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, and regen_pods targets.
510 =head2 make regen_headers
512 The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically
513 generated by perl scripts. Since the user isn't guaranteed to have a
514 working perl, we can't require the user to generate them. Hence you have
515 to, if you're making a distribution.
517 I used to include rules like the following in the makefile:
519 # The following three header files are generated automatically
520 # The correct versions should be already supplied with the perl kit,
521 # in case you don't have perl or 'sh' available.
522 # The - is to ignore error return codes in case you have the source
523 # installed read-only or you don't have perl yet.
524 keywords.h: keywords.pl
525 @echo "Don't worry if this fails."
529 However, I got B<lots> of mail consisting of people worrying because the
530 command failed. I eventually decided that I would save myself time
531 and effort by manually running C<make regen_headers> myself rather
532 than answering all the questions and complaints about the failing
535 =head2 make regen_pods
537 Will run `make regen_pods` in the pod directory for indexing.
539 =head2 global.sym, interp.sym and perlio.sym
541 Make sure these files are up-to-date. Read the comments in these
542 files and in perl_exp.SH to see what to do.
544 =head2 Binary compatibility
546 If you do change F<global.sym> or F<interp.sym>, think carefully about
547 what you are doing. To the extent reasonable, we'd like to maintain
548 source and binary compatibility with older releases of perl. That way,
549 extensions built under one version of perl will continue to work with
550 new versions of perl.
552 Of course, some incompatible changes may well be necessary. I'm just
553 suggesting that we not make any such changes without thinking carefully
554 about them first. If possible, we should provide
555 backwards-compatibility stubs. There's a lot of XS code out there.
556 Let's not force people to keep changing it.
560 F<ext/Devel/PPPort/PPPort.pm> needs to be synchronized to include all
561 new macros added to .h files (normally perl.h and XSUB.h, but others
562 as well). Since chances are that when a new macro is added the
563 committer will forget to update F<PPPort.pm>, it's the best to diff for
564 changes in .h files when making a new release and making sure that
565 F<PPPort.pm> contains them all.
567 The pumpking can delegate the synchronization responsibility to anybody
568 else, but the release process is the only place where we can make sure
569 that no new macros fell through the cracks.
573 Be sure to update the F<Changes> file. Try to include both an overall
574 summary as well as detailed descriptions of the changes. Your
575 audience will include other developers and users, so describe
576 user-visible changes (if any) in terms they will understand, not in
577 code like "initialize foo variable in bar function".
579 There are differing opinions on whether the detailed descriptions
580 ought to go in the Changes file or whether they ought to be available
581 separately in the patch file (or both). There is no disagreement that
582 detailed descriptions ought to be easily available somewhere.
584 If you update the subversion number in F<patchlevel.h>, you may need
585 to change the version number near the top of the F<Changes> file.
587 =head2 Bumping perl's version
589 If you bump perl's version, you will need to update a few things:
590 the L<perlhist> manpage for the date of release, the version number and
591 perldelta reference in the top level F<README> (and maybe the copyright
592 year too), the F<META.yml> file (generated via F<Porting/makemeta>, be
593 sure to run it with the current bleadperl), and the meta-info about
594 dual-lived modules in Module::Corelist (F<Porting/corelist.pl> does that).
595 Make sure the numbered feature bundles in F<lib/feature.pm> are also
600 The F<pod/perltodo.pod> file contains a roughly-categorized unordered
601 list of aspects of Perl that could use enhancement, features that could
602 be added, areas that could be cleaned up, and so on. During your term
603 as pumpkin-holder, you will probably address some of these issues, and
604 perhaps identify others which, while you decide not to address them this
605 time around, may be tackled in the future. Update the file to reflect
606 the situation as it stands when you hand over the pumpkin.
608 You might like, early in your pumpkin-holding career, to see if you
609 can find champions for particular issues on the to-do list: an issue
610 owned is an issue more likely to be resolved.
612 There are also some more porting-specific L</Todo> items later in this
615 =head2 OS/2-specific updates
617 In the os2 directory is F<diff.configure>, a set of OS/2-specific
618 diffs against B<Configure>. If you make changes to Configure, you may
619 want to consider regenerating this diff file to save trouble for the
622 You can also consider the OS/2 diffs as reminders of portability
623 things that need to be fixed in Configure.
