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1=head1 NAME
2
e25f343d 3Pumpkin - Notes on handling the Perl Patch Pumpkin And Porting Perl
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4
5=head1 SYNOPSIS
6
7There is no simple synopsis, yet.
8
9=head1 DESCRIPTION
10
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11This document attempts to begin to describe some of the considerations
12involved in patching, porting, and maintaining perl.
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13
14This document is still under construction, and still subject to
15significant changes. Still, I hope parts of it will be useful,
16so I'm releasing it even though it's not done.
17
18For the most part, it's a collection of anecdotal information that
19already assumes some familiarity with the Perl sources. I really need
20an introductory section that describes the organization of the sources
21and all the various auxiliary files that are part of the distribution.
22
23=head1 Where Do I Get Perl Sources and Related Material?
24
25The Comprehensive Perl Archive Network (or CPAN) is the place to go.
26There are many mirrors, but the easiest thing to use is probably
a93751fa 27http://www.cpan.org/README.html , which automatically points you to a
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28mirror site "close" to you.
29
30=head2 Perl5-porters mailing list
31
32The mailing list perl5-porters@perl.org
33is the main group working with the development of perl. If you're
34interested in all the latest developments, you should definitely
35subscribe. The list is high volume, but generally has a
36fairly low noise level.
37
38Subscribe by sending the message (in the body of your letter)
39
40 subscribe perl5-porters
41
42to perl5-porters-request@perl.org .
43
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44Archives of the list are held at:
45
f38c94f4 46 http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/
fb73857a 47
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48=head1 How are Perl Releases Numbered?
49
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50Beginning with v5.6.0, even versions will stand for maintenance releases
51and odd versions for development releases, i.e., v5.6.x for maintenance
52releases, and v5.7.x for development releases. Before v5.6.0, subversions
53_01 through _49 were reserved for bug-fix maintenance releases, and
54subversions _50 through _99 for unstable development versions.
7b5757d1 55
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56For example, in v5.6.1, the revision number is 5, the version is 6,
57and 1 is the subversion.
aa689395 58
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59For compatibility with the older numbering scheme the composite floating
60point version number continues to be available as the magic variable $],
76ba0908 61and amounts to C<$revision + $version/1000 + $subversion/100000>. This
f5a32c7f 62can still be used in comparisons.
aa689395 63
f5a32c7f 64 print "You've got an old perl\n" if $] < 5.005_03;
aa689395 65
f5a32c7f 66In addition, the version is also available as a string in $^V.
aa689395 67
f5a32c7f 68 print "You've got a new perl\n" if $^V and $^V ge v5.6.0;
7b5757d1 69
f5a32c7f 70You can also require particular version (or later) with:
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f5a32c7f 72 use 5.006;
aa689395 73
f5a32c7f 74or using the new syntax available only from v5.6 onward:
aa689395 75
f5a32c7f 76 use v5.6.0;
aa689395 77
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78At some point in the future, we may need to decide what to call the
79next big revision. In the .package file used by metaconfig to
80generate Configure, there are two variables that might be relevant:
81$baserev=5 and $package=perl5.
aa689395 82
f5a32c7f 83Perl releases produced by the members of perl5-porters are usually
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84available on CPAN in the F<src/5.0/maint> and F<src/5.0/devel>
85directories.
aa689395 86
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87=head2 Maintenance and Development Subversions
88
f5a32c7f 89The first rule of maintenance work is "First, do no harm."
7b5757d1 90
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91Trial releases of bug-fix maintenance releases are announced on
92perl5-porters. Trial releases use the new subversion number (to avoid
93testers installing it over the previous release) and include a 'local
f391b661 94patch' entry in F<patchlevel.h>. The distribution file contains the
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95string C<MAINT_TRIAL> to make clear that the file is not meant for
96public consumption.
fb73857a 97
e04b929a 98In general, the names of official distribution files for the public
f5a32c7f 99always match the regular expression:
e04b929a 100
f5a32c7f 101 ^perl\d+\.(\d+)\.\d+(-MAINT_TRIAL_\d+)\.tar\.gz$
e04b929a 102
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103C<$1> in the pattern is always an even number for maintenance
104versions, and odd for developer releases.
e04b929a 105
efc41c8e 106In the past it has been observed that pumpkings tend to invent new
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107naming conventions on the fly. If you are a pumpking, before you
108invent a new name for any of the three types of perl distributions,
109please inform the guys from the CPAN who are doing indexing and
110provide the trees of symlinks and the like. They will have to know
111I<in advance> what you decide.
20f245af 112
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113=head2 Why is it called the patch pumpkin?
114
115Chip Salzenberg gets credit for that, with a nod to his cow orker,
116David Croy. We had passed around various names (baton, token, hot
117potato) but none caught on. Then, Chip asked:
118
119[begin quote]
120
121 Who has the patch pumpkin?
122
123To explain: David Croy once told me once that at a previous job,
124there was one tape drive and multiple systems that used it for backups.
125But instead of some high-tech exclusion software, they used a low-tech
126method to prevent multiple simultaneous backups: a stuffed pumpkin.
127No one was allowed to make backups unless they had the "backup pumpkin".
128
129[end quote]
130
131The name has stuck.
132
a6968aa6 133=head1 Philosophical Issues in Patching and Porting Perl
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134
135There are no absolute rules, but there are some general guidelines I
136have tried to follow as I apply patches to the perl sources.
137(This section is still under construction.)
138
139=head2 Solve problems as generally as possible
140
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141Never implement a specific restricted solution to a problem when you
142can solve the same problem in a more general, flexible way.
143
144For example, for dynamic loading to work on some SVR4 systems, we had
145to build a shared libperl.so library. In order to build "FAT" binaries
146on NeXT 4.0 systems, we had to build a special libperl library. Rather
147than continuing to build a contorted nest of special cases, I
148generalized the process of building libperl so that NeXT and SVR4 users
149could still get their work done, but others could build a shared
150libperl if they wanted to as well.
aa689395 151
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152Contain your changes carefully. Assume nothing about other operating
153systems, not even closely related ones. Your changes must not affect
154other platforms.
155
156Spy shamelessly on how similar patching or porting issues have been
157settled elsewhere.
158
159If feasible, try to keep filenames 8.3-compliant to humor those poor
160souls that get joy from running Perl under such dire limitations.
f391b661 161There's a script, F<check83.pl>, for keeping your nose 8.3-clean.
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162In a similar vein, do not create files or directories which differ only
163in case (upper versus lower).
a6968aa6 164
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165=head2 Seek consensus on major changes
166
167If you are making big changes, don't do it in secret. Discuss the
168ideas in advance on perl5-porters.
169
170=head2 Keep the documentation up-to-date
171
172If your changes may affect how users use perl, then check to be sure
173that the documentation is in sync with your changes. Be sure to
174check all the files F<pod/*.pod> and also the F<INSTALL> document.
