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aa689395 | 1 | =head1 NAME |
2 | ||
3 | Pumpkin - Notes on handling the Perl Patch Pumpkin | |
4 | ||
5 | =head1 SYNOPSIS | |
6 | ||
7 | There is no simple synopsis, yet. | |
8 | ||
9 | =head1 DESCRIPTION | |
10 | ||
98dddfbd JH |
11 | This document attempts to begin to describe some of the considerations |
12 | involved in patching, porting, and maintaining perl. | |
aa689395 | 13 | |
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. | |
17 | ||
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. | |
22 | ||
23 | =head1 Where Do I Get Perl Sources and Related Material? | |
24 | ||
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 | |
7b5757d1 | 27 | http://www.perl.com/CPAN/README.html , which automatically points you to a |
aa689395 | 28 | mirror site "close" to you. |
29 | ||
30 | =head2 Perl5-porters mailing list | |
31 | ||
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. | |
37 | ||
38 | Subscribe by sending the message (in the body of your letter) | |
39 | ||
40 | subscribe perl5-porters | |
41 | ||
42 | to perl5-porters-request@perl.org . | |
43 | ||
fb73857a | 44 | Archives of the list are held at: |
45 | ||
46 | http://www.rosat.mpe-garching.mpg.de/mailing-lists/perl-porters/ | |
47 | ||
aa689395 | 48 | =head1 How are Perl Releases Numbered? |
49 | ||
f5a32c7f GS |
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. | |
7b5757d1 | 55 | |
f5a32c7f GS |
56 | For example, in v5.6.1, the revision number is 5, the version is 6, |
57 | and 1 is the subversion. | |
aa689395 | 58 | |
f5a32c7f GS |
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/1000000>. This | |
62 | can still be used in comparisons. | |
aa689395 | 63 | |
f5a32c7f | 64 | print "You've got an old perl\n" if $] < 5.005_03; |
aa689395 | 65 | |
f5a32c7f | 66 | In 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 | 70 | You can also require particular version (or later) with: |
aa689395 | 71 | |
f5a32c7f | 72 | use 5.006; |
aa689395 | 73 | |
f5a32c7f | 74 | or using the new syntax available only from v5.6 onward: |
aa689395 | 75 | |
f5a32c7f | 76 | use v5.6.0; |
aa689395 | 77 | |
f5a32c7f GS |
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 $package=perl5. | |
aa689395 | 82 | |
f5a32c7f | 83 | Perl releases produced by the members of perl5-porters are usually |
e04b929a GS |
84 | available on CPAN in the F<src/5.0/maint> and F<src/5.0/devel> |
85 | directories. | |
aa689395 | 86 | |
7b5757d1 AD |
87 | =head2 Maintenance and Development Subversions |
88 | ||
f5a32c7f | 89 | The first rule of maintenance work is "First, do no harm." |
7b5757d1 | 90 | |
fb73857a | 91 | Trial releases of bug-fix maintenance releases are announced on |
92 | perl5-porters. Trial releases use the new subversion number (to avoid | |
93 | testers installing it over the previous release) and include a 'local | |
e04b929a GS |
94 | patch' entry in patchlevel.h. The distribution file contains the |
95 | string C<MAINT_TRIAL> to make clear that the file is not meant for | |
96 | public consumption. | |
fb73857a | 97 | |
e04b929a | 98 | In general, the names of official distribution files for the public |
f5a32c7f | 99 | always match the regular expression: |
e04b929a | 100 | |
f5a32c7f | 101 | ^perl\d+\.(\d+)\.\d+(-MAINT_TRIAL_\d+)\.tar\.gz$ |
e04b929a | 102 | |
f5a32c7f GS |
103 | C<$1> in the pattern is always an even number for maintenance |
104 | versions, and odd for developer releases. | |
e04b929a GS |
105 | |
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. | |
20f245af | 112 | |
aa689395 | 113 | =head2 Why is it called the patch pumpkin? |
114 | ||
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: | |
118 | ||
119 | [begin quote] | |
120 | ||
121 | Who has the patch pumpkin? | |
122 | ||
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". | |
128 | ||
129 | [end quote] | |
130 | ||
131 | The name has stuck. | |
132 | ||
a6968aa6 | 133 | =head1 Philosophical Issues in Patching and Porting Perl |
aa689395 | 134 | |
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.) | |
138 | ||
139 | =head2 Solve problems as generally as possible | |
140 | ||
7b5757d1 AD |
141 | Never implement a specific restricted solution to a problem when you |
142 | can solve the same problem in a more general, flexible way. | |
143 | ||
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. | |
aa689395 | 151 | |
a6968aa6 JH |
152 | Contain your changes carefully. Assume nothing about other operating |
153 | systems, not even closely related ones. Your changes must not affect | |
154 | other platforms. | |
155 | ||
156 | Spy shamelessly on how similar patching or porting issues have been | |
157 | settled elsewhere. | |
158 | ||
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 | ||
aa689395 | 162 | =head2 Seek consensus on major changes |
163 | ||
164 | If you are making big changes, don't do it in secret. Discuss the | |
165 | ideas in advance on perl5-porters. | |
166 | ||
167 | =head2 Keep the documentation up-to-date | |
168 | ||
169 | If your changes may affect how users use perl, then check to be sure | |
170 | that the documentation is in sync with your changes. Be sure to | |
171 | check all the files F<pod/*.pod> and also the F<INSTALL> document. | |
172 | ||
173 | Consider writing the appropriate documentation first and then | |
7b5757d1 | 174 | implementing your change to correspond to the documentation. |
aa689395 | 175 | |
176 | =head2 Avoid machine-specific #ifdef's | |
177 | ||
178 | To the extent reasonable, try to avoid machine-specific #ifdef's in | |
179 | the sources. Instead, use feature-specific #ifdef's. The reason is | |
180 | that the machine-specific #ifdef's may not be valid across major | |
181 | releases of the operating system. Further, the feature-specific tests | |
182 | may help out folks on another platform who have the same problem. | |
183 | ||
a6968aa6 JH |
184 | =head2 Machine-specific files |
185 | ||
98dddfbd JH |
186 | =over 4 |
187 | ||
188 | =item source code | |
189 | ||
a6968aa6 JH |
190 | If you have many machine-specific #defines or #includes, consider |
191 | creating an "osish.h" (os2ish.h, vmsish.h, and so on) and including | |
192 | that in perl.h. If you have several machine-specific files (function | |
193 | emulations, function stubs, build utility wrappers) you may create a | |
194 | separate subdirectory (djgpp, win32) and put the files in there. | |
98dddfbd | 195 | Remember to update C<MANIFEST> when you add files. |
a6968aa6 | 196 | |
ff935051 | 197 | If your system supports dynamic loading but none of the existing |
98dddfbd JH |
198 | methods at F<ext/DynaLoader/dl_*.xs> work for you, you must write |
199 | a new one. Study the existing ones to see what kind of interface | |
200 | you must supply. | |
201 | ||
202 | =item build hints | |
a6968aa6 JH |
203 | |
204 | There are two kinds of hints: hints for building Perl and hints for | |
205 | extensions. The former live in the C<hints> subdirectory, the latter | |
206 | in C<ext/*/hints> subdirectories. | |
207 | ||
208 | The top level hints are Bourne-shell scripts that set, modify and | |
209 | unset appropriate Configure variables, based on the Configure command | |
210 | line options and possibly existing config.sh and Policy.sh files from | |
211 | previous Configure runs. | |
212 | ||
213 | The extension hints are written Perl (by the time they are used | |
214 | miniperl has been built) and control the building of their respective | |
215 | extensions. They can be used to for example manipulate compilation | |
