/[pcre]/code/trunk/maint/README
ViewVC logotype

Diff of /code/trunk/maint/README

Parent Directory Parent Directory | Revision Log Revision Log | View Patch Patch

code/trunk/maintain/README revision 111 by ph10, Thu Mar 8 16:53:09 2007 UTC code/trunk/maint/README revision 351 by ph10, Fri Jul 4 18:27:16 2008 UTC
# Line 1  Line 1 
1  The files in the "maintain" directory of the PCRE source contain data, scripts,  MAINTENANCE README FOR PCRE
2  and programs that are used for the maintenance of PCRE, but do not form part of  ---------------------------
3  the PCRE distribution tarballs.  
4    The files in the "maint" directory of the PCRE source contain data, scripts,
5  Builducptable   A Perl script that creates the contents of the ucptable.h file  and programs that are used for the maintenance of PCRE, but which do not form
6                  from two Unicode data files, which themselves are downloaded  part of the PCRE distribution tarballs. This document describes these files and
7                  from the Unicode web site. Run this script in the "maintain"  also contains some notes for maintainers. Its contents are:
8                  directory.  
9      Files in the maint directory
10  Tech.Notes      Some notes about the internals of the PCRE code.    Updating to a new Unicode release
11      Preparing for a PCRE release
12  Unicode.tables  The files in this directory, Scripts.txt and UnicodeData.txt,    Making a PCRE release
13                  were downloaded from the Unicode web site. They contain    Long-term ideas (wish list)
14                  information about Unicode characters and scripts.  
15    
16  ucptest.c       A short C program for testing the Unicode property functions in  Files in the maint directory
17                  pcre_ucp_searchfuncs.c, mainly useful after rebuilding the  ----------------------------
18                  Unicode property table. Compile and run this in the "maintain"  
19                  directory.  ----------------- This file is now OBSOLETE and no longer used ----------------
20    Builducptable    A Perl script that creates the contents of the ucptable.h file
21  ucptestdata     A directory containing two files, testinput1 and testoutput1,                   from two Unicode data files, which themselves are downloaded
22                  to use in conjunction with the ucptest program.                   from the Unicode web site. Run this script in the "maint"
23                     directory.
24  utf8.c          A short, freestanding C program for converting a Unicode code  ----------------- This file is now OBSOLETE and no longer used ----------------
25                  point into a sequence of bytes in the UTF-8 encoding, and vice  
26                  versa. If its argument is a hex number such as 0x1234, it  GenerateUtt.py   A Python script to generate part of the pcre_tables.c file
27                  outputs a list of the equivalent UTF-8 bytes. If its argument                   that contains Unicode script names in a long string with
28                  is sequence of concatenated UTF-8 bytes (e.g. e188b4) it treats                   offsets, which is tedious to maintain by hand.
29                  them as a UTF-8 character and outputs the equivalent code point  
30                  in hex.  ManyConfigTests  A shell script that runs "configure, make, test" a number of
31                     times with different configuration settings.
32  When there is a new release of Unicode, the files in Unicode.tables must be  
33  refreshed from the web site, and the Buildupctable script can then be run to  MultiStage2.py   A Python script that generates the file pcre_ucd.c from three
34  generate a new version of ucptable.h. The ucptest program can be used to check                   Unicode data tables, which are themselves downloaded from the
35  that the resulting table works properly, using the data files in ucptestdata to                   Unicode web site. Run this script in the "maint" directory.
36  check a number of test characters.                   The generated file contains the tables for a 2-stage lookup
37                     of Unicode properties.
38  ****  
39    Unicode.tables   The files in this directory, DerivedGeneralCategory.txt,
40                     Scripts.txt and UnicodeData.txt, were downloaded from the
41                     Unicode web site. They contain information about Unicode
42                     characters and scripts.
43    
44    ucptest.c        A short C program for testing the Unicode property macros
45                     that do lookups in the pcre_ucd.c data, mainly useful after
46                     rebuilding the Unicode property table. Compile and run this in
47                     the "maint" directory (see comments at its head).
48    
49    ucptestdata      A directory containing two files, testinput1 and testoutput1,
50                     to use in conjunction with the ucptest program.
51    
52    utf8.c           A short, freestanding C program for converting a Unicode code
53                     point into a sequence of bytes in the UTF-8 encoding, and vice
