environments and so cannot be included in the standard
tests.

12. Created a test for pcre2_match() heap processing that is not part of the
tests run by 'make check', but can be run manually. The current output is from
a 64-bit system.

13. Implemented -Z aka --null in pcre2grep.

14. A minor change to pcre2test and the addition of several new pcre2grep tests
have improved LCOV coverage statistics. At the same time, code in pcre2grep and
elsewhere that can never be obeyed in normal testing has been excluded from
coverage.

15. Fixed a bug in pcre2grep that could cause an extra newline to be written
after output generaed by --output.

16. If a file has a .bz2 extension but is not in fact compressed, pcre2grep
should process it as a plain text file. A bug stopped this happening; now fixed
and added to the tests.

17. When pcre2grep was running not in UTF mode, if a string specified by
--output or obtained from a callout in a pattern contained a character (byte)
greater than 127, it was incorrectly output in UTF-8 format.

18. Added some casts after warnings from Clang sanitize.

19. Merged patch from cbouc (GitHub #139): 4 function prototypes were missing
PCRE2_CALL_CONVENTION in src/pcre2posix.h. All function prototypes returning
pointers had out of place PCRE2_CALL_CONVENTION in src/pcre2.h.*. These
produced errors when building for Windows with #define PCRE2_CALL_CONVENTION
__stdcall.

20. A negative repeat value in a pcre2test subject line was not being
diagnosed, leading to infinite looping.

21. Updated RunGrepTest to discard the warning that Bash now gives when setting
LC_CTYPE to a bad value (because older versions didn't).

22. Updated pcre2grep so that it behaves like GNU grep when matching more than
one pattern and a later pattern matches at an earlier point in the subject when
the matched substrings are being identified by colour or by offsets.

23. Updated the PrepareRelease script so that the man page that it makes for
the pcre2demo demonstration program is more standard and does not cause errors
when processed by lexgrog or mandb -c (GitHub issue #160).

24. The JIT compiler was updated.


Version 10.40 15-April-2022
---------------------------

1. Merged patch from @carenas (GitHub #35, 7db87842) to fix pcre2grep incorrect
handling of multiple passes.

2. Merged patch from @carenas (GitHub #36, dae47509) to fix portability issue
in pcre2grep with buffered fseek(stdin).

3. Merged patch from @carenas (GitHub #37, acc520924) to fix tests when -S is
not supported.

4. Revert an unintended change in JIT repeat detection.

5. Merged patch from @carenas (GitHub #52, b037bfa1) to fix build on GNU Hurd.

6. Merged documentation and comments patches from @carenas (GitHub #47).

7. Merged patch from @carenas (GitHub #49) to remove obsolete JFriedl test code
from pcre2grep.

8. Merged patch from @carenas (GitHub #48) to fix CMake install issue #46.

9. Merged patch from @carenas (GitHub #53) fixing NULL checks in matching and
substituting.

10. Add null_subject and null_replacement modifiers to pcre2test.

11. Add check for NULL subject to POSIX regexec() function.

12. Add check for NULL replacement to pcre2_substitute().

13. For the subject arguments of pcre2_match(), pcre2_dfa_match(), and
pcre2_substitute(), and the replacement argument of the latter, if the pointer
is NULL and the length is zero, treat as an empty string. Apparently a number
of applications treat NULL/0 in this way.

14. Added support for Bidi_Class and a number of binary Unicode properties,
including Bidi_Control.

15. Fix some minor issues raised by clang sanitize.

16. Very minor code speed up for maximizing character property matches.

17. A number of changes to script matching for \p and \P:

    (a) Script extensions for a character are now coded as a bitmap instead of
        a list of script numbers, which should be faster and does not need a
        loop.

    (b) Added the syntax \p{script:xxx} and \p{script_extensions:xxx} (synonyms
        sc and scx).

    (c) Changed \p{scriptname} from being the same as \p{sc:scriptname} to being
        the same as \p{scx:scriptname} because this change happened in Perl at
        release 5.26.

    (d) The standard Unicode 4-letter abbreviations for script names are now
        recognized.

    (e) In accordance with Unicode and Perl's "loose matching" rules, spaces,
        hyphens, and underscores are ignored in property names, which are then
        matched independent of case.

18. The Python scripts in the maint directory have been refactored. There are
now three scripts that generate pcre2_ucd.c, pcre2_ucp.h, and pcre2_ucptables.c
(which is #included by pcre2_tables.c). The data lists that used to be
duplicated are now held in a single common Python module.

19. On CHERI, and thus Arm's Morello prototype, pointers are represented as
hardware capabilities, which consist of both an integer address and additional
metadata, meaning they are twice the size of the platform's size_t type, i.e.
16 bytes on a 64-bit system. The ovector member of heapframe happens to only be
8 byte aligned, and so computing frame_size ended up with a multiple of 8 but
not 16. Whilst the first frame was always suitably aligned, this then
misaligned the frame that follows, resulting in an alignment fault when storing
a pointer to Fecode at the start of match. Patch to fix this issue by Jessica
Clarke PR#72.

20. Added -LP and -LS listing options to pcre2test.

21. A user discovered that the library names in CMakeLists.txt for MSVC
debugger (PDB) files were incorrect - perhaps never tried for PCRE2?

22. An item such as [Aa] is optimized into a caseless single character match.
When this was quantified (e.g. [Aa]{2}) and was also the last literal item in a
pattern, the optimizing "must be present for a match" character check was not
being flagged as caseless, causing some matches that should have succeeded to
fail.

23. Fixed a unicode property matching issue in JIT. The character was not
fully read in caseless matching.

24. Fixed an issue affecting recursions in JIT caused by duplicated data
transfers.

25. Merged patch from @carenas (GitHub #96) which fixes some problems with
pcre2test and readline/readedit:

  * Use the right header for libedit in FreeBSD with autoconf
  * Really allow libedit with cmake
  * Avoid using readline headers with libedit


Version 10.39 29-October-2021
-----------------------------

1. Fix incorrect detection of alternatives in first character search in JIT.

2. Merged patch from @carenas (GitHub #28):

  Visual Studio 2013 includes support for %zu and %td, so let newer
  versions of it avoid the fallback, and while at it, make sure that
  the first check is for DISABLE_PERCENT_ZT so it will be always
  honoured if chosen.

  prtdiff_t is signed, so use a signed type instead, and make sure
  that an appropriate width is chosen if pointers are 64bit wide and
  long is not (ex: Windows 64bit).

  IMHO removing the cast (and therefore the possibilty of truncation)
  make the code cleaner and the fallback is likely portable enough
  with all 64-bit POSIX systems doing LP64 except for Windows.

3. Merged patch from @carenas (GitHub #29) to update to Unicode 14.0.0.

4. Merged patch from @carenas (GitHub #30):

  * Cleanup: remove references to no longer used stdint.h

  Since 19c50b9d (Unconditionally use inttypes.h instead of trying for stdint.h
  (simplification) and remove the now unnecessary inclusion in
  pcre2_internal.h., 2018-11-14), stdint.h is no longer used.

  Remove checks for it in autotools and CMake and document better the expected
  build failures for systems that might have stdint.h (C99) and not inttypes.h
  (from POSIX), like old Windows.

  * Cleanup: remove detection for inttypes.h which is a hard dependency

  CMake checks for standard headers are not meant to be used for hard
  dependencies, so will prevent a possible fallback to work.

  Alternatively, the header could be checked to make the configuration fail
  instead of breaking the build, but that was punted, as it was missing anyway
  from autotools.

5. Merged patch from @carenas (GitHub #32):

  * jit: allow building with ancient MSVC versions

  Visual Studio older than 2013 fails to build with JIT enabled, because it is
  unable to parse non C89 compatible syntax, with mixed declarations and code.
  While most recent compilers wouldn't even report this as a warning since it
  is valid C99, it could be also made visible by adding to gcc/clang the
  -Wdeclaration-after-statement flag at build time.

  Move the code below the affected definitions.

  * pcre2grep: avoid mixing declarations with code

  Since d5a61ee8 (Patch to detect (and ignore) symlink loops in pcre2grep,
  2021-08-28), code will fail to build in a strict C89 compiler.

  Reformat slightly to make it C89 compatible again.


Version 10.38 01-October-2021
-----------------------------

1. Fix invalid single character repetition issues in JIT when the repetition
is inside a capturing bracket and the bracket is preceded by character
literals.

2. Installed revised CMake configuration files provided by Jan-Willem Blokland.
This extends the CMake build system to build both static and shared libraries
in one go, builds the static library with PIC, and exposes PCRE2 libraries
using the CMake config files. JWB provided these notes:

- Introduced CMake variable BUILD_STATIC_LIBS to build the static library.

- Make a small modification to config-cmake.h.in by removing the PCRE2_STATIC
  variable. Added PCRE2_STATIC variable to the static build using the
  target_compile_definitions() function.

- Extended the CMake config files.

  - Introduced CMake variable PCRE2_USE_STATIC_LIBS to easily switch between
    the static and shared libraries.

  - Added the PCRE_STATIC variable to the target compile definitions for the
    import of the static library.

Building static and shared libraries using MSVC results in a name clash of
the libraries. Both static and shared library builds create, for example, the
file pcre2-8.lib. Therefore, I decided to change the static library names by
adding "-static". For example, pcre2-8.lib has become pcre2-8-static.lib.
[Comment by PH: this is MSVC-specific. It doesn't happen on Linux.]

3. Increased the minimum release number for CMake to 3.0.0 because older than
2.8.12 is deprecated (it was set to 2.8.5) and causes warnings. Even 3.0.0 is
quite old; it was released in 2014.

4. Implemented a modified version of Thomas Tempelmann's pcre2grep patch for
detecting symlink loops. This is dependent on the availability of realpath(),
which is now tested for in ./configure and CMakeLists.txt.

5. Implemented a modified version of Thomas Tempelmann's patch for faster
case-independent "first code unit" searches for unanchored patterns in 8-bit
mode in the interpreters. Instead of just remembering whether one case matched
or not, it remembers the position of a previous match so as to avoid
unnecessary repeated searching.

6. Perl now locks out \K in lookarounds, so PCRE2 now does the same by default.
However, just in case anybody was relying on the old behaviour, there is an
option called PCRE2_EXTRA_ALLOW_LOOKAROUND_BSK that enables the old behaviour.
An option has also been added to pcre2grep to enable this.

7. Re-enable a JIT optimization which was unintentionally disabled in 10.35.

8. There is a loop counter to catch excessively crazy patterns when checking
the lengths of lookbehinds at compile time. This was incorrectly getting reset
whenever a lookahead was processed, leading to some fuzzer-generated patterns
taking a very long time to compile when (?|) was present in the pattern,
because (?|) disables caching of group lengths.


Version 10.37 26-May-2021
-------------------------

1. Change RunGrepTest to use tr instead of sed when testing with binary
zero bytes, because sed varies a lot from system to system and has problems
with binary zeros. This is from Bugzilla #2681. Patch from Jeremie
Courreges-Anglas via Nam Nguyen. This fixes RunGrepTest for OpenBSD. Later:
it broke it for at least one version of Solaris, where tr can't handle binary
zeros. However, that system had /usr/xpg4/bin/tr installed, which works OK, so
RunGrepTest now checks for that command and uses it if found.

2. Compiling with gcc 10.2's -fanalyzer option showed up a hypothetical problem
with a NULL dereference. I don't think this case could ever occur in practice,
but I have put in a check in order to get rid of the compiler error.

3. An alternative patch for CMakeLists.txt because 10.36 #4 breaks CMake on
Windows. Patch from email@cs-ware.de fixes bugzilla #2688.

4. Two bugs related to over-large numbers have been fixed so the behaviour is
now the same as Perl.

  (a) A pattern such as /\214748364/ gave an overflow error instead of being
  treated as the octal number \214 followed by literal digits.

  (b) A sequence such as {65536 that has no terminating } so is not a
  quantifier was nevertheless complaining that a quantifier number was too big.

5. A run of autoconf suggested that configure.ac was out-of-date with respect
to the lastest autoconf. Running autoupdate made some valid changes, some valid
suggestions, and also some invalid changes, which were fixed by hand. Autoconf
now runs clean and the resulting "configure" seems to work, so I hope nothing
is broken. Later: the requirement for autoconf 2.70 broke some automatic test
robots. It doesn't seem to be necessary: trying a reduction to 2.60.

6. The pattern /a\K.(?0)*/ when matched against "abac" by the interpreter gave
the answer "bac", whereas Perl and JIT both yield "c". This was because the
effect of \K was not propagating back from the full pattern recursion. Other
recursions such as /(a\K.(?1)*)/ did not have this problem.

7. Restore single character repetition optimization in JIT. Currently fewer
character repetitions are optimized than in 10.34.

8. When the names of the functions in the POSIX wrapper were changed to
pcre2_regcomp() etc. (see change 10.33 #4 below), functions with the original
names were left in the library so that pre-compiled programs would still work.
However, this has proved troublesome when programs link with several libraries,
some of which use PCRE2 via the POSIX interface while others use a native POSIX
library. For this reason, the POSIX function names are removed in this release.
The macros in pcre2posix.h should ensure that re-compiling fixes any programs
that haven't been compiled since before 10.33.


Version 10.36 04-December-2020
------------------------------

1. Add CET_CFLAGS so that when Intel CET is enabled, pass -mshstk to
compiler. This fixes https://bugs.exim.org/show_bug.cgi?id=2578. Patch for
Makefile.am and configure.ac by H.J. Lu. Equivalent patch for CMakeLists.txt
invented by PH.

2. Fix inifinite loop when a single byte newline is searched in JIT when
invalid utf8 mode is enabled.

3. Updated CMakeLists.txt with patch from Wolfgang Stöggl (Bugzilla #2584):

  - Include GNUInstallDirs and use ${CMAKE_INSTALL_LIBDIR} instead of hardcoded
    lib. This allows differentiation between lib and lib64.
    CMAKE_INSTALL_LIBDIR is used for installation of libraries and also for
    pkgconfig file generation.

  - Add the version of PCRE2 to the configuration summary like ./configure
    does.

  - Fix typo: MACTHED_STRING->MATCHED_STRING

4. Updated CMakeLists.txt with another patch from Wolfgang Stöggl (Bugzilla
#2588):

  - Add escaped double quotes around include directory in CMakeLists.txt to
    allow spaces in directory names.

  - This fixes a cmake error, if the path of the pcre2 source contains a space.

