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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.
106    
107  . Run ./autogen.sh to ensure everything is up-to-date.  . Run ./autogen.sh to ensure everything is up-to-date.
108    
109  . Compile and test with many different config options, and combinations of  . Compile and test with many different config options, and combinations of
110    options. The maint/ManyConfigTests script now encapsulates this testing.    options. The maint/ManyConfigTests script now encapsulates this testing.
111    
112  . Run perltest.pl on the test data for tests 1 and 4. The output should match  . Run perltest.pl on the test data for tests 1, 4, 6, and 11. The output should
113    the PCRE test output, apart from the version identification at the top. The    match the PCRE test output, apart from the version identification at the
114    other tests are not Perl-compatible (they use various special PCRE options).    start of each test. The other tests are not Perl-compatible (they use various
115      PCRE-specific features or options).
116    
117  . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest  . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
118    valgrind", though that takes quite a long time.    valgrind", though that takes quite a long time.
119    
120  . It may also useful to test with Electric Fence, though the fact that it  . It is possible to test with the emulated memmove() function by undefining
121    grumbles for missing free() calls can be a nuisance. (A missing free() in    HAVE_MEMMOVE and HAVE_BCOPY in config.h, though I do not do this often. You
122    pcretest is hardly a big problem.) To build with EF, use:    may see a number of "pcre_memmove defined but not used" warnings for the
123      modules in which there is no call to memmove(). These can be ignored.
124      LIBS='/usr/lib/libefence.a -lpthread' with ./configure.  
125    . Documentation: check AUTHORS, COPYING, ChangeLog (check version and date),
126    Then all normal runs use it to check for buffer overflow. Also run everything    INSTALL, LICENCE, NEWS (check version and date), NON-UNIX-USE, and README.
127    with:    Many of these won't need changing, but over the long term things do change.
128    
129      EF_PROTECT_BELOW=1 <whatever>  . I used to test new releases myself on a number of different operating
130      systems, using different compilers as well. For example, on Solaris it is
131    because there have been problems with lookbehinds that looked too far.    helpful to test using Sun's cc compiler as a change from gcc. Adding
132      -xarch=v9 to the cc options does a 64-bit test, but it also needs -S 64 for
133  . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and    pcretest to increase the stack size for test 2. Since I retired I can no
134    HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not    longer do this, but instead I rely on putting out release candidates for
135    used" warnings for the modules in which there is no call to memmove(). These    folks on the pcre-dev list to test.
   can be ignored.  
   
 . 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.  
136    
137    
138  Making a PCRE release  Making a PCRE release
139  ---------------------  =====================
140    
141  Run PrepareRelease and commit the files that it changes (by removing trailing  Run PrepareRelease and commit the files that it changes (by removing trailing
142  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;
143    if it finds any markup errors, it reports them and then aborts.
144    
145    Once PrepareRelease has run clean, run "make distcheck" to create the tarballs
146    and the zipball. Double-check with "svn status", then create an SVN tagged
147    copy:
148    
149      svn copy svn://vcs.exim.org/pcre/code/trunk \
150               svn://vcs.exim.org/pcre/code/tags/pcre-8.xx
151    
152  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
153  webmaster@pcre.org and the mailing list.  webmaster@pcre.org and the mailing list. Also, update the list of version
154    numbers in Bugzilla (edit products).
155    
156    
157  Future ideas (wish list)  Future ideas (wish list)
158  ------------------------  ========================
159    
160  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
161  vary enormously in their usefulness and potential for implementation. Some are  vary enormously in their usefulness and potential for implementation. Some are
162  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;
163  others are relatively new.  others are relatively new.
164    
165  . Optimization  . Optimization
166    
167    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
168    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
169    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:
170    
171    * /((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
172      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}?
173      OTOH, this is pathological - the user could easily fix it.      OTOH, this is pathological - the user could easily fix it.
174    
175    * 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
176      to have little effect, and maybe makes things worse.      to have little effect, and maybe makes things worse.
177    
178    * "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
179      over the existing "required byte" (reqbyte) feature that just saves one      over the existing "required byte" (reqbyte) feature that just remembers one
180      byte.      byte.
181    
182    * These probably need to go in study():    * These probably need to go in pcre_study():
183    
184      o Remember an initial string rather than just 1 char?      o Remember an initial string rather than just 1 char?
185    
186      o A required byte from alternatives - not just the last char, but an      o A required byte from alternatives - not just the last char, but an
187        earlier one if common to all alternatives.        earlier one if common to all alternatives.
188    
     o Minimum length of subject needed.  
   
189      o Friedl contains other ideas.      o Friedl contains other ideas.
190    
191      * pcre_study() does not set initial byte flags for Unicode property types
192        such as \p; I don't know how much benefit there would be for, for example,
193        setting the bits for 0-9 and all bytes >= xC0 when a pattern starts with
194        \p{N}.
195    
196      * There is scope for more "auto-possessifying" in connection with \p and \P.
197    
198  . 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-
199    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
200    difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE    difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
201    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
202    because I think it needs much more state to be remembered.    because I think it needs much more state to be remembered.
203    
204  . Perl 6 will be a revolution. Is it a revolution too far for PCRE?  . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
205    
206  . Unicode  . Unicode
207    
208    * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX    * There has been a request for direct support of 16-bit characters and
209      character classes. For the moment, I've chosen not to support this for      UTF-16 (Bugzilla #1049). However, since Unicode is moving beyond purely
210      backward compatibility, for speed, and because it would be messy to      16-bit characters, is this worth it at all? One possible way of handling
211      implement.      16-bit characters would be to "load" them in the same way that UTF-8
212        characters are loaded. Another possibility is to provide a set of
213        translation functions, and build an index during translation so that the
214        returned offsets can automatically be translated (using the index) after a
215        match.
216    
217    * A different approach to Unicode might be to use a typedef to do everything    * A different approach to Unicode might be to use a typedef to do everything
218      in unsigned shorts instead of unsigned chars. Actually, we'd have to have a      in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
219      new typedef to distinguish data from bits of compiled pattern that are in      new typedef to distinguish data from bits of compiled pattern that are in
220      bytes, I think. There would need to be conversion functions in and out. I      bytes, I think. There would need to be conversion functions in and out. I
221      don't think this is particularly trivial - and anyway, Unicode now has      don't think this is particularly trivial - and anyway, Unicode now has
222      characters that need more than 16 bits, so is this at all sensible?      characters that need more than 16 bits, so is this at all sensible? I
223        suspect not.
224    * 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.  
   
