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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 | |
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11 | This document attempts to begin to describe some of the considerations |
12 | involved in patching, porting, and maintaining perl. |
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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 | The first rule of maintenance work is "First, do no harm." |
117 | |
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118 | =head2 Why such a complicated scheme? |
119 | |
120 | Two reasons, really. At least. |
121 | |
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122 | First, we need some way to identify and release collections of patches |
123 | that are known to have new features that need testing and exploration. The |
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124 | subversion scheme does that nicely while fitting into the |
125 | C<use 5.004;> mold. |
126 | |
127 | Second, since most of the folks who help maintain perl do so on a |
128 | free-time voluntary basis, perl development does not proceed at a |
129 | precise pace, though it always seems to be moving ahead quickly. |
130 | We needed some way to pass around the "patch pumpkin" to allow |
131 | different people chances to work on different aspects of the |
132 | distribution without getting in each other's way. It wouldn't be |
133 | constructive to have multiple people working on incompatible |
134 | implementations of the same idea. Instead what was needed was |
135 | some kind of "baton" or "token" to pass around so everyone knew |
136 | whose turn was next. |
137 | |
138 | =head2 Why is it called the patch pumpkin? |
139 | |
140 | Chip Salzenberg gets credit for that, with a nod to his cow orker, |
141 | David Croy. We had passed around various names (baton, token, hot |
142 | potato) but none caught on. Then, Chip asked: |
143 | |
144 | [begin quote] |
145 | |
146 | Who has the patch pumpkin? |
147 | |
148 | To explain: David Croy once told me once that at a previous job, |
149 | there was one tape drive and multiple systems that used it for backups. |
150 | But instead of some high-tech exclusion software, they used a low-tech |
151 | method to prevent multiple simultaneous backups: a stuffed pumpkin. |
152 | No one was allowed to make backups unless they had the "backup pumpkin". |
153 | |
154 | [end quote] |
155 | |
156 | The name has stuck. |
157 | |
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158 | =head1 Philosophical Issues in Patching and Porting Perl |
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159 | |
160 | There are no absolute rules, but there are some general guidelines I |
161 | have tried to follow as I apply patches to the perl sources. |
162 | (This section is still under construction.) |
163 | |
164 | =head2 Solve problems as generally as possible |
165 | |
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166 | Never implement a specific restricted solution to a problem when you |
167 | can solve the same problem in a more general, flexible way. |
168 | |
169 | For example, for dynamic loading to work on some SVR4 systems, we had |
170 | to build a shared libperl.so library. In order to build "FAT" binaries |
171 | on NeXT 4.0 systems, we had to build a special libperl library. Rather |
172 | than continuing to build a contorted nest of special cases, I |
173 | generalized the process of building libperl so that NeXT and SVR4 users |
174 | could still get their work done, but others could build a shared |
175 | libperl if they wanted to as well. |
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176 | |
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177 | Contain your changes carefully. Assume nothing about other operating |
178 | systems, not even closely related ones. Your changes must not affect |
179 | other platforms. |
180 | |
181 | Spy shamelessly on how similar patching or porting issues have been |
182 | settled elsewhere. |
183 | |
184 | If feasible, try to keep filenames 8.3-compliant to humor those poor |
185 | souls that get joy from running Perl under such dire limitations. |
186 | |
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187 | =head2 Seek consensus on major changes |
188 | |
189 | If you are making big changes, don't do it in secret. Discuss the |
190 | ideas in advance on perl5-porters. |
191 | |
192 | =head2 Keep the documentation up-to-date |
193 | |
194 | If your changes may affect how users use perl, then check to be sure |
195 | that the documentation is in sync with your changes. Be sure to |
196 | check all the files F<pod/*.pod> and also the F<INSTALL> document. |
197 | |
198 | Consider writing the appropriate documentation first and then |
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199 | implementing your change to correspond to the documentation. |
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200 | |
201 | =head2 Avoid machine-specific #ifdef's |
202 | |
203 | To the extent reasonable, try to avoid machine-specific #ifdef's in |
204 | the sources. Instead, use feature-specific #ifdef's. The reason is |
205 | that the machine-specific #ifdef's may not be valid across major |
206 | releases of the operating system. Further, the feature-specific tests |
207 | may help out folks on another platform who have the same problem. |
208 | |
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209 | =head2 Machine-specific files |
210 | |
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211 | =over 4 |
212 | |
213 | =item source code |
214 | |
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215 | If you have many machine-specific #defines or #includes, consider |
216 | creating an "osish.h" (os2ish.h, vmsish.h, and so on) and including |
217 | that in perl.h. If you have several machine-specific files (function |
218 | emulations, function stubs, build utility wrappers) you may create a |
219 | separate subdirectory (djgpp, win32) and put the files in there. |
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220 | Remember to update C<MANIFEST> when you add files. |
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221 | |
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222 | If your system support dynamic loading but none of the existing |
223 | methods at F<ext/DynaLoader/dl_*.xs> work for you, you must write |
224 | a new one. Study the existing ones to see what kind of interface |
225 | you must supply. |
226 | |
227 | =item build hints |
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228 | |
229 | There are two kinds of hints: hints for building Perl and hints for |
230 | extensions. The former live in the C<hints> subdirectory, the latter |
231 | in C<ext/*/hints> subdirectories. |
232 | |
233 | The top level hints are Bourne-shell scripts that set, modify and |
234 | unset appropriate Configure variables, based on the Configure command |
235 | line options and possibly existing config.sh and Policy.sh files from |
236 | previous Configure runs. |
237 | |
238 | The extension hints are written Perl (by the time they are used |
239 | miniperl has been built) and control the building of their respective |
240 | extensions. They can be used to for example manipulate compilation |
241 | and linking flags. |
242 | |
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243 | =item build and installation Makefiles, scripts, and so forth |
244 | |
245 | Sometimes you will also need to tweak the Perl build and installation |
246 | procedure itself, like for example F<Makefile.SH> and F<installperl>. |
247 | Tread very carefully, even more than usual. Contain your changes |
248 | with utmost care. |
