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

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