5. Updated CMakeLists.txt with a patch from B. Scott Michel: CMake's
documentation suggests using CHECK_SYMBOL_EXISTS over CHECK_FUNCTION_EXIST.
Moreover, these functions come from specific header files, which need to be
specified (and, thankfully, are the same on both the Linux and WinXX
platforms.)

6. Added a (uint32_t) cast to prevent a compiler warning in pcre2_compile.c.

7. Applied a patch from Wolfgang Stöggl (Bugzilla #2600) to fix postfix for
debug Windows builds using CMake. This also updated configure so that it
generates *.pc files and pcre2-config with the same content, as in the past.

8. If a pattern ended with (?(VERSION=n.d where n is any number but d is just a
single digit, the code unit beyond d was being read (i.e. there was a read
buffer overflow). Fixes ClusterFuzz 23779.

9. After the rework in r1235, certain character ranges were incorrectly
handled by an optimization in JIT. Furthermore a wrong offset was used to
read a value from a buffer which could lead to memory overread.

10. Unnoticed for many years was the fact that delimiters other than / in the
testinput1 and testinput4 files could cause incorrect behaviour when these
files were processed by perltest.sh. There were several tests that used quotes
as delimiters, and it was just luck that they didn't go wrong with perltest.sh.
All the patterns in testinput1 and testinput4 now use / as their delimiter.
This fixes Bugzilla #2641.

11. Perl has started to give an error for \K within lookarounds (though there
are cases where it doesn't). PCRE2 still allows this, so the tests that include
this case have been moved from test 1 to test 2.

12. Further to 10 above, pcre2test has been updated to detect and grumble if a
delimiter other than / is used after #perltest.

13. Fixed a bug with PCRE2_MATCH_INVALID_UTF in 8-bit mode when PCRE2_CASELESS
was set and PCRE2_NO_START_OPTIMIZE was not set. The optimization for finding
the start of a match was not resetting correctly after a failed match on the
first valid fragment of the subject, possibly causing incorrect "no match"
returns on subsequent fragments. For example, the pattern /A/ failed to match
the subject \xe5A. Fixes Bugzilla #2642.

14. Fixed a bug in character set matching when JIT is enabled and both unicode
scripts and unicode classes are present at the same time.

15. Added GNU grep's -m (aka --max-count) option to pcre2grep.

16. Refactored substitution processing in pcre2grep strings, both for the -O
option and when dealing with callouts. There is now a single function that
handles $ expansion in all cases (instead of multiple copies of almost
identical code). This means that the same escape sequences are available
everywhere, which was not previously the case. At the same time, the escape
sequences $x{...} and $o{...} have been introduced, to allow for characters
whose code points are greater than 255 in Unicode mode.

17. Applied the patch from Bugzilla #2628 to RunGrepTest. This does an explicit
test for a version of sed that can handle binary zero, instead of assuming that
any Linux version will work. Later: replaced $(...) by `...` because not all
shells recognize the former.

18. Fixed a word boundary check bug in JIT when partial matching is enabled.

19. Fix ARM64 compilation warning in JIT. Patch by Carlo.

20. A bug in the RunTest script meant that if the first part of test 2 failed,
the failure was not reported.

21. Test 2 was failing when run from a directory other than the source
directory. This failure was previously missed in RunTest because of 20 above.
Fixes added to both RunTest and RunTest.bat.

22. Patch to CMakeLists.txt from Daniel to fix problem with testing under
Windows.


Version 10.35 09-May-2020
---------------------------

1. Use PCRE2_MATCH_EMPTY flag to detect empty matches in JIT.

2. Fix ARMv5 JIT improper handling of labels right after a constant pool.

3. A JIT bug is fixed which allowed to read the fields of the compiled
pattern before its existence is checked.

4. Back in the PCRE1 day, capturing groups that contained recursive back
references to themselves were made atomic (version 8.01, change 18) because
after the end a repeated group, the captured substrings had their values from
the final repetition, not from an earlier repetition that might be the
destination of a backtrack. This feature was documented, and was carried over
into PCRE2. However, it has now been realized that the major refactoring that
was done for 10.30 has made this atomicizing unnecessary, and it is confusing
when users are unaware of it, making some patterns appear not to be working as
expected. Capture values of recursive back references in repeated groups are
now correctly backtracked, so this unnecessary restriction has been removed.

5. Added PCRE2_SUBSTITUTE_LITERAL.

6. Avoid some VS compiler warnings.

7. Added PCRE2_SUBSTITUTE_MATCHED.

8. Added (?* and (?<* as synonyms for (*napla: and (*naplb: to match another
regex engine. The Perl regex folks are aware of this usage and have made a note
about it.

9. When an assertion is repeated, PCRE2 used to limit the maximum repetition to
1, believing that repeating an assertion is pointless. However, if a positive
assertion contains capturing groups, repetition can be useful. In any case, an
assertion could always be wrapped in a repeated group. The only restriction
that is now imposed is that an unlimited maximum is changed to one more than
the minimum.

10. Fix *THEN verbs in lookahead assertions in JIT.

11. Added PCRE2_SUBSTITUTE_REPLACEMENT_ONLY.

12. The JIT stack should be freed when the low-level stack allocation fails.

13. In pcre2grep, if the final line in a scanned file is output but does not
end with a newline sequence, add a newline according to the --newline setting.

14. (?(DEFINE)...) groups were not being handled correctly when checking for
the fixed length of a lookbehind assertion. Such a group within a lookbehind
should be skipped, as it does not contribute to the length of the group.
Instead, the (DEFINE) group was being processed, and if at the end of the
lookbehind, that end was not correctly recognized. Errors such as "lookbehind
assertion is not fixed length" and also "internal error: bad code value in
parsed_skip()" could result.

15. Put a limit of 1000 on recursive calls in pcre2_study() when searching
nested groups for starting code units, in order to avoid stack overflow issues.
If the limit is reached, it just gives up trying for this optimization.

16. The control verb chain list must always be restored when exiting from a
recurse function in JIT.

17. Fix a crash which occurs when the character type of an invalid UTF
character is decoded in JIT.

18. Changes in many areas of the code so that when Unicode is supported and
PCRE2_UCP is set without PCRE2_UTF, Unicode character properties are used for
upper/lower case computations on characters whose code points are greater than
127.

19. The function for checking UTF-16 validity was returning an incorrect offset
for the start of the error when a high surrogate was not followed by a valid
low surrogate. This caused incorrect behaviour, for example when
PCRE2_MATCH_INVALID_UTF was set and a match started immediately following the
invalid high surrogate, such as /aa/ matching "\x{d800}aa".

20. If a DEFINE group immediately preceded a lookbehind assertion, the pattern
could be mis-compiled and therefore not match correctly. This is the example
that found this: /(?(DEFINE)(?<foo>bar))(?<![-a-z0-9])word/ which failed to
match "word" because the "move back" value was set to zero.

21. Following a request from a user, some extensions and tidies to the
character tables handling have been done:

  (a) The dftables auxiliary program is renamed pcre2_dftables, but it is still
  not installed for public use.

  (b) There is now a -b option for pcre2_dftables, which causes the tables to
  be written in binary. There is also a -help option.

  (c) PCRE2_CONFIG_TABLES_LENGTH is added to pcre2_config() so that an
  application that wants to save tables in binary knows how long they are.

22. Changed setting of CMAKE_MODULE_PATH in CMakeLists.txt from SET to
LIST(APPEND...) to allow a setting from the command line to be included.

23. Updated to Unicode 13.0.0.

24. CMake build now checks for secure_getenv() and strerror(). Patch by Carlo.

25. Avoid using [-1] as a suffix in pcre2test because it can provoke a compiler
warning.

26. Added tests for __attribute__((uninitialized)) to both the configure and
CMake build files, and then applied this attribute to the variable called
stack_frames_vector[] in pcre2_match(). When implemented, this disables
automatic initialization (a facility in clang), which can take time on big
variables.

27. Updated CMakeLists.txt (patches by Uwe Korn) to add support for
pcre2-config, the libpcre*.pc files, SOVERSION, VERSION and the
MACHO_*_VERSIONS settings for CMake builds.

28. Another patch to CMakeLists.txt to check for mkostemp (configure already
does). Patch by Carlo Marcelo Arenas Belon.

29. Check for the existence of memfd_create in both CMake and configure
configurations. Patch by Carlo Marcelo Arenas Belon.

30. Restrict the configuration setting for the SELinux compatible execmem
allocator (change 10.30/44) to Linux and NetBSD.


Version 10.34 21-November-2019
------------------------------

1. The maximum number of capturing subpatterns is 65535 (documented), but no
check on this was ever implemented. This omission has been rectified; it fixes
ClusterFuzz 14376.

2. Improved the invalid utf32 support of the JIT compiler. Now it correctly
detects invalid characters in the 0xd800-0xdfff range.

3. Fix minor typo bug in JIT compile when \X is used in a non-UTF string.

4. Add support for matching in invalid UTF strings to the pcre2_match()
interpreter, and integrate with the existing JIT support via the new
PCRE2_MATCH_INVALID_UTF compile-time option.

5. Give more error detail for invalid UTF-8 when detected in pcre2grep.

6. Add support for invalid UTF-8 to pcre2grep.

7. Adjust the limit for "must have" code unit searching, in particular,
increase it substantially for non-anchored patterns.

8. Allow (*ACCEPT) to be quantified, because an ungreedy quantifier with a zero
minimum is potentially useful.

9. Some changes to the way the minimum subject length is handled:

   * When PCRE2_NO_START_OPTIMIZE is set, no minimum length is computed;
     pcre2test now omits this item instead of showing a value of zero.

   * An incorrect minimum length could be calculated for a pattern that
     contained (*ACCEPT) inside a qualified group whose minimum repetition was
     zero, for example /A(?:(*ACCEPT))?B/, which incorrectly computed a minimum
     of 2. The minimum length scan no longer happens for a pattern that
     contains (*ACCEPT).

   * When no minimum length is set by the normal scan, but a first and/or last
     code unit is recorded, set the minimum to 1 or 2 as appropriate.

   * When a pattern contains multiple groups with the same number, a back
     reference cannot know which one to scan for a minimum length. This used to
     cause the minimum length finder to give up with no result. Now it treats
     such references as not adding to the minimum length (which it should have
     done all along).

   * Furthermore, the above action now happens only if the back reference is to
     a group that exists more than once in a pattern instead of any back
     reference in a pattern with duplicate numbers.

10. A (*MARK) value inside a successful condition was not being returned by the
interpretive matcher (it was returned by JIT). This bug has been mended.

11. A bug in pcre2grep meant that -o without an argument (or -o0) didn't work
if the pattern had more than 32 capturing parentheses. This is fixed. In
addition (a) the default limit for groups requested by -o<n> has been raised to
50, (b) the new --om-capture option changes the limit, (c) an error is raised
if -o asks for a group that is above the limit.

12. The quantifier {1} was always being ignored, but this is incorrect when it
is made possessive and applied to an item in parentheses, because a
parenthesized item may contain multiple branches or other backtracking points,
for example /(a|ab){1}+c/ or /(a+){1}+a/.

13. For partial matches, pcre2test was always showing the maximum lookbehind
characters, flagged with "<", which is misleading when the lookbehind didn't
actually look behind the start (because it was later in the pattern). Showing
all consulted preceding characters for partial matches is now controlled by the
existing "allusedtext" modifier and, as for complete matches, this facility is
available only for non-JIT matching, because JIT does not maintain the first
and last consulted characters.

14. DFA matching (using pcre2_dfa_match()) was not recognising a partial match
if the end of the subject was encountered in a lookahead (conditional or
otherwise), an atomic group, or a recursion.

15. Give error if pcre2test -t, -T, -tm or -TM is given an argument of zero.

16. Check for integer overflow when computing lookbehind lengths. Fixes
Clusterfuzz issue 15636.

17. Implemented non-atomic positive lookaround assertions.

18. If a lookbehind contained a lookahead that contained another lookbehind
within it, the nested lookbehind was not correctly processed. For example, if
/(?<=(?=(?<=a)))b/ was matched to "ab" it gave no match instead of matching
"b".

19. Implemented pcre2_get_match_data_size().

20. Two alterations to partial matching:

    (a) The definition of a partial match is slightly changed: if a pattern
    contains any lookbehinds, an empty partial match may be given, because this
    is another situation where adding characters to the current subject can
    lead to a full match. Example: /c*+(?<=[bc])/ with subject "ab".

    (b) Similarly, if a pattern could match an empty string, an empty partial
    match may be given. Example: /(?![ab]).*/ with subject "ab". This case
    applies only to PCRE2_PARTIAL_HARD.

    (c) An empty string partial hard match can be returned for \z and \Z as it
    is documented that they shouldn't match.

21. A branch that started with (*ACCEPT) was not being recognized as one that
could match an empty string.

22. Corrected pcre2_set_character_tables() tables data type: was const unsigned
char * instead of const uint8_t *, as generated by pcre2_maketables().

23. Upgraded to Unicode 12.1.0.

24. Add -jitfast command line option to pcre2test (to make all the jit options
available directly).

25. Make pcre2test -C show if libreadline or libedit is supported.

26. If the length of one branch of a group exceeded 65535 (the maximum value
that is remembered as a minimum length), the whole group's length was
incorrectly recorded as 65535, leading to incorrect "no match" when start-up
optimizations were in force.

27. The "rightmost consulted character" value was not always correct; in
particular, if a pattern ended with a negative lookahead, characters that were
inspected in that lookahead were not included.

28. Add the pcre2_maketables_free() function.

29. The start-up optimization that looks for a unique initial matching
code unit in the interpretive engines uses memchr() in 8-bit mode. When the
search is caseless, it was doing so inefficiently, which ended up slowing down
the match drastically when the subject was very long. The revised code (a)
remembers if one case is not found, so it never repeats the search for that
case after a bumpalong and (b) when one case has been found, it searches only
up to that position for an earlier occurrence of the other case. This fix
applies to both interpretive pcre2_match() and to pcre2_dfa_match().

30. While scanning to find the minimum length of a group, if any branch has
minimum length zero, there is no need to scan any subsequent branches (a small
compile-time performance improvement).

31. Installed a .gitignore file on a user's suggestion. When using the svn
repository with git (through git svn) this helps keep it tidy.

32. Add underflow check in JIT which may occur when the value of subject
string pointer is close to 0.

33. Arrange for classes such as [Aa] which contain just the two cases of the
same character, to be treated as a single caseless character. This causes the
first and required code unit optimizations to kick in where relevant.

