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1  MAINTENANCE README FOR PCRE  MAINTENANCE README FOR PCRE
2  ---------------------------  ===========================
3    
4  The files in the "maint" directory of the PCRE source contain data, scripts,  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  and programs that are used for the maintenance of PCRE, but which do not form
# Line 14  also contains some notes for maintainers Line 14  also contains some notes for maintainers
14    
15    
16  Files in the maint directory  Files in the maint directory
17  ----------------------------  ============================
18    
19  ----------------- This file is now OBSOLETE and no longer used ----------------  ---------------- This file is now OBSOLETE and no longer used ----------------
20  Builducptable    A Perl script that creates the contents of the ucptable.h file  Builducptable    A Perl script that creates the contents of the ucptable.h file
21                   from two Unicode data files, which themselves are downloaded                   from two Unicode data files, which themselves are downloaded
22                   from the Unicode web site. Run this script in the "maint"                   from the Unicode web site. Run this script in the "maint"
23                   directory.                   directory.
24  ----------------- This file is now OBSOLETE and no longer used ----------------  ---------------- This file is now OBSOLETE and no longer used ----------------
25    
26  GenerateUtt.py   A Python script to generate part of the pcre_tables.c file  GenerateUtt.py   A Python script to generate part of the pcre_tables.c file
27                   that contains Unicode script names in a long string with                   that contains Unicode script names in a long string with
28                   offsets, which is tedious to maintain by hand.                   offsets, which is tedious to maintain by hand.
29    
30  ManyConfigTests  A shell script that runs "configure, make, test" a number of  ManyConfigTests  A shell script that runs "configure, make, test" a number of
31                   times with different configuration settings.                   times with different configuration settings.
32    
33  MultiStage2.py   A Python script that generates the file pcre_ucd.c from three  MultiStage2.py   A Python script that generates the file pcre_ucd.c from three
34                   Unicode data tables, which are themselves downloaded from the                   Unicode data tables, which are themselves downloaded from the
35                   Unicode web site. Run this script in the "maint" directory.                   Unicode web site. Run this script in the "maint" directory.
36                   The generated file contains the tables for a 2-stage lookup                   The generated file contains the tables for a 2-stage lookup
37                   of Unicode properties.                   of Unicode properties.
38    
39  Unicode.tables   The files in this directory, DerivedGeneralCategory.txt,  pcre_chartables.c.non-standard
40                   Scripts.txt and UnicodeData.txt, were downloaded from the                   This is a set of character tables that came from a Windows
41                     system. It has characters greater than 128 that are set as
42                     spaces, amongst other things. I kept it so that it can be
43                     used for testing from time to time.
44    
45    README           This file.
46    
47    Unicode.tables   The files in this directory (CaseFolding.txt,
48                     DerivedGeneralCategory.txt, GraphemeBreakProperty.txt,
49                     Scripts.txt and UnicodeData.txt) were downloaded from the
50                   Unicode web site. They contain information about Unicode                   Unicode web site. They contain information about Unicode
51                   characters and scripts.                   characters and scripts.
52    
53  ucptest.c        A short C program for testing the Unicode property macros  ucptest.c        A short C program for testing the Unicode property macros
54                   that do lookups in the pcre_ucd.c data, mainly useful after                   that do lookups in the pcre_ucd.c data, mainly useful after
# Line 59  utf8.c           A short, freestanding C Line 68  utf8.c           A short, freestanding C
68    
69    
70  Updating to a new Unicode release  Updating to a new Unicode release
71  ---------------------------------  =================================
72    
73  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
74  refreshed from the web site. If the new version of Unicode adds new character  refreshed from the web site. If the new version of Unicode adds new character
75  scripts, the source file ucp.h and both the MultiStage2.py and the  scripts, the source file ucp.h and both the MultiStage2.py and the
76  GenerateUtt.py scripts must be edited to add the new names. Then the  GenerateUtt.py scripts must be edited to add the new names. Then MultiStage2.py
77  MultiStage2.py script can then be run to generate a new version of pcre_ucd.c  can be run to generate a new version of pcre_ucd.c, and GenerateUtt.py can be
78  and the GenerateUtt.py can be run to generate the tricky tables for inclusion  run to generate the tricky tables for inclusion in pcre_tables.c.
