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
246 If your operating system comes from outside UNIX you almost certainly
247 will have differences in the available operating system functionality
248 (missing system calls, different semantics, whatever). Please
249 document these at F<pod/perlport.pod>. If your operating system is
250 the first B<not> to have a system call also update the list of
251 "portability-bewares" at the beginning of F<pod/perlfunc.pod>.
253 A file called F<README.youros> at the top level that explains things
254 like how to install perl at this platform, where to get any possibly
255 required additional software, and for example what test suite errors
256 to expect, is nice too. Such files are in the process of being written
257 in pod format and will eventually be renamed F<INSTALL.youros>.
259 You may also want to write a separate F<.pod> file for your operating
260 system to tell about existing mailing lists, os-specific modules,
261 documentation, whatever. Please name these along the lines of
262 F<perl>I<youros>.pod. [unfinished: where to put this file (the pod/
263 subdirectory, of course: but more importantly, which/what index files
268 =head2 Allow for lots of testing
270 We should never release a main version without testing it as a
273 =head2 Test popular applications and modules.
275 We should never release a main version without testing whether or not
276 it breaks various popular modules and applications. A partial list of
277 such things would include majordomo, metaconfig, apache, Tk, CGI,
278 libnet, and libwww, to name just a few. Of course it's quite possible
279 that some of those things will be just plain broken and need to be fixed,
280 but, in general, we ought to try to avoid breaking widely-installed
283 =head2 Automated generation of derivative files
285 The F<embed.h>, F<keywords.h>, F<opcode.h>, and F<perltoc.pod> files
286 are all automatically generated by perl scripts. In general, don't
287 patch these directly; patch the data files instead.
289 F<Configure> and F<config_h.SH> are also automatically generated by
290 B<metaconfig>. In general, you should patch the metaconfig units
291 instead of patching these files directly. However, very minor changes
292 to F<Configure> may be made in between major sync-ups with the
293 metaconfig units, which tends to be complicated operations. But be
294 careful, this can quickly spiral out of control. Running metaconfig
297 Also F<Makefile> is automatically produced from F<Makefile.SH>.
298 In general, look out for all F<*.SH> files.
300 Finally, the sample files in the F<Porting/> subdirectory are
301 generated automatically by the script F<U/mksample> included
302 with the metaconfig units. See L<"run metaconfig"> below for
303 information on obtaining the metaconfig units.
305 =head1 How to Make a Distribution
307 There really ought to be a 'make dist' target, but there isn't.
308 The 'dist' suite of tools also contains a number of tools that I haven't
309 learned how to use yet. Some of them may make this all a bit easier.
311 Here are the steps I go through to prepare a patch & distribution.
313 Lots of it could doubtless be automated but isn't. The Porting/makerel
314 (make release) perl script does now help automate some parts of it.
316 =head2 Announce your intentions
318 First, you should volunteer out loud to take the patch pumpkin. It's
319 generally counter-productive to have multiple people working in secret
322 At the same time, announce what you plan to do with the patch pumpkin,
323 to allow folks a chance to object or suggest alternatives, or do it for
324 you. Naturally, the patch pumpkin holder ought to incorporate various
325 bug fixes and documentation improvements that are posted while he or
326 she has the pumpkin, but there might also be larger issues at stake.
328 One of the precepts of the subversion idea is that we shouldn't give
329 the patch pumpkin to anyone unless we have some idea what he or she
330 is going to do with it.
332 =head2 refresh pod/perltoc.pod
334 Presumably, you have done a full C<make> in your working source
335 directory. Before you C<make spotless> (if you do), and if you have
336 changed any documentation in any module or pod file, change to the
337 F<pod> directory and run C<make toc>.
339 =head2 run installhtml to check the validity of the pod files
341 =head2 update patchlevel.h
343 Don't be shy about using the subversion number, even for a relatively
344 modest patch. We've never even come close to using all 99 subversions,
345 and it's better to have a distinctive number for your patch. If you
346 need feedback on your patch, go ahead and issue it and promise to
347 incorporate that feedback quickly (e.g. within 1 week) and send out a
350 =head2 run metaconfig
352 If you need to make changes to Configure or config_h.SH, it may be best to
353 change the appropriate metaconfig units instead, and regenerate Configure.
357 will regenerate Configure and config_h.SH. Much more information
358 on obtaining and running metaconfig is in the F<U/README> file
359 that comes with Perl's metaconfig units. Perl's metaconfig units
360 should be available on CPAN. A set of units that will work with
361 perl5.005 is in the file F<mc_units-5.005_00-01.tar.gz> under
362 http://www.cpan.org/authors/id/ANDYD/ . The mc_units tar file
363 should be unpacked in your main perl source directory. Note: those
364 units were for use with 5.005. There may have been changes since then.