216 | and linking flags. | |
217 | ||
98dddfbd JH |
218 | =item build and installation Makefiles, scripts, and so forth |
219 | ||
220 | Sometimes you will also need to tweak the Perl build and installation | |
221 | procedure itself, like for example F<Makefile.SH> and F<installperl>. | |
222 | Tread very carefully, even more than usual. Contain your changes | |
223 | with utmost care. | |
a6968aa6 | 224 | |
98dddfbd JH |
225 | =item test suite |
226 | ||
227 | Many of the tests in C<t> subdirectory assume machine-specific things | |
a6968aa6 JH |
228 | like existence of certain functions, something about filesystem |
229 | semantics, certain external utilities and their error messages. Use | |
230 | the C<$^O> and the C<Config> module (which contains the results of the | |
231 | Configure run, in effect the C<config.sh> converted to Perl) to either | |
98dddfbd JH |
232 | skip (preferably not) or customize (preferable) the tests for your |
233 | platform. | |
234 | ||
235 | =item modules | |
236 | ||
237 | Certain standard modules may need updating if your operating system | |
238 | sports for example a native filesystem naming. You may want to update | |
239 | some or all of the modules File::Basename, File::Spec, File::Path, and | |
240 | File::Copy to become aware of your native filesystem syntax and | |
241 | peculiarities. | |
242 | ||
243 | =item documentation | |
244 | ||
245 | If your operating system comes from outside UNIX you almost certainly | |
246 | will have differences in the available operating system functionality | |
247 | (missing system calls, different semantics, whatever). Please | |
248 | document these at F<pod/perlport.pod>. If your operating system is | |
249 | the first B<not> to have a system call also update the list of | |
250 | "portability-bewares" at the beginning of F<pod/perlfunc.pod>. | |
251 | ||
252 | A file called F<README.youros> at the top level that explains things | |
253 | like how to install perl at this platform, where to get any possibly | |
254 | required additional software, and for example what test suite errors | |
255 | to expect, is nice too. | |
256 | ||
257 | You may also want to write a separate F<.pod> file for your operating | |
258 | system to tell about existing mailing lists, os-specific modules, | |
259 | documentation, whatever. Please name these along the lines of | |
260 | F<perl>I<youros>.pod. [unfinished: where to put this file (the pod/ | |
261 | subdirectory, of course: but more importantly, which/what index files | |
262 | should be updated?)] | |
263 | ||
264 | =back | |
a6968aa6 | 265 | |
aa689395 | 266 | =head2 Allow for lots of testing |
267 | ||
268 | We should never release a main version without testing it as a | |
269 | subversion first. | |
270 | ||
6877a1cf AD |
271 | =head2 Test popular applications and modules. |
272 | ||
273 | We should never release a main version without testing whether or not | |
274 | it breaks various popular modules and applications. A partial list of | |
275 | such things would include majordomo, metaconfig, apache, Tk, CGI, | |
276 | libnet, and libwww, to name just a few. Of course it's quite possible | |
277 | that some of those things will be just plain broken and need to be fixed, | |
278 | but, in general, we ought to try to avoid breaking widely-installed | |
279 | things. | |
280 | ||
98dddfbd | 281 | =head2 Automated generation of derivative files |
aa689395 | 282 | |
283 | The F<embed.h>, F<keywords.h>, F<opcode.h>, and F<perltoc.pod> files | |
284 | are all automatically generated by perl scripts. In general, don't | |
285 | patch these directly; patch the data files instead. | |
286 | ||
287 | F<Configure> and F<config_h.SH> are also automatically generated by | |
288 | B<metaconfig>. In general, you should patch the metaconfig units | |
a6968aa6 JH |
289 | instead of patching these files directly. However, very minor changes |
290 | to F<Configure> may be made in between major sync-ups with the | |
291 | metaconfig units, which tends to be complicated operations. But be | |
292 | careful, this can quickly spiral out of control. Running metaconfig | |
293 | is not really hard. | |
aa689395 | 294 | |
98dddfbd JH |
295 | Also F<Makefile> is automatically produced from F<Makefile.SH>. |
296 | In general, look out for all F<*.SH> files. | |
297 | ||
a8119d38 AD |
298 | Finally, the sample files in the F<Porting/> subdirectory are |
299 | generated automatically by the script F<U/mksample> included | |
300 | with the metaconfig units. See L<"run metaconfig"> below for | |
301 | information on obtaining the metaconfig units. | |
302 | ||
aa689395 | 303 | =head1 How to Make a Distribution |
304 | ||
305 | There really ought to be a 'make dist' target, but there isn't. | |
306 | The 'dist' suite of tools also contains a number of tools that I haven't | |
307 | learned how to use yet. Some of them may make this all a bit easier. | |
308 | ||
309 | Here are the steps I go through to prepare a patch & distribution. | |
310 | ||
3e3baf6d TB |
311 | Lots of it could doubtless be automated but isn't. The Porting/makerel |
312 | (make release) perl script does now help automate some parts of it. | |
aa689395 | 313 | |
314 | =head2 Announce your intentions | |
315 | ||
316 | First, you should volunteer out loud to take the patch pumpkin. It's | |
317 | generally counter-productive to have multiple people working in secret | |
318 | on the same thing. | |
319 | ||
320 | At the same time, announce what you plan to do with the patch pumpkin, | |
321 | to allow folks a chance to object or suggest alternatives, or do it for | |
322 | you. Naturally, the patch pumpkin holder ought to incorporate various | |
323 | bug fixes and documentation improvements that are posted while he or | |
324 | she has the pumpkin, but there might also be larger issues at stake. | |
325 | ||
326 | One of the precepts of the subversion idea is that we shouldn't give | |
7b5757d1 AD |
327 | the patch pumpkin to anyone unless we have some idea what he or she |
328 | is going to do with it. | |
aa689395 | 329 | |
330 | =head2 refresh pod/perltoc.pod | |
331 | ||
332 | Presumably, you have done a full C<make> in your working source | |
333 | directory. Before you C<make spotless> (if you do), and if you have | |
334 | changed any documentation in any module or pod file, change to the | |
335 | F<pod> directory and run C<make toc>. | |
336 | ||
3e3baf6d TB |
337 | =head2 run installhtml to check the validity of the pod files |
338 | ||
aa689395 | 339 | =head2 update patchlevel.h |
340 | ||
341 | Don't be shy about using the subversion number, even for a relatively | |
342 | modest patch. We've never even come close to using all 99 subversions, | |
343 | and it's better to have a distinctive number for your patch. If you | |
344 | need feedback on your patch, go ahead and issue it and promise to | |
345 | incorporate that feedback quickly (e.g. within 1 week) and send out a | |
346 | second patch. | |
347 | ||
348 | =head2 run metaconfig | |
349 | ||
350 | If you need to make changes to Configure or config_h.SH, it may be best to | |
351 | change the appropriate metaconfig units instead, and regenerate Configure. | |
352 | ||
353 | metaconfig -m | |
354 | ||
20f245af AD |
355 | will regenerate Configure and config_h.SH. Much more information |
356 | on obtaining and running metaconfig is in the F<U/README> file | |
357 | that comes with Perl's metaconfig units. Perl's metaconfig units | |
358 | should be available on CPAN. A set of units that will work with | |
