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1 | =head1 NAME |
2 | |
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3 | Pumpkin - Notes on handling the Perl Patch Pumpkin And Porting Perl |
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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.cpan.org/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 | |
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46 | http://www.xray.mpe.mpg.de/mailing-lists/perl5-porters/ |
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47 | |
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48 | =head1 How are Perl Releases Numbered? |
49 | |
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50 | Beginning with v5.6.0, even versions will stand for maintenance releases |
51 | and odd versions for development releases, i.e., v5.6.x for maintenance |
52 | releases, and v5.7.x for development releases. Before v5.6.0, subversions |
53 | _01 through _49 were reserved for bug-fix maintenance releases, and |
54 | subversions _50 through _99 for unstable development versions. |
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55 | |
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56 | For example, in v5.6.1, the revision number is 5, the version is 6, |
57 | and 1 is the subversion. |
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58 | |
f5a32c7f |
59 | For compatibility with the older numbering scheme the composite floating |
60 | point version number continues to be available as the magic variable $], |
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61 | and amounts to C<$revision + $version/1000 + $subversion/100000>. This |
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62 | can still be used in comparisons. |
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63 | |
f5a32c7f |
64 | print "You've got an old perl\n" if $] < 5.005_03; |
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65 | |
f5a32c7f |
66 | In addition, the version is also available as a string in $^V. |
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67 | |
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68 | print "You've got a new perl\n" if $^V and $^V ge v5.6.0; |
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69 | |
f5a32c7f |
70 | You can also require particular version (or later) with: |
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71 | |
f5a32c7f |
72 | use 5.006; |
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73 | |
f5a32c7f |
74 | or using the new syntax available only from v5.6 onward: |
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75 | |
f5a32c7f |
76 | use v5.6.0; |
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77 | |
f5a32c7f |
78 | At some point in the future, we may need to decide what to call the |
79 | next big revision. In the .package file used by metaconfig to |
80 | generate Configure, there are two variables that might be relevant: |
81 | $baserev=5 and $package=perl5. |
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82 | |
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83 | Perl releases produced by the members of perl5-porters are usually |
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84 | available on CPAN in the F<src/5.0/maint> and F<src/5.0/devel> |
85 | directories. |
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86 | |
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87 | =head2 Maintenance and Development Subversions |
88 | |
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89 | The first rule of maintenance work is "First, do no harm." |
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90 | |
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91 | Trial releases of bug-fix maintenance releases are announced on |
92 | perl5-porters. Trial releases use the new subversion number (to avoid |
93 | testers installing it over the previous release) and include a 'local |
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94 | patch' entry in patchlevel.h. The distribution file contains the |
95 | string C<MAINT_TRIAL> to make clear that the file is not meant for |
96 | public consumption. |
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97 | |
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98 | In general, the names of official distribution files for the public |
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99 | always match the regular expression: |
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100 | |
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101 | ^perl\d+\.(\d+)\.\d+(-MAINT_TRIAL_\d+)\.tar\.gz$ |
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102 | |
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103 | C<$1> in the pattern is always an even number for maintenance |
104 | versions, and odd for developer releases. |
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105 | |
106 | In the past it has been observed that pumkings tend to invent new |
107 | naming conventions on the fly. If you are a pumpking, before you |
108 | invent a new name for any of the three types of perl distributions, |
109 | please inform the guys from the CPAN who are doing indexing and |
110 | provide the trees of symlinks and the like. They will have to know |
111 | I<in advance> what you decide. |
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112 | |
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113 | =head2 Why is it called the patch pumpkin? |
114 | |
115 | Chip Salzenberg gets credit for that, with a nod to his cow orker, |
116 | David Croy. We had passed around various names (baton, token, hot |
117 | potato) but none caught on. Then, Chip asked: |
118 | |
119 | [begin quote] |
120 | |
121 | Who has the patch pumpkin? |
122 | |
123 | To explain: David Croy once told me once that at a previous job, |
124 | there was one tape drive and multiple systems that used it for backups. |
125 | But instead of some high-tech exclusion software, they used a low-tech |
126 | method to prevent multiple simultaneous backups: a stuffed pumpkin. |
127 | No one was allowed to make backups unless they had the "backup pumpkin". |
128 | |
129 | [end quote] |
130 | |
131 | The name has stuck. |
132 | |
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133 | =head1 Philosophical Issues in Patching and Porting Perl |
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134 | |
135 | There are no absolute rules, but there are some general guidelines I |
136 | have tried to follow as I apply patches to the perl sources. |
137 | (This section is still under construction.) |
138 | |
139 | =head2 Solve problems as generally as possible |
140 | |
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141 | Never implement a specific restricted solution to a problem when you |
142 | can solve the same problem in a more general, flexible way. |
143 | |
144 | For example, for dynamic loading to work on some SVR4 systems, we had |
145 | to build a shared libperl.so library. In order to build "FAT" binaries |
146 | on NeXT 4.0 systems, we had to build a special libperl library. Rather |
147 | than continuing to build a contorted nest of special cases, I |
148 | generalized the process of building libperl so that NeXT and SVR4 users |
149 | could still get their work done, but others could build a shared |
150 | libperl if they wanted to as well. |
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151 | |
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152 | Contain your changes carefully. Assume nothing about other operating |
153 | systems, not even closely related ones. Your changes must not affect |
154 | other platforms. |
155 | |
156 | Spy shamelessly on how similar patching or porting issues have been |
157 | settled elsewhere. |
158 | |
159 | If feasible, try to keep filenames 8.3-compliant to humor those poor |
160 | souls that get joy from running Perl under such dire limitations. |
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161 | There's a script, check83.pl, for keeping your nose 8.3-clean. |
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162 | |
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163 | =head2 Seek consensus on major changes |
164 | |
165 | If you are making big changes, don't do it in secret. Discuss the |
166 | ideas in advance on perl5-porters. |
167 | |
168 | =head2 Keep the documentation up-to-date |
169 | |
170 | If your changes may affect how users use perl, then check to be sure |
171 | that the documentation is in sync with your changes. Be sure to |
172 | check all the files F<pod/*.pod> and also the F<INSTALL> document. |
173 | |
174 | Consider writing the appropriate documentation first and then |
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175 | implementing your change to correspond to the documentation. |
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176 | |
177 | =head2 Avoid machine-specific #ifdef's |
178 | |
179 | To the extent reasonable, try to avoid machine-specific #ifdef's in |
180 | the sources. Instead, use feature-specific #ifdef's. The reason is |
181 | that the machine-specific #ifdef's may not be valid across major |
182 | releases of the operating system. Further, the feature-specific tests |
