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1  MAINTENANCE README FOR PCRE  MAINTENANCE README FOR PCRE
2  ---------------------------  ===========================
3    
4  The files in the "maint" directory of the PCRE source contain data, scripts,  The files in the "maint" directory of the PCRE source contain data, scripts,
5  and programs that are used for the maintenance of PCRE, but which do not form  and programs that are used for the maintenance of PCRE, but which do not form
6  part of the PCRE distribution tarballs. This document describes these files and  part of the PCRE distribution tarballs. This document describes these files and
7  also contains some notes for maintainers. Its contents are:  also contains some notes for maintainers. Its contents are:
8    
9    Files in the maint directory    Files in the maint directory
10    Updating to a new Unicode release    Updating to a new Unicode release
11    Preparing for a PCRE release    Preparing for a PCRE release
12    Making a PCRE release    Making a PCRE release
13    Long-term ideas (wish list)    Long-term ideas (wish list)
14    
15    
16  Files in the maint directory  Files in the maint directory
17  ----------------------------  ============================
18    
19    ---------------- This file is now OBSOLETE and no longer used ----------------
20  Builducptable    A Perl script that creates the contents of the ucptable.h file  Builducptable    A Perl script that creates the contents of the ucptable.h file
21                   from two Unicode data files, which themselves are downloaded                   from two Unicode data files, which themselves are downloaded
22                   from the Unicode web site. Run this script in the "maint"                   from the Unicode web site. Run this script in the "maint"
23                   directory.                   directory.
24    ---------------- This file is now OBSOLETE and no longer used ----------------
25    
26    GenerateUtt.py   A Python script to generate part of the pcre_tables.c file
27                     that contains Unicode script names in a long string with
28                     offsets, which is tedious to maintain by hand.
29    
30  ManyConfigTests  A shell script that runs "configure, make, test" a number of  ManyConfigTests  A shell script that runs "configure, make, test" a number of
31                   times with different configuration settings.                   times with different configuration settings.
32    
33  Unicode.tables   The files in this directory, Scripts.txt and UnicodeData.txt,  MultiStage2.py   A Python script that generates the file pcre_ucd.c from three
34                   were downloaded from the Unicode web site. They contain                   Unicode data tables, which are themselves downloaded from the
35                   information about Unicode characters and scripts.                   Unicode web site. Run this script in the "maint" directory.
36                     The generated file contains the tables for a 2-stage lookup
37  ucptest.c        A short C program for testing the Unicode property functions                   of Unicode properties.
38                   in pcre_ucp_searchfuncs.c, mainly useful after rebuilding the  
39                   Unicode property table. Compile and run this in the "maint"  pcre_chartables.c.non-standard
40                   directory.                   This is a set of character tables that came from a Windows
41                     system. It has characters greater than 128 that are set as
42                     spaces, amongst other things. I kept it so that it can be
43                     used for testing from time to time.
44    
45    README           This file.
46    
47    Unicode.tables   The files in this directory, DerivedGeneralCategory.txt,
48                     Scripts.txt and UnicodeData.txt, were downloaded from the
49                     Unicode web site. They contain information about Unicode
50                     characters and scripts.
51    
52    ucptest.c        A short C program for testing the Unicode property macros
53                     that do lookups in the pcre_ucd.c data, mainly useful after
54                     rebuilding the Unicode property table. Compile and run this in
55                     the "maint" directory (see comments at its head).
56    
57  ucptestdata      A directory containing two files, testinput1 and testoutput1,  ucptestdata      A directory containing two files, testinput1 and testoutput1,
58                   to use in conjunction with the ucptest program.                   to use in conjunction with the ucptest program.
59    
60  utf8.c           A short, freestanding C program for converting a Unicode code  utf8.c           A short, freestanding C program for converting a Unicode code
61                   point into a sequence of bytes in the UTF-8 encoding, and vice                   point into a sequence of bytes in the UTF-8 encoding, and vice
62                   versa. If its argument is a hex number such as 0x1234, it                   versa. If its argument is a hex number such as 0x1234, it
# Line 43  utf8.c           A short, freestanding C Line 64  utf8.c           A short, freestanding C
64                   is sequence of concatenated UTF-8 bytes (e.g. e188b4) it                   is sequence of concatenated UTF-8 bytes (e.g. e188b4) it
65                   treats them as a UTF-8 character and outputs the equivalent                   treats them as a UTF-8 character and outputs the equivalent
66                   code point in hex.                   code point in hex.
67    
68    
69  Updating to a new Unicode release  Updating to a new Unicode release
70  ---------------------------------  =================================
71    
72    When there is a new release of Unicode, the files in Unicode.tables must be
