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1 | =head1 Name |
2 | ||
3 | patching.pod - Appropriate format for patches to the perl source tree | |
4 | ||
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5 | =head2 How to contribute to this document |
6 | ||
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7 | You may mail corrections, additions, and suggestions by following the |
8 | instructions set forth in this document and submitting a patch :). | |
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9 | |
10 | =head1 Description | |
11 | ||
12 | =head2 Why this document exists | |
13 | ||
14 | As an open source project Perl relies on patches and contributions from | |
15 | its users to continue functioning properly and to root out the inevitable | |
16 | bugs. But, some users are unsure as to the I<right> way to prepare a patch | |
17 | and end up submitting seriously malformed patches. This makes it very | |
18 | difficult for the current maintainer to integrate said patches into their | |
19 | distribution. This document sets out usage guidelines for patches in an | |
20 | attempt to make everybody's life easier. | |
21 | ||
22 | =head2 Common problems | |
23 | ||
24 | The most common problems appear to be patches being mangled by certain | |
25 | mailers (I won't name names, but most of these seem to be originating on | |
54aff467 | 26 | boxes running a certain popular commercial operating system). Other problems |
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27 | include patches not rooted in the appropriate place in the directory structure, |
28 | and patches not produced using standard utilities (such as diff). | |
29 | ||
30 | =head1 Proper Patch Guidelines | |
31 | ||
f556e4ac DG |
32 | =head2 What to patch |
33 | ||
34 | Generally speaking you should patch the latest development release | |
35 | of perl. The maintainers of the individual branches will see to it | |
36 | that patches are picked up and applied as appropriate. | |
37 | ||
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38 | =head2 How to prepare your patch |
39 | ||
40 | =over 4 | |
41 | ||
42 | =item Creating your patch | |
43 | ||
44 | First, back up the original files. This can't be stressed enough, | |
45 | back everything up _first_. | |
46 | ||
47 | Also, please create patches against a clean distribution of the perl source. | |
54aff467 | 48 | This ensures that everyone else can apply your patch without clobbering their |
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49 | source tree. |
50 | ||
51 | =item diff | |
52 | ||
53 | While individual tastes vary (and are not the point here) patches should | |
54 | be created using either C<-u> or C<-c> arguments to diff. These produce, | |
55 | respectively, unified diffs (where the changed line appears immediately next | |
56 | to the original) and context diffs (where several lines surrounding the changes | |
57 | are included). See the manpage for diff for more details. | |
58 | ||
4a92fa57 MB |
59 | When GNU diff is available, the pumpkins would prefer you use C<-u -p> |
60 | (--unified --show-c-function) as arguments for optimal control. The | |
61 | examples below will only use -u. | |
62 | ||
54aff467 GS |
63 | The preferred method for creating a unified diff suitable for feeding |
64 | to the patch program is: | |
55d729e4 | 65 | |
54aff467 | 66 | diff -u old-file new-file > patch-file |
55d729e4 | 67 | |
54aff467 GS |
68 | Note the order of files. See below for how to create a patch from |
69 | two directory trees. | |
55d729e4 | 70 | |
54aff467 GS |
71 | If your patch is for wider consumption, it may be better to create it as |
72 | a context diff as some machines have broken patch utilities that choke on | |
73 | unified diffs. A context diff is made using C<diff -c> rather than | |
74 | C<diff -u>. | |
55d729e4 | 75 | |
9e52009c GS |
76 | GNU diff has many desirable features not provided by most vendor-supplied |
77 | diffs. Some examples using GNU diff: | |
78 | ||
79 | # generate a patch for a newly added file | |
80 | % diff -u /dev/null new/file | |
1266ad8f | 81 | |
9e52009c GS |
82 | # generate a patch to remove a file (patch > v2.4 will remove it cleanly) |
83 | % diff -u old/goner /dev/null | |