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249 | |
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250 | =item test suite |
251 | |
252 | Many of the tests in C<t> subdirectory assume machine-specific things |
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253 | like existence of certain functions, something about filesystem |
254 | semantics, certain external utilities and their error messages. Use |
255 | the C<$^O> and the C<Config> module (which contains the results of the |
256 | Configure run, in effect the C<config.sh> converted to Perl) to either |
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257 | skip (preferably not) or customize (preferable) the tests for your |
258 | platform. |
259 | |
260 | =item modules |
261 | |
262 | Certain standard modules may need updating if your operating system |
263 | sports for example a native filesystem naming. You may want to update |
264 | some or all of the modules File::Basename, File::Spec, File::Path, and |
265 | File::Copy to become aware of your native filesystem syntax and |
266 | peculiarities. |
267 | |
268 | =item documentation |
269 | |
270 | If your operating system comes from outside UNIX you almost certainly |
271 | will have differences in the available operating system functionality |
272 | (missing system calls, different semantics, whatever). Please |
273 | document these at F<pod/perlport.pod>. If your operating system is |
274 | the first B<not> to have a system call also update the list of |
275 | "portability-bewares" at the beginning of F<pod/perlfunc.pod>. |
276 | |
277 | A file called F<README.youros> at the top level that explains things |
278 | like how to install perl at this platform, where to get any possibly |
279 | required additional software, and for example what test suite errors |
280 | to expect, is nice too. |
281 | |
282 | You may also want to write a separate F<.pod> file for your operating |
283 | system to tell about existing mailing lists, os-specific modules, |
284 | documentation, whatever. Please name these along the lines of |
285 | F<perl>I<youros>.pod. [unfinished: where to put this file (the pod/ |
286 | subdirectory, of course: but more importantly, which/what index files |
287 | should be updated?)] |
288 | |
289 | =back |
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290 | |
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291 | =head2 Allow for lots of testing |
292 | |
293 | We should never release a main version without testing it as a |
294 | subversion first. |
295 | |
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296 | =head2 Test popular applications and modules. |
297 | |
298 | We should never release a main version without testing whether or not |
299 | it breaks various popular modules and applications. A partial list of |
300 | such things would include majordomo, metaconfig, apache, Tk, CGI, |
301 | libnet, and libwww, to name just a few. Of course it's quite possible |
302 | that some of those things will be just plain broken and need to be fixed, |
303 | but, in general, we ought to try to avoid breaking widely-installed |
304 | things. |
305 | |
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306 | =head2 Automated generation of derivative files |
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307 | |
308 | The F<embed.h>, F<keywords.h>, F<opcode.h>, and F<perltoc.pod> files |
309 | are all automatically generated by perl scripts. In general, don't |
310 | patch these directly; patch the data files instead. |
311 | |
312 | F<Configure> and F<config_h.SH> are also automatically generated by |
313 | B<metaconfig>. In general, you should patch the metaconfig units |
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314 | instead of patching these files directly. However, very minor changes |
315 | to F<Configure> may be made in between major sync-ups with the |
316 | metaconfig units, which tends to be complicated operations. But be |
317 | careful, this can quickly spiral out of control. Running metaconfig |
318 | is not really hard. |
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319 | |
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320 | Also F<Makefile> is automatically produced from F<Makefile.SH>. |
321 | In general, look out for all F<*.SH> files. |
322 | |
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323 | Finally, the sample files in the F<Porting/> subdirectory are |
324 | generated automatically by the script F<U/mksample> included |
325 | with the metaconfig units. See L<"run metaconfig"> below for |
326 | information on obtaining the metaconfig units. |
327 | |
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328 | =head1 How to Make a Distribution |
329 | |
330 | There really ought to be a 'make dist' target, but there isn't. |
331 | The 'dist' suite of tools also contains a number of tools that I haven't |
332 | learned how to use yet. Some of them may make this all a bit easier. |
333 | |
334 | Here are the steps I go through to prepare a patch & distribution. |
335 | |
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336 | Lots of it could doubtless be automated but isn't. The Porting/makerel |
337 | (make release) perl script does now help automate some parts of it. |
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338 | |
339 | =head2 Announce your intentions |
340 | |
341 | First, you should volunteer out loud to take the patch pumpkin. It's |
342 | generally counter-productive to have multiple people working in secret |
343 | on the same thing. |
344 | |
345 | At the same time, announce what you plan to do with the patch pumpkin, |
346 | to allow folks a chance to object or suggest alternatives, or do it for |
347 | you. Naturally, the patch pumpkin holder ought to incorporate various |
348 | bug fixes and documentation improvements that are posted while he or |
349 | she has the pumpkin, but there might also be larger issues at stake. |
350 | |
351 | One of the precepts of the subversion idea is that we shouldn't give |
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352 | the patch pumpkin to anyone unless we have some idea what he or she |
353 | is going to do with it. |
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354 | |
355 | =head2 refresh pod/perltoc.pod |
356 | |
357 | Presumably, you have done a full C<make> in your working source |
358 | directory. Before you C<make spotless> (if you do), and if you have |
359 | changed any documentation in any module or pod file, change to the |
360 | F<pod> directory and run C<make toc>. |
361 | |
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362 | =head2 run installhtml to check the validity of the pod files |
363 | |
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364 | =head2 update patchlevel.h |
365 | |
366 | Don't be shy about using the subversion number, even for a relatively |
367 | modest patch. We've never even come close to using all 99 subversions, |
368 | and it's better to have a distinctive number for your patch. If you |
369 | need feedback on your patch, go ahead and issue it and promise to |
370 | incorporate that feedback quickly (e.g. within 1 week) and send out a |
371 | second patch. |
372 | |
373 | =head2 run metaconfig |
374 | |
375 | If you need to make changes to Configure or config_h.SH, it may be best to |
376 | change the appropriate metaconfig units instead, and regenerate Configure. |
377 | |
378 | metaconfig -m |
379 | |
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380 | will regenerate Configure and config_h.SH. Much more information |
381 | on obtaining and running metaconfig is in the F<U/README> file |
382 | that comes with Perl's metaconfig units. Perl's metaconfig units |