73    refreshed from the web site. If the new version of Unicode adds new character
74    scripts, the source file ucp.h and both the MultiStage2.py and the
75    GenerateUtt.py scripts must be edited to add the new names. Then MultiStage2.py
76    can be run to generate a new version of pcre_ucd.c, and GenerateUtt.py can be
77    run to generate the tricky tables for inclusion in pcre_tables.c.
78    
79    If MultiStage2.py gives the error "ValueError: list.index(x): x not in list",
80    the cause is usually a missing (or misspelt) name in the list of scripts. I
81    couldn't find a straightforward list of scripts on the Unicode site, but
82    there's a useful Wikipedia page that list them, and notes the Unicode version
83    in which they were introduced:
84    
85    http://en.wikipedia.org/wiki/Unicode_scripts#Table_of_Unicode_scripts
86    
87    The ucptest program can be compiled and used to check that the new tables in
88    pcre_ucd.c work properly, using the data files in ucptestdata to check a number
89    of test characters. The source file ucptest.c must be updated whenever new
90    Unicode script names are added.
91    
92  When there is a new release of Unicode, the files in Unicode.tables must be  Note also that both the pcresyntax.3 and pcrepattern.3 man pages contain lists
93  refreshed from the web site, and the Buildupctable script can then be run to  of Unicode script names.
 generate a new version of ucptable.h. The ucptest program can be used to check  
 that the resulting table works properly, using the data files in ucptestdata to  
 check a number of test characters.  
94    
95    
96  Preparing for a PCRE release  Preparing for a PCRE release
97  ----------------------------  ============================
98    
99  This section contains a checklist of things that I consult before building a  This section contains a checklist of things that I consult before building a
100  distribution for a new release.  distribution for a new release.
101    
102  . Ensure that the version number and version date are correct in configure.ac,  . Ensure that the version number and version date are correct in configure.ac.
103    ChangeLog, and NEWS.  
104    . If new build options have been added, ensure that they are added to the CMake
105      files as well as to the autoconf files. The relevant files are CMakeLists.txt
106      and config-cmake.h.in. After making a release tarball, test it out with CMake
107      if there have been changes here.
108    
109  . Run ./autogen.sh to ensure everything is up-to-date.  . Run ./autogen.sh to ensure everything is up-to-date.
110    
111  . Compile and test with many different config options, and combinations of  . Compile and test with many different config options, and combinations of
112    options. The maint/ManyConfigTests script now encapsulates this testing.    options. Also, test with valgrind by running "RunTest valgrind" and
113      "RunGrepTest valgrind" (which takes quite a long time). The script
114  . Run perltest.pl on the test data for tests 1 and 4. The output should match    maint/ManyConfigTests now encapsulates this testing. It runs tests with
115    the PCRE test output, apart from the version identification at the top. The    different configurations, and it also runs some of them with valgrind, all of
116    other tests are not Perl-compatible (they use various special PCRE options).    which can take quite some time.
117    
118  . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest  . Run perltest.pl on the test data for tests 1, 4, and 6. The output
119    valgrind", though that takes quite a long time.    should match the PCRE test output, apart from the version identification at
120      the start of each test. The other tests are not Perl-compatible (they use
121  . It may also useful to test with Electric Fence, though the fact that it    various PCRE-specific features or options).
122    grumbles for missing free() calls can be a nuisance. (A missing free() in  
123    pcretest is hardly a big problem.) To build with EF, use:  . It is possible to test with the emulated memmove() function by undefining
124      HAVE_MEMMOVE and HAVE_BCOPY in config.h, though I do not do this often. You
125      LIBS='/usr/lib/libefence.a -lpthread' with ./configure.    may see a number of "pcre_memmove defined but not used" warnings for the
126      modules in which there is no call to memmove(). These can be ignored.
127    Then all normal runs use it to check for buffer overflow. Also run everything  
128    with:  . Documentation: check AUTHORS, COPYING, ChangeLog (check version and date),
129      INSTALL, LICENCE, NEWS (check version and date), NON-UNIX-USE, and README.
130      EF_PROTECT_BELOW=1 <whatever>    Many of these won't need changing, but over the long term things do change.
131    
132    because there have been problems with lookbehinds that looked too far.  . I used to test new releases myself on a number of different operating
133      systems, using different compilers as well. For example, on Solaris it is
134  . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and    helpful to test using Sun's cc compiler as a change from gcc. Adding
135    HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not    -xarch=v9 to the cc options does a 64-bit test, but it also needs -S 64 for
136    used" warnings for the modules in which there is no call to memmove(). These    pcretest to increase the stack size for test 2. Since I retired I can no
137    can be ignored.    longer do this, but instead I rely on putting out release candidates for
138      folks on the pcre-dev list to test.
 . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,  
   LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't  
   need changing, but over the long term things do change.  
   