359 | perl5.005 is in the file F<mc_units-5.005_00-01.tar.gz> under | |
360 | http://www.perl.com/CPAN/authors/id/ANDYD/ . The mc_units tar file | |
361 | should be unpacked in your main perl source directory. Note: those | |
362 | units were for use with 5.005. There may have been changes since then. | |
d562869c | 363 | Check for later versions or contact perl5-porters@perl.org to obtain a |
20f245af | 364 | pointer to the current version. |
aa689395 | 365 | |
366 | Alternatively, do consider if the F<*ish.h> files might be a better | |
367 | place for your changes. | |
368 | ||
369 | =head2 MANIFEST | |
370 | ||
371 | Make sure the MANIFEST is up-to-date. You can use dist's B<manicheck> | |
372 | program for this. You can also use | |
373 | ||
3e3baf6d | 374 | perl -w -MExtUtils::Manifest=fullcheck -e fullcheck |
aa689395 | 375 | |
3e3baf6d TB |
376 | Both commands will also list extra files in the directory that are not |
377 | listed in MANIFEST. | |
aa689395 | 378 | |
bfb7748a | 379 | The MANIFEST is normally sorted. |
aa689395 | 380 | |
381 | If you are using metaconfig to regenerate Configure, then you should note | |
382 | that metaconfig actually uses MANIFEST.new, so you want to be sure | |
383 | MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new | |
384 | distinction particularly useful, but that's probably because I still haven't | |
385 | learned how to use the full suite of tools in the dist distribution. | |
386 | ||
387 | =head2 Check permissions | |
388 | ||
389 | All the tests in the t/ directory ought to be executable. The | |
390 | main makefile used to do a 'chmod t/*/*.t', but that resulted in | |
391 | a self-modifying distribution--something some users would strongly | |
d562869c AD |
392 | prefer to avoid. The F<t/TEST> script will check for this |
393 | and do the chmod if needed, but the tests still ought to be | |
394 | executable. | |
aa689395 | 395 | |
396 | In all, the following files should probably be executable: | |
397 | ||
398 | Configure | |
399 | configpm | |
32fcaa0b | 400 | configure.gnu |
aa689395 | 401 | embed.pl |
402 | installperl | |
403 | installman | |
404 | keywords.pl | |
aa689395 | 405 | myconfig |
406 | opcode.pl | |
407 | perly.fixer | |
408 | t/TEST | |
409 | t/*/*.t | |
410 | *.SH | |
411 | vms/ext/Stdio/test.pl | |
412 | vms/ext/filespec.t | |
aa689395 | 413 | x2p/*.SH |
414 | ||
415 | Other things ought to be readable, at least :-). | |
416 | ||
417 | Probably, the permissions for the files could be encoded in MANIFEST | |
418 | somehow, but I'm reluctant to change MANIFEST itself because that | |
419 | could break old scripts that use MANIFEST. | |
420 | ||
421 | I seem to recall that some SVR3 systems kept some sort of file that listed | |
422 | permissions for system files; something like that might be appropriate. | |
423 | ||
424 | =head2 Run Configure | |
425 | ||
426 | This will build a config.sh and config.h. You can skip this if you haven't | |
693762b4 | 427 | changed Configure or config_h.SH at all. I use the following command |
aa689395 | 428 | |
693762b4 AD |
429 | sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \ |
430 | -Dcf_by='yourname' \ | |
431 | -Dcf_email='yourname@yourhost.yourplace.com' \ | |
432 | -Dperladmin='yourname@yourhost.yourplace.com' \ | |
433 | -Dmydomain='.yourplace.com' \ | |
434 | -Dmyhostname='yourhost' \ | |
435 | -des | |
aa689395 | 436 | |
693762b4 | 437 | =head2 Update Porting/config.sh and Porting/config_H |
dfe9444c | 438 | |
693762b4 AD |
439 | [XXX |
440 | This section needs revision. We're currently working on easing | |
441 | the task of keeping the vms, win32, and plan9 config.sh info | |
442 | up-to-date. The plan is to use keep up-to-date 'canned' config.sh | |
443 | files in the appropriate subdirectories and then generate 'canned' | |
444 | config.h files for vms, win32, etc. from the generic config.sh file. | |
445 | This is to ease maintenance. When Configure gets updated, the parts | |
446 | sometimes get scrambled around, and the changes in config_H can | |
447 | sometimes be very hard to follow. config.sh, on the other hand, can | |
448 | safely be sorted, so it's easy to track (typically very small) changes | |
449 | to config.sh and then propoagate them to a canned 'config.h' by any | |
450 | number of means, including a perl script in win32/ or carrying | |
451 | config.sh and config_h.SH to a Unix system and running sh | |
452 | config_h.SH.) | |
453 | XXX] | |
454 | ||
455 | The Porting/config.sh and Porting/config_H files are provided to | |
456 | help those folks who can't run Configure. It is important to keep | |
457 | them up-to-date. If you have changed config_h.SH, those changes must | |
458 | be reflected in config_H as well. (The name config_H was chosen to | |
459 | distinguish the file from config.h even on case-insensitive file systems.) | |
460 | Simply edit the existing config_H file; keep the first few explanatory | |
461 | lines and then copy your new config.h below. | |
aa689395 | 462 | |
d562869c | 463 | It may also be necessary to update win32/config.?c, vms/config.vms and |
aa689395 | 464 | plan9/config.plan9, though you should be quite careful in doing so if |
465 | you are not familiar with those systems. You might want to issue your | |
466 | patch with a promise to quickly issue a follow-up that handles those | |
467 | directories. | |
468 | ||
469 | =head2 make run_byacc | |
470 | ||
471 | If you have byacc-1.8.2 (available from CPAN), and if there have been | |
472 | changes to F<perly.y>, you can regenerate the F<perly.c> file. The | |
473 | run_byacc makefile target does this by running byacc and then applying | |
474 | some patches so that byacc dynamically allocates space, rather than | |
475 | having fixed limits. This patch is handled by the F<perly.fixer> | |
476 | script. Depending on the nature of the changes to F<perly.y>, you may | |
477 | or may not have to hand-edit the patch to apply correctly. If you do, | |
478 | you should include the edited patch in the new distribution. If you | |
479 | have byacc-1.9, the patch won't apply cleanly. Changes to the printf | |
480 | output statements mean the patch won't apply cleanly. Long ago I | |
481 | started to fix F<perly.fixer> to detect this, but I never completed the | |
482 | task. | |
483 | ||
ebb99254 GS |
484 | If C<perly.c> changes, make sure you run C<perl vms/vms_yfix.pl> to |
485 | update the corresponding VMS files. See L<VMS-specific updates>. | |
486 | ||
aa689395 | 487 | Some additional notes from Larry on this: |
488 | ||
e262e9be | 489 | Don't forget to regenerate perly_c.diff. |
aa689395 | 490 | |
7b5757d1 | 491 | byacc -d perly.y |
aa689395 | 492 | mv y.tab.c perly.c |
e262e9be | 493 | patch perly.c <perly_c.diff |
aa689395 | 494 | # manually apply any failed hunks |
e262e9be | 495 | diff -c2 perly.c.orig perly.c >perly_c.diff |
aa689395 | 496 | |
497 | One chunk of lines that often fails begins with | |
498 | ||
499 | #line 29 "perly.y" | |
500 | ||
501 | and ends one line before | |
502 | ||
503 | #define YYERRCODE 256 | |
504 | ||
505 | This only happens when you add or remove a token type. I suppose this | |
506 | could be automated, but it doesn't happen very often nowadays. | |
507 | ||
508 | Larry | |
509 | ||
510 | =head2 make regen_headers | |
511 | ||
512 | The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically | |
513 | generated by perl scripts. Since the user isn't guaranteed to have a | |
514 | working perl, we can't require the user to generate them. Hence you have | |