175
176Consider writing the appropriate documentation first and then
7b5757d1 177implementing your change to correspond to the documentation.
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178
179=head2 Avoid machine-specific #ifdef's
180
181To the extent reasonable, try to avoid machine-specific #ifdef's in
182the sources. Instead, use feature-specific #ifdef's. The reason is
183that the machine-specific #ifdef's may not be valid across major
184releases of the operating system. Further, the feature-specific tests
185may help out folks on another platform who have the same problem.
186
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187=head2 Machine-specific files
188
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189=over 4
190
191=item source code
192
a6968aa6 193If you have many machine-specific #defines or #includes, consider
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194creating an "osish.h" (F<os2ish.h>, F<vmsish.h>, and so on) and including
195that in F<perl.h>. If you have several machine-specific files (function
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196emulations, function stubs, build utility wrappers) you may create a
197separate subdirectory (djgpp, win32) and put the files in there.
98dddfbd 198Remember to update C<MANIFEST> when you add files.
a6968aa6 199
ff935051 200If your system supports dynamic loading but none of the existing
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201methods at F<ext/DynaLoader/dl_*.xs> work for you, you must write
202a new one. Study the existing ones to see what kind of interface
203you must supply.
204
205=item build hints
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206
207There are two kinds of hints: hints for building Perl and hints for
208extensions. The former live in the C<hints> subdirectory, the latter
209in C<ext/*/hints> subdirectories.
210
211The top level hints are Bourne-shell scripts that set, modify and
212unset appropriate Configure variables, based on the Configure command
213line options and possibly existing config.sh and Policy.sh files from
214previous Configure runs.
215
76ba0908 216The extension hints are written in Perl (by the time they are used
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217miniperl has been built) and control the building of their respective
218extensions. They can be used to for example manipulate compilation
219and linking flags.
220
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221=item build and installation Makefiles, scripts, and so forth
222
223Sometimes you will also need to tweak the Perl build and installation
224procedure itself, like for example F<Makefile.SH> and F<installperl>.
225Tread very carefully, even more than usual. Contain your changes
226with utmost care.
a6968aa6 227
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228=item test suite
229
230Many of the tests in C<t> subdirectory assume machine-specific things
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231like existence of certain functions, something about filesystem
232semantics, certain external utilities and their error messages. Use
233the C<$^O> and the C<Config> module (which contains the results of the
234Configure run, in effect the C<config.sh> converted to Perl) to either
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235skip (preferably not) or customize (preferable) the tests for your
236platform.
237
238=item modules
239
240Certain standard modules may need updating if your operating system
241sports for example a native filesystem naming. You may want to update
242some or all of the modules File::Basename, File::Spec, File::Path, and
243File::Copy to become aware of your native filesystem syntax and
244peculiarities.
245
b972f109 246Remember to have a $VERSION in the modules. You can use the
f391b661 247F<Porting/checkVERSION.pl> script for checking this.
b972f109 248
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249=item documentation
250
251If your operating system comes from outside UNIX you almost certainly
252will have differences in the available operating system functionality
253(missing system calls, different semantics, whatever). Please
254document these at F<pod/perlport.pod>. If your operating system is
255the first B<not> to have a system call also update the list of
256"portability-bewares" at the beginning of F<pod/perlfunc.pod>.
257
258A file called F<README.youros> at the top level that explains things
259like how to install perl at this platform, where to get any possibly
260required additional software, and for example what test suite errors
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261to expect, is nice too. Such files are in the process of being written
262in pod format and will eventually be renamed F<INSTALL.youros>.
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263
264You may also want to write a separate F<.pod> file for your operating
265system to tell about existing mailing lists, os-specific modules,
266documentation, whatever. Please name these along the lines of
267F<perl>I<youros>.pod. [unfinished: where to put this file (the pod/
268subdirectory, of course: but more importantly, which/what index files
269should be updated?)]
270
271=back
a6968aa6 272
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273=head2 Allow for lots of testing
274
275We should never release a main version without testing it as a
276subversion first.
277
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278=head2 Test popular applications and modules.
279
280We should never release a main version without testing whether or not
281it breaks various popular modules and applications. A partial list of
282such things would include majordomo, metaconfig, apache, Tk, CGI,
283libnet, and libwww, to name just a few. Of course it's quite possible
284that some of those things will be just plain broken and need to be fixed,
285but, in general, we ought to try to avoid breaking widely-installed
286things.
287
98dddfbd 288=head2 Automated generation of derivative files
aa689395 289
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290The F<embed.h>, F<keywords.h>, F<opcode.h>, F<regcharclass.h>,
291F<l1_char_class_tab.h>, and F<perltoc.pod> files
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292are all automatically generated by perl scripts. In general, don't
293patch these directly; patch the data files instead.
294
295F<Configure> and F<config_h.SH> are also automatically generated by
296B<metaconfig>. In general, you should patch the metaconfig units
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297instead of patching these files directly. However, very minor changes
298to F<Configure> may be made in between major sync-ups with the
299metaconfig units, which tends to be complicated operations. But be
300careful, this can quickly spiral out of control. Running metaconfig
301is not really hard.
aa689395 302
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303Also F<Makefile> is automatically produced from F<Makefile.SH>.
304In general, look out for all F<*.SH> files.
305
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306Finally, the sample files in the F<Porting/> subdirectory are
307generated automatically by the script F<U/mksample> included
308with the metaconfig units. See L<"run metaconfig"> below for
309information on obtaining the metaconfig units.
310
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311=head1 How to Make a Distribution
312
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313This section has now been expanded and moved into its own file,
314F<Porting/release_managers_guide.pod>.
aa689395 315
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316I've kept some of the subsections here for now, as they don't directly
317relate to building a release any more, but still contain what might be
f6af4394 318useful information - DAPM 7/2009.
05ff1fbb 319
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320=head2 run metaconfig
321
322If you need to make changes to Configure or config_h.SH, it may be best to
323change the appropriate metaconfig units instead, and regenerate Configure.
324
325 metaconfig -m
326
f391b661 327will regenerate F<Configure> and F<config_h.SH>. Much more information
20f245af 328on obtaining and running metaconfig is in the F<U/README> file
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329that comes with Perl's metaconfig units.
330
331Since metaconfig is hard to change, running correction scripts after
332this generation is sometimes needed. Configure gained complexity over
333time, and the order in which config_h.SH is generated can cause havoc
334when compiling perl. Therefor, you need to run Porting/config_h.pl
335after that generation. All that and more is described in the README
336files that come with the metaunits.
337
338Perl's metaconfig units should be available on CPAN. A set of units
339that will work with perl5.9.x is in a file with a name similar to
f391b661 340F<mc_units-20070423.tgz> under L<http://www.cpan.org/authors/id/H/HM/HMBRAND/>.
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341The mc_units tar file should be unpacked in your main perl source directory.