 . Man pages: Check all man pages for \ not followed by e or f or " because  
   that indicates a markup error.  
   
 . When the release is built, test it on a number of different operating  
   systems if possible, and using different compilers as well. For example,  
   on Solaris it is helpful to test using Sun's cc compiler as a change from  
   gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also  
   needs -S 64 for pcretest to increase the stack size for test 2.  
139    
140    
141  Making a PCRE release  Making a PCRE release
142  ---------------------  =====================
143    
144  Run PrepareRelease and commit the files that it changes (by removing trailing  Run PrepareRelease and commit the files that it changes (by removing trailing
145  spaces). Then run "make distcheck" to create the tarballs and the zipball.  spaces). The first thing this script does is to run CheckMan on the man pages;
146    if it finds any markup errors, it reports them and then aborts.
147    
148    Once PrepareRelease has run clean, run "make distcheck" to create the tarballs
149    and the zipball. Double-check with "svn status", then create an SVN tagged
150    copy:
151    
152      svn copy svn://vcs.exim.org/pcre/code/trunk \
153               svn://vcs.exim.org/pcre/code/tags/pcre-8.xx
154    
155  Don't forget to update Freshmeat when the new release is out, and to tell  Don't forget to update Freshmeat when the new release is out, and to tell
156  webmaster@pcre.org and the mailing list.  webmaster@pcre.org and the mailing list. Also, update the list of version
157    numbers in Bugzilla (edit products).
158    
159    
160  Future ideas (wish list)  Future ideas (wish list)
161  ------------------------  ========================
162    
163  This section records a list of ideas so that they do not get forgotten. They  This section records a list of ideas so that they do not get forgotten. They
164  vary enormously in their usefulness and potential for implementation. Some are  vary enormously in their usefulness and potential for implementation. Some are
165  very sensible; some are rather wacky. Some have been on this list for years;  very sensible; some are rather wacky. Some have been on this list for years;
166  others are relatively new.  others are relatively new.
167    
168  . Optimization  . Optimization
169    
170    There are always ideas for new optimizations so as to speed up pattern    There are always ideas for new optimizations so as to speed up pattern
171    matching. Most of them try to save work by recognizing a non-match without    matching. Most of them try to save work by recognizing a non-match without
172    having to scan all the possibilities. These are some that I've recorded:    having to scan all the possibilities. These are some that I've recorded:
173    
174    * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very    * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
175      slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?      slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
176      OTOH, this is pathological - the user could easily fix it.      OTOH, this is pathological - the user could easily fix it.
177    
178    * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems    * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
179      to have little effect, and maybe makes things worse.      to have little effect, and maybe makes things worse.
180    
181    * "Ends with literal string" - note that a single character doesn't gain much    * "Ends with literal string" - note that a single character doesn't gain much
182      over the existing "required byte" (reqbyte) feature that just saves one      over the existing "required byte" (reqbyte) feature that just remembers one
183      byte.      data unit.
184    
185    * These probably need to go in study():    * These probably need to go in pcre_study():
186    
187      o Remember an initial string rather than just 1 char?      o Remember an initial string rather than just 1 char?
188    
189      o A required byte from alternatives - not just the last char, but an      o A required data unit from alternatives - not just the last unit, but an
190        earlier one if common to all alternatives.        earlier one if common to all alternatives.
191    
     o Minimum length of subject needed.  
   
192      o Friedl contains other ideas.      o Friedl contains other ideas.
193    
194      * pcre_study() does not set initial byte flags for Unicode property types
195        such as \p; I don't know how much benefit there would be for, for example,
196        setting the bits for 0-9 and all bytes >= xC0 when a pattern starts with
197        \p{N}.
198    
199      * There is scope for more "auto-possessifying" in connection with \p and \P.
200    
201  . If Perl gets to a consistent state over the settings of capturing sub-  . If Perl gets to a consistent state over the settings of capturing sub-
202    patterns inside repeats, see if we can match it. One example of the    patterns inside repeats, see if we can match it. One example of the
203    difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE    difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
204    leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard    leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
205    because I think it needs much more state to be remembered.    because I think it needs much more state to be remembered.
   
