3 Pumpkin - Notes on handling the Perl Patch Pumpkin And Porting Perl
7 There is no simple synopsis, yet.
11 This document attempts to begin to describe some of the considerations
12 involved in patching, porting, and maintaining perl.
14 This document is still under construction, and still subject to
15 significant changes. Still, I hope parts of it will be useful,
16 so I'm releasing it even though it's not done.
18 For the most part, it's a collection of anecdotal information that
19 already assumes some familiarity with the Perl sources. I really need
20 an introductory section that describes the organization of the sources
21 and all the various auxiliary files that are part of the distribution.
23 =head1 Where Do I Get Perl Sources and Related Material?
25 The Comprehensive Perl Archive Network (or CPAN) is the place to go.
26 There are many mirrors, but the easiest thing to use is probably
27 http://www.cpan.org/README.html , which automatically points you to a
28 mirror site "close" to you.
30 =head2 Perl5-porters mailing list
32 The mailing list perl5-porters@perl.org
33 is the main group working with the development of perl. If you're
34 interested in all the latest developments, you should definitely
35 subscribe. The list is high volume, but generally has a
36 fairly low noise level.
38 Subscribe by sending the message (in the body of your letter)
40 subscribe perl5-porters
42 to perl5-porters-request@perl.org .
44 Archives of the list are held at:
46 http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/
48 =head1 How are Perl Releases Numbered?
50 Beginning with v5.6.0, even versions will stand for maintenance releases
51 and odd versions for development releases, i.e., v5.6.x for maintenance
52 releases, and v5.7.x for development releases. Before v5.6.0, subversions
53 _01 through _49 were reserved for bug-fix maintenance releases, and
54 subversions _50 through _99 for unstable development versions.
56 For example, in v5.6.1, the revision number is 5, the version is 6,
57 and 1 is the subversion.
59 For compatibility with the older numbering scheme the composite floating
60 point version number continues to be available as the magic variable $],
61 and amounts to C<$revision + $version/1000 + $subversion/100000>. This
62 can still be used in comparisons.
64 print "You've got an old perl\n" if $] < 5.005_03;
66 In addition, the version is also available as a string in $^V.
68 print "You've got a new perl\n" if $^V and $^V ge v5.6.0;
70 You can also require particular version (or later) with:
74 or using the new syntax available only from v5.6 onward:
78 At some point in the future, we may need to decide what to call the
79 next big revision. In the .package file used by metaconfig to
80 generate Configure, there are two variables that might be relevant:
81 $baserev=5 and $package=perl5.
83 Perl releases produced by the members of perl5-porters are usually
84 available on CPAN in the F<src/5.0/maint> and F<src/5.0/devel>
87 =head2 Maintenance and Development Subversions
89 The first rule of maintenance work is "First, do no harm."
91 Trial releases of bug-fix maintenance releases are announced on
92 perl5-porters. Trial releases use the new subversion number (to avoid
93 testers installing it over the previous release) and include a 'local
94 patch' entry in patchlevel.h. The distribution file contains the
95 string C<MAINT_TRIAL> to make clear that the file is not meant for
98 In general, the names of official distribution files for the public
99 always match the regular expression:
101 ^perl\d+\.(\d+)\.\d+(-MAINT_TRIAL_\d+)\.tar\.gz$
103 C<$1> in the pattern is always an even number for maintenance
104 versions, and odd for developer releases.
106 In the past it has been observed that pumpkings tend to invent new
107 naming conventions on the fly. If you are a pumpking, before you
108 invent a new name for any of the three types of perl distributions,
109 please inform the guys from the CPAN who are doing indexing and
110 provide the trees of symlinks and the like. They will have to know
111 I<in advance> what you decide.
113 =head2 Why is it called the patch pumpkin?
115 Chip Salzenberg gets credit for that, with a nod to his cow orker,
116 David Croy. We had passed around various names (baton, token, hot
117 potato) but none caught on. Then, Chip asked:
121 Who has the patch pumpkin?
123 To explain: David Croy once told me once that at a previous job,
124 there was one tape drive and multiple systems that used it for backups.
125 But instead of some high-tech exclusion software, they used a low-tech
126 method to prevent multiple simultaneous backups: a stuffed pumpkin.
127 No one was allowed to make backups unless they had the "backup pumpkin".
133 =head1 Philosophical Issues in Patching and Porting Perl
135 There are no absolute rules, but there are some general guidelines I
136 have tried to follow as I apply patches to the perl sources.
137 (This section is still under construction.)
139 =head2 Solve problems as generally as possible
141 Never implement a specific restricted solution to a problem when you
142 can solve the same problem in a more general, flexible way.
144 For example, for dynamic loading to work on some SVR4 systems, we had
145 to build a shared libperl.so library. In order to build "FAT" binaries
146 on NeXT 4.0 systems, we had to build a special libperl library. Rather
147 than continuing to build a contorted nest of special cases, I
148 generalized the process of building libperl so that NeXT and SVR4 users
149 could still get their work done, but others could build a shared
150 libperl if they wanted to as well.
152 Contain your changes carefully. Assume nothing about other operating
153 systems, not even closely related ones. Your changes must not affect
156 Spy shamelessly on how similar patching or porting issues have been
159 If feasible, try to keep filenames 8.3-compliant to humor those poor
160 souls that get joy from running Perl under such dire limitations.
161 There's a script, check83.pl, for keeping your nose 8.3-clean.
162 In a similar vein, do not create files or directories which differ only
163 in case (upper versus lower).
165 =head2 Seek consensus on major changes
167 If you are making big changes, don't do it in secret. Discuss the
168 ideas in advance on perl5-porters.
170 =head2 Keep the documentation up-to-date
172 If your changes may affect how users use perl, then check to be sure
173 that the documentation is in sync with your changes. Be sure to
174 check all the files F<pod/*.pod> and also the F<INSTALL> document.
176 Consider writing the appropriate documentation first and then
177 implementing your change to correspond to the documentation.
179 =head2 Avoid machine-specific #ifdef's
181 To the extent reasonable, try to avoid machine-specific #ifdef's in
182 the sources. Instead, use feature-specific #ifdef's. The reason is
183 that the machine-specific #ifdef's may not be valid across major
184 releases of the operating system. Further, the feature-specific tests
185 may help out folks on another platform who have the same problem.
187 =head2 Machine-specific files
193 If you have many machine-specific #defines or #includes, consider
194 creating an "osish.h" (os2ish.h, vmsish.h, and so on) and including
195 that in perl.h. If you have several machine-specific files (function
196 emulations, function stubs, build utility wrappers) you may create a
197 separate subdirectory (djgpp, win32) and put the files in there.
