3 Pumpkin - Notes on handling the Perl Patch Pumpkin
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.rosat.mpe-garching.mpg.de/mailing-lists/perl-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 pumkings 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.
163 =head2 Seek consensus on major changes
165 If you are making big changes, don't do it in secret. Discuss the
166 ideas in advance on perl5-porters.
168 =head2 Keep the documentation up-to-date
170 If your changes may affect how users use perl, then check to be sure
171 that the documentation is in sync with your changes. Be sure to
172 check all the files F<pod/*.pod> and also the F<INSTALL> document.
174 Consider writing the appropriate documentation first and then
175 implementing your change to correspond to the documentation.
177 =head2 Avoid machine-specific #ifdef's
179 To the extent reasonable, try to avoid machine-specific #ifdef's in
180 the sources. Instead, use feature-specific #ifdef's. The reason is
181 that the machine-specific #ifdef's may not be valid across major
182 releases of the operating system. Further, the feature-specific tests
183 may help out folks on another platform who have the same problem.
185 =head2 Machine-specific files
191 If you have many machine-specific #defines or #includes, consider
192 creating an "osish.h" (os2ish.h, vmsish.h, and so on) and including
193 that in perl.h. If you have several machine-specific files (function
194 emulations, function stubs, build utility wrappers) you may create a
195 separate subdirectory (djgpp, win32) and put the files in there.
196 Remember to update C<MANIFEST> when you add files.
198 If your system supports dynamic loading but none of the existing
199 methods at F<ext/DynaLoader/dl_*.xs> work for you, you must write
200 a new one. Study the existing ones to see what kind of interface
205 There are two kinds of hints: hints for building Perl and hints for
206 extensions. The former live in the C<hints> subdirectory, the latter
207 in C<ext/*/hints> subdirectories.
209 The top level hints are Bourne-shell scripts that set, modify and
210 unset appropriate Configure variables, based on the Configure command
211 line options and possibly existing config.sh and Policy.sh files from
212 previous Configure runs.
214 The extension hints are written in Perl (by the time they are used
215 miniperl has been built) and control the building of their respective
216 extensions. They can be used to for example manipulate compilation
219 =item build and installation Makefiles, scripts, and so forth
221 Sometimes you will also need to tweak the Perl build and installation
222 procedure itself, like for example F<Makefile.SH> and F<installperl>.
223 Tread very carefully, even more than usual. Contain your changes
228 Many of the tests in C<t> subdirectory assume machine-specific things
229 like existence of certain functions, something about filesystem
230 semantics, certain external utilities and their error messages. Use
231 the C<$^O> and the C<Config> module (which contains the results of the
232 Configure run, in effect the C<config.sh> converted to Perl) to either
233 skip (preferably not) or customize (preferable) the tests for your
238 Certain standard modules may need updating if your operating system
239 sports for example a native filesystem naming. You may want to update
240 some or all of the modules File::Basename, File::Spec, File::Path, and
241 File::Copy to become aware of your native filesystem syntax and
244 Remember to have a $VERSION in the modules. You can use the
245 Porting/checkVERSION.pl script for checking this.
249 If your operating system comes from outside UNIX you almost certainly
250 will have differences in the available operating system functionality
251 (missing system calls, different semantics, whatever). Please
252 document these at F<pod/perlport.pod>. If your operating system is
253 the first B<not> to have a system call also update the list of
254 "portability-bewares" at the beginning of F<pod/perlfunc.pod>.
256 A file called F<README.youros> at the top level that explains things
257 like how to install perl at this platform, where to get any possibly
258 required additional software, and for example what test suite errors
259 to expect, is nice too. Such files are in the process of being written
260 in pod format and will eventually be renamed F<INSTALL.youros>.
262 You may also want to write a separate F<.pod> file for your operating
263 system to tell about existing mailing lists, os-specific modules,
264 documentation, whatever. Please name these along the lines of
265 F<perl>I<youros>.pod. [unfinished: where to put this file (the pod/
266 subdirectory, of course: but more importantly, which/what index files
271 =head2 Allow for lots of testing
273 We should never release a main version without testing it as a
276 =head2 Test popular applications and modules.
278 We should never release a main version without testing whether or not
279 it breaks various popular modules and applications. A partial list of
280 such things would include majordomo, metaconfig, apache, Tk, CGI,
281 libnet, and libwww, to name just a few. Of course it's quite possible
282 that some of those things will be just plain broken and need to be fixed,
283 but, in general, we ought to try to avoid breaking widely-installed
286 =head2 Automated generation of derivative files
288 The F<embed.h>, F<keywords.h>, F<opcode.h>, and F<perltoc.pod> files
289 are all automatically generated by perl scripts. In general, don't
290 patch these directly; patch the data files instead.
