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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 155 by ph10, Tue Apr 24 13:36:11 2007 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  ---------------------------
 the PCRE distribution tarballs.  
   
 132html         A Perl script that converts a .1 or .3 man page into HTML. It  
                 is called from MakeRelease. It "knows" the relevant troff  
                 constructs that are used in the PCRE man pages.  
   
 Builducptable   A Perl script that creates the contents of the ucptable.h file  
                 from two Unicode data files, which themselves are downloaded  
                 from the Unicode web site. Run this script in the "maintain"  
                 directory.  
   
 CleanTxt        A Perl script that cleans up the output of "nroff -man" by  
                 removing backspaces and other redundant text so as to produce  
                 a readable .txt file. It is called from MakeRelease.  
   
 Detrail         A Perl script that removes trailing spaces from files. It is  
                 called from MakeRelease.  
3    
4  Index.html      A file that is copied as index.html into the doc/html  The files in the "maint" directory of the PCRE source contain data, scripts,
5                  directory when the HTML documentation is being built. It works  and programs that are used for the maintenance of PCRE, but which do not form
6                  like this so that doc/html can be deleted and re-created from  part of the PCRE distribution tarballs. This document describes these files and
7                  scratch.  also contains some notes for maintainers. Its contents are:
8    
9  MakeRelease     My script for creating a new release. It processes the    Files in the maint directory
10                  documentation man pages into .text and HTML formats before    Updating to a new Unicode release
11                  creating tarballs and putting them in the Releases directory.    Preparing for a PCRE release
12      Making a PCRE release
13  Tech.Notes      Some notes about the internals of the PCRE code.    Long-term ideas (wish list)
14    
15  Unicode.tables  The files in this directory, Scripts.txt and UnicodeData.txt,  
16                  were downloaded from the Unicode web site. They contain  Files in the maint directory
17                  information about Unicode characters and scripts.  ----------------------------
18    
19  ucptest.c       A short C program for testing the Unicode property functions in  Builducptable    A Perl script that creates the contents of the ucptable.h file
20                  pcre_ucp_searchfuncs.c, mainly useful after rebuilding the                   from two Unicode data files, which themselves are downloaded
21                  Unicode property table. Compile and run this in the "maintain"                   from the Unicode web site. Run this script in the "maint"
22                  directory.                   directory.
23    
24  ucptestdata     A directory containing two files, testinput1 and testoutput1,  ManyConfigTests  A shell script that runs "configure, make, test" a number of
25                  to use in conjunction with the ucptest program.                   times with different configuration settings.
26    
27  utf8.c          A short, freestanding C program for converting a Unicode code  Unicode.tables   The files in this directory, Scripts.txt and UnicodeData.txt,
28                  point into a sequence of bytes in the UTF-8 encoding, and vice                   were downloaded from the Unicode web site. They contain
29                  versa. If its argument is a hex number such as 0x1234, it                   information about Unicode characters and scripts.
30                  outputs a list of the equivalent UTF-8 bytes. If its argument  
31                  is sequence of concatenated UTF-8 bytes (e.g. e188b4) it treats  ucptest.c        A short C program for testing the Unicode property functions
32                  them as a UTF-8 character and outputs the equivalent code point                   in pcre_ucp_searchfuncs.c, mainly useful after rebuilding the
33                  in hex.                   Unicode property table. Compile and run this in the "maint"
34                     directory.
35    
36    ucptestdata      A directory containing two files, testinput1 and testoutput1,
37                     to use in conjunction with the ucptest program.
38    
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.
46    
47    
48    Updating to a new Unicode release
49    ---------------------------------
50    
51  When there is a new release of Unicode, the files in Unicode.tables must be  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  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  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  that the resulting table works properly, using the data files in ucptestdata to
55  check a number of test characters.  check a number of test characters.
56    
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    . Ensure that the version number and version date are correct in configure.ac,