183 | may help out folks on another platform who have the same problem. |
184 | |
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185 | =head2 Machine-specific files |
186 | |
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187 | =over 4 |
188 | |
189 | =item source code |
190 | |
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191 | If you have many machine-specific #defines or #includes, consider |
192 | creating an "osish.h" (os2ish.h, vmsish.h, and so on) and including |
193 | that in perl.h. If you have several machine-specific files (function |
194 | emulations, function stubs, build utility wrappers) you may create a |
195 | separate subdirectory (djgpp, win32) and put the files in there. |
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196 | Remember to update C<MANIFEST> when you add files. |
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197 | |
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198 | If your system supports dynamic loading but none of the existing |
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199 | methods at F<ext/DynaLoader/dl_*.xs> work for you, you must write |
200 | a new one. Study the existing ones to see what kind of interface |
201 | you must supply. |
202 | |
203 | =item build hints |
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204 | |
205 | There are two kinds of hints: hints for building Perl and hints for |
206 | extensions. The former live in the C<hints> subdirectory, the latter |
207 | in C<ext/*/hints> subdirectories. |
208 | |
209 | The top level hints are Bourne-shell scripts that set, modify and |
210 | unset appropriate Configure variables, based on the Configure command |
211 | line options and possibly existing config.sh and Policy.sh files from |
212 | previous Configure runs. |
213 | |
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214 | The extension hints are written in Perl (by the time they are used |
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215 | miniperl has been built) and control the building of their respective |
216 | extensions. They can be used to for example manipulate compilation |
217 | and linking flags. |
218 | |
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219 | =item build and installation Makefiles, scripts, and so forth |
220 | |
221 | Sometimes you will also need to tweak the Perl build and installation |
222 | procedure itself, like for example F<Makefile.SH> and F<installperl>. |
223 | Tread very carefully, even more than usual. Contain your changes |
224 | with utmost care. |
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225 | |
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226 | =item test suite |
227 | |
228 | Many of the tests in C<t> subdirectory assume machine-specific things |
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229 | like existence of certain functions, something about filesystem |
230 | semantics, certain external utilities and their error messages. Use |
231 | the C<$^O> and the C<Config> module (which contains the results of the |
232 | Configure run, in effect the C<config.sh> converted to Perl) to either |
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233 | skip (preferably not) or customize (preferable) the tests for your |
234 | platform. |
235 | |
236 | =item modules |
237 | |
238 | Certain standard modules may need updating if your operating system |
239 | sports for example a native filesystem naming. You may want to update |
240 | some or all of the modules File::Basename, File::Spec, File::Path, and |
241 | File::Copy to become aware of your native filesystem syntax and |
242 | peculiarities. |
243 | |
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244 | Remember to have a $VERSION in the modules. You can use the |
245 | Porting/checkVERSION.pl script for checking this. |
246 | |
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247 | =item documentation |
248 | |
249 | If your operating system comes from outside UNIX you almost certainly |
250 | will have differences in the available operating system functionality |
251 | (missing system calls, different semantics, whatever). Please |
252 | document these at F<pod/perlport.pod>. If your operating system is |
253 | the first B<not> to have a system call also update the list of |
254 | "portability-bewares" at the beginning of F<pod/perlfunc.pod>. |
255 | |
256 | A file called F<README.youros> at the top level that explains things |
257 | like how to install perl at this platform, where to get any possibly |
258 | required additional software, and for example what test suite errors |
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259 | to expect, is nice too. Such files are in the process of being written |
260 | in pod format and will eventually be renamed F<INSTALL.youros>. |
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261 | |
262 | You may also want to write a separate F<.pod> file for your operating |
263 | system to tell about existing mailing lists, os-specific modules, |
264 | documentation, whatever. Please name these along the lines of |
265 | F<perl>I<youros>.pod. [unfinished: where to put this file (the pod/ |
266 | subdirectory, of course: but more importantly, which/what index files |
267 | should be updated?)] |
268 | |
269 | =back |
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270 | |
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271 | =head2 Allow for lots of testing |
272 | |
273 | We should never release a main version without testing it as a |
274 | subversion first. |
275 | |
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276 | =head2 Test popular applications and modules. |
277 | |
278 | We should never release a main version without testing whether or not |
279 | it breaks various popular modules and applications. A partial list of |
280 | such things would include majordomo, metaconfig, apache, Tk, CGI, |
281 | libnet, and libwww, to name just a few. Of course it's quite possible |
282 | that some of those things will be just plain broken and need to be fixed, |
283 | but, in general, we ought to try to avoid breaking widely-installed |
284 | things. |
285 | |
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286 | =head2 Automated generation of derivative files |
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287 | |
288 | The F<embed.h>, F<keywords.h>, F<opcode.h>, and F<perltoc.pod> files |
289 | are all automatically generated by perl scripts. In general, don't |
290 | patch these directly; patch the data files instead. |
291 | |
292 | F<Configure> and F<config_h.SH> are also automatically generated by |
293 | B<metaconfig>. In general, you should patch the metaconfig units |
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294 | instead of patching these files directly. However, very minor changes |
295 | to F<Configure> may be made in between major sync-ups with the |
296 | metaconfig units, which tends to be complicated operations. But be |
297 | careful, this can quickly spiral out of control. Running metaconfig |
298 | is not really hard. |
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299 | |
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300 | Also F<Makefile> is automatically produced from F<Makefile.SH>. |
301 | In general, look out for all F<*.SH> files. |
302 | |
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303 | Finally, the sample files in the F<Porting/> subdirectory are |
304 | generated automatically by the script F<U/mksample> included |
305 | with the metaconfig units. See L<"run metaconfig"> below for |
306 | information on obtaining the metaconfig units. |
307 | |
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308 | =head1 How to Make a Distribution |
309 | |
310 | There really ought to be a 'make dist' target, but there isn't. |
311 | The 'dist' suite of tools also contains a number of tools that I haven't |
312 | learned how to use yet. Some of them may make this all a bit easier. |
313 | |
314 | Here are the steps I go through to prepare a patch & distribution. |
315 | |
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316 | Lots of it could doubtless be automated but isn't. The Porting/makerel |
317 | (make release) perl script does now help automate some parts of it. |
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318 | |
319 | =head2 Announce your intentions |
320 | |
321 | First, you should volunteer out loud to take the patch pumpkin. It's |
322 | generally counter-productive to have multiple people working in secret |
323 | on the same thing. |
324 | |
325 | At the same time, announce what you plan to do with the patch pumpkin, |
326 | to allow folks a chance to object or suggest alternatives, or do it for |
327 | you. Naturally, the patch pumpkin holder ought to incorporate various |
328 | bug fixes and documentation improvements that are posted while he or |
329 | she has the pumpkin, but there might also be larger issues at stake. |
330 | |
331 | One of the precepts of the subversion idea is that we shouldn't give |
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332 | the patch pumpkin to anyone unless we have some idea what he or she |
333 | is going to do with it. |
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334 | |
335 | =head2 refresh pod/perltoc.pod |
