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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 | |
11 | This document attempts to begin to describe some of the |
12 | considerations involved in patching and maintaining perl. |
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 |
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27 | http://www.perl.com/CPAN/README.html , which automatically points you to a |
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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 | |
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44 | Archives of the list are held at: |
45 | |
46 | http://www.rosat.mpe-garching.mpg.de/mailing-lists/perl-porters/ |
47 | |
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48 | =head1 How are Perl Releases Numbered? |
49 | |
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50 | Perl version numbers are floating point numbers, such as 5.004. |
51 | (Observations about the imprecision of floating point numbers for |
52 | representing reality probably have more relevance than you might |
53 | imagine :-) The major version number is 5 and the '004' is the |
54 | patchlevel. (Questions such as whether or not '004' is really a minor |
55 | version number can safely be ignored.:) |
56 | |
57 | The version number is available as the magic variable $], |
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58 | and can be used in comparisons, e.g. |
59 | |
60 | print "You've got an old perl\n" if $] < 5.002; |
61 | |
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62 | You can also require particular version (or later) with |
63 | |
64 | use 5.002; |
65 | |
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66 | At some point in the future, we may need to decide what to call the |
67 | next big revision. In the .package file used by metaconfig to |
68 | generate Configure, there are two variables that might be relevant: |
69 | $baserev=5.0 and $package=perl5. At various times, I have suggested |
70 | we might change them to $baserev=5.1 and $package=perl5.1 if want |
71 | to signify a fairly major update. Or, we might want to jump to perl6. |
72 | Let's worry about that problem when we get there. |
73 | |
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74 | =head2 Subversions |
75 | |
76 | In addition, there may be "developer" sub-versions available. These |
77 | are not official releases. They may contain unstable experimental |
78 | features, and are subject to rapid change. Such developer |
79 | sub-versions are numbered with sub-version numbers. For example, |
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80 | version 5.003_04 is the 4'th developer version built on top of |
81 | 5.003. It might include the _01, _02, and _03 changes, but it |
82 | also might not. Sub-versions are allowed to be subversive. (But see |
83 | the next section for recent changes.) |
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84 | |
85 | These sub-versions can also be used as floating point numbers, so |
86 | you can do things such as |
87 | |
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88 | print "You've got an unstable perl\n" if $] == 5.00303; |
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89 | |
90 | You can also require particular version (or later) with |
91 | |
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92 | use 5.003_03; # the "_" is optional |
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93 | |
94 | Sub-versions produced by the members of perl5-porters are usually |
95 | available on CPAN in the F<src/5.0/unsupported> directory. |
96 | |
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97 | =head2 Maintenance and Development Subversions |
98 | |
99 | As an experiment, starting with version 5.004, subversions _01 through |
100 | _49 will be reserved for bug-fix maintenance releases, and subversions |
101 | _50 through _99 will be available for unstable development versions. |
102 | |
103 | The separate bug-fix track is being established to allow us an easy |
104 | way to distribute important bug fixes without waiting for the |
105 | developers to untangle all the other problems in the current |
106 | developer's release. |
107 | |
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108 | Trial releases of bug-fix maintenance releases are announced on |
109 | perl5-porters. Trial releases use the new subversion number (to avoid |
110 | testers installing it over the previous release) and include a 'local |
111 | patch' entry in patchlevel.h. |
112 | |
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113 | Watch for announcements of maintenance subversions in |
114 | comp.lang.perl.announce. |
115 | |
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116 | =head2 Why such a complicated scheme? |
117 | |
118 | Two reasons, really. At least. |
119 | |
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120 | First, we need some way to identify and release collections of patches |
121 | that are known to have new features that need testing and exploration. The |
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122 | subversion scheme does that nicely while fitting into the |
123 | C<use 5.004;> mold. |
124 | |
125 | Second, since most of the folks who help maintain perl do so on a |
126 | free-time voluntary basis, perl development does not proceed at a |
127 | precise pace, though it always seems to be moving ahead quickly. |
128 | We needed some way to pass around the "patch pumpkin" to allow |
129 | different people chances to work on different aspects of the |
130 | distribution without getting in each other's way. It wouldn't be |
131 | constructive to have multiple people working on incompatible |
132 | implementations of the same idea. Instead what was needed was |
133 | some kind of "baton" or "token" to pass around so everyone knew |
134 | whose turn was next. |
135 | |
136 | =head2 Why is it called the patch pumpkin? |
137 | |
138 | Chip Salzenberg gets credit for that, with a nod to his cow orker, |
139 | David Croy. We had passed around various names (baton, token, hot |
140 | potato) but none caught on. Then, Chip asked: |
141 | |
142 | [begin quote] |
143 | |
144 | Who has the patch pumpkin? |
145 | |
146 | To explain: David Croy once told me once that at a previous job, |
147 | there was one tape drive and multiple systems that used it for backups. |
148 | But instead of some high-tech exclusion software, they used a low-tech |
149 | method to prevent multiple simultaneous backups: a stuffed pumpkin. |
150 | No one was allowed to make backups unless they had the "backup pumpkin". |
151 | |
152 | [end quote] |
153 | |
154 | The name has stuck. |
155 | |
156 | =head1 Philosophical Issues in Patching Perl |
157 | |
158 | There are no absolute rules, but there are some general guidelines I |
159 | have tried to follow as I apply patches to the perl sources. |
160 | (This section is still under construction.) |
161 | |
162 | =head2 Solve problems as generally as possible |
163 | |
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164 | Never implement a specific restricted solution to a problem when you |
165 | can solve the same problem in a more general, flexible way. |
166 | |
167 | For example, for dynamic loading to work on some SVR4 systems, we had |
168 | to build a shared libperl.so library. In order to build "FAT" binaries |
169 | on NeXT 4.0 systems, we had to build a special libperl library. Rather |
170 | than continuing to build a contorted nest of special cases, I |