54                     versa. If its argument is a hex number such as 0x1234, it
55                     outputs a list of the equivalent UTF-8 bytes. If its argument
56                     is sequence of concatenated UTF-8 bytes (e.g. e188b4) it
57                     treats them as a UTF-8 character and outputs the equivalent
58                     code point in hex.
59    
60    
61    Updating to a new Unicode release
62    ---------------------------------
63    
64    When there is a new release of Unicode, the files in Unicode.tables must be
65    refreshed from the web site. If the new version of Unicode adds new character
66    scripts, both the MultiStage2.py and the GenerateUtt.py scripts must be edited
67    to add the new names. Then the MultiStage2.py script can then be run to
68    generate a new version of pcre_ucd.c and the GenerateUtt.py can be run to
69    generate the tricky tables in pcre_tables.c.
70    
71    The ucptest program can then be compiled and used to check that the new tables
72    in pcre_ucd.c work properly, using the data files in ucptestdata to check a
73    number of test characters.
74    
75    
76    Preparing for a PCRE release
77    ----------------------------
78    
79    This section contains a checklist of things that I consult before building a
80    distribution for a new release.
81    
82    . Ensure that the version number and version date are correct in configure.ac,
83      ChangeLog, and NEWS.
84    
85    . If new build options have been added, ensure that they are added to the CMake
86      files as well as to the autoconf files.
87    
88    . Run ./autogen.sh to ensure everything is up-to-date.
89    
90    . Compile and test with many different config options, and combinations of
91      options. The maint/ManyConfigTests script now encapsulates this testing.
92    
93    . Run perltest.pl on the test data for tests 1 and 4. The output should match
94      the PCRE test output, apart from the version identification at the top. The
95      other tests are not Perl-compatible (they use various special PCRE options).
96    
97    . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
98      valgrind", though that takes quite a long time.
99    
100    . It may also useful to test with Electric Fence, though the fact that it
101      grumbles for missing free() calls can be a nuisance. (A missing free() in
102      pcretest is hardly a big problem.) To build with EF, use:
103    
104        LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
105    
106      Then all normal runs use it to check for buffer overflow. Also run everything
107      with:
108    
109        EF_PROTECT_BELOW=1 <whatever>
110    
111      because there have been problems with lookbehinds that looked too far.
112    
113    . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
114      HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
115      used" warnings for the modules in which there is no call to memmove(). These
116      can be ignored.
117    
118    . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,
119      LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't
120      need changing, but over the long term things do change.
121    
122    . Man pages: Check all man pages for \ not followed by e or f or " because
123      that indicates a markup error.
124    
125    . When the release is built, test it on a number of different operating
126      systems if possible, and using different compilers as well. For example,
127      on Solaris it is helpful to test using Sun's cc compiler as a change from
128      gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
129      needs -S 64 for pcretest to increase the stack size for test 2.
130    
131    
132    Making a PCRE release
133    ---------------------
134    
135    Run PrepareRelease and commit the files that it changes (by removing trailing
136    spaces). Then run "make distcheck" to create the tarballs and the zipball.
137    Double-check with "svn status", then create an SVN tagged copy:
138    
139      svn copy svn://vcs.exim.org/pcre/code/trunk \
140               svn://vcs.exim.org/pcre/code/tags/pcre-7.x
141    
142    Don't forget to update Freshmeat when the new release is out, and to tell
143    webmaster@pcre.org and the mailing list.
144    
145    
146    Future ideas (wish list)
147    ------------------------
148    
149    This section records a list of ideas so that they do not get forgotten. They
150    vary enormously in their usefulness and potential for implementation. Some are
151    very sensible; some are rather wacky. Some have been on this list for years;
152    others are relatively new.
153    
154    . Optimization
155    
156      There are always ideas for new optimizations so as to speed up pattern
157      matching. Most of them try to save work by recognizing a non-match without
158      having to scan all the possibilities. These are some that I've recorded:
159    
160      * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
161        slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