336 | |
337 | Presumably, you have done a full C<make> in your working source |
338 | directory. Before you C<make spotless> (if you do), and if you have |
339 | changed any documentation in any module or pod file, change to the |
340 | F<pod> directory and run C<make toc>. |
341 | |
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342 | =head2 run installhtml to check the validity of the pod files |
343 | |
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344 | =head2 update patchlevel.h |
345 | |
346 | Don't be shy about using the subversion number, even for a relatively |
347 | modest patch. We've never even come close to using all 99 subversions, |
348 | and it's better to have a distinctive number for your patch. If you |
349 | need feedback on your patch, go ahead and issue it and promise to |
350 | incorporate that feedback quickly (e.g. within 1 week) and send out a |
351 | second patch. |
352 | |
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353 | If you update the subversion number, you may need to change the version |
354 | number near the top of the F<Changes> file. |
355 | |
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356 | =head2 run metaconfig |
357 | |
358 | If you need to make changes to Configure or config_h.SH, it may be best to |
359 | change the appropriate metaconfig units instead, and regenerate Configure. |
360 | |
361 | metaconfig -m |
362 | |
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363 | will regenerate Configure and config_h.SH. Much more information |
364 | on obtaining and running metaconfig is in the F<U/README> file |
365 | that comes with Perl's metaconfig units. Perl's metaconfig units |
366 | should be available on CPAN. A set of units that will work with |
367 | perl5.005 is in the file F<mc_units-5.005_00-01.tar.gz> under |
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368 | http://www.cpan.org/authors/id/ANDYD/ . The mc_units tar file |
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369 | should be unpacked in your main perl source directory. Note: those |
370 | units were for use with 5.005. There may have been changes since then. |
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371 | Check for later versions or contact perl5-porters@perl.org to obtain a |
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372 | pointer to the current version. |
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373 | |
374 | Alternatively, do consider if the F<*ish.h> files might be a better |
375 | place for your changes. |
376 | |
377 | =head2 MANIFEST |
378 | |
379 | Make sure the MANIFEST is up-to-date. You can use dist's B<manicheck> |
380 | program for this. You can also use |
381 | |
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382 | perl -w -MExtUtils::Manifest=fullcheck -e fullcheck |
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383 | |
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384 | Both commands will also list extra files in the directory that are not |
385 | listed in MANIFEST. |
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386 | |
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387 | The MANIFEST is normally sorted. |
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388 | |
389 | If you are using metaconfig to regenerate Configure, then you should note |
390 | that metaconfig actually uses MANIFEST.new, so you want to be sure |
391 | MANIFEST.new is up-to-date too. I haven't found the MANIFEST/MANIFEST.new |
392 | distinction particularly useful, but that's probably because I still haven't |
393 | learned how to use the full suite of tools in the dist distribution. |
394 | |
395 | =head2 Check permissions |
396 | |
397 | All the tests in the t/ directory ought to be executable. The |
398 | main makefile used to do a 'chmod t/*/*.t', but that resulted in |
399 | a self-modifying distribution--something some users would strongly |
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400 | prefer to avoid. The F<t/TEST> script will check for this |
401 | and do the chmod if needed, but the tests still ought to be |
402 | executable. |
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403 | |
404 | In all, the following files should probably be executable: |
405 | |
406 | Configure |
407 | configpm |
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408 | configure.gnu |
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409 | embed.pl |
410 | installperl |
411 | installman |
412 | keywords.pl |
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413 | myconfig |
414 | opcode.pl |
415 | perly.fixer |
416 | t/TEST |
417 | t/*/*.t |
418 | *.SH |
419 | vms/ext/Stdio/test.pl |
420 | vms/ext/filespec.t |
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421 | x2p/*.SH |
422 | |
423 | Other things ought to be readable, at least :-). |
424 | |
425 | Probably, the permissions for the files could be encoded in MANIFEST |
426 | somehow, but I'm reluctant to change MANIFEST itself because that |
427 | could break old scripts that use MANIFEST. |
428 | |
429 | I seem to recall that some SVR3 systems kept some sort of file that listed |
430 | permissions for system files; something like that might be appropriate. |
431 | |
432 | =head2 Run Configure |
433 | |
434 | This will build a config.sh and config.h. You can skip this if you haven't |
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435 | changed Configure or config_h.SH at all. I use the following command |
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436 | |
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437 | sh Configure -Dprefix=/opt/perl -Doptimize=-O -Dusethreads \ |
438 | -Dcf_by='yourname' \ |
439 | -Dcf_email='yourname@yourhost.yourplace.com' \ |
440 | -Dperladmin='yourname@yourhost.yourplace.com' \ |
441 | -Dmydomain='.yourplace.com' \ |
442 | -Dmyhostname='yourhost' \ |
443 | -des |
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444 | |
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445 | =head2 Update Porting/config.sh and Porting/config_H |
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446 | |
693762b4 |
447 | [XXX |
448 | This section needs revision. We're currently working on easing |
449 | the task of keeping the vms, win32, and plan9 config.sh info |
450 | up-to-date. The plan is to use keep up-to-date 'canned' config.sh |
451 | files in the appropriate subdirectories and then generate 'canned' |
452 | config.h files for vms, win32, etc. from the generic config.sh file. |
453 | This is to ease maintenance. When Configure gets updated, the parts |
454 | sometimes get scrambled around, and the changes in config_H can |
455 | sometimes be very hard to follow. config.sh, on the other hand, can |
456 | safely be sorted, so it's easy to track (typically very small) changes |
457 | to config.sh and then propoagate them to a canned 'config.h' by any |
458 | number of means, including a perl script in win32/ or carrying |
459 | config.sh and config_h.SH to a Unix system and running sh |
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460 | config_h.SH.) Vms uses configure.com to generate its own config.sh |
461 | and config.h. If you want to add a new variable to config.sh check |
462 | with vms folk how to add it to configure.com too. |
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463 | XXX] |
464 | |
465 | The Porting/config.sh and Porting/config_H files are provided to |
466 | help those folks who can't run Configure. It is important to keep |
467 | them up-to-date. If you have changed config_h.SH, those changes must |
468 | be reflected in config_H as well. (The name config_H was chosen to |
469 | distinguish the file from config.h even on case-insensitive file systems.) |
470 | Simply edit the existing config_H file; keep the first few explanatory |
471 | lines and then copy your new config.h below. |
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472 | |
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473 | It may also be necessary to update win32/config.?c, and |
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474 | plan9/config.plan9, though you should be quite careful in doing so if |
475 | you are not familiar with those systems. You might want to issue your |
476 | patch with a promise to quickly issue a follow-up that handles those |
477 | directories. |
478 | |
479 | =head2 make run_byacc |
480 | |
481 | If you have byacc-1.8.2 (available from CPAN), and if there have been |
482 | changes to F<perly.y>, you can regenerate the F<perly.c> file. The |
483 | run_byacc makefile target does this by running byacc and then applying |
484 | some patches so that byacc dynamically allocates space, rather than |
485 | having fixed limits. This patch is handled by the F<perly.fixer> |
486 | script. Depending on the nature of the changes to F<perly.y>, you may |
487 | or may not have to hand-edit the patch to apply correctly. If you do, |
488 | you should include the edited patch in the new distribution. If you |
489 | have byacc-1.9, the patch won't apply cleanly. Changes to the printf |
490 | output statements mean the patch won't apply cleanly. Long ago I |
491 | started to fix F<perly.fixer> to detect this, but I never completed the |
492 | task. |
493 | |
76ba0908 |