79  in pcre_tables.c.  
80    If MultiStage2.py gives the error "ValueError: list.index(x): x not in list",
81  The ucptest program can then be compiled and used to check that the new tables  the cause is usually a missing (or misspelt) name in the list of scripts. I
82  in pcre_ucd.c work properly, using the data files in ucptestdata to check a  couldn't find a straightforward list of scripts on the Unicode site, but
83  number of test characters.  there's a useful Wikipedia page that list them, and notes the Unicode version
84    in which they were introduced:
85    
86    http://en.wikipedia.org/wiki/Unicode_scripts#Table_of_Unicode_scripts
87    
88    The ucptest program can be compiled and used to check that the new tables in
89    pcre_ucd.c work properly, using the data files in ucptestdata to check a number
90    of test characters. The source file ucptest.c must be updated whenever new
91    Unicode script names are added.
92    
93    Note also that both the pcresyntax.3 and pcrepattern.3 man pages contain lists
94    of Unicode script names.
95    
96    
97  Preparing for a PCRE release  Preparing for a PCRE release
98  ----------------------------  ============================
99    
100  This section contains a checklist of things that I consult before building a  This section contains a checklist of things that I consult before building a
101  distribution for a new release.  distribution for a new release.
102    
103  . Ensure that the version number and version date are correct in configure.ac,  . Ensure that the version number and version date are correct in configure.ac.
104    ChangeLog, and NEWS.  
105    . Update the library version numbers in configure.ac according to the rules
106      given below.
107    
108  . If new build options have been added, ensure that they are added to the CMake  . If new build options have been added, ensure that they are added to the CMake
109    files as well as to the autoconf files.    files as well as to the autoconf files. The relevant files are CMakeLists.txt
110      and config-cmake.h.in. After making a release tarball, test it out with CMake
111      if there have been changes here.
112    
113  . Run ./autogen.sh to ensure everything is up-to-date.  . Run ./autogen.sh to ensure everything is up-to-date.
114    
115  . Compile and test with many different config options, and combinations of  . Compile and test with many different config options, and combinations of
116    options. The maint/ManyConfigTests script now encapsulates this testing.    options. Also, test with valgrind by running "RunTest valgrind" and
117      "RunGrepTest valgrind" (which takes quite a long time). The script
118      maint/ManyConfigTests now encapsulates this testing. It runs tests with
119      different configurations, and it also runs some of them with valgrind, all of
120      which can take quite some time.
121    
122    . Run perltest.pl on the test data for tests 1, 4, and 6. The output
123      should match the PCRE test output, apart from the version identification at
124      the start of each test. The other tests are not Perl-compatible (they use
125      various PCRE-specific features or options).
126    
127    . It is possible to test with the emulated memmove() function by undefining
128      HAVE_MEMMOVE and HAVE_BCOPY in config.h, though I do not do this often. You
129      may see a number of "pcre_memmove defined but not used" warnings for the
130      modules in which there is no call to memmove(). These can be ignored.
131    
132    . Documentation: check AUTHORS, ChangeLog (check version and date), LICENCE,
133      NEWS (check version and date), NON-AUTOTOOLS-BUILD, and README. Many of these
134      won't need changing, but over the long term things do change.
135    
136    . I used to test new releases myself on a number of different operating
137      systems, using different compilers as well. For example, on Solaris it is
138      helpful to test using Sun's cc compiler as a change from gcc. Adding
139      -xarch=v9 to the cc options does a 64-bit test, but it also needs -S 64 for
140      pcretest to increase the stack size for test 2. Since I retired I can no
141      longer do this, but instead I rely on putting out release candidates for
142      folks on the pcre-dev list to test.
143    
144    
145    Updating version info for libtool
146    =================================
147    
148  . Run perltest.pl on the test data for tests 1 and 4. The output should match  This set of rules for updating library version information came from a web page
149    the PCRE test output, apart from the version identification at the top. The  whose URL I have forgotten. The version information consists of three parts:
150    other tests are not Perl-compatible (they use various special PCRE options).  (current, revision, age).
