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code/trunk/maintain/README revision 111 by ph10, Thu Mar 8 16:53:09 2007 UTC code/trunk/maint/README revision 350 by ph10, Wed Jul 2 19:18:41 2008 UTC
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1  The files in the "maintain" directory of the PCRE source contain data, scripts,  MAINTENANCE README FOR PCRE
2  and programs that are used for the maintenance of PCRE, but do not form part of  ---------------------------
3  the PCRE distribution tarballs.  
4    The files in the "maint" directory of the PCRE source contain data, scripts,
5  Builducptable   A Perl script that creates the contents of the ucptable.h file  and programs that are used for the maintenance of PCRE, but which do not form
6                  from two Unicode data files, which themselves are downloaded  part of the PCRE distribution tarballs. This document describes these files and
7                  from the Unicode web site. Run this script in the "maintain"  also contains some notes for maintainers. Its contents are:
8                  directory.  
9      Files in the maint directory
10  Tech.Notes      Some notes about the internals of the PCRE code.    Updating to a new Unicode release
11      Preparing for a PCRE release
12  Unicode.tables  The files in this directory, Scripts.txt and UnicodeData.txt,    Making a PCRE release
13                  were downloaded from the Unicode web site. They contain    Long-term ideas (wish list)
14                  information about Unicode characters and scripts.  
15    
16  ucptest.c       A short C program for testing the Unicode property functions in  Files in the maint directory
17                  pcre_ucp_searchfuncs.c, mainly useful after rebuilding the  ----------------------------
18                  Unicode property table. Compile and run this in the "maintain"  
19                  directory.  ----------------- This file is now OBSOLETE and no longer used ----------------
20    Builducptable    A Perl script that creates the contents of the ucptable.h file
21  ucptestdata     A directory containing two files, testinput1 and testoutput1,                   from two Unicode data files, which themselves are downloaded
22                  to use in conjunction with the ucptest program.                   from the Unicode web site. Run this script in the "maint"
23                     directory.
24  utf8.c          A short, freestanding C program for converting a Unicode code  ----------------- This file is now OBSOLETE and no longer used ----------------
25                  point into a sequence of bytes in the UTF-8 encoding, and vice  
26                  versa. If its argument is a hex number such as 0x1234, it  ManyConfigTests  A shell script that runs "configure, make, test" a number of
27                  outputs a list of the equivalent UTF-8 bytes. If its argument                   times with different configuration settings.
28                  is sequence of concatenated UTF-8 bytes (e.g. e188b4) it treats  
29                  them as a UTF-8 character and outputs the equivalent code point  MultiStage2.py   A Python script that generates the file pcre_ucd.c from three
30                  in hex.                   Unicode data tables, which are themselves downloaded from the
31                     Unicode web site. Run this script in the "maint" directory.
32  When there is a new release of Unicode, the files in Unicode.tables must be                   The generated file contains the tables for a 2-stage lookup
33  refreshed from the web site, and the Buildupctable script can then be run to                   of Unicode properties.
34  generate a new version of ucptable.h. The ucptest program can be used to check  
35  that the resulting table works properly, using the data files in ucptestdata to  Unicode.tables   The files in this directory, DerivedGeneralCategory.txt,
36  check a number of test characters.                   Scripts.txt and UnicodeData.txt, were downloaded from the
37                     Unicode web site. They contain information about Unicode
38  ****                   characters and scripts.
39    
40    ucptest.c        A short C program for testing the Unicode property macros
41                     that do lookups in the pcre_ucd.c data, mainly useful after
42                     rebuilding the Unicode property table. Compile and run this in
43                     the "maint" directory.
44    
45    ucptestdata      A directory containing two files, testinput1 and testoutput1,
46                     to use in conjunction with the ucptest program.
47    
48    utf8.c           A short, freestanding C program for converting a Unicode code
49                     point into a sequence of bytes in the UTF-8 encoding, and vice
50                     versa. If its argument is a hex number such as 0x1234, it
51                     outputs a list of the equivalent UTF-8 bytes. If its argument
52                     is sequence of concatenated UTF-8 bytes (e.g. e188b4) it
53                     treats them as a UTF-8 character and outputs the equivalent
54                     code point in hex.
55    
56    
57    Updating to a new Unicode release
58    ---------------------------------
59    
60    When there is a new release of Unicode, the files in Unicode.tables must be
61    refreshed from the web site, and the MultiStage2.py script can then be run to
62    generate a new version of pcre_ucd.c. The ucptest program can be used to check
63    that the resulting table works properly, using the data files in ucptestdata to
64    check a number of test characters.
65    
66    
67    Preparing for a PCRE release
68    ----------------------------
69    
70    This section contains a checklist of things that I consult before building a
71    distribution for a new release.
72    
73    . Ensure that the version number and version date are correct in configure.ac,
74      ChangeLog, and NEWS.
75    
76    . If new build options have been added, ensure that they are added to the CMake
77      files as well as to the autoconf files.
78    
79    . Run ./autogen.sh to ensure everything is up-to-date.
80    
81    . Compile and test with many different config options, and combinations of
82      options. The maint/ManyConfigTests script now encapsulates this testing.
83    
84    . Run perltest.pl on the test data for tests 1 and 4. The output should match
85      the PCRE test output, apart from the version identification at the top. The
86      other tests are not Perl-compatible (they use various special PCRE options).
87    
88    . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
89      valgrind", though that takes quite a long time.
