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1  ChangeLog for PCRE  ChangeLog for PCRE
2  ------------------  ------------------
4    Version 4.5 01-Dec-03
5    ---------------------
7     1. There has been some re-arrangement of the code for the match() function so
8        that it can be compiled in a version that does not call itself recursively.
9        Instead, it keeps those local variables that need separate instances for
10        each "recursion" in a frame on the heap, and gets/frees frames whenever it
11        needs to "recurse". Keeping track of where control must go is done by means
12        of setjmp/longjmp. The whole thing is implemented by a set of macros that
13        hide most of the details from the main code, and operates only if
14        NO_RECURSE is defined while compiling pcre.c. If PCRE is built using the
15        "configure" mechanism, "--disable-stack-for-recursion" turns on this way of
16        operating.
18        To make it easier for callers to provide specially tailored get/free
19        functions for this usage, two new functions, pcre_stack_malloc, and
20        pcre_stack_free, are used. They are always called in strict stacking order,
21        and the size of block requested is always the same.
23        The PCRE_CONFIG_STACKRECURSE info parameter can be used to find out whether
24        PCRE has been compiled to use the stack or the heap for recursion. The
25        -C option of pcretest uses this to show which version is compiled.
27        A new data escape \S, is added to pcretest; it causes the amounts of store
28        obtained and freed by both kinds of malloc/free at match time to be added
29        to the output.
31     2. Changed the locale test to use "fr_FR" instead of "fr" because that's
32        what's available on my current Linux desktop machine.
34     3. When matching a UTF-8 string, the test for a valid string at the start has
35        been extended. If start_offset is not zero, PCRE now checks that it points
36        to a byte that is the start of a UTF-8 character. If not, it returns
37        PCRE_ERROR_BADUTF8_OFFSET (-11). Note: the whole string is still checked;
38        this is necessary because there may be backward assertions in the pattern.
39        When matching the same subject several times, it may save resources to use
40        PCRE_NO_UTF8_CHECK on all but the first call if the string is long.
42     4. The code for checking the validity of UTF-8 strings has been tightened so
43        that it rejects (a) strings containing 0xfe or 0xff bytes and (b) strings
44        containing "overlong sequences".
46     5. Fixed a bug (appearing twice) that I could not find any way of exploiting!
47        I had written "if ((digitab[*p++] && chtab_digit) == 0)" where the "&&"
48        should have been "&", but it just so happened that all the cases this let
49        through by mistake were picked up later in the function.
51     6. I had used a variable called "isblank" - this is a C99 function, causing
52        some compilers to warn. To avoid this, I renamed it (as "blankclass").
54     7. Cosmetic: (a) only output another newline at the end of pcretest if it is
55        prompting; (b) run "./pcretest /dev/null" at the start of the test script
56        so the version is shown; (c) stop "make test" echoing "./RunTest".
58     8. Added patches from David Burgess to enable PCRE to run on EBCDIC systems.
60     9. The prototype for memmove() for systems that don't have it was using
61        size_t, but the inclusion of the header that defines size_t was later. I've
62        moved the #includes for the C headers earlier to avoid this.
64    10. Added some adjustments to the code to make it easier to compiler on certain
65        special systems:
67          (a) Some "const" qualifiers were missing.
68          (b) Added the macro EXPORT before all exported functions; by default this
69              is defined to be empty.
70          (c) Changed the dftables auxiliary program (that builds chartables.c) so
71              that it reads its output file name as an argument instead of writing
72              to the standard output and assuming this can be redirected.
74    11. In UTF-8 mode, if a recursive reference (e.g. (?1)) followed a character
75        class containing characters with values greater than 255, PCRE compilation
76        went into a loop.
78    12. A recursive reference to a subpattern that was within another subpattern
79        that had a minimum quantifier of zero caused PCRE to crash. For example,
80        (x(y(?2))z)? provoked this bug with a subject that got as far as the
81        recursion. If the recursively-called subpattern itself had a zero repeat,
82        that was OK.
84    13. In pcretest, the buffer for reading a data line was set at 30K, but the
85        buffer into which it was copied (for escape processing) was still set at
86        1024, so long lines caused crashes.
88    14. A pattern such as /[ab]{1,3}+/ failed to compile, giving the error
89        "internal error: code overflow...". This applied to any character class
90        that was followed by a possessive quantifier.
92    15. Modified the Makefile to add libpcre.la as a prerequisite for
93        libpcreposix.la because I was told this is needed for a parallel build to
94        work.
96    16. If a pattern that contained .* following optional items at the start was
97        studied, the wrong optimizing data was generated, leading to matching
98        errors. For example, studying /[ab]*.*c/ concluded, erroneously, that any
99        matching string must start with a or b or c. The correct conclusion for
100        this pattern is that a match can start with any character.
103    Version 4.4 13-Aug-03
104    ---------------------
106     1. In UTF-8 mode, a character class containing characters with values between
107        127 and 255 was not handled correctly if the compiled pattern was studied.