34. Improve the bitmap of starting bytes for positive classes that include wide
characters, but no property types, in UTF-8 mode. Previously, on encountering
such a class, the bits for all bytes greater than \xc4 were set, thus
specifying any character with codepoint >= 0x100. Now the only bits that are
set are for the relevant bytes that start the wide characters. This can give a
noticeable performance improvement.

35. If the bitmap of starting code units contains only 1 or 2 bits, replace it
with a single starting code unit (1 bit) or a caseless single starting code
unit if the two relevant characters are case-partners. This is particularly
relevant to the 8-bit library, though it applies to all. It can give a
performance boost for patterns such as [Ww]ord and (word|WORD). However, this
optimization doesn't happen if there is a "required" code unit of the same
value (because the search for a "required" code unit starts at the match start
for non-unique first code unit patterns, but after a unique first code unit,
and patterns such as a*a need the former action).

36. Small patch to pcre2posix.c to set the erroroffset field to -1 immediately
after a successful compile, instead of at the start of matching to avoid a
sanitizer complaint (regexec is supposed to be thread safe).

37. Add NEON vectorization to JIT to speed up matching of first character and
pairs of characters on ARM64 CPUs.

38. If a non-ASCII character was the first in a starting assertion in a
caseless match, the "first code unit" optimization did not get the casing
right, and the assertion failed to match a character in the other case if it
did not start with the same code unit.

39. Fixed the incorrect computation of jump sizes on x86 CPUs in JIT. A masking
operation was incorrectly removed in r1136. Reported by Ralf Junker.


Version 10.33 16-April-2019
---------------------------

1. Added "allvector" to pcre2test to make it easy to check the part of the
ovector that shouldn't be changed, in particular after substitute and failed or
partial matches.

2. Fix subject buffer overread in JIT when UTF is disabled and \X or \R has
a greater than 1 fixed quantifier. This issue was found by Yunho Kim.

3. Added support for callouts from pcre2_substitute(). After 10.33-RC1, but
prior to release, fixed a bug that caused a crash if pcre2_substitute() was
called with a NULL match context.

4. The POSIX functions are now all called pcre2_regcomp() etc., with wrapper
functions that use the standard POSIX names. However, in pcre2posix.h the POSIX
names are defined as macros. This should help avoid linking with the wrong
library in some environments while still exporting the POSIX names for
pre-existing programs that use them. (The Debian alternative names are also
defined as macros, but not documented.)

5. Fix an xclass matching issue in JIT.

6. Implement PCRE2_EXTRA_ESCAPED_CR_IS_LF (see Bugzilla 2315).

7. Implement the Perl 5.28 experimental alphabetic names for atomic groups and
lookaround assertions, for example, (*pla:...) and (*atomic:...). These are
characterized by a lower case letter following (* and to simplify coding for
this, the character tables created by pcre2_maketables() were updated to add a
new "is lower case letter" bit. At the same time, the now unused "is
hexadecimal digit" bit was removed. The default tables in
src/pcre2_chartables.c.dist are updated.

8. Implement the new Perl "script run" features (*script_run:...) and
(*atomic_script_run:...) aka (*sr:...) and (*asr:...).

9. Fixed two typos in change 22 for 10.21, which added special handling for
ranges such as a-z in EBCDIC environments. The original code probably never
worked, though there were no bug reports.

10. Implement PCRE2_COPY_MATCHED_SUBJECT for pcre2_match() (including JIT via
pcre2_match()) and pcre2_dfa_match(), but *not* the pcre2_jit_match() fast
path. Also, when a match fails, set the subject field in the match data to NULL
for tidiness - none of the substring extractors should reference this after
match failure.

11. If a pattern started with a subroutine call that had a quantifier with a
minimum of zero, an incorrect "match must start with this character" could be
recorded. Example: /(?&xxx)*ABC(?<xxx>XYZ)/ would (incorrectly) expect 'A' to
be the first character of a match.

12. The heap limit checking code in pcre2_dfa_match() could suffer from
overflow if the heap limit was set very large. This could cause incorrect "heap
limit exceeded" errors.

13. Add "kibibytes" to the heap limit output from pcre2test -C to make the
units clear.

14. Add a call to pcre2_jit_free_unused_memory() in pcre2grep, for tidiness.

15. Updated the VMS-specific code in pcre2test on the advice of a VMS user.

16. Removed the unnecessary inclusion of stdint.h (or inttypes.h) from
pcre2_internal.h as it is now included by pcre2.h. Also, change 17 for 10.32
below was unnecessarily complicated, as inttypes.h is a Standard C header,
which is defined to be a superset of stdint.h. Instead of conditionally
including stdint.h or inttypes.h, pcre2.h now unconditionally includes
inttypes.h. This supports environments that do not have stdint.h but do have
inttypes.h, which are known to exist. A note in the autotools documentation
says (November 2018) that there are none known that are the other way round.

17. Added --disable-percent-zt to "configure" (and equivalent to CMake) to
forcibly disable the use of %zu and %td in formatting strings because there is
at least one version of VMS that claims to be C99 but does not support these
modifiers.

18. Added --disable-pcre2grep-callout-fork, which restricts the callout support
in pcre2grep to the inbuilt echo facility. This may be useful in environments
that do not support fork().

19. Fix two instances of <= 0 being applied to unsigned integers (the VMS
compiler complains).

20. Added "fork" support for VMS to pcre2grep, for running an external program
via a string callout.

21. Improve MAP_JIT flag usage on MacOS. Patch by Rich Siegel.

22. If a pattern started with (*MARK), (*COMMIT), (*PRUNE), (*SKIP), or (*THEN)
followed by ^ it was not recognized as anchored.

23. The RunGrepTest script used to cut out the test of NUL characters for
Solaris and MacOS as printf and sed can't handle them. It seems that the *BSD
systems can't either. I've inverted the test so that only those OS that are
known to work (currently only Linux) try to run this test.

24. Some tests in RunGrepTest appended to testtrygrep from two different file
descriptors instead of redirecting stderr to stdout. This worked on Linux, but
it was reported not to on other systems, causing the tests to fail.

25. In the RunTest script, make the test for stack setting use the same value
for the stack as it needs for -bigstack.

26. Insert a cast in pcre2_dfa_match.c to suppress a compiler warning.

26. With PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL set, escape sequences such as \s
which are valid in character classes, but not as the end of ranges, were being
treated as literals. An example is [_-\s] (but not [\s-_] because that gave an
error at the *start* of a range). Now an "invalid range" error is given
independently of PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL.

27. Related to 26 above, PCRE2_BAD_ESCAPE_IS_LITERAL was affecting known escape
sequences such as \eX when they appeared invalidly in a character class. Now
the option applies only to unrecognized or malformed escape sequences.

28. Fix word boundary in JIT compiler. Patch by Mike Munday.

29. The pcre2_dfa_match() function was incorrectly handling conditional version
tests such as (?(VERSION>=0)...) when the version test was true. Incorrect
processing or a crash could result.

30. When PCRE2_UTF is set, allow non-ASCII letters and decimal digits in group
names, as Perl does. There was a small bug in this new code, found by
ClusterFuzz 12950, fixed before release.

31. Implemented PCRE2_EXTRA_ALT_BSUX to support ECMAScript 6's \u{hhh}
construct.

32. Compile \p{Any} to be the same as . in DOTALL mode, so that it benefits
from auto-anchoring if \p{Any}* starts a pattern.

33. Compile invalid UTF check in JIT test when only pcre32 is enabled.

34. For some time now, CMake has been warning about the setting of policy
CMP0026 to "OLD" in CmakeLists.txt, and hinting that the feature might be
removed in a future version. A request for CMake expertise on the list produced
no result, so I have now hacked CMakeLists.txt along the lines of some changes
I found on the Internet. The new code no longer needs the policy setting, and
it appears to work fine on Linux.

35. Setting --enable-jit=auto for an out-of-tree build failed because the
source directory wasn't in the search path for AC_TRY_COMPILE always. Patch
from Ross Burton.

36. Disable SSE2 JIT optimizations in x86 CPUs when SSE2 is not available.
Patch by Guillem Jover.

37. Changed expressions such as 1<<10 to 1u<<10 in many places because compiler
warnings were reported.

38. Using the clang compiler with sanitizing options causes runtime complaints
about truncation for statements such as x = ~x when x is an 8-bit value; it
seems to compute ~x as a 32-bit value. Changing such statements to x = 255 ^ x
gets rid of the warnings. There were also two missing casts in pcre2test.


Version 10.32 10-September-2018
-------------------------------

1. When matching using the REG_STARTEND feature of the POSIX API with a
non-zero starting offset, unset capturing groups with lower numbers than a
group that did capture something were not being correctly returned as "unset"
(that is, with offset values of -1).

2. When matching using the POSIX API, pcre2test used to omit listing unset
groups altogether. Now it shows those that come before any actual captures as
"<unset>", as happens for non-POSIX matching.

3. Running "pcre2test -C" always stated "\R matches CR, LF, or CRLF only",
whatever the build configuration was. It now correctly says "\R matches all
Unicode newlines" in the default case when --enable-bsr-anycrlf has not been
specified. Similarly, running "pcre2test -C bsr" never produced the result
ANY.

4. Matching the pattern /(*UTF)\C[^\v]+\x80/ against an 8-bit string containing
multi-code-unit characters caused bad behaviour and possibly a crash. This
issue was fixed for other kinds of repeat in release 10.20 by change 19, but
repeating character classes were overlooked.

5. pcre2grep now supports the inclusion of binary zeros in patterns that are
read from files via the -f option.

6. A small fix to pcre2grep to avoid compiler warnings for -Wformat-overflow=2.

7. Added --enable-jit=auto support to configure.ac.

8. Added some dummy variables to the heapframe structure in 16-bit and 32-bit
modes for the benefit of m68k, where pointers can be 16-bit aligned. The
dummies force 32-bit alignment and this ensures that the structure is a
multiple of PCRE2_SIZE, a requirement that is tested at compile time. In other
architectures, alignment requirements take care of this automatically.

9. When returning an error from pcre2_pattern_convert(), ensure the error
offset is set zero for early errors.

10. A number of patches for Windows support from Daniel Richard G:

  (a) List of error numbers in Runtest.bat corrected (it was not the same as in
      Runtest).

  (b) pcre2grep snprintf() workaround as used elsewhere in the tree.

  (c) Support for non-C99 snprintf() that returns -1 in the overflow case.

11. Minor tidy of pcre2_dfa_match() code.

12. Refactored pcre2_dfa_match() so that the internal recursive calls no longer
use the stack for local workspace and local ovectors. Instead, an initial block
of stack is reserved, but if this is insufficient, heap memory is used. The
heap limit parameter now applies to pcre2_dfa_match().

13. If a "find limits" test of DFA matching in pcre2test resulted in too many
matches for the ovector, no matches were displayed.

14. Removed an occurrence of ctrl/Z from test 6 because Windows treats it as
EOF. The test looks to have come from a fuzzer.

15. If PCRE2 was built with a default match limit a lot greater than the
default default of 10 000 000, some JIT tests of the match limit no longer
failed. All such tests now set 10 000 000 as the upper limit.

16. Another Windows related patch for pcregrep to ensure that WIN32 is
undefined under Cygwin.

17. Test for the presence of stdint.h and inttypes.h in configure and CMake and
include whichever exists (stdint preferred) instead of unconditionally
including stdint. This makes life easier for old and non-standard systems.

18. Further changes to improve portability, especially to old and or non-
standard systems:

  (a) Put all printf arguments in RunGrepTest into single, not double, quotes,
      and use \0 not \x00 for binary zero.

  (b) Avoid the use of C++ (i.e. BCPL) // comments.

  (c) Parameterize the use of %zu in pcre2test to make it like %td. For both of
      these now, if using MSVC or a standard C before C99, %lu is used with a
      cast if necessary.

19. Applied a contributed patch to CMakeLists.txt to increase the stack size
when linking pcre2test with MSVC. This gets rid of a stack overflow error in
the standard set of tests.

20. Output a warning in pcre2test when ignoring the "altglobal" modifier when
it is given with the "replace" modifier.

21. In both pcre2test and pcre2_substitute(), with global matching, a pattern
that matched an empty string, but never at the starting match offset, was not
handled in a Perl-compatible way. The pattern /(<?=\G.)/ is an example of such
a pattern. Because \G is in a lookbehind assertion, there has to be a
"bumpalong" before there can be a match. The automatic "advance by one
character after an empty string match" rule is therefore inappropriate. A more
complicated algorithm has now been implemented.

22. When checking to see if a lookbehind is of fixed length, lookaheads were
correctly ignored, but qualifiers on lookaheads were not being ignored, leading
to an incorrect "lookbehind assertion is not fixed length" error.

23. The VERSION condition test was reading fractional PCRE2 version numbers
such as the 04 in 10.04 incorrectly and hence giving wrong results.

24. Updated to Unicode version 11.0.0. As well as the usual addition of new
scripts and characters, this involved re-jigging the grapheme break property
algorithm because Unicode has changed the way emojis are handled.

25. Fixed an obscure bug that struck when there were two atomic groups not
separated by something with a backtracking point. There could be an incorrect
backtrack into the first of the atomic groups. A complicated example is
/(?>a(*:1))(?>b)(*SKIP:1)x|.*/ matched against "abc", where the *SKIP
shouldn't find a MARK (because is in an atomic group), but it did.

26. Upgraded the perltest.sh script: (1) #pattern lines can now be used to set
a list of modifiers for all subsequent patterns - only those that the script
recognizes are meaningful; (2) #subject lines can be used to set or unset a
default "mark" modifier; (3) Unsupported #command lines give a warning when
they are ignored; (4) Mark data is output only if the "mark" modifier is
present.

27. (*ACCEPT:ARG), (*FAIL:ARG), and (*COMMIT:ARG) are now supported.

28. A (*MARK) name was not being passed back for positive assertions that were
terminated by (*ACCEPT).

29. Add support for \N{U+dddd}, but only in Unicode mode.

30. Add support for (?^) for unsetting all imnsx options.

31. The PCRE2_EXTENDED (/x) option only ever discarded space characters whose
code point was less than 256 and that were recognized by the lookup table
generated by pcre2_maketables(), which uses isspace() to identify white space.
Now, when Unicode support is compiled, PCRE2_EXTENDED also discards U+0085,
U+200E, U+200F, U+2028, and U+2029, which are additional characters defined by
Unicode as "Pattern White Space". This makes PCRE2 compatible with Perl.

32. In certain circumstances, option settings within patterns were not being
correctly processed. For example, the pattern /((?i)A)(?m)B/ incorrectly
matched "ab". (The (?m) setting lost the fact that (?i) should be reset at the
end of its group during the parse process, but without another setting such as
(?m) the compile phase got it right.) This bug was introduced by the
refactoring in release 10.23.

