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. Perl's metaconfig units
368 should be available on CPAN. A set of units that will work with
369 perl5.005 is in the file F<mc_units-5.005_00-01.tar.gz> under
370 http://www.cpan.org/authors/id/ANDYD/ . The mc_units tar file
371 should be unpacked in your main perl source directory. Note: those
372 units were for use with 5.005. There may have been changes since then.
373 Check for later versions or contact perl5-porters@perl.org to obtain a
374 pointer to the current version.
376 Alternatively, do consider if the F<*ish.h> files might be a better
377 place for your changes.
381 Make sure the MANIFEST is up-to-date. You can use dist's B<manicheck>
382 program for this. You can also use
384 perl -w -MExtUtils::Manifest=fullcheck -e fullcheck
386 Both commands will also list extra files in the directory that are not
389 The MANIFEST is normally sorted.
391 If you are using metaconfig to regenerate Configure, then you should note
392 that metaconfig actually uses MANIFEST.new, so you want to be sure
393 MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new
394 distinction particularly useful, but that's probably because I still haven't
395 learned how to use the full suite of tools in the dist distribution.
397 =head2 Check permissions
399 All the tests in the t/ directory ought to be executable. The
400 main makefile used to do a 'chmod t/*/*.t', but that resulted in
401 a self-modifying distribution--something some users would strongly
402 prefer to avoid. The F<t/TEST> script will check for this
403 and do the chmod if needed, but the tests still ought to be
406 In all, the following files should probably be executable:
420 vms/ext/Stdio/test.pl
424 Other things ought to be readable, at least :-).
426 Probably, the permissions for the files could be encoded in MANIFEST
427 somehow, but I'm reluctant to change MANIFEST itself because that
428 could break old scripts that use MANIFEST.
430 I seem to recall that some SVR3 systems kept some sort of file that listed
431 permissions for system files; something like that might be appropriate.
435 This will build a config.sh and config.h. You can skip this if you haven't
436 changed Configure or config_h.SH at all. I use the following command
438 sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \
440 -Dcf_email='yourname@yourhost.yourplace.com' \
441 -Dperladmin='yourname@yourhost.yourplace.com' \
442 -Dmydomain='.yourplace.com' \
443 -Dmyhostname='yourhost' \
446 =head2 Update Porting/config.sh and Porting/config_H
449 This section needs revision. We're currently working on easing
450 the task of keeping the vms, win32, and plan9 config.sh info
451 up-to-date. The plan is to use keep up-to-date 'canned' config.sh
452 files in the appropriate subdirectories and then generate 'canned'
453 config.h files for vms, win32, etc. from the generic config.sh file.
454 This is to ease maintenance. When Configure gets updated, the parts
455 sometimes get scrambled around, and the changes in config_H can
456 sometimes be very hard to follow. config.sh, on the other hand, can
457 safely be sorted, so it's easy to track (typically very small) changes
458 to config.sh and then propagate them to a canned 'config.h' by any
459 number of means, including a perl script in win32/ or carrying
460 config.sh and config_h.SH to a Unix system and running sh
461 config_h.SH.) Vms uses configure.com to generate its own config.sh
462 and config.h. If you want to add a new variable to config.sh check
463 with vms folk how to add it to configure.com too.
466 The Porting/config.sh and Porting/config_H files are provided to
467 help those folks who can't run Configure. It is important to keep
468 them up-to-date. If you have changed config_h.SH, those changes must
469 be reflected in config_H as well. (The name config_H was chosen to
470 distinguish the file from config.h even on case-insensitive file systems.)
471 Simply edit the existing config_H file; keep the first few explanatory
472 lines and then copy your new config.h below.
474 It may also be necessary to update win32/config.?c, and
475 plan9/config.plan9, though you should be quite careful in doing so if
476 you are not familiar with those systems. You might want to issue your
477 patch with a promise to quickly issue a follow-up that handles those
480 =head2 make regen_perly
482 If perly.y has been edited, it is necessary to run this target to rebuild
483 perly.h, perly.act and perly.tab. In fact this target just runs the Perl
484 script regen_perly.pl. Note that perly.c is I<not> rebuilt; this is just a
485 plain static file now.
487 This target relies on you having Bison installed on your system. Running
488 the target will tell you if you haven't got the right version, and if so,
489 where to get the right one. Or if you prefer, you could hack
490 regen_perly.pl to work with your version of Bison. The important things
491 are that the regexes can still extract out the right chunks of the Bison
492 output into perly.act and perly.tab, and that the contents of those two
493 files, plus perly.h, are functionally equivalent to those produced by the
494 supported version of Bison.
496 Note that in the old days, you had to do C<make run_byacc> instead.
498 =head2 make regen_all
500 This target takes care of the regen_headers, and regen_pods targets.
502 =head2 make regen_headers
504 The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically
505 generated by perl scripts. Since the user isn't guaranteed to have a
506 working perl, we can't require the user to generate them. Hence you have
507 to, if you're making a distribution.