108        In fixing this, I have also improved the studying algorithm for such
109        classes (slightly).
111     2. Three internal functions had redundant arguments passed to them. Removal
112        might give a very teeny performance improvement.
114     3. Documentation bug: the value of the capture_top field in a callout is *one
115        more than* the number of the hightest numbered captured substring.
117     4. The Makefile linked pcretest and pcregrep with -lpcre, which could result
118        in incorrectly linking with a previously installed version. They now link
119        explicitly with libpcre.la.
121     5. configure.in no longer needs to recognize Cygwin specially.
123     6. A problem in pcre.in for Windows platforms is fixed.
125     7. If a pattern was successfully studied, and the -d (or /D) flag was given to
126        pcretest, it used to include the size of the study block as part of its
127        output. Unfortunately, the structure contains a field that has a different
128        size on different hardware architectures. This meant that the tests that
129        showed this size failed. As the block is currently always of a fixed size,
130        this information isn't actually particularly useful in pcretest output, so
131        I have just removed it.
133     8. Three pre-processor statements accidentally did not start in column 1.
134        Sadly, there are *still* compilers around that complain, even though
135        standard C has not required this for well over a decade. Sigh.
137     9. In pcretest, the code for checking callouts passed small integers in the
138        callout_data field, which is a void * field. However, some picky compilers
139        complained about the casts involved for this on 64-bit systems. Now
140        pcretest passes the address of the small integer instead, which should get
141        rid of the warnings.
143    10. By default, when in UTF-8 mode, PCRE now checks for valid UTF-8 strings at
144        both compile and run time, and gives an error if an invalid UTF-8 sequence
145        is found. There is a option for disabling this check in cases where the
146        string is known to be correct and/or the maximum performance is wanted.
148    11. In response to a bug report, I changed one line in Makefile.in from
150            -Wl,--out-implib,.libs/lib@WIN_PREFIX@pcreposix.dll.a \
151        to
152            -Wl,--out-implib,.libs/@WIN_PREFIX@libpcreposix.dll.a \
154        to look similar to other lines, but I have no way of telling whether this
155        is the right thing to do, as I do not use Windows. No doubt I'll get told
156        if it's wrong...
159    Version 4.3 21-May-03
160    ---------------------
162    1. Two instances of @WIN_PREFIX@ omitted from the Windows targets in the
163       Makefile.
165    2. Some refactoring to improve the quality of the code:
167       (i)   The utf8_table... variables are now declared "const".
169       (ii)  The code for \cx, which used the "case flipping" table to upper case
170             lower case letters, now just substracts 32. This is ASCII-specific,
171             but the whole concept of \cx is ASCII-specific, so it seems
172             reasonable.
174       (iii) PCRE was using its character types table to recognize decimal and
175             hexadecimal digits in the pattern. This is silly, because it handles
176             only 0-9, a-f, and A-F, but the character types table is locale-
177             specific, which means strange things might happen. A private
178             table is now used for this - though it costs 256 bytes, a table is
179             much faster than multiple explicit tests. Of course, the standard
180             character types table is still used for matching digits in subject
181             strings against \d.
183       (iv)  Strictly, the identifier ESC_t is reserved by POSIX (all identifiers
184             ending in _t are). So I've renamed it as ESC_tee.
186    3. The first argument for regexec() in the POSIX wrapper should have been
187       defined as "const".
189    4. Changed pcretest to use malloc() for its buffers so that they can be
190       Electric Fenced for debugging.
192    5. There were several places in the code where, in UTF-8 mode, PCRE would try
193       to read one or more bytes before the start of the subject string. Often this
194       had no effect on PCRE's behaviour, but in some circumstances it could
195       provoke a segmentation fault.
197    6. A lookbehind at the start of a pattern in UTF-8 mode could also cause PCRE
198       to try to read one or more bytes before the start of the subject string.
200    7. A lookbehind in a pattern matched in non-UTF-8 mode on a PCRE compiled with
201       UTF-8 support could misbehave in various ways if the subject string
202       contained bytes with the 0x80 bit set and the 0x40 bit unset in a lookbehind
203       area. (PCRE was not checking for the UTF-8 mode flag, and trying to move
204       back over UTF-8 characters.)
207    Version 4.2 14-Apr-03
208    ---------------------
210    1. Typo "#if SUPPORT_UTF8" instead of "#ifdef SUPPORT_UTF8" fixed.
