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Contents of /code/trunk/maint/README

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More of the UCP speedup update.
2 ---------------------------
4 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
6 part of the PCRE distribution tarballs. This document describes these files and
7 also contains some notes for maintainers. Its contents are:
9 Files in the maint directory
10 Updating to a new Unicode release
11 Preparing for a PCRE release
12 Making a PCRE release
13 Long-term ideas (wish list)
16 Files in the maint directory
17 ----------------------------
19 ----------------- This file is now OBSOLETE and no longer used ----------------
20 Builducptable A Perl script that creates the contents of the ucptable.h file
21 from two Unicode data files, which themselves are downloaded
22 from the Unicode web site. Run this script in the "maint"
23 directory.
24 ----------------- This file is now OBSOLETE and no longer used ----------------
26 ManyConfigTests A shell script that runs "configure, make, test" a number of
27 times with different configuration settings.
29 MultiStage2.py A Python script that generates the file pcre_ucd.c from three
30 Unicode data tables, which are themselves downloaded from the
31 Unicode web site. Run this script in the "maint" directory.
32 The generated file contains the tables for a 2-stage lookup
33 of Unicode properties.
35 Unicode.tables The files in this directory, DerivedGeneralCategory.txt,
36 Scripts.txt and UnicodeData.txt, were downloaded from the
37 Unicode web site. They contain information about Unicode
38 characters and scripts.
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.
45 ucptestdata A directory containing two files, testinput1 and testoutput1,
46 to use in conjunction with the ucptest program.
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.
57 Updating to a new Unicode release
58 ---------------------------------
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.
67 Preparing for a PCRE release
68 ----------------------------
70 This section contains a checklist of things that I consult before building a
71 distribution for a new release.
73 . Ensure that the version number and version date are correct in configure.ac,
74 ChangeLog, and NEWS.
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.
79 . Run ./autogen.sh to ensure everything is up-to-date.
81 . Compile and test with many different config options, and combinations of
82 options. The maint/ManyConfigTests script now encapsulates this testing.
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).
88 . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
89 valgrind", though that takes quite a long time.
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:
95 LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
97 Then all normal runs use it to check for buffer overflow. Also run everything
98 with:
100 EF_PROTECT_BELOW=1 <whatever>
102 because there have been problems with lookbehinds that looked too far.
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.
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.
113 . Man pages: Check all man pages for \ not followed by e or f or " because
114 that indicates a markup error.
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.
123 Making a PCRE release
124 ---------------------
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:
130 svn copy svn://vcs.exim.org/pcre/code/trunk \
131 svn://vcs.exim.org/pcre/code/tags/pcre-7.x
133 Don't forget to update Freshmeat when the new release is out, and to tell
134 webmaster@pcre.org and the mailing list.
137 Future ideas (wish list)
138 ------------------------
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.
145 . Optimization
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:
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.
155 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
156 to have little effect, and maybe makes things worse.
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.
162 * These probably need to go in study():
164 o Remember an initial string rather than just 1 char?
166 o A required byte from alternatives - not just the last char, but an
167 earlier one if common to all alternatives.
169 o Minimum length of subject needed.
171 o Friedl contains other ideas.
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.
179 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
181 . Unicode
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.
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?
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.
200 . Allow errorptr and erroroffset to be NULL. I don't like this idea.
202 . Line endings:
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.
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.
211 . Catch SIGSEGV for stack overflows?
213 . A feature to suspend a match via a callout was once requested.
215 . Option to convert results into character offsets and character lengths.
217 . Option for pcregrep to scan only the start of a file. I am not keen - this is
218 the job of "head".
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.
224 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
226 . Add a user pointer to pcre_malloc/free functions -- some option would be
227 needed to retain backward compatibility.
229 . Define a union for the results from pcre_fullinfo().
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.
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.
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.
244 . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
245 them will of course slow it down.
247 . Someone suggested --disable-callout to save code space when callouts are
248 never wanted. This seems rather marginal.
250 . Check names that consist entirely of digits: PCRE allows, but do Perl and
251 Python, etc?
253 Philip Hazel
254 Email local part: ph10
255 Email domain: cam.ac.uk
256 Last updated: 02 July 2008

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