198 Remember to update C<MANIFEST> when you add files.
200 If your system supports dynamic loading but none of the existing
201 methods at F<ext/DynaLoader/dl_*.xs> work for you, you must write
202 a new one. Study the existing ones to see what kind of interface
207 There are two kinds of hints: hints for building Perl and hints for
208 extensions. The former live in the C<hints> subdirectory, the latter
209 in C<ext/*/hints> subdirectories.
211 The top level hints are Bourne-shell scripts that set, modify and
212 unset appropriate Configure variables, based on the Configure command
213 line options and possibly existing config.sh and Policy.sh files from
214 previous Configure runs.
216 The extension hints are written in Perl (by the time they are used
217 miniperl has been built) and control the building of their respective
218 extensions. They can be used to for example manipulate compilation
221 =item build and installation Makefiles, scripts, and so forth
223 Sometimes you will also need to tweak the Perl build and installation
224 procedure itself, like for example F<Makefile.SH> and F<installperl>.
225 Tread very carefully, even more than usual. Contain your changes
230 Many of the tests in C<t> subdirectory assume machine-specific things
231 like existence of certain functions, something about filesystem
232 semantics, certain external utilities and their error messages. Use
233 the C<$^O> and the C<Config> module (which contains the results of the
234 Configure run, in effect the C<config.sh> converted to Perl) to either
235 skip (preferably not) or customize (preferable) the tests for your
240 Certain standard modules may need updating if your operating system
241 sports for example a native filesystem naming. You may want to update
242 some or all of the modules File::Basename, File::Spec, File::Path, and
243 File::Copy to become aware of your native filesystem syntax and
246 Remember to have a $VERSION in the modules. You can use the
247 Porting/checkVERSION.pl script for checking this.
251 If your operating system comes from outside UNIX you almost certainly
252 will have differences in the available operating system functionality
253 (missing system calls, different semantics, whatever). Please
254 document these at F<pod/perlport.pod>. If your operating system is
255 the first B<not> to have a system call also update the list of
256 "portability-bewares" at the beginning of F<pod/perlfunc.pod>.
258 A file called F<README.youros> at the top level that explains things
259 like how to install perl at this platform, where to get any possibly
260 required additional software, and for example what test suite errors
261 to expect, is nice too. Such files are in the process of being written
262 in pod format and will eventually be renamed F<INSTALL.youros>.
264 You may also want to write a separate F<.pod> file for your operating
265 system to tell about existing mailing lists, os-specific modules,
266 documentation, whatever. Please name these along the lines of
267 F<perl>I<youros>.pod. [unfinished: where to put this file (the pod/
268 subdirectory, of course: but more importantly, which/what index files
273 =head2 Allow for lots of testing
275 We should never release a main version without testing it as a
278 =head2 Test popular applications and modules.
280 We should never release a main version without testing whether or not
281 it breaks various popular modules and applications. A partial list of
282 such things would include majordomo, metaconfig, apache, Tk, CGI,
283 libnet, and libwww, to name just a few. Of course it's quite possible
284 that some of those things will be just plain broken and need to be fixed,
285 but, in general, we ought to try to avoid breaking widely-installed
288 =head2 Automated generation of derivative files
290 The F<embed.h>, F<keywords.h>, F<opcode.h>, and F<perltoc.pod> files
291 are all automatically generated by perl scripts. In general, don't
292 patch these directly; patch the data files instead.
294 F<Configure> and F<config_h.SH> are also automatically generated by
295 B<metaconfig>. In general, you should patch the metaconfig units
296 instead of patching these files directly. However, very minor changes
297 to F<Configure> may be made in between major sync-ups with the
298 metaconfig units, which tends to be complicated operations. But be
299 careful, this can quickly spiral out of control. Running metaconfig
302 Also F<Makefile> is automatically produced from F<Makefile.SH>.
303 In general, look out for all F<*.SH> files.
305 Finally, the sample files in the F<Porting/> subdirectory are
306 generated automatically by the script F<U/mksample> included
307 with the metaconfig units. See L<"run metaconfig"> below for
308 information on obtaining the metaconfig units.
310 =head1 How to Make a Distribution
312 There really ought to be a 'make dist' target, but there isn't.
313 The 'dist' suite of tools also contains a number of tools that I haven't
314 learned how to use yet. Some of them may make this all a bit easier.
316 Here are the steps I go through to prepare a patch & distribution.
318 Lots of it could doubtless be automated but isn't. The Porting/makerel
319 (make release) perl script does now help automate some parts of it.
321 =head2 Announce your intentions
323 First, you should volunteer out loud to take the patch pumpkin. It's
324 generally counter-productive to have multiple people working in secret
327 At the same time, announce what you plan to do with the patch pumpkin,
328 to allow folks a chance to object or suggest alternatives, or do it for
329 you. Naturally, the patch pumpkin holder ought to incorporate various
330 bug fixes and documentation improvements that are posted while he or
331 she has the pumpkin, but there might also be larger issues at stake.
333 One of the precepts of the subversion idea is that we shouldn't give
334 the patch pumpkin to anyone unless we have some idea what he or she
335 is going to do with it.
337 =head2 refresh pod/perltoc.pod
339 Presumably, you have done a full C<make> in your working source
340 directory. Before you C<make spotless> (if you do), and if you have
341 changed any documentation in any module or pod file, change to the
342 F<pod> directory and run C<make toc>.
344 =head2 run installhtml to check the validity of the pod files
346 =head2 update patchlevel.h
348 Don't be shy about using the subversion number, even for a relatively
349 modest patch. We've never even come close to using all 99 subversions,
350 and it's better to have a distinctive number for your patch. If you
351 need feedback on your patch, go ahead and issue it and promise to
352 incorporate that feedback quickly (e.g. within 1 week) and send out a
355 If you update the subversion number, you may need to change the version
356 number near the top of the F<Changes> file.
358 =head2 run metaconfig
360 If you need to make changes to Configure or config_h.SH, it may be best to
361 change the appropriate metaconfig units instead, and regenerate Configure.
365 will regenerate Configure and config_h.SH. Much more information
366 on obtaining and running metaconfig is in the F<U/README> file
367 that comes with Perl's metaconfig units.
369 Since metaconfig is hard to change, running correction scripts after
370 this generation is sometimes needed. Configure gained complexity over
371 time, and the order in which config_h.SH is generated can cause havoc
372 when compiling perl. Therefor, you need to run Porting/config_h.pl
373 after that generation. All that and more is described in the README
374 files that come with the metaunits.