494 | If C<perly.c> or C<perly.h> changes, make sure you run C<perl vms/vms_yfix.pl> |
495 | to update the corresponding VMS files. This could be taken care of by |
496 | the regen_all target in the Unix Makefile. See also |
497 | L<VMS-specific updates>. |
ebb99254 |
498 | |
aa689395 |
499 | Some additional notes from Larry on this: |
500 | |
e262e9be |
501 | Don't forget to regenerate perly_c.diff. |
aa689395 |
502 | |
7b5757d1 |
503 | byacc -d perly.y |
aa689395 |
504 | mv y.tab.c perly.c |
e262e9be |
505 | patch perly.c <perly_c.diff |
aa689395 |
506 | # manually apply any failed hunks |
eade9b71 |
507 | diff -c perly.c.orig perly.c >perly_c.diff |
aa689395 |
508 | |
509 | One chunk of lines that often fails begins with |
510 | |
511 | #line 29 "perly.y" |
512 | |
513 | and ends one line before |
514 | |
515 | #define YYERRCODE 256 |
516 | |
517 | This only happens when you add or remove a token type. I suppose this |
518 | could be automated, but it doesn't happen very often nowadays. |
519 | |
520 | Larry |
521 | |
76ba0908 |
522 | =head2 make regen_all |
523 | |
524 | This target takes care of the PERLYVMS, regen_headers, and regen_pods |
525 | targets. |
526 | |
aa689395 |
527 | =head2 make regen_headers |
528 | |
529 | The F<embed.h>, F<keywords.h>, and F<opcode.h> files are all automatically |
530 | generated by perl scripts. Since the user isn't guaranteed to have a |
531 | working perl, we can't require the user to generate them. Hence you have |
532 | to, if you're making a distribution. |
533 | |
534 | I used to include rules like the following in the makefile: |
535 | |
536 | # The following three header files are generated automatically |
537 | # The correct versions should be already supplied with the perl kit, |
538 | # in case you don't have perl or 'sh' available. |
539 | # The - is to ignore error return codes in case you have the source |
540 | # installed read-only or you don't have perl yet. |
541 | keywords.h: keywords.pl |
542 | @echo "Don't worry if this fails." |
543 | - perl keywords.pl |
544 | |
545 | |
7b5757d1 |
546 | However, I got B<lots> of mail consisting of people worrying because the |
aa689395 |
547 | command failed. I eventually decided that I would save myself time |
548 | and effort by manually running C<make regen_headers> myself rather |
549 | than answering all the questions and complaints about the failing |
550 | command. |
551 | |
76ba0908 |
552 | =head2 make regen_pods |
553 | |
554 | Will run `make regen_pods` in the pod directory for indexing. |
555 | |
3e3baf6d |
556 | =head2 global.sym, interp.sym and perlio.sym |
aa689395 |
557 | |
558 | Make sure these files are up-to-date. Read the comments in these |
559 | files and in perl_exp.SH to see what to do. |
560 | |
561 | =head2 Binary compatibility |
562 | |
563 | If you do change F<global.sym> or F<interp.sym>, think carefully about |
564 | what you are doing. To the extent reasonable, we'd like to maintain |
76ba0908 |
565 | source and binary compatibility with older releases of perl. That way, |
aa689395 |
566 | extensions built under one version of perl will continue to work with |
567 | new versions of perl. |
568 | |
569 | Of course, some incompatible changes may well be necessary. I'm just |
570 | suggesting that we not make any such changes without thinking carefully |
571 | about them first. If possible, we should provide |
572 | backwards-compatibility stubs. There's a lot of XS code out there. |
573 | Let's not force people to keep changing it. |
574 | |
575 | =head2 Changes |
576 | |
577 | Be sure to update the F<Changes> file. Try to include both an overall |
578 | summary as well as detailed descriptions of the changes. Your |
3e3baf6d |
579 | audience will include other developers and users, so describe |
aa689395 |
580 | user-visible changes (if any) in terms they will understand, not in |
581 | code like "initialize foo variable in bar function". |
582 | |
583 | There are differing opinions on whether the detailed descriptions |
584 | ought to go in the Changes file or whether they ought to be available |
585 | separately in the patch file (or both). There is no disagreement that |
586 | detailed descriptions ought to be easily available somewhere. |
587 | |
05ff1fbb |
588 | If you update the subversion number in F<patchlevel.h>, you may need |
589 | to change the version number near the top of the F<Changes> file. |
590 | |
2a26e2f1 |
591 | =head2 Todo |
592 | |
593 | The F<Todo> file contains a roughly-catgorized unordered list of |
594 | aspects of Perl that could use enhancement, features that could be |
595 | added, areas that could be cleaned up, and so on. During your term as |
596 | pumpkin-holder, you will probably address some of these issues, and |
597 | perhaps identify others which, while you decide not to address them |
598 | this time around, may be tackled in the future. Update the file |
599 | reflect the situation as it stands when you hand over the pumpkin. |
600 | |
601 | You might like, early in your pumpkin-holding career, to see if you |
602 | can find champions for partiticular issues on the to-do list: an issue |
603 | owned is an issue more likely to be resolved. |
604 | |
c4f23d77 |
605 | There are also some more porting-specific L<Todo> items later in this |
606 | file. |
607 | |
aa689395 |
608 | =head2 OS/2-specific updates |
609 | |
610 | In the os2 directory is F<diff.configure>, a set of OS/2-specific |
611 | diffs against B<Configure>. If you make changes to Configure, you may |
612 | want to consider regenerating this diff file to save trouble for the |
613 | OS/2 maintainer. |
614 | |
7b5757d1 |
615 | You can also consider the OS/2 diffs as reminders of portability |
616 | things that need to be fixed in Configure. |
617 | |
aa689395 |
618 | =head2 VMS-specific updates |
619 | |
ebb99254 |
620 | If you have changed F<perly.y> or F<perly.c>, then you most probably want |
76ba0908 |
621 | to update F<vms/perly_{h,c}.vms> by running C<perl vms/vms_yfix.pl>, or |
622 | by running `make regen_all` which will run that script for you. |
aa689395 |
623 | |
76ba0908 |
624 | The Perl revision number appears as "perl5" in configure.com. |
625 | It is courteous to update that if necessary. |
aa689395 |
626 | |
627 | =head2 Making the new distribution |
628 | |
629 | Suppose, for example, that you want to make version 5.004_08. Then you can |
630 | do something like the following |
631 | |
632 | mkdir ../perl5.004_08 |
633 | awk '{print $1}' MANIFEST | cpio -pdm ../perl5.004_08 |
634 | cd ../ |
635 | tar cf perl5.004_08.tar perl5.004_08 |
636 | gzip --best perl5.004_08.tar |
637 | |
3e3baf6d |
638 | These steps, with extra checks, are automated by the Porting/makerel |
639 | script. |
640 | |
aa689395 |
641 | =head2 Making a new patch |
642 | |
643 | I find the F<makepatch> utility quite handy for making patches. |
644 | You can obtain it from any CPAN archive under |
a93751fa |
645 | http://www.cpan.org/authors/Johan_Vromans/ . There are a couple |
3e3baf6d |
646 | of differences between my version and the standard one. I have mine do |
647 | a |
aa689395 |
648 | |
649 | # Print a reassuring "End of Patch" note so people won't |
650 | # wonder if their mailer truncated patches. |
651 | print "\n\nEnd of Patch.\n"; |
652 | |
3e3baf6d |
653 | at the end. That's because I used to get questions from people asking |
654 | if their mail was truncated. |
655 | |
656 | It also writes Index: lines which include the new directory prefix |
657 | (change Index: print, approx line 294 or 310 depending on the version, |
658 | to read: print PATCH ("Index: $newdir$new\n");). That helps patches |
659 | work with more POSIX conformant patch programs. |
aa689395 |
660 | |
661 | Here's how I generate a new patch. I'll use the hypothetical |
662 | 5.004_07 to 5.004_08 patch as an example. |
663 | |
664 | # unpack perl5.004_07/ |
665 | gzip -d -c perl5.004_07.tar.gz | tar -xof - |
666 | # unpack perl5.004_08/ |
667 | gzip -d -c perl5.004_08.tar.gz | tar -xof - |
668 | makepatch perl5.004_07 perl5.004_08 > perl5.004_08.pat |
669 | |
670 | Makepatch will automatically generate appropriate B<rm> commands to remove |
671 | deleted files. Unfortunately, it will not correctly set permissions |
672 | for newly created files, so you may have to do so manually. For example, |
673 | patch 5.003_04 created a new test F<t/op/gv.t> which needs to be executable, |
674 | so at the top of the patch, I inserted the following lines: |
675 | |
676 | # Make a new test |
677 | touch t/op/gv.t |
678 | chmod +x t/opt/gv.t |
679 | |
680 | Now, of course, my patch is now wrong because makepatch didn't know I |
681 | was going to do that command, and it patched against /dev/null. |
682 | |
683 | So, what I do is sort out all such shell commands that need to be in the |
684 | patch (including possible mv-ing of files, if needed) and put that in the |
685 | shell commands at the top of the patch. Next, I delete all the patch parts |
686 | of perl5.004_08.pat, leaving just the shell commands. Then, I do the |
687 | following: |
688 | |
7b5757d1 |
689 | cd perl5.004_07 |
690 | sh ../perl5.004_08.pat |
aa689395 |
691 | cd .. |
7b5757d1 |
692 | makepatch perl5.004_07 perl5.004_08 >> perl5.004_08.pat |
aa689395 |
693 | |
694 | (Note the append to preserve my shell commands.) |