515 | to, if you're making a distribution. | |
516 | ||
517 | I used to include rules like the following in the makefile: | |
518 | ||
519 | # The following three header files are generated automatically | |
520 | # The correct versions should be already supplied with the perl kit, | |
521 | # in case you don't have perl or 'sh' available. | |
522 | # The - is to ignore error return codes in case you have the source | |
523 | # installed read-only or you don't have perl yet. | |
524 | keywords.h: keywords.pl | |
525 | @echo "Don't worry if this fails." | |
526 | - perl keywords.pl | |
527 | ||
528 | ||
7b5757d1 | 529 | However, I got B<lots> of mail consisting of people worrying because the |
aa689395 | 530 | command failed. I eventually decided that I would save myself time |
531 | and effort by manually running C<make regen_headers> myself rather | |
532 | than answering all the questions and complaints about the failing | |
533 | command. | |
534 | ||
3e3baf6d | 535 | =head2 global.sym, interp.sym and perlio.sym |
aa689395 | 536 | |
537 | Make sure these files are up-to-date. Read the comments in these | |
538 | files and in perl_exp.SH to see what to do. | |
539 | ||
540 | =head2 Binary compatibility | |
541 | ||
542 | If you do change F<global.sym> or F<interp.sym>, think carefully about | |
543 | what you are doing. To the extent reasonable, we'd like to maintain | |
544 | souce and binary compatibility with older releases of perl. That way, | |
545 | extensions built under one version of perl will continue to work with | |
546 | new versions of perl. | |
547 | ||
548 | Of course, some incompatible changes may well be necessary. I'm just | |
549 | suggesting that we not make any such changes without thinking carefully | |
550 | about them first. If possible, we should provide | |
551 | backwards-compatibility stubs. There's a lot of XS code out there. | |
552 | Let's not force people to keep changing it. | |
553 | ||
554 | =head2 Changes | |
555 | ||
556 | Be sure to update the F<Changes> file. Try to include both an overall | |
557 | summary as well as detailed descriptions of the changes. Your | |
3e3baf6d | 558 | audience will include other developers and users, so describe |
aa689395 | 559 | user-visible changes (if any) in terms they will understand, not in |
560 | code like "initialize foo variable in bar function". | |
561 | ||
562 | There are differing opinions on whether the detailed descriptions | |
563 | ought to go in the Changes file or whether they ought to be available | |
564 | separately in the patch file (or both). There is no disagreement that | |
565 | detailed descriptions ought to be easily available somewhere. | |
566 | ||
2a26e2f1 DD |
567 | =head2 Todo |
568 | ||
569 | The F<Todo> file contains a roughly-catgorized unordered list of | |
570 | aspects of Perl that could use enhancement, features that could be | |
571 | added, areas that could be cleaned up, and so on. During your term as | |
572 | pumpkin-holder, you will probably address some of these issues, and | |
573 | perhaps identify others which, while you decide not to address them | |
574 | this time around, may be tackled in the future. Update the file | |
575 | reflect the situation as it stands when you hand over the pumpkin. | |
576 | ||
577 | You might like, early in your pumpkin-holding career, to see if you | |
578 | can find champions for partiticular issues on the to-do list: an issue | |
579 | owned is an issue more likely to be resolved. | |
580 | ||
c4f23d77 AD |
581 | There are also some more porting-specific L<Todo> items later in this |
582 | file. | |
583 | ||
aa689395 | 584 | =head2 OS/2-specific updates |
585 | ||
586 | In the os2 directory is F<diff.configure>, a set of OS/2-specific | |
587 | diffs against B<Configure>. If you make changes to Configure, you may | |
588 | want to consider regenerating this diff file to save trouble for the | |
589 | OS/2 maintainer. | |
590 | ||
7b5757d1 AD |
591 | You can also consider the OS/2 diffs as reminders of portability |
592 | things that need to be fixed in Configure. | |
593 | ||
aa689395 | 594 | =head2 VMS-specific updates |
595 | ||
ebb99254 GS |
596 | If you have changed F<perly.y> or F<perly.c>, then you most probably want |
597 | to update F<vms/perly_{h,c}.vms> by running C<perl vms/vms_yfix.pl>. | |
aa689395 | 598 | |
599 | The Perl version number appears in several places under F<vms>. | |
600 | It is courteous to update these versions. For example, if you are | |
601 | making 5.004_42, replace "5.00441" with "5.00442". | |
602 | ||
603 | =head2 Making the new distribution | |
604 | ||
605 | Suppose, for example, that you want to make version 5.004_08. Then you can | |
606 | do something like the following | |
607 | ||
608 | mkdir ../perl5.004_08 | |
609 | awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08 | |
610 | cd ../ | |
611 | tar cf perl5.004_08.tar perl5.004_08 | |
612 | gzip --best perl5.004_08.tar | |
613 | ||
3e3baf6d TB |
614 | These steps, with extra checks, are automated by the Porting/makerel |
615 | script. | |
616 | ||
aa689395 | 617 | =head2 Making a new patch |
618 | ||
619 | I find the F<makepatch> utility quite handy for making patches. | |
620 | You can obtain it from any CPAN archive under | |
3e3baf6d TB |
621 | http://www.perl.com/CPAN/authors/Johan_Vromans/ . There are a couple |
622 | of differences between my version and the standard one. I have mine do | |
623 | a | |
aa689395 | 624 | |
625 | # Print a reassuring "End of Patch" note so people won't | |
626 | # wonder if their mailer truncated patches. | |
627 | print "\n\nEnd of Patch.\n"; | |
628 | ||
3e3baf6d TB |
629 | at the end. That's because I used to get questions from people asking |
630 | if their mail was truncated. | |
631 | ||
632 | It also writes Index: lines which include the new directory prefix | |
633 | (change Index: print, approx line 294 or 310 depending on the version, | |
634 | to read: print PATCH ("Index: $newdir$new\n");). That helps patches | |
635 | work with more POSIX conformant patch programs. | |
aa689395 | 636 | |
637 | Here's how I generate a new patch. I'll use the hypothetical | |
638 | 5.004_07 to 5.004_08 patch as an example. | |
639 | ||
640 | # unpack perl5.004_07/ | |
641 | gzip -d -c perl5.004_07.tar.gz | tar -xof - | |
642 | # unpack perl5.004_08/ | |
643 | gzip -d -c perl5.004_08.tar.gz | tar -xof - | |
644 | makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat | |
645 | ||
646 | Makepatch will automatically generate appropriate B<rm> commands to remove | |
647 | deleted files. Unfortunately, it will not correctly set permissions | |
648 | for newly created files, so you may have to do so manually. For example, | |
649 | patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable, | |
650 | so at the top of the patch, I inserted the following lines: | |
651 | ||
652 | # Make a new test | |
653 | touch t/op/gv.t | |
654 | chmod +x t/opt/gv.t | |
655 | ||
656 | Now, of course, my patch is now wrong because makepatch didn't know I | |
657 | was going to do that command, and it patched against /dev/null. | |
658 | ||
659 | So, what I do is sort out all such shell commands that need to be in the | |
660 | patch (including possible mv-ing of files, if needed) and put that in the | |
661 | shell commands at the top of the patch. Next, I delete all the patch parts | |
662 | of perl5.004_08.pat, leaving just the shell commands. Then, I do the | |
663 | following: | |
664 | ||
7b5757d1 AD |
665 | cd perl5.004_07 |