212    2. Changes to the building process, supplied by Ronald Landheer-Cieslak
213         [ON_WINDOWS]: new variable, "#" on non-Windows platforms
214         [NOT_ON_WINDOWS]: new variable, "#" on Windows platforms
215         [WIN_PREFIX]: new variable, "cyg" for Cygwin
216         * Makefile.in: use autoconf substitution for OBJEXT, EXEEXT, BUILD_OBJEXT
217           and BUILD_EXEEXT
218         Note: automatic setting of the BUILD variables is not yet working
219         set CPPFLAGS and BUILD_CPPFLAGS (but don't use yet) - should be used at
220           compile-time but not at link-time
221         [LINK]: use for linking executables only
222         make different versions for Windows and non-Windows
223         [LINKLIB]: new variable, copy of UNIX-style LINK, used for linking
224           libraries
225         [LINK_FOR_BUILD]: new variable
226         [OBJEXT]: use throughout
227         [EXEEXT]: use throughout
228         <winshared>: new target
229         <wininstall>: new target
230         <dftables.o>: use native compiler
231         <dftables>: use native linker
232         <install>: handle Windows platform correctly
233         <clean>: ditto
234         <check>: ditto
235         copy DLL to top builddir before testing
237       As part of these changes, -no-undefined was removed again. This was reported
238       to give trouble on HP-UX 11.0, so getting rid of it seems like a good idea
239       in any case.
241    3. Some tidies to get rid of compiler warnings:
243       . In the match_data structure, match_limit was an unsigned long int, whereas
244         match_call_count was an int. I've made them both unsigned long ints.
246       . In pcretest the fact that a const uschar * doesn't automatically cast to
247         a void * provoked a warning.
249       . Turning on some more compiler warnings threw up some "shadow" variables
250         and a few more missing casts.
252    4. If PCRE was complied with UTF-8 support, but called without the PCRE_UTF8
253       option, a class that contained a single character with a value between 128
254       and 255 (e.g. /[\xFF]/) caused PCRE to crash.
256    5. If PCRE was compiled with UTF-8 support, but called without the PCRE_UTF8
257       option, a class that contained several characters, but with at least one
258       whose value was between 128 and 255 caused PCRE to crash.
261    Version 4.1 12-Mar-03
262    ---------------------
264    1. Compiling with gcc -pedantic found a couple of places where casts were
265    needed, and a string in dftables.c that was longer than standard compilers are
266    required to support.
268    2. Compiling with Sun's compiler found a few more places where the code could
269    be tidied up in order to avoid warnings.
271    3. The variables for cross-compiling were called HOST_CC and HOST_CFLAGS; the
272    first of these names is deprecated in the latest Autoconf in favour of the name
273    CC_FOR_BUILD, because "host" is typically used to mean the system on which the
274    compiled code will be run. I can't find a reference for HOST_CFLAGS, but by
275    analogy I have changed it to CFLAGS_FOR_BUILD.
277    4. Added -no-undefined to the linking command in the Makefile, because this is
278    apparently helpful for Windows. To make it work, also added "-L. -lpcre" to the
279    linking step for the pcreposix library.
281    5. PCRE was failing to diagnose the case of two named groups with the same
282    name.
284    6. A problem with one of PCRE's optimizations was discovered. PCRE remembers a
285    literal character that is needed in the subject for a match, and scans along to
286    ensure that it is present before embarking on the full matching process. This
287    saves time in cases of nested unlimited repeats that are never going to match.
288    Problem: the scan can take a lot of time if the subject is very long (e.g.
289    megabytes), thus penalizing straightforward matches. It is now done only if the
290    amount of subject to be scanned is less than 1000 bytes.
292    7. A lesser problem with the same optimization is that it was recording the
293    first character of an anchored pattern as "needed", thus provoking a search
294    right along the subject, even when the first match of the pattern was going to
295    fail. The "needed" character is now not set for anchored patterns, unless it
296    follows something in the pattern that is of non-fixed length. Thus, it still
297    fulfils its original purpose of finding quick non-matches in cases of nested
298    unlimited repeats, but isn't used for simple anchored patterns such as /^abc/.
301    Version 4.0 17-Feb-03
302    ---------------------
304    1. If a comment in an extended regex that started immediately after a meta-item
305    extended to the end of string, PCRE compiled incorrect data. This could lead to
306    all kinds of weird effects. Example: /#/ was bad; /()#/ was bad; /a#/ was not.
308    2. Moved to autoconf 2.53 and libtool 1.4.2.
310    3. Perl 5.8 no longer needs "use utf8" for doing UTF-8 things. Consequently,
311    the special perltest8 script is no longer needed - all the tests can be run
312    from a single perltest script.
314    4. From 5.004, Perl has not included the VT character (0x0b) in the set defined
315    by \s. It has now been removed in PCRE. This means it isn't recognized as
316    whitespace in /x regexes too, which is the same as Perl. Note that the POSIX
317    class [:space:] *does* include VT, thereby creating a mess.
319    5. Added the class [:blank:] (a GNU extension from Perl 5.8) to match only
320    space and tab.
322    6. Perl 5.005 was a long time ago. It's time to amalgamate the tests that use
323    its new features into the main test script, reducing the number of scripts.
325    7. Perl 5.8 has changed the meaning of patterns like /a(?i)b/. Earlier versions
326    were backward compatible, and made the (?i) apply to the whole pattern, as if
327    /i were given. Now it behaves more logically, and applies the option setting
328    only to what follows. PCRE has been changed to follow suit. However, if it
329    finds options settings right at the start of the pattern, it extracts them into
330    the global options, as before. Thus, they show up in the info data.