162        OTOH, this is pathological - the user could easily fix it.
163    
164      * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
165        to have little effect, and maybe makes things worse.
166    
167      * "Ends with literal string" - note that a single character doesn't gain much
168        over the existing "required byte" (reqbyte) feature that just saves one
169        byte.
170    
171      * These probably need to go in study():
172    
173        o Remember an initial string rather than just 1 char?
174    
175        o A required byte from alternatives - not just the last char, but an
176          earlier one if common to all alternatives.
177    
178        o Minimum length of subject needed.
179    
180        o Friedl contains other ideas.
181    
182    . If Perl gets to a consistent state over the settings of capturing sub-
183      patterns inside repeats, see if we can match it. One example of the
184      difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
185      leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
186      because I think it needs much more state to be remembered.
187    
188    . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
189    
190    . Unicode
191    
192      * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX
193        character classes. For the moment, I've chosen not to support this for
194        backward compatibility, for speed, and because it would be messy to
195        implement.
196    
197      * A different approach to Unicode might be to use a typedef to do everything
198        in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
199        new typedef to distinguish data from bits of compiled pattern that are in
200        bytes, I think. There would need to be conversion functions in and out. I
201        don't think this is particularly trivial - and anyway, Unicode now has
202        characters that need more than 16 bits, so is this at all sensible?
203    
204      * There has been a request for direct support of 16-bit characters and
205        UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
206        is this worth it at all? One possible way of handling 16-bit characters
207        would be to "load" them in the same way that UTF-8 characters are loaded.
208    
209    . Allow errorptr and erroroffset to be NULL. I don't like this idea.
210    
211    . Line endings:
212    
213      * Option to use NUL as a line terminator in subject strings. This could now
214        be done relatively easily since the extension to support LF, CR, and CRLF.
215        If this is done, a suitable option for pcregrep is also required.
216    
217    . Option to provide the pattern with a length instead of with a NUL terminator.
218      This probably affects quite a few places in the code.
219    
220    . Catch SIGSEGV for stack overflows?
221    
222    . A feature to suspend a match via a callout was once requested.
223    
224    . Option to convert results into character offsets and character lengths.
225    
226    . Option for pcregrep to scan only the start of a file. I am not keen - this is
227      the job of "head".
228    
229    . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
230      preceded by a blank line, instead of adding it to every matched line, and (b)
231      support --outputfile=name.
232    
233    . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
234    
235    . Add a user pointer to pcre_malloc/free functions -- some option would be
236      needed to retain backward compatibility.
237    
238    . Define a union for the results from pcre_fullinfo().
239    
240    . Provide a "random access to the subject" facility so that the way in which it
241      is stored is independent of PCRE. For efficiency, it probably isn't possible
242      to switch this dynamically. It would have to be specified when PCRE was
243      compiled. PCRE would then call a function every time it wanted a character.
244    
245    . Wild thought: the ability to compile from PCRE's internal byte code to a real
246      FSM and a very fast (third) matcher to process the result. There would be
247      even more restrictions than for pcre_dfa_exec(), however. This is not easy.
248    
249    . Should pcretest have some private locale data, to avoid relying on the
250      available locales for the test data, since different OS have different ideas?
251      This won't be as thorough a test, but perhaps that doesn't really matter.
252    
253    . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
254      them will of course slow it down.
255    
256    . Someone suggested --disable-callout to save code space when callouts are
257      never wanted. This seems rather marginal.
258    
259    . Check names that consist entirely of digits: PCRE allows, but do Perl and
260      Python, etc?
261    
262    Philip Hazel
263    Email local part: ph10
264    Email domain: cam.ac.uk
265    Last updated: 04 July 2008

Legend:
Removed from v.111  
changed lines
  Added in v.351

  ViewVC Help
Powered by ViewVC 1.1.5