292 F<Configure> and F<config_h.SH> are also automatically generated by
293 B<metaconfig>. In general, you should patch the metaconfig units
294 instead of patching these files directly. However, very minor changes
295 to F<Configure> may be made in between major sync-ups with the
296 metaconfig units, which tends to be complicated operations. But be
297 careful, this can quickly spiral out of control. Running metaconfig
300 Also F<Makefile> is automatically produced from F<Makefile.SH>.
301 In general, look out for all F<*.SH> files.
303 Finally, the sample files in the F<Porting/> subdirectory are
304 generated automatically by the script F<U/mksample> included
305 with the metaconfig units. See L<"run metaconfig"> below for
306 information on obtaining the metaconfig units.
308 =head1 How to Make a Distribution
310 There really ought to be a 'make dist' target, but there isn't.
311 The 'dist' suite of tools also contains a number of tools that I haven't
312 learned how to use yet. Some of them may make this all a bit easier.
314 Here are the steps I go through to prepare a patch & distribution.
316 Lots of it could doubtless be automated but isn't. The Porting/makerel
317 (make release) perl script does now help automate some parts of it.
319 =head2 Announce your intentions
321 First, you should volunteer out loud to take the patch pumpkin. It's
322 generally counter-productive to have multiple people working in secret
325 At the same time, announce what you plan to do with the patch pumpkin,
326 to allow folks a chance to object or suggest alternatives, or do it for
327 you. Naturally, the patch pumpkin holder ought to incorporate various
328 bug fixes and documentation improvements that are posted while he or
329 she has the pumpkin, but there might also be larger issues at stake.
331 One of the precepts of the subversion idea is that we shouldn't give
332 the patch pumpkin to anyone unless we have some idea what he or she
333 is going to do with it.
335 =head2 refresh pod/perltoc.pod
337 Presumably, you have done a full C<make> in your working source
338 directory. Before you C<make spotless> (if you do), and if you have
339 changed any documentation in any module or pod file, change to the
340 F<pod> directory and run C<make toc>.
342 =head2 run installhtml to check the validity of the pod files
344 =head2 update patchlevel.h
346 Don't be shy about using the subversion number, even for a relatively
347 modest patch. We've never even come close to using all 99 subversions,
348 and it's better to have a distinctive number for your patch. If you
349 need feedback on your patch, go ahead and issue it and promise to
350 incorporate that feedback quickly (e.g. within 1 week) and send out a
353 =head2 run metaconfig
355 If you need to make changes to Configure or config_h.SH, it may be best to
356 change the appropriate metaconfig units instead, and regenerate Configure.
360 will regenerate Configure and config_h.SH. Much more information
361 on obtaining and running metaconfig is in the F<U/README> file
362 that comes with Perl's metaconfig units. Perl's metaconfig units
363 should be available on CPAN. A set of units that will work with
364 perl5.005 is in the file F<mc_units-5.005_00-01.tar.gz> under
365 http://www.cpan.org/authors/id/ANDYD/ . The mc_units tar file
366 should be unpacked in your main perl source directory. Note: those
367 units were for use with 5.005. There may have been changes since then.
368 Check for later versions or contact perl5-porters@perl.org to obtain a
369 pointer to the current version.
371 Alternatively, do consider if the F<*ish.h> files might be a better
372 place for your changes.
376 Make sure the MANIFEST is up-to-date. You can use dist's B<manicheck>
377 program for this. You can also use
379 perl -w -MExtUtils::Manifest=fullcheck -e fullcheck
381 Both commands will also list extra files in the directory that are not
384 The MANIFEST is normally sorted.
386 If you are using metaconfig to regenerate Configure, then you should note
387 that metaconfig actually uses MANIFEST.new, so you want to be sure
388 MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new
389 distinction particularly useful, but that's probably because I still haven't
390 learned how to use the full suite of tools in the dist distribution.
392 =head2 Check permissions
394 All the tests in the t/ directory ought to be executable. The
395 main makefile used to do a 'chmod t/*/*.t', but that resulted in
396 a self-modifying distribution--something some users would strongly
397 prefer to avoid. The F<t/TEST> script will check for this
398 and do the chmod if needed, but the tests still ought to be
401 In all, the following files should probably be executable:
416 vms/ext/Stdio/test.pl
420 Other things ought to be readable, at least :-).
422 Probably, the permissions for the files could be encoded in MANIFEST
423 somehow, but I'm reluctant to change MANIFEST itself because that
424 could break old scripts that use MANIFEST.
426 I seem to recall that some SVR3 systems kept some sort of file that listed
427 permissions for system files; something like that might be appropriate.
431 This will build a config.sh and config.h. You can skip this if you haven't
432 changed Configure or config_h.SH at all. I use the following command
434 sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \
436 -Dcf_email='yourname@yourhost.yourplace.com' \
437 -Dperladmin='yourname@yourhost.yourplace.com' \
438 -Dmydomain='.yourplace.com' \
439 -Dmyhostname='yourhost' \
442 =head2 Update Porting/config.sh and Porting/config_H
445 This section needs revision. We're currently working on easing
446 the task of keeping the vms, win32, and plan9 config.sh info
447 up-to-date. The plan is to use keep up-to-date 'canned' config.sh
448 files in the appropriate subdirectories and then generate 'canned'
449 config.h files for vms, win32, etc. from the generic config.sh file.