365 Check for later versions or contact perl5-porters@perl.org to obtain a
366 pointer to the current version.
368 Alternatively, do consider if the F<*ish.h> files might be a better
369 place for your changes.
373 Make sure the MANIFEST is up-to-date. You can use dist's B<manicheck>
374 program for this. You can also use
376 perl -w -MExtUtils::Manifest=fullcheck -e fullcheck
378 Both commands will also list extra files in the directory that are not
381 The MANIFEST is normally sorted.
383 If you are using metaconfig to regenerate Configure, then you should note
384 that metaconfig actually uses MANIFEST.new, so you want to be sure
385 MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new
386 distinction particularly useful, but that's probably because I still haven't
387 learned how to use the full suite of tools in the dist distribution.
389 =head2 Check permissions
391 All the tests in the t/ directory ought to be executable. The
392 main makefile used to do a 'chmod t/*/*.t', but that resulted in
393 a self-modifying distribution--something some users would strongly
394 prefer to avoid. The F<t/TEST> script will check for this
395 and do the chmod if needed, but the tests still ought to be
398 In all, the following files should probably be executable:
413 vms/ext/Stdio/test.pl
417 Other things ought to be readable, at least :-).
419 Probably, the permissions for the files could be encoded in MANIFEST
420 somehow, but I'm reluctant to change MANIFEST itself because that
421 could break old scripts that use MANIFEST.
423 I seem to recall that some SVR3 systems kept some sort of file that listed
424 permissions for system files; something like that might be appropriate.
428 This will build a config.sh and config.h. You can skip this if you haven't
429 changed Configure or config_h.SH at all. I use the following command
431 sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \
433 -Dcf_email='yourname@yourhost.yourplace.com' \
434 -Dperladmin='yourname@yourhost.yourplace.com' \
435 -Dmydomain='.yourplace.com' \
436 -Dmyhostname='yourhost' \
439 =head2 Update Porting/config.sh and Porting/config_H
442 This section needs revision. We're currently working on easing
443 the task of keeping the vms, win32, and plan9 config.sh info
444 up-to-date. The plan is to use keep up-to-date 'canned' config.sh
445 files in the appropriate subdirectories and then generate 'canned'
446 config.h files for vms, win32, etc. from the generic config.sh file.
447 This is to ease maintenance. When Configure gets updated, the parts
448 sometimes get scrambled around, and the changes in config_H can
449 sometimes be very hard to follow. config.sh, on the other hand, can
450 safely be sorted, so it's easy to track (typically very small) changes
451 to config.sh and then propoagate them to a canned 'config.h' by any
452 number of means, including a perl script in win32/ or carrying
453 config.sh and config_h.SH to a Unix system and running sh
454 config_h.SH.) Vms uses configure.com to generate its own config.sh
455 and config.h. If you want to add a new variable to config.sh check
456 with vms folk how to add it to configure.com too.
459 The Porting/config.sh and Porting/config_H files are provided to
460 help those folks who can't run Configure. It is important to keep
461 them up-to-date. If you have changed config_h.SH, those changes must
462 be reflected in config_H as well. (The name config_H was chosen to
463 distinguish the file from config.h even on case-insensitive file systems.)
464 Simply edit the existing config_H file; keep the first few explanatory
465 lines and then copy your new config.h below.
467 It may also be necessary to update win32/config.?c, and
468 plan9/config.plan9, though you should be quite careful in doing so if
469 you are not familiar with those systems. You might want to issue your
470 patch with a promise to quickly issue a follow-up that handles those
473 =head2 make run_byacc
475 If you have byacc-1.8.2 (available from CPAN), and if there have been
476 changes to F<perly.y>, you can regenerate the F<perly.c> file. The
477 run_byacc makefile target does this by running byacc and then applying
478 some patches so that byacc dynamically allocates space, rather than
479 having fixed limits. This patch is handled by the F<perly.fixer>
480 script. Depending on the nature of the changes to F<perly.y>, you may
481 or may not have to hand-edit the patch to apply correctly. If you do,
482 you should include the edited patch in the new distribution. If you
483 have byacc-1.9, the patch won't apply cleanly. Changes to the printf
484 output statements mean the patch won't apply cleanly. Long ago I
485 started to fix F<perly.fixer> to detect this, but I never completed the
488 If C<perly.c> or C<perly.h> changes, make sure you run C<perl vms/vms_yfix.pl>
489 to update the corresponding VMS files. This could be taken care of by
490 the regen_all target in the Unix Makefile. See also
491 L<VMS-specific updates>.
493 Some additional notes from Larry on this:
495 Don't forget to regenerate perly_c.diff.
499 patch perly.c <perly_c.diff
500 # manually apply any failed hunks
501 diff -c2 perly.c.orig perly.c >perly_c.diff
503 One chunk of lines that often fails begins with
507 and ends one line before
509 #define YYERRCODE 256
511 This only happens when you add or remove a token type. I suppose this
512 could be automated, but it doesn't happen very often nowadays.