625 =head2 VMS-specific updates
627 The Perl revision number appears as "perl5" in configure.com.
628 It is courteous to update that if necessary.
630 =head2 Making the new distribution
632 Suppose, for example, that you want to make version 5.004_08. Then you can
633 do something like the following
635 mkdir ../perl5.004_08
636 awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08
638 tar cf perl5.004_08.tar perl5.004_08
639 gzip --best perl5.004_08.tar
641 These steps, with extra checks, are automated by the Porting/makerel
644 =head2 Making a new patch
646 I find the F<makepatch> utility quite handy for making patches.
647 You can obtain it from any CPAN archive under
648 http://www.cpan.org/authors/Johan_Vromans/ . There are a couple
649 of differences between my version and the standard one. I have mine do
652 # Print a reassuring "End of Patch" note so people won't
653 # wonder if their mailer truncated patches.
654 print "\n\nEnd of Patch.\n";
656 at the end. That's because I used to get questions from people asking
657 if their mail was truncated.
659 It also writes Index: lines which include the new directory prefix
660 (change Index: print, approx line 294 or 310 depending on the version,
661 to read: print PATCH ("Index: $newdir$new\n");). That helps patches
662 work with more POSIX conformant patch programs.
664 Here's how I generate a new patch. I'll use the hypothetical
665 5.004_07 to 5.004_08 patch as an example.
667 # unpack perl5.004_07/
668 gzip -d -c perl5.004_07.tar.gz | tar -xof -
669 # unpack perl5.004_08/
670 gzip -d -c perl5.004_08.tar.gz | tar -xof -
671 makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat
673 Makepatch will automatically generate appropriate B<rm> commands to remove
674 deleted files. Unfortunately, it will not correctly set permissions
675 for newly created files, so you may have to do so manually. For example,
676 patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable,
677 so at the top of the patch, I inserted the following lines:
683 Now, of course, my patch is now wrong because makepatch didn't know I
684 was going to do that command, and it patched against /dev/null.
686 So, what I do is sort out all such shell commands that need to be in the
687 patch (including possible mv-ing of files, if needed) and put that in the
688 shell commands at the top of the patch. Next, I delete all the patch parts
689 of perl5.004_08.pat, leaving just the shell commands. Then, I do the
693 sh ../perl5.004_08.pat
695 makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat
697 (Note the append to preserve my shell commands.)
698 Now, my patch will line up with what the end users are going to do.
700 =head2 Testing your patch
702 It seems obvious, but be sure to test your patch. That is, verify that
703 it produces exactly the same thing as your full distribution.
706 gzip -d -c perl5.004_07.tar.gz | tar -xf -
708 sh ../perl5.004_08.pat
709 patch -p1 -N < ../perl5.004_08.pat
711 gdiff -r perl5.004_07 perl5.004_08
713 where B<gdiff> is GNU diff. Other diff's may also do recursive checking.
717 Again, it's obvious, but you should test your new version as widely as you
718 can. You can be sure you'll hear about it quickly if your version doesn't
719 work on both ANSI and pre-ANSI compilers, and on common systems such as
720 SunOS 4.1.[34], Solaris, and Linux.
722 If your changes include conditional code, try to test the different
723 branches as thoroughly as you can. For example, if your system
724 supports dynamic loading, you can also test static loading with
728 You can also hand-tweak your config.h to try out different #ifdef
735 =item gcc -ansi -pedantic
737 Configure -Dgccansipedantic [ -Dcc=gcc ] will enable (via the cflags script,
738 not $Config{ccflags}) the gcc strict ANSI C flags -ansi and -pedantic for
739 the compilation of the core files on platforms where it knows it can
740 do so (like Linux, see cflags.SH for the full list), and on some
741 platforms only one (Solaris can do only -pedantic, not -ansi).
742 The flag -DPERL_GCC_PEDANTIC also gets added, since gcc does not add
743 any internal cpp flag to signify that -pedantic is being used, as it
744 does for -ansi (__STRICT_ANSI__).
746 Note that the -ansi and -pedantic are enabled only for version 3 (and
747 later) of gcc, since even gcc version 2.95.4 finds lots of seemingly
748 false "value computed not used" errors from Perl.