509 I used to include rules like the following in the makefile:
511 # The following three header files are generated automatically
512 # The correct versions should be already supplied with the perl kit,
513 # in case you don't have perl or 'sh' available.
514 # The - is to ignore error return codes in case you have the source
515 # installed read-only or you don't have perl yet.
516 keywords.h: keywords.pl
517 @echo "Don't worry if this fails."
521 However, I got B<lots> of mail consisting of people worrying because the
522 command failed. I eventually decided that I would save myself time
523 and effort by manually running C<make regen_headers> myself rather
524 than answering all the questions and complaints about the failing
527 =head2 make regen_pods
529 Will run `make regen_pods` in the pod directory for indexing.
531 =head2 global.sym, interp.sym and perlio.sym
533 Make sure these files are up-to-date. Read the comments in these
534 files and in perl_exp.SH to see what to do.
536 =head2 Binary compatibility
538 If you do change F<global.sym> or F<interp.sym>, think carefully about
539 what you are doing. To the extent reasonable, we'd like to maintain
540 source and binary compatibility with older releases of perl. That way,
541 extensions built under one version of perl will continue to work with
542 new versions of perl.
544 Of course, some incompatible changes may well be necessary. I'm just
545 suggesting that we not make any such changes without thinking carefully
546 about them first. If possible, we should provide
547 backwards-compatibility stubs. There's a lot of XS code out there.
548 Let's not force people to keep changing it.
552 F<ext/Devel/PPPort/PPPort.pm> needs to be synchronized to include all
553 new macros added to .h files (normally perl.h and XSUB.h, but others
554 as well). Since chances are that when a new macro is added the
555 committer will forget to update F<PPPort.pm>, it's the best to diff for
556 changes in .h files when making a new release and making sure that
557 F<PPPort.pm> contains them all.
559 The pumpking can delegate the synchronization responsibility to anybody
560 else, but the release process is the only place where we can make sure
561 that no new macros fell through the cracks.
565 Be sure to update the F<Changes> file. Try to include both an overall
566 summary as well as detailed descriptions of the changes. Your
567 audience will include other developers and users, so describe
568 user-visible changes (if any) in terms they will understand, not in
569 code like "initialize foo variable in bar function".
571 There are differing opinions on whether the detailed descriptions
572 ought to go in the Changes file or whether they ought to be available
573 separately in the patch file (or both). There is no disagreement that
574 detailed descriptions ought to be easily available somewhere.
576 If you update the subversion number in F<patchlevel.h>, you may need
577 to change the version number near the top of the F<Changes> file.
581 The F<pod/perltodo.pod> file contains a roughly-categorized unordered
582 list of aspects of Perl that could use enhancement, features that could
583 be added, areas that could be cleaned up, and so on. During your term
584 as pumpkin-holder, you will probably address some of these issues, and
585 perhaps identify others which, while you decide not to address them this
586 time around, may be tackled in the future. Update the file to reflect
587 the situation as it stands when you hand over the pumpkin.
589 You might like, early in your pumpkin-holding career, to see if you
590 can find champions for particular issues on the to-do list: an issue
591 owned is an issue more likely to be resolved.
593 There are also some more porting-specific L</Todo> items later in this
596 =head2 OS/2-specific updates
598 In the os2 directory is F<diff.configure>, a set of OS/2-specific
599 diffs against B<Configure>. If you make changes to Configure, you may
600 want to consider regenerating this diff file to save trouble for the
603 You can also consider the OS/2 diffs as reminders of portability
604 things that need to be fixed in Configure.
606 =head2 VMS-specific updates
608 The Perl revision number appears as "perl5" in configure.com.
609 It is courteous to update that if necessary.
611 =head2 Making the new distribution
613 Suppose, for example, that you want to make version 5.004_08. Then you can
614 do something like the following
616 mkdir ../perl5.004_08
617 awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08
619 tar cf perl5.004_08.tar perl5.004_08
620 gzip --best perl5.004_08.tar
622 These steps, with extra checks, are automated by the Porting/makerel
625 =head2 Making a new patch
627 I find the F<makepatch> utility quite handy for making patches.
628 You can obtain it from any CPAN archive under
629 http://www.cpan.org/authors/Johan_Vromans/ . There are a couple
630 of differences between my version and the standard one. I have mine do
633 # Print a reassuring "End of Patch" note so people won't
634 # wonder if their mailer truncated patches.
635 print "\n\nEnd of Patch.\n";
637 at the end. That's because I used to get questions from people asking
638 if their mail was truncated.
640 It also writes Index: lines which include the new directory prefix
641 (change Index: print, approx line 294 or 310 depending on the version,
642 to read: print PATCH ("Index: $newdir$new\n");). That helps patches
643 work with more POSIX conformant patch programs.
