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Contents of /code/trunk/maint/README

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Revision 129 - (show annotations)
Tue Mar 20 16:33:54 2007 UTC (14 years, 6 months ago) by ph10
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The maint/ManyConfigTests script runs a whole slew of tests.
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 Builducptable A Perl script that creates the contents of the ucptable.h file
20 from two Unicode data files, which themselves are downloaded
21 from the Unicode web site. Run this script in the "maint"
22 directory.
24 ManyConfigTests A shell script that runs "configure, make, test" a number of
25 times with different configuration settings.
27 Unicode.tables The files in this directory, Scripts.txt and UnicodeData.txt,
28 were downloaded from the Unicode web site. They contain
29 information about Unicode characters and scripts.
31 ucptest.c A short C program for testing the Unicode property functions
32 in pcre_ucp_searchfuncs.c, mainly useful after rebuilding the
33 Unicode property table. Compile and run this in the "maint"
34 directory.
36 ucptestdata A directory containing two files, testinput1 and testoutput1,
37 to use in conjunction with the ucptest program.
39 utf8.c A short, freestanding C program for converting a Unicode code
40 point into a sequence of bytes in the UTF-8 encoding, and vice
41 versa. If its argument is a hex number such as 0x1234, it
42 outputs a list of the equivalent UTF-8 bytes. If its argument
43 is sequence of concatenated UTF-8 bytes (e.g. e188b4) it
44 treats them as a UTF-8 character and outputs the equivalent
45 code point in hex.
48 Updating to a new Unicode release
49 ---------------------------------
51 When there is a new release of Unicode, the files in Unicode.tables must be
52 refreshed from the web site, and the Buildupctable script can then be run to
53 generate a new version of ucptable.h. The ucptest program can be used to check
54 that the resulting table works properly, using the data files in ucptestdata to
55 check a number of test characters.
58 Preparing for a PCRE release
59 ----------------------------
61 This section contains a checklist of things that I consult before building a
62 distribution for a new release.
64 . Ensure that the version number and version date are correct in configure.ac.
66 . Run ./autogen.sh to ensure everything is up-to-date.
68 . Compile and test with many different config options, and combinations of
69 options. The maint/ManyConfigTests script now encapsulates this testing.
71 . Run perltest.pl on the test data for tests 1 and 4. The output should match
72 the PCRE test output, apart from the version identification at the top. The
73 other tests are not Perl-compatible (they use various special PCRE options).
75 . Test on a number of different operating systems. In particular, at the moment
76 I can test on Solaris, using Sun's cc compiler (as a change from gcc). Adding
77 -xarch=v9 to the cc options does a 64-bit test, but it also needs -S 64 for
78 pcretest to increase the stack size for test 2. I also test on FreeBSD and
79 Linux (where I develop).
81 . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
82 valgrind", though that takes quite a long time.
84 . It can also useful to test with Electric Fence, though the fact that it
85 grumbles for missing free() calls can be a nuisance. (A missing free() in
86 pcretest is hardly a big problem.) To build with EF, use:
88 LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
90 Then all normal runs use it to check for buffer overflow. Also run everything
91 with:
93 EF_PROTECT_BELOW=1 <whatever>
95 because there have been problems with lookbehinds that looked too far.
97 . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
98 HAVE_BCOPY in config.h.
100 . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,
101 LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't
102 need changing, but over the long term things do change.
104 . Man pages: Check all man pages for \ not followed by e or f or " because
105 that indicates a markup error.
108 Making a PCRE release
109 ---------------------
111 Run PrepareRelease and commit the files that it changes (by removing trailing
112 spaces). Then run "make dist" to create the tarballs and the zipball.
114 Don't forget to update Freshmeat when the new release is out, and to tell
115 webmaster@pcre.org and the mailing list.
118 Future ideas (wish list)
119 ------------------------
121 This section records a list of ideas so that they do not get forgotten. They
122 vary enormously in their usefulness and potential for implementation. Some are
123 very sensible; some are rather wacky. Some have been on this list for years;
124 others are relatively new.
126 . Optimization
128 There are always ideas for new optimizations so as to speed up pattern
129 matching. Most of them try to save work by recognizing a non-match without
130 having to scan all the possibilities. These are some that I've recorded:
132 * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
133 slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
134 OTOH, this is pathological - the user could easily fix it.
136 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
137 to have little effect, and maybe makes things worse.