695 | Now, my patch will line up with what the end users are going to do. |
696 | |
697 | =head2 Testing your patch |
698 | |
699 | It seems obvious, but be sure to test your patch. That is, verify that |
700 | it produces exactly the same thing as your full distribution. |
701 | |
7b5757d1 |
702 | rm -rf perl5.004_07 |
703 | gzip -d -c perl5.004_07.tar.gz | tar -xf - |
704 | cd perl5.004_07 |
705 | sh ../perl5.004_08.pat |
706 | patch -p1 -N < ../perl5.004_08.pat |
aa689395 |
707 | cd .. |
7b5757d1 |
708 | gdiff -r perl5.004_07 perl5.004_08 |
aa689395 |
709 | |
710 | where B<gdiff> is GNU diff. Other diff's may also do recursive checking. |
711 | |
712 | =head2 More testing |
713 | |
714 | Again, it's obvious, but you should test your new version as widely as you |
715 | can. You can be sure you'll hear about it quickly if your version doesn't |
716 | work on both ANSI and pre-ANSI compilers, and on common systems such as |
717 | SunOS 4.1.[34], Solaris, and Linux. |
718 | |
719 | If your changes include conditional code, try to test the different |
720 | branches as thoroughly as you can. For example, if your system |
721 | supports dynamic loading, you can also test static loading with |
722 | |
723 | sh Configure -Uusedl |
724 | |
725 | You can also hand-tweak your config.h to try out different #ifdef |
726 | branches. |
727 | |
d2560b70 |
728 | =head2 Other tests |
729 | |
730 | =over 4 |
731 | |
732 | =item CHECK_FORMAT |
733 | |
734 | To test the correct use of printf-style arguments, C<Configure> with |
735 | S<-Dccflags='-DCHECK_FORMAT -Wformat'> and run C<make>. The compiler |
736 | will produce warning of incorrect use of format arguments. CHECK_FORMAT |
737 | changes perl-defined formats to common formats, so DO NOT USE the executable |
738 | produced by this process. |
739 | |
740 | A more accurate approach is the following commands: |
741 | |
b3fe4827 |
742 | =over 4 |
743 | |
744 | =item * |
745 | |
746 | build miniperl with -DCHECK_FORMAT |
747 | |
748 | make clean |
749 | make miniperl OPTIMIZE=-DCHECK_FORMAT >& mini.log |
750 | |
751 | =item * |
752 | |
753 | build a clean miniperl, |
754 | and build everything else from that with -DCHECK_FORMAT |
755 | |
d2560b70 |
756 | make clean |
b3fe4827 |
757 | make miniperl |
436c6dd3 |
758 | make all OPTIMIZE='-DCHECK_FORMAT -Wformat' >& make.log |
b3fe4827 |
759 | |
760 | =item * |
761 | |
762 | clean up, and print warnings from the log files |
763 | |
d2560b70 |
764 | make clean |
b3fe4827 |
765 | perl -nwe 'print if /^\S+:/ and not /^make\b/' \ |
766 | mini.log make.log |
767 | |
768 | =back |
d2560b70 |
769 | |
770 | (-Wformat support by Robin Barker.) |
771 | |
93189314 |
772 | =item gcc -ansi -pedantic |
773 | |
774 | Configure -Dgccansipedantic [ -Dcc=gcc ] will enable (via the cflags script, |
775 | not $Config{ccflags}) the gcc strict ANSI C flags -ansi and -pedantic for |
776 | the compilation of the core files on platforms where it knows it can |
777 | do so (like Linux, see cflags.SH for the full list), and on some |
778 | platforms only one (Solaris can do only -pedantic, not -ansi). |
779 | The flag -DPERL_GCC_PEDANTIC also gets added, since gcc does not add |
780 | any internal cpp flag to signify that -pedantic is being used, as it |
781 | does for -ansi (__STRICT_ANSI__). |
782 | |
a0426075 |
783 | Note that the -ansi and -pedantic are enabled only for version 3 (and |
784 | later) of gcc, since even gcc version 2.95.4 finds lots of seemingly |
785 | false "value computed not used" errors from Perl. |
786 | |
93189314 |
787 | The -ansi and -pedantic are useful in catching at least the following |
788 | nonportable practices: |
789 | |
790 | =over 4 |
791 | |
792 | =item * |
793 | |
794 | gcc-specific extensions |
795 | |
796 | =item * |
797 | |
798 | lvalue casts |
799 | |
800 | =item * |
801 | |
802 | // C++ comments |
803 | |
804 | =item * |
805 | |
806 | enum trailing commas |
807 | |
808 | =back |
809 | |
810 | The -Dgccansipedantic should be used only when cleaning up the code, |
811 | not for production builds, since otherwise gcc cannot inline certain |
812 | things. |
813 | |
d2560b70 |
814 | =back |
815 | |
d33b2eba |
816 | =head1 Running Purify |
f5a32c7f |
817 | |
818 | Purify is a commercial tool that is helpful in identifying memory |
819 | overruns, wild pointers, memory leaks and other such badness. Perl |
820 | must be compiled in a specific way for optimal testing with Purify. |
821 | |
822 | Use the following commands to test perl with Purify: |
823 | |
824 | sh Configure -des -Doptimize=-g -Uusemymalloc -Dusemultiplicity \ |
825 | -Accflags=-DPURIFY |
826 | setenv PURIFYOPTIONS "-chain-length=25" |
827 | make all pureperl |
828 | cd t |
829 | ln -s ../pureperl perl |
365a6279 |
830 | setenv PERL_DESTRUCT_LEVEL 2 |
f5a32c7f |
831 | ./perl TEST |
832 | |
833 | Disabling Perl's malloc allows Purify to monitor allocations and leaks |
834 | more closely; using Perl's malloc will make Purify report most leaks |
835 | in the "potential" leaks category. Enabling the multiplicity option |
836 | allows perl to clean up thoroughly when the interpreter shuts down, which |
837 | reduces the number of bogus leak reports from Purify. The -DPURIFY |
838 | enables any Purify-specific debugging code in the sources. |
839 | |
840 | Purify outputs messages in "Viewer" windows by default. If you don't have |
841 | a windowing environment or if you simply want the Purify output to |
842 | unobtrusively go to a log file instead of to the interactive window, |
843 | use the following options instead: |
844 | |
845 | setenv PURIFYOPTIONS "-chain-length=25 -windows=no -log-file=perl.log \ |
846 | -append-logfile=yes" |
847 | |
848 | The only currently known leaks happen when there are compile-time errors |
849 | within eval or require. (Fixing these is non-trivial, unfortunately, but |
850 | they must be fixed eventually.) |
851 | |
aa689395 |
852 | =head1 Common Gotcha's |
853 | |
854 | =over 4 |
855 | |
856 | =item #elif |
857 | |
858 | The '#elif' preprocessor directive is not understood on all systems. |
859 | Specifically, I know that Pyramids don't understand it. Thus instead of the |
860 | simple |
861 | |
862 | #if defined(I_FOO) |
863 | # include <foo.h> |
864 | #elif defined(I_BAR) |
865 | # include <bar.h> |
866 | #else |
867 | # include <fubar.h> |
868 | #endif |
869 | |
870 | You have to do the more Byzantine |
871 | |
872 | #if defined(I_FOO) |
873 | # include <foo.h> |
874 | #else |
875 | # if defined(I_BAR) |
876 | # include <bar.h> |
877 | # else |
878 | # include <fubar.h> |
879 | # endif |
880 | #endif |
881 | |
882 | Incidentally, whitespace between the leading '#' and the preprocessor |
883 | command is not guaranteed, but is very portable and you may use it freely. |
884 | I think it makes things a bit more readable, especially once things get |
885 | rather deeply nested. I also think that things should almost never get |
886 | too deeply nested, so it ought to be a moot point :-) |
887 | |
888 | =item Probably Prefer POSIX |
889 | |
890 | It's often the case that you'll need to choose whether to do |
891 | something the BSD-ish way or the POSIX-ish way. It's usually not |
892 | a big problem when the two systems use different names for similar |
893 | functions, such as memcmp() and bcmp(). The perl.h header file |
894 | handles these by appropriate #defines, selecting the POSIX mem*() |
895 | functions if available, but falling back on the b*() functions, if |
896 | need be. |
897 | |
898 | More serious is the case where some brilliant person decided to |
899 | use the same function name but give it a different meaning or |
900 | calling sequence :-). getpgrp() and setpgrp() come to mind. |
901 | These are a real problem on systems that aim for conformance to |
902 | one standard (e.g. POSIX), but still try to support the other way |
903 | of doing things (e.g. BSD). My general advice (still not really |
904 | implemented in the source) is to do something like the following. |
905 | Suppose there are two alternative versions, fooPOSIX() and |
906 | fooBSD(). |
907 | |
908 | #ifdef HAS_FOOPOSIX |
909 | /* use fooPOSIX(); */ |
910 | #else |
911 | # ifdef HAS_FOOBSD |
912 | /* try to emulate fooPOSIX() with fooBSD(); |
913 | perhaps with the following: */ |
914 | # define fooPOSIX fooBSD |
915 | # else |
916 | # /* Uh, oh. We have to supply our own. */ |
917 | # define fooPOSIX Perl_fooPOSIX |
918 | # endif |
919 | #endif |
920 | |
921 | =item Think positively |
922 | |
923 | If you need to add an #ifdef test, it is usually easier to follow if you |
924 | think positively, e.g. |
925 | |
926 | #ifdef HAS_NEATO_FEATURE |
927 | /* use neato feature */ |
928 | #else |
929 | /* use some fallback mechanism */ |
930 | #endif |
931 | |
932 | rather than the more impenetrable |
933 | |
934 | #ifndef MISSING_NEATO_FEATURE |
935 | /* Not missing it, so we must have it, so use it */ |
936 | #else |
937 | /* Are missing it, so fall back on something else. */ |
938 | #endif |
939 | |
940 | Of course for this toy example, there's not much difference. But when |
941 | the #ifdef's start spanning a couple of screen fulls, and the #else's |
942 | are marked something like |
943 | |
944 | #else /* !MISSING_NEATO_FEATURE */ |
945 | |