65      ChangeLog, and NEWS.
66    
67    . Run ./autogen.sh to ensure everything is up-to-date.
68    
69    . Compile and test with many different config options, and combinations of
70      options. The maint/ManyConfigTests script now encapsulates this testing.
71    
72    . Run perltest.pl on the test data for tests 1 and 4. The output should match
73      the PCRE test output, apart from the version identification at the top. The
74      other tests are not Perl-compatible (they use various special PCRE options).
75    
76    . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest
77      valgrind", though that takes quite a long time.
78    
79    . It may also useful to test with Electric Fence, though the fact that it
80      grumbles for missing free() calls can be a nuisance. (A missing free() in
81      pcretest is hardly a big problem.) To build with EF, use:
82    
83        LIBS='/usr/lib/libefence.a -lpthread' with ./configure.
84    
85      Then all normal runs use it to check for buffer overflow. Also run everything
86      with:
87    
88        EF_PROTECT_BELOW=1 <whatever>
89    
90      because there have been problems with lookbehinds that looked too far.
91    
92    . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and
93      HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not
94      used" warnings for the modules in which there is no call to memmove(). These
95      can be ignored.
96    
97    . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,
98      LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't
99      need changing, but over the long term things do change.
100    
101    . Man pages: Check all man pages for \ not followed by e or f or " because
102      that indicates a markup error.
103    
104    . When the release is built, test it on a number of different operating
105      systems if possible, and using different compilers as well. For example,
106      on Solaris it is helpful to test using Sun's cc compiler as a change from
107      gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also
108      needs -S 64 for pcretest to increase the stack size for test 2.
109    
110    
111    Making a PCRE release
112    ---------------------
113    
114    Run PrepareRelease and commit the files that it changes (by removing trailing
115    spaces). Then run "make distcheck" to create the tarballs and the zipball.
116    
117    Don't forget to update Freshmeat when the new release is out, and to tell
118    webmaster@pcre.org and the mailing list.
119    
120    
121    Future ideas (wish list)
122    ------------------------
123    
124    This section records a list of ideas so that they do not get forgotten. They
125    vary enormously in their usefulness and potential for implementation. Some are
126    very sensible; some are rather wacky. Some have been on this list for years;
127    others are relatively new.
128    
129    . Optimization
130    
131      There are always ideas for new optimizations so as to speed up pattern
132      matching. Most of them try to save work by recognizing a non-match without
133      having to scan all the possibilities. These are some that I've recorded:
134    
135      * /((A{0,5}){0,5}){0,5}(something complex)/ on a non-matching string is very
136        slow, though Perl is fast. Can we speed up somehow? Convert to {0,125}?
137        OTOH, this is pathological - the user could easily fix it.
138    
139      * Turn ={4} into ==== ? (for speed). I once did an experiment, and it seems
140        to have little effect, and maybe makes things worse.
141    
142      * "Ends with literal string" - note that a single character doesn't gain much
143        over the existing "required byte" (reqbyte) feature that just saves one
144        byte.
145    
146      * These probably need to go in study():
147    
148        o Remember an initial string rather than just 1 char?
149    
150        o A required byte from alternatives - not just the last char, but an
151          earlier one if common to all alternatives.
152    
153        o Minimum length of subject needed.
154    
155        o Friedl contains other ideas.
156    
157    . If Perl gets to a consistent state over the settings of capturing sub-
158      patterns inside repeats, see if we can match it. One example of the
159      difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
160      leaves $2 set. In Perl, it's unset. Changing this in PCRE will be very hard
161      because I think it needs much more state to be remembered.
162    
163    . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
164    
165    . Unicode
166    
167      * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX
168        character classes. For the moment, I've chosen not to support this for
169        backward compatibility, for speed, and because it would be messy to
170        implement.
171    
172      * A different approach to Unicode might be to use a typedef to do everything
173        in unsigned shorts instead of unsigned chars. Actually, we'd have to have a
