pcre2/ChangeLog

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

Version 10.10 xx-xxx-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))/.


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.

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