/[pcre]/code/trunk/maint/README
ViewVC logotype

Contents of /code/trunk/maint/README

Parent Directory Parent Directory | Revision Log Revision Log


Revision 539 - (show annotations) (download)
Sun Jun 13 21:35:04 2010 UTC (4 years, 1 month ago) by ph10
File size: 15249 byte(s)
A more correct fix for the chartables bug with UTF-8 and non-std tables.

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 pcre_chartables.c.non-standard
40 This is a set of character tables that came from a Windows
41 system. It has characters greater than 128 that are set as
42 spaces, amongst other things. I kept it so that it can be
43 used for testing from time to time.
44
45 README This file.
46
47 Unicode.tables The files in this directory, DerivedGeneralCategory.txt,
48 Scripts.txt and UnicodeData.txt, were downloaded from the
49 Unicode web site. They contain information about Unicode
50 characters and scripts.
51
52 ucptest.c A short C program for testing the Unicode property macros
53 that do lookups in the pcre_ucd.c data, mainly useful after
54 rebuilding the Unicode property table. Compile and run this in
55 the "maint" directory (see comments at its head).
56
57 ucptestdata A directory containing two files, testinput1 and testoutput1,
58 to use in conjunction with the ucptest program.
59
60 utf8.c A short, freestanding C program for converting a Unicode code
61 point into a sequence of bytes in the UTF-8 encoding, and vice
62 versa. If its argument is a hex number such as 0x1234, it
63 outputs a list of the equivalent UTF-8 bytes. If its argument
64 is sequence of concatenated UTF-8 bytes (e.g. e188b4) it
65 treats them as a UTF-8 character and outputs the equivalent
66 code point in hex.
67
68
69 Updating to a new Unicode release
70 =================================
71
72 When there is a new release of Unicode, the files in Unicode.tables must be
73 refreshed from the web site. If the new version of Unicode adds new character
74 scripts, the source file ucp.h and both the MultiStage2.py and the
75 GenerateUtt.py scripts must be edited to add the new names. Then MultiStage2.py
76 can be run to generate a new version of pcre_ucd.c, and GenerateUtt.py can be
77 run to generate the tricky tables for inclusion in pcre_tables.c.
78
79 If MultiStage2.py gives the error "ValueError: list.index(x): x not in list",
80 the cause is usually a missing (or misspelt) name in the list of scripts. I
81 couldn't find a straightforward list of scripts on the Unicode site, but
82 there's a useful Wikipedia page that list them, and notes the Unicode version
83 in which they were introduced:
84
85 http://en.wikipedia.org/wiki/Unicode_scripts#Table_of_Unicode_scripts
86
87 The ucptest program can be compiled and used to check that the new tables in
88 pcre_ucd.c work properly, using the data files in ucptestdata to check a number
89 of test characters. The source file ucptest.c must be updated whenever new
90 Unicode script names are added.
91
92 Note also that both the pcresyntax.3 and pcrepattern.3 man pages contain lists
93 of Unicode script names.
94
95
96 Preparing for a PCRE release
97 ============================
98
99 This section contains a checklist of things that I consult before building a
100 distribution for a new release.
101
102 . Ensure that the version number and version date are correct in configure.ac.
103
104 . If new build options have been added, ensure that they are added to the CMake
105 files as well as to the autoconf files.
106
107 . Run ./autogen.sh to ensure everything is up-to-date.
108
109 . Compile and test with many different config options, and combinations of
110 options. The maint/ManyConfigTests script now encapsulates this testing.
111
112 . Run perltest.pl on the test data for tests 1, 4, 6, and 11. The first two can
113 be run with Perl 5.8 or >= 5.10; the last two require Perl >= 5.10. The
114 output should match the PCRE test output, apart from the version
115 identification at the start of each test. The other tests are not
116 Perl-compatible (they use various PCRE-specific features or options).
117
118 . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
119 valgrind", though that takes quite a long time.
120
121 . It may also useful to test with Electric Fence, though the fact that it
122 grumbles for missing free() calls can be a nuisance. (A missing free() in
123 pcretest is hardly a big problem.) To build with EF, use:
124
125 LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
126
127 Then all normal runs use it to check for buffer overflow. Also run everything
128 with:
129
130 EF_PROTECT_BELOW=1 <whatever>
131
132 because there have been problems with lookbehinds that looked too far.
133