151    
152  . Test with valgrind by running "RunTest valgrind". There is also "RunGrepTest  1. Start with version information of 0:0:0 for each libtool library.
   valgrind", though that takes quite a long time.  
153    
154  . It may also useful to test with Electric Fence, though the fact that it  2. Update the version information only immediately before a public release of
155    grumbles for missing free() calls can be a nuisance. (A missing free() in     your software. More frequent updates are unnecessary, and only guarantee
156    pcretest is hardly a big problem.) To build with EF, use:     that the current interface number gets larger faster.
157    
158      LIBS='/usr/lib/libefence.a -lpthread' with ./configure.  3. If the library source code has changed at all since the last update, then
159       increment revision; c:r:a becomes c:r+1:a.
160    
161    Then all normal runs use it to check for buffer overflow. Also run everything  4. If any interfaces have been added, removed, or changed since the last
162    with:     update, increment current, and set revision to 0.
163    
164      EF_PROTECT_BELOW=1 <whatever>  5. If any interfaces have been added since the last public release, then
165       increment age.
166    
167    because there have been problems with lookbehinds that looked too far.  6. If any interfaces have been removed or changed since the last public
168       release, then set age to 0.
169    
170  . Test with the emulated memmove() function by undefining HAVE_MEMMOVE and  The following explanation may help in understanding the above rules a bit
171    HAVE_BCOPY in config.h. You may see a number of "pcre_memmove defined but not  better. Consider that there are three possible kinds of reaction from users to
172    used" warnings for the modules in which there is no call to memmove(). These  changes in a shared library:
   can be ignored.  
173    
174  . Documentation: check AUTHORS, COPYING, ChangeLog (check date), INSTALL,  1. Programs using the previous version may use the new version as a drop-in
175    LICENCE, NEWS (check date), NON-UNIX-USE, and README. Many of these won't     replacement, and programs using the new version can also work with the
176    need changing, but over the long term things do change.     previous one. In other words, no recompiling nor relinking is needed. In
177       this case, increment revision only, don't touch current or age.
178    
179  . Man pages: Check all man pages for \ not followed by e or f or " because  2. Programs using the previous version may use the new version as a drop-in
180    that indicates a markup error.     replacement, but programs using the new version may use APIs not present in
181       the previous one. In other words, a program linking against the new version
182       may fail if linked against the old version at run time. In this case, set
183       revision to 0, increment current and age.
184    
185  . When the release is built, test it on a number of different operating  3. Programs may need to be changed, recompiled, relinked in order to use the
186    systems if possible, and using different compilers as well. For example,     new version. Increment current, set revision and age to 0.
   on Solaris it is helpful to test using Sun's cc compiler as a change from  
   gcc. Adding -xarch=v9 to the cc options does a 64-bit test, but it also  
   needs -S 64 for pcretest to increase the stack size for test 2.  
187    
188    
189  Making a PCRE release  Making a PCRE release
190  ---------------------  =====================
191    
192  Run PrepareRelease and commit the files that it changes (by removing trailing  Run PrepareRelease and commit the files that it changes (by removing trailing
193  spaces). Then run "make distcheck" to create the tarballs and the zipball.  spaces). The first thing this script does is to run CheckMan on the man pages;
194  Double-check with "svn status", then create an SVN tagged copy:  if it finds any markup errors, it reports them and then aborts.
195    
196    Once PrepareRelease has run clean, run "make distcheck" to create the tarballs
197    and the zipball. Double-check with "svn status", then create an SVN tagged
198    copy:
199    
200    svn copy svn://vcs.exim.org/pcre/code/trunk \    svn copy svn://vcs.exim.org/pcre/code/trunk \
201             svn://vcs.exim.org/pcre/code/tags/pcre-7.x             svn://vcs.exim.org/pcre/code/tags/pcre-8.xx
202    
203  Don't forget to update Freshmeat when the new release is out, and to tell  Don't forget to update Freshmeat when the new release is out, and to tell
204  webmaster@pcre.org and the mailing list.  webmaster@pcre.org and the mailing list. Also, update the list of version
205    numbers in Bugzilla (edit products).
