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