516 =head2 make regen_all
518 This target takes care of the PERLYVMS, regen_headers, and regen_pods
521 =head2 make regen_headers
523 The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically
524 generated by perl scripts. Since the user isn't guaranteed to have a
525 working perl, we can't require the user to generate them. Hence you have
526 to, if you're making a distribution.
528 I used to include rules like the following in the makefile:
530 # The following three header files are generated automatically
531 # The correct versions should be already supplied with the perl kit,
532 # in case you don't have perl or 'sh' available.
533 # The - is to ignore error return codes in case you have the source
534 # installed read-only or you don't have perl yet.
535 keywords.h: keywords.pl
536 @echo "Don't worry if this fails."
540 However, I got B<lots> of mail consisting of people worrying because the
541 command failed. I eventually decided that I would save myself time
542 and effort by manually running C<make regen_headers> myself rather
543 than answering all the questions and complaints about the failing
546 =head2 make regen_pods
548 Will run `make regen_pods` in the pod directory for indexing.
550 =head2 global.sym, interp.sym and perlio.sym
552 Make sure these files are up-to-date. Read the comments in these
553 files and in perl_exp.SH to see what to do.
555 =head2 Binary compatibility
557 If you do change F<global.sym> or F<interp.sym>, think carefully about
558 what you are doing. To the extent reasonable, we'd like to maintain
559 source and binary compatibility with older releases of perl. That way,
560 extensions built under one version of perl will continue to work with
561 new versions of perl.
563 Of course, some incompatible changes may well be necessary. I'm just
564 suggesting that we not make any such changes without thinking carefully
565 about them first. If possible, we should provide
566 backwards-compatibility stubs. There's a lot of XS code out there.
567 Let's not force people to keep changing it.
571 Be sure to update the F<Changes> file. Try to include both an overall
572 summary as well as detailed descriptions of the changes. Your
573 audience will include other developers and users, so describe
574 user-visible changes (if any) in terms they will understand, not in
575 code like "initialize foo variable in bar function".
577 There are differing opinions on whether the detailed descriptions
578 ought to go in the Changes file or whether they ought to be available
579 separately in the patch file (or both). There is no disagreement that
580 detailed descriptions ought to be easily available somewhere.
584 The F<Todo> file contains a roughly-catgorized unordered list of
585 aspects of Perl that could use enhancement, features that could be
586 added, areas that could be cleaned up, and so on. During your term as
587 pumpkin-holder, you will probably address some of these issues, and
588 perhaps identify others which, while you decide not to address them
589 this time around, may be tackled in the future. Update the file
590 reflect the situation as it stands when you hand over the pumpkin.
592 You might like, early in your pumpkin-holding career, to see if you
593 can find champions for partiticular issues on the to-do list: an issue
594 owned is an issue more likely to be resolved.
596 There are also some more porting-specific L<Todo> items later in this
599 =head2 OS/2-specific updates
601 In the os2 directory is F<diff.configure>, a set of OS/2-specific
602 diffs against B<Configure>. If you make changes to Configure, you may
603 want to consider regenerating this diff file to save trouble for the
606 You can also consider the OS/2 diffs as reminders of portability
607 things that need to be fixed in Configure.
609 =head2 VMS-specific updates
611 If you have changed F<perly.y> or F<perly.c>, then you most probably want
612 to update F<vms/perly_{h,c}.vms> by running C<perl vms/vms_yfix.pl>, or
613 by running `make regen_all` which will run that script for you.
615 The Perl revision number appears as "perl5" in configure.com.
616 It is courteous to update that if necessary.
618 =head2 Making the new distribution
620 Suppose, for example, that you want to make version 5.004_08. Then you can
621 do something like the following
623 mkdir ../perl5.004_08
624 awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08
626 tar cf perl5.004_08.tar perl5.004_08
627 gzip --best perl5.004_08.tar
629 These steps, with extra checks, are automated by the Porting/makerel
632 =head2 Making a new patch
634 I find the F<makepatch> utility quite handy for making patches.
635 You can obtain it from any CPAN archive under
636 http://www.cpan.org/authors/Johan_Vromans/ . There are a couple
637 of differences between my version and the standard one. I have mine do
640 # Print a reassuring "End of Patch" note so people won't
641 # wonder if their mailer truncated patches.
642 print "\n\nEnd of Patch.\n";
644 at the end. That's because I used to get questions from people asking
645 if their mail was truncated.