171 | generalized the process of building libperl so that NeXT and SVR4 users |
172 | could still get their work done, but others could build a shared |
173 | libperl if they wanted to as well. |
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174 | |
175 | =head2 Seek consensus on major changes |
176 | |
177 | If you are making big changes, don't do it in secret. Discuss the |
178 | ideas in advance on perl5-porters. |
179 | |
180 | =head2 Keep the documentation up-to-date |
181 | |
182 | If your changes may affect how users use perl, then check to be sure |
183 | that the documentation is in sync with your changes. Be sure to |
184 | check all the files F<pod/*.pod> and also the F<INSTALL> document. |
185 | |
186 | Consider writing the appropriate documentation first and then |
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187 | implementing your change to correspond to the documentation. |
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188 | |
189 | =head2 Avoid machine-specific #ifdef's |
190 | |
191 | To the extent reasonable, try to avoid machine-specific #ifdef's in |
192 | the sources. Instead, use feature-specific #ifdef's. The reason is |
193 | that the machine-specific #ifdef's may not be valid across major |
194 | releases of the operating system. Further, the feature-specific tests |
195 | may help out folks on another platform who have the same problem. |
196 | |
197 | =head2 Allow for lots of testing |
198 | |
199 | We should never release a main version without testing it as a |
200 | subversion first. |
201 | |
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202 | =head2 Test popular applications and modules. |
203 | |
204 | We should never release a main version without testing whether or not |
205 | it breaks various popular modules and applications. A partial list of |
206 | such things would include majordomo, metaconfig, apache, Tk, CGI, |
207 | libnet, and libwww, to name just a few. Of course it's quite possible |
208 | that some of those things will be just plain broken and need to be fixed, |
209 | but, in general, we ought to try to avoid breaking widely-installed |
210 | things. |
211 | |
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212 | =head2 Automate generation of derivative files |
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213 | |
214 | The F<embed.h>, F<keywords.h>, F<opcode.h>, and F<perltoc.pod> files |
215 | are all automatically generated by perl scripts. In general, don't |
216 | patch these directly; patch the data files instead. |
217 | |
218 | F<Configure> and F<config_h.SH> are also automatically generated by |
219 | B<metaconfig>. In general, you should patch the metaconfig units |
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220 | instead of patching these files directly. However, very minor changes to |
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221 | F<Configure> may be made in between major sync-ups with the metaconfig |
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222 | units, which tends to be complicated operations. But be careful, this |
223 | can quickly spiral out of control. Running metaconfig is not really |
224 | hard. |
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225 | |
226 | =head1 How to Make a Distribution |
227 | |
228 | There really ought to be a 'make dist' target, but there isn't. |
229 | The 'dist' suite of tools also contains a number of tools that I haven't |
230 | learned how to use yet. Some of them may make this all a bit easier. |
231 | |
232 | Here are the steps I go through to prepare a patch & distribution. |
233 | |
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234 | Lots of it could doubtless be automated but isn't. The Porting/makerel |
235 | (make release) perl script does now help automate some parts of it. |
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236 | |
237 | =head2 Announce your intentions |
238 | |
239 | First, you should volunteer out loud to take the patch pumpkin. It's |
240 | generally counter-productive to have multiple people working in secret |
241 | on the same thing. |
242 | |
243 | At the same time, announce what you plan to do with the patch pumpkin, |
244 | to allow folks a chance to object or suggest alternatives, or do it for |
245 | you. Naturally, the patch pumpkin holder ought to incorporate various |
246 | bug fixes and documentation improvements that are posted while he or |
247 | she has the pumpkin, but there might also be larger issues at stake. |
248 | |
249 | One of the precepts of the subversion idea is that we shouldn't give |
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250 | the patch pumpkin to anyone unless we have some idea what he or she |
251 | is going to do with it. |
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252 | |
253 | =head2 refresh pod/perltoc.pod |
254 | |
255 | Presumably, you have done a full C<make> in your working source |
256 | directory. Before you C<make spotless> (if you do), and if you have |
257 | changed any documentation in any module or pod file, change to the |
258 | F<pod> directory and run C<make toc>. |
259 | |
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260 | =head2 run installhtml to check the validity of the pod files |
261 | |
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262 | =head2 update patchlevel.h |
263 | |
264 | Don't be shy about using the subversion number, even for a relatively |
265 | modest patch. We've never even come close to using all 99 subversions, |
266 | and it's better to have a distinctive number for your patch. If you |
267 | need feedback on your patch, go ahead and issue it and promise to |
268 | incorporate that feedback quickly (e.g. within 1 week) and send out a |
269 | second patch. |
270 | |
271 | =head2 run metaconfig |
272 | |
273 | If you need to make changes to Configure or config_h.SH, it may be best to |
274 | change the appropriate metaconfig units instead, and regenerate Configure. |
275 | |
276 | metaconfig -m |
277 | |
278 | will regenerate Configure and config_h.SH. More information on |
279 | obtaining and running metaconfig is in the F<U/README> file that comes |
280 | with Perl's metaconfig units. Perl's metaconfig units should be |
281 | available the same place you found this file. On CPAN, look under my |
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282 | directory F<authors/id/ANDYD/> for a file such as F<5.003_07-02.U.tar.gz>. |
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283 | That file should be unpacked in your main perl source directory. It |
284 | contains the files needed to run B<metaconfig> to reproduce Perl's |
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285 | Configure script. (Those units are for 5.003_07. There have been |
286 | changes since then; please contact me if you want more recent |
287 | versions, and I will try to point you in the right direction.) |
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288 | |
289 | Alternatively, do consider if the F<*ish.h> files might be a better |
290 | place for your changes. |
291 | |
292 | =head2 MANIFEST |
293 | |
294 | Make sure the MANIFEST is up-to-date. You can use dist's B<manicheck> |
295 | program for this. You can also use |
296 | |
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297 | perl -w -MExtUtils::Manifest=fullcheck -e fullcheck |
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298 | |
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299 | Both commands will also list extra files in the directory that are not |
300 | listed in MANIFEST. |