450 This is to ease maintenance. When Configure gets updated, the parts
451 sometimes get scrambled around, and the changes in config_H can
452 sometimes be very hard to follow. config.sh, on the other hand, can
453 safely be sorted, so it's easy to track (typically very small) changes
454 to config.sh and then propoagate them to a canned 'config.h' by any
455 number of means, including a perl script in win32/ or carrying
456 config.sh and config_h.SH to a Unix system and running sh
457 config_h.SH.) Vms uses configure.com to generate its own config.sh
458 and config.h. If you want to add a new variable to config.sh check
459 with vms folk how to add it to configure.com too.
462 The Porting/config.sh and Porting/config_H files are provided to
463 help those folks who can't run Configure. It is important to keep
464 them up-to-date. If you have changed config_h.SH, those changes must
465 be reflected in config_H as well. (The name config_H was chosen to
466 distinguish the file from config.h even on case-insensitive file systems.)
467 Simply edit the existing config_H file; keep the first few explanatory
468 lines and then copy your new config.h below.
470 It may also be necessary to update win32/config.?c, and
471 plan9/config.plan9, though you should be quite careful in doing so if
472 you are not familiar with those systems. You might want to issue your
473 patch with a promise to quickly issue a follow-up that handles those
476 =head2 make run_byacc
478 If you have byacc-1.8.2 (available from CPAN), and if there have been
479 changes to F<perly.y>, you can regenerate the F<perly.c> file. The
480 run_byacc makefile target does this by running byacc and then applying
481 some patches so that byacc dynamically allocates space, rather than
482 having fixed limits. This patch is handled by the F<perly.fixer>
483 script. Depending on the nature of the changes to F<perly.y>, you may
484 or may not have to hand-edit the patch to apply correctly. If you do,
485 you should include the edited patch in the new distribution. If you
486 have byacc-1.9, the patch won't apply cleanly. Changes to the printf
487 output statements mean the patch won't apply cleanly. Long ago I
488 started to fix F<perly.fixer> to detect this, but I never completed the
491 If C<perly.c> or C<perly.h> changes, make sure you run C<perl vms/vms_yfix.pl>
492 to update the corresponding VMS files. This could be taken care of by
493 the regen_all target in the Unix Makefile. See also
494 L<VMS-specific updates>.
496 Some additional notes from Larry on this:
498 Don't forget to regenerate perly_c.diff.
502 patch perly.c <perly_c.diff
503 # manually apply any failed hunks
504 diff -c2 perly.c.orig perly.c >perly_c.diff
506 One chunk of lines that often fails begins with
510 and ends one line before
512 #define YYERRCODE 256
514 This only happens when you add or remove a token type. I suppose this
515 could be automated, but it doesn't happen very often nowadays.
519 =head2 make regen_all
521 This target takes care of the PERLYVMS, regen_headers, and regen_pods
524 =head2 make regen_headers
526 The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically
527 generated by perl scripts. Since the user isn't guaranteed to have a
528 working perl, we can't require the user to generate them. Hence you have
529 to, if you're making a distribution.
531 I used to include rules like the following in the makefile:
533 # The following three header files are generated automatically
534 # The correct versions should be already supplied with the perl kit,
535 # in case you don't have perl or 'sh' available.
536 # The - is to ignore error return codes in case you have the source
537 # installed read-only or you don't have perl yet.
538 keywords.h: keywords.pl
539 @echo "Don't worry if this fails."
543 However, I got B<lots> of mail consisting of people worrying because the
544 command failed. I eventually decided that I would save myself time
545 and effort by manually running C<make regen_headers> myself rather
546 than answering all the questions and complaints about the failing
549 =head2 make regen_pods
551 Will run `make regen_pods` in the pod directory for indexing.
553 =head2 global.sym, interp.sym and perlio.sym
555 Make sure these files are up-to-date. Read the comments in these
556 files and in perl_exp.SH to see what to do.
558 =head2 Binary compatibility
560 If you do change F<global.sym> or F<interp.sym>, think carefully about
561 what you are doing. To the extent reasonable, we'd like to maintain
562 source and binary compatibility with older releases of perl. That way,
563 extensions built under one version of perl will continue to work with
564 new versions of perl.
566 Of course, some incompatible changes may well be necessary. I'm just
567 suggesting that we not make any such changes without thinking carefully
568 about them first. If possible, we should provide
569 backwards-compatibility stubs. There's a lot of XS code out there.
570 Let's not force people to keep changing it.
574 Be sure to update the F<Changes> file. Try to include both an overall
575 summary as well as detailed descriptions of the changes. Your
576 audience will include other developers and users, so describe
577 user-visible changes (if any) in terms they will understand, not in
578 code like "initialize foo variable in bar function".