750 The -ansi and -pedantic are useful in catching at least the following
751 nonportable practices:
757 gcc-specific extensions
773 The -Dgccansipedantic should be used only when cleaning up the code,
774 not for production builds, since otherwise gcc cannot inline certain
779 =head1 Running Purify
781 Purify is a commercial tool that is helpful in identifying memory
782 overruns, wild pointers, memory leaks and other such badness. Perl
783 must be compiled in a specific way for optimal testing with Purify.
785 Use the following commands to test perl with Purify:
787 sh Configure -des -Doptimize=-g -Uusemymalloc -Dusemultiplicity \
789 setenv PURIFYOPTIONS "-chain-length=25"
792 ln -s ../pureperl perl
793 setenv PERL_DESTRUCT_LEVEL 2
796 Disabling Perl's malloc allows Purify to monitor allocations and leaks
797 more closely; using Perl's malloc will make Purify report most leaks
798 in the "potential" leaks category. Enabling the multiplicity option
799 allows perl to clean up thoroughly when the interpreter shuts down, which
800 reduces the number of bogus leak reports from Purify. The -DPURIFY
801 enables any Purify-specific debugging code in the sources.
803 Purify outputs messages in "Viewer" windows by default. If you don't have
804 a windowing environment or if you simply want the Purify output to
805 unobtrusively go to a log file instead of to the interactive window,
806 use the following options instead:
808 setenv PURIFYOPTIONS "-chain-length=25 -windows=no -log-file=perl.log \
811 The only currently known leaks happen when there are compile-time errors
812 within eval or require. (Fixing these is non-trivial, unfortunately, but
813 they must be fixed eventually.)
815 =head1 Common Gotchas
819 =item Probably Prefer POSIX
821 It's often the case that you'll need to choose whether to do
822 something the BSD-ish way or the POSIX-ish way. It's usually not
823 a big problem when the two systems use different names for similar
824 functions, such as memcmp() and bcmp(). The perl.h header file
825 handles these by appropriate #defines, selecting the POSIX mem*()
826 functions if available, but falling back on the b*() functions, if
829 More serious is the case where some brilliant person decided to
830 use the same function name but give it a different meaning or
831 calling sequence :-). getpgrp() and setpgrp() come to mind.
832 These are a real problem on systems that aim for conformance to
833 one standard (e.g. POSIX), but still try to support the other way
834 of doing things (e.g. BSD). My general advice (still not really
835 implemented in the source) is to do something like the following.
836 Suppose there are two alternative versions, fooPOSIX() and
840 /* use fooPOSIX(); */
843 /* try to emulate fooPOSIX() with fooBSD();
844 perhaps with the following: */
845 # define fooPOSIX fooBSD
847 # /* Uh, oh. We have to supply our own. */
848 # define fooPOSIX Perl_fooPOSIX
852 =item Think positively
854 If you need to add an #ifdef test, it is usually easier to follow if you
855 think positively, e.g.
857 #ifdef HAS_NEATO_FEATURE
858 /* use neato feature */
860 /* use some fallback mechanism */
863 rather than the more impenetrable
865 #ifndef MISSING_NEATO_FEATURE
866 /* Not missing it, so we must have it, so use it */
868 /* Are missing it, so fall back on something else. */
871 Of course for this toy example, there's not much difference. But when
872 the #ifdef's start spanning a couple of screen fulls, and the #else's
873 are marked something like
875 #else /* !MISSING_NEATO_FEATURE */
877 I find it easy to get lost.
879 =item Providing Missing Functions -- Problem
881 Not all systems have all the neat functions you might want or need, so
882 you might decide to be helpful and provide an emulation. This is
883 sound in theory and very kind of you, but please be careful about what
884 you name the function. Let me use the C<pause()> function as an
887 Perl5.003 has the following in F<perl.h>
890 #define pause() sleep((32767<<16)+32767)
893 Configure sets HAS_PAUSE if the system has the pause() function, so
894 this #define only kicks in if the pause() function is missing.
897 Unfortunately, some systems apparently have a prototype for pause()
898 in F<unistd.h>, but don't actually have the function in the library.
899 (Or maybe they do have it in a library we're not using.)
901 Thus, the compiler sees something like
903 extern int pause(void);
905 #define pause() sleep((32767<<16)+32767)
907 and dies with an error message. (Some compilers don't mind this;
908 others apparently do.)
910 To work around this, 5.003_03 and later have the following in perl.h:
912 /* Some unistd.h's give a prototype for pause() even though
913 HAS_PAUSE ends up undefined. This causes the #define
914 below to be rejected by the compiler. Sigh.