666 | sh ../perl5.004_08.pat | |
aa689395 | 667 | cd .. |
7b5757d1 | 668 | makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat |
aa689395 | 669 | |
670 | (Note the append to preserve my shell commands.) | |
671 | Now, my patch will line up with what the end users are going to do. | |
672 | ||
673 | =head2 Testing your patch | |
674 | ||
675 | It seems obvious, but be sure to test your patch. That is, verify that | |
676 | it produces exactly the same thing as your full distribution. | |
677 | ||
7b5757d1 AD |
678 | rm -rf perl5.004_07 |
679 | gzip -d -c perl5.004_07.tar.gz | tar -xf - | |
680 | cd perl5.004_07 | |
681 | sh ../perl5.004_08.pat | |
682 | patch -p1 -N < ../perl5.004_08.pat | |
aa689395 | 683 | cd .. |
7b5757d1 | 684 | gdiff -r perl5.004_07 perl5.004_08 |
aa689395 | 685 | |
686 | where B<gdiff> is GNU diff. Other diff's may also do recursive checking. | |
687 | ||
688 | =head2 More testing | |
689 | ||
690 | Again, it's obvious, but you should test your new version as widely as you | |
691 | can. You can be sure you'll hear about it quickly if your version doesn't | |
692 | work on both ANSI and pre-ANSI compilers, and on common systems such as | |
693 | SunOS 4.1.[34], Solaris, and Linux. | |
694 | ||
695 | If your changes include conditional code, try to test the different | |
696 | branches as thoroughly as you can. For example, if your system | |
697 | supports dynamic loading, you can also test static loading with | |
698 | ||
699 | sh Configure -Uusedl | |
700 | ||
701 | You can also hand-tweak your config.h to try out different #ifdef | |
702 | branches. | |
703 | ||
d33b2eba | 704 | =head1 Running Purify |
f5a32c7f GS |
705 | |
706 | Purify is a commercial tool that is helpful in identifying memory | |
707 | overruns, wild pointers, memory leaks and other such badness. Perl | |
708 | must be compiled in a specific way for optimal testing with Purify. | |
709 | ||
710 | Use the following commands to test perl with Purify: | |
711 | ||
712 | sh Configure -des -Doptimize=-g -Uusemymalloc -Dusemultiplicity \ | |
713 | -Accflags=-DPURIFY | |
714 | setenv PURIFYOPTIONS "-chain-length=25" | |
715 | make all pureperl | |
716 | cd t | |
717 | ln -s ../pureperl perl | |
d33b2eba | 718 | setenv PERL_DESTRUCT_LEVEL 5 |
f5a32c7f GS |
719 | ./perl TEST |
720 | ||
721 | Disabling Perl's malloc allows Purify to monitor allocations and leaks | |
722 | more closely; using Perl's malloc will make Purify report most leaks | |
723 | in the "potential" leaks category. Enabling the multiplicity option | |
724 | allows perl to clean up thoroughly when the interpreter shuts down, which | |
725 | reduces the number of bogus leak reports from Purify. The -DPURIFY | |
726 | enables any Purify-specific debugging code in the sources. | |
727 | ||
728 | Purify outputs messages in "Viewer" windows by default. If you don't have | |
729 | a windowing environment or if you simply want the Purify output to | |
730 | unobtrusively go to a log file instead of to the interactive window, | |
731 | use the following options instead: | |
732 | ||
733 | setenv PURIFYOPTIONS "-chain-length=25 -windows=no -log-file=perl.log \ | |
734 | -append-logfile=yes" | |
735 | ||
736 | The only currently known leaks happen when there are compile-time errors | |
737 | within eval or require. (Fixing these is non-trivial, unfortunately, but | |
738 | they must be fixed eventually.) | |
739 | ||
aa689395 | 740 | =head1 Common Gotcha's |
741 | ||
742 | =over 4 | |
743 | ||
744 | =item #elif | |
745 | ||
746 | The '#elif' preprocessor directive is not understood on all systems. | |
747 | Specifically, I know that Pyramids don't understand it. Thus instead of the | |
748 | simple | |
749 | ||
750 | #if defined(I_FOO) | |
751 | # include <foo.h> | |
752 | #elif defined(I_BAR) | |
753 | # include <bar.h> | |
754 | #else | |
755 | # include <fubar.h> | |
756 | #endif | |
757 | ||
758 | You have to do the more Byzantine | |
759 | ||
760 | #if defined(I_FOO) | |
761 | # include <foo.h> | |
762 | #else | |
763 | # if defined(I_BAR) | |
764 | # include <bar.h> | |
765 | # else | |
766 | # include <fubar.h> | |
767 | # endif | |
768 | #endif | |
769 | ||
770 | Incidentally, whitespace between the leading '#' and the preprocessor | |
771 | command is not guaranteed, but is very portable and you may use it freely. | |
772 | I think it makes things a bit more readable, especially once things get | |
773 | rather deeply nested. I also think that things should almost never get | |
774 | too deeply nested, so it ought to be a moot point :-) | |
775 | ||
776 | =item Probably Prefer POSIX | |
777 | ||
778 | It's often the case that you'll need to choose whether to do | |
779 | something the BSD-ish way or the POSIX-ish way. It's usually not | |
780 | a big problem when the two systems use different names for similar | |
781 | functions, such as memcmp() and bcmp(). The perl.h header file | |
782 | handles these by appropriate #defines, selecting the POSIX mem*() | |
783 | functions if available, but falling back on the b*() functions, if | |
784 | need be. | |
785 | ||
786 | More serious is the case where some brilliant person decided to | |
787 | use the same function name but give it a different meaning or | |
788 | calling sequence :-). getpgrp() and setpgrp() come to mind. | |
789 | These are a real problem on systems that aim for conformance to | |
790 | one standard (e.g. POSIX), but still try to support the other way | |
791 | of doing things (e.g. BSD). My general advice (still not really | |
792 | implemented in the source) is to do something like the following. | |
793 | Suppose there are two alternative versions, fooPOSIX() and | |
794 | fooBSD(). | |
795 | ||
796 | #ifdef HAS_FOOPOSIX | |
797 | /* use fooPOSIX(); */ | |
798 | #else | |
799 | # ifdef HAS_FOOBSD | |
800 | /* try to emulate fooPOSIX() with fooBSD(); | |
801 | perhaps with the following: */ | |
802 | # define fooPOSIX fooBSD | |
803 | # else | |
804 | # /* Uh, oh. We have to supply our own. */ | |
805 | # define fooPOSIX Perl_fooPOSIX | |
806 | # endif | |
807 | #endif | |
808 | ||
809 | =item Think positively | |
810 | ||
811 | If you need to add an #ifdef test, it is usually easier to follow if you | |
812 | think positively, e.g. | |
813 | ||
814 | #ifdef HAS_NEATO_FEATURE | |
815 | /* use neato feature */ | |
816 | #else | |
817 | /* use some fallback mechanism */ | |
818 | #endif | |
819 | ||
820 | rather than the more impenetrable | |
821 | ||
822 | #ifndef MISSING_NEATO_FEATURE | |
823 | /* Not missing it, so we must have it, so use it */ | |
824 | #else | |
825 | /* Are missing it, so fall back on something else. */ | |
826 | #endif | |
827 | ||
828 | Of course for this toy example, there's not much difference. But when | |
829 | the #ifdef's start spanning a couple of screen fulls, and the #else's | |
830 | are marked something like | |
831 | ||
832 | #else /* !MISSING_NEATO_FEATURE */ | |
833 | ||
834 | I find it easy to get lost. | |
835 | ||
836 | =item Providing Missing Functions -- Problem | |
837 | ||
838 | Not all systems have all the neat functions you might want or need, so | |
839 | you might decide to be helpful and provide an emulation. This is | |
840 | sound in theory and very kind of you, but please be careful about what | |
841 | you name the function. Let me use the C<pause()> function as an | |
842 | illustration. | |
843 | ||
844 | Perl5.003 has the following in F<perl.h> | |
845 | ||
846 | #ifndef HAS_PAUSE | |
847 | #define pause() sleep((32767<<16)+32767) | |