580 There are differing opinions on whether the detailed descriptions
581 ought to go in the Changes file or whether they ought to be available
582 separately in the patch file (or both). There is no disagreement that
583 detailed descriptions ought to be easily available somewhere.
587 The F<Todo> file contains a roughly-catgorized unordered list of
588 aspects of Perl that could use enhancement, features that could be
589 added, areas that could be cleaned up, and so on. During your term as
590 pumpkin-holder, you will probably address some of these issues, and
591 perhaps identify others which, while you decide not to address them
592 this time around, may be tackled in the future. Update the file
593 reflect the situation as it stands when you hand over the pumpkin.
595 You might like, early in your pumpkin-holding career, to see if you
596 can find champions for partiticular issues on the to-do list: an issue
597 owned is an issue more likely to be resolved.
599 There are also some more porting-specific L<Todo> items later in this
602 =head2 OS/2-specific updates
604 In the os2 directory is F<diff.configure>, a set of OS/2-specific
605 diffs against B<Configure>. If you make changes to Configure, you may
606 want to consider regenerating this diff file to save trouble for the
609 You can also consider the OS/2 diffs as reminders of portability
610 things that need to be fixed in Configure.
612 =head2 VMS-specific updates
614 If you have changed F<perly.y> or F<perly.c>, then you most probably want
615 to update F<vms/perly_{h,c}.vms> by running C<perl vms/vms_yfix.pl>, or
616 by running `make regen_all` which will run that script for you.
618 The Perl revision number appears as "perl5" in configure.com.
619 It is courteous to update that if necessary.
621 =head2 Making the new distribution
623 Suppose, for example, that you want to make version 5.004_08. Then you can
624 do something like the following
626 mkdir ../perl5.004_08
627 awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08
629 tar cf perl5.004_08.tar perl5.004_08
630 gzip --best perl5.004_08.tar
632 These steps, with extra checks, are automated by the Porting/makerel
635 =head2 Making a new patch
637 I find the F<makepatch> utility quite handy for making patches.
638 You can obtain it from any CPAN archive under
639 http://www.cpan.org/authors/Johan_Vromans/ . There are a couple
640 of differences between my version and the standard one. I have mine do
643 # Print a reassuring "End of Patch" note so people won't
644 # wonder if their mailer truncated patches.
645 print "\n\nEnd of Patch.\n";
647 at the end. That's because I used to get questions from people asking
648 if their mail was truncated.
650 It also writes Index: lines which include the new directory prefix
651 (change Index: print, approx line 294 or 310 depending on the version,
652 to read: print PATCH ("Index: $newdir$new\n");). That helps patches
653 work with more POSIX conformant patch programs.
655 Here's how I generate a new patch. I'll use the hypothetical
656 5.004_07 to 5.004_08 patch as an example.
658 # unpack perl5.004_07/
659 gzip -d -c perl5.004_07.tar.gz | tar -xof -
660 # unpack perl5.004_08/
661 gzip -d -c perl5.004_08.tar.gz | tar -xof -
662 makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat
664 Makepatch will automatically generate appropriate B<rm> commands to remove
665 deleted files. Unfortunately, it will not correctly set permissions
666 for newly created files, so you may have to do so manually. For example,
667 patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable,
668 so at the top of the patch, I inserted the following lines:
674 Now, of course, my patch is now wrong because makepatch didn't know I
675 was going to do that command, and it patched against /dev/null.
677 So, what I do is sort out all such shell commands that need to be in the
678 patch (including possible mv-ing of files, if needed) and put that in the
679 shell commands at the top of the patch. Next, I delete all the patch parts
680 of perl5.004_08.pat, leaving just the shell commands. Then, I do the
684 sh ../perl5.004_08.pat
686 makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat
688 (Note the append to preserve my shell commands.)
689 Now, my patch will line up with what the end users are going to do.
691 =head2 Testing your patch
693 It seems obvious, but be sure to test your patch. That is, verify that
694 it produces exactly the same thing as your full distribution.
697 gzip -d -c perl5.004_07.tar.gz | tar -xf -
699 sh ../perl5.004_08.pat
700 patch -p1 -N < ../perl5.004_08.pat
702 gdiff -r perl5.004_07 perl5.004_08
704 where B<gdiff> is GNU diff. Other diff's may also do recursive checking.
708 Again, it's obvious, but you should test your new version as widely as you
709 can. You can be sure you'll hear about it quickly if your version doesn't
710 work on both ANSI and pre-ANSI compilers, and on common systems such as
711 SunOS 4.1.[34], Solaris, and Linux.
713 If your changes include conditional code, try to test the different
714 branches as thoroughly as you can. For example, if your system
715 supports dynamic loading, you can also test static loading with
719 You can also hand-tweak your config.h to try out different #ifdef
728 To test the correct use of printf-style arguments, C<Configure> with
729 S<-Dccflags='-DCHECK_FORMAT -Wformat'> and run C<make>. The compiler
730 will produce warning of incorrect use of format arguments. CHECK_FORMAT
731 changes perl-defined formats to common formats, so DO NOT USE the executable
732 produced by this process.