647 It also writes Index: lines which include the new directory prefix
648 (change Index: print, approx line 294 or 310 depending on the version,
649 to read: print PATCH ("Index: $newdir$new\n");). That helps patches
650 work with more POSIX conformant patch programs.
652 Here's how I generate a new patch. I'll use the hypothetical
653 5.004_07 to 5.004_08 patch as an example.
655 # unpack perl5.004_07/
656 gzip -d -c perl5.004_07.tar.gz | tar -xof -
657 # unpack perl5.004_08/
658 gzip -d -c perl5.004_08.tar.gz | tar -xof -
659 makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat
661 Makepatch will automatically generate appropriate B<rm> commands to remove
662 deleted files. Unfortunately, it will not correctly set permissions
663 for newly created files, so you may have to do so manually. For example,
664 patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable,
665 so at the top of the patch, I inserted the following lines:
671 Now, of course, my patch is now wrong because makepatch didn't know I
672 was going to do that command, and it patched against /dev/null.
674 So, what I do is sort out all such shell commands that need to be in the
675 patch (including possible mv-ing of files, if needed) and put that in the
676 shell commands at the top of the patch. Next, I delete all the patch parts
677 of perl5.004_08.pat, leaving just the shell commands. Then, I do the
681 sh ../perl5.004_08.pat
683 makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat
685 (Note the append to preserve my shell commands.)
686 Now, my patch will line up with what the end users are going to do.
688 =head2 Testing your patch
690 It seems obvious, but be sure to test your patch. That is, verify that
691 it produces exactly the same thing as your full distribution.
694 gzip -d -c perl5.004_07.tar.gz | tar -xf -
696 sh ../perl5.004_08.pat
697 patch -p1 -N < ../perl5.004_08.pat
699 gdiff -r perl5.004_07 perl5.004_08
701 where B<gdiff> is GNU diff. Other diff's may also do recursive checking.
705 Again, it's obvious, but you should test your new version as widely as you
706 can. You can be sure you'll hear about it quickly if your version doesn't
707 work on both ANSI and pre-ANSI compilers, and on common systems such as
708 SunOS 4.1.[34], Solaris, and Linux.
710 If your changes include conditional code, try to test the different
711 branches as thoroughly as you can. For example, if your system
712 supports dynamic loading, you can also test static loading with
716 You can also hand-tweak your config.h to try out different #ifdef
725 To test the correct use of printf-style arguments, C<Configure> with
726 S<-Dccflags='-DCHECK_FORMAT -Wformat'> and run C<make>. The compiler
727 will produce warning of incorrect use of format arguments. CHECK_FORMAT
728 changes perl-defined formats to common formats, so DO NOT USE the executable
729 produced by this process.
731 A more accurate approach is the following commands:
737 build miniperl with -DCHECK_FORMAT
740 make miniperl OPTIMIZE=-DCHECK_FORMAT >& mini.log
744 build a clean miniperl,
745 and build everything else from that with -DCHECK_FORMAT
749 make all OPTIMIZE=-DCHECK_FORMAT >& make.log
753 clean up, and print warnings from the log files
756 perl -nwe 'print if /^\S+:/ and not /^make\b/' \
761 (-Wformat support by Robin Barker.)
765 =head1 Running Purify
767 Purify is a commercial tool that is helpful in identifying memory
768 overruns, wild pointers, memory leaks and other such badness. Perl
769 must be compiled in a specific way for optimal testing with Purify.
771 Use the following commands to test perl with Purify:
773 sh Configure -des -Doptimize=-g -Uusemymalloc -Dusemultiplicity \
775 setenv PURIFYOPTIONS "-chain-length=25"
778 ln -s ../pureperl perl
779 setenv PERL_DESTRUCT_LEVEL 2
782 Disabling Perl's malloc allows Purify to monitor allocations and leaks
783 more closely; using Perl's malloc will make Purify report most leaks
784 in the "potential" leaks category. Enabling the multiplicity option
785 allows perl to clean up thoroughly when the interpreter shuts down, which
786 reduces the number of bogus leak reports from Purify. The -DPURIFY
787 enables any Purify-specific debugging code in the sources.
789 Purify outputs messages in "Viewer" windows by default. If you don't have
790 a windowing environment or if you simply want the Purify output to
791 unobtrusively go to a log file instead of to the interactive window,
792 use the following options instead:
794 setenv PURIFYOPTIONS "-chain-length=25 -windows=no -log-file=perl.log \
797 The only currently known leaks happen when there are compile-time errors
798 within eval or require. (Fixing these is non-trivial, unfortunately, but
799 they must be fixed eventually.)