919 # define Pause() sleep((32767<<16)+32767)
924 The curious reader may wonder why I didn't do the following in
930 sleep((32767<<16)+32767);
934 That is, since the function is missing, just provide it.
935 Then things would probably be been alright, it would seem.
937 Well, almost. It could be made to work. The problem arises from the
938 conflicting needs of dynamic loading and namespace protection.
940 For dynamic loading to work on AIX (and VMS) we need to provide a list
941 of symbols to be exported. This is done by the script F<perl_exp.SH>,
942 which reads F<global.sym> and F<interp.sym>. Thus, the C<pause>
943 symbol would have to be added to F<global.sym> So far, so good.
945 On the other hand, one of the goals of Perl5 is to make it easy to
946 either extend or embed perl and link it with other libraries. This
947 means we have to be careful to keep the visible namespace "clean".
948 That is, we don't want perl's global variables to conflict with
949 those in the other application library. Although this work is still
950 in progress, the way it is currently done is via the F<embed.h> file.
951 This file is built from the F<global.sym> and F<interp.sym> files,
952 since those files already list the globally visible symbols. If we
953 had added C<pause> to global.sym, then F<embed.h> would contain the
956 #define pause Perl_pause
958 and calls to C<pause> in the perl sources would now point to
959 C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable,
960 it will go looking for C<perl_pause>, which probably won't exist in any
961 of the standard libraries. Thus the build of perl will fail.
963 Those systems where C<HAS_PAUSE> is not defined would be ok, however,
964 since they would get a C<Perl_pause> function in util.c. The rest of
965 the world would be in trouble.
967 And yes, this scenario has happened. On SCO, the function C<chsize>
968 is available. (I think it's in F<-lx>, the Xenix compatibility
969 library.) Since the perl4 days (and possibly before), Perl has
970 included a C<chsize> function that gets called something akin to
973 I32 chsize(fd, length)
979 #define chsize Perl_chsize
981 to F<embed.h>, the compile started failing on SCO systems.
983 The "fix" is to give the function a different name. The one
984 implemented in 5.003_05 isn't optimal, but here's what was done:
987 # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */
990 # define my_chsize chsize
993 My explanatory comment in patch 5.003_05 said:
995 Undef and then re-define my_chsize from Perl_my_chsize to
996 just plain chsize if this system HAS_CHSIZE. This probably only
997 applies to SCO. This shows the perils of having internal
998 functions with the same name as external library functions :-).
1000 Now, we can safely put C<my_chsize> in F<global.sym>, export it, and
1001 hide it with F<embed.h>.
1003 To be consistent with what I did for C<pause>, I probably should have
1004 called the new function C<Chsize>, rather than C<my_chsize>.
1005 However, the perl sources are quite inconsistent on this (Consider
1006 New, Mymalloc, and Myremalloc, to name just a few.)
1008 There is a problem with this fix, however, in that C<Perl_chsize>
1009 was available as a F<libperl.a> library function in 5.003, but it
1010 isn't available any more (as of 5.003_07). This means that we've
1011 broken binary compatibility. This is not good.
1013 =item Providing missing functions -- some ideas
1015 We currently don't have a standard way of handling such missing
1016 function names. Right now, I'm effectively thinking aloud about a
1017 solution. Some day, I'll try to formally propose a solution.
1019 Part of the problem is that we want to have some functions listed as
1020 exported but not have their names mangled by embed.h or possibly
1021 conflict with names in standard system headers. We actually already
1022 have such a list at the end of F<perl_exp.SH> (though that list is
1025 # extra globals not included above.