376 Perl's metaconfig units should be available on CPAN. A set of units
377 that will work with perl5.9.x is in a file with a name similar to
378 F<mc_units-20070423.tgz> under http://www.cpan.org/authors/id/H/HM/HMBRAND/ .
379 The mc_units tar file should be unpacked in your main perl source directory.
380 Note: those units were for use with 5.9.x. There may have been changes since
381 then. Check for later versions or contact perl5-porters@perl.org to obtain a
382 pointer to the current version.
384 Alternatively, do consider if the F<*ish.h> files or the hint files might be
385 a better place for your changes.
389 Make sure the MANIFEST is up-to-date. You can use dist's B<manicheck>
390 program for this. You can also use
392 perl -w -MExtUtils::Manifest=fullcheck -e fullcheck
394 Both commands will also list extra files in the directory that are not
397 The MANIFEST is normally sorted.
399 If you are using metaconfig to regenerate Configure, then you should note
400 that metaconfig actually uses MANIFEST.new, so you want to be sure
401 MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new
402 distinction particularly useful, but that's probably because I still haven't
403 learned how to use the full suite of tools in the dist distribution.
405 =head2 Check permissions
407 All the tests in the t/ directory ought to be executable. The
408 main makefile used to do a 'chmod t/*/*.t', but that resulted in
409 a self-modifying distribution--something some users would strongly
410 prefer to avoid. The F<t/TEST> script will check for this
411 and do the chmod if needed, but the tests still ought to be
414 In all, the following files should probably be executable:
428 vms/ext/Stdio/test.pl
432 Other things ought to be readable, at least :-).
434 Probably, the permissions for the files could be encoded in MANIFEST
435 somehow, but I'm reluctant to change MANIFEST itself because that
436 could break old scripts that use MANIFEST.
438 I seem to recall that some SVR3 systems kept some sort of file that listed
439 permissions for system files; something like that might be appropriate.
443 This will build a config.sh and config.h. You can skip this if you haven't
444 changed Configure or config_h.SH at all. I use the following command
446 sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \
448 -Dcf_email='yourname@yourhost.yourplace.com' \
449 -Dperladmin='yourname@yourhost.yourplace.com' \
450 -Dmydomain='.yourplace.com' \
451 -Dmyhostname='yourhost' \
454 =head2 Update Porting/config.sh and Porting/config_H
457 This section needs revision. We're currently working on easing
458 the task of keeping the vms, win32, and plan9 config.sh info
459 up-to-date. The plan is to use keep up-to-date 'canned' config.sh
460 files in the appropriate subdirectories and then generate 'canned'
461 config.h files for vms, win32, etc. from the generic config.sh file.
462 This is to ease maintenance. When Configure gets updated, the parts
463 sometimes get scrambled around, and the changes in config_H can
464 sometimes be very hard to follow. config.sh, on the other hand, can
465 safely be sorted, so it's easy to track (typically very small) changes
466 to config.sh and then propagate them to a canned 'config.h' by any
467 number of means, including a perl script in win32/ or carrying
468 config.sh and config_h.SH to a Unix system and running sh
469 config_h.SH.) Vms uses configure.com to generate its own config.sh
470 and config.h. If you want to add a new variable to config.sh check
471 with vms folk how to add it to configure.com too.
474 The Porting/config.sh and Porting/config_H files are provided to
475 help those folks who can't run Configure. It is important to keep
476 them up-to-date. If you have changed config_h.SH, those changes must
477 be reflected in config_H as well. (The name config_H was chosen to
478 distinguish the file from config.h even on case-insensitive file systems.)
479 Simply edit the existing config_H file; keep the first few explanatory
480 lines and then copy your new config.h below.
482 It may also be necessary to update win32/config.?c, and
483 plan9/config.plan9, though you should be quite careful in doing so if
484 you are not familiar with those systems. You might want to issue your
485 patch with a promise to quickly issue a follow-up that handles those
488 =head2 make regen_perly
490 If perly.y has been edited, it is necessary to run this target to rebuild
491 perly.h, perly.act and perly.tab. In fact this target just runs the Perl
492 script regen_perly.pl. Note that perly.c is I<not> rebuilt; this is just a
493 plain static file now.
495 This target relies on you having Bison installed on your system. Running
496 the target will tell you if you haven't got the right version, and if so,
497 where to get the right one. Or if you prefer, you could hack
498 regen_perly.pl to work with your version of Bison. The important things
499 are that the regexes can still extract out the right chunks of the Bison
500 output into perly.act and perly.tab, and that the contents of those two
501 files, plus perly.h, are functionally equivalent to those produced by the
502 supported version of Bison.
504 Note that in the old days, you had to do C<make run_byacc> instead.
506 =head2 make regen_all
508 This target takes care of the regen_headers target.
509 (It used to also call the regen_pods target, but that has been eliminated.)
511 =head2 make regen_headers
513 The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically
514 generated by perl scripts. Since the user isn't guaranteed to have a
515 working perl, we can't require the user to generate them. Hence you have
516 to, if you're making a distribution.
518 I used to include rules like the following in the makefile:
520 # The following three header files are generated automatically
521 # The correct versions should be already supplied with the perl kit,
522 # in case you don't have perl or 'sh' available.
523 # The - is to ignore error return codes in case you have the source
524 # installed read-only or you don't have perl yet.
525 keywords.h: keywords.pl
526 @echo "Don't worry if this fails."
530 However, I got B<lots> of mail consisting of people worrying because the
531 command failed. I eventually decided that I would save myself time
532 and effort by manually running C<make regen_headers> myself rather
533 than answering all the questions and complaints about the failing
536 =head2 global.sym, interp.sym and perlio.sym
538 Make sure these files are up-to-date. Read the comments in these
539 files and in perl_exp.SH to see what to do.
541 =head2 Binary compatibility
543 If you do change F<global.sym> or F<interp.sym>, think carefully about
544 what you are doing. To the extent reasonable, we'd like to maintain
545 source and binary compatibility with older releases of perl. That way,
546 extensions built under one version of perl will continue to work with
547 new versions of perl.
549 Of course, some incompatible changes may well be necessary. I'm just
550 suggesting that we not make any such changes without thinking carefully
551 about them first. If possible, we should provide
552 backwards-compatibility stubs. There's a lot of XS code out there.
