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Update Unicode tables to Unicode version 5.2.0.
1 MAINTENANCE README FOR PCRE
2 ---------------------------
3
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:
8
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)
14
15
16 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
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 ----------------
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
31 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 README This file.
40
41 Unicode.tables The files in this directory, DerivedGeneralCategory.txt,
42 Scripts.txt and UnicodeData.txt, were downloaded from the
43 Unicode web site. They contain information about Unicode
44 characters and scripts.
45
46 ucptest.c A short C program for testing the Unicode property macros
47 that do lookups in the pcre_ucd.c data, mainly useful after
48 rebuilding the Unicode property table. Compile and run this in
49 the "maint" directory (see comments at its head).
50
51 ucptestdata A directory containing two files, testinput1 and testoutput1,
52 to use in conjunction with the ucptest program.
53
54 utf8.c A short, freestanding C program for converting a Unicode code
55 point into a sequence of bytes in the UTF-8 encoding, and vice
56 versa. If its argument is a hex number such as 0x1234, it
57 outputs a list of the equivalent UTF-8 bytes. If its argument
58 is sequence of concatenated UTF-8 bytes (e.g. e188b4) it
59 treats them as a UTF-8 character and outputs the equivalent
60 code point in hex.
61
62
63 Updating to a new Unicode release
64 ---------------------------------
65
66 When there is a new release of Unicode, the files in Unicode.tables must be
67 refreshed from the web site. If the new version of Unicode adds new character
68 scripts, the source file ucp.h and both the MultiStage2.py and the
69 GenerateUtt.py scripts must be edited to add the new names. Then MultiStage2.py
70 can be run to generate a new version of pcre_ucd.c, and GenerateUtt.py can be
71 run to generate the tricky tables for inclusion in pcre_tables.c.
72
73 If MultiStage2.py gives the error "ValueError: list.index(x): x not in list",
74 the cause is usually a missing (or misspelt) name in the list of scripts. I
75 couldn't find a straightforward list of scripts on the Unicode site, but
76 there's a useful Wikipedia page that list them, and notes the Unicode version
77 in which they were introduced:
78
79 http://en.wikipedia.org/wiki/Unicode_scripts#Table_of_Unicode_scripts
80
81 The ucptest program can be compiled and used to check that the new tables in
82 pcre_ucd.c work properly, using the data files in ucptestdata to check a number
83 of test characters. The source file ucptest.c must be updated whenever new
84 Unicode script names are added.
85
86 Note also that both the pcresyntax.3 and pcrepattern.3 man pages contain lists
87 of Unicode script names.
88
89
90 Preparing for a PCRE release
91 ----------------------------
92
93 This section contains a checklist of things that I consult before building a
94 distribution for a new release.
95
96 . Ensure that the version number and version date are correct in configure.ac.
97
98 . If new build options have been added, ensure that they are added to the CMake
99 files as well as to the autoconf files.
100
101 . Run ./autogen.sh to ensure everything is up-to-date.
102
103 . Compile and test with many different config options, and combinations of
104 options. The maint/ManyConfigTests script now encapsulates this testing.
105
106 . Run perltest.pl on the test data for tests 1, 4, 6, and 11. The first two can
107 be run with Perl 5.8 or 5.10; the last two require Perl 5.10. The output
108 should match the PCRE test output, apart from the version identification at
109 the start of each test. The other tests are not Perl-compatible (they use
110 various PCRE-specific features or options).
111
112 . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
113 valgrind", though that takes quite a long time.
114
115 . It may also useful to test with Electric Fence, though the fact that it
116 grumbles for missing free() calls can be a nuisance. (A missing free() in
117 pcretest is hardly a big problem.) To build with EF, use:
118
119 LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
120
121 Then all normal runs use it to check for buffer overflow. Also run everything
122 with:
123
124 EF_PROTECT_BELOW=1 <whatever>
125
126 because there have been problems with lookbehinds that looked too far.
127
128 . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
129 HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
130 used" warnings for the modules in which there is no call to memmove(). These
131 can be ignored.
132
133 . Documentation: check AUTHORS, COPYING, ChangeLog (check version and date),
134 INSTALL, LICENCE, NEWS (check version and date), NON-UNIX-USE, and README.
135 Many of these won't need changing, but over the long term things do change.
136
137 . Man pages: Check all man pages for \ not followed by e or f or " because
138 that indicates a markup error.
139
140 . When the release is built, test it on a number of different operating
141 systems if possible, and using different compilers as well. For example,
142 on Solaris it is helpful to test using Sun's cc compiler as a change from
143 gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
144 needs -S 64 for pcretest to increase the stack size for test 2.
145
146
147 Making a PCRE release
148 ---------------------
149
150 Run PrepareRelease and commit the files that it changes (by removing trailing
151 spaces). Then run "make distcheck" to create the tarballs and the zipball.
152 Double-check with "svn status", then create an SVN tagged copy:
153
154 svn copy svn://vcs.exim.org/pcre/code/trunk \
155 svn://vcs.exim.org/pcre/code/tags/pcre-8.xx
156
157 Don't forget to update Freshmeat when the new release is out, and to tell
158 webmaster@pcre.org and the mailing list.
159
160
161 Future ideas (wish list)
162 ------------------------
163
164 This section records a list of ideas so that they do not get forgotten. They
165 vary enormously in their usefulness and potential for implementation. Some are
166 very sensible; some are rather wacky. Some have been on this list for years;
167 others are relatively new.