645 Here's how I generate a new patch. I'll use the hypothetical
646 5.004_07 to 5.004_08 patch as an example.
648 # unpack perl5.004_07/
649 gzip -d -c perl5.004_07.tar.gz | tar -xof -
650 # unpack perl5.004_08/
651 gzip -d -c perl5.004_08.tar.gz | tar -xof -
652 makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat
654 Makepatch will automatically generate appropriate B<rm> commands to remove
655 deleted files. Unfortunately, it will not correctly set permissions
656 for newly created files, so you may have to do so manually. For example,
657 patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable,
658 so at the top of the patch, I inserted the following lines:
664 Now, of course, my patch is now wrong because makepatch didn't know I
665 was going to do that command, and it patched against /dev/null.
667 So, what I do is sort out all such shell commands that need to be in the
668 patch (including possible mv-ing of files, if needed) and put that in the
669 shell commands at the top of the patch. Next, I delete all the patch parts
670 of perl5.004_08.pat, leaving just the shell commands. Then, I do the
674 sh ../perl5.004_08.pat
676 makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat
678 (Note the append to preserve my shell commands.)
679 Now, my patch will line up with what the end users are going to do.
681 =head2 Testing your patch
683 It seems obvious, but be sure to test your patch. That is, verify that
684 it produces exactly the same thing as your full distribution.
687 gzip -d -c perl5.004_07.tar.gz | tar -xf -
689 sh ../perl5.004_08.pat
690 patch -p1 -N < ../perl5.004_08.pat
692 gdiff -r perl5.004_07 perl5.004_08
694 where B<gdiff> is GNU diff. Other diff's may also do recursive checking.
698 Again, it's obvious, but you should test your new version as widely as you
699 can. You can be sure you'll hear about it quickly if your version doesn't
700 work on both ANSI and pre-ANSI compilers, and on common systems such as
701 SunOS 4.1.[34], Solaris, and Linux.
703 If your changes include conditional code, try to test the different
704 branches as thoroughly as you can. For example, if your system
705 supports dynamic loading, you can also test static loading with
709 You can also hand-tweak your config.h to try out different #ifdef
716 =item gcc -ansi -pedantic
718 Configure -Dgccansipedantic [ -Dcc=gcc ] will enable (via the cflags script,
719 not $Config{ccflags}) the gcc strict ANSI C flags -ansi and -pedantic for
720 the compilation of the core files on platforms where it knows it can
721 do so (like Linux, see cflags.SH for the full list), and on some
722 platforms only one (Solaris can do only -pedantic, not -ansi).
723 The flag -DPERL_GCC_PEDANTIC also gets added, since gcc does not add
724 any internal cpp flag to signify that -pedantic is being used, as it
725 does for -ansi (__STRICT_ANSI__).
727 Note that the -ansi and -pedantic are enabled only for version 3 (and
728 later) of gcc, since even gcc version 2.95.4 finds lots of seemingly
729 false "value computed not used" errors from Perl.
731 The -ansi and -pedantic are useful in catching at least the following
732 nonportable practices:
738 gcc-specific extensions
754 The -Dgccansipedantic should be used only when cleaning up the code,
755 not for production builds, since otherwise gcc cannot inline certain
760 =head1 Running Purify
762 Purify is a commercial tool that is helpful in identifying memory
763 overruns, wild pointers, memory leaks and other such badness. Perl
764 must be compiled in a specific way for optimal testing with Purify.
766 Use the following commands to test perl with Purify:
768 sh Configure -des -Doptimize=-g -Uusemymalloc -Dusemultiplicity \
770 setenv PURIFYOPTIONS "-chain-length=25"
773 ln -s ../pureperl perl
774 setenv PERL_DESTRUCT_LEVEL 2
777 Disabling Perl's malloc allows Purify to monitor allocations and leaks
778 more closely; using Perl's malloc will make Purify report most leaks
779 in the "potential" leaks category. Enabling the multiplicity option
780 allows perl to clean up thoroughly when the interpreter shuts down, which
781 reduces the number of bogus leak reports from Purify. The -DPURIFY
782 enables any Purify-specific debugging code in the sources.
784 Purify outputs messages in "Viewer" windows by default. If you don't have
785 a windowing environment or if you simply want the Purify output to
786 unobtrusively go to a log file instead of to the interactive window,
787 use the following options instead:
789 setenv PURIFYOPTIONS "-chain-length=25 -windows=no -log-file=perl.log \
792 The only currently known leaks happen when there are compile-time errors
793 within eval or require. (Fixing these is non-trivial, unfortunately, but
794 they must be fixed eventually.)