383 | should be available on CPAN. A set of units that will work with |
384 | perl5.005 is in the file F<mc_units-5.005_00-01.tar.gz> under |
385 | http://www.perl.com/CPAN/authors/id/ANDYD/ . The mc_units tar file |
386 | should be unpacked in your main perl source directory. Note: those |
387 | units were for use with 5.005. There may have been changes since then. |
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388 | Check for later versions or contact perl5-porters@perl.org to obtain a |
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389 | pointer to the current version. |
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390 | |
391 | Alternatively, do consider if the F<*ish.h> files might be a better |
392 | place for your changes. |
393 | |
394 | =head2 MANIFEST |
395 | |
396 | Make sure the MANIFEST is up-to-date. You can use dist's B<manicheck> |
397 | program for this. You can also use |
398 | |
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399 | perl -w -MExtUtils::Manifest=fullcheck -e fullcheck |
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400 | |
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401 | Both commands will also list extra files in the directory that are not |
402 | listed in MANIFEST. |
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403 | |
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404 | The MANIFEST is normally sorted. |
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405 | |
406 | If you are using metaconfig to regenerate Configure, then you should note |
407 | that metaconfig actually uses MANIFEST.new, so you want to be sure |
408 | MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new |
409 | distinction particularly useful, but that's probably because I still haven't |
410 | learned how to use the full suite of tools in the dist distribution. |
411 | |
412 | =head2 Check permissions |
413 | |
414 | All the tests in the t/ directory ought to be executable. The |
415 | main makefile used to do a 'chmod t/*/*.t', but that resulted in |
416 | a self-modifying distribution--something some users would strongly |
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417 | prefer to avoid. The F<t/TEST> script will check for this |
418 | and do the chmod if needed, but the tests still ought to be |
419 | executable. |
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420 | |
421 | In all, the following files should probably be executable: |
422 | |
423 | Configure |
424 | configpm |
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425 | configure.gnu |
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426 | embed.pl |
427 | installperl |
428 | installman |
429 | keywords.pl |
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430 | myconfig |
431 | opcode.pl |
432 | perly.fixer |
433 | t/TEST |
434 | t/*/*.t |
435 | *.SH |
436 | vms/ext/Stdio/test.pl |
437 | vms/ext/filespec.t |
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438 | x2p/*.SH |
439 | |
440 | Other things ought to be readable, at least :-). |
441 | |
442 | Probably, the permissions for the files could be encoded in MANIFEST |
443 | somehow, but I'm reluctant to change MANIFEST itself because that |
444 | could break old scripts that use MANIFEST. |
445 | |
446 | I seem to recall that some SVR3 systems kept some sort of file that listed |
447 | permissions for system files; something like that might be appropriate. |
448 | |
449 | =head2 Run Configure |
450 | |
451 | This will build a config.sh and config.h. You can skip this if you haven't |
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452 | changed Configure or config_h.SH at all. I use the following command |
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453 | |
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454 | sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \ |
455 | -Dcf_by='yourname' \ |
456 | -Dcf_email='yourname@yourhost.yourplace.com' \ |
457 | -Dperladmin='yourname@yourhost.yourplace.com' \ |
458 | -Dmydomain='.yourplace.com' \ |
459 | -Dmyhostname='yourhost' \ |
460 | -des |
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461 | |
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462 | =head2 Update Porting/config.sh and Porting/config_H |
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463 | |
693762b4 |
464 | [XXX |
465 | This section needs revision. We're currently working on easing |
466 | the task of keeping the vms, win32, and plan9 config.sh info |
467 | up-to-date. The plan is to use keep up-to-date 'canned' config.sh |
468 | files in the appropriate subdirectories and then generate 'canned' |
469 | config.h files for vms, win32, etc. from the generic config.sh file. |
470 | This is to ease maintenance. When Configure gets updated, the parts |
471 | sometimes get scrambled around, and the changes in config_H can |
472 | sometimes be very hard to follow. config.sh, on the other hand, can |
473 | safely be sorted, so it's easy to track (typically very small) changes |
474 | to config.sh and then propoagate them to a canned 'config.h' by any |
475 | number of means, including a perl script in win32/ or carrying |
476 | config.sh and config_h.SH to a Unix system and running sh |
477 | config_h.SH.) |
478 | XXX] |
479 | |
480 | The Porting/config.sh and Porting/config_H files are provided to |
481 | help those folks who can't run Configure. It is important to keep |
482 | them up-to-date. If you have changed config_h.SH, those changes must |
483 | be reflected in config_H as well. (The name config_H was chosen to |
484 | distinguish the file from config.h even on case-insensitive file systems.) |
485 | Simply edit the existing config_H file; keep the first few explanatory |
486 | lines and then copy your new config.h below. |
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487 | |
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488 | It may also be necessary to update win32/config.?c, vms/config.vms and |
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489 | plan9/config.plan9, though you should be quite careful in doing so if |
490 | you are not familiar with those systems. You might want to issue your |
491 | patch with a promise to quickly issue a follow-up that handles those |
492 | directories. |
493 | |
494 | =head2 make run_byacc |
495 | |
496 | If you have byacc-1.8.2 (available from CPAN), and if there have been |
497 | changes to F<perly.y>, you can regenerate the F<perly.c> file. The |
498 | run_byacc makefile target does this by running byacc and then applying |
499 | some patches so that byacc dynamically allocates space, rather than |
500 | having fixed limits. This patch is handled by the F<perly.fixer> |
501 | script. Depending on the nature of the changes to F<perly.y>, you may |
502 | or may not have to hand-edit the patch to apply correctly. If you do, |
503 | you should include the edited patch in the new distribution. If you |
504 | have byacc-1.9, the patch won't apply cleanly. Changes to the printf |
505 | output statements mean the patch won't apply cleanly. Long ago I |
506 | started to fix F<perly.fixer> to detect this, but I never completed the |
507 | task. |
508 | |
ebb99254 |
509 | If C<perly.c> changes, make sure you run C<perl vms/vms_yfix.pl> to |
510 | update the corresponding VMS files. See L<VMS-specific updates>. |
511 | |
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512 | Some additional notes from Larry on this: |
513 | |
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514 | Don't forget to regenerate perly_c.diff. |
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515 | |
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516 | byacc -d perly.y |
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517 | mv y.tab.c perly.c |
