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Mon Jun 18 18:22:51 2012 UTC (8 years, 10 months ago) by ph10
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Rework and rename some of the docs about building methods.
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 pcre_chartables.c.non-standard
40 This is a set of character tables that came from a Windows
41 system. It has characters greater than 128 that are set as
42 spaces, amongst other things. I kept it so that it can be
43 used for testing from time to time.
45 README This file.
47 Unicode.tables The files in this directory, DerivedGeneralCategory.txt,
48 Scripts.txt and UnicodeData.txt, were downloaded from the
49 Unicode web site. They contain information about Unicode
50 characters and scripts.
52 ucptest.c A short C program for testing the Unicode property macros
53 that do lookups in the pcre_ucd.c data, mainly useful after
54 rebuilding the Unicode property table. Compile and run this in
55 the "maint" directory (see comments at its head).
57 ucptestdata A directory containing two files, testinput1 and testoutput1,
58 to use in conjunction with the ucptest program.
60 utf8.c A short, freestanding C program for converting a Unicode code
61 point into a sequence of bytes in the UTF-8 encoding, and vice
62 versa. If its argument is a hex number such as 0x1234, it
63 outputs a list of the equivalent UTF-8 bytes. If its argument
64 is sequence of concatenated UTF-8 bytes (e.g. e188b4) it
65 treats them as a UTF-8 character and outputs the equivalent
66 code point in hex.
69 Updating to a new Unicode release
70 =================================
72 When there is a new release of Unicode, the files in Unicode.tables must be
73 refreshed from the web site. If the new version of Unicode adds new character
74 scripts, the source file ucp.h and both the MultiStage2.py and the
75 GenerateUtt.py scripts must be edited to add the new names. Then MultiStage2.py
76 can be run to generate a new version of pcre_ucd.c, and GenerateUtt.py can be
77 run to generate the tricky tables for inclusion in pcre_tables.c.
79 If MultiStage2.py gives the error "ValueError: list.index(x): x not in list",
80 the cause is usually a missing (or misspelt) name in the list of scripts. I
81 couldn't find a straightforward list of scripts on the Unicode site, but
82 there's a useful Wikipedia page that list them, and notes the Unicode version
83 in which they were introduced:
85 http://en.wikipedia.org/wiki/Unicode_scripts#Table_of_Unicode_scripts
87 The ucptest program can be compiled and used to check that the new tables in
88 pcre_ucd.c work properly, using the data files in ucptestdata to check a number
89 of test characters. The source file ucptest.c must be updated whenever new
90 Unicode script names are added.
92 Note also that both the pcresyntax.3 and pcrepattern.3 man pages contain lists
93 of Unicode script names.
96 Preparing for a PCRE release
97 ============================
99 This section contains a checklist of things that I consult before building a
100 distribution for a new release.
102 . Ensure that the version number and version date are correct in configure.ac.
104 . Update the library version numbers in configure.ac according to the rules
105 given below.
107 . If new build options have been added, ensure that they are added to the CMake
108 files as well as to the autoconf files. The relevant files are CMakeLists.txt
109 and config-cmake.h.in. After making a release tarball, test it out with CMake
110 if there have been changes here.
112 . Run ./autogen.sh to ensure everything is up-to-date.
114 . Compile and test with many different config options, and combinations of
115 options. Also, test with valgrind by running "RunTest valgrind" and
116 "RunGrepTest valgrind" (which takes quite a long time). The script
117 maint/ManyConfigTests now encapsulates this testing. It runs tests with
118 different configurations, and it also runs some of them with valgrind, all of
119 which can take quite some time.
121 . Run perltest.pl on the test data for tests 1, 4, and 6. The output
122 should match the PCRE test output, apart from the version identification at
123 the start of each test. The other tests are not Perl-compatible (they use
124 various PCRE-specific features or options).
126 . It is possible to test with the emulated memmove() function by undefining
127 HAVE_MEMMOVE and HAVE_BCOPY in config.h, though I do not do this often. You
128 may see a number of "pcre_memmove defined but not used" warnings for the
129 modules in which there is no call to memmove(). These can be ignored.
131 . Documentation: check AUTHORS, COPYING, ChangeLog (check version and date),
132 INSTALL, LICENCE, NEWS (check version and date), NON-AUTOTOOLS-BUILD, and
133 README. Many of these won't need changing, but over the long term things do
134 change.