553 Let's not force people to keep changing it.
557 F<ext/Devel-PPPort/PPPort.pm> needs to be synchronized to include all
558 new macros added to .h files (normally perl.h and XSUB.h, but others
559 as well). Since chances are that when a new macro is added the
560 committer will forget to update F<PPPort.pm>, it's the best to diff for
561 changes in .h files when making a new release and making sure that
562 F<PPPort.pm> contains them all.
564 The pumpking can delegate the synchronization responsibility to anybody
565 else, but the release process is the only place where we can make sure
566 that no new macros fell through the cracks.
570 Be sure to update the F<Changes> file. Try to include both an overall
571 summary as well as detailed descriptions of the changes. Your
572 audience will include other developers and users, so describe
573 user-visible changes (if any) in terms they will understand, not in
574 code like "initialize foo variable in bar function".
576 There are differing opinions on whether the detailed descriptions
577 ought to go in the Changes file or whether they ought to be available
578 separately in the patch file (or both). There is no disagreement that
579 detailed descriptions ought to be easily available somewhere.
581 If you update the subversion number in F<patchlevel.h>, you may need
582 to change the version number near the top of the F<Changes> file.
584 =head2 Bumping perl's version
586 If you bump perl's version, you will need to update a few things:
587 the L<perlhist> manpage for the date of release, the version number and
588 perldelta reference in the top level F<README> (and maybe the copyright
589 year too), the F<META.yml> file (generated via F<Porting/makemeta>, be
590 sure to run it with the current bleadperl), and the meta-info about
591 dual-lived modules in Module::Corelist (F<Porting/corelist.pl> does that).
592 Make sure the numbered feature bundles in F<lib/feature.pm> are also
597 The F<pod/perltodo.pod> file contains a roughly-categorized unordered
598 list of aspects of Perl that could use enhancement, features that could
599 be added, areas that could be cleaned up, and so on. During your term
600 as pumpkin-holder, you will probably address some of these issues, and
601 perhaps identify others which, while you decide not to address them this
602 time around, may be tackled in the future. Update the file to reflect
603 the situation as it stands when you hand over the pumpkin.
605 You might like, early in your pumpkin-holding career, to see if you
606 can find champions for particular issues on the to-do list: an issue
607 owned is an issue more likely to be resolved.
609 There are also some more porting-specific L</Todo> items later in this
612 =head2 OS/2-specific updates
614 In the os2 directory is F<diff.configure>, a set of OS/2-specific
615 diffs against B<Configure>. If you make changes to Configure, you may
616 want to consider regenerating this diff file to save trouble for the
619 You can also consider the OS/2 diffs as reminders of portability
620 things that need to be fixed in Configure.
622 =head2 VMS-specific updates
624 The Perl revision number appears as "perl5" in configure.com.
625 It is courteous to update that if necessary.
627 =head2 Making the new distribution
629 Suppose, for example, that you want to make version 5.004_08. Then you can
630 do something like the following
632 mkdir ../perl5.004_08
633 awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08
635 tar cf perl5.004_08.tar perl5.004_08
636 gzip --best perl5.004_08.tar
638 These steps, with extra checks, are automated by the Porting/makerel
641 =head2 Making a new patch
643 I find the F<makepatch> utility quite handy for making patches.
644 You can obtain it from any CPAN archive under
645 http://www.cpan.org/authors/Johan_Vromans/ . There are a couple
646 of differences between my version and the standard one. I have mine do
649 # Print a reassuring "End of Patch" note so people won't
650 # wonder if their mailer truncated patches.
651 print "\n\nEnd of Patch.\n";
653 at the end. That's because I used to get questions from people asking
654 if their mail was truncated.
656 It also writes Index: lines which include the new directory prefix
657 (change Index: print, approx line 294 or 310 depending on the version,
658 to read: print PATCH ("Index: $newdir$new\n");). That helps patches
659 work with more POSIX conformant patch programs.
661 Here's how I generate a new patch. I'll use the hypothetical
662 5.004_07 to 5.004_08 patch as an example.
664 # unpack perl5.004_07/
665 gzip -d -c perl5.004_07.tar.gz | tar -xof -
666 # unpack perl5.004_08/
667 gzip -d -c perl5.004_08.tar.gz | tar -xof -
668 makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat
670 Makepatch will automatically generate appropriate B<rm> commands to remove
671 deleted files. Unfortunately, it will not correctly set permissions
672 for newly created files, so you may have to do so manually. For example,
673 patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable,
674 so at the top of the patch, I inserted the following lines:
680 Now, of course, my patch is now wrong because makepatch didn't know I
681 was going to do that command, and it patched against /dev/null.
683 So, what I do is sort out all such shell commands that need to be in the
684 patch (including possible mv-ing of files, if needed) and put that in the
685 shell commands at the top of the patch. Next, I delete all the patch parts
686 of perl5.004_08.pat, leaving just the shell commands. Then, I do the
690 sh ../perl5.004_08.pat
692 makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat
694 (Note the append to preserve my shell commands.)
695 Now, my patch will line up with what the end users are going to do.
697 =head2 Testing your patch
699 It seems obvious, but be sure to test your patch. That is, verify that
700 it produces exactly the same thing as your full distribution.
703 gzip -d -c perl5.004_07.tar.gz | tar -xf -
705 sh ../perl5.004_08.pat
706 patch -p1 -N < ../perl5.004_08.pat
708 gdiff -r perl5.004_07 perl5.004_08
710 where B<gdiff> is GNU diff. Other diff's may also do recursive checking.
714 Again, it's obvious, but you should test your new version as widely as you
715 can. You can be sure you'll hear about it quickly if your version doesn't
716 work on both ANSI and pre-ANSI compilers, and on common systems such as
717 SunOS 4.1.[34], Solaris, and Linux.
719 If your changes include conditional code, try to test the different
720 branches as thoroughly as you can. For example, if your system
721 supports dynamic loading, you can also test static loading with
725 You can also hand-tweak your config.h to try out different #ifdef
732 =item gcc -ansi -pedantic
734 Configure -Dgccansipedantic [ -Dcc=gcc ] will enable (via the cflags script,
735 not $Config{ccflags}) the gcc strict ANSI C flags -ansi and -pedantic for
736 the compilation of the core files on platforms where it knows it can
737 do so (like Linux, see cflags.SH for the full list), and on some
738 platforms only one (Solaris can do only -pedantic, not -ansi).
739 The flag -DPERL_GCC_PEDANTIC also gets added, since gcc does not add
740 any internal cpp flag to signify that -pedantic is being used, as it
741 does for -ansi (__STRICT_ANSI__).