33. PCRE2 uses bcopy() if available when memmove() is not, and it used just to
define memmove() as function call to bcopy(). This hasn't been tested for a
long time because in pcre2test the result of memmove() was being used, whereas
bcopy() doesn't return a result. This feature is now refactored always to call
an emulation function when there is no memmove(). The emulation makes use of
bcopy() when available.

34. When serializing a pattern, set the memctl, executable_jit, and tables
fields (that is, all the fields that contain pointers) to zeros so that the
result of serializing is always the same. These fields are re-set when the
pattern is deserialized.

35. In a pattern such as /[^\x{100}-\x{ffff}]*[\x80-\xff]/ which has a repeated
negative class with no characters less than 0x100 followed by a positive class
with only characters less than 0x100, the first class was incorrectly being
auto-possessified, causing incorrect match failures.

36. Removed the character type bit ctype_meta, which dates from PCRE1 and is
not used in PCRE2.

37. Tidied up unnecessarily complicated macros used in the escapes table.

38. Since 10.21, the new testoutput8-16-4 file has accidentally been omitted
from distribution tarballs, owing to a typo in Makefile.am which had
testoutput8-16-3 twice. Now fixed.

39. If the only branch in a conditional subpattern was anchored, the whole
subpattern was treated as anchored, when it should not have been, since the
assumed empty second branch cannot be anchored. Demonstrated by test patterns
such as /(?(1)^())b/ or /(?(?=^))b/.

40. A repeated conditional subpattern that could match an empty string was
always assumed to be unanchored. Now it is checked just like any other
repeated conditional subpattern, and can be found to be anchored if the minimum
quantifier is one or more. I can't see much use for a repeated anchored
pattern, but the behaviour is now consistent.

41. Minor addition to pcre2_jit_compile.c to avoid static analyzer complaint
(for an event that could never occur but you had to have external information
to know that).

42. If before the first match in a file that was being searched by pcre2grep
there was a line that was sufficiently long to cause the input buffer to be
expanded, the variable holding the location of the end of the previous match
was being adjusted incorrectly, and could cause an overflow warning from a code
sanitizer. However, as the value is used only to print pending "after" lines
when the next match is reached (and there are no such lines in this case) this
bug could do no damage.


Version 10.31 12-February-2018
------------------------------

1. Fix typo (missing ]) in VMS code in pcre2test.c.

2. Replace the replicated code for matching extended Unicode grapheme sequences
(which got a lot more complicated by change 10.30/49) by a single subroutine
that is called by both pcre2_match() and pcre2_dfa_match().

3. Add idempotent guard to pcre2_internal.h.

4. Add new pcre2_config() options: PCRE2_CONFIG_NEVER_BACKSLASH_C and
PCRE2_CONFIG_COMPILED_WIDTHS.

5. Cut out \C tests in the JIT regression tests when NEVER_BACKSLASH_C is
defined (e.g. by --enable-never-backslash-C).

6. Defined public names for all the pcre2_compile() error numbers, and used
the public names in pcre2_convert.c.

7. Fixed a small memory leak in pcre2test (convert contexts).

8. Added two casts to compile.c and one to match.c to avoid compiler warnings.

9. Added code to pcre2grep when compiled under VMS to set the symbol
PCRE2GREP_RC to the exit status, because VMS does not distinguish between
exit(0) and exit(1).

10. Added the -LM (list modifiers) option to pcre2test. Also made -C complain
about a bad option only if the following argument item does not start with a
hyphen.

11. pcre2grep was truncating components of file names to 128 characters when
processing files with the -r option, and also (some very odd code) truncating
path names to 512 characters. There is now a check on the absolute length of
full path file names, which may be up to 2047 characters long.

12. When an assertion contained (*ACCEPT) it caused all open capturing groups
to be closed (as for a non-assertion ACCEPT), which was wrong and could lead to
misbehaviour for subsequent references to groups that started outside the
assertion. ACCEPT in an assertion now closes only those groups that were
started within that assertion. Fixes oss-fuzz issues 3852 and 3891.

13. Multiline matching in pcre2grep was misbehaving if the pattern matched
within a line, and then matched again at the end of the line and over into
subsequent lines. Behaviour was different with and without colouring, and
sometimes context lines were incorrectly printed and/or line endings were lost.
All these issues should now be fixed.

14. If --line-buffered was specified for pcre2grep when input was from a
compressed file (.gz or .bz2) a segfault occurred. (Line buffering should be
ignored for compressed files.)

15. Although pcre2_jit_match checks whether the pattern is compiled
in a given mode, it was also expected that at least one mode is available.
This is fixed and pcre2_jit_match returns with PCRE2_ERROR_JIT_BADOPTION
when the pattern is not optimized by JIT at all.

16. The line number and related variables such as match counts in pcre2grep
were all int variables, causing overflow when files with more than 2147483647
lines were processed (assuming 32-bit ints). They have all been changed to
unsigned long ints.

17. If a backreference with a minimum repeat count of zero was first in a
pattern, apart from assertions, an incorrect first matching character could be
recorded. For example, for the pattern /(?=(a))\1?b/, "b" was incorrectly set
as the first character of a match.

18. Characters in a leading positive assertion are considered for recording a
first character of a match when the rest of the pattern does not provide one.
However, a character in a non-assertive group within a leading assertion such
as in the pattern /(?=(a))\1?b/ caused this process to fail. This was an
infelicity rather than an outright bug, because it did not affect the result of
a match, just its speed. (In fact, in this case, the starting 'a' was
subsequently picked up in the study.)

19. A minor tidy in pcre2_match(): making all PCRE2_ERROR_ returns use "return"
instead of "RRETURN" saves unwinding the backtracks in these cases (only one
didn't).

20. Allocate a single callout block on the stack at the start of pcre2_match()
and set its never-changing fields once only. Do the same for pcre2_dfa_match().

21. Save the extra compile options (set in the compile context) with the
compiled pattern (they were not previously saved), add PCRE2_INFO_EXTRAOPTIONS
to retrieve them, and update pcre2test to show them.

22. Added PCRE2_CALLOUT_STARTMATCH and PCRE2_CALLOUT_BACKTRACK bits to a new
field callout_flags in callout blocks. The bits are set by pcre2_match(), but
not by JIT or pcre2_dfa_match(). Their settings are shown in pcre2test callouts
if the callout_extra subject modifier is set. These bits are provided to help
with tracking how a backtracking match is proceeding.

23. Updated the pcre2demo.c demonstration program, which was missing the extra
code for -g that handles the case when \K in an assertion causes the match to
end at the original start point. Also arranged for it to detect when \K causes
the end of a match to be before its start.

24. Similar to 23 above, strange things (including loops) could happen in
pcre2grep when \K was used in an assertion when --colour was used or in
multiline mode. The "end at original start point" bug is fixed, and if the end
point is found to be before the start point, they are swapped.

25. When PCRE2_FIRSTLINE without PCRE2_NO_START_OPTIMIZE was used in non-JIT
matching (both pcre2_match() and pcre2_dfa_match()) and the matched string
started with the first code unit of a newline sequence, matching failed because
it was not tried at the newline.

26. Code for giving up a non-partial match after failing to find a starting
code unit anywhere in the subject was missing when searching for one of a
number of code units (the bitmap case) in both pcre2_match() and
pcre2_dfa_match(). This was a missing optimization rather than a bug.

27. Tidied up the ACROSSCHAR macro to be like FORWARDCHAR and BACKCHAR, using a
pointer argument rather than a code unit value. This should not have affected
the generated code.

28. The JIT compiler has been updated.

29. Avoid pointer overflow for unset captures in pcre2_substring_list_get().
This could not actually cause a crash because it was always used in a memcpy()
call with zero length.

30. Some internal structures have a variable-length ovector[] as their last
element. Their actual memory is obtained dynamically, giving an ovector of
appropriate length. However, they are defined in the structure as
ovector[NUMBER], where NUMBER is large so that array bound checkers don't
grumble. The value of NUMBER was 10000, but a fuzzer exceeded 5000 capturing
groups, making the ovector larger than this. The number has been increased to
131072, which allows for the maximum number of captures (65535) plus the
overall match. This fixes oss-fuzz issue 5415.

31. Auto-possessification at the end of a capturing group was dependent on what
follows the group (e.g. /(a+)b/ would auto-possessify the a+) but this caused
incorrect behaviour when the group was called recursively from elsewhere in the
pattern where something different might follow. This bug is an unforseen
consequence of change #1 for 10.30 - the implementation of backtracking into
recursions. Iterators at the ends of capturing groups are no longer considered
for auto-possessification if the pattern contains any recursions. Fixes
Bugzilla #2232.


Version 10.30 14-August-2017
----------------------------

1. The main interpreter, pcre2_match(), has been refactored into a new version
that does not use recursive function calls (and therefore the stack) for
remembering backtracking positions. This makes --disable-stack-for-recursion a
NOOP. The new implementation allows backtracking into recursive group calls in
patterns, making it more compatible with Perl, and also fixes some other
hard-to-do issues such as #1887 in Bugzilla. The code is also cleaner because
the old code had a number of fudges to try to reduce stack usage. It seems to
run no slower than the old code.

A number of bugs in the refactored code were subsequently fixed during testing
before release, but after the code was made available in the repository. These
bugs were never in fully released code, but are noted here for the record.

  (a) If a pattern had fewer capturing parentheses than the ovector supplied in
      the match data block, a memory error (detectable by ASAN) occurred after
      a match, because the external block was being set from non-existent
      internal ovector fields. Fixes oss-fuzz issue 781.

  (b) A pattern with very many capturing parentheses (when the internal frame
      size was greater than the initial frame vector on the stack) caused a
      crash. A vector on the heap is now set up at the start of matching if the
      vector on the stack is not big enough to handle at least 10 frames.
      Fixes oss-fuzz issue 783.

  (c) Handling of (*VERB)s in recursions was wrong in some cases.

  (d) Captures in negative assertions that were used as conditions were not
      happening if the assertion matched via (*ACCEPT).

  (e) Mark values were not being passed out of recursions.

  (f) Refactor some code in do_callout() to avoid picky compiler warnings about
      negative indices. Fixes oss-fuzz issue 1454.

  (g) Similarly refactor the way the variable length ovector is addressed for
      similar reasons. Fixes oss-fuzz issue 1465.

2. Now that pcre2_match() no longer uses recursive function calls (see above),
the "match limit recursion" value seems misnamed. It still exists, and limits
the depth of tree that is searched. To avoid future confusion, it has been
renamed as "depth limit" in all relevant places (--with-depth-limit,
(*LIMIT_DEPTH), pcre2_set_depth_limit(), etc) but the old names are still
available for backwards compatibility.

3. Hardened pcre2test so as to reduce the number of bugs reported by fuzzers:

  (a) Check for malloc failures when getting memory for the ovector (POSIX) or
      the match data block (non-POSIX).

4. In the 32-bit library in non-UTF mode, an attempt to find a Unicode property
for a character with a code point greater than 0x10ffff (the Unicode maximum)
caused a crash.

5. If a lookbehind assertion that contained a back reference to a group
appearing later in the pattern was compiled with the PCRE2_ANCHORED option,
undefined actions (often a segmentation fault) could occur, depending on what
other options were set. An example assertion is (?<!\1(abc)) where the
reference \1 precedes the group (abc). This fixes oss-fuzz issue 865.

6. Added the PCRE2_INFO_FRAMESIZE item to pcre2_pattern_info() and arranged for
pcre2test to use it to output the frame size when the "framesize" modifier is
given.

7. Reworked the recursive pattern matching in the JIT compiler to follow the
interpreter changes.

8. When the zero_terminate modifier was specified on a pcre2test subject line
for global matching, unpredictable things could happen. For example, in UTF-8
mode, the pattern //g,zero_terminate read random memory when matched against an
empty string with zero_terminate. This was a bug in pcre2test, not the library.

9. Moved some Windows-specific code in pcre2grep (introduced in 10.23/13) out
of the section that is compiled when Unix-style directory scanning is
available, and into a new section that is always compiled for Windows.

10. In pcre2test, explicitly close the file after an error during serialization
or deserialization (the "load" or "save" commands).

11. Fix memory leak in pcre2_serialize_decode() when the input is invalid.

12. Fix potential NULL dereference in pcre2_callout_enumerate() if called with
a NULL pattern pointer when Unicode support is available.

13. When the 32-bit library was being tested by pcre2test, error messages that
were longer than 64 code units could cause a buffer overflow. This was a bug in
pcre2test.

14. The alternative matching function, pcre2_dfa_match() misbehaved if it
encountered a character class with a possessive repeat, for example [a-f]{3}+.

15. The depth (formerly recursion) limit now applies to DFA matching (as
of 10.23/36); pcre2test has been upgraded so that \=find_limits works with DFA
matching to find the minimum value for this limit.

16. Since 10.21, if pcre2_match() was called with a null context, default
memory allocation functions were used instead of whatever was used when the
pattern was compiled.

17. Changes to the pcre2test "memory" modifier on a subject line. These apply
only to pcre2_match():

  (a) Warn if null_context is set on both pattern and subject, because the
      memory details cannot then be shown.

  (b) Remember (up to a certain number of) memory allocations and their
      lengths, and list only the lengths, so as to be system-independent.
      (In practice, the new interpreter never has more than 2 blocks allocated
      simultaneously.)

18. Make pcre2test detect an error return from pcre2_get_error_message(), give
a message, and abandon the run (this would have detected #13 above).

19. Implemented PCRE2_ENDANCHORED.

20. Applied Jason Hood's patches (slightly modified) to pcre2grep, to implement
the --output=text (-O) option and the inbuilt callout echo.

21. Extend auto-anchoring etc. to ignore groups with a zero qualifier and
single-branch conditions with a false condition (e.g. DEFINE) at the start of a
branch. For example, /(?(DEFINE)...)^A/ and /(...){0}^B/ are now flagged as
anchored.

22. Added an explicit limit on the amount of heap used by pcre2_match(), set by
pcre2_set_heap_limit() or (*LIMIT_HEAP=xxx). Upgraded pcre2test to show the
heap limit along with other pattern information, and to find the minimum when
the find_limits modifier is set.

23. Write to the last 8 bytes of the pcre2_real_code structure when a compiled
pattern is set up so as to initialize any padding the compiler might have
included. This avoids valgrind warnings when a compiled pattern is copied, in
particular when it is serialized.

