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Contents of /code/trunk/maint/README

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Mon Jul 7 15:12:56 2008 UTC (6 years, 9 months ago) by ph10
File size: 11703 byte(s)
Final (?) tidies for new Unicode property code.

2     ---------------------------
4 ph10 181 The files in the "maint" directory of the PCRE source contain data, scripts,
5 ph10 122 and programs that are used for the maintenance of PCRE, but which do not form
6 ph10 181 part of the PCRE distribution tarballs. This document describes these files and
7 ph10 122 also contains some notes for maintainers. Its contents are:
8 ph10 97
9 ph10 122 Files in the maint directory
10     Updating to a new Unicode release
11     Preparing for a PCRE release
12     Making a PCRE release
13 ph10 181 Long-term ideas (wish list)
14 ph10 122
16     Files in the maint directory
17     ----------------------------
19 ph10 350 ----------------- This file is now OBSOLETE and no longer used ----------------
20 ph10 129 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 ph10 350 ----------------- This file is now OBSOLETE and no longer used ----------------
25 ph10 181
26 ph10 351 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.
30 ph10 129 ManyConfigTests A shell script that runs "configure, make, test" a number of
31     times with different configuration settings.
32 ph10 350
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 ph10 181
39 ph10 350 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 ph10 181
44 ph10 350 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 ph10 351 the "maint" directory (see comments at its head).
48 ph10 181
49 ph10 129 ucptestdata A directory containing two files, testinput1 and testoutput1,
50     to use in conjunction with the ucptest program.
51 ph10 181
52 ph10 129 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 ph10 97
60 ph10 181
61 ph10 122 Updating to a new Unicode release
62     ---------------------------------
64 ph10 181 When there is a new release of Unicode, the files in Unicode.tables must be
65 ph10 351 refreshed from the web site. If the new version of Unicode adds new character
66 ph10 352 scripts, the source file ucp.h and both the MultiStage2.py and the
67     GenerateUtt.py scripts must be edited to add the new names. Then the
68     MultiStage2.py script can then be run to generate a new version of pcre_ucd.c
69     and the GenerateUtt.py can be run to generate the tricky tables for inclusion
70     in pcre_tables.c.
71 ph10 122
72 ph10 351 The ucptest program can then be compiled and used to check that the new tables
73     in pcre_ucd.c work properly, using the data files in ucptestdata to check a
74     number of test characters.
75 ph10 122
76 ph10 351
77 ph10 122 Preparing for a PCRE release
78     ----------------------------
80     This section contains a checklist of things that I consult before building a
81     distribution for a new release.
83 ph10 155 . Ensure that the version number and version date are correct in configure.ac,
84     ChangeLog, and NEWS.
85 ph10 292
86     . If new build options have been added, ensure that they are added to the CMake
87     files as well as to the autoconf files.
88 ph10 122
89     . Run ./autogen.sh to ensure everything is up-to-date.
91 ph10 181 . Compile and test with many different config options, and combinations of
92 ph10 129 options. The maint/ManyConfigTests script now encapsulates this testing.
93 ph10 181
94 ph10 122 . Run perltest.pl on the test data for tests 1 and 4. The output should match
95 ph10 181 the PCRE test output, apart from the version identification at the top. The
96 ph10 122 other tests are not Perl-compatible (they use various special PCRE options).
98     . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
99     valgrind", though that takes quite a long time.
100 ph10 181
101     . It may also useful to test with Electric Fence, though the fact that it
102     grumbles for missing free() calls can be a nuisance. (A missing free() in
103 ph10 122 pcretest is hardly a big problem.) To build with EF, use:
104 ph10 181
105 ph10 122 LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
107     Then all normal runs use it to check for buffer overflow. Also run everything
108     with:
109 ph10 181
110     EF_PROTECT_BELOW=1 <whatever>
112     because there have been problems with lookbehinds that looked too far.
114     . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
115     HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
116 ph10 155 used" warnings for the modules in which there is no call to memmove(). These
117     can be ignored.
118 ph10 122
119 ph10 181 . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,
120     LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't
121 ph10 122 need changing, but over the long term things do change.
122 ph10 181
123 ph10 122 . Man pages: Check all man pages for \ not followed by e or f or " because
124     that indicates a markup error.
126 ph10 181 . When the release is built, test it on a number of different operating
127 ph10 155 systems if possible, and using different compilers as well. For example,
128     on Solaris it is helpful to test using Sun's cc compiler as a change from
129     gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
130     needs -S 64 for pcretest to increase the stack size for test 2.
131 ph10 122
132 ph10 155
133 ph10 122 Making a PCRE release
134     ---------------------
136     Run PrepareRelease and commit the files that it changes (by removing trailing
137 ph10 155 spaces). Then run "make distcheck" to create the tarballs and the zipball.
138 ph10 212 Double-check with "svn status", then create an SVN tagged copy:
139 ph10 122
140 ph10 212 svn copy svn://vcs.exim.org/pcre/code/trunk \
141     svn://vcs.exim.org/pcre/code/tags/pcre-7.x
143 ph10 122 Don't forget to update Freshmeat when the new release is out, and to tell