342Note: those units were for use with 5.9.x. There may have been changes since
343then. Check for later versions or contact perl5-porters@perl.org to obtain a
20f245af 344pointer to the current version.
aa689395 345
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346Alternatively, do consider if the F<*ish.h> files or the hint files might be
347a better place for your changes.
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348
349=head2 MANIFEST
350
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351If you are using metaconfig to regenerate Configure, then you should note
352that metaconfig actually uses MANIFEST.new, so you want to be sure
353MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new
354distinction particularly useful, but that's probably because I still haven't
355learned how to use the full suite of tools in the dist distribution.
356
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357
358=head2 Run Configure
359
360This will build a config.sh and config.h. You can skip this if you haven't
693762b4 361changed Configure or config_h.SH at all. I use the following command
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363 sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \
364 -Dcf_by='yourname' \
365 -Dcf_email='yourname@yourhost.yourplace.com' \
366 -Dperladmin='yourname@yourhost.yourplace.com' \
367 -Dmydomain='.yourplace.com' \
368 -Dmyhostname='yourhost' \
369 -des
aa689395 370
693762b4 371=head2 Update Porting/config.sh and Porting/config_H
dfe9444c 372
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373[XXX
374This section needs revision. We're currently working on easing
375the task of keeping the vms, win32, and plan9 config.sh info
376up-to-date. The plan is to use keep up-to-date 'canned' config.sh
377files in the appropriate subdirectories and then generate 'canned'
378config.h files for vms, win32, etc. from the generic config.sh file.
379This is to ease maintenance. When Configure gets updated, the parts
380sometimes get scrambled around, and the changes in config_H can
381sometimes be very hard to follow. config.sh, on the other hand, can
382safely be sorted, so it's easy to track (typically very small) changes
d7f8936a 383to config.sh and then propagate them to a canned 'config.h' by any
693762b4 384number of means, including a perl script in win32/ or carrying
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385F<config.sh> and F<config_h.SH> to a Unix system and running sh
386config_h.SH.) Vms uses F<configure.com> to generate its own F<config.sh>
387and F<config.h>. If you want to add a new variable to F<config.sh> check
76ba0908 388with vms folk how to add it to configure.com too.
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389XXX]
390
f391b661 391The F<Porting/config.sh> and F<Porting/config_H> files are provided to
693762b4 392help those folks who can't run Configure. It is important to keep
f391b661 393them up-to-date. If you have changed F<config_h.SH>, those changes must
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394be reflected in config_H as well. (The name config_H was chosen to
395distinguish the file from config.h even on case-insensitive file systems.)
396Simply edit the existing config_H file; keep the first few explanatory
397lines and then copy your new config.h below.
aa689395 398
76ba0908 399It may also be necessary to update win32/config.?c, and
f391b661 400F<plan9/config.plan9>, though you should be quite careful in doing so if
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401you are not familiar with those systems. You might want to issue your
402patch with a promise to quickly issue a follow-up that handles those
403directories.
404
0de566d7 405=head2 make regen_perly
aa689395 406
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407If F<perly.y> has been edited, it is necessary to run this target to rebuild
408F<perly.h>, F<perly.act> and F<perly.tab>. In fact this target just runs the Perl
409script F<regen_perly.pl>. Note that F<perly.c> is I<not> rebuilt; this is just a
0de566d7 410plain static file now.
aa689395 411
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412This target relies on you having Bison installed on your system. Running
413the target will tell you if you haven't got the right version, and if so,
414where to get the right one. Or if you prefer, you could hack
f391b661 415F<regen_perly.pl> to work with your version of Bison. The important things
0de566d7 416are that the regexes can still extract out the right chunks of the Bison
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417output into F<perly.act> and F<perly.tab>, and that the contents of those two
418files, plus F<perly.h>, are functionally equivalent to those produced by the
0de566d7 419supported version of Bison.
ebb99254 420
0de566d7 421Note that in the old days, you had to do C<make run_byacc> instead.
aa689395 422
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423=head2 make regen_all
424
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425This target takes care of the regen_headers target.
426(It used to also call the regen_pods target, but that has been eliminated.)
76ba0908 427
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428=head2 make regen_headers
429
430The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically
431generated by perl scripts. Since the user isn't guaranteed to have a
432working perl, we can't require the user to generate them. Hence you have
433to, if you're making a distribution.
434
435I used to include rules like the following in the makefile:
436
437 # The following three header files are generated automatically
438 # The correct versions should be already supplied with the perl kit,
439 # in case you don't have perl or 'sh' available.
440 # The - is to ignore error return codes in case you have the source
441 # installed read-only or you don't have perl yet.
442 keywords.h: keywords.pl
443 @echo "Don't worry if this fails."
444 - perl keywords.pl
445
446
7b5757d1 447However, I got B<lots> of mail consisting of people worrying because the
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448command failed. I eventually decided that I would save myself time
449and effort by manually running C<make regen_headers> myself rather
450than answering all the questions and complaints about the failing
451command.
452
8d698ea9 453=head2 global.sym, and perlio.sym
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454
455Make sure these files are up-to-date. Read the comments in these
f391b661 456files and in F<perl_exp.SH> to see what to do.
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457
458=head2 Binary compatibility
459
8d698ea9 460If you do change F<global.sym> think carefully about
aa689395 461what you are doing. To the extent reasonable, we'd like to maintain
76ba0908 462source and binary compatibility with older releases of perl. That way,
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463extensions built under one version of perl will continue to work with
464new versions of perl.
465
466Of course, some incompatible changes may well be necessary. I'm just
467suggesting that we not make any such changes without thinking carefully
468about them first. If possible, we should provide
469backwards-compatibility stubs. There's a lot of XS code out there.
470Let's not force people to keep changing it.
471
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472=head2 PPPort
473
b2861970 474F<cpan/Devel-PPPort/PPPort.pm> needs to be synchronized to include all
f391b661 475new macros added to .h files (normally F<perl.h> and F<XSUB.h>, but others
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476as well). Since chances are that when a new macro is added the
477committer will forget to update F<PPPort.pm>, it's the best to diff for
478changes in .h files when making a new release and making sure that
479F<PPPort.pm> contains them all.
480
481The pumpking can delegate the synchronization responsibility to anybody
482else, but the release process is the only place where we can make sure
483that no new macros fell through the cracks.
484
15839b60 485
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486=head2 Todo
487
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488The F<pod/perltodo.pod> file contains a roughly-categorized unordered
489list of aspects of Perl that could use enhancement, features that could
490be added, areas that could be cleaned up, and so on. During your term
491as pumpkin-holder, you will probably address some of these issues, and
492perhaps identify others which, while you decide not to address them this
493time around, may be tackled in the future. Update the file to reflect
494the situation as it stands when you hand over the pumpkin.
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495
496You might like, early in your pumpkin-holding career, to see if you
d7f8936a 497can find champions for particular issues on the to-do list: an issue
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498owned is an issue more likely to be resolved.
499
94655993 500There are also some more porting-specific L</Todo> items later in this
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501file.