206    
207    
208  Future ideas (wish list)  Future ideas (wish list)
209  ------------------------  ========================
210    
211  This section records a list of ideas so that they do not get forgotten. They  This section records a list of ideas so that they do not get forgotten. They
212  vary enormously in their usefulness and potential for implementation. Some are  vary enormously in their usefulness and potential for implementation. Some are
# Line 166  others are relatively new. Line 227  others are relatively new.
227      to have little effect, and maybe makes things worse.      to have little effect, and maybe makes things worse.
228    
229    * "Ends with literal string" - note that a single character doesn't gain much    * "Ends with literal string" - note that a single character doesn't gain much
230      over the existing "required byte" (reqbyte) feature that just saves one      over the existing "required byte" (reqbyte) feature that just remembers one
231      byte.      data unit.
232    
233    * These probably need to go in study():    * These probably need to go in pcre_study():
234    
235      o Remember an initial string rather than just 1 char?      o Remember an initial string rather than just 1 char?
236    
237      o A required byte from alternatives - not just the last char, but an      o A required data unit from alternatives - not just the last unit, but an
238        earlier one if common to all alternatives.        earlier one if common to all alternatives.
239    
     o Minimum length of subject needed.  
   
240      o Friedl contains other ideas.      o Friedl contains other ideas.
241    
242      * pcre_study() does not set initial byte flags for Unicode property types
243        such as \p; I don't know how much benefit there would be for, for example,
244        setting the bits for 0-9 and all bytes >= xC0 when a pattern starts with
245        \p{N}.
246    
247      * There is scope for more "auto-possessifying" in connection with \p and \P.
248    
249  . If Perl gets to a consistent state over the settings of capturing sub-  . If Perl gets to a consistent state over the settings of capturing sub-
250    patterns inside repeats, see if we can match it. One example of the    patterns inside repeats, see if we can match it. One example of the
251    difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE    difference is the matching of /(main(O)?)+/ against mainOmain, where PCRE
# Line 188  others are relatively new. Line 254  others are relatively new.
254    
255  . Perl 6 will be a revolution. Is it a revolution too far for PCRE?  . Perl 6 will be a revolution. Is it a revolution too far for PCRE?
256    
 . Unicode  
   
   * Note that in Perl, \s matches \pZ and similarly for \d, \w and the POSIX  
     character classes. For the moment, I've chosen not to support this for  
     backward compatibility, for speed, and because it would be messy to  
     implement.  
   
   * A different approach to Unicode might be to use a typedef to do everything  
     in unsigned shorts instead of unsigned chars. Actually, we'd have to have a  
     new typedef to distinguish data from bits of compiled pattern that are in  
     bytes, I think. There would need to be conversion functions in and out. I  
     don't think this is particularly trivial - and anyway, Unicode now has  
     characters that need more than 16 bits, so is this at all sensible?  
   
   * There has been a request for direct support of 16-bit characters and  
     UTF-16. However, since Unicode is moving beyond purely 16-bit characters,  
     is this worth it at all? One possible way of handling 16-bit characters  
     would be to "load" them in the same way that UTF-8 characters are loaded.  
   
257  . Allow errorptr and erroroffset to be NULL. I don't like this idea.  . Allow errorptr and erroroffset to be NULL. I don't like this idea.
258    
259  . Line endings:  . Line endings:
260    
261    * Option to use NUL as a line terminator in subject strings. This could now    * Option to use NUL as a line terminator in subject strings. This could now
262      be done relatively easily since the extension to support LF, CR, and CRLF.      be done relatively easily since the extension to support LF, CR, and CRLF.
263      If this is done, a suitable option for pcregrep is also required.      If it is done, a suitable option for pcregrep is also required.
264    
265  . Option to provide the pattern with a length instead of with a NUL terminator.  . Option to provide the pattern with a length instead of with a NUL terminator.
266    This probably affects quite a few places in the code.    This affects quite a few places in the code and is not trivial.
267    
268  . Catch SIGSEGV for stack overflows?  . Catch SIGSEGV for stack overflows?
269    
# Line 231  others are relatively new. Line 278  others are relatively new.
278    preceded by a blank line, instead of adding it to every matched line, and (b)    preceded by a blank line, instead of adding it to every matched line, and (b)
279    support --outputfile=name.    support --outputfile=name.