743 Note that the -ansi and -pedantic are enabled only for version 3 (and
744 later) of gcc, since even gcc version 2.95.4 finds lots of seemingly
745 false "value computed not used" errors from Perl.
747 The -ansi and -pedantic are useful in catching at least the following
748 nonportable practices:
754 gcc-specific extensions
770 The -Dgccansipedantic should be used only when cleaning up the code,
771 not for production builds, since otherwise gcc cannot inline certain
776 =head1 Running Purify
778 Purify is a commercial tool that is helpful in identifying memory
779 overruns, wild pointers, memory leaks and other such badness. Perl
780 must be compiled in a specific way for optimal testing with Purify.
782 Use the following commands to test perl with Purify:
784 sh Configure -des -Doptimize=-g -Uusemymalloc -Dusemultiplicity \
786 setenv PURIFYOPTIONS "-chain-length=25"
789 ln -s ../pureperl perl
790 setenv PERL_DESTRUCT_LEVEL 2
793 Disabling Perl's malloc allows Purify to monitor allocations and leaks
794 more closely; using Perl's malloc will make Purify report most leaks
795 in the "potential" leaks category. Enabling the multiplicity option
796 allows perl to clean up thoroughly when the interpreter shuts down, which
797 reduces the number of bogus leak reports from Purify. The -DPURIFY
798 enables any Purify-specific debugging code in the sources.
800 Purify outputs messages in "Viewer" windows by default. If you don't have
801 a windowing environment or if you simply want the Purify output to
802 unobtrusively go to a log file instead of to the interactive window,
803 use the following options instead:
805 setenv PURIFYOPTIONS "-chain-length=25 -windows=no -log-file=perl.log \
808 The only currently known leaks happen when there are compile-time errors
809 within eval or require. (Fixing these is non-trivial, unfortunately, but
810 they must be fixed eventually.)
812 =head1 Common Gotchas
816 =item Probably Prefer POSIX
818 It's often the case that you'll need to choose whether to do
819 something the BSD-ish way or the POSIX-ish way. It's usually not
820 a big problem when the two systems use different names for similar
821 functions, such as memcmp() and bcmp(). The perl.h header file
822 handles these by appropriate #defines, selecting the POSIX mem*()
823 functions if available, but falling back on the b*() functions, if
826 More serious is the case where some brilliant person decided to
827 use the same function name but give it a different meaning or
828 calling sequence :-). getpgrp() and setpgrp() come to mind.
829 These are a real problem on systems that aim for conformance to
830 one standard (e.g. POSIX), but still try to support the other way
831 of doing things (e.g. BSD). My general advice (still not really
832 implemented in the source) is to do something like the following.
833 Suppose there are two alternative versions, fooPOSIX() and
837 /* use fooPOSIX(); */
840 /* try to emulate fooPOSIX() with fooBSD();
841 perhaps with the following: */
842 # define fooPOSIX fooBSD
844 # /* Uh, oh. We have to supply our own. */
845 # define fooPOSIX Perl_fooPOSIX
849 =item Think positively
851 If you need to add an #ifdef test, it is usually easier to follow if you
852 think positively, e.g.
854 #ifdef HAS_NEATO_FEATURE
855 /* use neato feature */
857 /* use some fallback mechanism */
860 rather than the more impenetrable
862 #ifndef MISSING_NEATO_FEATURE
863 /* Not missing it, so we must have it, so use it */
865 /* Are missing it, so fall back on something else. */
868 Of course for this toy example, there's not much difference. But when
869 the #ifdef's start spanning a couple of screen fulls, and the #else's
870 are marked something like
872 #else /* !MISSING_NEATO_FEATURE */
874 I find it easy to get lost.
876 =item Providing Missing Functions -- Problem
878 Not all systems have all the neat functions you might want or need, so
879 you might decide to be helpful and provide an emulation. This is
880 sound in theory and very kind of you, but please be careful about what
881 you name the function. Let me use the C<pause()> function as an
884 Perl5.003 has the following in F<perl.h>
887 #define pause() sleep((32767<<16)+32767)
890 Configure sets HAS_PAUSE if the system has the pause() function, so
891 this #define only kicks in if the pause() function is missing.
894 Unfortunately, some systems apparently have a prototype for pause()
895 in F<unistd.h>, but don't actually have the function in the library.
896 (Or maybe they do have it in a library we're not using.)
898 Thus, the compiler sees something like
900 extern int pause(void);
902 #define pause() sleep((32767<<16)+32767)
904 and dies with an error message. (Some compilers don't mind this;
905 others apparently do.)
907 To work around this, 5.003_03 and later have the following in perl.h:
909 /* Some unistd.h's give a prototype for pause() even though
910 HAS_PAUSE ends up undefined. This causes the #define
911 below to be rejected by the compiler. Sigh.
916 # define Pause() sleep((32767<<16)+32767)
921 The curious reader may wonder why I didn't do the following in
927 sleep((32767<<16)+32767);
931 That is, since the function is missing, just provide it.
932 Then things would probably be been alright, it would seem.
934 Well, almost. It could be made to work. The problem arises from the
935 conflicting needs of dynamic loading and namespace protection.
937 For dynamic loading to work on AIX (and VMS) we need to provide a list
938 of symbols to be exported. This is done by the script F<perl_exp.SH>,
939 which reads F<global.sym> and F<interp.sym>. Thus, the C<pause>
940 symbol would have to be added to F<global.sym> So far, so good.
942 On the other hand, one of the goals of Perl5 is to make it easy to
943 either extend or embed perl and link it with other libraries. This
944 means we have to be careful to keep the visible namespace "clean".
945 That is, we don't want perl's global variables to conflict with
946 those in the other application library. Although this work is still
947 in progress, the way it is currently done is via the F<embed.h> file.
948 This file is built from the F<global.sym> and F<interp.sym> files,
949 since those files already list the globally visible symbols. If we
950 had added C<pause> to global.sym, then F<embed.h> would contain the
953 #define pause Perl_pause
955 and calls to C<pause> in the perl sources would now point to
956 C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable,
957 it will go looking for C<perl_pause>, which probably won't exist in any
958 of the standard libraries. Thus the build of perl will fail.
960 Those systems where C<HAS_PAUSE> is not defined would be ok, however,
961 since they would get a C<Perl_pause> function in util.c. The rest of
962 the world would be in trouble.
964 And yes, this scenario has happened. On SCO, the function C<chsize>
965 is available. (I think it's in F<-lx>, the Xenix compatibility
966 library.) Since the perl4 days (and possibly before), Perl has
967 included a C<chsize> function that gets called something akin to
970 I32 chsize(fd, length)
976 #define chsize Perl_chsize
978 to F<embed.h>, the compile started failing on SCO systems.