174        new typedef to distinguish data from bits of compiled pattern that are in
175        bytes, I think. There would need to be conversion functions in and out. I
176        don't think this is particularly trivial - and anyway, Unicode now has
177        characters that need more than 16 bits, so is this at all sensible?
178    
179      * There has been a request for direct support of 16-bit characters and
180        UTF-16. However, since Unicode is moving beyond purely 16-bit characters,
181        is this worth it at all? One possible way of handling 16-bit characters
182        would be to "load" them in the same way that UTF-8 characters are loaded.
183    
184    . Allow errorptr and erroroffset to be NULL. I don't like this idea.
185    
186    . Line endings:
187    
188      * Option to use NUL as a line terminator in subject strings. This could now
189        be done relatively easily since the extension to support LF, CR, and CRLF.
190        If this is done, a suitable option for pcregrep is also required.
191    
192    . Option to provide the pattern with a length instead of with a NUL terminator.
193      This probably affects quite a few places in the code.
194    
195    . Catch SIGSEGV for stack overflows?
196    
197    . "Cut" as described in Jeffrey Friedl's book, p364: \v and \V. The definitions
198      aren't yet clear enough for me. \v flushes saved states so that no
199      backtracking to anything earlier can happen; \V says "no more bumpalong", but
200      does it fail the current match? As described in the book, these aren't really
201      "cut" as in Prolog, are they? NOTE: (a) PCRE once had "cut", but it was
202      removed when atomic groups were introduced. (b) Perl 5.10 has some (*PRUNE)
203      features -- see below.
204    
205    . A feature to suspend a match via a callout was once requested.
206    
207    . Option to convert results into character offsets and character lengths.
208    
209    . Option for pcregrep to scan only the start of a file. I am not keen - this is
210      the job of "head".
211    
212    . A (non-Unix) user wanted pcregrep options to (a) list a file name just once,
213      preceded by a blank line, instead of adding it to every matched line, and (b)
214      support --outputfile=name.
215    
216    . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.
217    
218    . Add a user pointer to pcre_malloc/free functions -- some option would be
219      needed to retain backward compatibility.
220    
221    . Define a union for the results from pcre_fullinfo().
222    
223    . Provide a "random access to the subject" facility so that the way in which it
224      is stored is independent of PCRE. For efficiency, it probably isn't possible
225      to switch this dynamically. It would have to be specified when PCRE was
226      compiled. PCRE would then call a function every time it wanted a character.
227    
228    . There are new (*PRUNE) facilities in Perl 5.10, some of which it might be
229      relatively easy to implement.
230    
231    . Also in Perl 5.10 are relative subroutine references (?&-1) and (?&+1) which
232      I didn't know about when I added some 5.10 features for PCRE 7.0. What about
233      (?(-1)... as a condition? That's an obvious extension, even if Perl 5.10
234      doesn't have it.
235    
236    . Wild thought: the ability to compile from PCRE's internal byte code to a real
237      FSM and a very fast (third) matcher to process the result. There would be
238      even more restrictions than for pcre_dfa_exec(), however. This is not easy.
239    
240    . Should pcretest have some private locale data, to avoid relying on the
241      available locales for the test data, since different OS have different ideas?
242      This won't be as thorough a test, but perhaps that doesn't really matter.
243    
244    . pcregrep: add -rs for a sorted recurse? Having to store file names and sort
245      them will of course slow it down.
246    
247    . Re-arrange test 2: take out the link-size dependent stuff for a separate test
248      that is run only when the link size *is* 2; leave in some non-numbered
249      debugging tests using the new /Z feature.
250    
251    . Stan Switzer's goto replacement for longjmp, which is apparently very slow on
252      OS-X. This is used when stack recursion is disabled. It would be worth doing
253      some timing tests on other OS.
254    
255    . Someone suggested --disable-callout to save code space when callouts are
256      never wanted. This seems rather marginal.
257    
258    . Work needs doing so that the pcregrep tests work better with different
259      linebreak settings. Currently, some tests don't work when the input files
260      do not have \n line endings.
261    
262    . If the fr_FR locale isn't available for testing, try "french" instead,
263      because this may be available on Windows. It means modifying the test data,
264      however.
265    
266    Philip Hazel
267    Email local part: ph10
268    Email domain: cam.ac.uk
269    Last updated: 24 April 2007

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