332    8. Added support for the \Q...\E escape sequence. Characters in between are
333    treated as literals. This is slightly different from Perl in that $ and @ are
334    also handled as literals inside the quotes. In Perl, they will cause variable
335    interpolation. Note the following examples:
337        Pattern            PCRE matches      Perl matches
339        \Qabc$xyz\E        abc$xyz           abc followed by the contents of $xyz
340        \Qabc\$xyz\E       abc\$xyz          abc\$xyz
341        \Qabc\E\$\Qxyz\E   abc$xyz           abc$xyz
343    For compatibility with Perl, \Q...\E sequences are recognized inside character
344    classes as well as outside them.
346    9. Re-organized 3 code statements in pcretest to avoid "overflow in
347    floating-point constant arithmetic" warnings from a Microsoft compiler. Added a
348    (size_t) cast to one statement in pcretest and one in pcreposix to avoid
349    signed/unsigned warnings.
351    10. SunOS4 doesn't have strtoul(). This was used only for unpicking the -o
352    option for pcretest, so I've replaced it by a simple function that does just
353    that job.
355    11. pcregrep was ending with code 0 instead of 2 for the commands "pcregrep" or
356    "pcregrep -".
358    12. Added "possessive quantifiers" ?+, *+, ++, and {,}+ which come from Sun's
359    Java package. This provides some syntactic sugar for simple cases of what my
360    documentation calls "once-only subpatterns". A pattern such as x*+ is the same
361    as (?>x*). In other words, if what is inside (?>...) is just a single repeated
362    item, you can use this simplified notation. Note that only makes sense with
363    greedy quantifiers. Consequently, the use of the possessive quantifier forces
364    greediness, whatever the setting of the PCRE_UNGREEDY option.
366    13. A change of greediness default within a pattern was not taking effect at
367    the current level for patterns like /(b+(?U)a+)/. It did apply to parenthesized
368    subpatterns that followed. Patterns like /b+(?U)a+/ worked because the option
369    was abstracted outside.
371    14. PCRE now supports the \G assertion. It is true when the current matching
372    position is at the start point of the match. This differs from \A when the
373    starting offset is non-zero. Used with the /g option of pcretest (or similar
374    code), it works in the same way as it does for Perl's /g option. If all
375    alternatives of a regex begin with \G, the expression is anchored to the start
376    match position, and the "anchored" flag is set in the compiled expression.
378    15. Some bugs concerning the handling of certain option changes within patterns
379    have been fixed. These applied to options other than (?ims). For example,
380    "a(?x: b c )d" did not match "XabcdY" but did match "Xa b c dY". It should have
381    been the other way round. Some of this was related to change 7 above.
383    16. PCRE now gives errors for /[.x.]/ and /[=x=]/ as unsupported POSIX
384    features, as Perl does. Previously, PCRE gave the warnings only for /[[.x.]]/
385    and /[[=x=]]/. PCRE now also gives an error for /[:name:]/ because it supports
386    POSIX classes only within a class (e.g. /[[:alpha:]]/).
388    17. Added support for Perl's \C escape. This matches one byte, even in UTF8
389    mode. Unlike ".", it always matches newline, whatever the setting of
390    PCRE_DOTALL. However, PCRE does not permit \C to appear in lookbehind
391    assertions. Perl allows it, but it doesn't (in general) work because it can't
392    calculate the length of the lookbehind. At least, that's the case for Perl
393    5.8.0 - I've been told they are going to document that it doesn't work in
394    future.
396    18. Added an error diagnosis for escapes that PCRE does not support: these are
397    \L, \l, \N, \P, \p, \U, \u, and \X.
399    19. Although correctly diagnosing a missing ']' in a character class, PCRE was
400    reading past the end of the pattern in cases such as /[abcd/.
402    20. PCRE was getting more memory than necessary for patterns with classes that
403    contained both POSIX named classes and other characters, e.g. /[[:space:]abc/.
405    21. Added some code, conditional on #ifdef VPCOMPAT, to make life easier for
406    compiling PCRE for use with Virtual Pascal.
408    22. Small fix to the Makefile to make it work properly if the build is done
409    outside the source tree.
411    23. Added a new extension: a condition to go with recursion. If a conditional
412    subpattern starts with (?(R) the "true" branch is used if recursion has
413    happened, whereas the "false" branch is used only at the top level.
415    24. When there was a very long string of literal characters (over 255 bytes
416    without UTF support, over 250 bytes with UTF support), the computation of how
417    much memory was required could be incorrect, leading to segfaults or other
418    strange effects.