980 The "fix" is to give the function a different name. The one
981 implemented in 5.003_05 isn't optimal, but here's what was done:
984 # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */
987 # define my_chsize chsize
990 My explanatory comment in patch 5.003_05 said:
992 Undef and then re-define my_chsize from Perl_my_chsize to
993 just plain chsize if this system HAS_CHSIZE. This probably only
994 applies to SCO. This shows the perils of having internal
995 functions with the same name as external library functions :-).
997 Now, we can safely put C<my_chsize> in F<global.sym>, export it, and
998 hide it with F<embed.h>.
1000 To be consistent with what I did for C<pause>, I probably should have
1001 called the new function C<Chsize>, rather than C<my_chsize>.
1002 However, the perl sources are quite inconsistent on this (Consider
1003 New, Mymalloc, and Myremalloc, to name just a few.)
1005 There is a problem with this fix, however, in that C<Perl_chsize>
1006 was available as a F<libperl.a> library function in 5.003, but it
1007 isn't available any more (as of 5.003_07). This means that we've
1008 broken binary compatibility. This is not good.
1010 =item Providing missing functions -- some ideas
1012 We currently don't have a standard way of handling such missing
1013 function names. Right now, I'm effectively thinking aloud about a
1014 solution. Some day, I'll try to formally propose a solution.
1016 Part of the problem is that we want to have some functions listed as
1017 exported but not have their names mangled by embed.h or possibly
1018 conflict with names in standard system headers. We actually already
1019 have such a list at the end of F<perl_exp.SH> (though that list is
1022 # extra globals not included above.
1023 cat <<END >> perl.exp
1047 This still needs much thought, but I'm inclined to think that one
1048 possible solution is to prefix all such functions with C<perl_> in the
1049 source and list them along with the other C<perl_*> functions in
1052 Thus, for C<chsize>, we'd do something like the following:
1056 # define perl_chsize chsize
1059 then in some file (e.g. F<util.c> or F<doio.c>) do
1062 I32 perl_chsize(fd, length)
1063 /* implement the function here . . . */
1066 Alternatively, we could just always use C<chsize> everywhere and move
1067 C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would
1068 probably be fine as long as our C<chsize> function agreed with all the
1069 C<chsize> function prototypes in the various systems we'll be using.
1070 As long as the prototypes in actual use don't vary that much, this is
1071 probably a good alternative. (As a counter-example, note how Configure
1072 and perl have to go through hoops to find and use get Malloc_t and
1073 Free_t for C<malloc> and C<free>.)
1075 At the moment, this latter option is what I tend to prefer.
1077 =item All the world's a VAX
1079 Sorry, showing my age:-). Still, all the world is not BSD 4.[34],
1080 SVR4, or POSIX. Be aware that SVR3-derived systems are still quite
1081 common (do you have any idea how many systems run SCO?) If you don't
1082 have a bunch of v7 manuals handy, the metaconfig units (by default
1083 installed in F</usr/local/lib/dist/U>) are a good resource to look at
1088 =head1 Miscellaneous Topics
1092 Why does perl use a metaconfig-generated Configure script instead of an
1093 autoconf-generated configure script?
1095 Metaconfig and autoconf are two tools with very similar purposes.
1096 Metaconfig is actually the older of the two, and was originally written
1097 by Larry Wall, while autoconf is probably now used in a wider variety of
1098 packages. The autoconf info file discusses the history of autoconf and
1099 how it came to be. The curious reader is referred there for further
1102 Overall, both tools are quite good, I think, and the choice of which one
1103 to use could be argued either way. In March, 1994, when I was just
1104 starting to work on Configure support for Perl5, I considered both
1105 autoconf and metaconfig, and eventually decided to use metaconfig for the
1110 =item Compatibility with Perl4
1112 Perl4 used metaconfig, so many of the #ifdef's were already set up for
1113 metaconfig. Of course metaconfig had evolved some since Perl4's days,
1114 but not so much that it posed any serious problems.
1116 =item Metaconfig worked for me
1118 My system at the time was Interactive 2.2, an SVR3.2/386 derivative that
1119 also had some POSIX support. Metaconfig-generated Configure scripts
1120 worked fine for me on that system. On the other hand, autoconf-generated
1121 scripts usually didn't. (They did come quite close, though, in some
1122 cases.) At the time, I actually fetched a large number of GNU packages
1123 and checked. Not a single one configured and compiled correctly
1124 out-of-the-box with the system's cc compiler.
1126 =item Configure can be interactive
1128 With both autoconf and metaconfig, if the script works, everything is
1129 fine. However, one of my main problems with autoconf-generated scripts
1130 was that if it guessed wrong about something, it could be B<very> hard to
1131 go back and fix it. For example, autoconf always insisted on passing the
1132 -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I
1133 wanted or needed for that package. There was no way short of editing the
1134 configure script to turn this off. You couldn't just edit the resulting
1135 Makefile at the end because the -Xp flag influenced a number of other
1138 Metaconfig's Configure scripts, on the other hand, can be interactive.
1139 Thus if Configure is guessing things incorrectly, you can go back and fix
1140 them. This isn't as important now as it was when we were actively
1141 developing Configure support for new features such as dynamic loading,
1142 but it's still useful occasionally.
1146 At the time, autoconf-generated scripts were covered under the GNU Public
1147 License, and hence weren't suitable for inclusion with Perl, which has a
1148 different licensing policy. (Autoconf's licensing has since changed.)
1152 Metaconfig builds up Configure from a collection of discrete pieces
1153 called "units". You can override the standard behavior by supplying your
1154 own unit. With autoconf, you have to patch the standard files instead.
1155 I find the metaconfig "unit" method easier to work with. Others
1156 may find metaconfig's units clumsy to work with.
1160 =head2 Why isn't there a directory to override Perl's library?
1162 Mainly because no one's gotten around to making one. Note that
1163 "making one" involves changing perl.c, Configure, config_h.SH (and
1164 associated files, see above), and I<documenting> it all in the
1167 Apparently, most folks who want to override one of the standard library
1168 files simply do it by overwriting the standard library files.
1172 In the perl.c sources, you'll find an undocumented APPLLIB_EXP
1173 variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are
1174 documented in config_h.SH). Here's what APPLLIB_EXP is for, from
1175 a mail message from Larry:
1177 The main intent of APPLLIB_EXP is for folks who want to send out a
1178 version of Perl embedded in their product. They would set the symbol
1179 to be the name of the library containing the files needed to run or to
1180 support their particular application. This works at the "override"
1181 level to make sure they get their own versions of any library code that
1182 they absolutely must have configuration control over.