796 =head1 Common Gotchas
800 =item Probably Prefer POSIX
802 It's often the case that you'll need to choose whether to do
803 something the BSD-ish way or the POSIX-ish way. It's usually not
804 a big problem when the two systems use different names for similar
805 functions, such as memcmp() and bcmp(). The perl.h header file
806 handles these by appropriate #defines, selecting the POSIX mem*()
807 functions if available, but falling back on the b*() functions, if
810 More serious is the case where some brilliant person decided to
811 use the same function name but give it a different meaning or
812 calling sequence :-). getpgrp() and setpgrp() come to mind.
813 These are a real problem on systems that aim for conformance to
814 one standard (e.g. POSIX), but still try to support the other way
815 of doing things (e.g. BSD). My general advice (still not really
816 implemented in the source) is to do something like the following.
817 Suppose there are two alternative versions, fooPOSIX() and
821 /* use fooPOSIX(); */
824 /* try to emulate fooPOSIX() with fooBSD();
825 perhaps with the following: */
826 # define fooPOSIX fooBSD
828 # /* Uh, oh. We have to supply our own. */
829 # define fooPOSIX Perl_fooPOSIX
833 =item Think positively
835 If you need to add an #ifdef test, it is usually easier to follow if you
836 think positively, e.g.
838 #ifdef HAS_NEATO_FEATURE
839 /* use neato feature */
841 /* use some fallback mechanism */
844 rather than the more impenetrable
846 #ifndef MISSING_NEATO_FEATURE
847 /* Not missing it, so we must have it, so use it */
849 /* Are missing it, so fall back on something else. */
852 Of course for this toy example, there's not much difference. But when
853 the #ifdef's start spanning a couple of screen fulls, and the #else's
854 are marked something like
856 #else /* !MISSING_NEATO_FEATURE */
858 I find it easy to get lost.
860 =item Providing Missing Functions -- Problem
862 Not all systems have all the neat functions you might want or need, so
863 you might decide to be helpful and provide an emulation. This is
864 sound in theory and very kind of you, but please be careful about what
865 you name the function. Let me use the C<pause()> function as an
868 Perl5.003 has the following in F<perl.h>
871 #define pause() sleep((32767<<16)+32767)
874 Configure sets HAS_PAUSE if the system has the pause() function, so
875 this #define only kicks in if the pause() function is missing.
878 Unfortunately, some systems apparently have a prototype for pause()
879 in F<unistd.h>, but don't actually have the function in the library.
880 (Or maybe they do have it in a library we're not using.)
882 Thus, the compiler sees something like
884 extern int pause(void);
886 #define pause() sleep((32767<<16)+32767)
888 and dies with an error message. (Some compilers don't mind this;
889 others apparently do.)
891 To work around this, 5.003_03 and later have the following in perl.h:
893 /* Some unistd.h's give a prototype for pause() even though
894 HAS_PAUSE ends up undefined. This causes the #define
895 below to be rejected by the compiler. Sigh.
900 # define Pause() sleep((32767<<16)+32767)
905 The curious reader may wonder why I didn't do the following in
911 sleep((32767<<16)+32767);
915 That is, since the function is missing, just provide it.
916 Then things would probably be been alright, it would seem.
918 Well, almost. It could be made to work. The problem arises from the
919 conflicting needs of dynamic loading and namespace protection.
921 For dynamic loading to work on AIX (and VMS) we need to provide a list
922 of symbols to be exported. This is done by the script F<perl_exp.SH>,
923 which reads F<global.sym> and F<interp.sym>. Thus, the C<pause>
924 symbol would have to be added to F<global.sym> So far, so good.
926 On the other hand, one of the goals of Perl5 is to make it easy to
927 either extend or embed perl and link it with other libraries. This
928 means we have to be careful to keep the visible namespace "clean".
929 That is, we don't want perl's global variables to conflict with
930 those in the other application library. Although this work is still
931 in progress, the way it is currently done is via the F<embed.h> file.
932 This file is built from the F<global.sym> and F<interp.sym> files,
933 since those files already list the globally visible symbols. If we
934 had added C<pause> to global.sym, then F<embed.h> would contain the
937 #define pause Perl_pause
939 and calls to C<pause> in the perl sources would now point to
940 C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable,
941 it will go looking for C<perl_pause>, which probably won't exist in any
942 of the standard libraries. Thus the build of perl will fail.
944 Those systems where C<HAS_PAUSE> is not defined would be ok, however,
945 since they would get a C<Perl_pause> function in util.c. The rest of
946 the world would be in trouble.
948 And yes, this scenario has happened. On SCO, the function C<chsize>
949 is available. (I think it's in F<-lx>, the Xenix compatibility
950 library.) Since the perl4 days (and possibly before), Perl has
951 included a C<chsize> function that gets called something akin to
954 I32 chsize(fd, length)
960 #define chsize Perl_chsize
962 to F<embed.h>, the compile started failing on SCO systems.