946 | I find it easy to get lost. |
947 | |
948 | =item Providing Missing Functions -- Problem |
949 | |
950 | Not all systems have all the neat functions you might want or need, so |
951 | you might decide to be helpful and provide an emulation. This is |
952 | sound in theory and very kind of you, but please be careful about what |
953 | you name the function. Let me use the C<pause()> function as an |
954 | illustration. |
955 | |
956 | Perl5.003 has the following in F<perl.h> |
957 | |
958 | #ifndef HAS_PAUSE |
959 | #define pause() sleep((32767<<16)+32767) |
960 | #endif |
961 | |
962 | Configure sets HAS_PAUSE if the system has the pause() function, so |
963 | this #define only kicks in if the pause() function is missing. |
964 | Nice idea, right? |
965 | |
966 | Unfortunately, some systems apparently have a prototype for pause() |
967 | in F<unistd.h>, but don't actually have the function in the library. |
968 | (Or maybe they do have it in a library we're not using.) |
969 | |
970 | Thus, the compiler sees something like |
971 | |
972 | extern int pause(void); |
973 | /* . . . */ |
974 | #define pause() sleep((32767<<16)+32767) |
975 | |
976 | and dies with an error message. (Some compilers don't mind this; |
977 | others apparently do.) |
978 | |
979 | To work around this, 5.003_03 and later have the following in perl.h: |
980 | |
981 | /* Some unistd.h's give a prototype for pause() even though |
982 | HAS_PAUSE ends up undefined. This causes the #define |
983 | below to be rejected by the compiler. Sigh. |
984 | */ |
985 | #ifdef HAS_PAUSE |
986 | # define Pause pause |
987 | #else |
988 | # define Pause() sleep((32767<<16)+32767) |
989 | #endif |
990 | |
991 | This works. |
992 | |
993 | The curious reader may wonder why I didn't do the following in |
994 | F<util.c> instead: |
995 | |
996 | #ifndef HAS_PAUSE |
997 | void pause() |
998 | { |
999 | sleep((32767<<16)+32767); |
1000 | } |
1001 | #endif |
1002 | |
1003 | That is, since the function is missing, just provide it. |
1004 | Then things would probably be been alright, it would seem. |
1005 | |
1006 | Well, almost. It could be made to work. The problem arises from the |
1007 | conflicting needs of dynamic loading and namespace protection. |
1008 | |
1009 | For dynamic loading to work on AIX (and VMS) we need to provide a list |
1010 | of symbols to be exported. This is done by the script F<perl_exp.SH>, |
1011 | which reads F<global.sym> and F<interp.sym>. Thus, the C<pause> |
1012 | symbol would have to be added to F<global.sym> So far, so good. |
1013 | |
1014 | On the other hand, one of the goals of Perl5 is to make it easy to |
1015 | either extend or embed perl and link it with other libraries. This |
1016 | means we have to be careful to keep the visible namespace "clean". |
1017 | That is, we don't want perl's global variables to conflict with |
1018 | those in the other application library. Although this work is still |
1019 | in progress, the way it is currently done is via the F<embed.h> file. |
1020 | This file is built from the F<global.sym> and F<interp.sym> files, |
1021 | since those files already list the globally visible symbols. If we |
1022 | had added C<pause> to global.sym, then F<embed.h> would contain the |
1023 | line |
1024 | |
1025 | #define pause Perl_pause |
1026 | |
1027 | and calls to C<pause> in the perl sources would now point to |
1028 | C<Perl_pause>. Now, when B<ld> is run to build the F<perl> executable, |
1029 | it will go looking for C<perl_pause>, which probably won't exist in any |
1030 | of the standard libraries. Thus the build of perl will fail. |
1031 | |
1032 | Those systems where C<HAS_PAUSE> is not defined would be ok, however, |
1033 | since they would get a C<Perl_pause> function in util.c. The rest of |
1034 | the world would be in trouble. |
1035 | |
1036 | And yes, this scenario has happened. On SCO, the function C<chsize> |
1037 | is available. (I think it's in F<-lx>, the Xenix compatibility |
1038 | library.) Since the perl4 days (and possibly before), Perl has |
1039 | included a C<chsize> function that gets called something akin to |
1040 | |
1041 | #ifndef HAS_CHSIZE |
1042 | I32 chsize(fd, length) |
1043 | /* . . . */ |
1044 | #endif |
1045 | |
1046 | When 5.003 added |
1047 | |
1048 | #define chsize Perl_chsize |
1049 | |
1050 | to F<embed.h>, the compile started failing on SCO systems. |
1051 | |
1052 | The "fix" is to give the function a different name. The one |
1053 | implemented in 5.003_05 isn't optimal, but here's what was done: |
1054 | |
1055 | #ifdef HAS_CHSIZE |
1056 | # ifdef my_chsize /* Probably #defined to Perl_my_chsize in embed.h */ |
1057 | # undef my_chsize |
1058 | # endif |
1059 | # define my_chsize chsize |
1060 | #endif |
1061 | |
1062 | My explanatory comment in patch 5.003_05 said: |
1063 | |
1064 | Undef and then re-define my_chsize from Perl_my_chsize to |
1065 | just plain chsize if this system HAS_CHSIZE. This probably only |
1066 | applies to SCO. This shows the perils of having internal |
1067 | functions with the same name as external library functions :-). |
1068 | |
1069 | Now, we can safely put C<my_chsize> in F<global.sym>, export it, and |
1070 | hide it with F<embed.h>. |
1071 | |
1072 | To be consistent with what I did for C<pause>, I probably should have |
1073 | called the new function C<Chsize>, rather than C<my_chsize>. |
1074 | However, the perl sources are quite inconsistent on this (Consider |
1075 | New, Mymalloc, and Myremalloc, to name just a few.) |
1076 | |
1077 | There is a problem with this fix, however, in that C<Perl_chsize> |
1078 | was available as a F<libperl.a> library function in 5.003, but it |
1079 | isn't available any more (as of 5.003_07). This means that we've |
1080 | broken binary compatibility. This is not good. |
1081 | |
1082 | =item Providing missing functions -- some ideas |
1083 | |
1084 | We currently don't have a standard way of handling such missing |
1085 | function names. Right now, I'm effectively thinking aloud about a |
1086 | solution. Some day, I'll try to formally propose a solution. |
1087 | |
1088 | Part of the problem is that we want to have some functions listed as |
1089 | exported but not have their names mangled by embed.h or possibly |
1090 | conflict with names in standard system headers. We actually already |
1091 | have such a list at the end of F<perl_exp.SH> (though that list is |
1092 | out-of-date): |
1093 | |
1094 | # extra globals not included above. |
1095 | cat <<END >> perl.exp |
1096 | perl_init_ext |
1097 | perl_init_fold |
1098 | perl_init_i18nl14n |
1099 | perl_alloc |
1100 | perl_construct |
1101 | perl_destruct |
1102 | perl_free |
1103 | perl_parse |
1104 | perl_run |
1105 | perl_get_sv |
1106 | perl_get_av |
1107 | perl_get_hv |
1108 | perl_get_cv |
1109 | perl_call_argv |
1110 | perl_call_pv |
1111 | perl_call_method |
1112 | perl_call_sv |
1113 | perl_requirepv |
1114 | safecalloc |
1115 | safemalloc |
1116 | saferealloc |
1117 | safefree |
1118 | |
1119 | This still needs much thought, but I'm inclined to think that one |
1120 | possible solution is to prefix all such functions with C<perl_> in the |
1121 | source and list them along with the other C<perl_*> functions in |
1122 | F<perl_exp.SH>. |
1123 | |
1124 | Thus, for C<chsize>, we'd do something like the following: |
1125 | |
1126 | /* in perl.h */ |
1127 | #ifdef HAS_CHSIZE |
1128 | # define perl_chsize chsize |
1129 | #endif |
1130 | |
1131 | then in some file (e.g. F<util.c> or F<doio.c>) do |
1132 | |
1133 | #ifndef HAS_CHSIZE |
1134 | I32 perl_chsize(fd, length) |
1135 | /* implement the function here . . . */ |
1136 | #endif |
1137 | |
1138 | Alternatively, we could just always use C<chsize> everywhere and move |
1139 | C<chsize> from F<global.sym> to the end of F<perl_exp.SH>. That would |
1140 | probably be fine as long as our C<chsize> function agreed with all the |
1141 | C<chsize> function prototypes in the various systems we'll be using. |
1142 | As long as the prototypes in actual use don't vary that much, this is |
1143 | probably a good alternative. (As a counter-example, note how Configure |
1144 | and perl have to go through hoops to find and use get Malloc_t and |
1145 | Free_t for C<malloc> and C<free>.) |
1146 | |
1147 | At the moment, this latter option is what I tend to prefer. |
1148 | |
1149 | =item All the world's a VAX |
1150 | |
1151 | Sorry, showing my age:-). Still, all the world is not BSD 4.[34], |
1152 | SVR4, or POSIX. Be aware that SVR3-derived systems are still quite |
1153 | common (do you have any idea how many systems run SCO?) If you don't |
1154 | have a bunch of v7 manuals handy, the metaconfig units (by default |
1155 | installed in F</usr/local/lib/dist/U>) are a good resource to look at |
1156 | for portability. |
1157 | |
1158 | =back |
1159 | |
1160 | =head1 Miscellaneous Topics |
1161 | |
1162 | =head2 Autoconf |
1163 | |
1164 | Why does perl use a metaconfig-generated Configure script instead of an |
1165 | autoconf-generated configure script? |
1166 | |
1167 | Metaconfig and autoconf are two tools with very similar purposes. |
1168 | Metaconfig is actually the older of the two, and was originally written |
1169 | by Larry Wall, while autoconf is probably now used in a wider variety of |