420    25. PCRE was incorrectly assuming anchoring (either to start of subject or to
421    start of line for a non-DOTALL pattern) when a pattern started with (.*) and
422    there was a subsequent back reference to those brackets. This meant that, for
423    example, /(.*)\d+\1/ failed to match "abc123bc". Unfortunately, it isn't
424    possible to check for precisely this case. All we can do is abandon the
425    optimization if .* occurs inside capturing brackets when there are any back
426    references whatsoever. (See below for a better fix that came later.)
428    26. The handling of the optimization for finding the first character of a
429    non-anchored pattern, and for finding a character that is required later in the
430    match were failing in some cases. This didn't break the matching; it just
431    failed to optimize when it could. The way this is done has been re-implemented.
433    27. Fixed typo in error message for invalid (?R item (it said "(?p").
435    28. Added a new feature that provides some of the functionality that Perl
436    provides with (?{...}). The facility is termed a "callout". The way it is done
437    in PCRE is for the caller to provide an optional function, by setting
438    pcre_callout to its entry point. Like pcre_malloc and pcre_free, this is a
439    global variable. By default it is unset, which disables all calling out. To get
440    the function called, the regex must include (?C) at appropriate points. This
441    is, in fact, equivalent to (?C0), and any number <= 255 may be given with (?C).
442    This provides a means of identifying different callout points. When PCRE
443    reaches such a point in the regex, if pcre_callout has been set, the external
444    function is called. It is provided with data in a structure called
445    pcre_callout_block, which is defined in pcre.h. If the function returns 0,
446    matching continues; if it returns a non-zero value, the match at the current
447    point fails. However, backtracking will occur if possible. [This was changed
448    later and other features added - see item 49 below.]
450    29. pcretest is upgraded to test the callout functionality. It provides a
451    callout function that displays information. By default, it shows the start of
452    the match and the current position in the text. There are some new data escapes
453    to vary what happens:
455        \C+         in addition, show current contents of captured substrings
456        \C-         do not supply a callout function
457        \C!n        return 1 when callout number n is reached
458        \C!n!m      return 1 when callout number n is reached for the mth time
460    30. If pcregrep was called with the -l option and just a single file name, it
461    output "<stdin>" if a match was found, instead of the file name.
463    31. Improve the efficiency of the POSIX API to PCRE. If the number of capturing
464    slots is less than POSIX_MALLOC_THRESHOLD, use a block on the stack to pass to
465    pcre_exec(). This saves a malloc/free per call. The default value of
466    POSIX_MALLOC_THRESHOLD is 10; it can be changed by --with-posix-malloc-threshold
467    when configuring.
469    32. The default maximum size of a compiled pattern is 64K. There have been a
470    few cases of people hitting this limit. The code now uses macros to handle the
471    storing of links as offsets within the compiled pattern. It defaults to 2-byte
472    links, but this can be changed to 3 or 4 bytes by --with-link-size when
473    configuring. Tests 2 and 5 work only with 2-byte links because they output
474    debugging information about compiled patterns.
476    33. Internal code re-arrangements:
478    (a) Moved the debugging function for printing out a compiled regex into
479        its own source file (printint.c) and used #include to pull it into
480        pcretest.c and, when DEBUG is defined, into pcre.c, instead of having two
481        separate copies.
483    (b) Defined the list of op-code names for debugging as a macro in
484        internal.h so that it is next to the definition of the opcodes.
486    (c) Defined a table of op-code lengths for simpler skipping along compiled
487        code. This is again a macro in internal.h so that it is next to the
488        definition of the opcodes.
490    34. Added support for recursive calls to individual subpatterns, along the
491    lines of Robin Houston's patch (but implemented somewhat differently).
493    35. Further mods to the Makefile to help Win32. Also, added code to pcregrep to
494    allow it to read and process whole directories in Win32. This code was
495    contributed by Lionel Fourquaux; it has not been tested by me.
497    36. Added support for named subpatterns. The Python syntax (?P<name>...) is
498    used to name a group. Names consist of alphanumerics and underscores, and must
499    be unique. Back references use the syntax (?P=name) and recursive calls use
500    (?P>name) which is a PCRE extension to the Python extension. Groups still have
501    numbers. The function pcre_fullinfo() can be used after compilation to extract
502    a name/number map. There are three relevant calls:
504      PCRE_INFO_NAMEENTRYSIZE        yields the size of each entry in the map
505      PCRE_INFO_NAMECOUNT            yields the number of entries
506      PCRE_INFO_NAMETABLE            yields a pointer to the map.
508    The map is a vector of fixed-size entries. The size of each entry depends on
509    the length of the longest name used. The first two bytes of each entry are the
510    group number, most significant byte first. There follows the corresponding
511    name, zero terminated. The names are in alphabetical order.
513    37. Make the maximum literal string in the compiled code 250 for the non-UTF-8
514    case instead of 255. Making it the same both with and without UTF-8 support
515    means that the same test output works with both.
517    38. There was a case of malloc(0) in the POSIX testing code in pcretest. Avoid
518    calling malloc() with a zero argument.
