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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    MultiStage2.py   A Python script that generates the file pcre_ucd.c from three
34                     Unicode data tables, which are themselves downloaded from the
35                     Unicode web site. Run this script in the "maint" directory.
36                     The generated file contains the tables for a 2-stage lookup
37                     of Unicode properties.
38    
39  Unicode.tables   The files in this directory, Scripts.txt and UnicodeData.txt,  pcre_chartables.c.non-standard
40                   were downloaded from the Unicode web site. They contain                   This is a set of character tables that came from a Windows
41                   information about Unicode characters and scripts.                   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  ucptest.c        A short C program for testing the Unicode property functions                   used for testing from time to time.
44                   in pcre_ucp_searchfuncs.c, mainly useful after rebuilding the  
45                   Unicode property table. Compile and run this in the "maint"  README           This file.
46                   directory.  
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  . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
121    grumbles for missing free() calls can be a nuisance. (A missing free() in    HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
   pcretest is hardly a big problem.) To build with EF, use:  
   
     LIBS='/usr/lib/libefence.a -lpthread' with ./configure.  
   
   Then all normal runs use it to check for buffer overflow. Also run everything  
   with:  
   
     EF_PROTECT_BELOW=1 <whatever>  
   
   because there have been problems with lookbehinds that looked too far.  
   
 . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and  
   HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not  
122    used" warnings for the modules in which there is no call to memmove(). These    used" warnings for the modules in which there is no call to memmove(). These
123    can be ignored.    can be ignored.
124    
125  . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,  . Documentation: check AUTHORS, COPYING, ChangeLog (check version and date),
126    LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't    INSTALL, LICENCE, NEWS (check version and date), NON-UNIX-USE, and README.
127    need changing, but over the long term things do change.    Many of these won't need changing, but over the long term things do change.
128    
129  . Man pages: Check all man pages for \ not followed by e or f or " because  . Man pages: Check all man pages for \ not followed by e or f or " because
130    that indicates a markup error.    that indicates a markup error. However, there is one exception: pcredemo.3,
131      which is created from the pcredemo.c program. It contains three instances
132      of \\n.
133    
134  . When the release is built, test it on a number of different operating  . When the release is built, test it on a number of different operating
135    systems if possible, and using different compilers as well. For example,    systems if possible, and using different compilers as well. For example,
136    on Solaris it is helpful to test using Sun's cc compiler as a change from    on Solaris it is helpful to test using Sun's cc compiler as a change from
137    gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also    gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
# Line 109  distribution for a new release. Line 139  distribution for a new release.
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). Then run "make distcheck" to create the tarballs and the zipball.
146    Double-check with "svn status", then create an SVN tagged copy:
147    
148      svn copy svn://vcs.exim.org/pcre/code/trunk \
149               svn://vcs.exim.org/pcre/code/tags/pcre-8.xx
150    
151  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
152  webmaster@pcre.org and the mailing list.  webmaster@pcre.org and the mailing list. Also, update the list of version
153    numbers in Bugzilla (edit products).
154    
155    
156  Future ideas (wish list)  Future ideas (wish list)
157  ------------------------  ========================
158    
159  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
160  vary enormously in their usefulness and potential for implementation. Some are  vary enormously in their usefulness and potential for implementation. Some are
161  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;
162  others are relatively new.  others are relatively new.
163    
164  . Optimization  . Optimization
165    
166    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
167    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
168    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:
169    
170    * /((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
171      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}?
172      OTOH, this is pathological - the user could easily fix it.      OTOH, this is pathological - the user could easily fix it.
173    
174    * 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
175      to have little effect, and maybe makes things worse.      to have little effect, and maybe makes things worse.
176    
177    * "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
178      over the existing "required byte" (reqbyte) feature that just saves one      over the existing "required byte" (reqbyte) feature that just remembers one
179      byte.      byte.
180    
181    * These probably need to go in study():    * These probably need to go in pcre_study():
182    
183      o Remember an initial string rather than just 1 char?      o Remember an initial string rather than just 1 char?
184    
185      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
186        earlier one if common to all alternatives.        earlier one if common to all alternatives.
187    
     o Minimum length of subject needed.  
   
188      o Friedl contains other ideas.      o Friedl contains other ideas.
189    
190      * pcre_study() does not set initial byte flags for Unicode property types
191        such as \p; I don't know how much benefit there would be for, for example,
192        setting the bits for 0-9 and all bytes >= xC0 when a pattern starts with
193        \p{N}.
194    
195      * There is scope for more "auto-possessifying" in connection with \p and \P.
196    
197  . 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-
198    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
199    difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE    difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
200    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
201    because I think it needs much more state to be remembered.    because I think it needs much more state to be remembered.
202    
203  . 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?
204    
205  . Unicode  . Unicode
206    
   * 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.  
   