144     webmaster@pcre.org and the mailing list.
147     Future ideas (wish list)
148     ------------------------
150     This section records a list of ideas so that they do not get forgotten. They
151 ph10 181 vary enormously in their usefulness and potential for implementation. Some are
152 ph10 122 very sensible; some are rather wacky. Some have been on this list for years;
153     others are relatively new.
155     . Optimization
157 ph10 181 There are always ideas for new optimizations so as to speed up pattern
158     matching. Most of them try to save work by recognizing a non-match without
159 ph10 122 having to scan all the possibilities. These are some that I've recorded:
161     * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
162     slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
163 ph10 181 OTOH, this is pathological - the user could easily fix it.
165 ph10 122 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
166     to have little effect, and maybe makes things worse.
167 ph10 181
168     * "Ends with literal string" - note that a single character doesn't gain much
169 ph10 122 over the existing "required byte" (reqbyte) feature that just saves one
170     byte.
171 ph10 181
172 ph10 122 * These probably need to go in study():
173 ph10 181
174 ph10 122 o Remember an initial string rather than just 1 char?
175 ph10 181
176 ph10 122 o A required byte from alternatives - not just the last char, but an
177     earlier one if common to all alternatives.
178 ph10 181
179 ph10 122 o Minimum length of subject needed.
180 ph10 181
181 ph10 122 o Friedl contains other ideas.
182 ph10 181
183 ph10 122 . If Perl gets to a consistent state over the settings of capturing sub-
184     patterns inside repeats, see if we can match it. One example of the
185     difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
186     leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
187     because I think it needs much more state to be remembered.
189 ph10 181 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
191 ph10 122 . Unicode
193 ph10 181 * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX
194     character classes. For the moment, I've chosen not to support this for
195     backward compatibility, for speed, and because it would be messy to
196 ph10 122 implement.
197 ph10 181
198 ph10 122 * A different approach to Unicode might be to use a typedef to do everything
199     in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
200     new typedef to distinguish data from bits of compiled pattern that are in
201     bytes, I think. There would need to be conversion functions in and out. I
202     don't think this is particularly trivial - and anyway, Unicode now has
203     characters that need more than 16 bits, so is this at all sensible?
204 ph10 181
205 ph10 122 * There has been a request for direct support of 16-bit characters and
206     UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
207     is this worth it at all? One possible way of handling 16-bit characters
208     would be to "load" them in the same way that UTF-8 characters are loaded.
209 ph10 181
210 ph10 122 . Allow errorptr and erroroffset to be NULL. I don't like this idea.
212     . Line endings:
214     * Option to use NUL as a line terminator in subject strings. This could now
215     be done relatively easily since the extension to support LF, CR, and CRLF.
216 ph10 181 If this is done, a suitable option for pcregrep is also required.
218 ph10 122 . Option to provide the pattern with a length instead of with a NUL terminator.
219 ph10 181 This probably affects quite a few places in the code.
220 ph10 122
221 ph10 181 . Catch SIGSEGV for stack overflows?
222 ph10 122
223     . A feature to suspend a match via a callout was once requested.
225     . Option to convert results into character offsets and character lengths.
227 ph10 181 . Option for pcregrep to scan only the start of a file. I am not keen - this is
228 ph10 122 the job of "head".
229 ph10 181
230     . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
231 ph10 122 preceded by a blank line, instead of adding it to every matched line, and (b)
232     support --outputfile=name.
233 ph10 181
234 ph10 122 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
236 ph10 181 . Add a user pointer to pcre_malloc/free functions -- some option would be
237 ph10 122 needed to retain backward compatibility.
238 ph10 181
239 ph10 122 . Define a union for the results from pcre_fullinfo().
241 ph10 181 . Provide a "random access to the subject" facility so that the way in which it
242     is stored is independent of PCRE. For efficiency, it probably isn't possible
243 ph10 122 to switch this dynamically. It would have to be specified when PCRE was
244     compiled. PCRE would then call a function every time it wanted a character.
245 ph10 181
246 ph10 122 . Wild thought: the ability to compile from PCRE's internal byte code to a real
247     FSM and a very fast (third) matcher to process the result. There would be
248     even more restrictions than for pcre_dfa_exec(), however. This is not easy.
249 ph10 181
250 ph10 122 . Should pcretest have some private locale data, to avoid relying on the
251     available locales for the test data, since different OS have different ideas?
252     This won't be as thorough a test, but perhaps that doesn't really matter.
253 ph10 181
254     . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
255 ph10 122 them will of course slow it down.
257 ph10 181 . Someone suggested --disable-callout to save code space when callouts are
258     never wanted. This seems rather marginal.
259 ph10 212
260     . Check names that consist entirely of digits: PCRE allows, but do Perl and
261     Python, etc?
262 ph10 122
263     Philip Hazel
264     Email local part: ph10
265     Email domain: cam.ac.uk
266 ph10 351 Last updated: 04 July 2008

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