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518 | patch perly.c <perly_c.diff |
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519 | # manually apply any failed hunks |
e262e9be |
520 | diff -c2 perly.c.orig perly.c >perly_c.diff |
aa689395 |
521 | |
522 | One chunk of lines that often fails begins with |
523 | |
524 | #line 29 "perly.y" |
525 | |
526 | and ends one line before |
527 | |
528 | #define YYERRCODE 256 |
529 | |
530 | This only happens when you add or remove a token type. I suppose this |
531 | could be automated, but it doesn't happen very often nowadays. |
532 | |
533 | Larry |
534 | |
535 | =head2 make regen_headers |
536 | |
537 | The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically |
538 | generated by perl scripts. Since the user isn't guaranteed to have a |
539 | working perl, we can't require the user to generate them. Hence you have |
540 | to, if you're making a distribution. |
541 | |
542 | I used to include rules like the following in the makefile: |
543 | |
544 | # The following three header files are generated automatically |
545 | # The correct versions should be already supplied with the perl kit, |
546 | # in case you don't have perl or 'sh' available. |
547 | # The - is to ignore error return codes in case you have the source |
548 | # installed read-only or you don't have perl yet. |
549 | keywords.h: keywords.pl |
550 | @echo "Don't worry if this fails." |
551 | - perl keywords.pl |
552 | |
553 | |
7b5757d1 |
554 | However, I got B<lots> of mail consisting of people worrying because the |
aa689395 |
555 | command failed. I eventually decided that I would save myself time |
556 | and effort by manually running C<make regen_headers> myself rather |
557 | than answering all the questions and complaints about the failing |
558 | command. |
559 | |
3e3baf6d |
560 | =head2 global.sym, interp.sym and perlio.sym |
aa689395 |
561 | |
562 | Make sure these files are up-to-date. Read the comments in these |
563 | files and in perl_exp.SH to see what to do. |
564 | |
565 | =head2 Binary compatibility |
566 | |
567 | If you do change F<global.sym> or F<interp.sym>, think carefully about |
568 | what you are doing. To the extent reasonable, we'd like to maintain |
569 | souce and binary compatibility with older releases of perl. That way, |
570 | extensions built under one version of perl will continue to work with |
571 | new versions of perl. |
572 | |
573 | Of course, some incompatible changes may well be necessary. I'm just |
574 | suggesting that we not make any such changes without thinking carefully |
575 | about them first. If possible, we should provide |
576 | backwards-compatibility stubs. There's a lot of XS code out there. |
577 | Let's not force people to keep changing it. |
578 | |
579 | =head2 Changes |
580 | |
581 | Be sure to update the F<Changes> file. Try to include both an overall |
582 | summary as well as detailed descriptions of the changes. Your |
3e3baf6d |
583 | audience will include other developers and users, so describe |
aa689395 |
584 | user-visible changes (if any) in terms they will understand, not in |
585 | code like "initialize foo variable in bar function". |
586 | |
587 | There are differing opinions on whether the detailed descriptions |
588 | ought to go in the Changes file or whether they ought to be available |
589 | separately in the patch file (or both). There is no disagreement that |
590 | detailed descriptions ought to be easily available somewhere. |
591 | |
2a26e2f1 |
592 | =head2 Todo |
593 | |
594 | The F<Todo> file contains a roughly-catgorized unordered list of |
595 | aspects of Perl that could use enhancement, features that could be |
596 | added, areas that could be cleaned up, and so on. During your term as |
597 | pumpkin-holder, you will probably address some of these issues, and |
598 | perhaps identify others which, while you decide not to address them |
599 | this time around, may be tackled in the future. Update the file |
600 | reflect the situation as it stands when you hand over the pumpkin. |
601 | |
602 | You might like, early in your pumpkin-holding career, to see if you |
603 | can find champions for partiticular issues on the to-do list: an issue |
604 | owned is an issue more likely to be resolved. |
605 | |
c4f23d77 |
606 | There are also some more porting-specific L<Todo> items later in this |
607 | file. |
608 | |
aa689395 |
609 | =head2 OS/2-specific updates |
610 | |
611 | In the os2 directory is F<diff.configure>, a set of OS/2-specific |
612 | diffs against B<Configure>. If you make changes to Configure, you may |
613 | want to consider regenerating this diff file to save trouble for the |
614 | OS/2 maintainer. |
615 | |
7b5757d1 |
616 | You can also consider the OS/2 diffs as reminders of portability |
617 | things that need to be fixed in Configure. |
618 | |
aa689395 |
619 | =head2 VMS-specific updates |
620 | |
ebb99254 |
621 | If you have changed F<perly.y> or F<perly.c>, then you most probably want |
622 | to update F<vms/perly_{h,c}.vms> by running C<perl vms/vms_yfix.pl>. |
aa689395 |
623 | |
624 | The Perl version number appears in several places under F<vms>. |
625 | It is courteous to update these versions. For example, if you are |
626 | making 5.004_42, replace "5.00441" with "5.00442". |
627 | |
628 | =head2 Making the new distribution |
629 | |
630 | Suppose, for example, that you want to make version 5.004_08. Then you can |
631 | do something like the following |
632 | |
633 | mkdir ../perl5.004_08 |
634 | awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08 |
635 | cd ../ |
636 | tar cf perl5.004_08.tar perl5.004_08 |
637 | gzip --best perl5.004_08.tar |
638 | |
3e3baf6d |
639 | These steps, with extra checks, are automated by the Porting/makerel |
640 | script. |
641 | |
aa689395 |
642 | =head2 Making a new patch |
643 | |
644 | I find the F<makepatch> utility quite handy for making patches. |
645 | You can obtain it from any CPAN archive under |
3e3baf6d |
646 | http://www.perl.com/CPAN/authors/Johan_Vromans/ . There are a couple |
647 | of differences between my version and the standard one. I have mine do |
648 | a |
aa689395 |
649 | |
650 | # Print a reassuring "End of Patch" note so people won't |
651 | # wonder if their mailer truncated patches. |
652 | print "\n\nEnd of Patch.\n"; |
653 | |
3e3baf6d |
654 | at the end. That's because I used to get questions from people asking |
655 | if their mail was truncated. |
656 | |
657 | It also writes Index: lines which include the new directory prefix |
658 | (change Index: print, approx line 294 or 310 depending on the version, |
659 | to read: print PATCH ("Index: $newdir$new\n");). That helps patches |
660 | work with more POSIX conformant patch programs. |
aa689395 |
661 | |
662 | Here's how I generate a new patch. I'll use the hypothetical |
663 | 5.004_07 to 5.004_08 patch as an example. |
664 | |
665 | # unpack perl5.004_07/ |
666 | gzip -d -c perl5.004_07.tar.gz | tar -xof - |
667 | # unpack perl5.004_08/ |
668 | gzip -d -c perl5.004_08.tar.gz | tar -xof - |
669 | makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat |
670 | |
671 | Makepatch will automatically generate appropriate B<rm> commands to remove |
672 | deleted files. Unfortunately, it will not correctly set permissions |
673 | for newly created files, so you may have to do so manually. For example, |
674 | patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable, |
675 | so at the top of the patch, I inserted the following lines: |
676 | |
677 | # Make a new test |
678 | touch t/op/gv.t |
679 | chmod +x t/opt/gv.t |
680 | |
681 | Now, of course, my patch is now wrong because makepatch didn't know I |