24. Remove a redundant line of code left in accidentally a long time ago.

25. Remove a duplication typo in pcre2_tables.c

26. Correct an incorrect cast in pcre2_valid_utf.c

27. Update pcre2test, remove some unused code in pcre2_match(), and upgrade the
tests to improve coverage.

28. Some fixes/tidies as a result of looking at Coverity Scan output:

    (a) Typo: ">" should be ">=" in opcode check in pcre2_auto_possess.c.
    (b) Added some casts to avoid "suspicious implicit sign extension".
    (c) Resource leaks in pcre2test in rare error cases.
    (d) Avoid warning for never-use case OP_TABLE_LENGTH which is just a fudge
        for checking at compile time that tables are the right size.
    (e) Add missing "fall through" comment.

29. Implemented PCRE2_EXTENDED_MORE and related /xx and (?xx) features.

30. Implement (?n: for PCRE2_NO_AUTO_CAPTURE, because Perl now has this.

31. If more than one of "push", "pushcopy", or "pushtablescopy" were set in
pcre2test, a crash could occur.

32. Make -bigstack in RunTest allocate a 64MiB stack (instead of 16MiB) so
that all the tests can run with clang's sanitizing options.

33. Implement extra compile options in the compile context and add the first
one: PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES.

34. Implement newline type PCRE2_NEWLINE_NUL.

35. A lookbehind assertion that had a zero-length branch caused undefined
behaviour when processed by pcre2_dfa_match(). This is oss-fuzz issue 1859.

36. The match limit value now also applies to pcre2_dfa_match() as there are
patterns that can use up a lot of resources without necessarily recursing very
deeply. (Compare item 10.23/36.) This should fix oss-fuzz #1761.

37. Implement PCRE2_EXTRA_BAD_ESCAPE_IS_LITERAL.

38. Fix returned offsets from regexec() when REG_STARTEND is used with a
starting offset greater than zero.

39. Implement REG_PEND (GNU extension) for the POSIX wrapper.

40. Implement the subject_literal modifier in pcre2test, and allow jitstack on
pattern lines.

41. Implement PCRE2_LITERAL and use it to support REG_NOSPEC.

42. Implement PCRE2_EXTRA_MATCH_LINE and PCRE2_EXTRA_MATCH_WORD for the benefit
of pcre2grep.

43. Re-implement pcre2grep's -F, -w, and -x options using PCRE2_LITERAL,
PCRE2_EXTRA_MATCH_WORD, and PCRE2_EXTRA_MATCH_LINE. This fixes two bugs:

    (a) The -F option did not work for fixed strings containing \E.
    (b) The -w option did not work for patterns with multiple branches.

44. Added configuration options for the SELinux compatible execmem allocator in
JIT.

45. Increased the limit for searching for a "must be present" code unit in
subjects from 1000 to 2000 for 8-bit searches, since they use memchr() and are
much faster.

46. Arrange for anchored patterns to record and use "first code unit" data,
because this can give a fast "no match" without searching for a "required code
unit". Previously only non-anchored patterns did this.

47. Upgraded the Unicode tables from Unicode 8.0.0 to Unicode 10.0.0.

48. Add the callout_no_where modifier to pcre2test.

49. Update extended grapheme breaking rules to the latest set that are in
Unicode Standard Annex #29.

50. Added experimental foreign pattern conversion facilities
(pcre2_pattern_convert() and friends).

51. Change the macro FWRITE, used in pcre2grep, to FWRITE_IGNORE because FWRITE
is defined in a system header in cygwin. Also modified some of the #ifdefs in
pcre2grep related to Windows and Cygwin support.

52. Change 3(g) for 10.23 was a bit too zealous. If a hyphen that follows a
character class is the last character in the class, Perl does not give a
warning. PCRE2 now also treats this as a literal.

53. Related to 52, though PCRE2 was throwing an error for [[:digit:]-X] it was
not doing so for [\d-X] (and similar escapes), as is documented.

54. Fixed a MIPS issue in the JIT compiler reported by Joshua Kinard.

55. Fixed a "maybe uninitialized" warning for class_uchardata in \p handling in
pcre2_compile() which could never actually trigger (code should have been cut
out when Unicode support is disabled).


Version 10.23 14-February-2017
------------------------------

1. Extended pcre2test with the utf8_input modifier so that it is able to
generate all possible 16-bit and 32-bit code unit values in non-UTF modes.

2. In any wide-character mode (8-bit UTF or any 16-bit or 32-bit mode), without
PCRE2_UCP set, a negative character type such as \D in a positive class should
cause all characters greater than 255 to match, whatever else is in the class.
There was a bug that caused this not to happen if a Unicode property item was
added to such a class, for example [\D\P{Nd}] or [\W\pL].

3. There has been a major re-factoring of the pcre2_compile.c file. Most syntax
checking is now done in the pre-pass that identifies capturing groups. This has
reduced the amount of duplication and made the code tidier. While doing this,
some minor bugs and Perl incompatibilities were fixed, including:

  (a) \Q\E in the middle of a quantifier such as A+\Q\E+ is now ignored instead
      of giving an invalid quantifier error.

  (b) {0} can now be used after a group in a lookbehind assertion; previously
      this caused an "assertion is not fixed length" error.

  (c) Perl always treats (?(DEFINE) as a "define" group, even if a group with
      the name "DEFINE" exists. PCRE2 now does likewise.

  (d) A recursion condition test such as (?(R2)...) must now refer to an
      existing subpattern.

  (e) A conditional recursion test such as (?(R)...) misbehaved if there was a
      group whose name began with "R".

  (f) When testing zero-terminated patterns under valgrind, the terminating
      zero is now marked "no access". This catches bugs that would otherwise
      show up only with non-zero-terminated patterns.

  (g) A hyphen appearing immediately after a POSIX character class (for example
      /[[:ascii:]-z]/) now generates an error. Perl does accept this as a
      literal, but gives a warning, so it seems best to fail it in PCRE.

  (h) An empty \Q\E sequence may appear after a callout that precedes an
      assertion condition (it is, of course, ignored).

One effect of the refactoring is that some error numbers and messages have
changed, and the pattern offset given for compiling errors is not always the
right-most character that has been read. In particular, for a variable-length
lookbehind assertion it now points to the start of the assertion. Another
change is that when a callout appears before a group, the "length of next
pattern item" that is passed now just gives the length of the opening
parenthesis item, not the length of the whole group. A length of zero is now
given only for a callout at the end of the pattern. Automatic callouts are no
longer inserted before and after explicit callouts in the pattern.

A number of bugs in the refactored code were subsequently fixed during testing
before release, but after the code was made available in the repository. Many
of the bugs were discovered by fuzzing testing. Several of them were related to
the change from assuming a zero-terminated pattern (which previously had
required non-zero terminated strings to be copied). These bugs were never in
fully released code, but are noted here for the record.

  (a) An overall recursion such as (?0) inside a lookbehind assertion was not
      being diagnosed as an error.

  (b) In utf mode, the length of a *MARK (or other verb) name was being checked
      in characters instead of code units, which could lead to bad code being
      compiled, leading to unpredictable behaviour.

  (c) In extended /x mode, characters whose code was greater than 255 caused
      a lookup outside one of the global tables. A similar bug existed for wide
      characters in *VERB names.

  (d) The amount of memory needed for a compiled pattern was miscalculated if a
      lookbehind contained more than one toplevel branch and the first branch
      was of length zero.

  (e) In UTF-8 or UTF-16 modes with PCRE2_EXTENDED (/x) set and a non-zero-
      terminated pattern, if a # comment ran on to the end of the pattern, one
      or more code units past the end were being read.

  (f) An unterminated repeat at the end of a non-zero-terminated pattern (e.g.
      "{2,2") could cause reading beyond the pattern.

  (g) When reading a callout string, if the end delimiter was at the end of the
      pattern one further code unit was read.

  (h) An unterminated number after \g' could cause reading beyond the pattern.

  (i) An insufficient memory size was being computed for compiling with
      PCRE2_AUTO_CALLOUT.

  (j) A conditional group with an assertion condition used more memory than was
      allowed for it during parsing, so too many of them could therefore
      overrun a buffer.

  (k) If parsing a pattern exactly filled the buffer, the internal test for
      overrun did not check when the final META_END item was added.

  (l) If a lookbehind contained a subroutine call, and the called group
      contained an option setting such as (?s), and the PCRE2_ANCHORED option
      was set, unpredictable behaviour could occur. The underlying bug was
      incorrect code and insufficient checking while searching for the end of
      the called subroutine in the parsed pattern.

  (m) Quantifiers following (*VERB)s were not being diagnosed as errors.

  (n) The use of \Q...\E in a (*VERB) name when PCRE2_ALT_VERBNAMES and
      PCRE2_AUTO_CALLOUT were both specified caused undetermined behaviour.

  (o) If \Q was preceded by a quantified item, and the following \E was
      followed by '?' or '+', and there was at least one literal character
      between them, an internal error "unexpected repeat" occurred (example:
      /.+\QX\E+/).

  (p) A buffer overflow could occur while sorting the names in the group name
      list (depending on the order in which the names were seen).

  (q) A conditional group that started with a callout was not doing the right
      check for a following assertion, leading to compiling bad code. Example:
      /(?(C'XX))?!XX/

  (r) If a character whose code point was greater than 0xffff appeared within
      a lookbehind that was within another lookbehind, the calculation of the
      lookbehind length went wrong and could provoke an internal error.

  (t) The sequence \E- or \Q\E- after a POSIX class in a character class caused
      an internal error. Now the hyphen is treated as a literal.

4. Back references are now permitted in lookbehind assertions when there are
no duplicated group numbers (that is, (?| has not been used), and, if the
reference is by name, there is only one group of that name. The referenced
group must, of course be of fixed length.

5. pcre2test has been upgraded so that, when run under valgrind with valgrind
support enabled, reading past the end of the pattern is detected, both when
compiling and during callout processing.

6. \g{+<number>} (e.g. \g{+2} ) is now supported. It is a "forward back
reference" and can be useful in repetitions (compare \g{-<number>} ). Perl does
not recognize this syntax.

7. Automatic callouts are no longer generated before and after callouts in the
pattern.

8. When pcre2test was outputing information from a callout, the caret indicator
for the current position in the subject line was incorrect if it was after an
escape sequence for a character whose code point was greater than \x{ff}.

9. Change 19 for 10.22 had a typo (PCRE_STATIC_RUNTIME should be
PCRE2_STATIC_RUNTIME). Fix from David Gaussmann.

10. Added --max-buffer-size to pcre2grep, to allow for automatic buffer
expansion when long lines are encountered. Original patch by Dmitry
Cherniachenko.

11. If pcre2grep was compiled with JIT support, but the library was compiled
without it (something that neither ./configure nor CMake allow, but it can be
done by editing config.h), pcre2grep was giving a JIT error. Now it detects
this situation and does not try to use JIT.

12. Added some "const" qualifiers to variables in pcre2grep.

13. Added Dmitry Cherniachenko's patch for colouring output in Windows
(untested by me). Also, look for GREP_COLOUR or GREP_COLOR if the environment
variables PCRE2GREP_COLOUR and PCRE2GREP_COLOR are not found.

14. Add the -t (grand total) option to pcre2grep.

15. A number of bugs have been mended relating to match start-up optimizations
when the first thing in a pattern is a positive lookahead. These all applied
only when PCRE2_NO_START_OPTIMIZE was *not* set:

    (a) A pattern such as (?=.*X)X$ was incorrectly optimized as if it needed
        both an initial 'X' and a following 'X'.
    (b) Some patterns starting with an assertion that started with .* were
        incorrectly optimized as having to match at the start of the subject or
        after a newline. There are cases where this is not true, for example,
        (?=.*[A-Z])(?=.{8,16})(?!.*[\s]) matches after the start in lines that
        start with spaces. Starting .* in an assertion is no longer taken as an
        indication of matching at the start (or after a newline).

16. The "offset" modifier in pcre2test was not being ignored (as documented)
when the POSIX API was in use.

17. Added --enable-fuzz-support to "configure", causing an non-installed
library containing a test function that can be called by fuzzers to be
compiled. A non-installed  binary to run the test function locally, called
pcre2fuzzcheck is also compiled.

18. A pattern with PCRE2_DOTALL (/s) set but not PCRE2_NO_DOTSTAR_ANCHOR, and
which started with .* inside a positive lookahead was incorrectly being
compiled as implicitly anchored.

19. Removed all instances of "register" declarations, as they are considered
obsolete these days and in any case had become very haphazard.

20. Add strerror() to pcre2test for failed file opening.

21. Make pcre2test -C list valgrind support when it is enabled.

22. Add the use_length modifier to pcre2test.

23. Fix an off-by-one bug in pcre2test for the list of names for 'get' and
'copy' modifiers.

24. Add PCRE2_CALL_CONVENTION into the prototype declarations in pcre2.h as it
is apparently needed there as well as in the function definitions. (Why did
nobody ask for this in PCRE1?)

25. Change the _PCRE2_H and _PCRE2_UCP_H guard macros in the header files to
PCRE2_H_IDEMPOTENT_GUARD and PCRE2_UCP_H_IDEMPOTENT_GUARD to be more standard
compliant and unique.

26. pcre2-config --libs-posix was listing -lpcre2posix instead of
-lpcre2-posix. Also, the CMake build process was building the library with the
wrong name.

27. In pcre2test, give some offset information for errors in hex patterns.
This uses the C99 formatting sequence %td, except for MSVC which doesn't
support it - %lu is used instead.

28. Implemented pcre2_code_copy_with_tables(), and added pushtablescopy to
pcre2test for testing it.

29. Fix small memory leak in pcre2test.

30. Fix out-of-bounds read for partial matching of /./ against an empty string
when the newline type is CRLF.

31. Fix a bug in pcre2test that caused a crash when a locale was set either in
the current pattern or a previous one and a wide character was matched.

32. The appearance of \p, \P, or \X in a substitution string when
PCRE2_SUBSTITUTE_EXTENDED was set caused a segmentation fault (NULL
dereference).

33. If the starting offset was specified as greater than the subject length in
a call to pcre2_substitute() an out-of-bounds memory reference could occur.

34. When PCRE2 was compiled to use the heap instead of the stack for recursive
calls to match(), a repeated minimizing caseless back reference, or a
maximizing one where the two cases had different numbers of code units,
followed by a caseful back reference, could lose the caselessness of the first
repeated back reference (example: /(Z)(a)\2{1,2}?(?-i)\1X/i should match ZaAAZX
but didn't).