1026 cat <<END >> perl.exp
1050 This still needs much thought, but I'm inclined to think that one
1051 possible solution is to prefix all such functions with C<perl_> in the
1052 source and list them along with the other C<perl_*> functions in
1055 Thus, for C<chsize>, we'd do something like the following:
1059 # define perl_chsize chsize
1062 then in some file (e.g. F<util.c> or F<doio.c>) do
1065 I32 perl_chsize(fd, length)
1066 /* implement the function here . . . */
1069 Alternatively, we could just always use C<chsize> everywhere and move
1070 C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would
1071 probably be fine as long as our C<chsize> function agreed with all the
1072 C<chsize> function prototypes in the various systems we'll be using.
1073 As long as the prototypes in actual use don't vary that much, this is
1074 probably a good alternative. (As a counter-example, note how Configure
1075 and perl have to go through hoops to find and use get Malloc_t and
1076 Free_t for C<malloc> and C<free>.)
1078 At the moment, this latter option is what I tend to prefer.
1080 =item All the world's a VAX
1082 Sorry, showing my age:-). Still, all the world is not BSD 4.[34],
1083 SVR4, or POSIX. Be aware that SVR3-derived systems are still quite
1084 common (do you have any idea how many systems run SCO?) If you don't
1085 have a bunch of v7 manuals handy, the metaconfig units (by default
1086 installed in F</usr/local/lib/dist/U>) are a good resource to look at
1091 =head1 Miscellaneous Topics
1095 Why does perl use a metaconfig-generated Configure script instead of an
1096 autoconf-generated configure script?
1098 Metaconfig and autoconf are two tools with very similar purposes.
1099 Metaconfig is actually the older of the two, and was originally written
1100 by Larry Wall, while autoconf is probably now used in a wider variety of
1101 packages. The autoconf info file discusses the history of autoconf and
1102 how it came to be. The curious reader is referred there for further
1105 Overall, both tools are quite good, I think, and the choice of which one
1106 to use could be argued either way. In March, 1994, when I was just
1107 starting to work on Configure support for Perl5, I considered both
1108 autoconf and metaconfig, and eventually decided to use metaconfig for the
1113 =item Compatibility with Perl4
1115 Perl4 used metaconfig, so many of the #ifdef's were already set up for
1116 metaconfig. Of course metaconfig had evolved some since Perl4's days,
1117 but not so much that it posed any serious problems.
1119 =item Metaconfig worked for me
1121 My system at the time was Interactive 2.2, an SVR3.2/386 derivative that
1122 also had some POSIX support. Metaconfig-generated Configure scripts
1123 worked fine for me on that system. On the other hand, autoconf-generated
1124 scripts usually didn't. (They did come quite close, though, in some
1125 cases.) At the time, I actually fetched a large number of GNU packages
1126 and checked. Not a single one configured and compiled correctly
1127 out-of-the-box with the system's cc compiler.
1129 =item Configure can be interactive
1131 With both autoconf and metaconfig, if the script works, everything is
1132 fine. However, one of my main problems with autoconf-generated scripts
1133 was that if it guessed wrong about something, it could be B<very> hard to
1134 go back and fix it. For example, autoconf always insisted on passing the
1135 -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I
1136 wanted or needed for that package. There was no way short of editing the
1137 configure script to turn this off. You couldn't just edit the resulting
1138 Makefile at the end because the -Xp flag influenced a number of other
1141 Metaconfig's Configure scripts, on the other hand, can be interactive.
1142 Thus if Configure is guessing things incorrectly, you can go back and fix
1143 them. This isn't as important now as it was when we were actively
1144 developing Configure support for new features such as dynamic loading,
1145 but it's still useful occasionally.
1149 At the time, autoconf-generated scripts were covered under the GNU Public
1150 License, and hence weren't suitable for inclusion with Perl, which has a
1151 different licensing policy. (Autoconf's licensing has since changed.)
1155 Metaconfig builds up Configure from a collection of discrete pieces
1156 called "units". You can override the standard behavior by supplying your
1157 own unit. With autoconf, you have to patch the standard files instead.
1158 I find the metaconfig "unit" method easier to work with. Others
1159 may find metaconfig's units clumsy to work with.
1163 =head2 Why isn't there a directory to override Perl's library?
1165 Mainly because no one's gotten around to making one. Note that
1166 "making one" involves changing perl.c, Configure, config_h.SH (and
1167 associated files, see above), and I<documenting> it all in the
1170 Apparently, most folks who want to override one of the standard library
1171 files simply do it by overwriting the standard library files.
1175 In the perl.c sources, you'll find an undocumented APPLLIB_EXP
1176 variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are
1177 documented in config_h.SH). Here's what APPLLIB_EXP is for, from
1178 a mail message from Larry:
1180 The main intent of APPLLIB_EXP is for folks who want to send out a
1181 version of Perl embedded in their product. They would set the symbol
1182 to be the name of the library containing the files needed to run or to
1183 support their particular application. This works at the "override"
1184 level to make sure they get their own versions of any library code that
1185 they absolutely must have configuration control over.