682 | was going to do that command, and it patched against /dev/null. |
683 | |
684 | So, what I do is sort out all such shell commands that need to be in the |
685 | patch (including possible mv-ing of files, if needed) and put that in the |
686 | shell commands at the top of the patch. Next, I delete all the patch parts |
687 | of perl5.004_08.pat, leaving just the shell commands. Then, I do the |
688 | following: |
689 | |
7b5757d1 |
690 | cd perl5.004_07 |
691 | sh ../perl5.004_08.pat |
aa689395 |
692 | cd .. |
7b5757d1 |
693 | makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat |
aa689395 |
694 | |
695 | (Note the append to preserve my shell commands.) |
696 | Now, my patch will line up with what the end users are going to do. |
697 | |
698 | =head2 Testing your patch |
699 | |
700 | It seems obvious, but be sure to test your patch. That is, verify that |
701 | it produces exactly the same thing as your full distribution. |
702 | |
7b5757d1 |
703 | rm -rf perl5.004_07 |
704 | gzip -d -c perl5.004_07.tar.gz | tar -xf - |
705 | cd perl5.004_07 |
706 | sh ../perl5.004_08.pat |
707 | patch -p1 -N < ../perl5.004_08.pat |
aa689395 |
708 | cd .. |
7b5757d1 |
709 | gdiff -r perl5.004_07 perl5.004_08 |
aa689395 |
710 | |
711 | where B<gdiff> is GNU diff. Other diff's may also do recursive checking. |
712 | |
713 | =head2 More testing |
714 | |
715 | Again, it's obvious, but you should test your new version as widely as you |
716 | can. You can be sure you'll hear about it quickly if your version doesn't |
717 | work on both ANSI and pre-ANSI compilers, and on common systems such as |
718 | SunOS 4.1.[34], Solaris, and Linux. |
719 | |
720 | If your changes include conditional code, try to test the different |
721 | branches as thoroughly as you can. For example, if your system |
722 | supports dynamic loading, you can also test static loading with |
723 | |
724 | sh Configure -Uusedl |
725 | |
726 | You can also hand-tweak your config.h to try out different #ifdef |
727 | branches. |
728 | |
729 | =head1 Common Gotcha's |
730 | |
731 | =over 4 |
732 | |
733 | =item #elif |
734 | |
735 | The '#elif' preprocessor directive is not understood on all systems. |
736 | Specifically, I know that Pyramids don't understand it. Thus instead of the |
737 | simple |
738 | |
739 | #if defined(I_FOO) |
740 | # include <foo.h> |
741 | #elif defined(I_BAR) |
742 | # include <bar.h> |
743 | #else |
744 | # include <fubar.h> |
745 | #endif |
746 | |
747 | You have to do the more Byzantine |
748 | |
749 | #if defined(I_FOO) |
750 | # include <foo.h> |
751 | #else |
752 | # if defined(I_BAR) |
753 | # include <bar.h> |
754 | # else |
755 | # include <fubar.h> |
756 | # endif |
757 | #endif |
758 | |
759 | Incidentally, whitespace between the leading '#' and the preprocessor |
760 | command is not guaranteed, but is very portable and you may use it freely. |
761 | I think it makes things a bit more readable, especially once things get |
762 | rather deeply nested. I also think that things should almost never get |
763 | too deeply nested, so it ought to be a moot point :-) |
764 | |
765 | =item Probably Prefer POSIX |
766 | |
767 | It's often the case that you'll need to choose whether to do |
768 | something the BSD-ish way or the POSIX-ish way. It's usually not |
769 | a big problem when the two systems use different names for similar |
770 | functions, such as memcmp() and bcmp(). The perl.h header file |
771 | handles these by appropriate #defines, selecting the POSIX mem*() |
772 | functions if available, but falling back on the b*() functions, if |
773 | need be. |
774 | |
775 | More serious is the case where some brilliant person decided to |
776 | use the same function name but give it a different meaning or |
777 | calling sequence :-). getpgrp() and setpgrp() come to mind. |
778 | These are a real problem on systems that aim for conformance to |
779 | one standard (e.g. POSIX), but still try to support the other way |
780 | of doing things (e.g. BSD). My general advice (still not really |
781 | implemented in the source) is to do something like the following. |
782 | Suppose there are two alternative versions, fooPOSIX() and |
783 | fooBSD(). |
784 | |
785 | #ifdef HAS_FOOPOSIX |
786 | /* use fooPOSIX(); */ |
787 | #else |
788 | # ifdef HAS_FOOBSD |
789 | /* try to emulate fooPOSIX() with fooBSD(); |
790 | perhaps with the following: */ |
791 | # define fooPOSIX fooBSD |
792 | # else |
793 | # /* Uh, oh. We have to supply our own. */ |
794 | # define fooPOSIX Perl_fooPOSIX |
795 | # endif |
796 | #endif |
797 | |
798 | =item Think positively |
799 | |
800 | If you need to add an #ifdef test, it is usually easier to follow if you |
801 | think positively, e.g. |
802 | |
803 | #ifdef HAS_NEATO_FEATURE |
804 | /* use neato feature */ |
805 | #else |
806 | /* use some fallback mechanism */ |
807 | #endif |
808 | |
809 | rather than the more impenetrable |
810 | |
811 | #ifndef MISSING_NEATO_FEATURE |
812 | /* Not missing it, so we must have it, so use it */ |
813 | #else |
814 | /* Are missing it, so fall back on something else. */ |
815 | #endif |
816 | |
817 | Of course for this toy example, there's not much difference. But when |
818 | the #ifdef's start spanning a couple of screen fulls, and the #else's |
819 | are marked something like |
820 | |
821 | #else /* !MISSING_NEATO_FEATURE */ |
822 | |
823 | I find it easy to get lost. |
824 | |
825 | =item Providing Missing Functions -- Problem |
826 | |
827 | Not all systems have all the neat functions you might want or need, so |
828 | you might decide to be helpful and provide an emulation. This is |
829 | sound in theory and very kind of you, but please be careful about what |
830 | you name the function. Let me use the C<pause()> function as an |
831 | illustration. |
832 | |
833 | Perl5.003 has the following in F<perl.h> |
834 | |
835 | #ifndef HAS_PAUSE |
836 | #define pause() sleep((32767<<16)+32767) |
837 | #endif |
838 | |
839 | Configure sets HAS_PAUSE if the system has the pause() function, so |
840 | this #define only kicks in if the pause() function is missing. |
841 | Nice idea, right? |
842 | |
843 | Unfortunately, some systems apparently have a prototype for pause() |
844 | in F<unistd.h>, but don't actually have the function in the library. |
845 | (Or maybe they do have it in a library we're not using.) |
846 | |
847 | Thus, the compiler sees something like |
848 | |
849 | extern int pause(void); |
850 | /* . . . */ |
851 | #define pause() sleep((32767<<16)+32767) |
852 | |
853 | and dies with an error message. (Some compilers don't mind this; |
854 | others apparently do.) |
855 | |
856 | To work around this, 5.003_03 and later have the following in perl.h: |
857 | |
858 | /* Some unistd.h's give a prototype for pause() even though |
859 | HAS_PAUSE ends up undefined. This causes the #define |
860 | below to be rejected by the compiler. Sigh. |
861 | */ |
862 | #ifdef HAS_PAUSE |
863 | # define Pause pause |
864 | #else |
865 | # define Pause() sleep((32767<<16)+32767) |
866 | #endif |
867 | |
868 | This works. |
869 | |
870 | The curious reader may wonder why I didn't do the following in |
871 | F<util.c> instead: |
872 | |
873 | #ifndef HAS_PAUSE |
874 | void pause() |
875 | { |
876 | sleep((32767<<16)+32767); |
877 | } |
878 | #endif |
879 | |
880 | That is, since the function is missing, just provide it. |
881 | Then things would probably be been alright, it would seem. |
882 | |
883 | Well, almost. It could be made to work. The problem arises from the |
884 | conflicting needs of dynamic loading and namespace protection. |
885 | |
886 | For dynamic loading to work on AIX (and VMS) we need to provide a list |
887 | of symbols to be exported. This is done by the script F<perl_exp.SH>, |