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301 | |
302 | The MANIFEST is normally sorted, with one exception. Perl includes |
303 | both a F<Configure> script and a F<configure> script. The |
304 | F<configure> script is a front-end to the main F<Configure>, but |
305 | is there to aid folks who use autoconf-generated F<configure> files |
306 | for other software. The problem is that F<Configure> and F<configure> |
307 | are the same on case-insensitive file systems, so I deliberately put |
308 | F<configure> first in the MANIFEST so that the extraction of |
309 | F<Configure> will overwrite F<configure> and leave you with the |
310 | correct script. (The F<configure> script must also have write |
311 | permission for this to work, so it's the only file in the distribution |
312 | I normally have with write permission.) |
313 | |
314 | If you are using metaconfig to regenerate Configure, then you should note |
315 | that metaconfig actually uses MANIFEST.new, so you want to be sure |
316 | MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new |
317 | distinction particularly useful, but that's probably because I still haven't |
318 | learned how to use the full suite of tools in the dist distribution. |
319 | |
320 | =head2 Check permissions |
321 | |
322 | All the tests in the t/ directory ought to be executable. The |
323 | main makefile used to do a 'chmod t/*/*.t', but that resulted in |
324 | a self-modifying distribution--something some users would strongly |
325 | prefer to avoid. Probably, the F<t/TEST> script should check for this |
326 | and do the chmod if needed, but it doesn't currently. |
327 | |
328 | In all, the following files should probably be executable: |
329 | |
330 | Configure |
331 | configpm |
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332 | configure.gnu |
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333 | embed.pl |
334 | installperl |
335 | installman |
336 | keywords.pl |
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337 | myconfig |
338 | opcode.pl |
339 | perly.fixer |
340 | t/TEST |
341 | t/*/*.t |
342 | *.SH |
343 | vms/ext/Stdio/test.pl |
344 | vms/ext/filespec.t |
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345 | x2p/*.SH |
346 | |
347 | Other things ought to be readable, at least :-). |
348 | |
349 | Probably, the permissions for the files could be encoded in MANIFEST |
350 | somehow, but I'm reluctant to change MANIFEST itself because that |
351 | could break old scripts that use MANIFEST. |
352 | |
353 | I seem to recall that some SVR3 systems kept some sort of file that listed |
354 | permissions for system files; something like that might be appropriate. |
355 | |
356 | =head2 Run Configure |
357 | |
358 | This will build a config.sh and config.h. You can skip this if you haven't |
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359 | changed Configure or config_h.SH at all. I use the following command |
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360 | |
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361 | sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \ |
362 | -Dcf_by='yourname' \ |
363 | -Dcf_email='yourname@yourhost.yourplace.com' \ |
364 | -Dperladmin='yourname@yourhost.yourplace.com' \ |
365 | -Dmydomain='.yourplace.com' \ |
366 | -Dmyhostname='yourhost' \ |
367 | -des |
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368 | |
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369 | =head2 Update Porting/config.sh and Porting/config_H |
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370 | |
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371 | [XXX |
372 | This section needs revision. We're currently working on easing |
373 | the task of keeping the vms, win32, and plan9 config.sh info |
374 | up-to-date. The plan is to use keep up-to-date 'canned' config.sh |
375 | files in the appropriate subdirectories and then generate 'canned' |
376 | config.h files for vms, win32, etc. from the generic config.sh file. |
377 | This is to ease maintenance. When Configure gets updated, the parts |
378 | sometimes get scrambled around, and the changes in config_H can |
379 | sometimes be very hard to follow. config.sh, on the other hand, can |
380 | safely be sorted, so it's easy to track (typically very small) changes |
381 | to config.sh and then propoagate them to a canned 'config.h' by any |
382 | number of means, including a perl script in win32/ or carrying |
383 | config.sh and config_h.SH to a Unix system and running sh |
384 | config_h.SH.) |
385 | XXX] |
386 | |
387 | The Porting/config.sh and Porting/config_H files are provided to |
388 | help those folks who can't run Configure. It is important to keep |
389 | them up-to-date. If you have changed config_h.SH, those changes must |
390 | be reflected in config_H as well. (The name config_H was chosen to |
391 | distinguish the file from config.h even on case-insensitive file systems.) |
392 | Simply edit the existing config_H file; keep the first few explanatory |
393 | lines and then copy your new config.h below. |
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394 | |
395 | It may also be necessary to update vms/config.vms and |
396 | plan9/config.plan9, though you should be quite careful in doing so if |
397 | you are not familiar with those systems. You might want to issue your |
398 | patch with a promise to quickly issue a follow-up that handles those |
399 | directories. |
400 | |
401 | =head2 make run_byacc |
402 | |
403 | If you have byacc-1.8.2 (available from CPAN), and if there have been |
404 | changes to F<perly.y>, you can regenerate the F<perly.c> file. The |
405 | run_byacc makefile target does this by running byacc and then applying |
406 | some patches so that byacc dynamically allocates space, rather than |
407 | having fixed limits. This patch is handled by the F<perly.fixer> |
408 | script. Depending on the nature of the changes to F<perly.y>, you may |
409 | or may not have to hand-edit the patch to apply correctly. If you do, |
410 | you should include the edited patch in the new distribution. If you |
411 | have byacc-1.9, the patch won't apply cleanly. Changes to the printf |
412 | output statements mean the patch won't apply cleanly. Long ago I |
413 | started to fix F<perly.fixer> to detect this, but I never completed the |
414 | task. |
415 | |
416 | Some additional notes from Larry on this: |
417 | |
418 | Don't forget to regenerate perly.c.diff. |
419 | |
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420 | byacc -d perly.y |
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421 | mv y.tab.c perly.c |
422 | patch perly.c <perly.c.diff |
423 | # manually apply any failed hunks |
424 | diff -c2 perly.c.orig perly.c >perly.c.diff |
425 | |
426 | One chunk of lines that often fails begins with |
427 | |
428 | #line 29 "perly.y" |
429 | |
430 | and ends one line before |
431 | |
432 | #define YYERRCODE 256 |
433 | |
434 | This only happens when you add or remove a token type. I suppose this |
435 | could be automated, but it doesn't happen very often nowadays. |
436 | |
437 | Larry |
438 | |
439 | =head2 make regen_headers |
440 | |
441 | The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically |
442 | generated by perl scripts. Since the user isn't guaranteed to have a |
443 | working perl, we can't require the user to generate them. Hence you have |
444 | to, if you're making a distribution. |
445 | |
446 | I used to include rules like the following in the makefile: |
447 | |
448 | # The following three header files are generated automatically |
