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code/trunk/maintain/README revision 99 by ph10, Tue Mar 6 12:27:42 2007 UTC code/trunk/maint/README revision 372 by ph10, Tue Aug 26 11:49:38 2008 UTC
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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  132html         A Perl script that converts a .1 or .3 man page into HTML. It  and programs that are used for the maintenance of PCRE, but which do not form
6                  is called from MakeRelease. It "knows" the relevant troff  part of the PCRE distribution tarballs. This document describes these files and
7                  constructs that are used in the PCRE man pages.  also contains some notes for maintainers. Its contents are:
8    
9  Builducptable   A Perl script that creates the contents of the ucptable.h file    Files in the maint directory
10                  from two Unicode data files, which themselves are downloaded    Updating to a new Unicode release
11                  from the Unicode web site. Run this script in the "maintain"    Preparing for a PCRE release
12                  directory.    Making a PCRE release
13      Long-term ideas (wish list)
14  CleanTxt        A Perl script that cleans up the output of "nroff -man" by  
15                  removing backspaces and other redundant text so as to produce  
16                  a readable .txt file. It is called from MakeRelease.  Files in the maint directory
17    ----------------------------
18  Detrail         A Perl script that removes trailing spaces from files. It is  
19                  called from MakeRelease.  ----------------- This file is now OBSOLETE and no longer used ----------------
20    Builducptable    A Perl script that creates the contents of the ucptable.h file
21  Index.html      A file that is copied as index.html into the doc/html                   from two Unicode data files, which themselves are downloaded
22                  directory when the HTML documentation is being built. It works                   from the Unicode web site. Run this script in the "maint"
23                  like this so that doc/html can be deleted and re-created from                   directory.
24                  scratch.  ----------------- This file is now OBSOLETE and no longer used ----------------
25    
26  MakeRelease     My script for creating a new release. It processes the  GenerateUtt.py   A Python script to generate part of the pcre_tables.c file
27                  documentation man pages into .text and HTML formats before                   that contains Unicode script names in a long string with
28                  creating tarballs and putting them in the Releases directory.                   offsets, which is tedious to maintain by hand.
29    
30  Tech.Notes      Some notes about the internals of the PCRE code.  ManyConfigTests  A shell script that runs "configure, make, test" a number of
31                     times with different configuration settings.
32  Unicode.tables  The files in this directory, Scripts.txt and UnicodeData.txt,  
33                  were downloaded from the Unicode web site. They contain  MultiStage2.py   A Python script that generates the file pcre_ucd.c from three
34                  information about Unicode characters and scripts.                   Unicode data tables, which are themselves downloaded from the
35                     Unicode web site. Run this script in the "maint" directory.
36  ucptest.c       A short C program for testing the Unicode property functions in                   The generated file contains the tables for a 2-stage lookup
37                  pcre_ucp_searchfuncs.c, mainly useful after rebuilding the                   of Unicode properties.
38                  Unicode property table. Compile and run this in the "maintain"  
39                  directory.  Unicode.tables   The files in this directory, DerivedGeneralCategory.txt,
40                     Scripts.txt and UnicodeData.txt, were downloaded from the
41  ucptestdata     A directory containing two files, testinput1 and testoutput1,                   Unicode web site. They contain information about Unicode
42                  to use in conjunction with the ucptest program.                   characters and scripts.
43    
44  utf8.c          A short, freestanding C program for converting a Unicode code  ucptest.c        A short C program for testing the Unicode property macros
45                  point into a sequence of bytes in the UTF-8 encoding, and vice                   that do lookups in the pcre_ucd.c data, mainly useful after
46                  versa. If its argument is a hex number such as 0x1234, it                   rebuilding the Unicode property table. Compile and run this in
47                  outputs a list of the equivalent UTF-8 bytes. If its argument                   the "maint" directory (see comments at its head).
48                  is sequence of concatenated UTF-8 bytes (e.g. e188b4) it treats  
49                  them as a UTF-8 character and outputs the equivalent code point  ucptestdata      A directory containing two files, testinput1 and testoutput1,
50                  in hex.                   to use in conjunction with the ucptest program.
51    
52  When there is a new release of Unicode, the files in Unicode.tables must be  utf8.c           A short, freestanding C program for converting a Unicode code
53  refreshed from the web site, and the Buildupctable script can then be run to                   point into a sequence of bytes in the UTF-8 encoding, and vice
54  generate a new version of ucptable.h. The ucptest program can be used to check                   versa. If its argument is a hex number such as 0x1234, it
55  that the resulting table works properly, using the data files in ucptestdata to                   outputs a list of the equivalent UTF-8 bytes. If its argument
56  check a number of test characters.                   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, the source file ucp.h and both the MultiStage2.py and the
67    GenerateUtt.py scripts must be edited to add the new names. Then the
68    MultiStage2.py script can then be run to generate a new version of pcre_ucd.c
69    and the GenerateUtt.py can be run to generate the tricky tables for inclusion
70    in pcre_tables.c.
71    
72    The ucptest program can then be compiled and used to check that the new tables
73    in pcre_ucd.c work properly, using the data files in ucptestdata to check a
74    number of test characters.
