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Contents of /code/trunk/maint/README

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Tue Aug 26 11:49:38 2008 UTC (12 years, 7 months ago) by ph10
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Update maint/README with new wishlist items.
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 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 ManyConfigTests A shell script that runs "configure, make, test" a number of
31 times with different configuration settings.
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.
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.
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).
49 ucptestdata A directory containing two files, testinput1 and testoutput1,
50 to use in conjunction with the ucptest program.
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.
61 Updating to a new Unicode release
62 ---------------------------------
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, 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.
72 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.
77 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 . Ensure that the version number and version date are correct in configure.ac,
84 ChangeLog, and NEWS.
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.
89 . Run ./autogen.sh to ensure everything is up-to-date.
91 . Compile and test with many different config options, and combinations of
92 options. The maint/ManyConfigTests script now encapsulates this testing.
94 . Run perltest.pl on the test data for tests 1 and 4. The output should match
95 the PCRE test output, apart from the version identification at the top. The
96 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.
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 pcretest is hardly a big problem.) To build with EF, use:
105 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:
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 used" warnings for the modules in which there is no call to memmove(). These
117 can be ignored.
119 . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,
120 LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't
121 need changing, but over the long term things do change.
123 . Man pages: Check all man pages for \ not followed by e or f or " because
124 that indicates a markup error.
126 . When the release is built, test it on a number of different operating
127 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.
133 Making a PCRE release
134 ---------------------
136 Run PrepareRelease and commit the files that it changes (by removing trailing
137 spaces). Then run "make distcheck" to create the tarballs and the zipball.
138 Double-check with "svn status", then create an SVN tagged copy:
140 svn copy svn://vcs.exim.org/pcre/code/trunk \
141 svn://vcs.exim.org/pcre/code/tags/pcre-7.x
143 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 vary enormously in their usefulness and potential for implementation. Some are
152 very sensible; some are rather wacky. Some have been on this list for years;
153 others are relatively new.
155 . Optimization
157 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 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 OTOH, this is pathological - the user could easily fix it.
165 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
166 to have little effect, and maybe makes things worse.
168 * "Ends with literal string" - note that a single character doesn't gain much
169 over the existing "required byte" (reqbyte) feature that just saves one
170 byte.
172 * These probably need to go in study():
174 o Remember an initial string rather than just 1 char?
176 o A required byte from alternatives - not just the last char, but an
177 earlier one if common to all alternatives.
179 o Minimum length of subject needed.
181 o Friedl contains other ideas.
183 . 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 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
191 . Unicode
193 * 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 implement.
198 * 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?
205 * 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.
210 . 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 If this is done, a suitable option for pcregrep is also required.
218 . Option to provide the pattern with a length instead of with a NUL terminator.
219 This probably affects quite a few places in the code.
221 . Catch SIGSEGV for stack overflows?
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 . Option for pcregrep to scan only the start of a file. I am not keen - this is
228 the job of "head".
230 . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
231 preceded by a blank line, instead of adding it to every matched line, and (b)
232 support --outputfile=name.
234 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
236 . Add a user pointer to pcre_malloc/free functions -- some option would be
237 needed to retain backward compatibility.
239 . Define a union for the results from pcre_fullinfo().
241 . 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 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.
246 . 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.
250 . 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.
254 . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
255 them will of course slow it down.
257 . Someone suggested --disable-callout to save code space when callouts are
258 never wanted. This seems rather marginal.
260 . Check names that consist entirely of digits: PCRE allows, but do Perl and
261 Python, etc?
263 . A user suggested a parameter to limit the length of string matched, for
264 example if the parameter is N, the current match should fail if the matched
265 substring exceeds N. This could apply to both match functions. The value
266 could be a new field in the extra block.
268 . Callouts with arguments: (?Cn:ARG) for instance.
270 . A user is going to supply a patch to generalize the API for user-specific
271 memory allocation so that it is more flexible in threaded environments.
273 Philip Hazel
274 Email local part: ph10
275 Email domain: cam.ac.uk
276 Last updated: 26 August 2008

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