888 | which reads F<global.sym> and F<interp.sym>. Thus, the C<pause> |
889 | symbol would have to be added to F<global.sym> So far, so good. |
890 | |
891 | On the other hand, one of the goals of Perl5 is to make it easy to |
892 | either extend or embed perl and link it with other libraries. This |
893 | means we have to be careful to keep the visible namespace "clean". |
894 | That is, we don't want perl's global variables to conflict with |
895 | those in the other application library. Although this work is still |
896 | in progress, the way it is currently done is via the F<embed.h> file. |
897 | This file is built from the F<global.sym> and F<interp.sym> files, |
898 | since those files already list the globally visible symbols. If we |
899 | had added C<pause> to global.sym, then F<embed.h> would contain the |
900 | line |
901 | |
902 | #define pause Perl_pause |
903 | |
904 | and calls to C<pause> in the perl sources would now point to |
905 | C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable, |
906 | it will go looking for C<perl_pause>, which probably won't exist in any |
907 | of the standard libraries. Thus the build of perl will fail. |
908 | |
909 | Those systems where C<HAS_PAUSE> is not defined would be ok, however, |
910 | since they would get a C<Perl_pause> function in util.c. The rest of |
911 | the world would be in trouble. |
912 | |
913 | And yes, this scenario has happened. On SCO, the function C<chsize> |
914 | is available. (I think it's in F<-lx>, the Xenix compatibility |
915 | library.) Since the perl4 days (and possibly before), Perl has |
916 | included a C<chsize> function that gets called something akin to |
917 | |
918 | #ifndef HAS_CHSIZE |
919 | I32 chsize(fd, length) |
920 | /* . . . */ |
921 | #endif |
922 | |
923 | When 5.003 added |
924 | |
925 | #define chsize Perl_chsize |
926 | |
927 | to F<embed.h>, the compile started failing on SCO systems. |
928 | |
929 | The "fix" is to give the function a different name. The one |
930 | implemented in 5.003_05 isn't optimal, but here's what was done: |
931 | |
932 | #ifdef HAS_CHSIZE |
933 | # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */ |
934 | # undef my_chsize |
935 | # endif |
936 | # define my_chsize chsize |
937 | #endif |
938 | |
939 | My explanatory comment in patch 5.003_05 said: |
940 | |
941 | Undef and then re-define my_chsize from Perl_my_chsize to |
942 | just plain chsize if this system HAS_CHSIZE. This probably only |
943 | applies to SCO. This shows the perils of having internal |
944 | functions with the same name as external library functions :-). |
945 | |
946 | Now, we can safely put C<my_chsize> in F<global.sym>, export it, and |
947 | hide it with F<embed.h>. |
948 | |
949 | To be consistent with what I did for C<pause>, I probably should have |
950 | called the new function C<Chsize>, rather than C<my_chsize>. |
951 | However, the perl sources are quite inconsistent on this (Consider |
952 | New, Mymalloc, and Myremalloc, to name just a few.) |
953 | |
954 | There is a problem with this fix, however, in that C<Perl_chsize> |
955 | was available as a F<libperl.a> library function in 5.003, but it |
956 | isn't available any more (as of 5.003_07). This means that we've |
957 | broken binary compatibility. This is not good. |
958 | |
959 | =item Providing missing functions -- some ideas |
960 | |
961 | We currently don't have a standard way of handling such missing |
962 | function names. Right now, I'm effectively thinking aloud about a |
963 | solution. Some day, I'll try to formally propose a solution. |
964 | |
965 | Part of the problem is that we want to have some functions listed as |
966 | exported but not have their names mangled by embed.h or possibly |
967 | conflict with names in standard system headers. We actually already |
968 | have such a list at the end of F<perl_exp.SH> (though that list is |
969 | out-of-date): |
970 | |
971 | # extra globals not included above. |
972 | cat <<END >> perl.exp |
973 | perl_init_ext |
974 | perl_init_fold |
975 | perl_init_i18nl14n |
976 | perl_alloc |
977 | perl_construct |
978 | perl_destruct |
979 | perl_free |
980 | perl_parse |
981 | perl_run |
982 | perl_get_sv |
983 | perl_get_av |
984 | perl_get_hv |
985 | perl_get_cv |
986 | perl_call_argv |
987 | perl_call_pv |
988 | perl_call_method |
989 | perl_call_sv |
990 | perl_requirepv |
991 | safecalloc |
992 | safemalloc |
993 | saferealloc |
994 | safefree |
995 | |
996 | This still needs much thought, but I'm inclined to think that one |
997 | possible solution is to prefix all such functions with C<perl_> in the |
998 | source and list them along with the other C<perl_*> functions in |
999 | F<perl_exp.SH>. |
1000 | |
1001 | Thus, for C<chsize>, we'd do something like the following: |
1002 | |
1003 | /* in perl.h */ |
1004 | #ifdef HAS_CHSIZE |
1005 | # define perl_chsize chsize |
1006 | #endif |
1007 | |
1008 | then in some file (e.g. F<util.c> or F<doio.c>) do |
1009 | |
1010 | #ifndef HAS_CHSIZE |
1011 | I32 perl_chsize(fd, length) |
1012 | /* implement the function here . . . */ |
1013 | #endif |
1014 | |
1015 | Alternatively, we could just always use C<chsize> everywhere and move |
1016 | C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would |
1017 | probably be fine as long as our C<chsize> function agreed with all the |
1018 | C<chsize> function prototypes in the various systems we'll be using. |
1019 | As long as the prototypes in actual use don't vary that much, this is |
1020 | probably a good alternative. (As a counter-example, note how Configure |
1021 | and perl have to go through hoops to find and use get Malloc_t and |
1022 | Free_t for C<malloc> and C<free>.) |
1023 | |
1024 | At the moment, this latter option is what I tend to prefer. |
1025 | |
1026 | =item All the world's a VAX |
1027 | |
1028 | Sorry, showing my age:-). Still, all the world is not BSD 4.[34], |
1029 | SVR4, or POSIX. Be aware that SVR3-derived systems are still quite |
1030 | common (do you have any idea how many systems run SCO?) If you don't |
1031 | have a bunch of v7 manuals handy, the metaconfig units (by default |
1032 | installed in F</usr/local/lib/dist/U>) are a good resource to look at |
1033 | for portability. |
1034 | |
1035 | =back |
1036 | |
1037 | =head1 Miscellaneous Topics |
1038 | |
1039 | =head2 Autoconf |
1040 | |
1041 | Why does perl use a metaconfig-generated Configure script instead of an |
1042 | autoconf-generated configure script? |
1043 | |
1044 | Metaconfig and autoconf are two tools with very similar purposes. |
1045 | Metaconfig is actually the older of the two, and was originally written |
1046 | by Larry Wall, while autoconf is probably now used in a wider variety of |
1047 | packages. The autoconf info file discusses the history of autoconf and |
1048 | how it came to be. The curious reader is referred there for further |
1049 | information. |
1050 | |
1051 | Overall, both tools are quite good, I think, and the choice of which one |
1052 | to use could be argued either way. In March, 1994, when I was just |
1053 | starting to work on Configure support for Perl5, I considered both |
1054 | autoconf and metaconfig, and eventually decided to use metaconfig for the |
1055 | following reasons: |
1056 | |
1057 | =over 4 |
1058 | |
1059 | =item Compatibility with Perl4 |
1060 | |
1061 | Perl4 used metaconfig, so many of the #ifdef's were already set up for |
1062 | metaconfig. Of course metaconfig had evolved some since Perl4's days, |
1063 | but not so much that it posed any serious problems. |
1064 | |
1065 | =item Metaconfig worked for me |
1066 | |
1067 | My system at the time was Interactive 2.2, a SVR3.2/386 derivative that |