136 . I used to test new releases myself on a number of different operating
137 systems, using different compilers as well. For example, on Solaris it is
138 helpful to test using Sun's cc compiler as a change from gcc. Adding
139 -xarch=v9 to the cc options does a 64-bit test, but it also needs -S 64 for
140 pcretest to increase the stack size for test 2. Since I retired I can no
141 longer do this, but instead I rely on putting out release candidates for
142 folks on the pcre-dev list to test.
145 Updating version info for libtool
146 =================================
148 This set of rules for updating library version information came from a web page
149 whose URL I have forgotten. The version information consists of three parts:
150 (current, revision, age).
152 1. Start with version information of 0:0:0 for each libtool library.
154 2. Update the version information only immediately before a public release of
155 your software. More frequent updates are unnecessary, and only guarantee
156 that the current interface number gets larger faster.
158 3. If the library source code has changed at all since the last update, then
159 increment revision; c:r:a becomes c:r+1:a.
161 4. If any interfaces have been added, removed, or changed since the last
162 update, increment current, and set revision to 0.
164 5. If any interfaces have been added since the last public release, then
165 increment age.
167 6. If any interfaces have been removed or changed since the last public
168 release, then set age to 0.
170 The following explanation may help in understanding the above rules a bit
171 better. Consider that there are three possible kinds of reaction from users to
172 changes in a shared library:
174 1. Programs using the previous version may use the new version as a drop-in
175 replacement, and programs using the new version can also work with the
176 previous one. In other words, no recompiling nor relinking is needed. In
177 this case, increment revision only, don't touch current or age.
179 2. Programs using the previous version may use the new version as a drop-in
180 replacement, but programs using the new version may use APIs not present in
181 the previous one. In other words, a program linking against the new version
182 may fail if linked against the old version at run time. In this case, set
183 revision to 0, increment current and age.
185 3. Programs may need to be changed, recompiled, relinked in order to use the
186 new version. Increment current, set revision and age to 0.
189 Making a PCRE release
190 =====================
192 Run PrepareRelease and commit the files that it changes (by removing trailing
193 spaces). The first thing this script does is to run CheckMan on the man pages;
194 if it finds any markup errors, it reports them and then aborts.
196 Once PrepareRelease has run clean, run "make distcheck" to create the tarballs
197 and the zipball. Double-check with "svn status", then create an SVN tagged
198 copy:
200 svn copy svn://vcs.exim.org/pcre/code/trunk \
201 svn://vcs.exim.org/pcre/code/tags/pcre-8.xx
203 Don't forget to update Freshmeat when the new release is out, and to tell
204 webmaster@pcre.org and the mailing list. Also, update the list of version
205 numbers in Bugzilla (edit products).
208 Future ideas (wish list)
209 ========================
211 This section records a list of ideas so that they do not get forgotten. They
212 vary enormously in their usefulness and potential for implementation. Some are
213 very sensible; some are rather wacky. Some have been on this list for years;
214 others are relatively new.
216 . Optimization
218 There are always ideas for new optimizations so as to speed up pattern
219 matching. Most of them try to save work by recognizing a non-match without
220 having to scan all the possibilities. These are some that I've recorded:
222 * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
223 slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
224 OTOH, this is pathological - the user could easily fix it.
226 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
227 to have little effect, and maybe makes things worse.
229 * "Ends with literal string" - note that a single character doesn't gain much
230 over the existing "required byte" (reqbyte) feature that just remembers one
231 data unit.
233 * These probably need to go in pcre_study():
235 o Remember an initial string rather than just 1 char?
237 o A required data unit from alternatives - not just the last unit, but an
238 earlier one if common to all alternatives.
240 o Friedl contains other ideas.
242 * pcre_study() does not set initial byte flags for Unicode property types
243 such as \p; I don't know how much benefit there would be for, for example,
244 setting the bits for 0-9 and all bytes >= xC0 when a pattern starts with
245 \p{N}.
247 * There is scope for more "auto-possessifying" in connection with \p and \P.
249 . If Perl gets to a consistent state over the settings of capturing sub-
250 patterns inside repeats, see if we can match it. One example of the
251 difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
252 leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
253 because I think it needs much more state to be remembered.