449 | # The correct versions should be already supplied with the perl kit, |
450 | # in case you don't have perl or 'sh' available. |
451 | # The - is to ignore error return codes in case you have the source |
452 | # installed read-only or you don't have perl yet. |
453 | keywords.h: keywords.pl |
454 | @echo "Don't worry if this fails." |
455 | - perl keywords.pl |
456 | |
457 | |
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458 | However, I got B<lots> of mail consisting of people worrying because the |
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459 | command failed. I eventually decided that I would save myself time |
460 | and effort by manually running C<make regen_headers> myself rather |
461 | than answering all the questions and complaints about the failing |
462 | command. |
463 | |
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464 | =head2 global.sym, interp.sym and perlio.sym |
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465 | |
466 | Make sure these files are up-to-date. Read the comments in these |
467 | files and in perl_exp.SH to see what to do. |
468 | |
469 | =head2 Binary compatibility |
470 | |
471 | If you do change F<global.sym> or F<interp.sym>, think carefully about |
472 | what you are doing. To the extent reasonable, we'd like to maintain |
473 | souce and binary compatibility with older releases of perl. That way, |
474 | extensions built under one version of perl will continue to work with |
475 | new versions of perl. |
476 | |
477 | Of course, some incompatible changes may well be necessary. I'm just |
478 | suggesting that we not make any such changes without thinking carefully |
479 | about them first. If possible, we should provide |
480 | backwards-compatibility stubs. There's a lot of XS code out there. |
481 | Let's not force people to keep changing it. |
482 | |
483 | =head2 Changes |
484 | |
485 | Be sure to update the F<Changes> file. Try to include both an overall |
486 | summary as well as detailed descriptions of the changes. Your |
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487 | audience will include other developers and users, so describe |
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488 | user-visible changes (if any) in terms they will understand, not in |
489 | code like "initialize foo variable in bar function". |
490 | |
491 | There are differing opinions on whether the detailed descriptions |
492 | ought to go in the Changes file or whether they ought to be available |
493 | separately in the patch file (or both). There is no disagreement that |
494 | detailed descriptions ought to be easily available somewhere. |
495 | |
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496 | =head2 Todo |
497 | |
498 | The F<Todo> file contains a roughly-catgorized unordered list of |
499 | aspects of Perl that could use enhancement, features that could be |
500 | added, areas that could be cleaned up, and so on. During your term as |
501 | pumpkin-holder, you will probably address some of these issues, and |
502 | perhaps identify others which, while you decide not to address them |
503 | this time around, may be tackled in the future. Update the file |
504 | reflect the situation as it stands when you hand over the pumpkin. |
505 | |
506 | You might like, early in your pumpkin-holding career, to see if you |
507 | can find champions for partiticular issues on the to-do list: an issue |
508 | owned is an issue more likely to be resolved. |
509 | |
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510 | There are also some more porting-specific L<Todo> items later in this |
511 | file. |
512 | |
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513 | =head2 OS/2-specific updates |
514 | |
515 | In the os2 directory is F<diff.configure>, a set of OS/2-specific |
516 | diffs against B<Configure>. If you make changes to Configure, you may |
517 | want to consider regenerating this diff file to save trouble for the |
518 | OS/2 maintainer. |
519 | |
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520 | You can also consider the OS/2 diffs as reminders of portability |
521 | things that need to be fixed in Configure. |
522 | |
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523 | =head2 VMS-specific updates |
524 | |
525 | If you have changed F<perly.y>, then you may want to update |
526 | F<vms/perly_{h,c}.vms> by running C<perl vms/vms_yfix.pl>. |
527 | |
528 | The Perl version number appears in several places under F<vms>. |
529 | It is courteous to update these versions. For example, if you are |
530 | making 5.004_42, replace "5.00441" with "5.00442". |
531 | |
532 | =head2 Making the new distribution |
533 | |
534 | Suppose, for example, that you want to make version 5.004_08. Then you can |
535 | do something like the following |
536 | |
537 | mkdir ../perl5.004_08 |
538 | awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08 |
539 | cd ../ |
540 | tar cf perl5.004_08.tar perl5.004_08 |
541 | gzip --best perl5.004_08.tar |
542 | |
3e3baf6d |
543 | These steps, with extra checks, are automated by the Porting/makerel |
544 | script. |
545 | |
aa689395 |
546 | =head2 Making a new patch |
547 | |
548 | I find the F<makepatch> utility quite handy for making patches. |
549 | You can obtain it from any CPAN archive under |
3e3baf6d |
550 | http://www.perl.com/CPAN/authors/Johan_Vromans/ . There are a couple |
551 | of differences between my version and the standard one. I have mine do |
552 | a |
aa689395 |
553 | |
554 | # Print a reassuring "End of Patch" note so people won't |
555 | # wonder if their mailer truncated patches. |
556 | print "\n\nEnd of Patch.\n"; |
557 | |
3e3baf6d |
558 | at the end. That's because I used to get questions from people asking |
559 | if their mail was truncated. |
560 | |
561 | It also writes Index: lines which include the new directory prefix |
562 | (change Index: print, approx line 294 or 310 depending on the version, |
563 | to read: print PATCH ("Index: $newdir$new\n");). That helps patches |
564 | work with more POSIX conformant patch programs. |
aa689395 |
565 | |
566 | Here's how I generate a new patch. I'll use the hypothetical |
567 | 5.004_07 to 5.004_08 patch as an example. |
568 | |
569 | # unpack perl5.004_07/ |
570 | gzip -d -c perl5.004_07.tar.gz | tar -xof - |
571 | # unpack perl5.004_08/ |
572 | gzip -d -c perl5.004_08.tar.gz | tar -xof - |
573 | makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat |
574 | |
575 | Makepatch will automatically generate appropriate B<rm> commands to remove |
576 | deleted files. Unfortunately, it will not correctly set permissions |
577 | for newly created files, so you may have to do so manually. For example, |
578 | patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable, |
579 | so at the top of the patch, I inserted the following lines: |
580 | |
581 | # Make a new test |
582 | touch t/op/gv.t |
583 | chmod +x t/opt/gv.t |
584 | |
585 | Now, of course, my patch is now wrong because makepatch didn't know I |
586 | was going to do that command, and it patched against /dev/null. |
587 | |
588 | So, what I do is sort out all such shell commands that need to be in the |
589 | patch (including possible mv-ing of files, if needed) and put that in the |
590 | shell commands at the top of the patch. Next, I delete all the patch parts |
591 | of perl5.004_08.pat, leaving just the shell commands. Then, I do the |
592 | following: |
593 | |
7b5757d1 |
594 | cd perl5.004_07 |
595 | sh ../perl5.004_08.pat |
aa689395 |
596 | cd .. |
7b5757d1 |