 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?  
206    
207  . Unicode  . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
208    
   * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX  
     character classes. For the moment, I've chosen not to support this for  
     backward compatibility, for speed, and because it would be messy to  
     implement.  
   
   * A different approach to Unicode might be to use a typedef to do everything  
     in unsigned shorts instead of unsigned chars. Actually, we'd have to have a  
     new typedef to distinguish data from bits of compiled pattern that are in  
     bytes, I think. There would need to be conversion functions in and out. I  
     don't think this is particularly trivial - and anyway, Unicode now has  
     characters that need more than 16 bits, so is this at all sensible?  
   
   * There has been a request for direct support of 16-bit characters and  
     UTF-16. However, since Unicode is moving beyond purely 16-bit characters,  
     is this worth it at all? One possible way of handling 16-bit characters  
     would be to "load" them in the same way that UTF-8 characters are loaded.  
   
209  . Allow errorptr and erroroffset to be NULL. I don't like this idea.  . Allow errorptr and erroroffset to be NULL. I don't like this idea.
210    
211  . Line endings:  . Line endings:
212    
213    * Option to use NUL as a line terminator in subject strings. This could now    * Option to use NUL as a line terminator in subject strings. This could now
214      be done relatively easily since the extension to support LF, CR, and CRLF.      be done relatively easily since the extension to support LF, CR, and CRLF.
215      If this is done, a suitable option for pcregrep is also required.      If it is done, a suitable option for pcregrep is also required.
216    
217  . Option to provide the pattern with a length instead of with a NUL terminator.  . Option to provide the pattern with a length instead of with a NUL terminator.
218    This probably affects quite a few places in the code.    This affects quite a few places in the code and is not trivial.
219    
220  . Catch SIGSEGV for stack overflows?  . Catch SIGSEGV for stack overflows?
   
 . "Cut" as described in Jeffrey Friedl's book, p364: \v and \V. The definitions  
   aren't yet clear enough for me. \v flushes saved states so that no  
   backtracking to anything earlier can happen; \V says "no more bumpalong", but  
   does it fail the current match? As described in the book, these aren't really  
   "cut" as in Prolog, are they? NOTE: (a) PCRE once had "cut", but it was  
   removed when atomic groups were introduced. (b) Perl 5.10 has some (*PRUNE)  
   features -- see below.  
221    
222  . A feature to suspend a match via a callout was once requested.  . A feature to suspend a match via a callout was once requested.
223    
224  . Option to convert results into character offsets and character lengths.  . Option to convert results into character offsets and character lengths.
225    
226  . Option for pcregrep to scan only the start of a file. I am not keen - this is  . Option for pcregrep to scan only the start of a file. I am not keen - this is
227    the job of "head".    the job of "head".
228    
229  . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,  . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
230    preceded by a blank line, instead of adding it to every matched line, and (b)    preceded by a blank line, instead of adding it to every matched line, and (b)
231    support --outputfile=name.    support --outputfile=name.
   
 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.  
232    
233  . Add a user pointer to pcre_malloc/free functions -- some option would be  . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 8.
234      (And now presumably UTF-16 and UCP for the 16-bit library.)
235    
236    . Add a user pointer to pcre_malloc/free functions -- some option would be
237    needed to retain backward compatibility.    needed to retain backward compatibility.
238    
239  . Define a union for the results from pcre_fullinfo().  . Define a union for the results from pcre_fullinfo().
240    
241  . Provide a "random access to the subject" facility so that the way in which it  . Provide a "random access to the subject" facility so that the way in which it
242    is stored is independent of PCRE. For efficiency, it probably isn't possible    is stored is independent of PCRE. For efficiency, it probably isn't possible
243    to switch this dynamically. It would have to be specified when PCRE was    to switch this dynamically. It would have to be specified when PCRE was
244    compiled. PCRE would then call a function every time it wanted a character.    compiled. PCRE would then call a function every time it wanted a character.
245    
 . There are new (*PRUNE) facilities in Perl 5.10, some of which it might be  
   relatively easy to implement.  
   
 . Also in Perl 5.10 are relative subroutine references (?&-1) and (?&+1) which  
   I didn't know about when I added some 5.10 features for PCRE 7.0. What about  
   (?(-1)... as a condition? That's an obvious extension, even if Perl 5.10  
   doesn't have it.  
   