1068 | also had some POSIX support. Metaconfig-generated Configure scripts |
1069 | worked fine for me on that system. On the other hand, autoconf-generated |
1070 | scripts usually didn't. (They did come quite close, though, in some |
1071 | cases.) At the time, I actually fetched a large number of GNU packages |
1072 | and checked. Not a single one configured and compiled correctly |
1073 | out-of-the-box with the system's cc compiler. |
1074 | |
1075 | =item Configure can be interactive |
1076 | |
1077 | With both autoconf and metaconfig, if the script works, everything is |
1078 | fine. However, one of my main problems with autoconf-generated scripts |
1079 | was that if it guessed wrong about something, it could be B<very> hard to |
1080 | go back and fix it. For example, autoconf always insisted on passing the |
1081 | -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I |
1082 | wanted or needed for that package. There was no way short of editing the |
1083 | configure script to turn this off. You couldn't just edit the resulting |
1084 | Makefile at the end because the -Xp flag influenced a number of other |
1085 | configure tests. |
1086 | |
1087 | Metaconfig's Configure scripts, on the other hand, can be interactive. |
1088 | Thus if Configure is guessing things incorrectly, you can go back and fix |
1089 | them. This isn't as important now as it was when we were actively |
1090 | developing Configure support for new features such as dynamic loading, |
1091 | but it's still useful occasionally. |
1092 | |
1093 | =item GPL |
1094 | |
1095 | At the time, autoconf-generated scripts were covered under the GNU Public |
1096 | License, and hence weren't suitable for inclusion with Perl, which has a |
1097 | different licensing policy. (Autoconf's licensing has since changed.) |
1098 | |
1099 | =item Modularity |
1100 | |
1101 | Metaconfig builds up Configure from a collection of discrete pieces |
1102 | called "units". You can override the standard behavior by supplying your |
1103 | own unit. With autoconf, you have to patch the standard files instead. |
1104 | I find the metaconfig "unit" method easier to work with. Others |
1105 | may find metaconfig's units clumsy to work with. |
1106 | |
1107 | =back |
1108 | |
1109 | =head2 @INC search order |
1110 | |
1111 | By default, the list of perl library directories in @INC is the |
1112 | following: |
1113 | |
1114 | $archlib |
1115 | $privlib |
1116 | $sitearch |
1117 | $sitelib |
1118 | |
1119 | Specifically, on my Solaris/x86 system, I run |
1120 | B<sh Configure -Dprefix=/opt/perl> and I have the following |
1121 | directories: |
1122 | |
1123 | /opt/perl/lib/i86pc-solaris/5.00307 |
1124 | /opt/perl/lib |
1125 | /opt/perl/lib/site_perl/i86pc-solaris |
1126 | /opt/perl/lib/site_perl |
1127 | |
1128 | That is, perl's directories come first, followed by the site-specific |
1129 | directories. |
1130 | |
1131 | The site libraries come second to support the usage of extensions |
1132 | across perl versions. Read the relevant section in F<INSTALL> for |
1133 | more information. If we ever make $sitearch version-specific, this |
1134 | topic could be revisited. |
1135 | |
1136 | =head2 Why isn't there a directory to override Perl's library? |
1137 | |
1138 | Mainly because no one's gotten around to making one. Note that |
1139 | "making one" involves changing perl.c, Configure, config_h.SH (and |
1140 | associated files, see above), and I<documenting> it all in the |
1141 | INSTALL file. |
1142 | |
1143 | Apparently, most folks who want to override one of the standard library |
1144 | files simply do it by overwriting the standard library files. |
1145 | |
1146 | =head2 APPLLIB |
1147 | |
1148 | In the perl.c sources, you'll find an undocumented APPLLIB_EXP |
1149 | variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are |
1150 | documented in config_h.SH). Here's what APPLLIB_EXP is for, from |
1151 | a mail message from Larry: |
1152 | |
1153 | The main intent of APPLLIB_EXP is for folks who want to send out a |
1154 | version of Perl embedded in their product. They would set the symbol |
1155 | to be the name of the library containing the files needed to run or to |
1156 | support their particular application. This works at the "override" |
1157 | level to make sure they get their own versions of any library code that |
1158 | they absolutely must have configuration control over. |
1159 | |
1160 | As such, I don't see any conflict with a sysadmin using it for a |
1161 | override-ish sort of thing, when installing a generic Perl. It should |
1162 | probably have been named something to do with overriding though. Since |
1163 | it's undocumented we could still change it... :-) |
1164 | |
1165 | Given that it's already there, you can use it to override |
1166 | distribution modules. If you do |
1167 | |
1168 | sh Configure -Dccflags='-DAPPLLIB_EXP=/my/override' |
1169 | |
1170 | then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB. |
1171 | |
c4f23d77 |
1172 | =head2 Shared libperl.so location |
1173 | |
1174 | Why isn't the shared libperl.so installed in /usr/lib/ along |
1175 | with "all the other" shared libraries? Instead, it is installed |
1176 | in $archlib, which is typically something like |
1177 | |
1178 | /usr/local/lib/perl5/archname/5.00404 |
1179 | |
1180 | and is architecture- and version-specific. |
1181 | |
1182 | The basic reason why a shared libperl.so gets put in $archlib is so that |
1183 | you can have more than one version of perl on the system at the same time, |
1184 | and have each refer to its own libperl.so. |
1185 | |
1186 | Three examples might help. All of these work now; none would work if you |
1187 | put libperl.so in /usr/lib. |
1188 | |
1189 | =over |
1190 | |
1191 | =item 1. |
1192 | |
1193 | Suppose you want to have both threaded and non-threaded perl versions |
1194 | around. Configure will name both perl libraries "libperl.so" (so that |
1195 | you can link to them with -lperl). The perl binaries tell them apart |
1196 | by having looking in the appropriate $archlib directories. |
1197 | |
1198 | =item 2. |
1199 | |
1200 | Suppose you have perl5.004_04 installed and you want to try to compile |
1201 | it again, perhaps with different options or after applying a patch. |
1202 | If you already have libperl.so installed in /usr/lib/, then it may be |
1203 | either difficult or impossible to get ld.so to find the new libperl.so |
1204 | that you're trying to build. If, instead, libperl.so is tucked away in |
1205 | $archlib, then you can always just change $archlib in the current perl |
1206 | you're trying to build so that ld.so won't find your old libperl.so. |
1207 | (The INSTALL file suggests you do this when building a debugging perl.) |
1208 | |
1209 | =item 3. |
1210 | |
1211 | The shared perl library is not a "well-behaved" shared library with |
1212 | proper major and minor version numbers, so you can't necessarily |
1213 | have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose |
1214 | perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05 |
1215 | were to install /usr/lib/libperl.so.4.5. Now, when you try to run |
1216 | perl5.004_04, ld.so might try to load libperl.so.4.5, since it has |
1217 | the right "major version" number. If this works at all, it almost |
1218 | certainly defeats the reason for keeping perl5.004_04 around. Worse, |
1219 | with development subversions, you certaily can't guarantee that |
1220 | libperl.so.4.4 and libperl.so.4.55 will be compatible. |
1221 | |
1222 | Anyway, all this leads to quite obscure failures that are sure to drive |
1223 | casual users crazy. Even experienced users will get confused :-). Upon |
1224 | reflection, I'd say leave libperl.so in $archlib. |
1225 | |
1226 | =back |
1227 | |