1266ad8f | 84 | |
9e52009c GS |
85 | # get additions, deletions along with everything else, recursively |
86 | % diff -ruN olddir newdir | |
1266ad8f | 87 | |
9e52009c GS |
88 | # ignore whitespace |
89 | % diff -bu a/file b/file | |
1266ad8f | 90 | |
9e52009c | 91 | # show function name in every hunk (safer, more informative) |
4a92fa57 | 92 | % diff -u -p old/file new/file |
9e52009c GS |
93 | % diff -u -F '^[_a-zA-Z0-9]+ *(' old/file new/file |
94 | ||
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95 | # show sub name in perl files and modules |
96 | % diff -u -F '^sub' old/file.pm new/file.pm | |
97 | ||
98 | # show header in doc patches | |
99 | % diff -u -F '^=head' old/file.pod new/file.pod | |
100 | ||
39f9fc43 | 101 | =item Derived Files |
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102 | |
103 | Many files in the distribution are derivative--avoid patching them. | |
104 | Patch the originals instead. Most utilities (like perldoc) are in | |
105 | this category, i.e. patch utils/perldoc.PL rather than utils/perldoc. | |
106 | Similarly, don't create patches for files under $src_root/ext from | |
107 | their copies found in $install_root/lib. If you are unsure about the | |
108 | proper location of a file that may have gotten copied while building | |
109 | the source distribution, consult the C<MANIFEST>. | |
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110 | |
111 | =item Filenames | |
112 | ||
113 | The most usual convention when submitting patches for a single file is to make | |
114 | your changes to a copy of the file with the same name as the original. Rename | |
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115 | the original file in such a way that it is obvious what is being patched |
116 | ($file.dist or $file.old seem to be popular). | |
117 | ||
118 | If you are submitting patches that affect multiple files then you should | |
119 | backup the entire directory tree (to $source_root.old/ for example). This | |
120 | will allow C<diff -ruN old-dir new-dir> to create all the patches at once. | |
55d729e4 | 121 | |
39f9fc43 A |
122 | =item Directories |
123 | ||
124 | IMPORTANT: Patches should be generated from the source root directory, not | |
125 | from the directory that the patched file resides in. This ensures that the | |
126 | maintainer patches the proper file. | |
127 | ||
128 | For larger patches that are dealing with multiple files or | |
129 | directories, Johan Vromans has written a powerful utility: makepatch. | |
130 | See the JV directory on CPAN for the current version. If you have this | |
131 | program available, it is recommended to create a duplicate of the perl | |
132 | directory tree against which you are intending to provide a patch and | |
133 | let makepatch figure out all the changes you made to your copy of the | |
134 | sources. As perl comes with a MANIFEST file, you need not delete | |
135 | object files and other derivative files from the two directory trees, | |
136 | makepatch is smart about them. | |
137 | ||
138 | Say, you have created a directory perl-5.7.1@8685/ for the perl you | |
139 | are taking as the base and a directory perl-5.7.1@8685-withfoo/ where | |
140 | you have your changes, you would run makepatch as follows: | |
141 | ||
142 | makepatch -oldman perl-5.7.1@8685/MANIFEST \ | |
143 | -newman perl-5.7.1@8685-withfoo/MANIFEST \ | |
144 | -diff "diff -u" \ | |
145 | perl-5.7.1@8685 perl-5.7.1@8685-withfoo | |
146 | ||
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147 | =item Binary Files |
148 | ||
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149 | Since the patch(1) utility cannot deal with binary files, it's important |
150 | that you either avoid the use of binary files in your patch, generate the | |
151 | files dynamically, or that you encode any binary files using the | |
1266ad8f | 152 | F<uupacktool.pl> utility. |
687d3573 | 153 | |
21f7822e | 154 | Assuming you needed to include a gzip-encoded file for a module's test |
1266ad8f | 155 | suite, you might do this as follows using the F<uupacktool.pl> utility: |
687d3573 | 156 | |
1266ad8f | 157 | $ perl uupacktool.pl -v -p -D lib/Some/Module/t/src/t.gz |