801 =head1 Common Gotcha's
807 The '#elif' preprocessor directive is not understood on all systems.
808 Specifically, I know that Pyramids don't understand it. Thus instead of the
819 You have to do the more Byzantine
831 Incidentally, whitespace between the leading '#' and the preprocessor
832 command is not guaranteed, but is very portable and you may use it freely.
833 I think it makes things a bit more readable, especially once things get
834 rather deeply nested. I also think that things should almost never get
835 too deeply nested, so it ought to be a moot point :-)
837 =item Probably Prefer POSIX
839 It's often the case that you'll need to choose whether to do
840 something the BSD-ish way or the POSIX-ish way. It's usually not
841 a big problem when the two systems use different names for similar
842 functions, such as memcmp() and bcmp(). The perl.h header file
843 handles these by appropriate #defines, selecting the POSIX mem*()
844 functions if available, but falling back on the b*() functions, if
847 More serious is the case where some brilliant person decided to
848 use the same function name but give it a different meaning or
849 calling sequence :-). getpgrp() and setpgrp() come to mind.
850 These are a real problem on systems that aim for conformance to
851 one standard (e.g. POSIX), but still try to support the other way
852 of doing things (e.g. BSD). My general advice (still not really
853 implemented in the source) is to do something like the following.
854 Suppose there are two alternative versions, fooPOSIX() and
858 /* use fooPOSIX(); */
861 /* try to emulate fooPOSIX() with fooBSD();
862 perhaps with the following: */
863 # define fooPOSIX fooBSD
865 # /* Uh, oh. We have to supply our own. */
866 # define fooPOSIX Perl_fooPOSIX
870 =item Think positively
872 If you need to add an #ifdef test, it is usually easier to follow if you
873 think positively, e.g.
875 #ifdef HAS_NEATO_FEATURE
876 /* use neato feature */
878 /* use some fallback mechanism */
881 rather than the more impenetrable
883 #ifndef MISSING_NEATO_FEATURE
884 /* Not missing it, so we must have it, so use it */
886 /* Are missing it, so fall back on something else. */
889 Of course for this toy example, there's not much difference. But when
890 the #ifdef's start spanning a couple of screen fulls, and the #else's
891 are marked something like
893 #else /* !MISSING_NEATO_FEATURE */
895 I find it easy to get lost.
897 =item Providing Missing Functions -- Problem
899 Not all systems have all the neat functions you might want or need, so
900 you might decide to be helpful and provide an emulation. This is
901 sound in theory and very kind of you, but please be careful about what
902 you name the function. Let me use the C<pause()> function as an
905 Perl5.003 has the following in F<perl.h>
908 #define pause() sleep((32767<<16)+32767)
911 Configure sets HAS_PAUSE if the system has the pause() function, so
912 this #define only kicks in if the pause() function is missing.
915 Unfortunately, some systems apparently have a prototype for pause()
916 in F<unistd.h>, but don't actually have the function in the library.
917 (Or maybe they do have it in a library we're not using.)
919 Thus, the compiler sees something like
921 extern int pause(void);
923 #define pause() sleep((32767<<16)+32767)
925 and dies with an error message. (Some compilers don't mind this;
926 others apparently do.)
928 To work around this, 5.003_03 and later have the following in perl.h:
930 /* Some unistd.h's give a prototype for pause() even though
931 HAS_PAUSE ends up undefined. This causes the #define
932 below to be rejected by the compiler. Sigh.
937 # define Pause() sleep((32767<<16)+32767)
942 The curious reader may wonder why I didn't do the following in
948 sleep((32767<<16)+32767);
952 That is, since the function is missing, just provide it.
953 Then things would probably be been alright, it would seem.
955 Well, almost. It could be made to work. The problem arises from the
956 conflicting needs of dynamic loading and namespace protection.
958 For dynamic loading to work on AIX (and VMS) we need to provide a list
959 of symbols to be exported. This is done by the script F<perl_exp.SH>,
960 which reads F<global.sym> and F<interp.sym>. Thus, the C<pause>
961 symbol would have to be added to F<global.sym> So far, so good.
963 On the other hand, one of the goals of Perl5 is to make it easy to
964 either extend or embed perl and link it with other libraries. This
965 means we have to be careful to keep the visible namespace "clean".
966 That is, we don't want perl's global variables to conflict with
967 those in the other application library. Although this work is still
968 in progress, the way it is currently done is via the F<embed.h> file.
969 This file is built from the F<global.sym> and F<interp.sym> files,
970 since those files already list the globally visible symbols. If we
971 had added C<pause> to global.sym, then F<embed.h> would contain the
974 #define pause Perl_pause
976 and calls to C<pause> in the perl sources would now point to
977 C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable,
978 it will go looking for C<perl_pause>, which probably won't exist in any
979 of the standard libraries. Thus the build of perl will fail.