90    
91    . It may also useful to test with Electric Fence, though the fact that it
92      grumbles for missing free() calls can be a nuisance. (A missing free() in
93      pcretest is hardly a big problem.) To build with EF, use:
94    
95        LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
96    
97      Then all normal runs use it to check for buffer overflow. Also run everything
98      with:
99    
100        EF_PROTECT_BELOW=1 <whatever>
101    
102      because there have been problems with lookbehinds that looked too far.
103    
104    . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
105      HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
106      used" warnings for the modules in which there is no call to memmove(). These
107      can be ignored.
108    
109    . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,
110      LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't
111      need changing, but over the long term things do change.
112    
113    . Man pages: Check all man pages for \ not followed by e or f or " because
114      that indicates a markup error.
115    
116    . When the release is built, test it on a number of different operating
117      systems if possible, and using different compilers as well. For example,
118      on Solaris it is helpful to test using Sun's cc compiler as a change from
119      gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
120      needs -S 64 for pcretest to increase the stack size for test 2.
121    
122    
123    Making a PCRE release
124    ---------------------
125    
126    Run PrepareRelease and commit the files that it changes (by removing trailing
127    spaces). Then run "make distcheck" to create the tarballs and the zipball.
128    Double-check with "svn status", then create an SVN tagged copy:
129    
130      svn copy svn://vcs.exim.org/pcre/code/trunk \
131               svn://vcs.exim.org/pcre/code/tags/pcre-7.x
132    
133    Don't forget to update Freshmeat when the new release is out, and to tell
134    webmaster@pcre.org and the mailing list.
135    
136    
137    Future ideas (wish list)
138    ------------------------
139    
140    This section records a list of ideas so that they do not get forgotten. They
141    vary enormously in their usefulness and potential for implementation. Some are
142    very sensible; some are rather wacky. Some have been on this list for years;
143    others are relatively new.
144    
145    . Optimization
146    
147      There are always ideas for new optimizations so as to speed up pattern
148      matching. Most of them try to save work by recognizing a non-match without
149      having to scan all the possibilities. These are some that I've recorded:
150    
151      * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
152        slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
153        OTOH, this is pathological - the user could easily fix it.
154    
155      * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
156        to have little effect, and maybe makes things worse.
157    
158      * "Ends with literal string" - note that a single character doesn't gain much
159        over the existing "required byte" (reqbyte) feature that just saves one
160        byte.
161    
162      * These probably need to go in study():
163    
164        o Remember an initial string rather than just 1 char?
165    
166        o A required byte from alternatives - not just the last char, but an
167          earlier one if common to all alternatives.
168    
169        o Minimum length of subject needed.
170    
171        o Friedl contains other ideas.
172    
173    . If Perl gets to a consistent state over the settings of capturing sub-
174      patterns inside repeats, see if we can match it. One example of the
175      difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
176      leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
177      because I think it needs much more state to be remembered.
178    
179    . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
180    
181    . Unicode
182    
183      * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX
184        character classes. For the moment, I've chosen not to support this for
185        backward compatibility, for speed, and because it would be messy to
186        implement.
187    
188      * A different approach to Unicode might be to use a typedef to do everything
189        in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
190        new typedef to distinguish data from bits of compiled pattern that are in
191        bytes, I think. There would need to be conversion functions in and out. I
192        don't think this is particularly trivial - and anyway, Unicode now has
193        characters that need more than 16 bits, so is this at all sensible?
194    
195      * There has been a request for direct support of 16-bit characters and
196        UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
197        is this worth it at all? One possible way of handling 16-bit characters
198        would be to "load" them in the same way that UTF-8 characters are loaded.
199    
200    . Allow errorptr and erroroffset to be NULL. I don't like this idea.
201    
202    . Line endings:
203    
204      * Option to use NUL as a line terminator in subject strings. This could now
205        be done relatively easily since the extension to support LF, CR, and CRLF.
206        If this is done, a suitable option for pcregrep is also required.
207    
208    . Option to provide the pattern with a length instead of with a NUL terminator.
209      This probably affects quite a few places in the code.
210    
211    . Catch SIGSEGV for stack overflows?
212    
213    . A feature to suspend a match via a callout was once requested.
214    
215    . Option to convert results into character offsets and character lengths.
216    
217    . Option for pcregrep to scan only the start of a file. I am not keen - this is
218      the job of "head".
219    
220    . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
221      preceded by a blank line, instead of adding it to every matched line, and (b)
222      support --outputfile=name.
223    
224    . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
225    
226    . Add a user pointer to pcre_malloc/free functions -- some option would be
227      needed to retain backward compatibility.
228    
229    . Define a union for the results from pcre_fullinfo().
230    
231    . Provide a "random access to the subject" facility so that the way in which it
232      is stored is independent of PCRE. For efficiency, it probably isn't possible
233      to switch this dynamically. It would have to be specified when PCRE was
234      compiled. PCRE would then call a function every time it wanted a character.
235    
236    . Wild thought: the ability to compile from PCRE's internal byte code to a real
237      FSM and a very fast (third) matcher to process the result. There would be
238      even more restrictions than for pcre_dfa_exec(), however. This is not easy.
239    
240    . Should pcretest have some private locale data, to avoid relying on the
241      available locales for the test data, since different OS have different ideas?
242      This won't be as thorough a test, but perhaps that doesn't really matter.
243    
244    . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
245      them will of course slow it down.
246    
247    . Someone suggested --disable-callout to save code space when callouts are
248      never wanted. This seems rather marginal.
249    
250    . Check names that consist entirely of digits: PCRE allows, but do Perl and
251      Python, etc?
252    
253    Philip Hazel
254    Email local part: ph10
255    Email domain: cam.ac.uk
256    Last updated: 02 July 2008

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