502
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503=head2 OS/2-specific updates
504
505In the os2 directory is F<diff.configure>, a set of OS/2-specific
506diffs against B<Configure>. If you make changes to Configure, you may
507want to consider regenerating this diff file to save trouble for the
508OS/2 maintainer.
509
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510You can also consider the OS/2 diffs as reminders of portability
511things that need to be fixed in Configure.
512
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513=head2 VMS-specific updates
514
f391b661 515The Perl revision number appears as "perl5" in F<configure.com>.
76ba0908 516It is courteous to update that if necessary.
aa689395 517
3e3baf6d 518
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519=head2 Making a new patch
520
521I find the F<makepatch> utility quite handy for making patches.
522You can obtain it from any CPAN archive under
dbcdbb63 523L<http://www.cpan.org/authors/Johan_Vromans/>. There are a couple
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524of differences between my version and the standard one. I have mine do
525a
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526
527 # Print a reassuring "End of Patch" note so people won't
528 # wonder if their mailer truncated patches.
529 print "\n\nEnd of Patch.\n";
530
3e3baf6d
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531at the end. That's because I used to get questions from people asking
532if their mail was truncated.
533
534It also writes Index: lines which include the new directory prefix
535(change Index: print, approx line 294 or 310 depending on the version,
536to read: print PATCH ("Index: $newdir$new\n");). That helps patches
537work with more POSIX conformant patch programs.
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538
539Here's how I generate a new patch. I'll use the hypothetical
5405.004_07 to 5.004_08 patch as an example.
541
542 # unpack perl5.004_07/
543 gzip -d -c perl5.004_07.tar.gz | tar -xof -
544 # unpack perl5.004_08/
545 gzip -d -c perl5.004_08.tar.gz | tar -xof -
546 makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat
547
548Makepatch will automatically generate appropriate B<rm> commands to remove
549deleted files. Unfortunately, it will not correctly set permissions
550for newly created files, so you may have to do so manually. For example,
551patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable,
552so at the top of the patch, I inserted the following lines:
553
554 # Make a new test
555 touch t/op/gv.t
556 chmod +x t/opt/gv.t
557
558Now, of course, my patch is now wrong because makepatch didn't know I
559was going to do that command, and it patched against /dev/null.
560
561So, what I do is sort out all such shell commands that need to be in the
562patch (including possible mv-ing of files, if needed) and put that in the
563shell commands at the top of the patch. Next, I delete all the patch parts
564of perl5.004_08.pat, leaving just the shell commands. Then, I do the
565following:
566
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567 cd perl5.004_07
568 sh ../perl5.004_08.pat
aa689395 569 cd ..
7b5757d1 570 makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat
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571
572(Note the append to preserve my shell commands.)
573Now, my patch will line up with what the end users are going to do.
574
575=head2 Testing your patch
576
577It seems obvious, but be sure to test your patch. That is, verify that
578it produces exactly the same thing as your full distribution.
579
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580 rm -rf perl5.004_07
581 gzip -d -c perl5.004_07.tar.gz | tar -xf -
582 cd perl5.004_07
583 sh ../perl5.004_08.pat
584 patch -p1 -N < ../perl5.004_08.pat
aa689395 585 cd ..
7b5757d1 586 gdiff -r perl5.004_07 perl5.004_08
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587
588where B<gdiff> is GNU diff. Other diff's may also do recursive checking.
589
590=head2 More testing
591
592Again, it's obvious, but you should test your new version as widely as you
593can. You can be sure you'll hear about it quickly if your version doesn't
594work on both ANSI and pre-ANSI compilers, and on common systems such as
595SunOS 4.1.[34], Solaris, and Linux.
596
597If your changes include conditional code, try to test the different
598branches as thoroughly as you can. For example, if your system
599supports dynamic loading, you can also test static loading with
600
601 sh Configure -Uusedl
602
603You can also hand-tweak your config.h to try out different #ifdef
604branches.
605
d2560b70
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606=head2 Other tests
607
00baac8f
RGS
608=over 4
609
93189314
JH
610=item gcc -ansi -pedantic
611
612Configure -Dgccansipedantic [ -Dcc=gcc ] will enable (via the cflags script,
613not $Config{ccflags}) the gcc strict ANSI C flags -ansi and -pedantic for
614the compilation of the core files on platforms where it knows it can
615do so (like Linux, see cflags.SH for the full list), and on some
616platforms only one (Solaris can do only -pedantic, not -ansi).
617The flag -DPERL_GCC_PEDANTIC also gets added, since gcc does not add
618any internal cpp flag to signify that -pedantic is being used, as it
619does for -ansi (__STRICT_ANSI__).
620
a0426075
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621Note that the -ansi and -pedantic are enabled only for version 3 (and
622later) of gcc, since even gcc version 2.95.4 finds lots of seemingly
623false "value computed not used" errors from Perl.
624
93189314
JH
625The -ansi and -pedantic are useful in catching at least the following
626nonportable practices:
627
628=over 4
629
630=item *
631
632gcc-specific extensions
633
634=item *
635
636lvalue casts
637
638=item *
639
640// C++ comments
641
642=item *
643
644enum trailing commas
645
646=back
647
648The -Dgccansipedantic should be used only when cleaning up the code,
649not for production builds, since otherwise gcc cannot inline certain
650things.
651
d2560b70
RB
652=back
653
d33b2eba 654=head1 Running Purify
f5a32c7f
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655
656Purify is a commercial tool that is helpful in identifying memory
657overruns, wild pointers, memory leaks and other such badness. Perl
658must be compiled in a specific way for optimal testing with Purify.
659
660Use the following commands to test perl with Purify:
661
662 sh Configure -des -Doptimize=-g -Uusemymalloc -Dusemultiplicity \
663 -Accflags=-DPURIFY
664 setenv PURIFYOPTIONS "-chain-length=25"
665 make all pureperl
666 cd t
667 ln -s ../pureperl perl
365a6279 668 setenv PERL_DESTRUCT_LEVEL 2
f5a32c7f
GS
669 ./perl TEST
670
671Disabling Perl's malloc allows Purify to monitor allocations and leaks
672more closely; using Perl's malloc will make Purify report most leaks
673in the "potential" leaks category. Enabling the multiplicity option
674allows perl to clean up thoroughly when the interpreter shuts down, which
675reduces the number of bogus leak reports from Purify. The -DPURIFY
676enables any Purify-specific debugging code in the sources.
677
678Purify outputs messages in "Viewer" windows by default. If you don't have
679a windowing environment or if you simply want the Purify output to
680unobtrusively go to a log file instead of to the interactive window,
681use the following options instead:
682
683 setenv PURIFYOPTIONS "-chain-length=25 -windows=no -log-file=perl.log \
684 -append-logfile=yes"
685
686The only currently known leaks happen when there are compile-time errors
687within eval or require. (Fixing these is non-trivial, unfortunately, but
688they must be fixed eventually.)