981 Those systems where C<HAS_PAUSE> is not defined would be ok, however,
982 since they would get a C<Perl_pause> function in util.c. The rest of
983 the world would be in trouble.
985 And yes, this scenario has happened. On SCO, the function C<chsize>
986 is available. (I think it's in F<-lx>, the Xenix compatibility
987 library.) Since the perl4 days (and possibly before), Perl has
988 included a C<chsize> function that gets called something akin to
991 I32 chsize(fd, length)
997 #define chsize Perl_chsize
999 to F<embed.h>, the compile started failing on SCO systems.
1001 The "fix" is to give the function a different name. The one
1002 implemented in 5.003_05 isn't optimal, but here's what was done:
1005 # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */
1008 # define my_chsize chsize
1011 My explanatory comment in patch 5.003_05 said:
1013 Undef and then re-define my_chsize from Perl_my_chsize to
1014 just plain chsize if this system HAS_CHSIZE. This probably only
1015 applies to SCO. This shows the perils of having internal
1016 functions with the same name as external library functions :-).
1018 Now, we can safely put C<my_chsize> in F<global.sym>, export it, and
1019 hide it with F<embed.h>.
1021 To be consistent with what I did for C<pause>, I probably should have
1022 called the new function C<Chsize>, rather than C<my_chsize>.
1023 However, the perl sources are quite inconsistent on this (Consider
1024 New, Mymalloc, and Myremalloc, to name just a few.)
1026 There is a problem with this fix, however, in that C<Perl_chsize>
1027 was available as a F<libperl.a> library function in 5.003, but it
1028 isn't available any more (as of 5.003_07). This means that we've
1029 broken binary compatibility. This is not good.
1031 =item Providing missing functions -- some ideas
1033 We currently don't have a standard way of handling such missing
1034 function names. Right now, I'm effectively thinking aloud about a
1035 solution. Some day, I'll try to formally propose a solution.
1037 Part of the problem is that we want to have some functions listed as
1038 exported but not have their names mangled by embed.h or possibly
1039 conflict with names in standard system headers. We actually already
1040 have such a list at the end of F<perl_exp.SH> (though that list is
1043 # extra globals not included above.
1044 cat <<END >> perl.exp
1068 This still needs much thought, but I'm inclined to think that one
1069 possible solution is to prefix all such functions with C<perl_> in the
1070 source and list them along with the other C<perl_*> functions in
1073 Thus, for C<chsize>, we'd do something like the following:
1077 # define perl_chsize chsize
1080 then in some file (e.g. F<util.c> or F<doio.c>) do
1083 I32 perl_chsize(fd, length)
1084 /* implement the function here . . . */
1087 Alternatively, we could just always use C<chsize> everywhere and move
1088 C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would
1089 probably be fine as long as our C<chsize> function agreed with all the
1090 C<chsize> function prototypes in the various systems we'll be using.
1091 As long as the prototypes in actual use don't vary that much, this is
1092 probably a good alternative. (As a counter-example, note how Configure
1093 and perl have to go through hoops to find and use get Malloc_t and
1094 Free_t for C<malloc> and C<free>.)
1096 At the moment, this latter option is what I tend to prefer.
1098 =item All the world's a VAX
1100 Sorry, showing my age:-). Still, all the world is not BSD 4.[34],
1101 SVR4, or POSIX. Be aware that SVR3-derived systems are still quite
1102 common (do you have any idea how many systems run SCO?) If you don't
1103 have a bunch of v7 manuals handy, the metaconfig units (by default
1104 installed in F</usr/local/lib/dist/U>) are a good resource to look at
1109 =head1 Miscellaneous Topics
1113 Why does perl use a metaconfig-generated Configure script instead of an
1114 autoconf-generated configure script?
1116 Metaconfig and autoconf are two tools with very similar purposes.
1117 Metaconfig is actually the older of the two, and was originally written
1118 by Larry Wall, while autoconf is probably now used in a wider variety of
1119 packages. The autoconf info file discusses the history of autoconf and
1120 how it came to be. The curious reader is referred there for further
1123 Overall, both tools are quite good, I think, and the choice of which one
1124 to use could be argued either way. In March, 1994, when I was just
1125 starting to work on Configure support for Perl5, I considered both
1126 autoconf and metaconfig, and eventually decided to use metaconfig for the
1131 =item Compatibility with Perl4
1133 Perl4 used metaconfig, so many of the #ifdef's were already set up for
1134 metaconfig. Of course metaconfig had evolved some since Perl4's days,
1135 but not so much that it posed any serious problems.