1187 As such, I don't see any conflict with a sysadmin using it for a
1188 override-ish sort of thing, when installing a generic Perl. It should
1189 probably have been named something to do with overriding though. Since
1190 it's undocumented we could still change it... :-)
1192 Given that it's already there, you can use it to override distribution modules.
1193 One way to do that is to add
1195 ccflags="$ccflags -DAPPLLIB_EXP=\"/my/override\""
1197 to your config.over file. (You have to be particularly careful to get the
1198 double quotes in. APPLLIB_EXP must be a valid C string. It might
1199 actually be easier to just #define it yourself in perl.c.)
1201 Then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB. Perl will
1202 also search architecture-specific and version-specific subdirectories of
1205 =head2 Shared libperl.so location
1207 Why isn't the shared libperl.so installed in /usr/lib/ along
1208 with "all the other" shared libraries? Instead, it is installed
1209 in $archlib, which is typically something like
1211 /usr/local/lib/perl5/archname/5.00404
1213 and is architecture- and version-specific.
1215 The basic reason why a shared libperl.so gets put in $archlib is so that
1216 you can have more than one version of perl on the system at the same time,
1217 and have each refer to its own libperl.so.
1219 Three examples might help. All of these work now; none would work if you
1220 put libperl.so in /usr/lib.
1226 Suppose you want to have both threaded and non-threaded perl versions
1227 around. Configure will name both perl libraries "libperl.so" (so that
1228 you can link to them with -lperl). The perl binaries tell them apart
1229 by having looking in the appropriate $archlib directories.
1233 Suppose you have perl5.004_04 installed and you want to try to compile
1234 it again, perhaps with different options or after applying a patch.
1235 If you already have libperl.so installed in /usr/lib/, then it may be
1236 either difficult or impossible to get ld.so to find the new libperl.so
1237 that you're trying to build. If, instead, libperl.so is tucked away in
1238 $archlib, then you can always just change $archlib in the current perl
1239 you're trying to build so that ld.so won't find your old libperl.so.
1240 (The INSTALL file suggests you do this when building a debugging perl.)
1244 The shared perl library is not a "well-behaved" shared library with
1245 proper major and minor version numbers, so you can't necessarily
1246 have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose
1247 perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05
1248 were to install /usr/lib/libperl.so.4.5. Now, when you try to run
1249 perl5.004_04, ld.so might try to load libperl.so.4.5, since it has
1250 the right "major version" number. If this works at all, it almost
1251 certainly defeats the reason for keeping perl5.004_04 around. Worse,
1252 with development subversions, you certaily can't guarantee that
1253 libperl.so.4.4 and libperl.so.4.55 will be compatible.
1255 Anyway, all this leads to quite obscure failures that are sure to drive
1256 casual users crazy. Even experienced users will get confused :-). Upon
1257 reflection, I'd say leave libperl.so in $archlib.
1261 =head2 Indentation style
1263 Over the years Perl has become a mishmash of
1264 various indentation styles, but the original "Larry style" can
1265 probably be restored with (GNU) indent somewhat like this:
1267 indent -kr -nce -psl -sc
1269 A more ambitious solution would also specify a list of Perl specific
1270 types with -TSV -TAV -THV .. -TMAGIC -TPerlIO ... but that list would
1271 be quite ungainly. Also note that GNU indent also doesn't do aligning
1272 of consecutive assignments, which would truly wreck the layout in
1273 places like sv.c:Perl_sv_upgrade() or sv.c:Perl_clone_using().
1274 Similarly nicely aligned &&s, ||s and ==s would not be respected.
1276 =head1 Upload Your Work to CPAN
1278 You can upload your work to CPAN if you have a CPAN id. Check out
1279 http://www.cpan.org/modules/04pause.html for information on
1280 _PAUSE_, the Perl Author's Upload Server.
1282 I typically upload both the patch file, e.g. F<perl5.004_08.pat.gz>
1283 and the full tar file, e.g. F<perl5.004_08.tar.gz>.
1285 If you want your patch to appear in the F<src/5.0/unsupported>
1286 directory on CPAN, send e-mail to the CPAN master librarian. (Check
1287 out http://www.cpan.org/CPAN.html ).