1170 | packages. The autoconf info file discusses the history of autoconf and |
1171 | how it came to be. The curious reader is referred there for further |
1172 | information. |
1173 | |
1174 | Overall, both tools are quite good, I think, and the choice of which one |
1175 | to use could be argued either way. In March, 1994, when I was just |
1176 | starting to work on Configure support for Perl5, I considered both |
1177 | autoconf and metaconfig, and eventually decided to use metaconfig for the |
1178 | following reasons: |
1179 | |
1180 | =over 4 |
1181 | |
1182 | =item Compatibility with Perl4 |
1183 | |
1184 | Perl4 used metaconfig, so many of the #ifdef's were already set up for |
1185 | metaconfig. Of course metaconfig had evolved some since Perl4's days, |
1186 | but not so much that it posed any serious problems. |
1187 | |
1188 | =item Metaconfig worked for me |
1189 | |
d1be9408 |
1190 | My system at the time was Interactive 2.2, an SVR3.2/386 derivative that |
aa689395 |
1191 | also had some POSIX support. Metaconfig-generated Configure scripts |
1192 | worked fine for me on that system. On the other hand, autoconf-generated |
1193 | scripts usually didn't. (They did come quite close, though, in some |
1194 | cases.) At the time, I actually fetched a large number of GNU packages |
1195 | and checked. Not a single one configured and compiled correctly |
1196 | out-of-the-box with the system's cc compiler. |
1197 | |
1198 | =item Configure can be interactive |
1199 | |
1200 | With both autoconf and metaconfig, if the script works, everything is |
1201 | fine. However, one of my main problems with autoconf-generated scripts |
1202 | was that if it guessed wrong about something, it could be B<very> hard to |
1203 | go back and fix it. For example, autoconf always insisted on passing the |
1204 | -Xp flag to cc (to turn on POSIX behavior), even when that wasn't what I |
1205 | wanted or needed for that package. There was no way short of editing the |
1206 | configure script to turn this off. You couldn't just edit the resulting |
1207 | Makefile at the end because the -Xp flag influenced a number of other |
1208 | configure tests. |
1209 | |
1210 | Metaconfig's Configure scripts, on the other hand, can be interactive. |
1211 | Thus if Configure is guessing things incorrectly, you can go back and fix |
1212 | them. This isn't as important now as it was when we were actively |
1213 | developing Configure support for new features such as dynamic loading, |
1214 | but it's still useful occasionally. |
1215 | |
1216 | =item GPL |
1217 | |
1218 | At the time, autoconf-generated scripts were covered under the GNU Public |
1219 | License, and hence weren't suitable for inclusion with Perl, which has a |
1220 | different licensing policy. (Autoconf's licensing has since changed.) |
1221 | |
1222 | =item Modularity |
1223 | |
1224 | Metaconfig builds up Configure from a collection of discrete pieces |
1225 | called "units". You can override the standard behavior by supplying your |
1226 | own unit. With autoconf, you have to patch the standard files instead. |
1227 | I find the metaconfig "unit" method easier to work with. Others |
1228 | may find metaconfig's units clumsy to work with. |
1229 | |
1230 | =back |
1231 | |
aa689395 |
1232 | =head2 Why isn't there a directory to override Perl's library? |
1233 | |
1234 | Mainly because no one's gotten around to making one. Note that |
1235 | "making one" involves changing perl.c, Configure, config_h.SH (and |
1236 | associated files, see above), and I<documenting> it all in the |
1237 | INSTALL file. |
1238 | |
1239 | Apparently, most folks who want to override one of the standard library |
1240 | files simply do it by overwriting the standard library files. |
1241 | |
1242 | =head2 APPLLIB |
1243 | |
1244 | In the perl.c sources, you'll find an undocumented APPLLIB_EXP |
1245 | variable, sort of like PRIVLIB_EXP and ARCHLIB_EXP (which are |
1246 | documented in config_h.SH). Here's what APPLLIB_EXP is for, from |
1247 | a mail message from Larry: |
1248 | |
1249 | The main intent of APPLLIB_EXP is for folks who want to send out a |
1250 | version of Perl embedded in their product. They would set the symbol |
1251 | to be the name of the library containing the files needed to run or to |
1252 | support their particular application. This works at the "override" |
1253 | level to make sure they get their own versions of any library code that |
1254 | they absolutely must have configuration control over. |
1255 | |
1256 | As such, I don't see any conflict with a sysadmin using it for a |
1257 | override-ish sort of thing, when installing a generic Perl. It should |
1258 | probably have been named something to do with overriding though. Since |
1259 | it's undocumented we could still change it... :-) |
1260 | |
24f415b4 |
1261 | Given that it's already there, you can use it to override distribution modules. |
1262 | One way to do that is to add |
1263 | |
453a1e5f |
1264 | ccflags="$ccflags -DAPPLLIB_EXP=\"/my/override\"" |
24f415b4 |
1265 | |
1266 | to your config.over file. (You have to be particularly careful to get the |
453a1e5f |
1267 | double quotes in. APPLLIB_EXP must be a valid C string. It might |
1268 | actually be easier to just #define it yourself in perl.c.) |
24f415b4 |
1269 | |
1270 | Then perl.c will put /my/override ahead of ARCHLIB and PRIVLIB. Perl will |
1271 | also search architecture-specific and version-specific subdirectories of |
1272 | APPLLIB_EXP. |
aa689395 |
1273 | |
c4f23d77 |
1274 | =head2 Shared libperl.so location |
1275 | |
1276 | Why isn't the shared libperl.so installed in /usr/lib/ along |
1277 | with "all the other" shared libraries? Instead, it is installed |
1278 | in $archlib, which is typically something like |
1279 | |
1280 | /usr/local/lib/perl5/archname/5.00404 |
1281 | |
1282 | and is architecture- and version-specific. |
1283 | |
1284 | The basic reason why a shared libperl.so gets put in $archlib is so that |
1285 | you can have more than one version of perl on the system at the same time, |
1286 | and have each refer to its own libperl.so. |
1287 | |
1288 | Three examples might help. All of these work now; none would work if you |
1289 | put libperl.so in /usr/lib. |
1290 | |
1291 | =over |
1292 | |
1293 | =item 1. |
1294 | |
1295 | Suppose you want to have both threaded and non-threaded perl versions |
1296 | around. Configure will name both perl libraries "libperl.so" (so that |
1297 | you can link to them with -lperl). The perl binaries tell them apart |
1298 | by having looking in the appropriate $archlib directories. |
1299 | |
1300 | =item 2. |
1301 | |
1302 | Suppose you have perl5.004_04 installed and you want to try to compile |
1303 | it again, perhaps with different options or after applying a patch. |
1304 | If you already have libperl.so installed in /usr/lib/, then it may be |
1305 | either difficult or impossible to get ld.so to find the new libperl.so |
1306 | that you're trying to build. If, instead, libperl.so is tucked away in |
1307 | $archlib, then you can always just change $archlib in the current perl |
1308 | you're trying to build so that ld.so won't find your old libperl.so. |
1309 | (The INSTALL file suggests you do this when building a debugging perl.) |
1310 | |
1311 | =item 3. |
1312 | |
1313 | The shared perl library is not a "well-behaved" shared library with |
1314 | proper major and minor version numbers, so you can't necessarily |
1315 | have perl5.004_04 and perl5.004_05 installed simultaneously. Suppose |
1316 | perl5.004_04 were to install /usr/lib/libperl.so.4.4, and perl5.004_05 |
1317 | were to install /usr/lib/libperl.so.4.5. Now, when you try to run |
1318 | perl5.004_04, ld.so might try to load libperl.so.4.5, since it has |
1319 | the right "major version" number. If this works at all, it almost |
1320 | certainly defeats the reason for keeping perl5.004_04 around. Worse, |
1321 | with development subversions, you certaily can't guarantee that |
1322 | libperl.so.4.4 and libperl.so.4.55 will be compatible. |
1323 | |
1324 | Anyway, all this leads to quite obscure failures that are sure to drive |
1325 | casual users crazy. Even experienced users will get confused :-). Upon |
1326 | reflection, I'd say leave libperl.so in $archlib. |
1327 | |
2032ff04 |
1328 | =item 4. |
1329 | |
1330 | Indentation style: over the years Perl has become a mishmash of |
1331 | various indentation styles, but the original "Larry style" can |
1332 | probably be restored with (GNU) indent somewhat like this: |
1333 | |
1334 | indent -kr -nce -psl -sc |
1335 | |
55c0ed8c |
1336 | A more ambitious solution would also specify a list of Perl specific |
1337 | types with -TSV -TAV -THV .. -TMAGIC -TPerlIO ... but that list would |
1338 | be quite ungainly. Also note that GNU indent also doesn't do aligning |
1339 | of consecutive assignments, which would truly wreck the layout in |
1340 | places like sv.c:Perl_sv_upgrade() or sv.c:Perl_clone_using(). |
1341 | Similarly nicely aligned &&s, ||s and ==s would not be respected. |
2032ff04 |
1342 | |
c4f23d77 |
1343 | =back |
1344 | |
aa689395 |
1345 | =head1 Upload Your Work to CPAN |
1346 | |
1347 | You can upload your work to CPAN if you have a CPAN id. Check out |
a93751fa |
1348 | http://www.cpan.org/modules/04pause.html for information on |
