1strictures(3) User Contributed Perl Documentation strictures(3)
2
6 strictures - Turn on strict and make most warnings fatal
7
9 use strictures 2;
10 is equivalent to
12 use strict;
14 use warnings FATAL => 'all';
15 use warnings NONFATAL => qw(
16 exec
17 recursion
18 internal
19 malloc
20 newline
21 experimental
22 deprecated
23 portable
24 );
25 no warnings 'once';
26 except when called from a file which matches:
28 (caller)[1] =~ /^(?:t|xt|lib|blib)[\\\/]/
30 and when either ".git", ".svn", ".hg", or ".bzr" is present in the
32 current directory (with the intention of only forcing extra tests on
33 the author side) -- or when ".git", ".svn", ".hg", or ".bzr" is present
34 two directories up along with "dist.ini" (which would indicate we are
35 in a "dzil test" operation, via Dist::Zilla) -- or when the
36 "PERL_STRICTURES_EXTRA" environment variable is set, in which case it
37 also does the equivalent of
38 no indirect 'fatal';
40 no multidimensional;
41 no bareword::filehandles;
42 Note that "PERL_STRICTURES_EXTRA" may at some point add even more
44 tests, with only a minor version increase, but any changes to the
45 effect of "use strictures" in normal mode will involve a major version
46 bump.
47 If any of the extra testing modules are not present, strictures will
49 complain loudly, once, via warn(), and then shut up. But you really
50 should consider installing them, they're all great anti-footgun tools.
51
53 I've been writing the equivalent of this module at the top of my code
54 for about a year now. I figured it was time to make it shorter.
55 Things like the importer in "use Moose" don't help me because they turn
57 warnings on but don't make them fatal -- which from my point of view is
58 useless because I want an exception to tell me my code isn't warnings-
59 clean.
60 Any time I see a warning from my code, that indicates a mistake.
62 Any time my code encounters a mistake, I want a crash -- not spew to
64 STDERR and then unknown (and probably undesired) subsequent behaviour.
65 I also want to ensure that obvious coding mistakes, like indirect
67 object syntax (and not so obvious mistakes that cause things to
68 accidentally compile as such) get caught, but not at the cost of an XS
69 dependency and not at the cost of blowing things up on another machine.
70 Therefore, strictures turns on additional checking, but only when it
72 thinks it's running in a test file in a VCS checkout -- although if
73 this causes undesired behaviour this can be overridden by setting the
74 "PERL_STRICTURES_EXTRA" environment variable.
75 If additional useful author side checks come to mind, I'll add them to
77 the "PERL_STRICTURES_EXTRA" code path only -- this will result in a
78 minor version increase (e.g. 1.000000 to 1.001000 (1.1.0) or similar).
79 Any fixes only to the mechanism of this code will result in a sub-
80 version increase (e.g. 1.000000 to 1.000001 (1.0.1)).
81
83 strictures does not enable fatal warnings for all categories.
84 exec
86 Includes a warning that can cause your program to continue running
87 unintentionally after an internal fork. Not safe to fatalize.
88 recursion
90 Infinite recursion will end up overflowing the stack eventually
91 anyway.
92 internal
94 Triggers deep within perl, in places that are not safe to trap.
95 malloc
97 Triggers deep within perl, in places that are not safe to trap.
98 newline
100 Includes a warning for using stat on a valid but suspect filename,
101 ending in a newline.
102 experimental
104 Experimental features are used intentionally.
105 deprecated
107 Deprecations will inherently be added to in the future in
108 unexpected ways, so making them fatal won't be reliable.
109 portable
111 Doesn't indicate an actual problem with the program, only that it
112 may not behave properly if run on a different machine.
113 once
115 Can't be fatalized. Also triggers very inconsistently, so we just
116 disable it.
117
119 Depending on the version of strictures requested, different warnings
120 will be enabled. If no specific version is requested, the current
121 version's behavior will be used. Versions can be requested using
122 perl's standard mechanism:
123 use strictures 2;
125 Or, by passing in a "version" option:
127 use strictures version => 2;
129 VERSION 2
131 Equivalent to:
132 use strict;
134 use warnings FATAL => 'all';
135 use warnings NONFATAL => qw(
136 exec
137 recursion
138 internal
139 malloc
140 newline
141 experimental
142 deprecated
143 portable
144 );
145 no warnings 'once';
146 # and if in dev mode:
148 no indirect 'fatal';
149 no multidimensional;
150 no bareword::filehandles;
151 Additionally, any warnings created by modules using warnings::register
153 or warnings::register_categories() will not be fatalized.
