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Contents of /code/trunk/maint/README

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Revision 455 - (show annotations)
Sat Sep 26 19:12:32 2009 UTC (11 years, 6 months ago) by ph10
File size: 13853 byte(s)
Added lower bound length-finding to pcre_study() and use it when matching; make 
the value available via pcre_fullinfo(); also fixed bugs connected with
pcre_study() in pcre_dfa_exec(). 
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 README This file.
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.
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).
51 ucptestdata A directory containing two files, testinput1 and testoutput1,
52 to use in conjunction with the ucptest program.
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.
63 Updating to a new Unicode release
64 ---------------------------------
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.
73 The ucptest program can be compiled and used to check that the new tables in
74 pcre_ucd.c work properly, using the data files in ucptestdata to check a number
75 of test characters.
78 Preparing for a PCRE release
79 ----------------------------
81 This section contains a checklist of things that I consult before building a
82 distribution for a new release.
84 . Ensure that the version number and version date are correct in configure.ac.
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, 4, 6, and 11. The first two can
95 be run with Perl 5.8 or 5.10; the last two require Perl 5.10. The output
96 should match the PCRE test output, apart from the version identification at
97 the start of each test. The other tests are not Perl-compatible (they use
98 various PCRE-specific features or options).
100 . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
101 valgrind", though that takes quite a long time.
103 . It may also useful to test with Electric Fence, though the fact that it
104 grumbles for missing free() calls can be a nuisance. (A missing free() in
105 pcretest is hardly a big problem.) To build with EF, use:
107 LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
109 Then all normal runs use it to check for buffer overflow. Also run everything
110 with:
112 EF_PROTECT_BELOW=1 <whatever>
114 because there have been problems with lookbehinds that looked too far.
116 . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
117 HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
118 used" warnings for the modules in which there is no call to memmove(). These
119 can be ignored.
121 . Documentation: check AUTHORS, COPYING, ChangeLog (check version and date),
122 INSTALL, LICENCE, NEWS (check version and date), NON-UNIX-USE, and README.
123 Many of these won't need changing, but over the long term things do change.
125 . Man pages: Check all man pages for \ not followed by e or f or " because
126 that indicates a markup error.
128 . When the release is built, test it on a number of different operating
129 systems if possible, and using different compilers as well. For example,
130 on Solaris it is helpful to test using Sun's cc compiler as a change from
131 gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
132 needs -S 64 for pcretest to increase the stack size for test 2.
135 Making a PCRE release
136 ---------------------
138 Run PrepareRelease and commit the files that it changes (by removing trailing
139 spaces). Then run "make distcheck" to create the tarballs and the zipball.
140 Double-check with "svn status", then create an SVN tagged copy:
142 svn copy svn://vcs.exim.org/pcre/code/trunk \
143 svn://vcs.exim.org/pcre/code/tags/pcre-8.xx
145 Don't forget to update Freshmeat when the new release is out, and to tell
146 webmaster@pcre.org and the mailing list.
149 Future ideas (wish list)
150 ------------------------
152 This section records a list of ideas so that they do not get forgotten. They
153 vary enormously in their usefulness and potential for implementation. Some are
154 very sensible; some are rather wacky. Some have been on this list for years;
155 others are relatively new.
157 . Optimization
159 There are always ideas for new optimizations so as to speed up pattern
160 matching. Most of them try to save work by recognizing a non-match without
161 having to scan all the possibilities. These are some that I've recorded:
163 * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
164 slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
165 OTOH, this is pathological - the user could easily fix it.
167 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
168 to have little effect, and maybe makes things worse.
170 * "Ends with literal string" - note that a single character doesn't gain much
171 over the existing "required byte" (reqbyte) feature that just remembers one
172 byte.
174 * These probably need to go in study():
176 o Remember an initial string rather than just 1 char?
178 o A required byte from alternatives - not just the last char, but an
179 earlier one if common to all alternatives.
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 it 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 affects quite a few places in the code and is not trivial.
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 > 8.
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. Thiw
272 was promised a long time ago, and never appeared...
274 . Write a function that generates random matching strings for a compiled regex.
276 . Write a wrapper to maintain a structure with specified runtime parameters,
277 such as recurse limit, and pass these to PCRE each time it is called. Also
278 maybe malloc and free. A user sent a prototype.
280 . Pcregrep: an option to specify the output line separator, either as a string
281 or select from a fixed list. This is not dead easy, because at the moment it
282 outputs whatever is in the input file.
284 . Improve the code for duplicate checking in pcre_dfa_exec(). An incomplete,
285 non-thread-safe patch showed that this can help performance for patterns
286 where there are many alternatives. However, a simple thread-safe
287 implementation that I tried made things worse in many simple cases, so this
288 is not an obviously good thing.
290 . Make the longest lookbehind available via pcre_fullinfo(). This is not
291 straightforward because lookbehinds can be nested inside lookbehinds. This
292 case will have to be identified, and the amounts added. This should then give
293 the maximum possible lookbehind length. The reason for wanting this is to
294 help when implementing multi-segment matching using pcre_exec() with partial
295 matching and overlapping segments.
297 . PCRE cannot at present distinguish between subpatterns with different names,
298 but the same number (created by the use of ?|). In order to do so, a way of
299 remembering *which* subpattern numbered n matched is needed. Bugzilla #760.
301 Philip Hazel
302 Email local part: ph10
303 Email domain: cam.ac.uk
304 Last updated: 26 September 2009

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