848 | #endif | |
849 | ||
850 | Configure sets HAS_PAUSE if the system has the pause() function, so | |
851 | this #define only kicks in if the pause() function is missing. | |
852 | Nice idea, right? | |
853 | ||
854 | Unfortunately, some systems apparently have a prototype for pause() | |
855 | in F<unistd.h>, but don't actually have the function in the library. | |
856 | (Or maybe they do have it in a library we're not using.) | |
857 | ||
858 | Thus, the compiler sees something like | |
859 | ||
860 | extern int pause(void); | |
861 | /* . . . */ | |
862 | #define pause() sleep((32767<<16)+32767) | |
863 | ||
864 | and dies with an error message. (Some compilers don't mind this; | |
865 | others apparently do.) | |
866 | ||
867 | To work around this, 5.003_03 and later have the following in perl.h: | |
868 | ||
869 | /* Some unistd.h's give a prototype for pause() even though | |
870 | HAS_PAUSE ends up undefined. This causes the #define | |
871 | below to be rejected by the compiler. Sigh. | |
872 | */ | |
873 | #ifdef HAS_PAUSE | |
874 | # define Pause pause | |
875 | #else | |
876 | # define Pause() sleep((32767<<16)+32767) | |
877 | #endif | |
878 | ||
879 | This works. | |
880 | ||
881 | The curious reader may wonder why I didn't do the following in | |
882 | F<util.c> instead: | |
883 | ||
884 | #ifndef HAS_PAUSE | |
885 | void pause() | |
886 | { | |
887 | sleep((32767<<16)+32767); | |
888 | } | |
889 | #endif | |
890 | ||
891 | That is, since the function is missing, just provide it. | |
892 | Then things would probably be been alright, it would seem. | |
893 | ||
894 | Well, almost. It could be made to work. The problem arises from the | |
895 | conflicting needs of dynamic loading and namespace protection. | |
896 | ||
897 | For dynamic loading to work on AIX (and VMS) we need to provide a list | |
898 | of symbols to be exported. This is done by the script F<perl_exp.SH>, | |
899 | which reads F<global.sym> and F<interp.sym>. Thus, the C<pause> | |
900 | symbol would have to be added to F<global.sym> So far, so good. | |
901 | ||
902 | On the other hand, one of the goals of Perl5 is to make it easy to | |
903 | either extend or embed perl and link it with other libraries. This | |
904 | means we have to be careful to keep the visible namespace "clean". | |
905 | That is, we don't want perl's global variables to conflict with | |
906 | those in the other application library. Although this work is still | |
907 | in progress, the way it is currently done is via the F<embed.h> file. | |
908 | This file is built from the F<global.sym> and F<interp.sym> files, | |
909 | since those files already list the globally visible symbols. If we | |
910 | had added C<pause> to global.sym, then F<embed.h> would contain the | |
911 | line | |
912 | ||
913 | #define pause Perl_pause | |
914 | ||
915 | and calls to C<pause> in the perl sources would now point to | |
916 | C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable, | |
917 | it will go looking for C<perl_pause>, which probably won't exist in any | |
918 | of the standard libraries. Thus the build of perl will fail. | |
919 | ||
920 | Those systems where C<HAS_PAUSE> is not defined would be ok, however, | |
921 | since they would get a C<Perl_pause> function in util.c. The rest of | |
922 | the world would be in trouble. | |
923 | ||
924 | And yes, this scenario has happened. On SCO, the function C<chsize> | |
925 | is available. (I think it's in F<-lx>, the Xenix compatibility | |
926 | library.) Since the perl4 days (and possibly before), Perl has | |
927 | included a C<chsize> function that gets called something akin to | |
928 | ||
929 | #ifndef HAS_CHSIZE | |
930 | I32 chsize(fd, length) | |
931 | /* . . . */ | |
932 | #endif | |
933 | ||
934 | When 5.003 added | |
935 | ||
936 | #define chsize Perl_chsize | |
937 | ||
938 | to F<embed.h>, the compile started failing on SCO systems. | |
939 | ||
940 | The "fix" is to give the function a different name. The one | |
941 | implemented in 5.003_05 isn't optimal, but here's what was done: | |
942 | ||
943 | #ifdef HAS_CHSIZE | |
944 | # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */ | |
945 | # undef my_chsize | |
946 | # endif | |
947 | # define my_chsize chsize | |
948 | #endif | |
949 | ||
950 | My explanatory comment in patch 5.003_05 said: | |
951 | ||
952 | Undef and then re-define my_chsize from Perl_my_chsize to | |
953 | just plain chsize if this system HAS_CHSIZE. This probably only | |
954 | applies to SCO. This shows the perils of having internal | |
955 | functions with the same name as external library functions :-). | |
956 | ||
957 | Now, we can safely put C<my_chsize> in F<global.sym>, export it, and | |
958 | hide it with F<embed.h>. | |
959 | ||
960 | To be consistent with what I did for C<pause>, I probably should have | |
961 | called the new function C<Chsize>, rather than C<my_chsize>. | |
962 | However, the perl sources are quite inconsistent on this (Consider | |
963 | New, Mymalloc, and Myremalloc, to name just a few.) | |
964 | ||
965 | There is a problem with this fix, however, in that C<Perl_chsize> | |
966 | was available as a F<libperl.a> library function in 5.003, but it | |
967 | isn't available any more (as of 5.003_07). This means that we've | |
968 | broken binary compatibility. This is not good. | |
969 | ||
970 | =item Providing missing functions -- some ideas | |
971 | ||
972 | We currently don't have a standard way of handling such missing | |
973 | function names. Right now, I'm effectively thinking aloud about a | |
974 | solution. Some day, I'll try to formally propose a solution. | |
975 | ||
976 | Part of the problem is that we want to have some functions listed as | |
977 | exported but not have their names mangled by embed.h or possibly | |
978 | conflict with names in standard system headers. We actually already | |
979 | have such a list at the end of F<perl_exp.SH> (though that list is | |
980 | out-of-date): | |
981 | ||
982 | # extra globals not included above. | |
983 | cat <<END >> perl.exp | |
984 | perl_init_ext | |
985 | perl_init_fold | |
986 | perl_init_i18nl14n | |
987 | perl_alloc | |
988 | perl_construct | |
989 | perl_destruct | |
990 | perl_free | |
991 | perl_parse | |
992 | perl_run | |
993 | perl_get_sv | |
994 | perl_get_av | |
995 | perl_get_hv | |
996 | perl_get_cv | |
997 | perl_call_argv | |
998 | perl_call_pv | |
999 | perl_call_method | |
1000 | perl_call_sv | |
1001 | perl_requirepv | |
1002 | safecalloc | |
1003 | safemalloc | |
1004 | saferealloc | |
1005 | safefree | |
1006 | ||
1007 | This still needs much thought, but I'm inclined to think that one | |
1008 | possible solution is to prefix all such functions with C<perl_> in the | |
1009 | source and list them along with the other C<perl_*> functions in | |
1010 | F<perl_exp.SH>. | |
1011 | ||
1012 | Thus, for C<chsize>, we'd do something like the following: | |
1013 | ||
1014 | /* in perl.h */ | |
1015 | #ifdef HAS_CHSIZE | |
1016 | # define perl_chsize chsize | |
1017 | #endif | |
1018 | ||
1019 | then in some file (e.g. F<util.c> or F<doio.c>) do | |
1020 | ||
1021 | #ifndef HAS_CHSIZE | |
1022 | I32 perl_chsize(fd, length) | |
1023 | /* implement the function here . . . */ | |
1024 | #endif | |
1025 | ||
1026 | Alternatively, we could just always use C<chsize> everywhere and move | |
1027 | C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would | |
1028 | probably be fine as long as our C<chsize> function agreed with all the | |
1029 | C<chsize> function prototypes in the various systems we'll be using. | |