964 The "fix" is to give the function a different name. The one
965 implemented in 5.003_05 isn't optimal, but here's what was done:
968 # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */
971 # define my_chsize chsize
974 My explanatory comment in patch 5.003_05 said:
976 Undef and then re-define my_chsize from Perl_my_chsize to
977 just plain chsize if this system HAS_CHSIZE. This probably only
978 applies to SCO. This shows the perils of having internal
979 functions with the same name as external library functions :-).
981 Now, we can safely put C<my_chsize> in F<global.sym>, export it, and
982 hide it with F<embed.h>.
984 To be consistent with what I did for C<pause>, I probably should have
985 called the new function C<Chsize>, rather than C<my_chsize>.
986 However, the perl sources are quite inconsistent on this (Consider
987 New, Mymalloc, and Myremalloc, to name just a few.)
989 There is a problem with this fix, however, in that C<Perl_chsize>
990 was available as a F<libperl.a> library function in 5.003, but it
991 isn't available any more (as of 5.003_07). This means that we've
992 broken binary compatibility. This is not good.
994 =item Providing missing functions -- some ideas
996 We currently don't have a standard way of handling such missing
997 function names. Right now, I'm effectively thinking aloud about a
998 solution. Some day, I'll try to formally propose a solution.
1000 Part of the problem is that we want to have some functions listed as
1001 exported but not have their names mangled by embed.h or possibly
1002 conflict with names in standard system headers. We actually already
1003 have such a list at the end of F<perl_exp.SH> (though that list is
1006 # extra globals not included above.
1007 cat <<END >> perl.exp
1031 This still needs much thought, but I'm inclined to think that one
1032 possible solution is to prefix all such functions with C<perl_> in the
1033 source and list them along with the other C<perl_*> functions in
1036 Thus, for C<chsize>, we'd do something like the following:
1040 # define perl_chsize chsize
1043 then in some file (e.g. F<util.c> or F<doio.c>) do
1046 I32 perl_chsize(fd, length)
1047 /* implement the function here . . . */
1050 Alternatively, we could just always use C<chsize> everywhere and move
1051 C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would
1052 probably be fine as long as our C<chsize> function agreed with all the
1053 C<chsize> function prototypes in the various systems we'll be using.
1054 As long as the prototypes in actual use don't vary that much, this is
1055 probably a good alternative. (As a counter-example, note how Configure
1056 and perl have to go through hoops to find and use get Malloc_t and
1057 Free_t for C<malloc> and C<free>.)
1059 At the moment, this latter option is what I tend to prefer.
1061 =item All the world's a VAX
1063 Sorry, showing my age:-). Still, all the world is not BSD 4.[34],
1064 SVR4, or POSIX. Be aware that SVR3-derived systems are still quite
1065 common (do you have any idea how many systems run SCO?) If you don't
1066 have a bunch of v7 manuals handy, the metaconfig units (by default
1067 installed in F</usr/local/lib/dist/U>) are a good resource to look at
1072 =head1 Miscellaneous Topics
1076 Why does perl use a metaconfig-generated Configure script instead of an
1077 autoconf-generated configure script?
1079 Metaconfig and autoconf are two tools with very similar purposes.
1080 Metaconfig is actually the older of the two, and was originally written
1081 by Larry Wall, while autoconf is probably now used in a wider variety of
1082 packages. The autoconf info file discusses the history of autoconf and
1083 how it came to be. The curious reader is referred there for further
1086 Overall, both tools are quite good, I think, and the choice of which one
1087 to use could be argued either way. In March, 1994, when I was just
1088 starting to work on Configure support for Perl5, I considered both
1089 autoconf and metaconfig, and eventually decided to use metaconfig for the
1094 =item Compatibility with Perl4
1096 Perl4 used metaconfig, so many of the #ifdef's were already set up for
1097 metaconfig. Of course metaconfig had evolved some since Perl4's days,
1098 but not so much that it posed any serious problems.
1100 =item Metaconfig worked for me
1102 My system at the time was Interactive 2.2, an SVR3.2/386 derivative that
1103 also had some POSIX support. Metaconfig-generated Configure scripts
1104 worked fine for me on that system. On the other hand, autoconf-generated
1105 scripts usually didn't. (They did come quite close, though, in some
1106 cases.) At the time, I actually fetched a large number of GNU packages
1107 and checked. Not a single one configured and compiled correctly
1108 out-of-the-box with the system's cc compiler.
1110 =item Configure can be interactive
1112 With both autoconf and metaconfig, if the script works, everything is
1113 fine. However, one of my main problems with autoconf-generated scripts
1114 was that if it guessed wrong about something, it could be B<very> hard to
1115 go back and fix it. For example, autoconf always insisted on passing the
1116 -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I
1117 wanted or needed for that package. There was no way short of editing the
1118 configure script to turn this off. You couldn't just edit the resulting
1119 Makefile at the end because the -Xp flag influenced a number of other
1122 Metaconfig's Configure scripts, on the other hand, can be interactive.
1123 Thus if Configure is guessing things incorrectly, you can go back and fix
1124 them. This isn't as important now as it was when we were actively
1125 developing Configure support for new features such as dynamic loading,
1126 but it's still useful occasionally.