597 | makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat |
aa689395 |
598 | |
599 | (Note the append to preserve my shell commands.) |
600 | Now, my patch will line up with what the end users are going to do. |
601 | |
602 | =head2 Testing your patch |
603 | |
604 | It seems obvious, but be sure to test your patch. That is, verify that |
605 | it produces exactly the same thing as your full distribution. |
606 | |
7b5757d1 |
607 | rm -rf perl5.004_07 |
608 | gzip -d -c perl5.004_07.tar.gz | tar -xf - |
609 | cd perl5.004_07 |
610 | sh ../perl5.004_08.pat |
611 | patch -p1 -N < ../perl5.004_08.pat |
aa689395 |
612 | cd .. |
7b5757d1 |
613 | gdiff -r perl5.004_07 perl5.004_08 |
aa689395 |
614 | |
615 | where B<gdiff> is GNU diff. Other diff's may also do recursive checking. |
616 | |
617 | =head2 More testing |
618 | |
619 | Again, it's obvious, but you should test your new version as widely as you |
620 | can. You can be sure you'll hear about it quickly if your version doesn't |
621 | work on both ANSI and pre-ANSI compilers, and on common systems such as |
622 | SunOS 4.1.[34], Solaris, and Linux. |
623 | |
624 | If your changes include conditional code, try to test the different |
625 | branches as thoroughly as you can. For example, if your system |
626 | supports dynamic loading, you can also test static loading with |
627 | |
628 | sh Configure -Uusedl |
629 | |
630 | You can also hand-tweak your config.h to try out different #ifdef |
631 | branches. |
632 | |
633 | =head1 Common Gotcha's |
634 | |
635 | =over 4 |
636 | |
637 | =item #elif |
638 | |
639 | The '#elif' preprocessor directive is not understood on all systems. |
640 | Specifically, I know that Pyramids don't understand it. Thus instead of the |
641 | simple |
642 | |
643 | #if defined(I_FOO) |
644 | # include <foo.h> |
645 | #elif defined(I_BAR) |
646 | # include <bar.h> |
647 | #else |
648 | # include <fubar.h> |
649 | #endif |
650 | |
651 | You have to do the more Byzantine |
652 | |
653 | #if defined(I_FOO) |
654 | # include <foo.h> |
655 | #else |
656 | # if defined(I_BAR) |
657 | # include <bar.h> |
658 | # else |
659 | # include <fubar.h> |
660 | # endif |
661 | #endif |
662 | |
663 | Incidentally, whitespace between the leading '#' and the preprocessor |
664 | command is not guaranteed, but is very portable and you may use it freely. |
665 | I think it makes things a bit more readable, especially once things get |
666 | rather deeply nested. I also think that things should almost never get |
667 | too deeply nested, so it ought to be a moot point :-) |
668 | |
669 | =item Probably Prefer POSIX |
670 | |
671 | It's often the case that you'll need to choose whether to do |
672 | something the BSD-ish way or the POSIX-ish way. It's usually not |
673 | a big problem when the two systems use different names for similar |
674 | functions, such as memcmp() and bcmp(). The perl.h header file |
675 | handles these by appropriate #defines, selecting the POSIX mem*() |
676 | functions if available, but falling back on the b*() functions, if |
677 | need be. |
678 | |
679 | More serious is the case where some brilliant person decided to |
680 | use the same function name but give it a different meaning or |
681 | calling sequence :-). getpgrp() and setpgrp() come to mind. |
682 | These are a real problem on systems that aim for conformance to |
683 | one standard (e.g. POSIX), but still try to support the other way |
684 | of doing things (e.g. BSD). My general advice (still not really |
685 | implemented in the source) is to do something like the following. |
686 | Suppose there are two alternative versions, fooPOSIX() and |
687 | fooBSD(). |
688 | |
689 | #ifdef HAS_FOOPOSIX |
690 | /* use fooPOSIX(); */ |
691 | #else |
692 | # ifdef HAS_FOOBSD |
693 | /* try to emulate fooPOSIX() with fooBSD(); |
694 | perhaps with the following: */ |
695 | # define fooPOSIX fooBSD |
696 | # else |
697 | # /* Uh, oh. We have to supply our own. */ |
698 | # define fooPOSIX Perl_fooPOSIX |
699 | # endif |
700 | #endif |
701 | |
702 | =item Think positively |
703 | |
704 | If you need to add an #ifdef test, it is usually easier to follow if you |
705 | think positively, e.g. |
706 | |
707 | #ifdef HAS_NEATO_FEATURE |
708 | /* use neato feature */ |
709 | #else |
710 | /* use some fallback mechanism */ |
711 | #endif |
712 | |
713 | rather than the more impenetrable |
714 | |
715 | #ifndef MISSING_NEATO_FEATURE |
716 | /* Not missing it, so we must have it, so use it */ |
717 | #else |
718 | /* Are missing it, so fall back on something else. */ |
719 | #endif |
720 | |
721 | Of course for this toy example, there's not much difference. But when |
722 | the #ifdef's start spanning a couple of screen fulls, and the #else's |
723 | are marked something like |
724 | |
725 | #else /* !MISSING_NEATO_FEATURE */ |
726 | |
727 | I find it easy to get lost. |
728 | |
729 | =item Providing Missing Functions -- Problem |
730 | |
731 | Not all systems have all the neat functions you might want or need, so |
732 | you might decide to be helpful and provide an emulation. This is |
733 | sound in theory and very kind of you, but please be careful about what |
734 | you name the function. Let me use the C<pause()> function as an |
735 | illustration. |
736 | |
737 | Perl5.003 has the following in F<perl.h> |
738 | |
739 | #ifndef HAS_PAUSE |
740 | #define pause() sleep((32767<<16)+32767) |
741 | #endif |
742 | |
743 | Configure sets HAS_PAUSE if the system has the pause() function, so |
744 | this #define only kicks in if the pause() function is missing. |
745 | Nice idea, right? |
746 | |
747 | Unfortunately, some systems apparently have a prototype for pause() |
748 | in F<unistd.h>, but don't actually have the function in the library. |
749 | (Or maybe they do have it in a library we're not using.) |
750 | |
751 | Thus, the compiler sees something like |
752 | |
753 | extern int pause(void); |
754 | /* . . . */ |
755 | #define pause() sleep((32767<<16)+32767) |
756 | |
757 | and dies with an error message. (Some compilers don't mind this; |
758 | others apparently do.) |
759 | |
760 | To work around this, 5.003_03 and later have the following in perl.h: |
761 | |
762 | /* Some unistd.h's give a prototype for pause() even though |
763 | HAS_PAUSE ends up undefined. This causes the #define |
764 | below to be rejected by the compiler. Sigh. |
765 | */ |
766 | #ifdef HAS_PAUSE |
767 | # define Pause pause |
768 | #else |
769 | # define Pause() sleep((32767<<16)+32767) |
770 | #endif |
771 | |
772 | This works. |
773 | |
774 | The curious reader may wonder why I didn't do the following in |
775 | F<util.c> instead: |
776 | |
777 | #ifndef HAS_PAUSE |
778 | void pause() |
779 | { |
780 | sleep((32767<<16)+32767); |
781 | } |
782 | #endif |
783 | |
784 | That is, since the function is missing, just provide it. |
785 | Then things would probably be been alright, it would seem. |
786 | |
787 | Well, almost. It could be made to work. The problem arises from the |
788 | conflicting needs of dynamic loading and namespace protection. |
789 | |
790 | For dynamic loading to work on AIX (and VMS) we need to provide a list |
791 | of symbols to be exported. This is done by the script F<perl_exp.SH>, |
792 | which reads F<global.sym> and F<interp.sym>. Thus, the C<pause> |
793 | symbol would have to be added to F<global.sym> So far, so good. |
794 | |
795 | On the other hand, one of the goals of Perl5 is to make it easy to |
796 | either extend or embed perl and link it with other libraries. This |
797 | means we have to be careful to keep the visible namespace "clean". |
