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1 ph10 122 MAINTENANCE README FOR PCRE
2     ---------------------------
3    
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
15    
16     Files in the maint directory
17     ----------------------------
18    
19 ph10 129 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.
23 ph10 181
24 ph10 129 ManyConfigTests A shell script that runs "configure, make, test" a number of
25     times with different configuration settings.
26 ph10 181
27     Unicode.tables The files in this directory, Scripts.txt and UnicodeData.txt,
28     were downloaded from the Unicode web site. They contain
29 ph10 129 information about Unicode characters and scripts.
30 ph10 181
31 ph10 129 ucptest.c A short C program for testing the Unicode property functions
32     in pcre_ucp_searchfuncs.c, mainly useful after rebuilding the
33 ph10 181 Unicode property table. Compile and run this in the "maint"
34 ph10 129 directory.
35 ph10 181
36 ph10 129 ucptestdata A directory containing two files, testinput1 and testoutput1,
37     to use in conjunction with the ucptest program.
38 ph10 181
39 ph10 129 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.
46 ph10 97
47 ph10 181
48 ph10 122 Updating to a new Unicode release
49     ---------------------------------
50    
51 ph10 181 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.
56 ph10 122
57    
58     Preparing for a PCRE release
59     ----------------------------
60    
61     This section contains a checklist of things that I consult before building a
62     distribution for a new release.
63    
64 ph10 155 . Ensure that the version number and version date are correct in configure.ac,
65     ChangeLog, and NEWS.
66 ph10 292
67     . If new build options have been added, ensure that they are added to the CMake
68     files as well as to the autoconf files.
69 ph10 122
70     . Run ./autogen.sh to ensure everything is up-to-date.
71    
72 ph10 181 . Compile and test with many different config options, and combinations of
73 ph10 129 options. The maint/ManyConfigTests script now encapsulates this testing.
74 ph10 181
75 ph10 122 . Run perltest.pl on the test data for tests 1 and 4. The output should match
76 ph10 181 the PCRE test output, apart from the version identification at the top. The
77 ph10 122 other tests are not Perl-compatible (they use various special PCRE options).
78    
79     . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
80     valgrind", though that takes quite a long time.
81 ph10 181
82     . It may also useful to test with Electric Fence, though the fact that it
83     grumbles for missing free() calls can be a nuisance. (A missing free() in
84 ph10 122 pcretest is hardly a big problem.) To build with EF, use:
85 ph10 181
86 ph10 122 LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
87    
88     Then all normal runs use it to check for buffer overflow. Also run everything
89     with:
90 ph10 181
91     EF_PROTECT_BELOW=1 <whatever>
92    
93     because there have been problems with lookbehinds that looked too far.
94    
95     . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
96     HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
97 ph10 155 used" warnings for the modules in which there is no call to memmove(). These
98     can be ignored.
99 ph10 122
100 ph10 181 . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,
101     LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't
102 ph10 122 need changing, but over the long term things do change.
103 ph10 181
104 ph10 122 . Man pages: Check all man pages for \ not followed by e or f or " because
105     that indicates a markup error.
106    
107 ph10 181 . When the release is built, test it on a number of different operating
108 ph10 155 systems if possible, and using different compilers as well. For example,
109     on Solaris it is helpful to test using Sun's cc compiler as a change from
110     gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
111     needs -S 64 for pcretest to increase the stack size for test 2.
112 ph10 122
113 ph10 155
114 ph10 122 Making a PCRE release
115     ---------------------
116    
117     Run PrepareRelease and commit the files that it changes (by removing trailing
118 ph10 155 spaces). Then run "make distcheck" to create the tarballs and the zipball.
119 ph10 212 Double-check with "svn status", then create an SVN tagged copy:
120 ph10 122
121 ph10 212 svn copy svn://vcs.exim.org/pcre/code/trunk \
122     svn://vcs.exim.org/pcre/code/tags/pcre-7.x
123    
124 ph10 122 Don't forget to update Freshmeat when the new release is out, and to tell
125     webmaster@pcre.org and the mailing list.
126    
127    
128     Future ideas (wish list)
129     ------------------------
130    
131     This section records a list of ideas so that they do not get forgotten. They
132 ph10 181 vary enormously in their usefulness and potential for implementation. Some are
133 ph10 122 very sensible; some are rather wacky. Some have been on this list for years;
134     others are relatively new.