280    
281  . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 7.  . Consider making UTF-8 and UCP the default for PCRE n.0 for some n > 8.
282      (And now presumably UTF-16 and UCP for the 16-bit library.)
283    
284  . Add a user pointer to pcre_malloc/free functions -- some option would be  . Add a user pointer to pcre_malloc/free functions -- some option would be
285    needed to retain backward compatibility.    needed to retain backward compatibility.
# Line 246  others are relatively new. Line 294  others are relatively new.
294  . Wild thought: the ability to compile from PCRE's internal byte code to a real  . Wild thought: the ability to compile from PCRE's internal byte code to a real
295    FSM and a very fast (third) matcher to process the result. There would be    FSM and a very fast (third) matcher to process the result. There would be
296    even more restrictions than for pcre_dfa_exec(), however. This is not easy.    even more restrictions than for pcre_dfa_exec(), however. This is not easy.
297      This is probably obsolete now that we have the JIT support.
298    
299  . Should pcretest have some private locale data, to avoid relying on the  . Should pcretest have some private locale data, to avoid relying on the
300    available locales for the test data, since different OS have different ideas?    available locales for the test data, since different OS have different ideas?
# Line 256  others are relatively new. Line 305  others are relatively new.
305    
306  . Someone suggested --disable-callout to save code space when callouts are  . Someone suggested --disable-callout to save code space when callouts are
307    never wanted. This seems rather marginal.    never wanted. This seems rather marginal.
308    
309  . Check names that consist entirely of digits: PCRE allows, but do Perl and  . Check names that consist entirely of digits: PCRE allows, but do Perl and
310    Python, etc?    Python, etc?
311    
312    . A user suggested a parameter to limit the length of string matched, for
313      example if the parameter is N, the current match should fail if the matched
314      substring exceeds N. This could apply to both match functions. The value
315      could be a new field in the extra block.
316    
317    . Callouts with arguments: (?Cn:ARG) for instance.
318    
319    . A user is going to supply a patch to generalize the API for user-specific
320      memory allocation so that it is more flexible in threaded environments. This
321      was promised a long time ago, and never appeared. However, this is a live
322      issue not only for threaded environments, but for libraries that use PCRE and
323      want not to be beholden to their caller's memory allocation.
324    
325    . Write a wrapper to maintain a structure with specified runtime parameters,
326      such as recurse limit, and pass these to PCRE each time it is called. Also
327      maybe malloc and free. A user sent a prototype. This relates the the previous
328      item.
329    
330    . Write a function that generates random matching strings for a compiled regex.
331    
332    . Pcregrep: an option to specify the output line separator, either as a string
333      or select from a fixed list. This is not dead easy, because at the moment it
334      outputs whatever is in the input file.
335    
336    . Improve the code for duplicate checking in pcre_dfa_exec(). An incomplete,
337      non-thread-safe patch showed that this can help performance for patterns
338      where there are many alternatives. However, a simple thread-safe
339      implementation that I tried made things worse in many simple cases, so this
340      is not an obviously good thing.
341    
342    . Make the longest lookbehind available via pcre_fullinfo(). This is not
343      straightforward because lookbehinds can be nested inside lookbehinds. This
344      case will have to be identified, and the amounts added. This should then give
345      the maximum possible lookbehind length. The reason for wanting this is to
346      help when implementing multi-segment matching using pcre_exec() with partial
347      matching and overlapping segments.
348    
349    . PCRE cannot at present distinguish between subpatterns with different names,
350      but the same number (created by the use of ?|). In order to do so, a way of
351      remembering *which* subpattern numbered n matched is needed. Bugzilla #760.
352      Now that (*MARK) has been implemented, it can perhaps be used as a way round
353      this problem.
354    
355    . Instead of having #ifdef HAVE_CONFIG_H in each module, put #include
356      "something" and the the #ifdef appears only in one place, in "something".
357    
358  Philip Hazel  Philip Hazel
359  Email local part: ph10  Email local part: ph10
360  Email domain: cam.ac.uk  Email domain: cam.ac.uk
361  Last updated: 04 July 2008  Last updated: 20 September 2012

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