734 A more accurate approach is the following commands:
740 build miniperl with -DCHECK_FORMAT
743 make miniperl OPTIMIZE=-DCHECK_FORMAT >& mini.log
747 build a clean miniperl,
748 and build everything else from that with -DCHECK_FORMAT
752 make all OPTIMIZE=-DCHECK_FORMAT >& make.log
756 clean up, and print warnings from the log files
759 perl -nwe 'print if /^\S+:/ and not /^make\b/' \
764 (-Wformat support by Robin Barker.)
768 =head1 Running Purify
770 Purify is a commercial tool that is helpful in identifying memory
771 overruns, wild pointers, memory leaks and other such badness. Perl
772 must be compiled in a specific way for optimal testing with Purify.
774 Use the following commands to test perl with Purify:
776 sh Configure -des -Doptimize=-g -Uusemymalloc -Dusemultiplicity \
778 setenv PURIFYOPTIONS "-chain-length=25"
781 ln -s ../pureperl perl
782 setenv PERL_DESTRUCT_LEVEL 2
785 Disabling Perl's malloc allows Purify to monitor allocations and leaks
786 more closely; using Perl's malloc will make Purify report most leaks
787 in the "potential" leaks category. Enabling the multiplicity option
788 allows perl to clean up thoroughly when the interpreter shuts down, which
789 reduces the number of bogus leak reports from Purify. The -DPURIFY
790 enables any Purify-specific debugging code in the sources.
792 Purify outputs messages in "Viewer" windows by default. If you don't have
793 a windowing environment or if you simply want the Purify output to
794 unobtrusively go to a log file instead of to the interactive window,
795 use the following options instead:
797 setenv PURIFYOPTIONS "-chain-length=25 -windows=no -log-file=perl.log \
800 The only currently known leaks happen when there are compile-time errors
801 within eval or require. (Fixing these is non-trivial, unfortunately, but
802 they must be fixed eventually.)
804 =head1 Common Gotcha's
810 The '#elif' preprocessor directive is not understood on all systems.
811 Specifically, I know that Pyramids don't understand it. Thus instead of the
822 You have to do the more Byzantine
834 Incidentally, whitespace between the leading '#' and the preprocessor
835 command is not guaranteed, but is very portable and you may use it freely.
836 I think it makes things a bit more readable, especially once things get
837 rather deeply nested. I also think that things should almost never get
838 too deeply nested, so it ought to be a moot point :-)
840 =item Probably Prefer POSIX
842 It's often the case that you'll need to choose whether to do
843 something the BSD-ish way or the POSIX-ish way. It's usually not
844 a big problem when the two systems use different names for similar
845 functions, such as memcmp() and bcmp(). The perl.h header file
846 handles these by appropriate #defines, selecting the POSIX mem*()
847 functions if available, but falling back on the b*() functions, if
850 More serious is the case where some brilliant person decided to
851 use the same function name but give it a different meaning or
852 calling sequence :-). getpgrp() and setpgrp() come to mind.
853 These are a real problem on systems that aim for conformance to
854 one standard (e.g. POSIX), but still try to support the other way
855 of doing things (e.g. BSD). My general advice (still not really
856 implemented in the source) is to do something like the following.
857 Suppose there are two alternative versions, fooPOSIX() and
861 /* use fooPOSIX(); */
864 /* try to emulate fooPOSIX() with fooBSD();
865 perhaps with the following: */
866 # define fooPOSIX fooBSD
868 # /* Uh, oh. We have to supply our own. */
869 # define fooPOSIX Perl_fooPOSIX
873 =item Think positively
875 If you need to add an #ifdef test, it is usually easier to follow if you
876 think positively, e.g.
878 #ifdef HAS_NEATO_FEATURE
879 /* use neato feature */
881 /* use some fallback mechanism */
884 rather than the more impenetrable
886 #ifndef MISSING_NEATO_FEATURE
887 /* Not missing it, so we must have it, so use it */
889 /* Are missing it, so fall back on something else. */
892 Of course for this toy example, there's not much difference. But when
893 the #ifdef's start spanning a couple of screen fulls, and the #else's
894 are marked something like
896 #else /* !MISSING_NEATO_FEATURE */
898 I find it easy to get lost.
900 =item Providing Missing Functions -- Problem
902 Not all systems have all the neat functions you might want or need, so
903 you might decide to be helpful and provide an emulation. This is
904 sound in theory and very kind of you, but please be careful about what
905 you name the function. Let me use the C<pause()> function as an
908 Perl5.003 has the following in F<perl.h>
911 #define pause() sleep((32767<<16)+32767)
914 Configure sets HAS_PAUSE if the system has the pause() function, so
915 this #define only kicks in if the pause() function is missing.
918 Unfortunately, some systems apparently have a prototype for pause()
919 in F<unistd.h>, but don't actually have the function in the library.