35. When a pattern is too complicated, PCRE2 gives up trying to find a minimum
matching length and just records zero. Typically this happens when there are
too many nested or recursive back references. If the limit was reached in
certain recursive cases it failed to be triggered and an internal error could
be the result.

36. The pcre2_dfa_match() function now takes note of the recursion limit for
the internal recursive calls that are used for lookrounds and recursions within
the pattern.

37. More refactoring has got rid of the internal could_be_empty_branch()
function (around 400 lines of code, including comments) by keeping track of
could-be-emptiness as the pattern is compiled instead of scanning compiled
groups. (This would have been much harder before the refactoring of #3 above.)
This lifts a restriction on the number of branches in a group (more than about
1100 would give "pattern is too complicated").

38. Add the "-ac" command line option to pcre2test as a synonym for "-pattern
auto_callout".

39. In a library with Unicode support, incorrect data was compiled for a
pattern with PCRE2_UCP set without PCRE2_UTF if a class required all wide
characters to match (for example, /[\s[:^ascii:]]/).

40. The callout_error modifier has been added to pcre2test to make it possible
to return PCRE2_ERROR_CALLOUT from a callout.

41. A minor change to pcre2grep: colour reset is now "<esc>[0m" instead of
"<esc>[00m".

42. The limit in the auto-possessification code that was intended to catch
overly-complicated patterns and not spend too much time auto-possessifying was
being reset too often, resulting in very long compile times for some patterns.
Now such patterns are no longer completely auto-possessified.

43. Applied Jason Hood's revised patch for RunTest.bat.

44. Added a new Windows script RunGrepTest.bat, courtesy of Jason Hood.

45. Minor cosmetic fix to pcre2test: move a variable that is not used under
Windows into the "not Windows" code.

46. Applied Jason Hood's patches to upgrade pcre2grep under Windows and tidy
some of the code:

  * normalised the Windows condition by ensuring WIN32 is defined;
  * enables the callout feature under Windows;
  * adds globbing (Microsoft's implementation expands quoted args),
    using a tweaked opendirectory;
  * implements the is_*_tty functions for Windows;
  * --color=always will write the ANSI sequences to file;
  * add sequences 4 (underline works on Win10) and 5 (blink as bright
    background, relatively standard on DOS/Win);
  * remove the (char *) casts for the now-const strings;
  * remove GREP_COLOUR (grep's command line allowed the 'u', but not
    the environment), parsing GREP_COLORS instead;
  * uses the current colour if not set, rather than black;
  * add print_match for the undefined case;
  * fixes a typo.

In addition, colour settings containing anything other than digits and
semicolon are ignored, and the colour controls are no longer output for empty
strings.

47. Detecting patterns that are too large inside the length-measuring loop
saves processing ridiculously long patterns to their end.

48. Ignore PCRE2_CASELESS when processing \h, \H, \v, and \V in classes as it
just wastes time. In the UTF case it can also produce redundant entries in
XCLASS lists caused by characters with multiple other cases and pairs of
characters in the same "not-x" sublists.

49. A pattern such as /(?=(a\K))/ can report the end of the match being before
its start; pcre2test was not handling this correctly when using the POSIX
interface (it was OK with the native interface).

50. In pcre2grep, ignore all JIT compile errors. This means that pcre2grep will
continue to work, falling back to interpretation if anything goes wrong with
JIT.

51. Applied patches from Christian Persch to configure.ac to make use of the
AC_USE_SYSTEM_EXTENSIONS macro and to test for functions used by the JIT
modules.

52. Minor fixes to pcre2grep from Jason Hood:
    * fixed some spacing;
    * Windows doesn't usually use single quotes, so I've added a define
      to use appropriate quotes [in an example];
    * LC_ALL was displayed as "LCC_ALL";
    * numbers 11, 12 & 13 should end in "th";
    * use double quotes in usage message.

53. When autopossessifying, skip empty branches without recursion, to reduce
stack usage for the benefit of clang with -fsanitize-address, which uses huge
stack frames. Example pattern: /X?(R||){3335}/. Fixes oss-fuzz issue 553.

54. A pattern with very many explicit back references to a group that is a long
way from the start of the pattern could take a long time to compile because
searching for the referenced group in order to find the minimum length was
being done repeatedly. Now up to 128 group minimum lengths are cached and the
attempt to find a minimum length is abandoned if there is a back reference to a
group whose number is greater than 128. (In that case, the pattern is so
complicated that this optimization probably isn't worth it.) This fixes
oss-fuzz issue 557.

55. Issue 32 for 10.22 below was not correctly fixed. If pcre2grep in multiline
mode with --only-matching matched several lines, it restarted scanning at the
next line instead of moving on to the end of the matched string, which can be
several lines after the start.

56. Applied Jason Hood's new patch for RunGrepTest.bat that updates it in line
with updates to the non-Windows version.



Version 10.22 29-July-2016
--------------------------

1. Applied Jason Hood's patches to RunTest.bat and testdata/wintestoutput3
to fix problems with running the tests under Windows.

2. Implemented a facility for quoting literal characters within hexadecimal
patterns in pcre2test, to make it easier to create patterns with just a few
non-printing characters.

3. Binary zeros are not supported in pcre2test input files. It now detects them
and gives an error.

4. Updated the valgrind parameters in RunTest: (a) changed smc-check=all to
smc-check=all-non-file; (b) changed obj:* in the suppression file to obj:??? so
that it matches only unknown objects.

5. Updated the maintenance script maint/ManyConfigTests to make it easier to
select individual groups of tests.

6. When the POSIX wrapper function regcomp() is called, the REG_NOSUB option
used to set PCRE2_NO_AUTO_CAPTURE when calling pcre2_compile(). However, this
disables the use of back references (and subroutine calls), which are supported
by other implementations of regcomp() with RE_NOSUB. Therefore, REG_NOSUB no
longer causes PCRE2_NO_AUTO_CAPTURE to be set, though it still ignores nmatch
and pmatch when regexec() is called.

7. Because of 6 above, pcre2test has been modified with a new modifier called
posix_nosub, to call regcomp() with REG_NOSUB. Previously the no_auto_capture
modifier had this effect. That option is now ignored when the POSIX API is in
use.

8. Minor tidies to the pcre2demo.c sample program, including more comments
about its 8-bit-ness.

9. Detect unmatched closing parentheses and give the error in the pre-scan
instead of later. Previously the pre-scan carried on and could give a
misleading incorrect error message. For example, /(?J)(?'a'))(?'a')/ gave a
message about invalid duplicate group names.

10. It has happened that pcre2test was accidentally linked with another POSIX
regex library instead of libpcre2-posix. In this situation, a call to regcomp()
(in the other library) may succeed, returning zero, but of course putting its
own data into the regex_t block. In one example the re_pcre2_code field was
left as NULL, which made pcre2test think it had not got a compiled POSIX regex,
so it treated the next line as another pattern line, resulting in a confusing
error message. A check has been added to pcre2test to see if the data returned
from a successful call of regcomp() are valid for PCRE2's regcomp(). If they
are not, an error message is output and the pcre2test run is abandoned. The
message points out the possibility of a mis-linking. Hopefully this will avoid
some head-scratching the next time this happens.

11. A pattern such as /(?<=((?C)0))/, which has a callout inside a lookbehind
assertion, caused pcre2test to output a very large number of spaces when the
callout was taken, making the program appearing to loop.

12. A pattern that included (*ACCEPT) in the middle of a sufficiently deeply
nested set of parentheses of sufficient size caused an overflow of the
compiling workspace (which was diagnosed, but of course is not desirable).

13. Detect missing closing parentheses during the pre-pass for group
identification.

14. Changed some integer variable types and put in a number of casts, following
a report of compiler warnings from Visual Studio 2013 and a few tests with
gcc's -Wconversion (which still throws up a lot).

15. Implemented pcre2_code_copy(), and added pushcopy and #popcopy to pcre2test
for testing it.

16. Change 66 for 10.21 introduced the use of snprintf() in PCRE2's version of
regerror(). When the error buffer is too small, my version of snprintf() puts a
binary zero in the final byte. Bug #1801 seems to show that other versions do
not do this, leading to bad output from pcre2test when it was checking for
buffer overflow. It no longer assumes a binary zero at the end of a too-small
regerror() buffer.

17. Fixed typo ("&&" for "&") in pcre2_study(). Fortunately, this could not
actually affect anything, by sheer luck.

18. Two minor fixes for MSVC compilation: (a) removal of apparently incorrect
"const" qualifiers in pcre2test and (b) defining snprintf as _snprintf for
older MSVC compilers. This has been done both in src/pcre2_internal.h for most
of the library, and also in src/pcre2posix.c, which no longer includes
pcre2_internal.h (see 24 below).

19. Applied Chris Wilson's patch (Bugzilla #1681) to CMakeLists.txt for MSVC
static compilation. Subsequently applied Chris Wilson's second patch, putting
the first patch under a new option instead of being unconditional when
PCRE_STATIC is set.

20. Updated pcre2grep to set stdout as binary when run under Windows, so as not
to convert \r\n at the ends of reflected lines into \r\r\n. This required
ensuring that other output that is written to stdout (e.g. file names) uses the
appropriate line terminator: \r\n for Windows, \n otherwise.

21. When a line is too long for pcre2grep's internal buffer, show the maximum
length in the error message.

22. Added support for string callouts to pcre2grep (Zoltan's patch with PH
additions).

23. RunTest.bat was missing a "set type" line for test 22.

24. The pcre2posix.c file was including pcre2_internal.h, and using some
"private" knowledge of the data structures. This is unnecessary; the code has
been re-factored and no longer includes pcre2_internal.h.

25. A racing condition is fixed in JIT reported by Mozilla.

26. Minor code refactor to avoid "array subscript is below array bounds"
compiler warning.

27. Minor code refactor to avoid "left shift of negative number" warning.

28. Add a bit more sanity checking to pcre2_serialize_decode() and document
that it expects trusted data.

29. Fix typo in pcre2_jit_test.c

30. Due to an oversight, pcre2grep was not making use of JIT when available.
This is now fixed.

31. The RunGrepTest script is updated to use the valgrind suppressions file
when testing with JIT under valgrind (compare 10.21/51 below). The suppressions
file is updated so that is now the same as for PCRE1: it suppresses the
Memcheck warnings Addr16 and Cond in unknown objects (that is, JIT-compiled
code). Also changed smc-check=all to smc-check=all-non-file as was done for
RunTest (see 4 above).

32. Implemented the PCRE2_NO_JIT option for pcre2_match().

33. Fix typo that gave a compiler error when JIT not supported.

34. Fix comment describing the returns from find_fixedlength().

35. Fix potential negative index in pcre2test.

36. Calls to pcre2_get_error_message() with error numbers that are never
returned by PCRE2 functions were returning empty strings. Now the error code
PCRE2_ERROR_BADDATA is returned. A facility has been added to pcre2test to
show the texts for given error numbers (i.e. to call pcre2_get_error_message()
and display what it returns) and a few representative error codes are now
checked in RunTest.

37. Added "&& !defined(__INTEL_COMPILER)" to the test for __GNUC__ in
pcre2_match.c, in anticipation that this is needed for the same reason it was
recently added to pcrecpp.cc in PCRE1.

38. Using -o with -M in pcre2grep could cause unnecessary repeated output when
the match extended over a line boundary, as it tried to find more matches "on
the same line" - but it was already over the end.

39. Allow \C in lookbehinds and DFA matching in UTF-32 mode (by converting it
to the same code as '.' when PCRE2_DOTALL is set).

40. Fix two clang compiler warnings in pcre2test when only one code unit width
is supported.

41. Upgrade RunTest to automatically re-run test 2 with a large (64MiB) stack
if it fails when running the interpreter with a 16MiB stack (and if changing
the stack size via pcre2test is possible). This avoids having to manually set a
large stack size when testing with clang.

42. Fix register overwite in JIT when SSE2 acceleration is enabled.

43. Detect integer overflow in pcre2test pattern and data repetition counts.

44. In pcre2test, ignore "allcaptures" after DFA matching.

45. Fix unaligned accesses on x86. Patch by Marc Mutz.

46. Fix some more clang compiler warnings.


Version 10.21 12-January-2016
-----------------------------

1. Improve matching speed of patterns starting with + or * in JIT.

2. Use memchr() to find the first character in an unanchored match in 8-bit
mode in the interpreter. This gives a significant speed improvement.

3. Removed a redundant copy of the opcode_possessify table in the
pcre2_auto_possessify.c source.

4. Fix typos in dftables.c for z/OS.

5. Change 36 for 10.20 broke the handling of [[:>:]] and [[:<:]] in that
processing them could involve a buffer overflow if the following character was
an opening parenthesis.

6. Change 36 for 10.20 also introduced a bug in processing this pattern:
/((?x)(*:0))#(?'/. Specifically: if a setting of (?x) was followed by a (*MARK)
setting (which (*:0) is), then (?x) did not get unset at the end of its group
during the scan for named groups, and hence the external # was incorrectly
treated as a comment and the invalid (?' at the end of the pattern was not
diagnosed. This caused a buffer overflow during the real compile. This bug was
discovered by Karl Skomski with the LLVM fuzzer.

7. Moved the pcre2_find_bracket() function from src/pcre2_compile.c into its
own source module to avoid a circular dependency between src/pcre2_compile.c
and src/pcre2_study.c

8. A callout with a string argument containing an opening square bracket, for
example /(?C$[$)(?<]/, was incorrectly processed and could provoke a buffer
overflow. This bug was discovered by Karl Skomski with the LLVM fuzzer.

9. The handling of callouts during the pre-pass for named group identification
has been tightened up.

10. The quantifier {1} can be ignored, whether greedy, non-greedy, or
possessive. This is a very minor optimization.

11. A possessively repeated conditional group that could match an empty string,
for example, /(?(R))*+/, was incorrectly compiled.

12. The Unicode tables have been updated to Unicode 8.0.0 (thanks to Christian
Persch).

13. An empty comment (?#) in a pattern was incorrectly processed and could
provoke a buffer overflow. This bug was discovered by Karl Skomski with the
LLVM fuzzer.

14. Fix infinite recursion in the JIT compiler when certain patterns such as
/(?:|a|){100}x/ are analysed.

15. Some patterns with character classes involving [: and \\ were incorrectly
compiled and could cause reading from uninitialized memory or an incorrect
error diagnosis. Examples are: /[[:\\](?<[::]/ and /[[:\\](?'abc')[a:]. The
first of these bugs was discovered by Karl Skomski with the LLVM fuzzer.