798 | That is, we don't want perl's global variables to conflict with |
799 | those in the other application library. Although this work is still |
800 | in progress, the way it is currently done is via the F<embed.h> file. |
801 | This file is built from the F<global.sym> and F<interp.sym> files, |
802 | since those files already list the globally visible symbols. If we |
803 | had added C<pause> to global.sym, then F<embed.h> would contain the |
804 | line |
805 | |
806 | #define pause Perl_pause |
807 | |
808 | and calls to C<pause> in the perl sources would now point to |
809 | C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable, |
810 | it will go looking for C<perl_pause>, which probably won't exist in any |
811 | of the standard libraries. Thus the build of perl will fail. |
812 | |
813 | Those systems where C<HAS_PAUSE> is not defined would be ok, however, |
814 | since they would get a C<Perl_pause> function in util.c. The rest of |
815 | the world would be in trouble. |
816 | |
817 | And yes, this scenario has happened. On SCO, the function C<chsize> |
818 | is available. (I think it's in F<-lx>, the Xenix compatibility |
819 | library.) Since the perl4 days (and possibly before), Perl has |
820 | included a C<chsize> function that gets called something akin to |
821 | |
822 | #ifndef HAS_CHSIZE |
823 | I32 chsize(fd, length) |
824 | /* . . . */ |
825 | #endif |
826 | |
827 | When 5.003 added |
828 | |
829 | #define chsize Perl_chsize |
830 | |
831 | to F<embed.h>, the compile started failing on SCO systems. |
832 | |
833 | The "fix" is to give the function a different name. The one |
834 | implemented in 5.003_05 isn't optimal, but here's what was done: |
835 | |
836 | #ifdef HAS_CHSIZE |
837 | # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */ |
838 | # undef my_chsize |
839 | # endif |
840 | # define my_chsize chsize |
841 | #endif |
842 | |
843 | My explanatory comment in patch 5.003_05 said: |
844 | |
845 | Undef and then re-define my_chsize from Perl_my_chsize to |
846 | just plain chsize if this system HAS_CHSIZE. This probably only |
847 | applies to SCO. This shows the perils of having internal |
848 | functions with the same name as external library functions :-). |
849 | |
850 | Now, we can safely put C<my_chsize> in F<global.sym>, export it, and |
851 | hide it with F<embed.h>. |
852 | |
853 | To be consistent with what I did for C<pause>, I probably should have |
854 | called the new function C<Chsize>, rather than C<my_chsize>. |
855 | However, the perl sources are quite inconsistent on this (Consider |
856 | New, Mymalloc, and Myremalloc, to name just a few.) |
857 | |
858 | There is a problem with this fix, however, in that C<Perl_chsize> |
859 | was available as a F<libperl.a> library function in 5.003, but it |
860 | isn't available any more (as of 5.003_07). This means that we've |
861 | broken binary compatibility. This is not good. |
862 | |
863 | =item Providing missing functions -- some ideas |
864 | |
865 | We currently don't have a standard way of handling such missing |
866 | function names. Right now, I'm effectively thinking aloud about a |
867 | solution. Some day, I'll try to formally propose a solution. |
868 | |
869 | Part of the problem is that we want to have some functions listed as |
870 | exported but not have their names mangled by embed.h or possibly |
871 | conflict with names in standard system headers. We actually already |
872 | have such a list at the end of F<perl_exp.SH> (though that list is |
873 | out-of-date): |
874 | |
875 | # extra globals not included above. |
876 | cat <<END >> perl.exp |
877 | perl_init_ext |
878 | perl_init_fold |
879 | perl_init_i18nl14n |
880 | perl_alloc |
881 | perl_construct |
882 | perl_destruct |
883 | perl_free |
884 | perl_parse |
885 | perl_run |
886 | perl_get_sv |
887 | perl_get_av |
888 | perl_get_hv |
889 | perl_get_cv |
890 | perl_call_argv |
891 | perl_call_pv |
892 | perl_call_method |
893 | perl_call_sv |
894 | perl_requirepv |
895 | safecalloc |
896 | safemalloc |
897 | saferealloc |
898 | safefree |
899 | |
900 | This still needs much thought, but I'm inclined to think that one |
901 | possible solution is to prefix all such functions with C<perl_> in the |
902 | source and list them along with the other C<perl_*> functions in |
903 | F<perl_exp.SH>. |
904 | |
905 | Thus, for C<chsize>, we'd do something like the following: |
906 | |
907 | /* in perl.h */ |
908 | #ifdef HAS_CHSIZE |
909 | # define perl_chsize chsize |
910 | #endif |
911 | |
912 | then in some file (e.g. F<util.c> or F<doio.c>) do |
913 | |
914 | #ifndef HAS_CHSIZE |
915 | I32 perl_chsize(fd, length) |
916 | /* implement the function here . . . */ |
917 | #endif |
918 | |
919 | Alternatively, we could just always use C<chsize> everywhere and move |
920 | C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would |
921 | probably be fine as long as our C<chsize> function agreed with all the |
922 | C<chsize> function prototypes in the various systems we'll be using. |
923 | As long as the prototypes in actual use don't vary that much, this is |
924 | probably a good alternative. (As a counter-example, note how Configure |
925 | and perl have to go through hoops to find and use get Malloc_t and |
926 | Free_t for C<malloc> and C<free>.) |
927 | |
928 | At the moment, this latter option is what I tend to prefer. |
929 | |
930 | =item All the world's a VAX |
931 | |
932 | Sorry, showing my age:-). Still, all the world is not BSD 4.[34], |
933 | SVR4, or POSIX. Be aware that SVR3-derived systems are still quite |
934 | common (do you have any idea how many systems run SCO?) If you don't |
935 | have a bunch of v7 manuals handy, the metaconfig units (by default |
936 | installed in F</usr/local/lib/dist/U>) are a good resource to look at |
937 | for portability. |
938 | |
939 | =back |
940 | |
941 | =head1 Miscellaneous Topics |
942 | |
943 | =head2 Autoconf |
944 | |
945 | Why does perl use a metaconfig-generated Configure script instead of an |
946 | autoconf-generated configure script? |
947 | |
948 | Metaconfig and autoconf are two tools with very similar purposes. |
949 | Metaconfig is actually the older of the two, and was originally written |
950 | by Larry Wall, while autoconf is probably now used in a wider variety of |
951 | packages. The autoconf info file discusses the history of autoconf and |
952 | how it came to be. The curious reader is referred there for further |
953 | information. |
954 | |
955 | Overall, both tools are quite good, I think, and the choice of which one |
956 | to use could be argued either way. In March, 1994, when I was just |
957 | starting to work on Configure support for Perl5, I considered both |
958 | autoconf and metaconfig, and eventually decided to use metaconfig for the |
959 | following reasons: |
960 | |
961 | =over 4 |
962 | |
963 | =item Compatibility with Perl4 |
964 | |
965 | Perl4 used metaconfig, so many of the #ifdef's were already set up for |
966 | metaconfig. Of course metaconfig had evolved some since Perl4's days, |
967 | but not so much that it posed any serious problems. |
968 | |
969 | =item Metaconfig worked for me |
970 | |
971 | My system at the time was Interactive 2.2, a SVR3.2/386 derivative that |
972 | also had some POSIX support. Metaconfig-generated Configure scripts |
973 | worked fine for me on that system. On the other hand, autoconf-generated |
974 | scripts usually didn't. (They did come quite close, though, in some |
975 | cases.) At the time, I actually fetched a large number of GNU packages |