1137 =item Metaconfig worked for me
1139 My system at the time was Interactive 2.2, an SVR3.2/386 derivative that
1140 also had some POSIX support. Metaconfig-generated Configure scripts
1141 worked fine for me on that system. On the other hand, autoconf-generated
1142 scripts usually didn't. (They did come quite close, though, in some
1143 cases.) At the time, I actually fetched a large number of GNU packages
1144 and checked. Not a single one configured and compiled correctly
1145 out-of-the-box with the system's cc compiler.
1147 =item Configure can be interactive
1149 With both autoconf and metaconfig, if the script works, everything is
1150 fine. However, one of my main problems with autoconf-generated scripts
1151 was that if it guessed wrong about something, it could be B<very> hard to
1152 go back and fix it. For example, autoconf always insisted on passing the
1153 -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I
1154 wanted or needed for that package. There was no way short of editing the
1155 configure script to turn this off. You couldn't just edit the resulting
1156 Makefile at the end because the -Xp flag influenced a number of other
1159 Metaconfig's Configure scripts, on the other hand, can be interactive.
1160 Thus if Configure is guessing things incorrectly, you can go back and fix
1161 them. This isn't as important now as it was when we were actively
1162 developing Configure support for new features such as dynamic loading,
1163 but it's still useful occasionally.
1167 At the time, autoconf-generated scripts were covered under the GNU Public
1168 License, and hence weren't suitable for inclusion with Perl, which has a
1169 different licensing policy. (Autoconf's licensing has since changed.)
1173 Metaconfig builds up Configure from a collection of discrete pieces
1174 called "units". You can override the standard behavior by supplying your
1175 own unit. With autoconf, you have to patch the standard files instead.
1176 I find the metaconfig "unit" method easier to work with. Others
1177 may find metaconfig's units clumsy to work with.
1181 =head2 Why isn't there a directory to override Perl's library?
1183 Mainly because no one's gotten around to making one. Note that
1184 "making one" involves changing perl.c, Configure, config_h.SH (and
1185 associated files, see above), and I<documenting> it all in the
1188 Apparently, most folks who want to override one of the standard library
1189 files simply do it by overwriting the standard library files.
1193 In the perl.c sources, you'll find an undocumented APPLLIB_EXP
1194 variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are
1195 documented in config_h.SH). Here's what APPLLIB_EXP is for, from
1196 a mail message from Larry:
1198 The main intent of APPLLIB_EXP is for folks who want to send out a
1199 version of Perl embedded in their product. They would set the symbol
1200 to be the name of the library containing the files needed to run or to
1201 support their particular application. This works at the "override"
1202 level to make sure they get their own versions of any library code that
1203 they absolutely must have configuration control over.
1205 As such, I don't see any conflict with a sysadmin using it for a
1206 override-ish sort of thing, when installing a generic Perl. It should
1207 probably have been named something to do with overriding though. Since
1208 it's undocumented we could still change it... :-)
1210 Given that it's already there, you can use it to override
1211 distribution modules. If you do
1213 sh Configure -Dccflags='-DAPPLLIB_EXP=/my/override'
1215 then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB.
1217 =head2 Shared libperl.so location
1219 Why isn't the shared libperl.so installed in /usr/lib/ along
1220 with "all the other" shared libraries? Instead, it is installed
1221 in $archlib, which is typically something like
1223 /usr/local/lib/perl5/archname/5.00404
1225 and is architecture- and version-specific.
1227 The basic reason why a shared libperl.so gets put in $archlib is so that
1228 you can have more than one version of perl on the system at the same time,
1229 and have each refer to its own libperl.so.
1231 Three examples might help. All of these work now; none would work if you
1232 put libperl.so in /usr/lib.
1238 Suppose you want to have both threaded and non-threaded perl versions
1239 around. Configure will name both perl libraries "libperl.so" (so that
1240 you can link to them with -lperl). The perl binaries tell them apart
1241 by having looking in the appropriate $archlib directories.
1245 Suppose you have perl5.004_04 installed and you want to try to compile
1246 it again, perhaps with different options or after applying a patch.
1247 If you already have libperl.so installed in /usr/lib/, then it may be
1248 either difficult or impossible to get ld.so to find the new libperl.so
1249 that you're trying to build. If, instead, libperl.so is tucked away in
1250 $archlib, then you can always just change $archlib in the current perl
1251 you're trying to build so that ld.so won't find your old libperl.so.
1252 (The INSTALL file suggests you do this when building a debugging perl.)
1256 The shared perl library is not a "well-behaved" shared library with
1257 proper major and minor version numbers, so you can't necessarily
1258 have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose
1259 perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05
1260 were to install /usr/lib/libperl.so.4.5. Now, when you try to run
1261 perl5.004_04, ld.so might try to load libperl.so.4.5, since it has
1262 the right "major version" number. If this works at all, it almost
1263 certainly defeats the reason for keeping perl5.004_04 around. Worse,
1264 with development subversions, you certaily can't guarantee that
1265 libperl.so.4.4 and libperl.so.4.55 will be compatible.