16. Pathological patterns containing many nested occurrences of [: caused
pcre2_compile() to run for a very long time. This bug was found by the LLVM
fuzzer.

17. A missing closing parenthesis for a callout with a string argument was not
being diagnosed, possibly leading to a buffer overflow. This bug was found by
the LLVM fuzzer.

18. A conditional group with only one branch has an implicit empty alternative
branch and must therefore be treated as potentially matching an empty string.

19. If (?R was followed by - or + incorrect behaviour happened instead of a
diagnostic. This bug was discovered by Karl Skomski with the LLVM fuzzer.

20. Another bug that was introduced by change 36 for 10.20: conditional groups
whose condition was an assertion preceded by an explicit callout with a string
argument might be incorrectly processed, especially if the string contained \Q.
This bug was discovered by Karl Skomski with the LLVM fuzzer.

21. Compiling PCRE2 with the sanitize options of clang showed up a number of
very pedantic coding infelicities and a buffer overflow while checking a UTF-8
string if the final multi-byte UTF-8 character was truncated.

22. For Perl compatibility in EBCDIC environments, ranges such as a-z in a
class, where both values are literal letters in the same case, omit the
non-letter EBCDIC code points within the range.

23. Finding the minimum matching length of complex patterns with back
references and/or recursions can take a long time. There is now a cut-off that
gives up trying to find a minimum length when things get too complex.

24. An optimization has been added that speeds up finding the minimum matching
length for patterns containing repeated capturing groups or recursions.

25. If a pattern contained a back reference to a group whose number was
duplicated as a result of appearing in a (?|...) group, the computation of the
minimum matching length gave a wrong result, which could cause incorrect "no
match" errors. For such patterns, a minimum matching length cannot at present
be computed.

26. Added a check for integer overflow in conditions (?(<digits>) and
(?(R<digits>). This omission was discovered by Karl Skomski with the LLVM
fuzzer.

27. Fixed an issue when \p{Any} inside an xclass did not read the current
character.

28. If pcre2grep was given the -q option with -c or -l, or when handling a
binary file, it incorrectly wrote output to stdout.

29. The JIT compiler did not restore the control verb head in case of *THEN
control verbs. This issue was found by Karl Skomski with a custom LLVM fuzzer.

30. The way recursive references such as (?3) are compiled has been re-written
because the old way was the cause of many issues. Now, conversion of the group
number into a pattern offset does not happen until the pattern has been
completely compiled. This does mean that detection of all infinitely looping
recursions is postponed till match time. In the past, some easy ones were
detected at compile time. This re-writing was done in response to yet another
bug found by the LLVM fuzzer.

31. A test for a back reference to a non-existent group was missing for items
such as \987. This caused incorrect code to be compiled. This issue was found
by Karl Skomski with a custom LLVM fuzzer.

32. Error messages for syntax errors following \g and \k were giving inaccurate
offsets in the pattern.

33. Improve the performance of starting single character repetitions in JIT.

34. (*LIMIT_MATCH=) now gives an error instead of setting the value to 0.

35. Error messages for syntax errors in *LIMIT_MATCH and *LIMIT_RECURSION now
give the right offset instead of zero.

36. The JIT compiler should not check repeats after a {0,1} repeat byte code.
This issue was found by Karl Skomski with a custom LLVM fuzzer.

37. The JIT compiler should restore the control chain for empty possessive
repeats. This issue was found by Karl Skomski with a custom LLVM fuzzer.

38. A bug which was introduced by the single character repetition optimization
was fixed.

39. Match limit check added to recursion. This issue was found by Karl Skomski
with a custom LLVM fuzzer.

40. Arrange for the UTF check in pcre2_match() and pcre2_dfa_match() to look
only at the part of the subject that is relevant when the starting offset is
non-zero.

41. Improve first character match in JIT with SSE2 on x86.

42. Fix two assertion fails in JIT. These issues were found by Karl Skomski
with a custom LLVM fuzzer.

43. Correct the setting of CMAKE_C_FLAGS in CMakeLists.txt (patch from Roy Ivy
III).

44. Fix bug in RunTest.bat for new test 14, and adjust the script for the added
test (there are now 20 in total).

45. Fixed a corner case of range optimization in JIT.

46. Add the ${*MARK} facility to pcre2_substitute().

47. Modifier lists in pcre2test were splitting at spaces without the required
commas.

48. Implemented PCRE2_ALT_VERBNAMES.

49. Fixed two issues in JIT. These were found by Karl Skomski with a custom
LLVM fuzzer.

50. The pcre2test program has been extended by adding the #newline_default
command. This has made it possible to run the standard tests when PCRE2 is
compiled with either CR or CRLF as the default newline convention. As part of
this work, the new command was added to several test files and the testing
scripts were modified. The pcre2grep tests can now also be run when there is no
LF in the default newline convention.

51. The RunTest script has been modified so that, when JIT is used and valgrind
is specified, a valgrind suppressions file is set up to ignore "Invalid read of
size 16" errors because these are false positives when the hardware supports
the SSE2 instruction set.

52. It is now possible to have comment lines amid the subject strings in
pcre2test (and perltest.sh) input.

53. Implemented PCRE2_USE_OFFSET_LIMIT and pcre2_set_offset_limit().

54. Add the null_context modifier to pcre2test so that calling pcre2_compile()
and the matching functions with NULL contexts can be tested.

55. Implemented PCRE2_SUBSTITUTE_EXTENDED.

56. In a character class such as [\W\p{Any}] where both a negative-type escape
("not a word character") and a property escape were present, the property
escape was being ignored.

57. Fixed integer overflow for patterns whose minimum matching length is very,
very large.

58. Implemented --never-backslash-C.

59. Change 55 above introduced a bug by which certain patterns provoked the
erroneous error "\ at end of pattern".

60. The special sequences [[:<:]] and [[:>:]] gave rise to incorrect compiling
errors or other strange effects if compiled in UCP mode. Found with libFuzzer
and AddressSanitizer.

61. Whitespace at the end of a pcre2test pattern line caused a spurious error
message if there were only single-character modifiers. It should be ignored.

62. The use of PCRE2_NO_AUTO_CAPTURE could cause incorrect compilation results
or segmentation errors for some patterns. Found with libFuzzer and
AddressSanitizer.

63. Very long names in (*MARK) or (*THEN) etc. items could provoke a buffer
overflow.

64. Improve error message for overly-complicated patterns.

65. Implemented an optional replication feature for patterns in pcre2test, to
make it easier to test long repetitive patterns. The tests for 63 above are
converted to use the new feature.

66. In the POSIX wrapper, if regerror() was given too small a buffer, it could
misbehave.

67. In pcre2_substitute() in UTF mode, the UTF validity check on the
replacement string was happening before the length setting when the replacement
string was zero-terminated.

68. In pcre2_substitute() in UTF mode, PCRE2_NO_UTF_CHECK can be set for the
second and subsequent calls to pcre2_match().

69. There was no check for integer overflow for a replacement group number in
pcre2_substitute(). An added check for a number greater than the largest group
number in the pattern means this is not now needed.

70. The PCRE2-specific VERSION condition didn't work correctly if only one
digit was given after the decimal point, or if more than two digits were given.
It now works with one or two digits, and gives a compile time error if more are
given.

71. In pcre2_substitute() there was the possibility of reading one code unit
beyond the end of the replacement string.

72. The code for checking a subject's UTF-32 validity for a pattern with a
lookbehind involved an out-of-bounds pointer, which could potentially cause
trouble in some environments.

73. The maximum lookbehind length was incorrectly calculated for patterns such
as /(?<=(a)(?-1))x/ which have a recursion within a backreference.

74. Give an error if a lookbehind assertion is longer than 65535 code units.

75. Give an error in pcre2_substitute() if a match ends before it starts (as a
result of the use of \K).

76. Check the length of subpattern names and the names in (*MARK:xx) etc.
dynamically to avoid the possibility of integer overflow.

77. Implement pcre2_set_max_pattern_length() so that programs can restrict the
size of patterns that they are prepared to handle.

78. (*NO_AUTO_POSSESS) was not working.

79. Adding group information caching improves the speed of compiling when
checking whether a group has a fixed length and/or could match an empty string,
especially when recursion or subroutine calls are involved. However, this
cannot be used when (?| is present in the pattern because the same number may
be used for groups of different sizes. To catch runaway patterns in this
situation, counts have been introduced to the functions that scan for empty
branches or compute fixed lengths.

80. Allow for the possibility of the size of the nest_save structure not being
a factor of the size of the compiling workspace (it currently is).

81. Check for integer overflow in minimum length calculation and cap it at
65535.

82. Small optimizations in code for finding the minimum matching length.

83. Lock out configuring for EBCDIC with non-8-bit libraries.

84. Test for error code <= 0 in regerror().

85. Check for too many replacements (more than INT_MAX) in pcre2_substitute().

86. Avoid the possibility of computing with an out-of-bounds pointer (though
not dereferencing it) while handling lookbehind assertions.

87. Failure to get memory for the match data in regcomp() is now given as a
regcomp() error instead of waiting for regexec() to pick it up.

88. In pcre2_substitute(), ensure that CRLF is not split when it is a valid
newline sequence.

89. Paranoid check in regcomp() for bad error code from pcre2_compile().

90. Run test 8 (internal offsets and code sizes) for link sizes 3 and 4 as well
as for link size 2.

91. Document that JIT has a limit on pattern size, and give more information
about JIT compile failures in pcre2test.

92. Implement PCRE2_INFO_HASBACKSLASHC.

93. Re-arrange valgrind support code in pcre2test to avoid spurious reports
with JIT (possibly caused by SSE2?).

94. Support offset_limit in JIT.

95. A sequence such as [[:punct:]b] that is, a POSIX character class followed
by a single ASCII character in a class item, was incorrectly compiled in UCP
mode. The POSIX class got lost, but only if the single character followed it.

96. [:punct:] in UCP mode was matching some characters in the range 128-255
that should not have been matched.

97. If [:^ascii:] or [:^xdigit:] are present in a non-negated class, all
characters with code points greater than 255 are in the class. When a Unicode
property was also in the class (if PCRE2_UCP is set, escapes such as \w are
turned into Unicode properties), wide characters were not correctly handled,
and could fail to match.

98. In pcre2test, make the "startoffset" modifier a synonym of "offset",
because it sets the "startoffset" parameter for pcre2_match().

99. If PCRE2_AUTO_CALLOUT was set on a pattern that had a (?# comment between
an item and its qualifier (for example, A(?#comment)?B) pcre2_compile()
misbehaved. This bug was found by the LLVM fuzzer.

100. The error for an invalid UTF pattern string always gave the code unit
offset as zero instead of where the invalidity was found.

101. Further to 97 above, negated classes such as [^[:^ascii:]\d] were also not
working correctly in UCP mode.

102. Similar to 99 above, if an isolated \E was present between an item and its
qualifier when PCRE2_AUTO_CALLOUT was set, pcre2_compile() misbehaved. This bug
was found by the LLVM fuzzer.

103. The POSIX wrapper function regexec() crashed if the option REG_STARTEND
was set when the pmatch argument was NULL. It now returns REG_INVARG.

104. Allow for up to 32-bit numbers in the ordin() function in pcre2grep.

105. An empty \Q\E sequence between an item and its qualifier caused
pcre2_compile() to misbehave when auto callouts were enabled. This bug
was found by the LLVM fuzzer.

106. If both PCRE2_ALT_VERBNAMES and PCRE2_EXTENDED were set, and a (*MARK) or
other verb "name" ended with whitespace immediately before the closing
parenthesis, pcre2_compile() misbehaved. Example: /(*:abc )/, but only when
both those options were set.

107. In a number of places pcre2_compile() was not handling NULL characters
correctly, and pcre2test with the "bincode" modifier was not always correctly
displaying fields containing NULLS:

   (a) Within /x extended #-comments
   (b) Within the "name" part of (*MARK) and other *verbs
   (c) Within the text argument of a callout

108. If a pattern that was compiled with PCRE2_EXTENDED started with white
space or a #-type comment that was followed by (?-x), which turns off
PCRE2_EXTENDED, and there was no subsequent (?x) to turn it on again,
pcre2_compile() assumed that (?-x) applied to the whole pattern and
consequently mis-compiled it. This bug was found by the LLVM fuzzer. The fix
for this bug means that a setting of any of the (?imsxJU) options at the start
of a pattern is no longer transferred to the options that are returned by
PCRE2_INFO_ALLOPTIONS. In fact, this was an anachronism that should have
changed when the effects of those options were all moved to compile time.

109. An escaped closing parenthesis in the "name" part of a (*verb) when
PCRE2_ALT_VERBNAMES was set caused pcre2_compile() to malfunction. This bug
was found by the LLVM fuzzer.

110. Implemented PCRE2_SUBSTITUTE_UNSET_EMPTY, and updated pcre2test to make it
possible to test it.

111. "Harden" pcre2test against ridiculously large values in modifiers and
command line arguments.

112. Implemented PCRE2_SUBSTITUTE_UNKNOWN_UNSET and PCRE2_SUBSTITUTE_OVERFLOW_
LENGTH.

113. Fix printing of *MARK names that contain binary zeroes in pcre2test.


Version 10.20 30-June-2015
--------------------------

1. Callouts with string arguments have been added.

2. Assertion code generator in JIT has been optimized.

3. The invalid pattern (?(?C) has a missing assertion condition at the end. The
pcre2_compile() function read past the end of the input before diagnosing an
error. This bug was discovered by the LLVM fuzzer.

4. Implemented pcre2_callout_enumerate().

5. Fix JIT compilation of conditional blocks whose assertion is converted to
(*FAIL). E.g: /(?(?!))/.

6. The pattern /(?(?!)^)/ caused references to random memory. This bug was
discovered by the LLVM fuzzer.

7. The assertion (?!) is optimized to (*FAIL). This was not handled correctly
when this assertion was used as a condition, for example (?(?!)a|b). In
pcre2_match() it worked by luck; in pcre2_dfa_match() it gave an incorrect
error about an unsupported item.

8. For some types of pattern, for example /Z*(|d*){216}/, the auto-
possessification code could take exponential time to complete. A recursion
depth limit of 1000 has been imposed to limit the resources used by this
optimization. This infelicity was discovered by the LLVM fuzzer.

9. A pattern such as /(*UTF)[\S\V\H]/, which contains a negated special class
such as \S in non-UCP mode, explicit wide characters (> 255) can be ignored
because \S ensures they are all in the class. The code for doing this was
interacting badly with the code for computing the amount of space needed to
compile the pattern, leading to a buffer overflow. This bug was discovered by
the LLVM fuzzer.