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158 | Writing lib/Some/Module/t/src/t.gz into lib/Some/Module/t/src/t.gz.packed |
159 | ||
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160 | This will replace the C<t.gz> file with an encoded counterpart. During |
161 | C<make test>, before any tests are run, perl's Makefile will restore all | |
162 | the C<.packed> files mentioned in the MANIFEST to their original name. | |
163 | This means that the test suite does not need to be aware of this packing | |
164 | scheme and will not need to be altered. | |
687d3573 | 165 | |
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166 | =item Try it yourself |
167 | ||
168 | Just to make sure your patch "works", be sure to apply it to the Perl | |
169 | distribution, rebuild everything, and make sure the testsuite runs | |
170 | without incident. | |
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171 | |
172 | =back | |
173 | ||
174 | =head2 What to include in your patch | |
175 | ||
176 | =over 4 | |
177 | ||
178 | =item Description of problem | |
179 | ||
180 | The first thing you should include is a description of the problem that | |
181 | the patch corrects. If it is a code patch (rather than a documentation | |
182 | patch) you should also include a small test case that illustrates the | |
183 | bug. | |
184 | ||
54aff467 | 185 | =item Directions for application |
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186 | |
187 | You should include instructions on how to properly apply your patch. | |
188 | These should include the files affected, any shell scripts or commands | |
189 | that need to be run before or after application of the patch, and | |
190 | the command line necessary for application. | |
191 | ||
192 | =item If you have a code patch | |
193 | ||
194 | If you are submitting a code patch there are several other things that | |
195 | you need to do. | |
196 | ||
197 | =over 4 | |
198 | ||
199 | =item Comments, Comments, Comments | |
200 | ||
201 | Be sure to adequately comment your code. While commenting every | |
202 | line is unnecessary, anything that takes advantage of side effects of | |
203 | operators, that creates changes that will be felt outside of the | |
204 | function being patched, or that others may find confusing should | |
205 | be documented. If you are going to err, it is better to err on the | |
206 | side of adding too many comments than too few. | |
207 | ||
208 | =item Style | |
209 | ||
54aff467 GS |
210 | In general, please follow the particular style of the code you are patching. |
211 | ||
212 | In particular, follow these general guidelines for patching Perl sources: | |
213 | ||
214 | 8-wide tabs (no exceptions!) | |
215 | 4-wide indents for code, 2-wide indents for nested CPP #defines | |
216 | try hard not to exceed 79-columns | |
217 | ANSI C prototypes | |
218 | uncuddled elses and "K&R" style for indenting control constructs | |
219 | no C++ style (//) comments, most C compilers will choke on them | |
220 | mark places that need to be revisited with XXX (and revisit often!) | |
221 | opening brace lines up with "if" when conditional spans multiple | |
222 | lines; should be at end-of-line otherwise | |
223 | in function definitions, name starts in column 0 (return value is on | |
224 | previous line) | |
225 | single space after keywords that are followed by parens, no space | |
226 | between function name and following paren | |
227 | avoid assignments in conditionals, but if they're unavoidable, use | |
228 | extra paren, e.g. "if (a && (b = c)) ..." | |
229 | "return foo;" rather than "return(foo);" | |
230 | "if (!foo) ..." rather than "if (foo == FALSE) ..." etc. | |
231 | ||
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232 | |
233 | =item Testsuite | |
234 | ||
f4dad39e DG |
235 | When submitting a patch you should make every effort to also include |
236 | an addition to perl's regression tests to properly exercise your | |
237 | patch. Your testsuite additions should generally follow these | |
54aff467 | 238 | guidelines (courtesy of Gurusamy Sarathy <gsar@activestate.com>): |
f4dad39e DG |
239 | |
240 | Know what you're testing. Read the docs, and the source. | |
241 | Tend to fail, not succeed. | |
242 | Interpret results strictly. | |