255 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
257 . Allow errorptr and erroroffset to be NULL. I don't like this idea.
259 . Line endings:
261 * Option to use NUL as a line terminator in subject strings. This could now
262 be done relatively easily since the extension to support LF, CR, and CRLF.
263 If it is done, a suitable option for pcregrep is also required.
265 . Option to provide the pattern with a length instead of with a NUL terminator.
266 This affects quite a few places in the code and is not trivial.
268 . Catch SIGSEGV for stack overflows?
270 . A feature to suspend a match via a callout was once requested.
272 . Option to convert results into character offsets and character lengths.
274 . Option for pcregrep to scan only the start of a file. I am not keen - this is
275 the job of "head".
277 . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
278 preceded by a blank line, instead of adding it to every matched line, and (b)
279 support --outputfile=name.
281 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 8.
282 (And now presumably UTF-16 and UCP for the 16-bit library.)
284 . Add a user pointer to pcre_malloc/free functions -- some option would be
285 needed to retain backward compatibility.
287 . Define a union for the results from pcre_fullinfo().
289 . Provide a "random access to the subject" facility so that the way in which it
290 is stored is independent of PCRE. For efficiency, it probably isn't possible
291 to switch this dynamically. It would have to be specified when PCRE was
292 compiled. PCRE would then call a function every time it wanted a character.
294 . Wild thought: the ability to compile from PCRE's internal byte code to a real
295 FSM and a very fast (third) matcher to process the result. There would be
296 even more restrictions than for pcre_dfa_exec(), however. This is not easy.
297 This is probably obsolete now that we have the JIT support.
299 . Should pcretest have some private locale data, to avoid relying on the
300 available locales for the test data, since different OS have different ideas?
301 This won't be as thorough a test, but perhaps that doesn't really matter.
303 . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
304 them will of course slow it down.
306 . Someone suggested --disable-callout to save code space when callouts are
307 never wanted. This seems rather marginal.
309 . Check names that consist entirely of digits: PCRE allows, but do Perl and
310 Python, etc?
312 . A user suggested a parameter to limit the length of string matched, for
313 example if the parameter is N, the current match should fail if the matched
314 substring exceeds N. This could apply to both match functions. The value
315 could be a new field in the extra block.
317 . Callouts with arguments: (?Cn:ARG) for instance.
319 . A user is going to supply a patch to generalize the API for user-specific
320 memory allocation so that it is more flexible in threaded environments. This
321 was promised a long time ago, and never appeared. However, this is a live
322 issue not only for threaded environments, but for libraries that use PCRE and
323 want not to be beholden to their caller's memory allocation.
325 . Write a wrapper to maintain a structure with specified runtime parameters,
326 such as recurse limit, and pass these to PCRE each time it is called. Also
327 maybe malloc and free. A user sent a prototype. This relates the the previous
328 item.
330 . Write a function that generates random matching strings for a compiled regex.
332 . Pcregrep: an option to specify the output line separator, either as a string
333 or select from a fixed list. This is not dead easy, because at the moment it
334 outputs whatever is in the input file.
336 . Improve the code for duplicate checking in pcre_dfa_exec(). An incomplete,
337 non-thread-safe patch showed that this can help performance for patterns
338 where there are many alternatives. However, a simple thread-safe
339 implementation that I tried made things worse in many simple cases, so this
340 is not an obviously good thing.
342 . Make the longest lookbehind available via pcre_fullinfo(). This is not
343 straightforward because lookbehinds can be nested inside lookbehinds. This
344 case will have to be identified, and the amounts added. This should then give
345 the maximum possible lookbehind length. The reason for wanting this is to
346 help when implementing multi-segment matching using pcre_exec() with partial
347 matching and overlapping segments.
349 . PCRE cannot at present distinguish between subpatterns with different names,
350 but the same number (created by the use of ?|). In order to do so, a way of
351 remembering *which* subpattern numbered n matched is needed. Bugzilla #760.
352 Now that (*MARK) has been implemented, it can perhaps be used as a way round
353 this problem.
355 . Instead of having #ifdef HAVE_CONFIG_H in each module, put #include
356 "something" and the the #ifdef appears only in one place, in "something".
358 Philip Hazel
359 Email local part: ph10
360 Email domain: cam.ac.uk
361 Last updated: 18 June 2012

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