134 . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
135 HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
136 used" warnings for the modules in which there is no call to memmove(). These
137 can be ignored.
138
139 . Documentation: check AUTHORS, COPYING, ChangeLog (check version and date),
140 INSTALL, LICENCE, NEWS (check version and date), NON-UNIX-USE, and README.
141 Many of these won't need changing, but over the long term things do change.
142
143 . Man pages: Check all man pages for \ not followed by e or f or " because
144 that indicates a markup error. However, there is one exception: pcredemo.3,
145 which is created from the pcredemo.c program. It contains three instances
146 of \\n.
147
148 . When the release is built, test it on a number of different operating
149 systems if possible, and using different compilers as well. For example,
150 on Solaris it is helpful to test using Sun's cc compiler as a change from
151 gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
152 needs -S 64 for pcretest to increase the stack size for test 2.
153
154
155 Making a PCRE release
156 =====================
157
158 Run PrepareRelease and commit the files that it changes (by removing trailing
159 spaces). Then run "make distcheck" to create the tarballs and the zipball.
160 Double-check with "svn status", then create an SVN tagged copy:
161
162 svn copy svn://vcs.exim.org/pcre/code/trunk \
163 svn://vcs.exim.org/pcre/code/tags/pcre-8.xx
164
165 Don't forget to update Freshmeat when the new release is out, and to tell
166 webmaster@pcre.org and the mailing list. Also, update the list of version
167 numbers in Bugzilla (edit products).
168
169
170 Future ideas (wish list)
171 ========================
172
173 This section records a list of ideas so that they do not get forgotten. They
174 vary enormously in their usefulness and potential for implementation. Some are
175 very sensible; some are rather wacky. Some have been on this list for years;
176 others are relatively new.
177
178 . Optimization
179
180 There are always ideas for new optimizations so as to speed up pattern
181 matching. Most of them try to save work by recognizing a non-match without
182 having to scan all the possibilities. These are some that I've recorded:
183
184 * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
185 slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
186 OTOH, this is pathological - the user could easily fix it.
187
188 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
189 to have little effect, and maybe makes things worse.
190
191 * "Ends with literal string" - note that a single character doesn't gain much
192 over the existing "required byte" (reqbyte) feature that just remembers one
193 byte.
194
195 * These probably need to go in pcre_study():
196
197 o Remember an initial string rather than just 1 char?
198
199 o A required byte from alternatives - not just the last char, but an
200 earlier one if common to all alternatives.
201
202 o Friedl contains other ideas.
203
204 * pcre_study() does not set initial byte flags for Unicode property types
205 such as \p; I don't know how much benefit there would be for, for example,
206 setting the bits for 0-9 and all bytes >= xC0 when a pattern starts with
207 \p{N}.
208
209 * There is scope for more "auto-possessifying" in connection with \p and \P.
210
211 . If Perl gets to a consistent state over the settings of capturing sub-
212 patterns inside repeats, see if we can match it. One example of the
213 difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
214 leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
215 because I think it needs much more state to be remembered.
216
217 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
218
219 . Unicode
220
221 * A different approach to Unicode might be to use a typedef to do everything
222 in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
223 new typedef to distinguish data from bits of compiled pattern that are in
224 bytes, I think. There would need to be conversion functions in and out. I
225 don't think this is particularly trivial - and anyway, Unicode now has
226 characters that need more than 16 bits, so is this at all sensible?
227
228 * There has been a request for direct support of 16-bit characters and
229 UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
230 is this worth it at all? One possible way of handling 16-bit characters
231 would be to "load" them in the same way that UTF-8 characters are loaded.
232
233 . Allow errorptr and erroroffset to be NULL. I don't like this idea.
234
235 . Line endings:
236
237 * Option to use NUL as a line terminator in subject strings. This could now