10. A pattern such as /((?2)+)((?1))/ which has mutual recursion nested inside
other kinds of group caused stack overflow at compile time. This bug was
discovered by the LLVM fuzzer.

11. A pattern such as /(?1)(?#?'){8}(a)/ which had a parenthesized comment
between a subroutine call and its quantifier was incorrectly compiled, leading
to buffer overflow or other errors. This bug was discovered by the LLVM fuzzer.

12. The illegal pattern /(?(?<E>.*!.*)?)/ was not being diagnosed as missing an
assertion after (?(. The code was failing to check the character after (?(?<
for the ! or = that would indicate a lookbehind assertion. This bug was
discovered by the LLVM fuzzer.

13. A pattern such as /X((?2)()*+){2}+/ which has a possessive quantifier with
a fixed maximum following a group that contains a subroutine reference was
incorrectly compiled and could trigger buffer overflow. This bug was discovered
by the LLVM fuzzer.

14. Negative relative recursive references such as (?-7) to non-existent
subpatterns were not being diagnosed and could lead to unpredictable behaviour.
This bug was discovered by the LLVM fuzzer.

15. The bug fixed in 14 was due to an integer variable that was unsigned when
it should have been signed. Some other "int" variables, having been checked,
have either been changed to uint32_t or commented as "must be signed".

16. A mutual recursion within a lookbehind assertion such as (?<=((?2))((?1)))
caused a stack overflow instead of the diagnosis of a non-fixed length
lookbehind assertion. This bug was discovered by the LLVM fuzzer.

17. The use of \K in a positive lookbehind assertion in a non-anchored pattern
(e.g. /(?<=\Ka)/) could make pcre2grep loop.

18. There was a similar problem to 17 in pcre2test for global matches, though
the code there did catch the loop.

19. If a greedy quantified \X was preceded by \C in UTF mode (e.g. \C\X*),
and a subsequent item in the pattern caused a non-match, backtracking over the
repeated \X did not stop, but carried on past the start of the subject, causing
reference to random memory and/or a segfault. There were also some other cases
where backtracking after \C could crash. This set of bugs was discovered by the
LLVM fuzzer.

20. The function for finding the minimum length of a matching string could take
a very long time if mutual recursion was present many times in a pattern, for
example, /((?2){73}(?2))((?1))/. A better mutual recursion detection method has
been implemented. This infelicity was discovered by the LLVM fuzzer.

21. Implemented PCRE2_NEVER_BACKSLASH_C.

22. The feature for string replication in pcre2test could read from freed
memory if the replication required a buffer to be extended, and it was not
working properly in 16-bit and 32-bit modes. This issue was discovered by a
fuzzer: see http://lcamtuf.coredump.cx/afl/.

23. Added the PCRE2_ALT_CIRCUMFLEX option.

24. Adjust the treatment of \8 and \9 to be the same as the current Perl
behaviour.

25. Static linking against the PCRE2 library using the pkg-config module was
failing on missing pthread symbols.

26. If a group that contained a recursive back reference also contained a
forward reference subroutine call followed by a non-forward-reference
subroutine call, for example /.((?2)(?R)\1)()/, pcre2_compile() failed to
compile correct code, leading to undefined behaviour or an internally detected
error. This bug was discovered by the LLVM fuzzer.

27. Quantification of certain items (e.g. atomic back references) could cause
incorrect code to be compiled when recursive forward references were involved.
For example, in this pattern: /(?1)()((((((\1++))\x85)+)|))/. This bug was
discovered by the LLVM fuzzer.

28. A repeated conditional group whose condition was a reference by name caused
a buffer overflow if there was more than one group with the given name. This
bug was discovered by the LLVM fuzzer.

29. A recursive back reference by name within a group that had the same name as
another group caused a buffer overflow. For example: /(?J)(?'d'(?'d'\g{d}))/.
This bug was discovered by the LLVM fuzzer.

30. A forward reference by name to a group whose number is the same as the
current group, for example in this pattern: /(?|(\k'Pm')|(?'Pm'))/, caused a
buffer overflow at compile time. This bug was discovered by the LLVM fuzzer.

31. Fix -fsanitize=undefined warnings for left shifts of 1 by 31 (it treats 1
as an int; fixed by writing it as 1u).

32. Fix pcre2grep compile when -std=c99 is used with gcc, though it still gives
a warning for "fileno" unless -std=gnu99 us used.

33. A lookbehind assertion within a set of mutually recursive subpatterns could
provoke a buffer overflow. This bug was discovered by the LLVM fuzzer.

34. Give an error for an empty subpattern name such as (?'').

35. Make pcre2test give an error if a pattern that follows #forbud_utf contains
\P, \p, or \X.

36. The way named subpatterns are handled has been refactored. There is now a
pre-pass over the regex which does nothing other than identify named
subpatterns and count the total captures. This means that information about
named patterns is known before the rest of the compile. In particular, it means
that forward references can be checked as they are encountered. Previously, the
code for handling forward references was contorted and led to several errors in
computing the memory requirements for some patterns, leading to buffer
overflows.

37. There was no check for integer overflow in subroutine calls such as (?123).

38. The table entry for \l in EBCDIC environments was incorrect, leading to its
being treated as a literal 'l' instead of causing an error.

39. If a non-capturing group containing a conditional group that could match
an empty string was repeated, it was not identified as matching an empty string
itself. For example: /^(?:(?(1)x|)+)+$()/.

40. In an EBCDIC environment, pcretest was mishandling the escape sequences
\a and \e in test subject lines.

41. In an EBCDIC environment, \a in a pattern was converted to the ASCII
instead of the EBCDIC value.

42. The handling of \c in an EBCDIC environment has been revised so that it is
now compatible with the specification in Perl's perlebcdic page.

43. Single character repetition in JIT has been improved. 20-30% speedup
was achieved on certain patterns.

44. The EBCDIC character 0x41 is a non-breaking space, equivalent to 0xa0 in
ASCII/Unicode. This has now been added to the list of characters that are
recognized as white space in EBCDIC.

45. When PCRE2 was compiled without Unicode support, the use of \p and \P gave
an error (correctly) when used outside a class, but did not give an error
within a class.

46. \h within a class was incorrectly compiled in EBCDIC environments.

47. JIT should return with error when the compiled pattern requires
more stack space than the maximum.

48. Fixed a memory leak in pcre2grep when a locale is set.


Version 10.10 06-March-2015
---------------------------

1. When a pattern is compiled, it remembers the highest back reference so that
when matching, if the ovector is too small, extra memory can be obtained to
use instead. A conditional subpattern whose condition is a check on a capture
having happened, such as, for example in the pattern /^(?:(a)|b)(?(1)A|B)/, is
another kind of back reference, but it was not setting the highest
backreference number. This mattered only if pcre2_match() was called with an
ovector that was too small to hold the capture, and there was no other kind of
back reference (a situation which is probably quite rare). The effect of the
bug was that the condition was always treated as FALSE when the capture could
not be consulted, leading to a incorrect behaviour by pcre2_match(). This bug
has been fixed.

2. Functions for serialization and deserialization of sets of compiled patterns
have been added.

3. The value that is returned by PCRE2_INFO_SIZE has been corrected to remove
excess code units at the end of the data block that may occasionally occur if
the code for calculating the size over-estimates. This change stops the
serialization code copying uninitialized data, to which valgrind objects. The
documentation of PCRE2_INFO_SIZE was incorrect in stating that the size did not
include the general overhead. This has been corrected.

4. All code units in every slot in the table of group names are now set, again
in order to avoid accessing uninitialized data when serializing.

5. The (*NO_JIT) feature is implemented.

6. If a bug that caused pcre2_compile() to use more memory than allocated was
triggered when using valgrind, the code in (3) above passed a stupidly large
value to valgrind. This caused a crash instead of an "internal error" return.

7. A reference to a duplicated named group (either a back reference or a test
for being set in a conditional) that occurred in a part of the pattern where
PCRE2_DUPNAMES was not set caused the amount of memory needed for the pattern
to be incorrectly calculated, leading to overwriting.

8. A mutually recursive set of back references such as (\2)(\1) caused a
segfault at compile time (while trying to find the minimum matching length).
The infinite loop is now broken (with the minimum length unset, that is, zero).

9. If an assertion that was used as a condition was quantified with a minimum
of zero, matching went wrong. In particular, if the whole group had unlimited
repetition and could match an empty string, a segfault was likely. The pattern
(?(?=0)?)+ is an example that caused this. Perl allows assertions to be
quantified, but not if they are being used as conditions, so the above pattern
is faulted by Perl. PCRE2 has now been changed so that it also rejects such
patterns.

10. The error message for an invalid quantifier has been changed from "nothing
to repeat" to "quantifier does not follow a repeatable item".

11. If a bad UTF string is compiled with NO_UTF_CHECK, it may succeed, but
scanning the compiled pattern in subsequent auto-possessification can get out
of step and lead to an unknown opcode. Previously this could have caused an
infinite loop. Now it generates an "internal error" error. This is a tidyup,
not a bug fix; passing bad UTF with NO_UTF_CHECK is documented as having an
undefined outcome.

12. A UTF pattern containing a "not" match of a non-ASCII character and a
subroutine reference could loop at compile time. Example: /[^\xff]((?1))/.

13. The locale test (RunTest 3) has been upgraded. It now checks that a locale
that is found in the output of "locale -a" can actually be set by pcre2test
before it is accepted. Previously, in an environment where a locale was listed
but would not set (an example does exist), the test would "pass" without
actually doing anything. Also the fr_CA locale has been added to the list of
locales that can be used.

14. Fixed a bug in pcre2_substitute(). If a replacement string ended in a
capturing group number without parentheses, the last character was incorrectly
literally included at the end of the replacement string.

15. A possessive capturing group such as (a)*+ with a minimum repeat of zero
failed to allow the zero-repeat case if pcre2_match() was called with an
ovector too small to capture the group.

16. Improved error message in pcre2test when setting the stack size (-S) fails.

17. Fixed two bugs in CMakeLists.txt: (1) Some lines had got lost in the
transfer from PCRE1, meaning that CMake configuration failed if "build tests"
was selected. (2) The file src/pcre2_serialize.c had not been added to the list
of PCRE2 sources, which caused a failure to build pcre2test.

18. Fixed typo in pcre2_serialize.c (DECL instead of DEFN) that causes problems
only on Windows.

19. Use binary input when reading back saved serialized patterns in pcre2test.

20. Added RunTest.bat for running the tests under Windows.

21. "make distclean" was not removing config.h, a file that may be created for
use with CMake.

22. A pattern such as "((?2){0,1999}())?", which has a group containing a
forward reference repeated a large (but limited) number of times within a
repeated outer group that has a zero minimum quantifier, caused incorrect code
to be compiled, leading to the error "internal error: previously-checked
referenced subpattern not found" when an incorrect memory address was read.
This bug was reported as "heap overflow", discovered by Kai Lu of Fortinet's
FortiGuard Labs. (Added 24-March-2015: CVE-2015-2325 was given to this.)

23. A pattern such as "((?+1)(\1))/" containing a forward reference subroutine
call within a group that also contained a recursive back reference caused
incorrect code to be compiled. This bug was reported as "heap overflow",
discovered by Kai Lu of Fortinet's FortiGuard Labs. (Added 24-March-2015:
CVE-2015-2326 was given to this.)

24. Computing the size of the JIT read-only data in advance has been a source
of various issues, and new ones are still appear unfortunately. To fix
existing and future issues, size computation is eliminated from the code,
and replaced by on-demand memory allocation.

25. A pattern such as /(?i)[A-`]/, where characters in the other case are
adjacent to the end of the range, and the range contained characters with more
than one other case, caused incorrect behaviour when compiled in UTF mode. In
that example, the range a-j was left out of the class.


Version 10.00 05-January-2015
-----------------------------

Version 10.00 is the first release of PCRE2, a revised API for the PCRE
library. Changes prior to 10.00 are logged in the ChangeLog file for the old
API, up to item 20 for release 8.36.

The code of the library was heavily revised as part of the new API
implementation. Details of each and every modification were not individually
logged. In addition to the API changes, the following changes were made. They
are either new functionality, or bug fixes and other noticeable changes of
behaviour that were implemented after the code had been forked.

1. Including Unicode support at build time is now enabled by default, but it
can optionally be disabled. It is not enabled by default at run time (no
change).

2. The test program, now called pcre2test, was re-specified and almost
completely re-written. Its input is not compatible with input for pcretest.

3. Patterns may start with (*NOTEMPTY) or (*NOTEMPTY_ATSTART) to set the
PCRE2_NOTEMPTY or PCRE2_NOTEMPTY_ATSTART options for every subject line that is
matched by that pattern.

4. For the benefit of those who use PCRE2 via some other application, that is,
not writing the function calls themselves, it is possible to check the PCRE2
version by matching a pattern such as /(?(VERSION>=10)yes|no)/ against a
string such as "yesno".

5. There are case-equivalent Unicode characters whose encodings use different
numbers of code units in UTF-8. U+023A and U+2C65 are one example. (It is
theoretically possible for this to happen in UTF-16 too.) If a backreference to
a group containing one of these characters was greedily repeated, and during
the match a backtrack occurred, the subject might be backtracked by the wrong
number of code units. For example, if /^(\x{23a})\1*(.)/ is matched caselessly
(and in UTF-8 mode) against "\x{23a}\x{2c65}\x{2c65}\x{2c65}", group 2 should
capture the final character, which is the three bytes E2, B1, and A5 in UTF-8.
Incorrect backtracking meant that group 2 captured only the last two bytes.
This bug has been fixed; the new code is slower, but it is used only when the
strings matched by the repetition are not all the same length.

6. A pattern such as /()a/ was not setting the "first character must be 'a'"
information. This applied to any pattern with a group that matched no
characters, for example: /(?:(?=.)|(?<!x))a/.

7. When an (*ACCEPT) is triggered inside capturing parentheses, it arranges for
those parentheses to be closed with whatever has been captured so far. However,
it was failing to mark any other groups between the highest capture so far and
the currrent group as "unset". Thus, the ovector for those groups contained
whatever was previously there. An example is the pattern /(x)|((*ACCEPT))/ when
matched against "abcd".

8. The pcre2_substitute() function has been implemented.

9. If an assertion used as a condition was quantified with a minimum of zero
(an odd thing to do, but it happened), SIGSEGV or other misbehaviour could
occur.

10. The PCRE2_NO_DOTSTAR_ANCHOR option has been implemented.

****