243 | Use unrelated features (this will flush out bizarre interactions). | |
244 | Use non-standard idioms (otherwise you are not testing TIMTOWTDI). | |
f556e4ac DG |
245 | Avoid using hardcoded test numbers whenever possible (the |
246 | EXPECTED/GOT found in t/op/tie.t is much more maintainable, | |
247 | and gives better failure reports). | |
f4dad39e DG |
248 | Give meaningful error messages when a test fails. |
249 | Avoid using qx// and system() unless you are testing for them. If you | |
250 | do use them, make sure that you cover _all_ perl platforms. | |
251 | Unlink any temporary files you create. | |
252 | Promote unforeseen warnings to errors with $SIG{__WARN__}. | |
54aff467 | 253 | Be sure to use the libraries and modules shipped with the version |
f556e4ac | 254 | being tested, not those that were already installed. |
f4dad39e | 255 | Add comments to the code explaining what you are testing for. |
f556e4ac DG |
256 | Make updating the '1..42' string unnecessary. Or make sure that |
257 | you update it. | |
54aff467 GS |
258 | Test _all_ behaviors of a given operator, library, or function: |
259 | - All optional arguments | |
260 | - Return values in various contexts (boolean, scalar, list, lvalue) | |
261 | - Use both global and lexical variables | |
262 | - Don't forget the exceptional, pathological cases. | |
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263 | |
264 | =back | |
265 | ||
266 | =item Test your patch | |
267 | ||
268 | Apply your patch to a clean distribution, compile, and run the | |
269 | regression test suite (you did remember to add one for your | |
270 | patch, didn't you). | |
271 | ||
272 | =back | |
273 | ||
274 | =head2 An example patch creation | |
275 | ||
54aff467 | 276 | This should work for most patches: |
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277 | |
278 | cp MANIFEST MANIFEST.old | |
279 | emacs MANIFEST | |
280 | (make changes) | |
281 | cd .. | |
535aafb8 | 282 | diff -c perl5.7.42/MANIFEST.old perl5.7.42/MANIFEST > mypatch |
55d729e4 | 283 | (testing the patch:) |
535aafb8 PN |
284 | mv perl5.7.42/MANIFEST perl5.7.42/MANIFEST.new |
285 | cp perl5.7.42/MANIFEST.old perl5.7.42/MANIFEST | |
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286 | patch -p < mypatch |
287 | (should succeed) | |
535aafb8 | 288 | diff perl5.7.42/MANIFEST perl5.7.42/MANIFEST.new |
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289 | (should produce no output) |
290 | ||
291 | =head2 Submitting your patch | |
292 | ||
293 | =over 4 | |
294 | ||
295 | =item Mailers | |
296 | ||
297 | Please, please, please (get the point? 8-) don't use a mailer that | |
69c646ef JH |
298 | word wraps your patch. This leaves the patch essentially worthless |
299 | to the maintainers. | |
55d729e4 | 300 | |
69c646ef JH |
301 | Unfortunately many mailers word wrap the main text of messages, but |
302 | luckily you can usually send your patches as email attachments without | |
303 | them getting "helpfully" word wrapped. | |
304 | ||
305 | If you have no choice in mailers and no way to get your hands on | |
306 | a better one, there is, of course, a Perl solution. Just do this: | |
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307 | |
308 | perl -ne 'print pack("u*",$_)' patch > patch.uue | |
309 | ||
310 | and post patch.uue with a note saying to unpack it using | |
311 | ||
312 | perl -ne 'print unpack("u*",$_)' patch.uue > patch | |
313 | ||
314 | =item Subject lines for patches | |
315 | ||
316 | The subject line on your patch should read | |
317 | ||
535aafb8 | 318 | [PATCH 5.x.x AREA] Description |
55d729e4 | 319 | |
54aff467 GS |
320 | where the x's are replaced by the appropriate version number. |
321 | The description should be a very brief but accurate summary of the | |
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322 | problem (don't forget this is an email header). |
323 | ||
54aff467 | 324 | Examples: |
55d729e4 | 325 | |
535aafb8 | 326 | [PATCH 5.6.4 DOC] fix minor typos |
55d729e4 | 327 | |
535aafb8 | 328 | [PATCH 5.7.9 CORE] New warning for foo() when frobbing |
55d729e4 | 329 | |
535aafb8 | 330 | [PATCH 5.7.16 CONFIG] Added support for fribnatz 1.5 |
54aff467 GS |
331 | |
332 | The name of the file being patched makes for a poor subject line if | |