976 | and checked. Not a single one configured and compiled correctly |
977 | out-of-the-box with the system's cc compiler. |
978 | |
979 | =item Configure can be interactive |
980 | |
981 | With both autoconf and metaconfig, if the script works, everything is |
982 | fine. However, one of my main problems with autoconf-generated scripts |
983 | was that if it guessed wrong about something, it could be B<very> hard to |
984 | go back and fix it. For example, autoconf always insisted on passing the |
985 | -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I |
986 | wanted or needed for that package. There was no way short of editing the |
987 | configure script to turn this off. You couldn't just edit the resulting |
988 | Makefile at the end because the -Xp flag influenced a number of other |
989 | configure tests. |
990 | |
991 | Metaconfig's Configure scripts, on the other hand, can be interactive. |
992 | Thus if Configure is guessing things incorrectly, you can go back and fix |
993 | them. This isn't as important now as it was when we were actively |
994 | developing Configure support for new features such as dynamic loading, |
995 | but it's still useful occasionally. |
996 | |
997 | =item GPL |
998 | |
999 | At the time, autoconf-generated scripts were covered under the GNU Public |
1000 | License, and hence weren't suitable for inclusion with Perl, which has a |
1001 | different licensing policy. (Autoconf's licensing has since changed.) |
1002 | |
1003 | =item Modularity |
1004 | |
1005 | Metaconfig builds up Configure from a collection of discrete pieces |
1006 | called "units". You can override the standard behavior by supplying your |
1007 | own unit. With autoconf, you have to patch the standard files instead. |
1008 | I find the metaconfig "unit" method easier to work with. Others |
1009 | may find metaconfig's units clumsy to work with. |
1010 | |
1011 | =back |
1012 | |
1013 | =head2 @INC search order |
1014 | |
1015 | By default, the list of perl library directories in @INC is the |
1016 | following: |
1017 | |
1018 | $archlib |
1019 | $privlib |
1020 | $sitearch |
1021 | $sitelib |
1022 | |
1023 | Specifically, on my Solaris/x86 system, I run |
1024 | B<sh Configure -Dprefix=/opt/perl> and I have the following |
1025 | directories: |
1026 | |
1027 | /opt/perl/lib/i86pc-solaris/5.00307 |
1028 | /opt/perl/lib |
1029 | /opt/perl/lib/site_perl/i86pc-solaris |
1030 | /opt/perl/lib/site_perl |
1031 | |
1032 | That is, perl's directories come first, followed by the site-specific |
1033 | directories. |
1034 | |
1035 | The site libraries come second to support the usage of extensions |
1036 | across perl versions. Read the relevant section in F<INSTALL> for |
1037 | more information. If we ever make $sitearch version-specific, this |
1038 | topic could be revisited. |
1039 | |
1040 | =head2 Why isn't there a directory to override Perl's library? |
1041 | |
1042 | Mainly because no one's gotten around to making one. Note that |
1043 | "making one" involves changing perl.c, Configure, config_h.SH (and |
1044 | associated files, see above), and I<documenting> it all in the |
1045 | INSTALL file. |
1046 | |
1047 | Apparently, most folks who want to override one of the standard library |
1048 | files simply do it by overwriting the standard library files. |
1049 | |
1050 | =head2 APPLLIB |
1051 | |
1052 | In the perl.c sources, you'll find an undocumented APPLLIB_EXP |
1053 | variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are |
1054 | documented in config_h.SH). Here's what APPLLIB_EXP is for, from |
1055 | a mail message from Larry: |
1056 | |
1057 | The main intent of APPLLIB_EXP is for folks who want to send out a |
1058 | version of Perl embedded in their product. They would set the symbol |
1059 | to be the name of the library containing the files needed to run or to |
1060 | support their particular application. This works at the "override" |
1061 | level to make sure they get their own versions of any library code that |
1062 | they absolutely must have configuration control over. |
1063 | |
1064 | As such, I don't see any conflict with a sysadmin using it for a |
1065 | override-ish sort of thing, when installing a generic Perl. It should |
1066 | probably have been named something to do with overriding though. Since |
1067 | it's undocumented we could still change it... :-) |
1068 | |
1069 | Given that it's already there, you can use it to override |
1070 | distribution modules. If you do |
1071 | |
1072 | sh Configure -Dccflags='-DAPPLLIB_EXP=/my/override' |
1073 | |
1074 | then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB. |
1075 | |
c4f23d77 |
1076 | =head2 Shared libperl.so location |
1077 | |
1078 | Why isn't the shared libperl.so installed in /usr/lib/ along |
1079 | with "all the other" shared libraries? Instead, it is installed |
1080 | in $archlib, which is typically something like |
1081 | |
1082 | /usr/local/lib/perl5/archname/5.00404 |
1083 | |
1084 | and is architecture- and version-specific. |
1085 | |
1086 | The basic reason why a shared libperl.so gets put in $archlib is so that |
1087 | you can have more than one version of perl on the system at the same time, |
1088 | and have each refer to its own libperl.so. |
1089 | |
1090 | Three examples might help. All of these work now; none would work if you |
1091 | put libperl.so in /usr/lib. |
1092 | |
1093 | =over |
1094 | |
1095 | =item 1. |
1096 | |
1097 | Suppose you want to have both threaded and non-threaded perl versions |
1098 | around. Configure will name both perl libraries "libperl.so" (so that |
1099 | you can link to them with -lperl). The perl binaries tell them apart |
1100 | by having looking in the appropriate $archlib directories. |
1101 | |
1102 | =item 2. |
1103 | |
1104 | Suppose you have perl5.004_04 installed and you want to try to compile |
1105 | it again, perhaps with different options or after applying a patch. |
1106 | If you already have libperl.so installed in /usr/lib/, then it may be |
1107 | either difficult or impossible to get ld.so to find the new libperl.so |
1108 | that you're trying to build. If, instead, libperl.so is tucked away in |
1109 | $archlib, then you can always just change $archlib in the current perl |
1110 | you're trying to build so that ld.so won't find your old libperl.so. |
1111 | (The INSTALL file suggests you do this when building a debugging perl.) |
1112 | |
1113 | =item 3. |
1114 | |
1115 | The shared perl library is not a "well-behaved" shared library with |
1116 | proper major and minor version numbers, so you can't necessarily |
1117 | have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose |
1118 | perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05 |
1119 | were to install /usr/lib/libperl.so.4.5. Now, when you try to run |
1120 | perl5.004_04, ld.so might try to load libperl.so.4.5, since it has |
1121 | the right "major version" number. If this works at all, it almost |
1122 | certainly defeats the reason for keeping perl5.004_04 around. Worse, |
1123 | with development subversions, you certaily can't guarantee that |
1124 | libperl.so.4.4 and libperl.so.4.55 will be compatible. |
1125 | |
1126 | Anyway, all this leads to quite obscure failures that are sure to drive |
1127 | casual users crazy. Even experienced users will get confused :-). Upon |
1128 | reflection, I'd say leave libperl.so in $archlib. |
1129 | |
1130 | =back |
1131 | |
aa689395 |
1132 | =head1 Upload Your Work to CPAN |
1133 | |
1134 | You can upload your work to CPAN if you have a CPAN id. Check out |
