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Revision 351 - (show annotations) (download)
Fri Jul 4 18:27:16 2008 UTC (5 years, 9 months ago) by ph10
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Final tidies for new Unicode property code; upgrade to Unicode 5.1.0.

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 Unicode.tables The files in this directory, DerivedGeneralCategory.txt,
40 Scripts.txt and UnicodeData.txt, were downloaded from the
41 Unicode web site. They contain information about Unicode
42 characters and scripts.
43
44 ucptest.c A short C program for testing the Unicode property macros
45 that do lookups in the pcre_ucd.c data, mainly useful after
46 rebuilding the Unicode property table. Compile and run this in
47 the "maint" directory (see comments at its head).
48
49 ucptestdata A directory containing two files, testinput1 and testoutput1,
50 to use in conjunction with the ucptest program.
51
52 utf8.c A short, freestanding C program for converting a Unicode code
53 point into a sequence of bytes in the UTF-8 encoding, and vice
54 versa. If its argument is a hex number such as 0x1234, it
55 outputs a list of the equivalent UTF-8 bytes. If its argument
56 is sequence of concatenated UTF-8 bytes (e.g. e188b4) it
57 treats them as a UTF-8 character and outputs the equivalent
58 code point in hex.
59
60
61 Updating to a new Unicode release
62 ---------------------------------
63
64 When there is a new release of Unicode, the files in Unicode.tables must be
65 refreshed from the web site. If the new version of Unicode adds new character
66 scripts, both the MultiStage2.py and the GenerateUtt.py scripts must be edited
67 to add the new names. Then the MultiStage2.py script can then be run to
68 generate a new version of pcre_ucd.c and the GenerateUtt.py can be run to
69 generate the tricky tables in pcre_tables.c.
70
71 The ucptest program can then be compiled and used to check that the new tables
72 in pcre_ucd.c work properly, using the data files in ucptestdata to check a
73 number of test characters.
74
75
76 Preparing for a PCRE release
77 ----------------------------
78
79 This section contains a checklist of things that I consult before building a
80 distribution for a new release.
81
82 . Ensure that the version number and version date are correct in configure.ac,
83 ChangeLog, and NEWS.
84
85 . If new build options have been added, ensure that they are added to the CMake
86 files as well as to the autoconf files.
87
88 . Run ./autogen.sh to ensure everything is up-to-date.
89
90 . Compile and test with many different config options, and combinations of
91 options. The maint/ManyConfigTests script now encapsulates this testing.
92
93 . Run perltest.pl on the test data for tests 1 and 4. The output should match
94 the PCRE test output, apart from the version identification at the top. The
95 other tests are not Perl-compatible (they use various special PCRE options).
96
97 . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
98 valgrind", though that takes quite a long time.
99
100 . It may also useful to test with Electric Fence, though the fact that it
101 grumbles for missing free() calls can be a nuisance. (A missing free() in
102 pcretest is hardly a big problem.) To build with EF, use:
103
104 LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
105
106 Then all normal runs use it to check for buffer overflow. Also run everything
107 with:
108
109 EF_PROTECT_BELOW=1 <whatever>
110
111 because there have been problems with lookbehinds that looked too far.
112
113 . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
114 HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
115 used" warnings for the modules in which there is no call to memmove(). These
116 can be ignored.
117
118 . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,
119 LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't
120 need changing, but over the long term things do change.
121
122 . Man pages: Check all man pages for \ not followed by e or f or " because
123 that indicates a markup error.
124
125 . When the release is built, test it on a number of different operating
126 systems if possible, and using different compilers as well. For example,
127 on Solaris it is helpful to test using Sun's cc compiler as a change from
128 gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
129 needs -S 64 for pcretest to increase the stack size for test 2.
130
131
132 Making a PCRE release
133 ---------------------
134
135 Run PrepareRelease and commit the files that it changes (by removing trailing
136 spaces). Then run "make distcheck" to create the tarballs and the zipball.
137 Double-check with "svn status", then create an SVN tagged copy:
138
139 svn copy svn://vcs.exim.org/pcre/code/trunk \
140 svn://vcs.exim.org/pcre/code/tags/pcre-7.x
141
142 Don't forget to update Freshmeat when the new release is out, and to tell
143 webmaster@pcre.org and the mailing list.