520    39. Change 25 above had to resort to a heavy-handed test for the .* anchoring
521    optimization. I've improved things by keeping a bitmap of backreferences with
522    numbers 1-31 so that if .* occurs inside capturing brackets that are not in
523    fact referenced, the optimization can be applied. It is unlikely that a
524    relevant occurrence of .* (i.e. one which might indicate anchoring or forcing
525    the match to follow \n) will appear inside brackets with a number greater than
526    31, but if it does, any back reference > 31 suppresses the optimization.
528    40. Added a new compile-time option PCRE_NO_AUTO_CAPTURE. This has the effect
529    of disabling numbered capturing parentheses. Any opening parenthesis that is
530    not followed by ? behaves as if it were followed by ?: but named parentheses
531    can still be used for capturing (and they will acquire numbers in the usual
532    way).
534    41. Redesigned the return codes from the match() function into yes/no/error so
535    that errors can be passed back from deep inside the nested calls. A malloc
536    failure while inside a recursive subpattern call now causes the
537    PCRE_ERROR_NOMEMORY return instead of quietly going wrong.
539    42. It is now possible to set a limit on the number of times the match()
540    function is called in a call to pcre_exec(). This facility makes it possible to
541    limit the amount of recursion and backtracking, though not in a directly
542    obvious way, because the match() function is used in a number of different
543    circumstances. The count starts from zero for each position in the subject
544    string (for non-anchored patterns). The default limit is, for compatibility, a
545    large number, namely 10 000 000. You can change this in two ways:
547    (a) When configuring PCRE before making, you can use --with-match-limit=n
548        to set a default value for the compiled library.
550    (b) For each call to pcre_exec(), you can pass a pcre_extra block in which
551        a different value is set. See 45 below.
553    If the limit is exceeded, pcre_exec() returns PCRE_ERROR_MATCHLIMIT.
555    43. Added a new function pcre_config(int, void *) to enable run-time extraction
556    of things that can be changed at compile time. The first argument specifies
557    what is wanted and the second points to where the information is to be placed.
558    The current list of available information is:
562    The output is an integer that is set to one if UTF-8 support is available;
563    otherwise it is set to zero.
567    The output is an integer that it set to the value of the code that is used for
568    newline. It is either LF (10) or CR (13).
572    The output is an integer that contains the number of bytes used for internal
573    linkage in compiled expressions. The value is 2, 3, or 4. See item 32 above.
577    The output is an integer that contains the threshold above which the POSIX
578    interface uses malloc() for output vectors. See item 31 above.
582    The output is an unsigned integer that contains the default limit of the number
583    of match() calls in a pcre_exec() execution. See 42 above.
585    44. pcretest has been upgraded by the addition of the -C option. This causes it
586    to extract all the available output from the new pcre_config() function, and to
587    output it. The program then exits immediately.
589    45. A need has arisen to pass over additional data with calls to pcre_exec() in
590    order to support additional features. One way would have been to define
591    pcre_exec2() (for example) with extra arguments, but this would not have been
592    extensible, and would also have required all calls to the original function to
593    be mapped to the new one. Instead, I have chosen to extend the mechanism that
594    is used for passing in "extra" data from pcre_study().
596    The pcre_extra structure is now exposed and defined in pcre.h. It currently
597    contains the following fields:
599      flags         a bitmap indicating which of the following fields are set
600      study_data    opaque data from pcre_study()
601      match_limit   a way of specifying a limit on match() calls for a specific
602                      call to pcre_exec()
603      callout_data  data for callouts (see 49 below)
605    The flag bits are also defined in pcre.h, and are
611    The pcre_study() function now returns one of these new pcre_extra blocks, with
612    the actual study data pointed to by the study_data field, and the
613    PCRE_EXTRA_STUDY_DATA flag set. This can be passed directly to pcre_exec() as
614    before. That is, this change is entirely upwards-compatible and requires no
615    change to existing code.
617    If you want to pass in additional data to pcre_exec(), you can either place it
618    in a pcre_extra block provided by pcre_study(), or create your own pcre_extra
619    block.
621    46. pcretest has been extended to test the PCRE_EXTRA_MATCH_LIMIT feature. If a
622    data string contains the escape sequence \M, pcretest calls pcre_exec() several
623    times with different match limits, until it finds the minimum value needed for
624    pcre_exec() to complete. The value is then output. This can be instructive; for
625    most simple matches the number is quite small, but for pathological cases it
626    gets very large very quickly.
628    47. There's a new option for pcre_fullinfo() called PCRE_INFO_STUDYSIZE. It
629    returns the size of the data block pointed to by the study_data field in a
630    pcre_extra block, that is, the value that was passed as the argument to
631    pcre_malloc() when PCRE was getting memory in which to place the information
632    created by pcre_study(). The fourth argument should point to a size_t variable.
633    pcretest has been extended so that this information is shown after a successful
634    pcre_study() call when information about the compiled regex is being displayed.