246  . Wild thought: the ability to compile from PCRE's internal byte code to a real  . Wild thought: the ability to compile from PCRE's internal byte code to a real
247    FSM and a very fast (third) matcher to process the result. There would be    FSM and a very fast (third) matcher to process the result. There would be
248    even more restrictions than for pcre_dfa_exec(), however. This is not easy.    even more restrictions than for pcre_dfa_exec(), however. This is not easy.
249      This is probably obsolete now that we have the JIT support.
250    
251  . Should pcretest have some private locale data, to avoid relying on the  . Should pcretest have some private locale data, to avoid relying on the
252    available locales for the test data, since different OS have different ideas?    available locales for the test data, since different OS have different ideas?
253    This won't be as thorough a test, but perhaps that doesn't really matter.    This won't be as thorough a test, but perhaps that doesn't really matter.
254    
255  . pcregrep: add -rs for a sorted recurse? Having to store file names and sort  . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
256    them will of course slow it down.    them will of course slow it down.
257    
258  . Re-arrange test 2: take out the link-size dependent stuff for a separate test  . Someone suggested --disable-callout to save code space when callouts are
259    that is run only when the link size *is* 2; leave in some non-numbered    never wanted. This seems rather marginal.
260    debugging tests using the new /Z feature.  
261    . Check names that consist entirely of digits: PCRE allows, but do Perl and
262  . Stan Switzer's goto replacement for longjmp, which is apparently very slow on    Python, etc?
263    OS-X. This is used when stack recursion is disabled. It would be worth doing  
264    some timing tests on other OS.  . A user suggested a parameter to limit the length of string matched, for
265      example if the parameter is N, the current match should fail if the matched
266  . Someone suggested --disable-callout to save code space when callouts are    substring exceeds N. This could apply to both match functions. The value
267    never wanted. This seems rather marginal.    could be a new field in the extra block.
268    
269  . Work needs doing so that the pcregrep tests work better with different  . Callouts with arguments: (?Cn:ARG) for instance.
270    linebreak settings. Currently, some tests don't work when the input files  
271    do not have \n line endings.  . A user is going to supply a patch to generalize the API for user-specific
272      memory allocation so that it is more flexible in threaded environments. This
273  . If the fr_FR locale isn't available for testing, try "french" instead,    was promised a long time ago, and never appeared. However, this is a live
274    because this may be available on Windows. It means modifying the test data,    issue not only for threaded environments, but for libraries that use PCRE and
275    however.    want not to be beholden to their caller's memory allocation.
276    
277    . Write a wrapper to maintain a structure with specified runtime parameters,
278      such as recurse limit, and pass these to PCRE each time it is called. Also
279      maybe malloc and free. A user sent a prototype. This relates the the previous
280      item.
281    
282    . Write a function that generates random matching strings for a compiled regex.
283    
284    . Pcregrep: an option to specify the output line separator, either as a string
285      or select from a fixed list. This is not dead easy, because at the moment it
286      outputs whatever is in the input file.
287    
288    . Improve the code for duplicate checking in pcre_dfa_exec(). An incomplete,
289      non-thread-safe patch showed that this can help performance for patterns
290      where there are many alternatives. However, a simple thread-safe
291      implementation that I tried made things worse in many simple cases, so this
292      is not an obviously good thing.
293    
294    . Make the longest lookbehind available via pcre_fullinfo(). This is not
295      straightforward because lookbehinds can be nested inside lookbehinds. This
296      case will have to be identified, and the amounts added. This should then give
297      the maximum possible lookbehind length. The reason for wanting this is to
298      help when implementing multi-segment matching using pcre_exec() with partial
299      matching and overlapping segments.
300    
301    . PCRE cannot at present distinguish between subpatterns with different names,
302      but the same number (created by the use of ?|). In order to do so, a way of
303      remembering *which* subpattern numbered n matched is needed. Bugzilla #760.
304      Now that (*MARK) has been implemented, it can perhaps be used as a way round
305      this problem.
306    
307    . Instead of having #ifdef HAVE_CONFIG_H in each module, put #include
308      "something" and the the #ifdef appears only in one place, in "something".
309    
310  Philip Hazel  Philip Hazel
311  Email local part: ph10  Email local part: ph10
312  Email domain: cam.ac.uk  Email domain: cam.ac.uk
313  Last updated: 24 April 2007  Last updated: 14 January 2012

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