1289 =head1 Help Save the World
1291 You should definitely announce your patch on the perl5-porters list.
1292 You should also consider announcing your patch on
1293 comp.lang.perl.announce, though you should make it quite clear that a
1294 subversion is not a production release, and be prepared to deal with
1295 people who will not read your disclaimer.
1299 Here, in no particular order, are some Configure and build-related
1300 items that merit consideration. This list isn't exhaustive, it's just
1301 what I came up with off the top of my head.
1303 =head2 Adding missing library functions to Perl
1305 The perl Configure script automatically determines which headers and
1306 functions you have available on your system and arranges for them to be
1307 included in the compilation and linking process. Occasionally, when porting
1308 perl to an operating system for the first time, you may find that the
1309 operating system is missing a key function. While perl may still build
1310 without this function, no perl program will be able to reference the missing
1311 function. You may be able to write the missing function yourself, or you
1312 may be able to find the missing function in the distribution files for
1313 another software package. In this case, you need to instruct the perl
1314 configure-and-build process to use your function. Perform these steps.
1320 Code and test the function you wish to add. Test it carefully; you will
1321 have a much easier time debugging your code independently than when it is a
1326 Here is an implementation of the POSIX truncate function for an operating
1327 system (VOS) that does not supply one, but which does supply the ftruncate()
1330 /* Beginning of modification history */
1331 /* Written 02-01-02 by Nick Ing-Simmons (nick@ing-simmons.net) */
1332 /* End of modification history */
1334 /* VOS doesn't supply a truncate function, so we build one up
1335 from the available POSIX functions. */
1338 #include <sys/types.h>
1342 truncate(const char *path, off_t len)
1344 int fd = open(path,O_WRONLY);
1347 code = ftruncate(fd,len);
1353 Place this file into a subdirectory that has the same name as the operating
1354 system. This file is named perl/vos/vos.c
1358 If your operating system has a hints file (in perl/hints/XXX.sh for an
1359 operating system named XXX), then start with it. If your operating system
1360 has no hints file, then create one. You can use a hints file for a similar
1361 operating system, if one exists, as a template.
1365 Add lines like the following to your hints file. The first line
1366 (d_truncate="define") instructs Configure that the truncate() function
1367 exists. The second line (archobjs="vos.o") instructs the makefiles that the
1368 perl executable depends on the existence of a file named "vos.o". (Make
1369 will automatically look for "vos.c" and compile it with the same options as
1370 the perl source code). The final line ("test -h...") adds a symbolic link
1371 to the top-level directory so that make can find vos.c. Of course, you
1372 should use your own operating system name for the source file of extensions,
1375 # VOS does not have truncate() but we supply one in vos.c
1379 # Help gmake find vos.c
1380 test -h vos.c || ln -s vos/vos.c vos.c
1382 The hints file is a series of shell commands that are run in the top-level
1383 directory (the "perl" directory). Thus, these commands are simply executed
1384 by Configure at an appropriate place during its execution.
1388 At this point, you can run the Configure script and rebuild perl. Carefully
1389 test the newly-built perl to ensure that normal paths, and error paths,
1390 behave as you expect.
1394 =head2 Good ideas waiting for round tuits
1398 =item Configure -Dsrc=/blah/blah
1400 We should be able to emulate B<configure --srcdir>. Tom Tromey
1401 tromey@creche.cygnus.com has submitted some patches to
1402 the dist-users mailing list along these lines. They have been folded
1403 back into the main distribution, but various parts of the perl
1404 Configure/build/install process still assume src='.'.
1406 =item Hint file fixes
1408 Various hint files work around Configure problems. We ought to fix
1409 Configure so that most of them aren't needed.
1411 =item Hint file information
1413 Some of the hint file information (particularly dynamic loading stuff)
1414 ought to be fed back into the main metaconfig distribution.
1418 =head2 Probably good ideas waiting for round tuits
1422 =item GNU configure --options
1424 I've received sensible suggestions for --exec_prefix and other
1425 GNU configure --options. It's not always obvious exactly what is
1426 intended, but this merits investigation.
1430 Currently, B<make clean> isn't all that useful, though
1431 B<make realclean> and B<make distclean> are. This needs a bit of
1432 thought and documentation before it gets cleaned up.