1030 | As long as the prototypes in actual use don't vary that much, this is | |
1031 | probably a good alternative. (As a counter-example, note how Configure | |
1032 | and perl have to go through hoops to find and use get Malloc_t and | |
1033 | Free_t for C<malloc> and C<free>.) | |
1034 | ||
1035 | At the moment, this latter option is what I tend to prefer. | |
1036 | ||
1037 | =item All the world's a VAX | |
1038 | ||
1039 | Sorry, showing my age:-). Still, all the world is not BSD 4.[34], | |
1040 | SVR4, or POSIX. Be aware that SVR3-derived systems are still quite | |
1041 | common (do you have any idea how many systems run SCO?) If you don't | |
1042 | have a bunch of v7 manuals handy, the metaconfig units (by default | |
1043 | installed in F</usr/local/lib/dist/U>) are a good resource to look at | |
1044 | for portability. | |
1045 | ||
1046 | =back | |
1047 | ||
1048 | =head1 Miscellaneous Topics | |
1049 | ||
1050 | =head2 Autoconf | |
1051 | ||
1052 | Why does perl use a metaconfig-generated Configure script instead of an | |
1053 | autoconf-generated configure script? | |
1054 | ||
1055 | Metaconfig and autoconf are two tools with very similar purposes. | |
1056 | Metaconfig is actually the older of the two, and was originally written | |
1057 | by Larry Wall, while autoconf is probably now used in a wider variety of | |
1058 | packages. The autoconf info file discusses the history of autoconf and | |
1059 | how it came to be. The curious reader is referred there for further | |
1060 | information. | |
1061 | ||
1062 | Overall, both tools are quite good, I think, and the choice of which one | |
1063 | to use could be argued either way. In March, 1994, when I was just | |
1064 | starting to work on Configure support for Perl5, I considered both | |
1065 | autoconf and metaconfig, and eventually decided to use metaconfig for the | |
1066 | following reasons: | |
1067 | ||
1068 | =over 4 | |
1069 | ||
1070 | =item Compatibility with Perl4 | |
1071 | ||
1072 | Perl4 used metaconfig, so many of the #ifdef's were already set up for | |
1073 | metaconfig. Of course metaconfig had evolved some since Perl4's days, | |
1074 | but not so much that it posed any serious problems. | |
1075 | ||
1076 | =item Metaconfig worked for me | |
1077 | ||
1078 | My system at the time was Interactive 2.2, a SVR3.2/386 derivative that | |
1079 | also had some POSIX support. Metaconfig-generated Configure scripts | |
1080 | worked fine for me on that system. On the other hand, autoconf-generated | |
1081 | scripts usually didn't. (They did come quite close, though, in some | |
1082 | cases.) At the time, I actually fetched a large number of GNU packages | |
1083 | and checked. Not a single one configured and compiled correctly | |
1084 | out-of-the-box with the system's cc compiler. | |
1085 | ||
1086 | =item Configure can be interactive | |
1087 | ||
1088 | With both autoconf and metaconfig, if the script works, everything is | |
1089 | fine. However, one of my main problems with autoconf-generated scripts | |
1090 | was that if it guessed wrong about something, it could be B<very> hard to | |
1091 | go back and fix it. For example, autoconf always insisted on passing the | |
1092 | -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I | |
1093 | wanted or needed for that package. There was no way short of editing the | |
1094 | configure script to turn this off. You couldn't just edit the resulting | |
1095 | Makefile at the end because the -Xp flag influenced a number of other | |
1096 | configure tests. | |
1097 | ||
1098 | Metaconfig's Configure scripts, on the other hand, can be interactive. | |
1099 | Thus if Configure is guessing things incorrectly, you can go back and fix | |
1100 | them. This isn't as important now as it was when we were actively | |
1101 | developing Configure support for new features such as dynamic loading, | |
1102 | but it's still useful occasionally. | |
1103 | ||
1104 | =item GPL | |
1105 | ||
1106 | At the time, autoconf-generated scripts were covered under the GNU Public | |
1107 | License, and hence weren't suitable for inclusion with Perl, which has a | |
1108 | different licensing policy. (Autoconf's licensing has since changed.) | |
1109 | ||
1110 | =item Modularity | |
1111 | ||
1112 | Metaconfig builds up Configure from a collection of discrete pieces | |
1113 | called "units". You can override the standard behavior by supplying your | |
1114 | own unit. With autoconf, you have to patch the standard files instead. | |
1115 | I find the metaconfig "unit" method easier to work with. Others | |
1116 | may find metaconfig's units clumsy to work with. | |
1117 | ||
1118 | =back | |
1119 | ||
aa689395 | 1120 | =head2 Why isn't there a directory to override Perl's library? |
1121 | ||
1122 | Mainly because no one's gotten around to making one. Note that | |
1123 | "making one" involves changing perl.c, Configure, config_h.SH (and | |
1124 | associated files, see above), and I<documenting> it all in the | |
1125 | INSTALL file. | |
1126 | ||
1127 | Apparently, most folks who want to override one of the standard library | |
1128 | files simply do it by overwriting the standard library files. | |
1129 | ||
1130 | =head2 APPLLIB | |
1131 | ||
1132 | In the perl.c sources, you'll find an undocumented APPLLIB_EXP | |
1133 | variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are | |
1134 | documented in config_h.SH). Here's what APPLLIB_EXP is for, from | |
1135 | a mail message from Larry: | |
1136 | ||
1137 | The main intent of APPLLIB_EXP is for folks who want to send out a | |
1138 | version of Perl embedded in their product. They would set the symbol | |
1139 | to be the name of the library containing the files needed to run or to | |
1140 | support their particular application. This works at the "override" | |
1141 | level to make sure they get their own versions of any library code that | |
1142 | they absolutely must have configuration control over. | |
1143 | ||
1144 | As such, I don't see any conflict with a sysadmin using it for a | |
1145 | override-ish sort of thing, when installing a generic Perl. It should | |
1146 | probably have been named something to do with overriding though. Since | |
1147 | it's undocumented we could still change it... :-) | |
1148 | ||
1149 | Given that it's already there, you can use it to override | |
1150 | distribution modules. If you do | |
1151 | ||
1152 | sh Configure -Dccflags='-DAPPLLIB_EXP=/my/override' | |
1153 | ||
1154 | then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB. | |
1155 | ||
c4f23d77 AD |
1156 | =head2 Shared libperl.so location |
1157 | ||
1158 | Why isn't the shared libperl.so installed in /usr/lib/ along | |
1159 | with "all the other" shared libraries? Instead, it is installed | |
1160 | in $archlib, which is typically something like | |
1161 | ||
1162 | /usr/local/lib/perl5/archname/5.00404 | |
1163 | ||
1164 | and is architecture- and version-specific. | |
1165 | ||
1166 | The basic reason why a shared libperl.so gets put in $archlib is so that | |
1167 | you can have more than one version of perl on the system at the same time, | |
1168 | and have each refer to its own libperl.so. | |
1169 | ||
1170 | Three examples might help. All of these work now; none would work if you | |
1171 | put libperl.so in /usr/lib. | |
1172 | ||
1173 | =over | |
1174 | ||
1175 | =item 1. | |
1176 | ||
1177 | Suppose you want to have both threaded and non-threaded perl versions | |