238 be done relatively easily since the extension to support LF, CR, and CRLF.
239 If it is done, a suitable option for pcregrep is also required.
240
241 . Option to provide the pattern with a length instead of with a NUL terminator.
242 This affects quite a few places in the code and is not trivial.
243
244 . Catch SIGSEGV for stack overflows?
245
246 . A feature to suspend a match via a callout was once requested.
247
248 . Option to convert results into character offsets and character lengths.
249
250 . Option for pcregrep to scan only the start of a file. I am not keen - this is
251 the job of "head".
252
253 . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
254 preceded by a blank line, instead of adding it to every matched line, and (b)
255 support --outputfile=name.
256
257 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 8.
258
259 . Add a user pointer to pcre_malloc/free functions -- some option would be
260 needed to retain backward compatibility.
261
262 . Define a union for the results from pcre_fullinfo().
263
264 . Provide a "random access to the subject" facility so that the way in which it
265 is stored is independent of PCRE. For efficiency, it probably isn't possible
266 to switch this dynamically. It would have to be specified when PCRE was
267 compiled. PCRE would then call a function every time it wanted a character.
268
269 . Wild thought: the ability to compile from PCRE's internal byte code to a real
270 FSM and a very fast (third) matcher to process the result. There would be
271 even more restrictions than for pcre_dfa_exec(), however. This is not easy.
272
273 . Should pcretest have some private locale data, to avoid relying on the
274 available locales for the test data, since different OS have different ideas?
275 This won't be as thorough a test, but perhaps that doesn't really matter.
276
277 . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
278 them will of course slow it down.
279
280 . Someone suggested --disable-callout to save code space when callouts are
281 never wanted. This seems rather marginal.
282
283 . Check names that consist entirely of digits: PCRE allows, but do Perl and
284 Python, etc?
285
286 . A user suggested a parameter to limit the length of string matched, for
287 example if the parameter is N, the current match should fail if the matched
288 substring exceeds N. This could apply to both match functions. The value
289 could be a new field in the extra block.
290
291 . Callouts with arguments: (?Cn:ARG) for instance.
292
293 . A user is going to supply a patch to generalize the API for user-specific
294 memory allocation so that it is more flexible in threaded environments. This
295 was promised a long time ago, and never appeared...
296
297 . Write a function that generates random matching strings for a compiled regex.
298
299 . Write a wrapper to maintain a structure with specified runtime parameters,
300 such as recurse limit, and pass these to PCRE each time it is called. Also
301 maybe malloc and free. A user sent a prototype.
302
303 . Pcregrep: an option to specify the output line separator, either as a string
304 or select from a fixed list. This is not dead easy, because at the moment it
305 outputs whatever is in the input file.
306
307 . Improve the code for duplicate checking in pcre_dfa_exec(). An incomplete,
308 non-thread-safe patch showed that this can help performance for patterns
309 where there are many alternatives. However, a simple thread-safe
310 implementation that I tried made things worse in many simple cases, so this
311 is not an obviously good thing.
312
313 . Make the longest lookbehind available via pcre_fullinfo(). This is not
314 straightforward because lookbehinds can be nested inside lookbehinds. This
315 case will have to be identified, and the amounts added. This should then give
316 the maximum possible lookbehind length. The reason for wanting this is to
317 help when implementing multi-segment matching using pcre_exec() with partial
318 matching and overlapping segments.
319
320 . PCRE cannot at present distinguish between subpatterns with different names,
321 but the same number (created by the use of ?|). In order to do so, a way of
322 remembering *which* subpattern numbered n matched is needed. Bugzilla #760.
323 Now that (*MARK) has been implemented, it can perhaps be used as a way round
324 this problem.
325
326 . Instead of having #ifdef HAVE_CONFIG_H in each module, put #include
327 "something" and the the #ifdef appears only in one place, in "something".
328
329 Philip Hazel
330 Email local part: ph10
331 Email domain: cam.ac.uk
332 Last updated: 03 June 2010

webmaster@exim.org
ViewVC Help
Powered by ViewVC 1.1.12