168
169 . Optimization
170
171 There are always ideas for new optimizations so as to speed up pattern
172 matching. Most of them try to save work by recognizing a non-match without
173 having to scan all the possibilities. These are some that I've recorded:
174
175 * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
176 slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
177 OTOH, this is pathological - the user could easily fix it.
178
179 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
180 to have little effect, and maybe makes things worse.
181
182 * "Ends with literal string" - note that a single character doesn't gain much
183 over the existing "required byte" (reqbyte) feature that just remembers one
184 byte.
185
186 * These probably need to go in study():
187
188 o Remember an initial string rather than just 1 char?
189
190 o A required byte from alternatives - not just the last char, but an
191 earlier one if common to all alternatives.
192
193 o Friedl contains other ideas.
194
195 . If Perl gets to a consistent state over the settings of capturing sub-
196 patterns inside repeats, see if we can match it. One example of the
197 difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
198 leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
199 because I think it needs much more state to be remembered.
200
201 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
202
203 . Unicode
204
205 * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX
206 character classes. For the moment, I've chosen not to support this for
207 backward compatibility, for speed, and because it would be messy to
208 implement.
209
210 * A different approach to Unicode might be to use a typedef to do everything
211 in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
212 new typedef to distinguish data from bits of compiled pattern that are in
213 bytes, I think. There would need to be conversion functions in and out. I
214 don't think this is particularly trivial - and anyway, Unicode now has
215 characters that need more than 16 bits, so is this at all sensible?
216
217 * There has been a request for direct support of 16-bit characters and
218 UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
219 is this worth it at all? One possible way of handling 16-bit characters
220 would be to "load" them in the same way that UTF-8 characters are loaded.
221
222 . Allow errorptr and erroroffset to be NULL. I don't like this idea.
223
224 . Line endings:
225
226 * Option to use NUL as a line terminator in subject strings. This could now
227 be done relatively easily since the extension to support LF, CR, and CRLF.
228 If it is done, a suitable option for pcregrep is also required.
229
230 . Option to provide the pattern with a length instead of with a NUL terminator.
231 This affects quite a few places in the code and is not trivial.
232
233 . Catch SIGSEGV for stack overflows?
234
235 . A feature to suspend a match via a callout was once requested.
236
237 . Option to convert results into character offsets and character lengths.
238
239 . Option for pcregrep to scan only the start of a file. I am not keen - this is
240 the job of "head".
241
242 . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
243 preceded by a blank line, instead of adding it to every matched line, and (b)
244 support --outputfile=name.
245
246 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 8.
247
248 . Add a user pointer to pcre_malloc/free functions -- some option would be
249 needed to retain backward compatibility.
250
251 . Define a union for the results from pcre_fullinfo().
252
253 . Provide a "random access to the subject" facility so that the way in which it
254 is stored is independent of PCRE. For efficiency, it probably isn't possible
255 to switch this dynamically. It would have to be specified when PCRE was
256 compiled. PCRE would then call a function every time it wanted a character.
257
258 . Wild thought: the ability to compile from PCRE's internal byte code to a real
259 FSM and a very fast (third) matcher to process the result. There would be
260 even more restrictions than for pcre_dfa_exec(), however. This is not easy.
261
262 . Should pcretest have some private locale data, to avoid relying on the
263 available locales for the test data, since different OS have different ideas?
264 This won't be as thorough a test, but perhaps that doesn't really matter.
265
266 . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
267 them will of course slow it down.
268
269 . Someone suggested --disable-callout to save code space when callouts are
270 never wanted. This seems rather marginal.
271
272 . Check names that consist entirely of digits: PCRE allows, but do Perl and
273 Python, etc?
274
275 . A user suggested a parameter to limit the length of string matched, for
276 example if the parameter is N, the current match should fail if the matched
277 substring exceeds N. This could apply to both match functions. The value
278 could be a new field in the extra block.
279
280 . Callouts with arguments: (?Cn:ARG) for instance.
281
282 . A user is going to supply a patch to generalize the API for user-specific
283 memory allocation so that it is more flexible in threaded environments. Thiw
284 was promised a long time ago, and never appeared...
285
286 . Write a function that generates random matching strings for a compiled regex.
287
288 . Write a wrapper to maintain a structure with specified runtime parameters,
289 such as recurse limit, and pass these to PCRE each time it is called. Also
290 maybe malloc and free. A user sent a prototype.
291
292 . Pcregrep: an option to specify the output line separator, either as a string
293 or select from a fixed list. This is not dead easy, because at the moment it
294 outputs whatever is in the input file.
295
296 . Improve the code for duplicate checking in pcre_dfa_exec(). An incomplete,
297 non-thread-safe patch showed that this can help performance for patterns
298 where there are many alternatives. However, a simple thread-safe
299 implementation that I tried made things worse in many simple cases, so this
300 is not an obviously good thing.
301
302 . Make the longest lookbehind available via pcre_fullinfo(). This is not
303 straightforward because lookbehinds can be nested inside lookbehinds. This
304 case will have to be identified, and the amounts added. This should then give
305 the maximum possible lookbehind length. The reason for wanting this is to
306 help when implementing multi-segment matching using pcre_exec() with partial
307 matching and overlapping segments.
308
309 . PCRE cannot at present distinguish between subpatterns with different names,
310 but the same number (created by the use of ?|). In order to do so, a way of
311 remembering *which* subpattern numbered n matched is needed. Bugzilla #760.
312
313 Philip Hazel
314 Email local part: ph10
315 Email domain: cam.ac.uk
316 Last updated: 26 September 2009

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