154 VERSION 1
156 Equivalent to:
157 use strict;
159 use warnings FATAL => 'all';
160 # and if in dev mode:
161 no indirect 'fatal';
162 no multidimensional;
163 no bareword::filehandles;
164
166 import
167 This method does the setup work described above in "DESCRIPTION".
168 Optionally accepts a "version" option to request a specific version's
169 behavior.
170 VERSION
172 This method traps the "strictures->VERSION(1)" call produced by a use
173 line with a version number on it and does the version check.
174
176 Every so often, somebody complains that they're deploying via "git
177 pull" and that they don't want strictures to enable itself in this case
178 -- and that setting "PERL_STRICTURES_EXTRA" to 0 isn't acceptable
179 (additional ways to disable extra testing would be welcome but the
180 discussion never seems to get that far).
181 In order to allow us to skip a couple of stages and get straight to a
183 productive conversation, here's my current rationale for turning the
184 extra testing on via a heuristic:
185 The extra testing is all stuff that only ever blows up at compile time;
187 this is intentional. So the oft-raised concern that it's different code
188 being tested is only sort of the case -- none of the modules involved
189 affect the final optree to my knowledge, so the author gets some
190 additional compile time crashes which he/she then fixes, and the rest
191 of the testing is completely valid for all environments.
192 The point of the extra testing -- especially "no indirect" -- is to
194 catch mistakes that newbie users won't even realise are mistakes
195 without help. For example,
196 foo { ... };
198 where foo is an & prototyped sub that you forgot to import -- this is
200 pernicious to track down since all seems fine until it gets called and
201 you get a crash. Worse still, you can fail to have imported it due to a
202 circular require, at which point you have a load order dependent bug
203 which I've seen before now only show up in production due to tiny
204 differences between the production and the development environment. I
205 wrote <http://shadow.cat/blog/matt-s-trout/indirect-but-still-fatal/>
206 to explain this particular problem before strictures itself existed.
207 As such, in my experience so far strictures' extra testing has avoided
209 production versus development differences, not caused them.
210 Additionally, strictures' policy is very much "try and provide as much
212 protection as possible for newbies -- who won't think about whether
213 there's an option to turn on or not" -- so having only the environment
214 variable is not sufficient to achieve that (I get to explain that you
215 need to add "use strict" at least once a week on freenode #perl --
216 newbies sometimes completely skip steps because they don't understand
217 that that step is important).
218 I make no claims that the heuristic is perfect -- it's already been
220 evolved significantly over time, especially for 1.004 where we changed
221 things to ensure it only fires on files in your checkout (rather than
222 strictures-using modules you happened to have installed, which was just
223 silly). However, I hope the above clarifies why a heuristic approach is
224 not only necessary but desirable from a point of view of providing new
225 users with as much safety as possible, and will allow any future
226 discussion on the subject to focus on "how do we minimise annoyance to
227 people deploying from checkouts intentionally".
228
230 • indirect
231 • multidimensional
233 • bareword::filehandles
235
237 IRC channel
238 irc.perl.org #toolchain
239 (or bug 'mst' in query on there or freenode)
241 Git repository
243 Gitweb is on http://git.shadowcat.co.uk/ and the clone URL is:
244 git clone git://git.shadowcat.co.uk/p5sagit/strictures.git
246 The web interface to the repository is at:
248 http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=p5sagit/strictures.git
250
252 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
253
255 Karen Etheridge (cpan:ETHER) <ether@cpan.org>
256 Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@gmail.com>
258 haarg - Graham Knop (cpan:HAARG) <haarg@haarg.org>
260
262 Copyright (c) 2010 the strictures "AUTHOR" and "CONTRIBUTORS" as listed
263 above.
264
266 This library is free software and may be distributed under the same
267 terms as perl itself.
268perl v5.38.0 2023-07-21 strictures(3)