920 (Or maybe they do have it in a library we're not using.)
922 Thus, the compiler sees something like
924 extern int pause(void);
926 #define pause() sleep((32767<<16)+32767)
928 and dies with an error message. (Some compilers don't mind this;
929 others apparently do.)
931 To work around this, 5.003_03 and later have the following in perl.h:
933 /* Some unistd.h's give a prototype for pause() even though
934 HAS_PAUSE ends up undefined. This causes the #define
935 below to be rejected by the compiler. Sigh.
940 # define Pause() sleep((32767<<16)+32767)
945 The curious reader may wonder why I didn't do the following in
951 sleep((32767<<16)+32767);
955 That is, since the function is missing, just provide it.
956 Then things would probably be been alright, it would seem.
958 Well, almost. It could be made to work. The problem arises from the
959 conflicting needs of dynamic loading and namespace protection.
961 For dynamic loading to work on AIX (and VMS) we need to provide a list
962 of symbols to be exported. This is done by the script F<perl_exp.SH>,
963 which reads F<global.sym> and F<interp.sym>. Thus, the C<pause>
964 symbol would have to be added to F<global.sym> So far, so good.
966 On the other hand, one of the goals of Perl5 is to make it easy to
967 either extend or embed perl and link it with other libraries. This
968 means we have to be careful to keep the visible namespace "clean".
969 That is, we don't want perl's global variables to conflict with
970 those in the other application library. Although this work is still
971 in progress, the way it is currently done is via the F<embed.h> file.
972 This file is built from the F<global.sym> and F<interp.sym> files,
973 since those files already list the globally visible symbols. If we
974 had added C<pause> to global.sym, then F<embed.h> would contain the
977 #define pause Perl_pause
979 and calls to C<pause> in the perl sources would now point to
980 C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable,
981 it will go looking for C<perl_pause>, which probably won't exist in any
982 of the standard libraries. Thus the build of perl will fail.
984 Those systems where C<HAS_PAUSE> is not defined would be ok, however,
985 since they would get a C<Perl_pause> function in util.c. The rest of
986 the world would be in trouble.
988 And yes, this scenario has happened. On SCO, the function C<chsize>
989 is available. (I think it's in F<-lx>, the Xenix compatibility
990 library.) Since the perl4 days (and possibly before), Perl has
991 included a C<chsize> function that gets called something akin to
994 I32 chsize(fd, length)
1000 #define chsize Perl_chsize
1002 to F<embed.h>, the compile started failing on SCO systems.
1004 The "fix" is to give the function a different name. The one
1005 implemented in 5.003_05 isn't optimal, but here's what was done:
1008 # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */
1011 # define my_chsize chsize
1014 My explanatory comment in patch 5.003_05 said:
1016 Undef and then re-define my_chsize from Perl_my_chsize to
1017 just plain chsize if this system HAS_CHSIZE. This probably only
1018 applies to SCO. This shows the perils of having internal
1019 functions with the same name as external library functions :-).
1021 Now, we can safely put C<my_chsize> in F<global.sym>, export it, and
1022 hide it with F<embed.h>.
1024 To be consistent with what I did for C<pause>, I probably should have
1025 called the new function C<Chsize>, rather than C<my_chsize>.
1026 However, the perl sources are quite inconsistent on this (Consider
1027 New, Mymalloc, and Myremalloc, to name just a few.)
1029 There is a problem with this fix, however, in that C<Perl_chsize>
1030 was available as a F<libperl.a> library function in 5.003, but it
1031 isn't available any more (as of 5.003_07). This means that we've
1032 broken binary compatibility. This is not good.
1034 =item Providing missing functions -- some ideas
1036 We currently don't have a standard way of handling such missing
1037 function names. Right now, I'm effectively thinking aloud about a
1038 solution. Some day, I'll try to formally propose a solution.
1040 Part of the problem is that we want to have some functions listed as
1041 exported but not have their names mangled by embed.h or possibly
1042 conflict with names in standard system headers. We actually already
1043 have such a list at the end of F<perl_exp.SH> (though that list is
1046 # extra globals not included above.
1047 cat <<END >> perl.exp
1071 This still needs much thought, but I'm inclined to think that one
1072 possible solution is to prefix all such functions with C<perl_> in the
1073 source and list them along with the other C<perl_*> functions in
1076 Thus, for C<chsize>, we'd do something like the following:
1080 # define perl_chsize chsize
1083 then in some file (e.g. F<util.c> or F<doio.c>) do
1086 I32 perl_chsize(fd, length)
1087 /* implement the function here . . . */
1090 Alternatively, we could just always use C<chsize> everywhere and move
1091 C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would
1092 probably be fine as long as our C<chsize> function agreed with all the
1093 C<chsize> function prototypes in the various systems we'll be using.
1094 As long as the prototypes in actual use don't vary that much, this is
1095 probably a good alternative. (As a counter-example, note how Configure
1096 and perl have to go through hoops to find and use get Malloc_t and
1097 Free_t for C<malloc> and C<free>.)
1099 At the moment, this latter option is what I tend to prefer.
1101 =item All the world's a VAX
1103 Sorry, showing my age:-). Still, all the world is not BSD 4.[34],
1104 SVR4, or POSIX. Be aware that SVR3-derived systems are still quite
1105 common (do you have any idea how many systems run SCO?) If you don't
1106 have a bunch of v7 manuals handy, the metaconfig units (by default
1107 installed in F</usr/local/lib/dist/U>) are a good resource to look at
1112 =head1 Miscellaneous Topics
1116 Why does perl use a metaconfig-generated Configure script instead of an
1117 autoconf-generated configure script?
