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1 | =head1 Name |
2 | ||
3 | patching.pod - Appropriate format for patches to the perl source tree | |
4 | ||
f4dad39e | 5 | =head2 Where to get this document |
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6 | |
7 | The latest version of this document is available from | |
f4dad39e | 8 | http://perrin.dimensional.com/perl/perlpatch.html |
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9 | |
10 | =head2 How to contribute to this document | |
11 | ||
12 | You may mail corrections, additions, and suggestions to me | |
f556e4ac | 13 | at dgris@dimensional.com but the preferred method would be |
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14 | to follow the instructions set forth in this document and |
15 | submit a patch 8-). | |
16 | ||
17 | =head1 Description | |
18 | ||
19 | =head2 Why this document exists | |
20 | ||
21 | As an open source project Perl relies on patches and contributions from | |
22 | its users to continue functioning properly and to root out the inevitable | |
23 | bugs. But, some users are unsure as to the I<right> way to prepare a patch | |
24 | and end up submitting seriously malformed patches. This makes it very | |
25 | difficult for the current maintainer to integrate said patches into their | |
26 | distribution. This document sets out usage guidelines for patches in an | |
27 | attempt to make everybody's life easier. | |
28 | ||
29 | =head2 Common problems | |
30 | ||
31 | The most common problems appear to be patches being mangled by certain | |
32 | mailers (I won't name names, but most of these seem to be originating on | |
54aff467 | 33 | boxes running a certain popular commercial operating system). Other problems |
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34 | include patches not rooted in the appropriate place in the directory structure, |
35 | and patches not produced using standard utilities (such as diff). | |
36 | ||
37 | =head1 Proper Patch Guidelines | |
38 | ||
f556e4ac DG |
39 | =head2 What to patch |
40 | ||
41 | Generally speaking you should patch the latest development release | |
42 | of perl. The maintainers of the individual branches will see to it | |
43 | that patches are picked up and applied as appropriate. | |
44 | ||
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45 | =head2 How to prepare your patch |
46 | ||
47 | =over 4 | |
48 | ||
49 | =item Creating your patch | |
50 | ||
51 | First, back up the original files. This can't be stressed enough, | |
52 | back everything up _first_. | |
53 | ||
54 | Also, please create patches against a clean distribution of the perl source. | |
54aff467 | 55 | This ensures that everyone else can apply your patch without clobbering their |
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56 | source tree. |
57 | ||
58 | =item diff | |
59 | ||
60 | While individual tastes vary (and are not the point here) patches should | |
61 | be created using either C<-u> or C<-c> arguments to diff. These produce, | |
62 | respectively, unified diffs (where the changed line appears immediately next | |
63 | to the original) and context diffs (where several lines surrounding the changes | |
64 | are included). See the manpage for diff for more details. | |
65 | ||
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66 | The preferred method for creating a unified diff suitable for feeding |
67 | to the patch program is: | |
55d729e4 | 68 | |
54aff467 | 69 | diff -u old-file new-file > patch-file |
55d729e4 | 70 | |
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71 | Note the order of files. See below for how to create a patch from |
72 | two directory trees. | |
55d729e4 | 73 | |
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74 | If your patch is for wider consumption, it may be better to create it as |
75 | a context diff as some machines have broken patch utilities that choke on | |
76 | unified diffs. A context diff is made using C<diff -c> rather than | |
77 | C<diff -u>. | |
55d729e4 | 78 | |
9e52009c GS |
79 | GNU diff has many desirable features not provided by most vendor-supplied |
80 | diffs. Some examples using GNU diff: | |
81 | ||
82 | # generate a patch for a newly added file | |
83 | % diff -u /dev/null new/file | |
84 | ||
85 | # generate a patch to remove a file (patch > v2.4 will remove it cleanly) | |
86 | % diff -u old/goner /dev/null | |
87 | ||
88 | # get additions, deletions along with everything else, recursively | |
89 | % diff -ruN olddir newdir | |
90 | ||
91 | # ignore whitespace | |
92 | % diff -bu a/file b/file | |
93 | ||