aa689395 |
1228 | =head1 Upload Your Work to CPAN |
1229 | |
1230 | You can upload your work to CPAN if you have a CPAN id. Check out |
1231 | http://www.perl.com/CPAN/modules/04pause.html for information on |
1232 | _PAUSE_, the Perl Author's Upload Server. |
1233 | |
1234 | I typically upload both the patch file, e.g. F<perl5.004_08.pat.gz> |
1235 | and the full tar file, e.g. F<perl5.004_08.tar.gz>. |
1236 | |
1237 | If you want your patch to appear in the F<src/5.0/unsupported> |
1238 | directory on CPAN, send e-mail to the CPAN master librarian. (Check |
7b5757d1 |
1239 | out http://www.perl.com/CPAN/CPAN.html ). |
aa689395 |
1240 | |
1241 | =head1 Help Save the World |
1242 | |
1243 | You should definitely announce your patch on the perl5-porters list. |
1244 | You should also consider announcing your patch on |
1245 | comp.lang.perl.announce, though you should make it quite clear that a |
1246 | subversion is not a production release, and be prepared to deal with |
1247 | people who will not read your disclaimer. |
1248 | |
1249 | =head1 Todo |
1250 | |
1251 | Here, in no particular order, are some Configure and build-related |
1252 | items that merit consideration. This list isn't exhaustive, it's just |
1253 | what I came up with off the top of my head. |
1254 | |
1255 | =head2 Good ideas waiting for round tuits |
1256 | |
1257 | =over 4 |
1258 | |
1259 | =item installprefix |
1260 | |
1261 | I think we ought to support |
1262 | |
1263 | Configure -Dinstallprefix=/blah/blah |
1264 | |
1265 | Currently, we support B<-Dprefix=/blah/blah>, but the changing the install |
1266 | location has to be handled by something like the F<config.over> trick |
1267 | described in F<INSTALL>. AFS users also are treated specially. |
1268 | We should probably duplicate the metaconfig prefix stuff for an |
1269 | install prefix. |
1270 | |
c4f23d77 |
1271 | =item Configure -Dsrc=/blah/blah |
aa689395 |
1272 | |
1273 | We should be able to emulate B<configure --srcdir>. Tom Tromey |
1274 | tromey@creche.cygnus.com has submitted some patches to |
c4f23d77 |
1275 | the dist-users mailing list along these lines. They have been folded |
1276 | back into the main distribution, but various parts of the perl |
1277 | Configure/build/install process still assume src='.'. |
aa689395 |
1278 | |
1279 | =item Hint file fixes |
1280 | |
1281 | Various hint files work around Configure problems. We ought to fix |
1282 | Configure so that most of them aren't needed. |
1283 | |
1284 | =item Hint file information |
1285 | |
1286 | Some of the hint file information (particularly dynamic loading stuff) |
1287 | ought to be fed back into the main metaconfig distribution. |
1288 | |
c4f23d77 |
1289 | =item Catch GNU Libc "Stub" functions |
1290 | |
1291 | Some functions (such as lchown()) are present in libc, but are |
1292 | unimplmented. That is, they always fail and set errno=ENOSYS. |
1293 | |
1294 | Thomas Bushnell provided the following sample code and the explanation |
1295 | that follows: |
1296 | |
1297 | /* System header to define __stub macros and hopefully few prototypes, |
1298 | which can conflict with char FOO(); below. */ |
1299 | #include <assert.h> |
1300 | /* Override any gcc2 internal prototype to avoid an error. */ |
1301 | /* We use char because int might match the return type of a gcc2 |
1302 | builtin and then its argument prototype would still apply. */ |
1303 | char FOO(); |
1304 | |
1305 | int main() { |
1306 | |
1307 | /* The GNU C library defines this for functions which it implements |
1308 | to always fail with ENOSYS. Some functions are actually named |
1309 | something starting with __ and the normal name is an alias. */ |
1310 | #if defined (__stub_FOO) || defined (__stub___FOO) |
1311 | choke me |
1312 | #else |
1313 | FOO(); |
1314 | #endif |
1315 | |
1316 | ; return 0; } |
1317 | |
1318 | The choice of <assert.h> is essentially arbitrary. The GNU libc |
1319 | macros are found in <gnu/stubs.h>. You can include that file instead |
1320 | of <assert.h> (which itself includes <gnu/stubs.h>) if you test for |
1321 | its existence first. <assert.h> is assumed to exist on every system, |
1322 | which is why it's used here. Any GNU libc header file will include |
1323 | the stubs macros. If either __stub_NAME or __stub___NAME is defined, |
1324 | then the function doesn't actually exist. Tests using <assert.h> work |
1325 | on every system around. |
1326 | |
1327 | The declaration of FOO is there to override builtin prototypes for |
1328 | ANSI C functions. |
1329 | |
aa689395 |
1330 | =back |
1331 | |
1332 | =head2 Probably good ideas waiting for round tuits |
1333 | |
1334 | =over 4 |
1335 | |
1336 | =item GNU configure --options |
1337 | |
1338 | I've received sensible suggestions for --exec_prefix and other |
1339 | GNU configure --options. It's not always obvious exactly what is |
1340 | intended, but this merits investigation. |
1341 | |
1342 | =item make clean |
1343 | |
1344 | Currently, B<make clean> isn't all that useful, though |
1345 | B<make realclean> and B<make distclean> are. This needs a bit of |
1346 | thought and documentation before it gets cleaned up. |
1347 | |
1348 | =item Try gcc if cc fails |
1349 | |
1350 | Currently, we just give up. |
1351 | |
1352 | =item bypassing safe*alloc wrappers |
1353 | |
1354 | On some systems, it may be safe to call the system malloc directly |
1355 | without going through the util.c safe* layers. (Such systems would |
1356 | accept free(0), for example.) This might be a time-saver for systems |
1357 | that already have a good malloc. (Recent Linux libc's apparently have |
1358 | a nice malloc that is well-tuned for the system.) |
1359 | |
1360 | =back |
1361 | |
1362 | =head2 Vague possibilities |
1363 | |
1364 | =over 4 |
1365 | |
aa689395 |
1366 | =item MacPerl |
1367 | |
3e3baf6d |
1368 | Get some of the Macintosh stuff folded back into the main distribution. |
aa689395 |
1369 | |
1370 | =item gconvert replacement |
1371 | |
1372 | Maybe include a replacement function that doesn't lose data in rare |
1373 | cases of coercion between string and numerical values. |
1374 | |
aa689395 |
1375 | =item Improve makedepend |
1376 | |
1377 | The current makedepend process is clunky and annoyingly slow, but it |
1378 | works for most folks. Alas, it assumes that there is a filename |
1379 | $firstmakefile that the B<make> command will try to use before it uses |
1380 | F<Makefile>. Such may not be the case for all B<make> commands, |
1381 | particularly those on non-Unix systems. |
1382 | |
1383 | Probably some variant of the BSD F<.depend> file will be useful. |
1384 | We ought to check how other packages do this, if they do it at all. |
1385 | We could probably pre-generate the dependencies (with the exception of |
1386 | malloc.o, which could probably be determined at F<Makefile.SH> |
1387 | extraction time. |
1388 | |
1389 | =item GNU Makefile standard targets |
1390 | |
1391 | GNU software generally has standardized Makefile targets. Unless we |
1392 | have good reason to do otherwise, I see no reason not to support them. |
1393 | |
1394 | =item File locking |
1395 | |
1396 | Somehow, straighten out, document, and implement lockf(), flock(), |
1397 | and/or fcntl() file locking. It's a mess. |
1398 | |
1399 | =back |
1400 | |
fb73857a |
1401 | =head1 AUTHORS |
aa689395 |
1402 | |
fb73857a |
1403 | Original author: Andy Dougherty doughera@lafcol.lafayette.edu . |
1404 | Additions by Chip Salzenberg chip@perl.com and |
1405 | Tim Bunce Tim.Bunce@ig.co.uk . |
aa689395 |
1406 | |
1407 | All opinions expressed herein are those of the authorZ<>(s). |
1408 | |
1409 | =head1 LAST MODIFIED |
1410 | |
20f245af |
1411 | $Id: pumpkin.pod,v 1.22 1998/07/22 16:33:55 doughera Released $ |