1119 Metaconfig and autoconf are two tools with very similar purposes.
1120 Metaconfig is actually the older of the two, and was originally written
1121 by Larry Wall, while autoconf is probably now used in a wider variety of
1122 packages. The autoconf info file discusses the history of autoconf and
1123 how it came to be. The curious reader is referred there for further
1126 Overall, both tools are quite good, I think, and the choice of which one
1127 to use could be argued either way. In March, 1994, when I was just
1128 starting to work on Configure support for Perl5, I considered both
1129 autoconf and metaconfig, and eventually decided to use metaconfig for the
1134 =item Compatibility with Perl4
1136 Perl4 used metaconfig, so many of the #ifdef's were already set up for
1137 metaconfig. Of course metaconfig had evolved some since Perl4's days,
1138 but not so much that it posed any serious problems.
1140 =item Metaconfig worked for me
1142 My system at the time was Interactive 2.2, an SVR3.2/386 derivative that
1143 also had some POSIX support. Metaconfig-generated Configure scripts
1144 worked fine for me on that system. On the other hand, autoconf-generated
1145 scripts usually didn't. (They did come quite close, though, in some
1146 cases.) At the time, I actually fetched a large number of GNU packages
1147 and checked. Not a single one configured and compiled correctly
1148 out-of-the-box with the system's cc compiler.
1150 =item Configure can be interactive
1152 With both autoconf and metaconfig, if the script works, everything is
1153 fine. However, one of my main problems with autoconf-generated scripts
1154 was that if it guessed wrong about something, it could be B<very> hard to
1155 go back and fix it. For example, autoconf always insisted on passing the
1156 -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I
1157 wanted or needed for that package. There was no way short of editing the
1158 configure script to turn this off. You couldn't just edit the resulting
1159 Makefile at the end because the -Xp flag influenced a number of other
1162 Metaconfig's Configure scripts, on the other hand, can be interactive.
1163 Thus if Configure is guessing things incorrectly, you can go back and fix
1164 them. This isn't as important now as it was when we were actively
1165 developing Configure support for new features such as dynamic loading,
1166 but it's still useful occasionally.
1170 At the time, autoconf-generated scripts were covered under the GNU Public
1171 License, and hence weren't suitable for inclusion with Perl, which has a
1172 different licensing policy. (Autoconf's licensing has since changed.)
1176 Metaconfig builds up Configure from a collection of discrete pieces
1177 called "units". You can override the standard behavior by supplying your
1178 own unit. With autoconf, you have to patch the standard files instead.
1179 I find the metaconfig "unit" method easier to work with. Others
1180 may find metaconfig's units clumsy to work with.
1184 =head2 Why isn't there a directory to override Perl's library?
1186 Mainly because no one's gotten around to making one. Note that
1187 "making one" involves changing perl.c, Configure, config_h.SH (and
1188 associated files, see above), and I<documenting> it all in the
1191 Apparently, most folks who want to override one of the standard library
1192 files simply do it by overwriting the standard library files.
1196 In the perl.c sources, you'll find an undocumented APPLLIB_EXP
1197 variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are
1198 documented in config_h.SH). Here's what APPLLIB_EXP is for, from
1199 a mail message from Larry:
1201 The main intent of APPLLIB_EXP is for folks who want to send out a
1202 version of Perl embedded in their product. They would set the symbol
1203 to be the name of the library containing the files needed to run or to
1204 support their particular application. This works at the "override"
1205 level to make sure they get their own versions of any library code that
1206 they absolutely must have configuration control over.
1208 As such, I don't see any conflict with a sysadmin using it for a
1209 override-ish sort of thing, when installing a generic Perl. It should
1210 probably have been named something to do with overriding though. Since
1211 it's undocumented we could still change it... :-)
1213 Given that it's already there, you can use it to override
1214 distribution modules. If you do
1216 sh Configure -Dccflags='-DAPPLLIB_EXP=/my/override'
1218 then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB.
1220 =head2 Shared libperl.so location
1222 Why isn't the shared libperl.so installed in /usr/lib/ along
1223 with "all the other" shared libraries? Instead, it is installed
1224 in $archlib, which is typically something like
1226 /usr/local/lib/perl5/archname/5.00404
1228 and is architecture- and version-specific.