207    * 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
208      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
209      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
210      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
211      don't think this is particularly trivial - and anyway, Unicode now has      don't think this is particularly trivial - and anyway, Unicode now has
212      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?
213    
214    * There has been a request for direct support of 16-bit characters and    * There has been a request for direct support of 16-bit characters and
215      UTF-16. However, since Unicode is moving beyond purely 16-bit characters,      UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
216      is this worth it at all? One possible way of handling 16-bit characters      is this worth it at all? One possible way of handling 16-bit characters
217      would be to "load" them in the same way that UTF-8 characters are loaded.      would be to "load" them in the same way that UTF-8 characters are loaded.
218    
219  . 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.
220    
221  . Line endings:  . Line endings:
222    
223    * 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
224      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.
225      If this is done, a suitable option for pcregrep is also required.      If it is done, a suitable option for pcregrep is also required.
226    
227  . 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.
228    This probably affects quite a few places in the code.    This affects quite a few places in the code and is not trivial.
229    
230  . 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.  
231    
232  . A feature to suspend a match via a callout was once requested.  . A feature to suspend a match via a callout was once requested.
233    
234  . Option to convert results into character offsets and character lengths.  . Option to convert results into character offsets and character lengths.
235    
236  . 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
237    the job of "head".    the job of "head".
238    
239  . 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,
240    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)
241    support --outputfile=name.    support --outputfile=name.
   
 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.  
242    
243  . 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.
244    
245    . Add a user pointer to pcre_malloc/free functions -- some option would be
246    needed to retain backward compatibility.    needed to retain backward compatibility.
247    
248  . Define a union for the results from pcre_fullinfo().  . Define a union for the results from pcre_fullinfo().
249    
250  . 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
251    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
252    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
253    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.
254    
 . 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.  
   
255  . 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
256    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
257    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.
258    
259  . Should pcretest have some private locale data, to avoid relying on the  . Should pcretest have some private locale data, to avoid relying on the
260    available locales for the test data, since different OS have different ideas?    available locales for the test data, since different OS have different ideas?
261    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.
262    
263  . 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
264    them will of course slow it down.    them will of course slow it down.
265    
266  . 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
267    that is run only when the link size *is* 2; leave in some non-numbered    never wanted. This seems rather marginal.
268    debugging tests using the new /Z feature.  
269    . Check names that consist entirely of digits: PCRE allows, but do Perl and
270  . Stan Switzer's goto replacement for longjmp, which is apparently very slow on    Python, etc?
271    OS-X. This is used when stack recursion is disabled. It would be worth doing  
272    some timing tests on other OS.  . A user suggested a parameter to limit the length of string matched, for
273      example if the parameter is N, the current match should fail if the matched
274  . Someone suggested --disable-callout to save code space when callouts are    substring exceeds N. This could apply to both match functions. The value
275    never wanted. This seems rather marginal.    could be a new field in the extra block.
276    
277  . Work needs doing so that the pcregrep tests work better with different  . Callouts with arguments: (?Cn:ARG) for instance.
278    linebreak settings. Currently, some tests don't work when the input files  
279    do not have \n line endings.  . A user is going to supply a patch to generalize the API for user-specific
280      memory allocation so that it is more flexible in threaded environments. This
281  . If the fr_FR locale isn't available for testing, try "french" instead,    was promised a long time ago, and never appeared...
282    because this may be available on Windows. It means modifying the test data,  
283    however.  . Write a function that generates random matching strings for a compiled regex.
284    
285    . Write a wrapper to maintain a structure with specified runtime parameters,
286      such as recurse limit, and pass these to PCRE each time it is called. Also
287      maybe malloc and free. A user sent a prototype.
288    
289    . Pcregrep: an option to specify the output line separator, either as a string
290      or select from a fixed list. This is not dead easy, because at the moment it
291      outputs whatever is in the input file.
292    
293    . Improve the code for duplicate checking in pcre_dfa_exec(). An incomplete,
294      non-thread-safe patch showed that this can help performance for patterns
295      where there are many alternatives. However, a simple thread-safe
296      implementation that I tried made things worse in many simple cases, so this
297      is not an obviously good thing.
298    
299    . Make the longest lookbehind available via pcre_fullinfo(). This is not
300      straightforward because lookbehinds can be nested inside lookbehinds. This
301      case will have to be identified, and the amounts added. This should then give
302      the maximum possible lookbehind length. The reason for wanting this is to
303      help when implementing multi-segment matching using pcre_exec() with partial
304      matching and overlapping segments.
305    
306    . PCRE cannot at present distinguish between subpatterns with different names,
307      but the same number (created by the use of ?|). In order to do so, a way of
308      remembering *which* subpattern numbered n matched is needed. Bugzilla #760.
309      Now that (*MARK) has been implemented, it can perhaps be used as a way round
310      this problem.
311    
312    . Instead of having #ifdef HAVE_CONFIG_H in each module, put #include
313      "something" and the the #ifdef appears only in one place, in "something".
314    
315  Philip Hazel  Philip Hazel
316  Email local part: ph10  Email local part: ph10
317  Email domain: cam.ac.uk  Email domain: cam.ac.uk
318  Last updated: 24 April 2007  Last updated: 24 November 2010

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