689
b432a672 690=head1 Common Gotchas
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691
692=over 4
693
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694=item Probably Prefer POSIX
695
696It's often the case that you'll need to choose whether to do
697something the BSD-ish way or the POSIX-ish way. It's usually not
698a big problem when the two systems use different names for similar
699functions, such as memcmp() and bcmp(). The perl.h header file
700handles these by appropriate #defines, selecting the POSIX mem*()
701functions if available, but falling back on the b*() functions, if
702need be.
703
704More serious is the case where some brilliant person decided to
705use the same function name but give it a different meaning or
706calling sequence :-). getpgrp() and setpgrp() come to mind.
707These are a real problem on systems that aim for conformance to
708one standard (e.g. POSIX), but still try to support the other way
709of doing things (e.g. BSD). My general advice (still not really
710implemented in the source) is to do something like the following.
711Suppose there are two alternative versions, fooPOSIX() and
712fooBSD().
713
714 #ifdef HAS_FOOPOSIX
715 /* use fooPOSIX(); */
716 #else
717 # ifdef HAS_FOOBSD
718 /* try to emulate fooPOSIX() with fooBSD();
719 perhaps with the following: */
720 # define fooPOSIX fooBSD
721 # else
722 # /* Uh, oh. We have to supply our own. */
723 # define fooPOSIX Perl_fooPOSIX
724 # endif
725 #endif
726
727=item Think positively
728
729If you need to add an #ifdef test, it is usually easier to follow if you
730think positively, e.g.
731
732 #ifdef HAS_NEATO_FEATURE
733 /* use neato feature */
734 #else
735 /* use some fallback mechanism */
736 #endif
737
738rather than the more impenetrable
739
740 #ifndef MISSING_NEATO_FEATURE
741 /* Not missing it, so we must have it, so use it */
742 #else
743 /* Are missing it, so fall back on something else. */
744 #endif
745
746Of course for this toy example, there's not much difference. But when
747the #ifdef's start spanning a couple of screen fulls, and the #else's
748are marked something like
749
750 #else /* !MISSING_NEATO_FEATURE */
751
752I find it easy to get lost.
753
754=item Providing Missing Functions -- Problem
755
756Not all systems have all the neat functions you might want or need, so
757you might decide to be helpful and provide an emulation. This is
758sound in theory and very kind of you, but please be careful about what
759you name the function. Let me use the C<pause()> function as an
760illustration.
761
762Perl5.003 has the following in F<perl.h>
763
764 #ifndef HAS_PAUSE
765 #define pause() sleep((32767<<16)+32767)
766 #endif
767
768Configure sets HAS_PAUSE if the system has the pause() function, so
769this #define only kicks in if the pause() function is missing.
770Nice idea, right?
771
772Unfortunately, some systems apparently have a prototype for pause()
773in F<unistd.h>, but don't actually have the function in the library.
774(Or maybe they do have it in a library we're not using.)
775
776Thus, the compiler sees something like
777
778 extern int pause(void);
779 /* . . . */
780 #define pause() sleep((32767<<16)+32767)
781
782and dies with an error message. (Some compilers don't mind this;
783others apparently do.)
784
785To work around this, 5.003_03 and later have the following in perl.h:
786
787 /* Some unistd.h's give a prototype for pause() even though
788 HAS_PAUSE ends up undefined. This causes the #define
789 below to be rejected by the compiler. Sigh.
790 */
791 #ifdef HAS_PAUSE
792 # define Pause pause
793 #else
794 # define Pause() sleep((32767<<16)+32767)
795 #endif
796
797This works.
798
799The curious reader may wonder why I didn't do the following in
800F<util.c> instead:
801
802 #ifndef HAS_PAUSE
803 void pause()
804 {
805 sleep((32767<<16)+32767);
806 }
807 #endif
808
809That is, since the function is missing, just provide it.
810Then things would probably be been alright, it would seem.
811
812Well, almost. It could be made to work. The problem arises from the
813conflicting needs of dynamic loading and namespace protection.
814
815For dynamic loading to work on AIX (and VMS) we need to provide a list
816of symbols to be exported. This is done by the script F<perl_exp.SH>,
8d698ea9 817which reads F<global.sym>. Thus, the C<pause>
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818symbol would have to be added to F<global.sym> So far, so good.
819
820On the other hand, one of the goals of Perl5 is to make it easy to
821either extend or embed perl and link it with other libraries. This
822means we have to be careful to keep the visible namespace "clean".
823That is, we don't want perl's global variables to conflict with
824those in the other application library. Although this work is still
825in progress, the way it is currently done is via the F<embed.h> file.
8d698ea9 826This file is built from the F<global.sym> file,
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827since those files already list the globally visible symbols. If we
828had added C<pause> to global.sym, then F<embed.h> would contain the
829line
830
831 #define pause Perl_pause
832
833and calls to C<pause> in the perl sources would now point to
834C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable,
835it will go looking for C<perl_pause>, which probably won't exist in any
836of the standard libraries. Thus the build of perl will fail.
837
838Those systems where C<HAS_PAUSE> is not defined would be ok, however,
839since they would get a C<Perl_pause> function in util.c. The rest of
840the world would be in trouble.
841
842And yes, this scenario has happened. On SCO, the function C<chsize>
843is available. (I think it's in F<-lx>, the Xenix compatibility
844library.) Since the perl4 days (and possibly before), Perl has
845included a C<chsize> function that gets called something akin to
846
847 #ifndef HAS_CHSIZE
848 I32 chsize(fd, length)
849 /* . . . */
850 #endif
851
852When 5.003 added
853
854 #define chsize Perl_chsize
855
856to F<embed.h>, the compile started failing on SCO systems.
857
858The "fix" is to give the function a different name. The one
859implemented in 5.003_05 isn't optimal, but here's what was done:
860
861 #ifdef HAS_CHSIZE
862 # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */
863 # undef my_chsize
864 # endif
865 # define my_chsize chsize
866 #endif
867
868My explanatory comment in patch 5.003_05 said:
869
870 Undef and then re-define my_chsize from Perl_my_chsize to
871 just plain chsize if this system HAS_CHSIZE. This probably only
872 applies to SCO. This shows the perils of having internal
873 functions with the same name as external library functions :-).
874
875Now, we can safely put C<my_chsize> in F<global.sym>, export it, and
876hide it with F<embed.h>.
877
878To be consistent with what I did for C<pause>, I probably should have
879called the new function C<Chsize>, rather than C<my_chsize>.
880However, the perl sources are quite inconsistent on this (Consider
881New, Mymalloc, and Myremalloc, to name just a few.)
882
883There is a problem with this fix, however, in that C<Perl_chsize>
884was available as a F<libperl.a> library function in 5.003, but it
885isn't available any more (as of 5.003_07). This means that we've
886broken binary compatibility. This is not good.