1230 The basic reason why a shared libperl.so gets put in $archlib is so that
1231 you can have more than one version of perl on the system at the same time,
1232 and have each refer to its own libperl.so.
1234 Three examples might help. All of these work now; none would work if you
1235 put libperl.so in /usr/lib.
1241 Suppose you want to have both threaded and non-threaded perl versions
1242 around. Configure will name both perl libraries "libperl.so" (so that
1243 you can link to them with -lperl). The perl binaries tell them apart
1244 by having looking in the appropriate $archlib directories.
1248 Suppose you have perl5.004_04 installed and you want to try to compile
1249 it again, perhaps with different options or after applying a patch.
1250 If you already have libperl.so installed in /usr/lib/, then it may be
1251 either difficult or impossible to get ld.so to find the new libperl.so
1252 that you're trying to build. If, instead, libperl.so is tucked away in
1253 $archlib, then you can always just change $archlib in the current perl
1254 you're trying to build so that ld.so won't find your old libperl.so.
1255 (The INSTALL file suggests you do this when building a debugging perl.)
1259 The shared perl library is not a "well-behaved" shared library with
1260 proper major and minor version numbers, so you can't necessarily
1261 have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose
1262 perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05
1263 were to install /usr/lib/libperl.so.4.5. Now, when you try to run
1264 perl5.004_04, ld.so might try to load libperl.so.4.5, since it has
1265 the right "major version" number. If this works at all, it almost
1266 certainly defeats the reason for keeping perl5.004_04 around. Worse,
1267 with development subversions, you certaily can't guarantee that
1268 libperl.so.4.4 and libperl.so.4.55 will be compatible.
1270 Anyway, all this leads to quite obscure failures that are sure to drive
1271 casual users crazy. Even experienced users will get confused :-). Upon
1272 reflection, I'd say leave libperl.so in $archlib.
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 Good ideas waiting for round tuits
1307 =item Configure -Dsrc=/blah/blah
1309 We should be able to emulate B<configure --srcdir>. Tom Tromey
1310 tromey@creche.cygnus.com has submitted some patches to
1311 the dist-users mailing list along these lines. They have been folded
1312 back into the main distribution, but various parts of the perl
1313 Configure/build/install process still assume src='.'.
1315 =item Hint file fixes
1317 Various hint files work around Configure problems. We ought to fix
1318 Configure so that most of them aren't needed.
1320 =item Hint file information
1322 Some of the hint file information (particularly dynamic loading stuff)
1323 ought to be fed back into the main metaconfig distribution.
1327 =head2 Probably good ideas waiting for round tuits
1331 =item GNU configure --options
1333 I've received sensible suggestions for --exec_prefix and other
1334 GNU configure --options. It's not always obvious exactly what is
1335 intended, but this merits investigation.
1339 Currently, B<make clean> isn't all that useful, though
1340 B<make realclean> and B<make distclean> are. This needs a bit of
1341 thought and documentation before it gets cleaned up.
1343 =item Try gcc if cc fails
1345 Currently, we just give up.
1347 =item bypassing safe*alloc wrappers
1349 On some systems, it may be safe to call the system malloc directly
1350 without going through the util.c safe* layers. (Such systems would
1351 accept free(0), for example.) This might be a time-saver for systems
1352 that already have a good malloc. (Recent Linux libc's apparently have
1353 a nice malloc that is well-tuned for the system.)
1357 =head2 Vague possibilities
1363 Get some of the Macintosh stuff folded back into the main distribution.
1365 =item gconvert replacement
1367 Maybe include a replacement function that doesn't lose data in rare
1368 cases of coercion between string and numerical values.
1370 =item Improve makedepend
1372 The current makedepend process is clunky and annoyingly slow, but it
1373 works for most folks. Alas, it assumes that there is a filename
1374 $firstmakefile that the B<make> command will try to use before it uses
1375 F<Makefile>. Such may not be the case for all B<make> commands,
1376 particularly those on non-Unix systems.
1378 Probably some variant of the BSD F<.depend> file will be useful.
1379 We ought to check how other packages do this, if they do it at all.
1380 We could probably pre-generate the dependencies (with the exception of
1381 malloc.o, which could probably be determined at F<Makefile.SH>
1384 =item GNU Makefile standard targets
1386 GNU software generally has standardized Makefile targets. Unless we
1387 have good reason to do otherwise, I see no reason not to support them.
1391 Somehow, straighten out, document, and implement lockf(), flock(),
1392 and/or fcntl() file locking. It's a mess. See $d_fcntl_can_lock
1393 in recent config.sh files though.
1399 Original author: Andy Dougherty doughera@lafcol.lafayette.edu .
1400 Additions by Chip Salzenberg chip@perl.com and
1401 Tim Bunce Tim.Bunce@ig.co.uk .
1403 All opinions expressed herein are those of the authorZ<>(s).
1405 =head1 LAST MODIFIED
1407 $Id: pumpkin.pod,v 1.23 2000/01/13 19:45:13 doughera Released $