1184 As such, I don't see any conflict with a sysadmin using it for a
1185 override-ish sort of thing, when installing a generic Perl. It should
1186 probably have been named something to do with overriding though. Since
1187 it's undocumented we could still change it... :-)
1189 Given that it's already there, you can use it to override distribution modules.
1190 One way to do that is to add
1192 ccflags="$ccflags -DAPPLLIB_EXP=\"/my/override\""
1194 to your config.over file. (You have to be particularly careful to get the
1195 double quotes in. APPLLIB_EXP must be a valid C string. It might
1196 actually be easier to just #define it yourself in perl.c.)
1198 Then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB. Perl will
1199 also search architecture-specific and version-specific subdirectories of
1202 =head2 Shared libperl.so location
1204 Why isn't the shared libperl.so installed in /usr/lib/ along
1205 with "all the other" shared libraries? Instead, it is installed
1206 in $archlib, which is typically something like
1208 /usr/local/lib/perl5/archname/5.00404
1210 and is architecture- and version-specific.
1212 The basic reason why a shared libperl.so gets put in $archlib is so that
1213 you can have more than one version of perl on the system at the same time,
1214 and have each refer to its own libperl.so.
1216 Three examples might help. All of these work now; none would work if you
1217 put libperl.so in /usr/lib.
1223 Suppose you want to have both threaded and non-threaded perl versions
1224 around. Configure will name both perl libraries "libperl.so" (so that
1225 you can link to them with -lperl). The perl binaries tell them apart
1226 by having looking in the appropriate $archlib directories.
1230 Suppose you have perl5.004_04 installed and you want to try to compile
1231 it again, perhaps with different options or after applying a patch.
1232 If you already have libperl.so installed in /usr/lib/, then it may be
1233 either difficult or impossible to get ld.so to find the new libperl.so
1234 that you're trying to build. If, instead, libperl.so is tucked away in
1235 $archlib, then you can always just change $archlib in the current perl
1236 you're trying to build so that ld.so won't find your old libperl.so.
1237 (The INSTALL file suggests you do this when building a debugging perl.)
1241 The shared perl library is not a "well-behaved" shared library with
1242 proper major and minor version numbers, so you can't necessarily
1243 have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose
1244 perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05
1245 were to install /usr/lib/libperl.so.4.5. Now, when you try to run
1246 perl5.004_04, ld.so might try to load libperl.so.4.5, since it has
1247 the right "major version" number. If this works at all, it almost
1248 certainly defeats the reason for keeping perl5.004_04 around. Worse,
1249 with development subversions, you certaily can't guarantee that
1250 libperl.so.4.4 and libperl.so.4.55 will be compatible.
1252 Anyway, all this leads to quite obscure failures that are sure to drive
1253 casual users crazy. Even experienced users will get confused :-). Upon
1254 reflection, I'd say leave libperl.so in $archlib.
1258 =head2 Indentation style
1260 Over the years Perl has become a mishmash of
1261 various indentation styles, but the original "Larry style" can
1262 probably be restored with (GNU) indent somewhat like this:
1264 indent -kr -nce -psl -sc
1266 A more ambitious solution would also specify a list of Perl specific
1267 types with -TSV -TAV -THV .. -TMAGIC -TPerlIO ... but that list would
1268 be quite ungainly. Also note that GNU indent also doesn't do aligning
1269 of consecutive assignments, which would truly wreck the layout in
1270 places like sv.c:Perl_sv_upgrade() or sv.c:Perl_clone_using().
1271 Similarly nicely aligned &&s, ||s and ==s would not be respected.
1273 =head1 Upload Your Work to CPAN
1275 You can upload your work to CPAN if you have a CPAN id. Check out
1276 http://www.cpan.org/modules/04pause.html for information on
1277 _PAUSE_, the Perl Author's Upload Server.
1279 I typically upload both the patch file, e.g. F<perl5.004_08.pat.gz>
1280 and the full tar file, e.g. F<perl5.004_08.tar.gz>.
1282 If you want your patch to appear in the F<src/5.0/unsupported>
1283 directory on CPAN, send e-mail to the CPAN master librarian. (Check
1284 out http://www.cpan.org/CPAN.html ).
1286 =head1 Help Save the World
1288 You should definitely announce your patch on the perl5-porters list.
1289 You should also consider announcing your patch on
1290 comp.lang.perl.announce, though you should make it quite clear that a
1291 subversion is not a production release, and be prepared to deal with
1292 people who will not read your disclaimer.
1296 Here, in no particular order, are some Configure and build-related
1297 items that merit consideration. This list isn't exhaustive, it's just
1298 what I came up with off the top of my head.
1300 =head2 Adding missing library functions to Perl
1302 The perl Configure script automatically determines which headers and
1303 functions you have available on your system and arranges for them to be
1304 included in the compilation and linking process. Occasionally, when porting
1305 perl to an operating system for the first time, you may find that the
1306 operating system is missing a key function. While perl may still build
1307 without this function, no perl program will be able to reference the missing
1308 function. You may be able to write the missing function yourself, or you
1309 may be able to find the missing function in the distribution files for
1310 another software package. In this case, you need to instruct the perl
1311 configure-and-build process to use your function. Perform these steps.
1317 Code and test the function you wish to add. Test it carefully; you will
1318 have a much easier time debugging your code independently than when it is a
1323 Here is an implementation of the POSIX truncate function for an operating
1324 system (VOS) that does not supply one, but which does supply the ftruncate()
1327 /* Beginning of modification history */
1328 /* Written 02-01-02 by Nick Ing-Simmons (nick@ing-simmons.net) */
1329 /* End of modification history */
1331 /* VOS doesn't supply a truncate function, so we build one up
1332 from the available POSIX functions. */
1335 #include <sys/types.h>
1339 truncate(const char *path, off_t len)
1341 int fd = open(path,O_WRONLY);
1344 code = ftruncate(fd,len);
1350 Place this file into a subdirectory that has the same name as the operating
1351 system. This file is named perl/vos/vos.c
1355 If your operating system has a hints file (in perl/hints/XXX.sh for an
1356 operating system named XXX), then start with it. If your operating system
1357 has no hints file, then create one. You can use a hints file for a similar
1358 operating system, if one exists, as a template.