887
888=item Providing missing functions -- some ideas
889
890We currently don't have a standard way of handling such missing
891function names. Right now, I'm effectively thinking aloud about a
892solution. Some day, I'll try to formally propose a solution.
893
894Part of the problem is that we want to have some functions listed as
895exported but not have their names mangled by embed.h or possibly
896conflict with names in standard system headers. We actually already
897have such a list at the end of F<perl_exp.SH> (though that list is
898out-of-date):
899
900 # extra globals not included above.
901 cat <<END >> perl.exp
902 perl_init_ext
903 perl_init_fold
904 perl_init_i18nl14n
905 perl_alloc
906 perl_construct
907 perl_destruct
908 perl_free
909 perl_parse
910 perl_run
911 perl_get_sv
912 perl_get_av
913 perl_get_hv
914 perl_get_cv
915 perl_call_argv
916 perl_call_pv
917 perl_call_method
918 perl_call_sv
919 perl_requirepv
920 safecalloc
921 safemalloc
922 saferealloc
923 safefree
924
925This still needs much thought, but I'm inclined to think that one
926possible solution is to prefix all such functions with C<perl_> in the
927source and list them along with the other C<perl_*> functions in
928F<perl_exp.SH>.
929
930Thus, for C<chsize>, we'd do something like the following:
931
932 /* in perl.h */
933 #ifdef HAS_CHSIZE
934 # define perl_chsize chsize
935 #endif
936
937then in some file (e.g. F<util.c> or F<doio.c>) do
938
939 #ifndef HAS_CHSIZE
940 I32 perl_chsize(fd, length)
941 /* implement the function here . . . */
942 #endif
943
944Alternatively, we could just always use C<chsize> everywhere and move
945C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would
946probably be fine as long as our C<chsize> function agreed with all the
947C<chsize> function prototypes in the various systems we'll be using.
948As long as the prototypes in actual use don't vary that much, this is
949probably a good alternative. (As a counter-example, note how Configure
950and perl have to go through hoops to find and use get Malloc_t and
951Free_t for C<malloc> and C<free>.)
952
953At the moment, this latter option is what I tend to prefer.
954
955=item All the world's a VAX
956
957Sorry, showing my age:-). Still, all the world is not BSD 4.[34],
958SVR4, or POSIX. Be aware that SVR3-derived systems are still quite
959common (do you have any idea how many systems run SCO?) If you don't
960have a bunch of v7 manuals handy, the metaconfig units (by default
961installed in F</usr/local/lib/dist/U>) are a good resource to look at
962for portability.
963
964=back
965
966=head1 Miscellaneous Topics
967
968=head2 Autoconf
969
970Why does perl use a metaconfig-generated Configure script instead of an
971autoconf-generated configure script?
972
973Metaconfig and autoconf are two tools with very similar purposes.
974Metaconfig is actually the older of the two, and was originally written
975by Larry Wall, while autoconf is probably now used in a wider variety of
976packages. The autoconf info file discusses the history of autoconf and
977how it came to be. The curious reader is referred there for further
978information.
979
980Overall, both tools are quite good, I think, and the choice of which one
981to use could be argued either way. In March, 1994, when I was just
982starting to work on Configure support for Perl5, I considered both
983autoconf and metaconfig, and eventually decided to use metaconfig for the
984following reasons:
985
986=over 4
987
988=item Compatibility with Perl4
989
990Perl4 used metaconfig, so many of the #ifdef's were already set up for
991metaconfig. Of course metaconfig had evolved some since Perl4's days,
992but not so much that it posed any serious problems.
993
994=item Metaconfig worked for me
995
d1be9408 996My system at the time was Interactive 2.2, an SVR3.2/386 derivative that
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997also had some POSIX support. Metaconfig-generated Configure scripts
998worked fine for me on that system. On the other hand, autoconf-generated
999scripts usually didn't. (They did come quite close, though, in some
1000cases.) At the time, I actually fetched a large number of GNU packages
1001and checked. Not a single one configured and compiled correctly
1002out-of-the-box with the system's cc compiler.
1003
1004=item Configure can be interactive
1005
1006With both autoconf and metaconfig, if the script works, everything is
1007fine. However, one of my main problems with autoconf-generated scripts
1008was that if it guessed wrong about something, it could be B<very> hard to
1009go back and fix it. For example, autoconf always insisted on passing the
1010-Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I
1011wanted or needed for that package. There was no way short of editing the
1012configure script to turn this off. You couldn't just edit the resulting
1013Makefile at the end because the -Xp flag influenced a number of other
1014configure tests.
1015
1016Metaconfig's Configure scripts, on the other hand, can be interactive.
1017Thus if Configure is guessing things incorrectly, you can go back and fix
1018them. This isn't as important now as it was when we were actively
1019developing Configure support for new features such as dynamic loading,
1020but it's still useful occasionally.
1021
1022=item GPL
1023
1024At the time, autoconf-generated scripts were covered under the GNU Public
1025License, and hence weren't suitable for inclusion with Perl, which has a
1026different licensing policy. (Autoconf's licensing has since changed.)
1027
1028=item Modularity
1029
1030Metaconfig builds up Configure from a collection of discrete pieces
1031called "units". You can override the standard behavior by supplying your
1032own unit. With autoconf, you have to patch the standard files instead.
1033I find the metaconfig "unit" method easier to work with. Others
1034may find metaconfig's units clumsy to work with.
1035
1036=back
1037
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1038=head2 Why isn't there a directory to override Perl's library?
1039
1040Mainly because no one's gotten around to making one. Note that
1041"making one" involves changing perl.c, Configure, config_h.SH (and
1042associated files, see above), and I<documenting> it all in the
1043INSTALL file.
1044
1045Apparently, most folks who want to override one of the standard library
1046files simply do it by overwriting the standard library files.
1047
1048=head2 APPLLIB
1049
1050In the perl.c sources, you'll find an undocumented APPLLIB_EXP
1051variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are
1052documented in config_h.SH). Here's what APPLLIB_EXP is for, from
1053a mail message from Larry:
1054
1055 The main intent of APPLLIB_EXP is for folks who want to send out a
1056 version of Perl embedded in their product. They would set the symbol
1057 to be the name of the library containing the files needed to run or to
1058 support their particular application. This works at the "override"
1059 level to make sure they get their own versions of any library code that
1060 they absolutely must have configuration control over.
1061
1062 As such, I don't see any conflict with a sysadmin using it for a
1063 override-ish sort of thing, when installing a generic Perl. It should
1064 probably have been named something to do with overriding though. Since
1065 it's undocumented we could still change it... :-)
1066
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1067Given that it's already there, you can use it to override distribution modules.
1068One way to do that is to add
1069
453a1e5f 1070 ccflags="$ccflags -DAPPLLIB_EXP=\"/my/override\""
a4b0381d 1071
24f415b4 1072to your config.over file. (You have to be particularly careful to get the
453a1e5f
MB
1073double quotes in. APPLLIB_EXP must be a valid C string. It might
1074actually be easier to just #define it yourself in perl.c.)