636    48. Cosmetic change to Makefile: there's no need to have / after $(DESTDIR)
637    because what follows is always an absolute path. (Later: it turns out that this
638    is more than cosmetic for MinGW, because it doesn't like empty path
639    components.)
641    49. Some changes have been made to the callout feature (see 28 above):
643    (i)  A callout function now has three choices for what it returns:
645           0  =>  success, carry on matching
646         > 0  =>  failure at this point, but backtrack if possible
647         < 0  =>  serious error, return this value from pcre_exec()
649         Negative values should normally be chosen from the set of PCRE_ERROR_xxx
650         values. In particular, returning PCRE_ERROR_NOMATCH forces a standard
651         "match failed" error. The error number PCRE_ERROR_CALLOUT is reserved for
652         use by callout functions. It will never be used by PCRE itself.
654    (ii) The pcre_extra structure (see 45 above) has a void * field called
655         callout_data, with corresponding flag bit PCRE_EXTRA_CALLOUT_DATA. The
656         pcre_callout_block structure has a field of the same name. The contents of
657         the field passed in the pcre_extra structure are passed to the callout
658         function in the corresponding field in the callout block. This makes it
659         easier to use the same callout-containing regex from multiple threads. For
660         testing, the pcretest program has a new data escape
662           \C*n        pass the number n (may be negative) as callout_data
664         If the callout function in pcretest receives a non-zero value as
665         callout_data, it returns that value.
667    50. Makefile wasn't handling CFLAGS properly when compiling dftables. Also,
668    there were some redundant $(CFLAGS) in commands that are now specified as
669    $(LINK), which already includes $(CFLAGS).
671    51. Extensions to UTF-8 support are listed below. These all apply when (a) PCRE
672    has been compiled with UTF-8 support *and* pcre_compile() has been compiled
673    with the PCRE_UTF8 flag. Patterns that are compiled without that flag assume
674    one-byte characters throughout. Note that case-insensitive matching applies
675    only to characters whose values are less than 256. PCRE doesn't support the
676    notion of cases for higher-valued characters.
678    (i)   A character class whose characters are all within 0-255 is handled as
679          a bit map, and the map is inverted for negative classes. Previously, a
680          character > 255 always failed to match such a class; however it should
681          match if the class was a negative one (e.g. [^ab]). This has been fixed.
683    (ii)  A negated character class with a single character < 255 is coded as
684          "not this character" (OP_NOT). This wasn't working properly when the test
685          character was multibyte, either singly or repeated.
687    (iii) Repeats of multibyte characters are now handled correctly in UTF-8
688          mode, for example: \x{100}{2,3}.
690    (iv)  The character escapes \b, \B, \d, \D, \s, \S, \w, and \W (either
691          singly or repeated) now correctly test multibyte characters. However,
692          PCRE doesn't recognize any characters with values greater than 255 as
693          digits, spaces, or word characters. Such characters always match \D, \S,
694          and \W, and never match \d, \s, or \w.
696    (v)   Classes may now contain characters and character ranges with values
697          greater than 255. For example: [ab\x{100}-\x{400}].
699    (vi)  pcregrep now has a --utf-8 option (synonym -u) which makes it call
700          PCRE in UTF-8 mode.
702    52. The info request value PCRE_INFO_FIRSTCHAR has been renamed
703    PCRE_INFO_FIRSTBYTE because it is a byte value. However, the old name is
704    retained for backwards compatibility. (Note that LASTLITERAL is also a byte
705    value.)
707    53. The single man page has become too large. I have therefore split it up into
708    a number of separate man pages. These also give rise to individual HTML pages;
709    these are now put in a separate directory, and there is an index.html page that
710    lists them all. Some hyperlinking between the pages has been installed.
712    54. Added convenience functions for handling named capturing parentheses.
714    55. Unknown escapes inside character classes (e.g. [\M]) and escapes that
715    aren't interpreted therein (e.g. [\C]) are literals in Perl. This is now also
716    true in PCRE, except when the PCRE_EXTENDED option is set, in which case they
717    are faulted.
719    56. Introduced HOST_CC and HOST_CFLAGS which can be set in the environment when
720    calling configure. These values are used when compiling the dftables.c program
721    which is run to generate the source of the default character tables. They
722    default to the values of CC and CFLAGS. If you are cross-compiling PCRE,
723    you will need to set these values.
725    57. Updated the building process for Windows DLL, as provided by Fred Cox.
728    Version 3.9 02-Jan-02
729    ---------------------
731    1. A bit of extraneous text had somehow crept into the pcregrep documentation.
733    2. If --disable-static was given, the building process failed when trying to
734    build pcretest and pcregrep. (For some reason it was using libtool to compile
735    them, which is not right, as they aren't part of the library.)
738    Version 3.8 18-Dec-01
739    ---------------------
741    1. The experimental UTF-8 code was completely screwed up. It was packing the
742    bytes in the wrong order. How dumb can you get?