135    
136     . Optimization
137    
138 ph10 181 There are always ideas for new optimizations so as to speed up pattern
139     matching. Most of them try to save work by recognizing a non-match without
140 ph10 122 having to scan all the possibilities. These are some that I've recorded:
141    
142     * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
143     slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
144 ph10 181 OTOH, this is pathological - the user could easily fix it.
145    
146 ph10 122 * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
147     to have little effect, and maybe makes things worse.
148 ph10 181
149     * "Ends with literal string" - note that a single character doesn't gain much
150 ph10 122 over the existing "required byte" (reqbyte) feature that just saves one
151     byte.
152 ph10 181
153 ph10 122 * These probably need to go in study():
154 ph10 181
155 ph10 122 o Remember an initial string rather than just 1 char?
156 ph10 181
157 ph10 122 o A required byte from alternatives - not just the last char, but an
158     earlier one if common to all alternatives.
159 ph10 181
160 ph10 122 o Minimum length of subject needed.
161 ph10 181
162 ph10 122 o Friedl contains other ideas.
163 ph10 181
164 ph10 122 . If Perl gets to a consistent state over the settings of capturing sub-
165     patterns inside repeats, see if we can match it. One example of the
166     difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
167     leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
168     because I think it needs much more state to be remembered.
169    
170 ph10 181 . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
171    
172 ph10 122 . Unicode
173    
174 ph10 181 * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX
175     character classes. For the moment, I've chosen not to support this for
176     backward compatibility, for speed, and because it would be messy to
177 ph10 122 implement.
178 ph10 181
179 ph10 122 * A different approach to Unicode might be to use a typedef to do everything
180     in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
181     new typedef to distinguish data from bits of compiled pattern that are in
182     bytes, I think. There would need to be conversion functions in and out. I
183     don't think this is particularly trivial - and anyway, Unicode now has
184     characters that need more than 16 bits, so is this at all sensible?
185 ph10 181
186 ph10 122 * There has been a request for direct support of 16-bit characters and
187     UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
188     is this worth it at all? One possible way of handling 16-bit characters
189     would be to "load" them in the same way that UTF-8 characters are loaded.
190 ph10 181
191 ph10 122 . Allow errorptr and erroroffset to be NULL. I don't like this idea.
192    
193     . Line endings:
194    
195     * Option to use NUL as a line terminator in subject strings. This could now
196     be done relatively easily since the extension to support LF, CR, and CRLF.
197 ph10 181 If this is done, a suitable option for pcregrep is also required.
198    
199 ph10 122 . Option to provide the pattern with a length instead of with a NUL terminator.
200 ph10 181 This probably affects quite a few places in the code.
201 ph10 122
202 ph10 181 . Catch SIGSEGV for stack overflows?
203 ph10 122
204     . A feature to suspend a match via a callout was once requested.
205    
206     . Option to convert results into character offsets and character lengths.
207    
208 ph10 181 . Option for pcregrep to scan only the start of a file. I am not keen - this is
209 ph10 122 the job of "head".
210 ph10 181
211     . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
212 ph10 122 preceded by a blank line, instead of adding it to every matched line, and (b)
213     support --outputfile=name.
214 ph10 181
215 ph10 122 . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
216    
217 ph10 181 . Add a user pointer to pcre_malloc/free functions -- some option would be
218 ph10 122 needed to retain backward compatibility.
219 ph10 181
220 ph10 122 . Define a union for the results from pcre_fullinfo().
221    
222 ph10 181 . Provide a "random access to the subject" facility so that the way in which it
223     is stored is independent of PCRE. For efficiency, it probably isn't possible
224 ph10 122 to switch this dynamically. It would have to be specified when PCRE was
225     compiled. PCRE would then call a function every time it wanted a character.
226 ph10 181
227 ph10 122 . Wild thought: the ability to compile from PCRE's internal byte code to a real
228     FSM and a very fast (third) matcher to process the result. There would be
229     even more restrictions than for pcre_dfa_exec(), however. This is not easy.
230 ph10 181
231 ph10 122 . Should pcretest have some private locale data, to avoid relying on the
232     available locales for the test data, since different OS have different ideas?
233     This won't be as thorough a test, but perhaps that doesn't really matter.
234 ph10 181
235     . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
236 ph10 122 them will of course slow it down.
237    
238 ph10 181 . Someone suggested --disable-callout to save code space when callouts are
239     never wanted. This seems rather marginal.
240 ph10 212
241     . Check names that consist entirely of digits: PCRE allows, but do Perl and
242     Python, etc?
243 ph10 122
244     Philip Hazel
245     Email local part: ph10
246     Email domain: cam.ac.uk
247 ph10 292 Last updated: 27 December 2007

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