24f415b4
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1075
1076Then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB. Perl will
1077also search architecture-specific and version-specific subdirectories of
1078APPLLIB_EXP.
aa689395 1079
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1080=head2 Shared libperl.so location
1081
1082Why isn't the shared libperl.so installed in /usr/lib/ along
1083with "all the other" shared libraries? Instead, it is installed
1084in $archlib, which is typically something like
1085
1086 /usr/local/lib/perl5/archname/5.00404
1087
1088and is architecture- and version-specific.
1089
1090The basic reason why a shared libperl.so gets put in $archlib is so that
1091you can have more than one version of perl on the system at the same time,
1092and have each refer to its own libperl.so.
1093
1094Three examples might help. All of these work now; none would work if you
1095put libperl.so in /usr/lib.
1096
1097=over
1098
1099=item 1.
1100
1101Suppose you want to have both threaded and non-threaded perl versions
1102around. Configure will name both perl libraries "libperl.so" (so that
1103you can link to them with -lperl). The perl binaries tell them apart
1104by having looking in the appropriate $archlib directories.
1105
1106=item 2.
1107
1108Suppose you have perl5.004_04 installed and you want to try to compile
1109it again, perhaps with different options or after applying a patch.
1110If you already have libperl.so installed in /usr/lib/, then it may be
1111either difficult or impossible to get ld.so to find the new libperl.so
1112that you're trying to build. If, instead, libperl.so is tucked away in
1113$archlib, then you can always just change $archlib in the current perl
1114you're trying to build so that ld.so won't find your old libperl.so.
1115(The INSTALL file suggests you do this when building a debugging perl.)
1116
1117=item 3.
1118
1119The shared perl library is not a "well-behaved" shared library with
1120proper major and minor version numbers, so you can't necessarily
1121have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose
1122perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05
1123were to install /usr/lib/libperl.so.4.5. Now, when you try to run
1124perl5.004_04, ld.so might try to load libperl.so.4.5, since it has
1125the right "major version" number. If this works at all, it almost
1126certainly defeats the reason for keeping perl5.004_04 around. Worse,
47e01c32 1127with development subversions, you certainly can't guarantee that
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1128libperl.so.4.4 and libperl.so.4.55 will be compatible.
1129
1130Anyway, all this leads to quite obscure failures that are sure to drive
1131casual users crazy. Even experienced users will get confused :-). Upon
1132reflection, I'd say leave libperl.so in $archlib.
1133
94655993
SR
1134=back
1135
1136=head2 Indentation style
2032ff04 1137
94655993 1138Over the years Perl has become a mishmash of
2032ff04
JH
1139various indentation styles, but the original "Larry style" can
1140probably be restored with (GNU) indent somewhat like this:
1141
1142 indent -kr -nce -psl -sc
1143
55c0ed8c
JH
1144A more ambitious solution would also specify a list of Perl specific
1145types with -TSV -TAV -THV .. -TMAGIC -TPerlIO ... but that list would
1146be quite ungainly. Also note that GNU indent also doesn't do aligning
1147of consecutive assignments, which would truly wreck the layout in
1148places like sv.c:Perl_sv_upgrade() or sv.c:Perl_clone_using().
1149Similarly nicely aligned &&s, ||s and ==s would not be respected.
2032ff04 1150
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1151=head1 Upload Your Work to CPAN
1152
1153You can upload your work to CPAN if you have a CPAN id. Check out
f391b661 1154L<http://www.cpan.org/modules/04pause.html> for information on
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1155_PAUSE_, the Perl Author's Upload Server.
1156
1157I typically upload both the patch file, e.g. F<perl5.004_08.pat.gz>
1158and the full tar file, e.g. F<perl5.004_08.tar.gz>.
1159
1160If you want your patch to appear in the F<src/5.0/unsupported>
1161directory on CPAN, send e-mail to the CPAN master librarian. (Check
a93751fa 1162out http://www.cpan.org/CPAN.html ).
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1163
1164=head1 Help Save the World
1165
1166You should definitely announce your patch on the perl5-porters list.
1167You should also consider announcing your patch on
1168comp.lang.perl.announce, though you should make it quite clear that a
1169subversion is not a production release, and be prepared to deal with
1170people who will not read your disclaimer.
1171
1172=head1 Todo
1173
1174Here, in no particular order, are some Configure and build-related
1175items that merit consideration. This list isn't exhaustive, it's just
1176what I came up with off the top of my head.
1177
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1178=head2 Adding missing library functions to Perl
1179
1180The perl Configure script automatically determines which headers and
1181functions you have available on your system and arranges for them to be
1182included in the compilation and linking process. Occasionally, when porting
1183perl to an operating system for the first time, you may find that the
1184operating system is missing a key function. While perl may still build
1185without this function, no perl program will be able to reference the missing
1186function. You may be able to write the missing function yourself, or you
1187may be able to find the missing function in the distribution files for
1188another software package. In this case, you need to instruct the perl
1189configure-and-build process to use your function. Perform these steps.
1190
1191=over 3
1192
1193=item *
1194
2ecb232b 1195Code and test the function you wish to add. Test it carefully; you will
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PG
1196have a much easier time debugging your code independently than when it is a
1197part of perl.
1198
1199=item *
1200
1201Here is an implementation of the POSIX truncate function for an operating
1202system (VOS) that does not supply one, but which does supply the ftruncate()
1203function.
1204
1205 /* Beginning of modification history */
1206 /* Written 02-01-02 by Nick Ing-Simmons (nick@ing-simmons.net) */
1207 /* End of modification history */
1208
1209 /* VOS doesn't supply a truncate function, so we build one up
1210 from the available POSIX functions. */
1211
1212 #include <fcntl.h>
1213 #include <sys/types.h>
1214 #include <unistd.h>
1215
1216 int
1217 truncate(const char *path, off_t len)
1218 {
1219 int fd = open(path,O_WRONLY);
1220 int code = -1;
1221 if (fd >= 0) {
1222 code = ftruncate(fd,len);
1223 close(fd);
1224 }
1225 return code;
1226 }
1227
1228Place this file into a subdirectory that has the same name as the operating
1229system. This file is named perl/vos/vos.c
1230
1231=item *
1232
1233If your operating system has a hints file (in perl/hints/XXX.sh for an
1234operating system named XXX), then start with it. If your operating system
1235has no hints file, then create one. You can use a hints file for a similar
1236operating system, if one exists, as a template.
1237
1238=item *
1239
1240Add lines like the following to your hints file. The first line
1241(d_truncate="define") instructs Configure that the truncate() function
1242exists. The second line (archobjs="vos.o") instructs the makefiles that the
1243perl executable depends on the existence of a file named "vos.o". (Make
1244will automatically look for "vos.c" and compile it with the same options as
1245the perl source code). The final line ("test -h...") adds a symbolic link
1246to the top-level directory so that make can find vos.c. Of course, you
1247should use your own operating system name for the source file of extensions,
1248not "vos.c".