1178 | around. Configure will name both perl libraries "libperl.so" (so that | |
1179 | you can link to them with -lperl). The perl binaries tell them apart | |
1180 | by having looking in the appropriate $archlib directories. | |
1181 | ||
1182 | =item 2. | |
1183 | ||
1184 | Suppose you have perl5.004_04 installed and you want to try to compile | |
1185 | it again, perhaps with different options or after applying a patch. | |
1186 | If you already have libperl.so installed in /usr/lib/, then it may be | |
1187 | either difficult or impossible to get ld.so to find the new libperl.so | |
1188 | that you're trying to build. If, instead, libperl.so is tucked away in | |
1189 | $archlib, then you can always just change $archlib in the current perl | |
1190 | you're trying to build so that ld.so won't find your old libperl.so. | |
1191 | (The INSTALL file suggests you do this when building a debugging perl.) | |
1192 | ||
1193 | =item 3. | |
1194 | ||
1195 | The shared perl library is not a "well-behaved" shared library with | |
1196 | proper major and minor version numbers, so you can't necessarily | |
1197 | have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose | |
1198 | perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05 | |
1199 | were to install /usr/lib/libperl.so.4.5. Now, when you try to run | |
1200 | perl5.004_04, ld.so might try to load libperl.so.4.5, since it has | |
1201 | the right "major version" number. If this works at all, it almost | |
1202 | certainly defeats the reason for keeping perl5.004_04 around. Worse, | |
1203 | with development subversions, you certaily can't guarantee that | |
1204 | libperl.so.4.4 and libperl.so.4.55 will be compatible. | |
1205 | ||
1206 | Anyway, all this leads to quite obscure failures that are sure to drive | |
1207 | casual users crazy. Even experienced users will get confused :-). Upon | |
1208 | reflection, I'd say leave libperl.so in $archlib. | |
1209 | ||
1210 | =back | |
1211 | ||
aa689395 | 1212 | =head1 Upload Your Work to CPAN |
1213 | ||
1214 | You can upload your work to CPAN if you have a CPAN id. Check out | |
1215 | http://www.perl.com/CPAN/modules/04pause.html for information on | |
1216 | _PAUSE_, the Perl Author's Upload Server. | |
1217 | ||
1218 | I typically upload both the patch file, e.g. F<perl5.004_08.pat.gz> | |
1219 | and the full tar file, e.g. F<perl5.004_08.tar.gz>. | |
1220 | ||
1221 | If you want your patch to appear in the F<src/5.0/unsupported> | |
1222 | directory on CPAN, send e-mail to the CPAN master librarian. (Check | |
7b5757d1 | 1223 | out http://www.perl.com/CPAN/CPAN.html ). |
aa689395 | 1224 | |
1225 | =head1 Help Save the World | |
1226 | ||
1227 | You should definitely announce your patch on the perl5-porters list. | |
1228 | You should also consider announcing your patch on | |
1229 | comp.lang.perl.announce, though you should make it quite clear that a | |
1230 | subversion is not a production release, and be prepared to deal with | |
1231 | people who will not read your disclaimer. | |
1232 | ||
1233 | =head1 Todo | |
1234 | ||
1235 | Here, in no particular order, are some Configure and build-related | |
1236 | items that merit consideration. This list isn't exhaustive, it's just | |
1237 | what I came up with off the top of my head. | |
1238 | ||
1239 | =head2 Good ideas waiting for round tuits | |
1240 | ||
1241 | =over 4 | |
1242 | ||
c4f23d77 | 1243 | =item Configure -Dsrc=/blah/blah |
aa689395 | 1244 | |
1245 | We should be able to emulate B<configure --srcdir>. Tom Tromey | |
1246 | tromey@creche.cygnus.com has submitted some patches to | |
c4f23d77 AD |
1247 | the dist-users mailing list along these lines. They have been folded |
1248 | back into the main distribution, but various parts of the perl | |
1249 | Configure/build/install process still assume src='.'. | |
aa689395 | 1250 | |
1251 | =item Hint file fixes | |
1252 | ||
1253 | Various hint files work around Configure problems. We ought to fix | |
1254 | Configure so that most of them aren't needed. | |
1255 | ||
1256 | =item Hint file information | |
1257 | ||
1258 | Some of the hint file information (particularly dynamic loading stuff) | |
1259 | ought to be fed back into the main metaconfig distribution. | |
1260 | ||
1261 | =back | |
1262 | ||
1263 | =head2 Probably good ideas waiting for round tuits | |
1264 | ||
1265 | =over 4 | |
1266 | ||
1267 | =item GNU configure --options | |
1268 | ||
1269 | I've received sensible suggestions for --exec_prefix and other | |
1270 | GNU configure --options. It's not always obvious exactly what is | |
1271 | intended, but this merits investigation. | |
1272 | ||
1273 | =item make clean | |
1274 | ||
1275 | Currently, B<make clean> isn't all that useful, though | |
1276 | B<make realclean> and B<make distclean> are. This needs a bit of | |
1277 | thought and documentation before it gets cleaned up. | |
1278 | ||
1279 | =item Try gcc if cc fails | |
1280 | ||
1281 | Currently, we just give up. | |
1282 | ||
1283 | =item bypassing safe*alloc wrappers | |
1284 | ||
1285 | On some systems, it may be safe to call the system malloc directly | |
1286 | without going through the util.c safe* layers. (Such systems would | |
1287 | accept free(0), for example.) This might be a time-saver for systems | |
1288 | that already have a good malloc. (Recent Linux libc's apparently have | |
1289 | a nice malloc that is well-tuned for the system.) | |
1290 | ||
1291 | =back | |
1292 | ||
1293 | =head2 Vague possibilities | |
1294 | ||
1295 | =over 4 | |
1296 | ||
aa689395 | 1297 | =item MacPerl |
1298 | ||
3e3baf6d | 1299 | Get some of the Macintosh stuff folded back into the main distribution. |
aa689395 | 1300 | |
1301 | =item gconvert replacement | |
1302 | ||
1303 | Maybe include a replacement function that doesn't lose data in rare | |
1304 | cases of coercion between string and numerical values. | |
1305 | ||
aa689395 | 1306 | =item Improve makedepend |
1307 | ||
1308 | The current makedepend process is clunky and annoyingly slow, but it | |
1309 | works for most folks. Alas, it assumes that there is a filename | |
1310 | $firstmakefile that the B<make> command will try to use before it uses | |
1311 | F<Makefile>. Such may not be the case for all B<make> commands, | |
1312 | particularly those on non-Unix systems. | |
1313 | ||
1314 | Probably some variant of the BSD F<.depend> file will be useful. | |
1315 | We ought to check how other packages do this, if they do it at all. | |
1316 | We could probably pre-generate the dependencies (with the exception of | |
1317 | malloc.o, which could probably be determined at F<Makefile.SH> | |
1318 | extraction time. | |
1319 | ||
1320 | =item GNU Makefile standard targets | |
1321 | ||
1322 | GNU software generally has standardized Makefile targets. Unless we | |
1323 | have good reason to do otherwise, I see no reason not to support them. | |
1324 | ||
1325 | =item File locking | |
1326 | ||
1327 | Somehow, straighten out, document, and implement lockf(), flock(), | |
1328 | and/or fcntl() file locking. It's a mess. | |
1329 | ||
1330 | =back | |
1331 | ||
fb73857a | 1332 | =head1 AUTHORS |
aa689395 | 1333 | |
fb73857a | 1334 | Original author: Andy Dougherty doughera@lafcol.lafayette.edu . |
1335 | Additions by Chip Salzenberg chip@perl.com and | |
1336 | Tim Bunce Tim.Bunce@ig.co.uk . | |
aa689395 | 1337 | |
1338 | All opinions expressed herein are those of the authorZ<>(s). | |
1339 | ||
1340 | =head1 LAST MODIFIED | |
1341 | ||
ff935051 | 1342 | $Id: pumpkin.pod,v 1.23 2000/01/13 19:45:13 doughera Released $ |