1130 At the time, autoconf-generated scripts were covered under the GNU Public
1131 License, and hence weren't suitable for inclusion with Perl, which has a
1132 different licensing policy. (Autoconf's licensing has since changed.)
1136 Metaconfig builds up Configure from a collection of discrete pieces
1137 called "units". You can override the standard behavior by supplying your
1138 own unit. With autoconf, you have to patch the standard files instead.
1139 I find the metaconfig "unit" method easier to work with. Others
1140 may find metaconfig's units clumsy to work with.
1144 =head2 Why isn't there a directory to override Perl's library?
1146 Mainly because no one's gotten around to making one. Note that
1147 "making one" involves changing perl.c, Configure, config_h.SH (and
1148 associated files, see above), and I<documenting> it all in the
1151 Apparently, most folks who want to override one of the standard library
1152 files simply do it by overwriting the standard library files.
1156 In the perl.c sources, you'll find an undocumented APPLLIB_EXP
1157 variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are
1158 documented in config_h.SH). Here's what APPLLIB_EXP is for, from
1159 a mail message from Larry:
1161 The main intent of APPLLIB_EXP is for folks who want to send out a
1162 version of Perl embedded in their product. They would set the symbol
1163 to be the name of the library containing the files needed to run or to
1164 support their particular application. This works at the "override"
1165 level to make sure they get their own versions of any library code that
1166 they absolutely must have configuration control over.
1168 As such, I don't see any conflict with a sysadmin using it for a
1169 override-ish sort of thing, when installing a generic Perl. It should
1170 probably have been named something to do with overriding though. Since
1171 it's undocumented we could still change it... :-)
1173 Given that it's already there, you can use it to override distribution modules.
1174 One way to do that is to add
1176 ccflags="$ccflags -DAPPLLIB_EXP=\"/my/override\""
1178 to your config.over file. (You have to be particularly careful to get the
1179 double quotes in. APPLLIB_EXP must be a valid C string. It might
1180 actually be easier to just #define it yourself in perl.c.)
1182 Then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB. Perl will
1183 also search architecture-specific and version-specific subdirectories of
1186 =head2 Shared libperl.so location
1188 Why isn't the shared libperl.so installed in /usr/lib/ along
1189 with "all the other" shared libraries? Instead, it is installed
1190 in $archlib, which is typically something like
1192 /usr/local/lib/perl5/archname/5.00404
1194 and is architecture- and version-specific.
1196 The basic reason why a shared libperl.so gets put in $archlib is so that
1197 you can have more than one version of perl on the system at the same time,
1198 and have each refer to its own libperl.so.
1200 Three examples might help. All of these work now; none would work if you
1201 put libperl.so in /usr/lib.
1207 Suppose you want to have both threaded and non-threaded perl versions
1208 around. Configure will name both perl libraries "libperl.so" (so that
1209 you can link to them with -lperl). The perl binaries tell them apart
1210 by having looking in the appropriate $archlib directories.
1214 Suppose you have perl5.004_04 installed and you want to try to compile
1215 it again, perhaps with different options or after applying a patch.
1216 If you already have libperl.so installed in /usr/lib/, then it may be
1217 either difficult or impossible to get ld.so to find the new libperl.so
1218 that you're trying to build. If, instead, libperl.so is tucked away in
1219 $archlib, then you can always just change $archlib in the current perl
1220 you're trying to build so that ld.so won't find your old libperl.so.
1221 (The INSTALL file suggests you do this when building a debugging perl.)
1225 The shared perl library is not a "well-behaved" shared library with
1226 proper major and minor version numbers, so you can't necessarily
1227 have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose
1228 perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05
1229 were to install /usr/lib/libperl.so.4.5. Now, when you try to run
1230 perl5.004_04, ld.so might try to load libperl.so.4.5, since it has
1231 the right "major version" number. If this works at all, it almost
1232 certainly defeats the reason for keeping perl5.004_04 around. Worse,
1233 with development subversions, you certaily can't guarantee that
1234 libperl.so.4.4 and libperl.so.4.55 will be compatible.
1236 Anyway, all this leads to quite obscure failures that are sure to drive
1237 casual users crazy. Even experienced users will get confused :-). Upon
1238 reflection, I'd say leave libperl.so in $archlib.
1242 =head2 Indentation style
1244 Over the years Perl has become a mishmash of
1245 various indentation styles, but the original "Larry style" can
1246 probably be restored with (GNU) indent somewhat like this:
1248 indent -kr -nce -psl -sc
1250 A more ambitious solution would also specify a list of Perl specific
1251 types with -TSV -TAV -THV .. -TMAGIC -TPerlIO ... but that list would
1252 be quite ungainly. Also note that GNU indent also doesn't do aligning
1253 of consecutive assignments, which would truly wreck the layout in
1254 places like sv.c:Perl_sv_upgrade() or sv.c:Perl_clone_using().