333 | no other descriptive text accompanies it. | |
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334 | |
335 | =item Where to send your patch | |
336 | ||
54aff467 GS |
337 | If your patch is for a specific bug in the Perl core, it should be sent |
338 | using the perlbug utility. Don't forget to describe the problem and the | |
339 | fix adequately. | |
340 | ||
55d729e4 GS |
341 | If it is a patch to a module that you downloaded from CPAN you should |
342 | submit your patch to that module's author. | |
343 | ||
54aff467 GS |
344 | If your patch addresses one of the items described in perltodo.pod, |
345 | please discuss your approach B<before> you make the patch at | |
346 | <perl5-porters@perl.org>. Be sure to browse the archives of past | |
347 | discussions (see perltodo.pod for archive locations). | |
348 | ||
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349 | =back |
350 | ||
351 | =head2 Applying a patch | |
352 | ||
353 | =over 4 | |
354 | ||
355 | =item General notes on applying patches | |
356 | ||
357 | The following are some general notes on applying a patch | |
358 | to your perl distribution. | |
359 | ||
360 | =over 4 | |
361 | ||
362 | =item patch C<-p> | |
363 | ||
54aff467 GS |
364 | It is generally easier to apply patches with the C<-p N> argument to |
365 | patch (where N is the number of path components to skip in the files | |
366 | found in the headers). This helps reconcile differing paths between | |
367 | the machine the patch was created on and the machine on which it is | |
368 | being applied. | |
55d729e4 | 369 | |
4a92fa57 MB |
370 | Be sure to use the Larry Wall version of patch. Some Operating Systems |
371 | (HP-UX amongst those) have a patch command that does something completely | |
372 | different. The correct version of patch will show Larry's name several | |
373 | times when invoked as patch --version. | |
374 | ||
55d729e4 GS |
375 | =item Cut and paste |
376 | ||
54aff467 | 377 | B<Never> cut and paste a patch into your editor. This usually clobbers |
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378 | the tabs and confuses patch. |
379 | ||
380 | =item Hand editing patches | |
381 | ||
54aff467 GS |
382 | Avoid hand editing patches as this almost always screws up the line |
383 | numbers and offsets in the patch, making it useless. | |
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384 | |
385 | =back | |
386 | ||
387 | =back | |
388 | ||
389 | =head2 Final notes | |
390 | ||
391 | If you follow these guidelines it will make everybody's life a little | |
392 | easier. You'll have the satisfaction of having contributed to perl, | |
393 | others will have an easy time using your work, and it should be easier | |
1266ad8f | 394 | for the maintainers to coordinate the occasionally large numbers of |
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395 | patches received. |
396 | ||
f556e4ac DG |
397 | Also, just because you're not a brilliant coder doesn't mean that you |
398 | can't contribute. As valuable as code patches are there is always a | |
399 | need for better documentation (especially considering the general | |
400 | level of joy that most programmers feel when forced to sit down and | |
401 | write docs). If all you do is patch the documentation you have still | |
402 | contributed more than the person who sent in an amazing new feature | |
403 | that no one can use because no one understands the code (what I'm | |
404 | getting at is that documentation is both the hardest part to do | |
405 | (because everyone hates doing it) and the most valuable). | |
406 | ||
407 | Mostly, when contributing patches, imagine that it is B<you> receiving | |
408 | hundreds of patches and that it is B<your> responsibility to integrate | |
409 | them into the source. Obviously you'd want the patches to be as easy | |
410 | to apply as possible. Keep that in mind. 8-) | |
55d729e4 | 411 | |
55d729e4 GS |
412 | =head1 Author and Copyright Information |
413 | ||
4a92fa57 | 414 | Copyright (c) 1998-2002 Daniel Grisinger |
55d729e4 GS |
415 | |
416 | Adapted from a posting to perl5-porters by Tim Bunce (Tim.Bunce@ig.co.uk). | |
417 | ||
418 | I'd like to thank the perl5-porters for their suggestions. |