1249
1250 # VOS does not have truncate() but we supply one in vos.c
1251 d_truncate="define"
1252 archobjs="vos.o"
1253
1254 # Help gmake find vos.c
1255 test -h vos.c || ln -s vos/vos.c vos.c
1256
1257The hints file is a series of shell commands that are run in the top-level
1258directory (the "perl" directory). Thus, these commands are simply executed
1259by Configure at an appropriate place during its execution.
1260
1261=item *
1262
1263At this point, you can run the Configure script and rebuild perl. Carefully
1264test the newly-built perl to ensure that normal paths, and error paths,
1265behave as you expect.
1266
1267=back
1268
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1269=head2 Good ideas waiting for round tuits
1270
1271=over 4
1272
c4f23d77 1273=item Configure -Dsrc=/blah/blah
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1274
1275We should be able to emulate B<configure --srcdir>. Tom Tromey
1276tromey@creche.cygnus.com has submitted some patches to
c4f23d77
AD
1277the dist-users mailing list along these lines. They have been folded
1278back into the main distribution, but various parts of the perl
1279Configure/build/install process still assume src='.'.
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1280
1281=item Hint file fixes
1282
1283Various hint files work around Configure problems. We ought to fix
1284Configure so that most of them aren't needed.
1285
1286=item Hint file information
1287
1288Some of the hint file information (particularly dynamic loading stuff)
1289ought to be fed back into the main metaconfig distribution.
1290
1291=back
1292
1293=head2 Probably good ideas waiting for round tuits
1294
1295=over 4
1296
1297=item GNU configure --options
1298
1299I've received sensible suggestions for --exec_prefix and other
1300GNU configure --options. It's not always obvious exactly what is
1301intended, but this merits investigation.
1302
1303=item make clean
1304
1305Currently, B<make clean> isn't all that useful, though
1306B<make realclean> and B<make distclean> are. This needs a bit of
1307thought and documentation before it gets cleaned up.
1308
1309=item Try gcc if cc fails
1310
1311Currently, we just give up.
1312
1313=item bypassing safe*alloc wrappers
1314
1315On some systems, it may be safe to call the system malloc directly
1316without going through the util.c safe* layers. (Such systems would
1317accept free(0), for example.) This might be a time-saver for systems
1318that already have a good malloc. (Recent Linux libc's apparently have
1319a nice malloc that is well-tuned for the system.)
1320
1321=back
1322
1323=head2 Vague possibilities
1324
1325=over 4
1326
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PP
1327=item gconvert replacement
1328
1329Maybe include a replacement function that doesn't lose data in rare
1330cases of coercion between string and numerical values.
1331
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1332=item Improve makedepend
1333
1334The current makedepend process is clunky and annoyingly slow, but it
1335works for most folks. Alas, it assumes that there is a filename
1336$firstmakefile that the B<make> command will try to use before it uses
1337F<Makefile>. Such may not be the case for all B<make> commands,
1338particularly those on non-Unix systems.
1339
1340Probably some variant of the BSD F<.depend> file will be useful.
1341We ought to check how other packages do this, if they do it at all.
1342We could probably pre-generate the dependencies (with the exception of
1343malloc.o, which could probably be determined at F<Makefile.SH>
1344extraction time.
1345
1346=item GNU Makefile standard targets
1347
1348GNU software generally has standardized Makefile targets. Unless we
1349have good reason to do otherwise, I see no reason not to support them.
1350
1351=item File locking
1352
1353Somehow, straighten out, document, and implement lockf(), flock(),
76ba0908
PK
1354and/or fcntl() file locking. It's a mess. See $d_fcntl_can_lock
1355in recent config.sh files though.
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1356
1357=back
1358
4bb101f2
JH
1359=head2 Copyright Issues
1360
1361The following is based on the consensus of a couple of IPR lawyers,
1362but it is of course not a legally binding statement, just a common
1363sense summary.
1364
1365=over 4
1366
1367=item *
1368
1369Tacking on copyright statements is unnecessary to begin with because
1370of the Berne convention. But assuming you want to go ahead...
1371
1372=item *
1373
1374The right form of a copyright statement is
1375
1376 Copyright (C) Year, Year, ... by Someone
1377
1378The (C) is not required everywhere but it doesn't hurt and in certain
1379jurisdictions it is required, so let's leave it in. (Yes, it's true
1380that in some jurisdictions the "(C)" is not legally binding, one should
1381use the true ringed-C. But we don't have that character available for
1382Perl's source code.)
1383
1384The years must be listed out separately. Year-Year is not correct.
1385Only the years when the piece has changed 'significantly' may be added.
1386
1387=item *
1388
1389One cannot give away one's copyright trivially. One can give one's
1390copyright away by using public domain, but even that requires a little
1391bit more than just saying 'this is in public domain'. (What it
1392exactly requires depends on your jurisdiction.) But barring public
1393domain, one cannot "transfer" one's copyright to another person or
1394entity. In the context of software, it means that contributors cannot
1395give away their copyright or "transfer" it to the "owner" of the software.
1396
1397Also remember that in many cases if you are employed by someone,
1398your work may be copyrighted to your employer, even when you are
1399contributing on your own time (this all depends on too many things
1400to list here). But the bottom line is that you definitely can't give
1401away a copyright you may not even have.
1402
1403What is possible, however, is that the software can simply state
1404
1405 Copyright (C) Year, Year, ... by Someone and others
1406
1407and then list the "others" somewhere in the distribution.
1408And this is exactly what Perl does. (The "somewhere" is
1409AUTHORS and the Changes* files.)
1410
1411=item *
1412
1413Split files, merged files, and generated files are problematic.
1414The rule of thumb: in split files, copy the copyright years of
1415the original file to all the new files; in merged files make
1416an union of the copyright years of all the old files; in generated
1417files propagate the copyright years of the generating file(s).
1418
1419=item *
1420
1421The files of Perl source code distribution do carry a lot of
1422copyrights, by various people. (There are many copyrights embedded in
1423perl.c, for example.) The most straightforward thing for pumpkings to
1424do is to simply update Larry's copyrights at the beginning of the
1425*.[hcy], x2p/*.[hcy], *.pl, and README files, and leave all other
1426copyrights alone. Doing more than that requires quite a bit of tracking.
1427
1428=back
1429
fb73857a 1430=head1 AUTHORS
aa689395 1431
36816da2 1432Original author: Andy Dougherty doughera@lafayette.edu .
fb73857a
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1433Additions by Chip Salzenberg chip@perl.com and
1434Tim Bunce Tim.Bunce@ig.co.uk .
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1435
1436All opinions expressed herein are those of the authorZ<>(s).
1437
1438=head1 LAST MODIFIED
1439
1c05a96e 14402009-07-08-01 Jesse Vincent