225  . 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.
226    
227  . Line endings:  . Line endings:
228    
229    * 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
230      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.
231      If this is done, a suitable option for pcregrep is also required.      If it is done, a suitable option for pcregrep is also required.
232    
233  . 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.
234    This probably affects quite a few places in the code.    This affects quite a few places in the code and is not trivial.
235    
236  . 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.  
237    
238  . A feature to suspend a match via a callout was once requested.  . A feature to suspend a match via a callout was once requested.
239    
240  . Option to convert results into character offsets and character lengths.  . Option to convert results into character offsets and character lengths.
241    
242  . 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
243    the job of "head".    the job of "head".
244    
245  . 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,
246    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)
247    support --outputfile=name.    support --outputfile=name.
   
 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.  
248    
249  . 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.
250    
251    . Add a user pointer to pcre_malloc/free functions -- some option would be
252    needed to retain backward compatibility.    needed to retain backward compatibility.
253    
254  . Define a union for the results from pcre_fullinfo().  . Define a union for the results from pcre_fullinfo().
255    
256  . 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
257    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
258    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
259    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.
260    
 . 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.  
   
261  . 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
262    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
263    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.
264    
265  . Should pcretest have some private locale data, to avoid relying on the  . Should pcretest have some private locale data, to avoid relying on the
266    available locales for the test data, since different OS have different ideas?    available locales for the test data, since different OS have different ideas?
267    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.
268    
269  . 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
270    them will of course slow it down.    them will of course slow it down.
271    
272  . 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
273    that is run only when the link size *is* 2; leave in some non-numbered    never wanted. This seems rather marginal.
274    debugging tests using the new /Z feature.  
275    . Check names that consist entirely of digits: PCRE allows, but do Perl and
276  . Stan Switzer's goto replacement for longjmp, which is apparently very slow on    Python, etc?
277    OS-X. This is used when stack recursion is disabled. It would be worth doing  
278    some timing tests on other OS.  . A user suggested a parameter to limit the length of string matched, for
279      example if the parameter is N, the current match should fail if the matched
280  . Someone suggested --disable-callout to save code space when callouts are    substring exceeds N. This could apply to both match functions. The value
281    never wanted. This seems rather marginal.    could be a new field in the extra block.
282    
283  . Work needs doing so that the pcregrep tests work better with different  . Callouts with arguments: (?Cn:ARG) for instance.
284    linebreak settings. Currently, some tests don't work when the input files  
285    do not have \n line endings.  . A user is going to supply a patch to generalize the API for user-specific
286      memory allocation so that it is more flexible in threaded environments. This
287  . If the fr_FR locale isn't available for testing, try "french" instead,    was promised a long time ago, and never appeared...
288    because this may be available on Windows. It means modifying the test data,  
289    however.  . Write a function that generates random matching strings for a compiled regex.
290    
291    . Write a wrapper to maintain a structure with specified runtime parameters,
292      such as recurse limit, and pass these to PCRE each time it is called. Also
293      maybe malloc and free. A user sent a prototype.
294    
295    . Pcregrep: an option to specify the output line separator, either as a string
296      or select from a fixed list. This is not dead easy, because at the moment it
297      outputs whatever is in the input file.
298    
299    . Improve the code for duplicate checking in pcre_dfa_exec(). An incomplete,
300      non-thread-safe patch showed that this can help performance for patterns
301      where there are many alternatives. However, a simple thread-safe
302      implementation that I tried made things worse in many simple cases, so this
303      is not an obviously good thing.
304    
305    . Make the longest lookbehind available via pcre_fullinfo(). This is not
306      straightforward because lookbehinds can be nested inside lookbehinds. This
307      case will have to be identified, and the amounts added. This should then give
308      the maximum possible lookbehind length. The reason for wanting this is to
309      help when implementing multi-segment matching using pcre_exec() with partial
310      matching and overlapping segments.
311    
312    . PCRE cannot at present distinguish between subpatterns with different names,
313      but the same number (created by the use of ?|). In order to do so, a way of
314      remembering *which* subpattern numbered n matched is needed. Bugzilla #760.
315      Now that (*MARK) has been implemented, it can perhaps be used as a way round
316      this problem.
317    
318    . Instead of having #ifdef HAVE_CONFIG_H in each module, put #include
319      "something" and the the #ifdef appears only in one place, in "something".
320    
321  Philip Hazel  Philip Hazel
322  Email local part: ph10  Email local part: ph10
323  Email domain: cam.ac.uk  Email domain: cam.ac.uk
324  Last updated: 24 April 2007  Last updated: 12 January 2011

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