144
145
146 Future ideas (wish list)
147 ------------------------
148
149 This section records a list of ideas so that they do not get forgotten. They
150 vary enormously in their usefulness and potential for implementation. Some are
151 very sensible; some are rather wacky. Some have been on this list for years;
152 others are relatively new.
153
154 . Optimization
155
156 There are always ideas for new optimizations so as to speed up pattern
157 matching. Most of them try to save work by recognizing a non-match without
158 having to scan all the possibilities. These are some that I've recorded:
159
160 * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
161 slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
162 OTOH, this is pathological - the user could easily fix it.
163
164 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
165 to have little effect, and maybe makes things worse.
166
167 * "Ends with literal string" - note that a single character doesn't gain much
168 over the existing "required byte" (reqbyte) feature that just saves one
169 byte.
170
171 * These probably need to go in study():
172
173 o Remember an initial string rather than just 1 char?
174
175 o A required byte from alternatives - not just the last char, but an
176 earlier one if common to all alternatives.
177
178 o Minimum length of subject needed.
179
180 o Friedl contains other ideas.
181
182 . If Perl gets to a consistent state over the settings of capturing sub-
183 patterns inside repeats, see if we can match it. One example of the
184 difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
185 leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
186 because I think it needs much more state to be remembered.
187
188 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
189
190 . Unicode
191
192 * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX
193 character classes. For the moment, I've chosen not to support this for
194 backward compatibility, for speed, and because it would be messy to
195 implement.
196
197 * A different approach to Unicode might be to use a typedef to do everything
198 in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
199 new typedef to distinguish data from bits of compiled pattern that are in
200 bytes, I think. There would need to be conversion functions in and out. I
201 don't think this is particularly trivial - and anyway, Unicode now has
202 characters that need more than 16 bits, so is this at all sensible?
203
204 * There has been a request for direct support of 16-bit characters and
205 UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
206 is this worth it at all? One possible way of handling 16-bit characters
207 would be to "load" them in the same way that UTF-8 characters are loaded.
208
209 . Allow errorptr and erroroffset to be NULL. I don't like this idea.
210
211 . Line endings:
212
213 * Option to use NUL as a line terminator in subject strings. This could now
214 be done relatively easily since the extension to support LF, CR, and CRLF.
215 If this is done, a suitable option for pcregrep is also required.
216
217 . Option to provide the pattern with a length instead of with a NUL terminator.
218 This probably affects quite a few places in the code.
219
220 . Catch SIGSEGV for stack overflows?
221
222 . A feature to suspend a match via a callout was once requested.
223
224 . Option to convert results into character offsets and character lengths.
225
226 . Option for pcregrep to scan only the start of a file. I am not keen - this is
227 the job of "head".
228
229 . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
230 preceded by a blank line, instead of adding it to every matched line, and (b)
231 support --outputfile=name.
232
233 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
234
235 . Add a user pointer to pcre_malloc/free functions -- some option would be
236 needed to retain backward compatibility.
237
238 . Define a union for the results from pcre_fullinfo().
239
240 . Provide a "random access to the subject" facility so that the way in which it
241 is stored is independent of PCRE. For efficiency, it probably isn't possible
242 to switch this dynamically. It would have to be specified when PCRE was
243 compiled. PCRE would then call a function every time it wanted a character.
244
245 . Wild thought: the ability to compile from PCRE's internal byte code to a real
246 FSM and a very fast (third) matcher to process the result. There would be
247 even more restrictions than for pcre_dfa_exec(), however. This is not easy.
248
249 . Should pcretest have some private locale data, to avoid relying on the
250 available locales for the test data, since different OS have different ideas?
251 This won't be as thorough a test, but perhaps that doesn't really matter.
252
253 . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
254 them will of course slow it down.
255
256 . Someone suggested --disable-callout to save code space when callouts are
257 never wanted. This seems rather marginal.
258
259 . Check names that consist entirely of digits: PCRE allows, but do Perl and
260 Python, etc?
261
262 Philip Hazel
263 Email local part: ph10
264 Email domain: cam.ac.uk
265 Last updated: 04 July 2008

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