1255 Similarly nicely aligned &&s, ||s and ==s would not be respected.
1257 =head1 Upload Your Work to CPAN
1259 You can upload your work to CPAN if you have a CPAN id. Check out
1260 http://www.cpan.org/modules/04pause.html for information on
1261 _PAUSE_, the Perl Author's Upload Server.
1263 I typically upload both the patch file, e.g. F<perl5.004_08.pat.gz>
1264 and the full tar file, e.g. F<perl5.004_08.tar.gz>.
1266 If you want your patch to appear in the F<src/5.0/unsupported>
1267 directory on CPAN, send e-mail to the CPAN master librarian. (Check
1268 out http://www.cpan.org/CPAN.html ).
1270 =head1 Help Save the World
1272 You should definitely announce your patch on the perl5-porters list.
1273 You should also consider announcing your patch on
1274 comp.lang.perl.announce, though you should make it quite clear that a
1275 subversion is not a production release, and be prepared to deal with
1276 people who will not read your disclaimer.
1280 Here, in no particular order, are some Configure and build-related
1281 items that merit consideration. This list isn't exhaustive, it's just
1282 what I came up with off the top of my head.
1284 =head2 Adding missing library functions to Perl
1286 The perl Configure script automatically determines which headers and
1287 functions you have available on your system and arranges for them to be
1288 included in the compilation and linking process. Occasionally, when porting
1289 perl to an operating system for the first time, you may find that the
1290 operating system is missing a key function. While perl may still build
1291 without this function, no perl program will be able to reference the missing
1292 function. You may be able to write the missing function yourself, or you
1293 may be able to find the missing function in the distribution files for
1294 another software package. In this case, you need to instruct the perl
1295 configure-and-build process to use your function. Perform these steps.
1301 Code and test the function you wish to add. Test it carefully; you will
1302 have a much easier time debugging your code independently than when it is a
1307 Here is an implementation of the POSIX truncate function for an operating
1308 system (VOS) that does not supply one, but which does supply the ftruncate()
1311 /* Beginning of modification history */
1312 /* Written 02-01-02 by Nick Ing-Simmons (nick@ing-simmons.net) */
1313 /* End of modification history */
1315 /* VOS doesn't supply a truncate function, so we build one up
1316 from the available POSIX functions. */
1319 #include <sys/types.h>
1323 truncate(const char *path, off_t len)
1325 int fd = open(path,O_WRONLY);
1328 code = ftruncate(fd,len);
1334 Place this file into a subdirectory that has the same name as the operating
1335 system. This file is named perl/vos/vos.c
1339 If your operating system has a hints file (in perl/hints/XXX.sh for an
1340 operating system named XXX), then start with it. If your operating system
1341 has no hints file, then create one. You can use a hints file for a similar
1342 operating system, if one exists, as a template.
1346 Add lines like the following to your hints file. The first line
1347 (d_truncate="define") instructs Configure that the truncate() function
1348 exists. The second line (archobjs="vos.o") instructs the makefiles that the
1349 perl executable depends on the existence of a file named "vos.o". (Make
1350 will automatically look for "vos.c" and compile it with the same options as
1351 the perl source code). The final line ("test -h...") adds a symbolic link
1352 to the top-level directory so that make can find vos.c. Of course, you
1353 should use your own operating system name for the source file of extensions,
1356 # VOS does not have truncate() but we supply one in vos.c
1360 # Help gmake find vos.c
1361 test -h vos.c || ln -s vos/vos.c vos.c
1363 The hints file is a series of shell commands that are run in the top-level
1364 directory (the "perl" directory). Thus, these commands are simply executed
1365 by Configure at an appropriate place during its execution.
1369 At this point, you can run the Configure script and rebuild perl. Carefully
1370 test the newly-built perl to ensure that normal paths, and error paths,
1371 behave as you expect.
1375 =head2 Good ideas waiting for round tuits
1379 =item Configure -Dsrc=/blah/blah
1381 We should be able to emulate B<configure --srcdir>. Tom Tromey
1382 tromey@creche.cygnus.com has submitted some patches to
1383 the dist-users mailing list along these lines. They have been folded
1384 back into the main distribution, but various parts of the perl
1385 Configure/build/install process still assume src='.'.
1387 =item Hint file fixes
1389 Various hint files work around Configure problems. We ought to fix
1390 Configure so that most of them aren't needed.
1392 =item Hint file information
1394 Some of the hint file information (particularly dynamic loading stuff)
1395 ought to be fed back into the main metaconfig distribution.