1362 Add lines like the following to your hints file. The first line
1363 (d_truncate="define") instructs Configure that the truncate() function
1364 exists. The second line (archobjs="vos.o") instructs the makefiles that the
1365 perl executable depends on the existence of a file named "vos.o". (Make
1366 will automatically look for "vos.c" and compile it with the same options as
1367 the perl source code). The final line ("test -h...") adds a symbolic link
1368 to the top-level directory so that make can find vos.c. Of course, you
1369 should use your own operating system name for the source file of extensions,
1372 # VOS does not have truncate() but we supply one in vos.c
1376 # Help gmake find vos.c
1377 test -h vos.c || ln -s vos/vos.c vos.c
1379 The hints file is a series of shell commands that are run in the top-level
1380 directory (the "perl" directory). Thus, these commands are simply executed
1381 by Configure at an appropriate place during its execution.
1385 At this point, you can run the Configure script and rebuild perl. Carefully
1386 test the newly-built perl to ensure that normal paths, and error paths,
1387 behave as you expect.
1391 =head2 Good ideas waiting for round tuits
1395 =item Configure -Dsrc=/blah/blah
1397 We should be able to emulate B<configure --srcdir>. Tom Tromey
1398 tromey@creche.cygnus.com has submitted some patches to
1399 the dist-users mailing list along these lines. They have been folded
1400 back into the main distribution, but various parts of the perl
1401 Configure/build/install process still assume src='.'.
1403 =item Hint file fixes
1405 Various hint files work around Configure problems. We ought to fix
1406 Configure so that most of them aren't needed.
1408 =item Hint file information
1410 Some of the hint file information (particularly dynamic loading stuff)
1411 ought to be fed back into the main metaconfig distribution.
1415 =head2 Probably good ideas waiting for round tuits
1419 =item GNU configure --options
1421 I've received sensible suggestions for --exec_prefix and other
1422 GNU configure --options. It's not always obvious exactly what is
1423 intended, but this merits investigation.
1427 Currently, B<make clean> isn't all that useful, though
1428 B<make realclean> and B<make distclean> are. This needs a bit of
1429 thought and documentation before it gets cleaned up.
1431 =item Try gcc if cc fails
1433 Currently, we just give up.
1435 =item bypassing safe*alloc wrappers
1437 On some systems, it may be safe to call the system malloc directly
1438 without going through the util.c safe* layers. (Such systems would
1439 accept free(0), for example.) This might be a time-saver for systems
1440 that already have a good malloc. (Recent Linux libc's apparently have
1441 a nice malloc that is well-tuned for the system.)
1445 =head2 Vague possibilities
1451 Get some of the Macintosh stuff folded back into the main distribution.
1453 =item gconvert replacement
1455 Maybe include a replacement function that doesn't lose data in rare
1456 cases of coercion between string and numerical values.
1458 =item Improve makedepend
1460 The current makedepend process is clunky and annoyingly slow, but it
1461 works for most folks. Alas, it assumes that there is a filename
1462 $firstmakefile that the B<make> command will try to use before it uses
1463 F<Makefile>. Such may not be the case for all B<make> commands,
1464 particularly those on non-Unix systems.
1466 Probably some variant of the BSD F<.depend> file will be useful.
1467 We ought to check how other packages do this, if they do it at all.
1468 We could probably pre-generate the dependencies (with the exception of
1469 malloc.o, which could probably be determined at F<Makefile.SH>
1472 =item GNU Makefile standard targets
1474 GNU software generally has standardized Makefile targets. Unless we
1475 have good reason to do otherwise, I see no reason not to support them.
1479 Somehow, straighten out, document, and implement lockf(), flock(),
1480 and/or fcntl() file locking. It's a mess. See $d_fcntl_can_lock
1481 in recent config.sh files though.
1485 =head2 Copyright Issues
1487 The following is based on the consensus of a couple of IPR lawyers,
1488 but it is of course not a legally binding statement, just a common
1495 Tacking on copyright statements is unnecessary to begin with because
1496 of the Berne convention. But assuming you want to go ahead...
1500 The right form of a copyright statement is
1502 Copyright (C) Year, Year, ... by Someone
1504 The (C) is not required everywhere but it doesn't hurt and in certain
1505 jurisdictions it is required, so let's leave it in. (Yes, it's true
1506 that in some jurisdictions the "(C)" is not legally binding, one should
1507 use the true ringed-C. But we don't have that character available for
1508 Perl's source code.)
1510 The years must be listed out separately. Year-Year is not correct.
1511 Only the years when the piece has changed 'significantly' may be added.
1515 One cannot give away one's copyright trivially. One can give one's
1516 copyright away by using public domain, but even that requires a little
1517 bit more than just saying 'this is in public domain'. (What it
1518 exactly requires depends on your jurisdiction.) But barring public
1519 domain, one cannot "transfer" one's copyright to another person or
1520 entity. In the context of software, it means that contributors cannot
1521 give away their copyright or "transfer" it to the "owner" of the software.
1523 Also remember that in many cases if you are employed by someone,
1524 your work may be copyrighted to your employer, even when you are
1525 contributing on your own time (this all depends on too many things
1526 to list here). But the bottom line is that you definitely can't give
1527 away a copyright you may not even have.
1529 What is possible, however, is that the software can simply state
1531 Copyright (C) Year, Year, ... by Someone and others
1533 and then list the "others" somewhere in the distribution.
1534 And this is exactly what Perl does. (The "somewhere" is
1535 AUTHORS and the Changes* files.)
1539 Split files, merged files, and generated files are problematic.
1540 The rule of thumb: in split files, copy the copyright years of
1541 the original file to all the new files; in merged files make
1542 an union of the copyright years of all the old files; in generated
1543 files propagate the copyright years of the generating file(s).
1547 The files of Perl source code distribution do carry a lot of
1548 copyrights, by various people. (There are many copyrights embedded in
1549 perl.c, for example.) The most straightforward thing for pumpkings to
1550 do is to simply update Larry's copyrights at the beginning of the
1551 *.[hcy], x2p/*.[hcy], *.pl, and README files, and leave all other
1552 copyrights alone. Doing more than that requires quite a bit of tracking.
1558 Original author: Andy Dougherty doughera@lafayette.edu .
1559 Additions by Chip Salzenberg chip@perl.com and
1560 Tim Bunce Tim.Bunce@ig.co.uk .
1562 All opinions expressed herein are those of the authorZ<>(s).
1564 =head1 LAST MODIFIED
1566 27-04-2007 H.Merijn Brand
1567 $Id: pumpkin.pod,v 1.23 2000/01/13 19:45:13 doughera Released $