139 * "Ends with literal string" - note that a single character doesn't gain much
140 over the existing "required byte" (reqbyte) feature that just saves one
141 byte.
143 * These probably need to go in study():
145 o Remember an initial string rather than just 1 char?
147 o A required byte from alternatives - not just the last char, but an
148 earlier one if common to all alternatives.
150 o Minimum length of subject needed.
152 o Friedl contains other ideas.
154 . If Perl gets to a consistent state over the settings of capturing sub-
155 patterns inside repeats, see if we can match it. One example of the
156 difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
157 leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
158 because I think it needs much more state to be remembered.
160 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
162 . Unicode
164 * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX
165 character classes. For the moment, I've chosen not to support this for
166 backward compatibility, for speed, and because it would be messy to
167 implement.
169 * A different approach to Unicode might be to use a typedef to do everything
170 in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
171 new typedef to distinguish data from bits of compiled pattern that are in
172 bytes, I think. There would need to be conversion functions in and out. I
173 don't think this is particularly trivial - and anyway, Unicode now has
174 characters that need more than 16 bits, so is this at all sensible?
176 * There has been a request for direct support of 16-bit characters and
177 UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
178 is this worth it at all? One possible way of handling 16-bit characters
179 would be to "load" them in the same way that UTF-8 characters are loaded.
181 . Allow errorptr and erroroffset to be NULL. I don't like this idea.
183 . Line endings:
185 * Option to use NUL as a line terminator in subject strings. This could now
186 be done relatively easily since the extension to support LF, CR, and CRLF.
187 If this is done, a suitable option for pcregrep is also required.
189 . Option to provide the pattern with a length instead of with a NUL terminator.
190 This probably affects quite a few places in the code.
192 . Catch SIGSEGV for stack overflows?
194 . "Cut" as described in Jeffrey Friedl's book, p364: \v and \V. The definitions
195 aren't yet clear enough for me. \v flushes saved states so that no
196 backtracking to anything earlier can happen; \V says "no more bumpalong", but
197 does it fail the current match? As described in the book, these aren't really
198 "cut" as in Prolog, are they? NOTE: (a) PCRE once had "cut", but it was
199 removed when atomic groups were introduced. (b) Perl 5.10 has some (*PRUNE)
200 features -- see below.
202 . A feature to suspend a match via a callout was once requested.
204 . Option to convert results into character offsets and character lengths.
206 . Option for pcregrep to scan only the start of a file. I am not keen - this is
207 the job of "head".
209 . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
210 preceded by a blank line, instead of adding it to every matched line, and (b)
211 support --outputfile=name.
213 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
215 . Add a user pointer to pcre_malloc/free functions -- some option would be
216 needed to retain backward compatibility.
218 . Define a union for the results from pcre_fullinfo().
220 . Provide a "random access to the subject" facility so that the way in which it
221 is stored is independent of PCRE. For efficiency, it probably isn't possible
222 to switch this dynamically. It would have to be specified when PCRE was
223 compiled. PCRE would then call a function every time it wanted a character.
225 . There are new (*PRUNE) facilities in Perl 5.10, some of which it might be
226 relatively easy to implement.
228 . Also in Perl 5.10 are relative subroutine references (?&-1) and (?&+1) which
229 I didn't know about when I added some 5.10 features for PCRE 7.0. What about
230 (?(-1)... as a condition? That's an obvious extension, even if Perl 5.10
231 doesn't have it.
233 . Wild thought: the ability to compile from PCRE's internal byte code to a real
234 FSM and a very fast (third) matcher to process the result. There would be
235 even more restrictions than for pcre_dfa_exec(), however. This is not easy.
237 . Should pcretest have some private locale data, to avoid relying on the
238 available locales for the test data, since different OS have different ideas?
239 This won't be as thorough a test, but perhaps that doesn't really matter.
241 . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
242 them will of course slow it down.
244 . Re-arrange test 2: take out the link-size dependent stuff for a separate test
245 that is run only when the link size *is* 2; leave in some non-numbered
246 debugging tests using the new /Z feature.
248 . Stan Switzer's goto replacement for longjmp, which is apparently very slow on
249 OS-X. This is used when stack recursion is disabled. It would be worth doing
250 some timing tests on other OS.
252 . Someone suggested --disable-callout to save code space when callouts are
253 never wanted. This seems rather marginal.
255 Philip Hazel
256 Email local part: ph10
257 Email domain: cam.ac.uk
258 Last updated: 20 March 2007

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