1267 Anyway, all this leads to quite obscure failures that are sure to drive
1268 casual users crazy. Even experienced users will get confused :-). Upon
1269 reflection, I'd say leave libperl.so in $archlib.
1273 =head1 Upload Your Work to CPAN
1275 You can upload your work to CPAN if you have a CPAN id. Check out
1276 http://www.cpan.org/modules/04pause.html for information on
1277 _PAUSE_, the Perl Author's Upload Server.
1279 I typically upload both the patch file, e.g. F<perl5.004_08.pat.gz>
1280 and the full tar file, e.g. F<perl5.004_08.tar.gz>.
1282 If you want your patch to appear in the F<src/5.0/unsupported>
1283 directory on CPAN, send e-mail to the CPAN master librarian. (Check
1284 out http://www.cpan.org/CPAN.html ).
1286 =head1 Help Save the World
1288 You should definitely announce your patch on the perl5-porters list.
1289 You should also consider announcing your patch on
1290 comp.lang.perl.announce, though you should make it quite clear that a
1291 subversion is not a production release, and be prepared to deal with
1292 people who will not read your disclaimer.
1296 Here, in no particular order, are some Configure and build-related
1297 items that merit consideration. This list isn't exhaustive, it's just
1298 what I came up with off the top of my head.
1300 =head2 Good ideas waiting for round tuits
1304 =item Configure -Dsrc=/blah/blah
1306 We should be able to emulate B<configure --srcdir>. Tom Tromey
1307 tromey@creche.cygnus.com has submitted some patches to
1308 the dist-users mailing list along these lines. They have been folded
1309 back into the main distribution, but various parts of the perl
1310 Configure/build/install process still assume src='.'.
1312 =item Hint file fixes
1314 Various hint files work around Configure problems. We ought to fix
1315 Configure so that most of them aren't needed.
1317 =item Hint file information
1319 Some of the hint file information (particularly dynamic loading stuff)
1320 ought to be fed back into the main metaconfig distribution.
1324 =head2 Probably good ideas waiting for round tuits
1328 =item GNU configure --options
1330 I've received sensible suggestions for --exec_prefix and other
1331 GNU configure --options. It's not always obvious exactly what is
1332 intended, but this merits investigation.
1336 Currently, B<make clean> isn't all that useful, though
1337 B<make realclean> and B<make distclean> are. This needs a bit of
1338 thought and documentation before it gets cleaned up.
1340 =item Try gcc if cc fails
1342 Currently, we just give up.
1344 =item bypassing safe*alloc wrappers
1346 On some systems, it may be safe to call the system malloc directly
1347 without going through the util.c safe* layers. (Such systems would
1348 accept free(0), for example.) This might be a time-saver for systems
1349 that already have a good malloc. (Recent Linux libc's apparently have
1350 a nice malloc that is well-tuned for the system.)
1354 =head2 Vague possibilities
1360 Get some of the Macintosh stuff folded back into the main distribution.
1362 =item gconvert replacement
1364 Maybe include a replacement function that doesn't lose data in rare
1365 cases of coercion between string and numerical values.
1367 =item Improve makedepend
1369 The current makedepend process is clunky and annoyingly slow, but it
1370 works for most folks. Alas, it assumes that there is a filename
1371 $firstmakefile that the B<make> command will try to use before it uses
1372 F<Makefile>. Such may not be the case for all B<make> commands,
1373 particularly those on non-Unix systems.
1375 Probably some variant of the BSD F<.depend> file will be useful.
1376 We ought to check how other packages do this, if they do it at all.
1377 We could probably pre-generate the dependencies (with the exception of
1378 malloc.o, which could probably be determined at F<Makefile.SH>
1381 =item GNU Makefile standard targets
1383 GNU software generally has standardized Makefile targets. Unless we
1384 have good reason to do otherwise, I see no reason not to support them.
1388 Somehow, straighten out, document, and implement lockf(), flock(),
1389 and/or fcntl() file locking. It's a mess. See $d_fcntl_can_lock
1390 in recent config.sh files though.
1396 Original author: Andy Dougherty doughera@lafcol.lafayette.edu .
1397 Additions by Chip Salzenberg chip@perl.com and
1398 Tim Bunce Tim.Bunce@ig.co.uk .
1400 All opinions expressed herein are those of the authorZ<>(s).
1402 =head1 LAST MODIFIED
1404 $Id: pumpkin.pod,v 1.23 2000/01/13 19:45:13 doughera Released $