75    
76    
77    Preparing for a PCRE release
78    ----------------------------
79    
80    This section contains a checklist of things that I consult before building a
81    distribution for a new release.
82    
83    . Ensure that the version number and version date are correct in configure.ac,
84      ChangeLog, and NEWS.
85    
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    
89    . Run ./autogen.sh to ensure everything is up-to-date.
90    
91    . Compile and test with many different config options, and combinations of
92      options. The maint/ManyConfigTests script now encapsulates this testing.
93    
94    . Run perltest.pl on the test data for tests 1 and 4. The output should match
95      the PCRE test output, apart from the version identification at the top. The
96      other tests are not Perl-compatible (they use various special PCRE options).
97    
98    . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
99      valgrind", though that takes quite a long time.
100    
101    . It may also useful to test with Electric Fence, though the fact that it
102      grumbles for missing free() calls can be a nuisance. (A missing free() in
103      pcretest is hardly a big problem.) To build with EF, use:
104    
105        LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
106    
107      Then all normal runs use it to check for buffer overflow. Also run everything
108      with:
109    
110        EF_PROTECT_BELOW=1 <whatever>
111    
112      because there have been problems with lookbehinds that looked too far.
113    
114    . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
115      HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
116      used" warnings for the modules in which there is no call to memmove(). These
117      can be ignored.
118    
119    . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,
120      LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't
121      need changing, but over the long term things do change.
122    
123    . Man pages: Check all man pages for \ not followed by e or f or " because
124      that indicates a markup error.
125    
126    . When the release is built, test it on a number of different operating
127      systems if possible, and using different compilers as well. For example,
128      on Solaris it is helpful to test using Sun's cc compiler as a change from
129      gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
130      needs -S 64 for pcretest to increase the stack size for test 2.
131    
132    
133    Making a PCRE release
134    ---------------------
135    
136    Run PrepareRelease and commit the files that it changes (by removing trailing
137    spaces). Then run "make distcheck" to create the tarballs and the zipball.
138    Double-check with "svn status", then create an SVN tagged copy:
139    
140      svn copy svn://vcs.exim.org/pcre/code/trunk \
141               svn://vcs.exim.org/pcre/code/tags/pcre-7.x
142    
143    Don't forget to update Freshmeat when the new release is out, and to tell
144    webmaster@pcre.org and the mailing list.
145    
146    
147    Future ideas (wish list)
148    ------------------------
149    
150    This section records a list of ideas so that they do not get forgotten. They
151    vary enormously in their usefulness and potential for implementation. Some are
152    very sensible; some are rather wacky. Some have been on this list for years;
153    others are relatively new.
154    
155    . Optimization
156    
157      There are always ideas for new optimizations so as to speed up pattern
158      matching. Most of them try to save work by recognizing a non-match without
159      having to scan all the possibilities. These are some that I've recorded:
160    
161      * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
162        slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
163        OTOH, this is pathological - the user could easily fix it.
164    
165      * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
166        to have little effect, and maybe makes things worse.
167    
168      * "Ends with literal string" - note that a single character doesn't gain much
169        over the existing "required byte" (reqbyte) feature that just saves one
170        byte.
171    
172      * These probably need to go in study():
173    
174        o Remember an initial string rather than just 1 char?
175    
176        o A required byte from alternatives - not just the last char, but an
177          earlier one if common to all alternatives.
178    
179        o Minimum length of subject needed.
180    
181        o Friedl contains other ideas.
182    
183    . 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.
188    
189    . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
190    
191    . Unicode
192    
193      * 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        implement.
197    
198      * 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    
205      * 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    
210    . Allow errorptr and erroroffset to be NULL. I don't like this idea.
211    
212    . Line endings:
213    
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        If this is done, a suitable option for pcregrep is also required.
217    
218    . Option to provide the pattern with a length instead of with a NUL terminator.
219      This probably affects quite a few places in the code.
220    
221    . Catch SIGSEGV for stack overflows?
222    
223    . A feature to suspend a match via a callout was once requested.
224    
225    . Option to convert results into character offsets and character lengths.
226    
227    . Option for pcregrep to scan only the start of a file. I am not keen - this is
228      the job of "head".
229    
230    . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
231      preceded by a blank line, instead of adding it to every matched line, and (b)
232      support --outputfile=name.
233    
234    . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
235    
236    . Add a user pointer to pcre_malloc/free functions -- some option would be
237      needed to retain backward compatibility.
238    
239    . Define a union for the results from pcre_fullinfo().
240    
241    . 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      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    
246    . 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    
250    . 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    
254    . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
255      them will of course slow it down.
256    
257    . Someone suggested --disable-callout to save code space when callouts are
258      never wanted. This seems rather marginal.
259    
260    . Check names that consist entirely of digits: PCRE allows, but do Perl and
261      Python, etc?
262    
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.
267    
268    . Callouts with arguments: (?Cn:ARG) for instance.
269    
270    . A user is going to supply a patch to generalize the API for user-specific
271      memory allocation so that it is more flexible in threaded environments.
272    
273    Philip Hazel
274    Email local part: ph10
275    Email domain: cam.ac.uk
276    Last updated: 26 August 2008

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