1135 | http://www.perl.com/CPAN/modules/04pause.html for information on |
1136 | _PAUSE_, the Perl Author's Upload Server. |
1137 | |
1138 | I typically upload both the patch file, e.g. F<perl5.004_08.pat.gz> |
1139 | and the full tar file, e.g. F<perl5.004_08.tar.gz>. |
1140 | |
1141 | If you want your patch to appear in the F<src/5.0/unsupported> |
1142 | directory on CPAN, send e-mail to the CPAN master librarian. (Check |
7b5757d1 |
1143 | out http://www.perl.com/CPAN/CPAN.html ). |
aa689395 |
1144 | |
1145 | =head1 Help Save the World |
1146 | |
1147 | You should definitely announce your patch on the perl5-porters list. |
1148 | You should also consider announcing your patch on |
1149 | comp.lang.perl.announce, though you should make it quite clear that a |
1150 | subversion is not a production release, and be prepared to deal with |
1151 | people who will not read your disclaimer. |
1152 | |
1153 | =head1 Todo |
1154 | |
1155 | Here, in no particular order, are some Configure and build-related |
1156 | items that merit consideration. This list isn't exhaustive, it's just |
1157 | what I came up with off the top of my head. |
1158 | |
1159 | =head2 Good ideas waiting for round tuits |
1160 | |
1161 | =over 4 |
1162 | |
1163 | =item installprefix |
1164 | |
1165 | I think we ought to support |
1166 | |
1167 | Configure -Dinstallprefix=/blah/blah |
1168 | |
1169 | Currently, we support B<-Dprefix=/blah/blah>, but the changing the install |
1170 | location has to be handled by something like the F<config.over> trick |
1171 | described in F<INSTALL>. AFS users also are treated specially. |
1172 | We should probably duplicate the metaconfig prefix stuff for an |
1173 | install prefix. |
1174 | |
c4f23d77 |
1175 | =item Configure -Dsrc=/blah/blah |
aa689395 |
1176 | |
1177 | We should be able to emulate B<configure --srcdir>. Tom Tromey |
1178 | tromey@creche.cygnus.com has submitted some patches to |
c4f23d77 |
1179 | the dist-users mailing list along these lines. They have been folded |
1180 | back into the main distribution, but various parts of the perl |
1181 | Configure/build/install process still assume src='.'. |
aa689395 |
1182 | |
1183 | =item Hint file fixes |
1184 | |
1185 | Various hint files work around Configure problems. We ought to fix |
1186 | Configure so that most of them aren't needed. |
1187 | |
1188 | =item Hint file information |
1189 | |
1190 | Some of the hint file information (particularly dynamic loading stuff) |
1191 | ought to be fed back into the main metaconfig distribution. |
1192 | |
c4f23d77 |
1193 | =item Catch GNU Libc "Stub" functions |
1194 | |
1195 | Some functions (such as lchown()) are present in libc, but are |
1196 | unimplmented. That is, they always fail and set errno=ENOSYS. |
1197 | |
1198 | Thomas Bushnell provided the following sample code and the explanation |
1199 | that follows: |
1200 | |
1201 | /* System header to define __stub macros and hopefully few prototypes, |
1202 | which can conflict with char FOO(); below. */ |
1203 | #include <assert.h> |
1204 | /* Override any gcc2 internal prototype to avoid an error. */ |
1205 | /* We use char because int might match the return type of a gcc2 |
1206 | builtin and then its argument prototype would still apply. */ |
1207 | char FOO(); |
1208 | |
1209 | int main() { |
1210 | |
1211 | /* The GNU C library defines this for functions which it implements |
1212 | to always fail with ENOSYS. Some functions are actually named |
1213 | something starting with __ and the normal name is an alias. */ |
1214 | #if defined (__stub_FOO) || defined (__stub___FOO) |
1215 | choke me |
1216 | #else |
1217 | FOO(); |
1218 | #endif |
1219 | |
1220 | ; return 0; } |
1221 | |
1222 | The choice of <assert.h> is essentially arbitrary. The GNU libc |
1223 | macros are found in <gnu/stubs.h>. You can include that file instead |
1224 | of <assert.h> (which itself includes <gnu/stubs.h>) if you test for |
1225 | its existence first. <assert.h> is assumed to exist on every system, |
1226 | which is why it's used here. Any GNU libc header file will include |
1227 | the stubs macros. If either __stub_NAME or __stub___NAME is defined, |
1228 | then the function doesn't actually exist. Tests using <assert.h> work |
1229 | on every system around. |
1230 | |
1231 | The declaration of FOO is there to override builtin prototypes for |
1232 | ANSI C functions. |
1233 | |
aa689395 |
1234 | =back |
1235 | |
1236 | =head2 Probably good ideas waiting for round tuits |
1237 | |
1238 | =over 4 |
1239 | |
1240 | =item GNU configure --options |
1241 | |
1242 | I've received sensible suggestions for --exec_prefix and other |
1243 | GNU configure --options. It's not always obvious exactly what is |
1244 | intended, but this merits investigation. |
1245 | |
1246 | =item make clean |
1247 | |
1248 | Currently, B<make clean> isn't all that useful, though |
1249 | B<make realclean> and B<make distclean> are. This needs a bit of |
1250 | thought and documentation before it gets cleaned up. |
1251 | |
1252 | =item Try gcc if cc fails |
1253 | |
1254 | Currently, we just give up. |
1255 | |
1256 | =item bypassing safe*alloc wrappers |
1257 | |
1258 | On some systems, it may be safe to call the system malloc directly |
1259 | without going through the util.c safe* layers. (Such systems would |
1260 | accept free(0), for example.) This might be a time-saver for systems |
1261 | that already have a good malloc. (Recent Linux libc's apparently have |
1262 | a nice malloc that is well-tuned for the system.) |
1263 | |
1264 | =back |
1265 | |
1266 | =head2 Vague possibilities |
1267 | |
1268 | =over 4 |
1269 | |
aa689395 |
1270 | =item MacPerl |
1271 | |
3e3baf6d |
1272 | Get some of the Macintosh stuff folded back into the main distribution. |
aa689395 |
1273 | |
1274 | =item gconvert replacement |
1275 | |
1276 | Maybe include a replacement function that doesn't lose data in rare |
1277 | cases of coercion between string and numerical values. |
1278 | |
aa689395 |
1279 | =item Improve makedepend |
1280 | |
1281 | The current makedepend process is clunky and annoyingly slow, but it |
1282 | works for most folks. Alas, it assumes that there is a filename |
1283 | $firstmakefile that the B<make> command will try to use before it uses |
1284 | F<Makefile>. Such may not be the case for all B<make> commands, |
1285 | particularly those on non-Unix systems. |
1286 | |
1287 | Probably some variant of the BSD F<.depend> file will be useful. |
1288 | We ought to check how other packages do this, if they do it at all. |
1289 | We could probably pre-generate the dependencies (with the exception of |
1290 | malloc.o, which could probably be determined at F<Makefile.SH> |
1291 | extraction time. |
1292 | |
1293 | =item GNU Makefile standard targets |
1294 | |
1295 | GNU software generally has standardized Makefile targets. Unless we |
1296 | have good reason to do otherwise, I see no reason not to support them. |
1297 | |
1298 | =item File locking |
1299 | |
1300 | Somehow, straighten out, document, and implement lockf(), flock(), |
1301 | and/or fcntl() file locking. It's a mess. |
1302 | |
1303 | =back |
1304 | |
fb73857a |
1305 | =head1 AUTHORS |
aa689395 |
1306 | |
fb73857a |
1307 | Original author: Andy Dougherty doughera@lafcol.lafayette.edu . |
1308 | Additions by Chip Salzenberg chip@perl.com and |
1309 | Tim Bunce Tim.Bunce@ig.co.uk . |
aa689395 |
1310 | |
1311 | All opinions expressed herein are those of the authorZ<>(s). |
1312 | |
1313 | =head1 LAST MODIFIED |
1314 | |
c4f23d77 |
1315 | $Id: pumpkin.pod,v 1.15 1998/04/23 17:03:48 doughera Released $ |