94 | # show function name in every hunk (safer, more informative) | |
95 | % diff -u -F '^[_a-zA-Z0-9]+ *(' old/file new/file | |
96 | ||
97 | ||
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98 | =item Directories |
99 | ||
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100 | IMPORTANT: Patches should be generated from the source root directory, not |
101 | from the directory that the patched file resides in. This ensures that the | |
102 | maintainer patches the proper file. | |
103 | ||
104 | Many files in the distribution are derivative--avoid patching them. | |
105 | Patch the originals instead. Most utilities (like perldoc) are in | |
106 | this category, i.e. patch utils/perldoc.PL rather than utils/perldoc. | |
107 | Similarly, don't create patches for files under $src_root/ext from | |
108 | their copies found in $install_root/lib. If you are unsure about the | |
109 | proper location of a file that may have gotten copied while building | |
110 | the source distribution, consult the C<MANIFEST>. | |
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111 | |
112 | =item Filenames | |
113 | ||
114 | The most usual convention when submitting patches for a single file is to make | |
115 | your changes to a copy of the file with the same name as the original. Rename | |
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116 | the original file in such a way that it is obvious what is being patched |
117 | ($file.dist or $file.old seem to be popular). | |
118 | ||
119 | If you are submitting patches that affect multiple files then you should | |
120 | backup the entire directory tree (to $source_root.old/ for example). This | |
121 | will allow C<diff -ruN old-dir new-dir> to create all the patches at once. | |
55d729e4 | 122 | |
54aff467 GS |
123 | =item Try it yourself |
124 | ||
125 | Just to make sure your patch "works", be sure to apply it to the Perl | |
126 | distribution, rebuild everything, and make sure the testsuite runs | |
127 | without incident. | |
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128 | |
129 | =back | |
130 | ||
131 | =head2 What to include in your patch | |
132 | ||
133 | =over 4 | |
134 | ||
135 | =item Description of problem | |
136 | ||
137 | The first thing you should include is a description of the problem that | |
138 | the patch corrects. If it is a code patch (rather than a documentation | |
139 | patch) you should also include a small test case that illustrates the | |
140 | bug. | |
141 | ||
54aff467 | 142 | =item Directions for application |
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143 | |
144 | You should include instructions on how to properly apply your patch. | |
145 | These should include the files affected, any shell scripts or commands | |
146 | that need to be run before or after application of the patch, and | |
147 | the command line necessary for application. | |
148 | ||
149 | =item If you have a code patch | |
150 | ||
151 | If you are submitting a code patch there are several other things that | |
152 | you need to do. | |
153 | ||
154 | =over 4 | |
155 | ||
156 | =item Comments, Comments, Comments | |
157 | ||
158 | Be sure to adequately comment your code. While commenting every | |
159 | line is unnecessary, anything that takes advantage of side effects of | |
160 | operators, that creates changes that will be felt outside of the | |
161 | function being patched, or that others may find confusing should | |
162 | be documented. If you are going to err, it is better to err on the | |
163 | side of adding too many comments than too few. | |
164 | ||
165 | =item Style | |
166 | ||
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167 | In general, please follow the particular style of the code you are patching. |
168 | ||
169 | In particular, follow these general guidelines for patching Perl sources: | |
170 | ||
171 | 8-wide tabs (no exceptions!) | |
172 | 4-wide indents for code, 2-wide indents for nested CPP #defines | |
173 | try hard not to exceed 79-columns | |
174 | ANSI C prototypes | |
175 | uncuddled elses and "K&R" style for indenting control constructs | |
176 | no C++ style (//) comments, most C compilers will choke on them | |
177 | mark places that need to be revisited with XXX (and revisit often!) | |
178 | opening brace lines up with "if" when conditional spans multiple | |
179 | lines; should be at end-of-line otherwise | |
180 | in function definitions, name starts in column 0 (return value is on | |
181 | previous line) | |
182 | single space after keywords that are followed by parens, no space | |
183 | between function name and following paren | |