745    Version 3.7 29-Oct-01
746    ---------------------
748    1. In updating pcretest to check change 1 of version 3.6, I screwed up.
749    This caused pcretest, when used on the test data, to segfault. Unfortunately,
750    this didn't happen under Solaris 8, where I normally test things.
752    2. The Makefile had to be changed to make it work on BSD systems, where 'make'
753    doesn't seem to recognize that ./xxx and xxx are the same file. (This entry
754    isn't in ChangeLog distributed with 3.7 because I forgot when I hastily made
755    this fix an hour or so after the initial 3.7 release.)
758    Version 3.6 23-Oct-01
759    ---------------------
761    1. Crashed with /(sens|respons)e and \1ibility/ and "sense and sensibility" if
762    offsets passed as NULL with zero offset count.
764    2. The config.guess and config.sub files had not been updated when I moved to
765    the latest autoconf.
768    Version 3.5 15-Aug-01
769    ---------------------
771    1. Added some missing #if !defined NOPOSIX conditionals in pcretest.c that
772    had been forgotten.
774    2. By using declared but undefined structures, we can avoid using "void"
775    definitions in pcre.h while keeping the internal definitions of the structures
776    private.
778    3. The distribution is now built using autoconf 2.50 and libtool 1.4. From a
779    user point of view, this means that both static and shared libraries are built
780    by default, but this can be individually controlled. More of the work of
781    handling this static/shared cases is now inside libtool instead of PCRE's make
782    file.
784    4. The pcretest utility is now installed along with pcregrep because it is
785    useful for users (to test regexs) and by doing this, it automatically gets
786    relinked by libtool. The documentation has been turned into a man page, so
787    there are now .1, .txt, and .html versions in /doc.
789    5. Upgrades to pcregrep:
790       (i)   Added long-form option names like gnu grep.
791       (ii)  Added --help to list all options with an explanatory phrase.
792       (iii) Added -r, --recursive to recurse into sub-directories.
793       (iv)  Added -f, --file to read patterns from a file.
795    6. pcre_exec() was referring to its "code" argument before testing that
796    argument for NULL (and giving an error if it was NULL).
798    7. Upgraded Makefile.in to allow for compiling in a different directory from
799    the source directory.
801    8. Tiny buglet in pcretest: when pcre_fullinfo() was called to retrieve the
802    options bits, the pointer it was passed was to an int instead of to an unsigned
803    long int. This mattered only on 64-bit systems.
805    9. Fixed typo (3.4/1) in pcre.h again. Sigh. I had changed pcre.h (which is
806    generated) instead of pcre.in, which it its source. Also made the same change
807    in several of the .c files.
809    10. A new release of gcc defines printf() as a macro, which broke pcretest
810    because it had an ifdef in the middle of a string argument for printf(). Fixed
811    by using separate calls to printf().
813    11. Added --enable-newline-is-cr and --enable-newline-is-lf to the configure
814    script, to force use of CR or LF instead of \n in the source. On non-Unix
815    systems, the value can be set in config.h.
817    12. The limit of 200 on non-capturing parentheses is a _nesting_ limit, not an
818    absolute limit. Changed the text of the error message to make this clear, and
819    likewise updated the man page.
821    13. The limit of 99 on the number of capturing subpatterns has been removed.
822    The new limit is 65535, which I hope will not be a "real" limit.
825    Version 3.4 22-Aug-00
826    ---------------------
828    1. Fixed typo in pcre.h: unsigned const char * changed to const unsigned char *.
830    2. Diagnose condition (?(0) as an error instead of crashing on matching.
833    Version 3.3 01-Aug-00
834    ---------------------
836    1. If an octal character was given, but the value was greater than \377, it
837    was not getting masked to the least significant bits, as documented. This could
838    lead to crashes in some systems.
840    2. Perl 5.6 (if not earlier versions) accepts classes like [a-\d] and treats
841    the hyphen as a literal. PCRE used to give an error; it now behaves like Perl.
843    3. Added the functions pcre_free_substring() and pcre_free_substring_list().
844    These just pass their arguments on to (pcre_free)(), but they are provided
845    because some uses of PCRE bind it to non-C systems that can call its functions,
846    but cannot call free() or pcre_free() directly.
848    4. Add "make test" as a synonym for "make check". Corrected some comments in
849    the Makefile.
851    5. Add $(DESTDIR)/ in front of all the paths in the "install" target in the
852    Makefile.
854    6. Changed the name of pgrep to pcregrep, because Solaris has introduced a
855    command called pgrep for grepping around the active processes.
857    7. Added the beginnings of support for UTF-8 character strings.
859    8. Arranged for the Makefile to pass over the settings of CC, CFLAGS, and
860    RANLIB to ./ltconfig so that they are used by libtool. I think these are all
861    the relevant ones. (AR is not passed because ./ltconfig does its own figuring
862    out for the ar command.)
865  Version 3.2 12-May-00  Version 3.2 12-May-00
866  ---------------------  ---------------------

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