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Contents of /code/trunk/maint/README

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Revision 455 - (hide annotations) (download)
Sat Sep 26 19:12:32 2009 UTC (5 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 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 454 README This file.
41 ph10 350 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.
45 ph10 181
46 ph10 350 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 ph10 351 the "maint" directory (see comments at its head).
50 ph10 181
51 ph10 129 ucptestdata A directory containing two files, testinput1 and testoutput1,
52     to use in conjunction with the ucptest program.
53 ph10 181
54 ph10 129 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.
61 ph10 97
62 ph10 181
63 ph10 122 Updating to a new Unicode release
64     ---------------------------------
66 ph10 181 When there is a new release of Unicode, the files in Unicode.tables must be
67 ph10 454 refreshed from the web site. If the new version of Unicode adds new character
68 ph10 352 scripts, the source file ucp.h and both the MultiStage2.py and the
69 ph10 454 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.
72 ph10 122
73 ph10 454 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.
76 ph10 122
77 ph10 351
78 ph10 122 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 ph10 454 . Ensure that the version number and version date are correct in configure.ac.
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 454 . 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).
99 ph10 122
100     . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
101     valgrind", though that takes quite a long time.
102 ph10 181
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 ph10 122 pcretest is hardly a big problem.) To build with EF, use:
106 ph10 181
107 ph10 122 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:
111 ph10 181
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 ph10 155 used" warnings for the modules in which there is no call to memmove(). These
119     can be ignored.
120 ph10 122
121 ph10 454 . 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.
124 ph10 181
125 ph10 122 . Man pages: Check all man pages for \ not followed by e or f or " because
126     that indicates a markup error.
128 ph10 181 . When the release is built, test it on a number of different operating
129 ph10 155 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.
133 ph10 122
134 ph10 155
135 ph10 122 Making a PCRE release
136     ---------------------
138     Run PrepareRelease and commit the files that it changes (by removing trailing
139 ph10 155 spaces). Then run "make distcheck" to create the tarballs and the zipball.
140 ph10 212 Double-check with "svn status", then create an SVN tagged copy:
141 ph10 122
142 ph10 212 svn copy svn://vcs.exim.org/pcre/code/trunk \
143 ph10 454 svn://vcs.exim.org/pcre/code/tags/pcre-8.xx
144 ph10 212
145 ph10 122 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 ph10 181 vary enormously in their usefulness and potential for implementation. Some are
154 ph10 122 very sensible; some are rather wacky. Some have been on this list for years;
155     others are relatively new.
157     . Optimization
159 ph10 181 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 ph10 122 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 ph10 181 OTOH, this is pathological - the user could easily fix it.
167 ph10 122 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
168     to have little effect, and maybe makes things worse.
169 ph10 181
170     * "Ends with literal string" - note that a single character doesn't gain much
171 ph10 454 over the existing "required byte" (reqbyte) feature that just remembers one
172 ph10 122 byte.
173 ph10 181
174 ph10 122 * These probably need to go in study():
175 ph10 181
176 ph10 122 o Remember an initial string rather than just 1 char?
177 ph10 181
178 ph10 122 o A required byte from alternatives - not just the last char, but an
179     earlier one if common to all alternatives.
180 ph10 181
181 ph10 122 o Friedl contains other ideas.
182 ph10 454
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 454 If it is done, a suitable option for pcregrep is also required.
217 ph10 181
218 ph10 122 . Option to provide the pattern with a length instead of with a NUL terminator.
219 ph10 454 This affects quite a few places in the code and is not trivial.
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 454 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 8.
235 ph10 122
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 372
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.
269 ph10 122
270 ph10 372 . A user is going to supply a patch to generalize the API for user-specific
271 ph10 454 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.
275 ph10 372
276 ph10 454 . 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 ph10 122 Philip Hazel
302     Email local part: ph10
303     Email domain: cam.ac.uk
304 ph10 455 Last updated: 26 September 2009

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