1399 =head2 Probably good ideas waiting for round tuits
1403 =item GNU configure --options
1405 I've received sensible suggestions for --exec_prefix and other
1406 GNU configure --options. It's not always obvious exactly what is
1407 intended, but this merits investigation.
1411 Currently, B<make clean> isn't all that useful, though
1412 B<make realclean> and B<make distclean> are. This needs a bit of
1413 thought and documentation before it gets cleaned up.
1415 =item Try gcc if cc fails
1417 Currently, we just give up.
1419 =item bypassing safe*alloc wrappers
1421 On some systems, it may be safe to call the system malloc directly
1422 without going through the util.c safe* layers. (Such systems would
1423 accept free(0), for example.) This might be a time-saver for systems
1424 that already have a good malloc. (Recent Linux libc's apparently have
1425 a nice malloc that is well-tuned for the system.)
1429 =head2 Vague possibilities
1435 Get some of the Macintosh stuff folded back into the main distribution.
1437 =item gconvert replacement
1439 Maybe include a replacement function that doesn't lose data in rare
1440 cases of coercion between string and numerical values.
1442 =item Improve makedepend
1444 The current makedepend process is clunky and annoyingly slow, but it
1445 works for most folks. Alas, it assumes that there is a filename
1446 $firstmakefile that the B<make> command will try to use before it uses
1447 F<Makefile>. Such may not be the case for all B<make> commands,
1448 particularly those on non-Unix systems.
1450 Probably some variant of the BSD F<.depend> file will be useful.
1451 We ought to check how other packages do this, if they do it at all.
1452 We could probably pre-generate the dependencies (with the exception of
1453 malloc.o, which could probably be determined at F<Makefile.SH>
1456 =item GNU Makefile standard targets
1458 GNU software generally has standardized Makefile targets. Unless we
1459 have good reason to do otherwise, I see no reason not to support them.
1463 Somehow, straighten out, document, and implement lockf(), flock(),
1464 and/or fcntl() file locking. It's a mess. See $d_fcntl_can_lock
1465 in recent config.sh files though.
1469 =head2 Copyright Issues
1471 The following is based on the consensus of a couple of IPR lawyers,
1472 but it is of course not a legally binding statement, just a common
1479 Tacking on copyright statements is unnecessary to begin with because
1480 of the Berne convention. But assuming you want to go ahead...
1484 The right form of a copyright statement is
1486 Copyright (C) Year, Year, ... by Someone
1488 The (C) is not required everywhere but it doesn't hurt and in certain
1489 jurisdictions it is required, so let's leave it in. (Yes, it's true
1490 that in some jurisdictions the "(C)" is not legally binding, one should
1491 use the true ringed-C. But we don't have that character available for
1492 Perl's source code.)
1494 The years must be listed out separately. Year-Year is not correct.
1495 Only the years when the piece has changed 'significantly' may be added.
1499 One cannot give away one's copyright trivially. One can give one's
1500 copyright away by using public domain, but even that requires a little
1501 bit more than just saying 'this is in public domain'. (What it
1502 exactly requires depends on your jurisdiction.) But barring public
1503 domain, one cannot "transfer" one's copyright to another person or
1504 entity. In the context of software, it means that contributors cannot
1505 give away their copyright or "transfer" it to the "owner" of the software.
1507 Also remember that in many cases if you are employed by someone,
1508 your work may be copyrighted to your employer, even when you are
1509 contributing on your own time (this all depends on too many things
1510 to list here). But the bottom line is that you definitely can't give
1511 away a copyright you may not even have.
1513 What is possible, however, is that the software can simply state
1515 Copyright (C) Year, Year, ... by Someone and others
1517 and then list the "others" somewhere in the distribution.
1518 And this is exactly what Perl does. (The "somewhere" is
1519 AUTHORS and the Changes* files.)
1523 Split files, merged files, and generated files are problematic.
1524 The rule of thumb: in split files, copy the copyright years of
1525 the original file to all the new files; in merged files make
1526 an union of the copyright years of all the old files; in generated
1527 files propagate the copyright years of the generating file(s).
1531 The files of Perl source code distribution do carry a lot of
1532 copyrights, by various people. (There are many copyrights embedded in
1533 perl.c, for example.) The most straightforward thing for pumpkings to
1534 do is to simply update Larry's copyrights at the beginning of the
1535 *.[hcy], x2p/*.[hcy], *.pl, and README files, and leave all other
1536 copyrights alone. Doing more than that requires quite a bit of tracking.
1542 Original author: Andy Dougherty doughera@lafayette.edu .
1543 Additions by Chip Salzenberg chip@perl.com and
1544 Tim Bunce Tim.Bunce@ig.co.uk .
1546 All opinions expressed herein are those of the authorZ<>(s).
1548 =head1 LAST MODIFIED
1550 $Id: pumpkin.pod,v 1.23 2000/01/13 19:45:13 doughera Released $