aa689395 |
1349 | _PAUSE_, the Perl Author's Upload Server. |
1350 | |
1351 | I typically upload both the patch file, e.g. F<perl5.004_08.pat.gz> |
1352 | and the full tar file, e.g. F<perl5.004_08.tar.gz>. |
1353 | |
1354 | If you want your patch to appear in the F<src/5.0/unsupported> |
1355 | directory on CPAN, send e-mail to the CPAN master librarian. (Check |
a93751fa |
1356 | out http://www.cpan.org/CPAN.html ). |
aa689395 |
1357 | |
1358 | =head1 Help Save the World |
1359 | |
1360 | You should definitely announce your patch on the perl5-porters list. |
1361 | You should also consider announcing your patch on |
1362 | comp.lang.perl.announce, though you should make it quite clear that a |
1363 | subversion is not a production release, and be prepared to deal with |
1364 | people who will not read your disclaimer. |
1365 | |
1366 | =head1 Todo |
1367 | |
1368 | Here, in no particular order, are some Configure and build-related |
1369 | items that merit consideration. This list isn't exhaustive, it's just |
1370 | what I came up with off the top of my head. |
1371 | |
e25f343d |
1372 | =head2 Adding missing library functions to Perl |
1373 | |
1374 | The perl Configure script automatically determines which headers and |
1375 | functions you have available on your system and arranges for them to be |
1376 | included in the compilation and linking process. Occasionally, when porting |
1377 | perl to an operating system for the first time, you may find that the |
1378 | operating system is missing a key function. While perl may still build |
1379 | without this function, no perl program will be able to reference the missing |
1380 | function. You may be able to write the missing function yourself, or you |
1381 | may be able to find the missing function in the distribution files for |
1382 | another software package. In this case, you need to instruct the perl |
1383 | configure-and-build process to use your function. Perform these steps. |
1384 | |
1385 | =over 3 |
1386 | |
1387 | =item * |
1388 | |
2ecb232b |
1389 | Code and test the function you wish to add. Test it carefully; you will |
e25f343d |
1390 | have a much easier time debugging your code independently than when it is a |
1391 | part of perl. |
1392 | |
1393 | =item * |
1394 | |
1395 | Here is an implementation of the POSIX truncate function for an operating |
1396 | system (VOS) that does not supply one, but which does supply the ftruncate() |
1397 | function. |
1398 | |
1399 | /* Beginning of modification history */ |
1400 | /* Written 02-01-02 by Nick Ing-Simmons (nick@ing-simmons.net) */ |
1401 | /* End of modification history */ |
1402 | |
1403 | /* VOS doesn't supply a truncate function, so we build one up |
1404 | from the available POSIX functions. */ |
1405 | |
1406 | #include <fcntl.h> |
1407 | #include <sys/types.h> |
1408 | #include <unistd.h> |
1409 | |
1410 | int |
1411 | truncate(const char *path, off_t len) |
1412 | { |
1413 | int fd = open(path,O_WRONLY); |
1414 | int code = -1; |
1415 | if (fd >= 0) { |
1416 | code = ftruncate(fd,len); |
1417 | close(fd); |
1418 | } |
1419 | return code; |
1420 | } |
1421 | |
1422 | Place this file into a subdirectory that has the same name as the operating |
1423 | system. This file is named perl/vos/vos.c |
1424 | |
1425 | =item * |
1426 | |
1427 | If your operating system has a hints file (in perl/hints/XXX.sh for an |
1428 | operating system named XXX), then start with it. If your operating system |
1429 | has no hints file, then create one. You can use a hints file for a similar |
1430 | operating system, if one exists, as a template. |
1431 | |
1432 | =item * |
1433 | |
1434 | Add lines like the following to your hints file. The first line |
1435 | (d_truncate="define") instructs Configure that the truncate() function |
1436 | exists. The second line (archobjs="vos.o") instructs the makefiles that the |
1437 | perl executable depends on the existence of a file named "vos.o". (Make |
1438 | will automatically look for "vos.c" and compile it with the same options as |
1439 | the perl source code). The final line ("test -h...") adds a symbolic link |
1440 | to the top-level directory so that make can find vos.c. Of course, you |
1441 | should use your own operating system name for the source file of extensions, |
1442 | not "vos.c". |
1443 | |
1444 | # VOS does not have truncate() but we supply one in vos.c |
1445 | d_truncate="define" |
1446 | archobjs="vos.o" |
1447 | |
1448 | # Help gmake find vos.c |
1449 | test -h vos.c || ln -s vos/vos.c vos.c |
1450 | |
1451 | The hints file is a series of shell commands that are run in the top-level |
1452 | directory (the "perl" directory). Thus, these commands are simply executed |
1453 | by Configure at an appropriate place during its execution. |
1454 | |
1455 | =item * |
1456 | |
1457 | At this point, you can run the Configure script and rebuild perl. Carefully |
1458 | test the newly-built perl to ensure that normal paths, and error paths, |
1459 | behave as you expect. |
1460 | |
1461 | =back |
1462 | |
aa689395 |
1463 | =head2 Good ideas waiting for round tuits |
1464 | |
1465 | =over 4 |
1466 | |
c4f23d77 |
1467 | =item Configure -Dsrc=/blah/blah |
aa689395 |
1468 | |
1469 | We should be able to emulate B<configure --srcdir>. Tom Tromey |
1470 | tromey@creche.cygnus.com has submitted some patches to |
c4f23d77 |
1471 | the dist-users mailing list along these lines. They have been folded |
1472 | back into the main distribution, but various parts of the perl |
1473 | Configure/build/install process still assume src='.'. |
aa689395 |
1474 | |
1475 | =item Hint file fixes |
1476 | |
1477 | Various hint files work around Configure problems. We ought to fix |
1478 | Configure so that most of them aren't needed. |
1479 | |
1480 | =item Hint file information |
1481 | |
1482 | Some of the hint file information (particularly dynamic loading stuff) |
1483 | ought to be fed back into the main metaconfig distribution. |
1484 | |
1485 | =back |
1486 | |
1487 | =head2 Probably good ideas waiting for round tuits |
1488 | |
1489 | =over 4 |
1490 | |
1491 | =item GNU configure --options |
1492 | |
1493 | I've received sensible suggestions for --exec_prefix and other |
1494 | GNU configure --options. It's not always obvious exactly what is |
1495 | intended, but this merits investigation. |
1496 | |
1497 | =item make clean |
1498 | |
1499 | Currently, B<make clean> isn't all that useful, though |
1500 | B<make realclean> and B<make distclean> are. This needs a bit of |
1501 | thought and documentation before it gets cleaned up. |
1502 | |
1503 | =item Try gcc if cc fails |
1504 | |
1505 | Currently, we just give up. |
1506 | |
1507 | =item bypassing safe*alloc wrappers |
1508 | |
1509 | On some systems, it may be safe to call the system malloc directly |
1510 | without going through the util.c safe* layers. (Such systems would |
1511 | accept free(0), for example.) This might be a time-saver for systems |
1512 | that already have a good malloc. (Recent Linux libc's apparently have |
1513 | a nice malloc that is well-tuned for the system.) |
1514 | |
1515 | =back |
1516 | |
1517 | =head2 Vague possibilities |
1518 | |
1519 | =over 4 |
1520 | |
aa689395 |
1521 | =item MacPerl |
1522 | |
3e3baf6d |
1523 | Get some of the Macintosh stuff folded back into the main distribution. |
aa689395 |
1524 | |
1525 | =item gconvert replacement |
1526 | |
1527 | Maybe include a replacement function that doesn't lose data in rare |
1528 | cases of coercion between string and numerical values. |
1529 | |
aa689395 |
1530 | =item Improve makedepend |
1531 | |
1532 | The current makedepend process is clunky and annoyingly slow, but it |
1533 | works for most folks. Alas, it assumes that there is a filename |
1534 | $firstmakefile that the B<make> command will try to use before it uses |
1535 | F<Makefile>. Such may not be the case for all B<make> commands, |
1536 | particularly those on non-Unix systems. |
1537 | |
1538 | Probably some variant of the BSD F<.depend> file will be useful. |
1539 | We ought to check how other packages do this, if they do it at all. |
1540 | We could probably pre-generate the dependencies (with the exception of |
1541 | malloc.o, which could probably be determined at F<Makefile.SH> |
1542 | extraction time. |
1543 | |
1544 | =item GNU Makefile standard targets |
1545 | |
1546 | GNU software generally has standardized Makefile targets. Unless we |
1547 | have good reason to do otherwise, I see no reason not to support them. |
1548 | |
1549 | =item File locking |
1550 | |
1551 | Somehow, straighten out, document, and implement lockf(), flock(), |
76ba0908 |
1552 | and/or fcntl() file locking. It's a mess. See $d_fcntl_can_lock |
1553 | in recent config.sh files though. |
aa689395 |
1554 | |
1555 | =back |
1556 | |
fb73857a |
1557 | =head1 AUTHORS |
aa689395 |
1558 | |
fb73857a |
1559 | Original author: Andy Dougherty doughera@lafcol.lafayette.edu . |
1560 | Additions by Chip Salzenberg chip@perl.com and |
1561 | Tim Bunce Tim.Bunce@ig.co.uk . |
aa689395 |
1562 | |
1563 | All opinions expressed herein are those of the authorZ<>(s). |
1564 | |
1565 | =head1 LAST MODIFIED |
1566 | |
ff935051 |
1567 | $Id: pumpkin.pod,v 1.23 2000/01/13 19:45:13 doughera Released $ |