184 | avoid assignments in conditionals, but if they're unavoidable, use | |
185 | extra paren, e.g. "if (a && (b = c)) ..." | |
186 | "return foo;" rather than "return(foo);" | |
187 | "if (!foo) ..." rather than "if (foo == FALSE) ..." etc. | |
188 | ||
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189 | |
190 | =item Testsuite | |
191 | ||
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192 | When submitting a patch you should make every effort to also include |
193 | an addition to perl's regression tests to properly exercise your | |
194 | patch. Your testsuite additions should generally follow these | |
54aff467 | 195 | guidelines (courtesy of Gurusamy Sarathy <gsar@activestate.com>): |
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196 | |
197 | Know what you're testing. Read the docs, and the source. | |
198 | Tend to fail, not succeed. | |
199 | Interpret results strictly. | |
200 | Use unrelated features (this will flush out bizarre interactions). | |
201 | Use non-standard idioms (otherwise you are not testing TIMTOWTDI). | |
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202 | Avoid using hardcoded test numbers whenever possible (the |
203 | EXPECTED/GOT found in t/op/tie.t is much more maintainable, | |
204 | and gives better failure reports). | |
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205 | Give meaningful error messages when a test fails. |
206 | Avoid using qx// and system() unless you are testing for them. If you | |
207 | do use them, make sure that you cover _all_ perl platforms. | |
208 | Unlink any temporary files you create. | |
209 | Promote unforeseen warnings to errors with $SIG{__WARN__}. | |
54aff467 | 210 | Be sure to use the libraries and modules shipped with the version |
f556e4ac | 211 | being tested, not those that were already installed. |
f4dad39e | 212 | Add comments to the code explaining what you are testing for. |
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213 | Make updating the '1..42' string unnecessary. Or make sure that |
214 | you update it. | |
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215 | Test _all_ behaviors of a given operator, library, or function: |
216 | - All optional arguments | |
217 | - Return values in various contexts (boolean, scalar, list, lvalue) | |
218 | - Use both global and lexical variables | |
219 | - Don't forget the exceptional, pathological cases. | |
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220 | |
221 | =back | |
222 | ||
223 | =item Test your patch | |
224 | ||
225 | Apply your patch to a clean distribution, compile, and run the | |
226 | regression test suite (you did remember to add one for your | |
227 | patch, didn't you). | |
228 | ||
229 | =back | |
230 | ||
231 | =head2 An example patch creation | |
232 | ||
54aff467 | 233 | This should work for most patches: |
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234 | |
235 | cp MANIFEST MANIFEST.old | |
236 | emacs MANIFEST | |
237 | (make changes) | |
238 | cd .. | |
239 | diff -c perl5.008_42/MANIFEST.old perl5.008_42/MANIFEST > mypatch | |
240 | (testing the patch:) | |
241 | mv perl5.008_42/MANIFEST perl5.008_42/MANIFEST.new | |
242 | cp perl5.008_42/MANIFEST.old perl5.008_42/MANIFEST | |
243 | patch -p < mypatch | |
244 | (should succeed) | |
245 | diff perl5.008_42/MANIFEST perl5.008_42/MANIFEST.new | |
246 | (should produce no output) | |
247 | ||
248 | =head2 Submitting your patch | |
249 | ||
250 | =over 4 | |
251 | ||
252 | =item Mailers | |
253 | ||
254 | Please, please, please (get the point? 8-) don't use a mailer that | |
255 | word wraps your patch or that MIME encodes it. Both of these leave | |
256 | the patch essentially worthless to the maintainer. | |
257 | ||
258 | If you have no choice in mailers and no way to get your hands on a | |
54aff467 | 259 | better one there is, of course, a perl solution. Just do this: |
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260 | |
261 | perl -ne 'print pack("u*",$_)' patch > patch.uue | |
262 | ||
263 | and post patch.uue with a note saying to unpack it using | |
264 | ||
265 | perl -ne 'print unpack("u*",$_)' patch.uue > patch | |
266 | ||
267 | =item Subject lines for patches | |
268 | ||
269 | The subject line on your patch should read | |
270 | ||
54aff467 | 271 | [PATCH 5.xxx_xx AREA] Description |
55d729e4 | 272 | |
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273 | where the x's are replaced by the appropriate version number. |
274 | The description should be a very brief but accurate summary of the | |