1434 =item Try gcc if cc fails
1436 Currently, we just give up.
1438 =item bypassing safe*alloc wrappers
1440 On some systems, it may be safe to call the system malloc directly
1441 without going through the util.c safe* layers. (Such systems would
1442 accept free(0), for example.) This might be a time-saver for systems
1443 that already have a good malloc. (Recent Linux libc's apparently have
1444 a nice malloc that is well-tuned for the system.)
1448 =head2 Vague possibilities
1454 Get some of the Macintosh stuff folded back into the main distribution.
1456 =item gconvert replacement
1458 Maybe include a replacement function that doesn't lose data in rare
1459 cases of coercion between string and numerical values.
1461 =item Improve makedepend
1463 The current makedepend process is clunky and annoyingly slow, but it
1464 works for most folks. Alas, it assumes that there is a filename
1465 $firstmakefile that the B<make> command will try to use before it uses
1466 F<Makefile>. Such may not be the case for all B<make> commands,
1467 particularly those on non-Unix systems.
1469 Probably some variant of the BSD F<.depend> file will be useful.
1470 We ought to check how other packages do this, if they do it at all.
1471 We could probably pre-generate the dependencies (with the exception of
1472 malloc.o, which could probably be determined at F<Makefile.SH>
1475 =item GNU Makefile standard targets
1477 GNU software generally has standardized Makefile targets. Unless we
1478 have good reason to do otherwise, I see no reason not to support them.
1482 Somehow, straighten out, document, and implement lockf(), flock(),
1483 and/or fcntl() file locking. It's a mess. See $d_fcntl_can_lock
1484 in recent config.sh files though.
1488 =head2 Copyright Issues
1490 The following is based on the consensus of a couple of IPR lawyers,
1491 but it is of course not a legally binding statement, just a common
1498 Tacking on copyright statements is unnecessary to begin with because
1499 of the Berne convention. But assuming you want to go ahead...
1503 The right form of a copyright statement is
1505 Copyright (C) Year, Year, ... by Someone
1507 The (C) is not required everywhere but it doesn't hurt and in certain
1508 jurisdictions it is required, so let's leave it in. (Yes, it's true
1509 that in some jurisdictions the "(C)" is not legally binding, one should
1510 use the true ringed-C. But we don't have that character available for
1511 Perl's source code.)
1513 The years must be listed out separately. Year-Year is not correct.
1514 Only the years when the piece has changed 'significantly' may be added.
1518 One cannot give away one's copyright trivially. One can give one's
1519 copyright away by using public domain, but even that requires a little
1520 bit more than just saying 'this is in public domain'. (What it
1521 exactly requires depends on your jurisdiction.) But barring public
1522 domain, one cannot "transfer" one's copyright to another person or
1523 entity. In the context of software, it means that contributors cannot
1524 give away their copyright or "transfer" it to the "owner" of the software.
1526 Also remember that in many cases if you are employed by someone,
1527 your work may be copyrighted to your employer, even when you are
1528 contributing on your own time (this all depends on too many things
1529 to list here). But the bottom line is that you definitely can't give
1530 away a copyright you may not even have.
1532 What is possible, however, is that the software can simply state
1534 Copyright (C) Year, Year, ... by Someone and others
1536 and then list the "others" somewhere in the distribution.
1537 And this is exactly what Perl does. (The "somewhere" is
1538 AUTHORS and the Changes* files.)
1542 Split files, merged files, and generated files are problematic.
1543 The rule of thumb: in split files, copy the copyright years of
1544 the original file to all the new files; in merged files make
1545 an union of the copyright years of all the old files; in generated
1546 files propagate the copyright years of the generating file(s).
1550 The files of Perl source code distribution do carry a lot of
1551 copyrights, by various people. (There are many copyrights embedded in
1552 perl.c, for example.) The most straightforward thing for pumpkings to
1553 do is to simply update Larry's copyrights at the beginning of the
1554 *.[hcy], x2p/*.[hcy], *.pl, and README files, and leave all other
1555 copyrights alone. Doing more than that requires quite a bit of tracking.
1561 Original author: Andy Dougherty doughera@lafayette.edu .
1562 Additions by Chip Salzenberg chip@perl.com and
1563 Tim Bunce Tim.Bunce@ig.co.uk .
1565 All opinions expressed herein are those of the authorZ<>(s).
1567 =head1 LAST MODIFIED
1569 27-04-2007 H.Merijn Brand
1570 $Id: pumpkin.pod,v 1.23 2000/01/13 19:45:13 doughera Released $