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275 | problem (don't forget this is an email header). |
276 | ||
54aff467 | 277 | Examples: |
55d729e4 | 278 | |
54aff467 | 279 | [PATCH 5.004_04 DOC] fix minor typos |
55d729e4 | 280 | |
54aff467 | 281 | [PATCH 5.004_99 CORE] New warning for foo() when frobbing |
55d729e4 | 282 | |
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283 | [PATCH 5.005_42 CONFIG] Added support for fribnatz 1.5 |
284 | ||
285 | The name of the file being patched makes for a poor subject line if | |
286 | no other descriptive text accompanies it. | |
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287 | |
288 | =item Where to send your patch | |
289 | ||
54aff467 GS |
290 | If your patch is for a specific bug in the Perl core, it should be sent |
291 | using the perlbug utility. Don't forget to describe the problem and the | |
292 | fix adequately. | |
293 | ||
55d729e4 GS |
294 | If it is a patch to a module that you downloaded from CPAN you should |
295 | submit your patch to that module's author. | |
296 | ||
54aff467 GS |
297 | If your patch addresses one of the items described in perltodo.pod, |
298 | please discuss your approach B<before> you make the patch at | |
299 | <perl5-porters@perl.org>. Be sure to browse the archives of past | |
300 | discussions (see perltodo.pod for archive locations). | |
301 | ||
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302 | =back |
303 | ||
304 | =head2 Applying a patch | |
305 | ||
306 | =over 4 | |
307 | ||
308 | =item General notes on applying patches | |
309 | ||
310 | The following are some general notes on applying a patch | |
311 | to your perl distribution. | |
312 | ||
313 | =over 4 | |
314 | ||
315 | =item patch C<-p> | |
316 | ||
54aff467 GS |
317 | It is generally easier to apply patches with the C<-p N> argument to |
318 | patch (where N is the number of path components to skip in the files | |
319 | found in the headers). This helps reconcile differing paths between | |
320 | the machine the patch was created on and the machine on which it is | |
321 | being applied. | |
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322 | |
323 | =item Cut and paste | |
324 | ||
54aff467 | 325 | B<Never> cut and paste a patch into your editor. This usually clobbers |
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326 | the tabs and confuses patch. |
327 | ||
328 | =item Hand editing patches | |
329 | ||
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330 | Avoid hand editing patches as this almost always screws up the line |
331 | numbers and offsets in the patch, making it useless. | |
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332 | |
333 | =back | |
334 | ||
335 | =back | |
336 | ||
337 | =head2 Final notes | |
338 | ||
339 | If you follow these guidelines it will make everybody's life a little | |
340 | easier. You'll have the satisfaction of having contributed to perl, | |
341 | others will have an easy time using your work, and it should be easier | |
342 | for the maintainers to coordinate the occasionally large numbers of | |
343 | patches received. | |
344 | ||
f556e4ac DG |
345 | Also, just because you're not a brilliant coder doesn't mean that you |
346 | can't contribute. As valuable as code patches are there is always a | |
347 | need for better documentation (especially considering the general | |
348 | level of joy that most programmers feel when forced to sit down and | |
349 | write docs). If all you do is patch the documentation you have still | |
350 | contributed more than the person who sent in an amazing new feature | |
351 | that no one can use because no one understands the code (what I'm | |
352 | getting at is that documentation is both the hardest part to do | |
353 | (because everyone hates doing it) and the most valuable). | |
354 | ||
355 | Mostly, when contributing patches, imagine that it is B<you> receiving | |
356 | hundreds of patches and that it is B<your> responsibility to integrate | |
357 | them into the source. Obviously you'd want the patches to be as easy | |
358 | to apply as possible. Keep that in mind. 8-) | |
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359 | |
360 | =head1 Last Modified | |
361 | ||
f556e4ac DG |
362 | Last modified 21 January 1999 |
363 | Daniel Grisinger <dgris@dimensional.com> | |
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364 | |
365 | =head1 Author and Copyright Information | |
366 | ||
367 | Copyright (c) 1998 Daniel Grisinger | |
368 | ||
369 | Adapted from a posting to perl5-porters by Tim Bunce (Tim.Bunce@ig.co.uk). | |
370 | ||
371 | I'd like to thank the perl5-porters for their suggestions. |