xref: /openbsd-src/gnu/usr.bin/perl/lib/warnings.pm (revision 897fc685943471cf985a0fe38ba076ea6fe74fa5) 
1# -*- buffer-read-only: t -*-
2# !!!!!!!   DO NOT EDIT THIS FILE   !!!!!!!
3# This file is built by regen/warnings.pl.
4# Any changes made here will be lost!
5
6package warnings;
7
8our $VERSION = "1.36";
9
10# Verify that we're called correctly so that warnings will work.
11# Can't use Carp, since Carp uses us!
12# String regexps because constant folding = smaller optree = less memory vs regexp literal
13# see also strict.pm.
14die sprintf "Incorrect use of pragma '%s' at %s line %d.\n", __PACKAGE__, +(caller)[1,2]
15    if __FILE__ !~ ( '(?x) \b     '.__PACKAGE__.'  \.pmc? \z' )
16    && __FILE__ =~ ( '(?x) \b (?i:'.__PACKAGE__.') \.pmc? \z' );
17
18our %Offsets = (
19    # Warnings Categories added in Perl 5.008
20    'all'				=> 0,
21    'closure'				=> 2,
22    'deprecated'			=> 4,
23    'exiting'				=> 6,
24    'glob'				=> 8,
25    'io'				=> 10,
26    'closed'				=> 12,
27    'exec'				=> 14,
28    'layer'				=> 16,
29    'newline'				=> 18,
30    'pipe'				=> 20,
31    'unopened'				=> 22,
32    'misc'				=> 24,
33    'numeric'				=> 26,
34    'once'				=> 28,
35    'overflow'				=> 30,
36    'pack'				=> 32,
37    'portable'				=> 34,
38    'recursion'				=> 36,
39    'redefine'				=> 38,
40    'regexp'				=> 40,
41    'severe'				=> 42,
42    'debugging'				=> 44,
43    'inplace'				=> 46,
44    'internal'				=> 48,
45    'malloc'				=> 50,
46    'signal'				=> 52,
47    'substr'				=> 54,
48    'syntax'				=> 56,
49    'ambiguous'				=> 58,
50    'bareword'				=> 60,
51    'digit'				=> 62,
52    'parenthesis'			=> 64,
53    'precedence'			=> 66,
54    'printf'				=> 68,
55    'prototype'				=> 70,
56    'qw'				=> 72,
57    'reserved'				=> 74,
58    'semicolon'				=> 76,
59    'taint'				=> 78,
60    'threads'				=> 80,
61    'uninitialized'			=> 82,
62    'unpack'				=> 84,
63    'untie'				=> 86,
64    'utf8'				=> 88,
65    'void'				=> 90,
66
67    # Warnings Categories added in Perl 5.011
68    'imprecision'			=> 92,
69    'illegalproto'			=> 94,
70
71    # Warnings Categories added in Perl 5.013
72    'non_unicode'			=> 96,
73    'nonchar'				=> 98,
74    'surrogate'				=> 100,
75
76    # Warnings Categories added in Perl 5.017
77    'experimental'			=> 102,
78    'experimental::lexical_subs'	=> 104,
79    'experimental::regex_sets'		=> 106,
80    'experimental::smartmatch'		=> 108,
81
82    # Warnings Categories added in Perl 5.019
83    'experimental::postderef'		=> 110,
84    'experimental::signatures'		=> 112,
85    'syscalls'				=> 114,
86
87    # Warnings Categories added in Perl 5.021
88    'experimental::bitwise'		=> 116,
89    'experimental::const_attr'		=> 118,
90    'experimental::re_strict'		=> 120,
91    'experimental::refaliasing'		=> 122,
92    'experimental::win32_perlio'	=> 124,
93    'locale'				=> 126,
94    'missing'				=> 128,
95    'redundant'				=> 130,
96);
97
98our %Bits = (
99    'all'				=> "\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x55\x05", # [0..65]
100    'ambiguous'				=> "\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [29]
101    'bareword'				=> "\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [30]
102    'closed'				=> "\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [6]
103    'closure'				=> "\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [1]
104    'debugging'				=> "\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [22]
105    'deprecated'			=> "\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [2]
106    'digit'				=> "\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [31]
107    'exec'				=> "\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [7]
108    'exiting'				=> "\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [3]
109    'experimental'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x55\x51\x15\x00", # [51..56,58..62]
110    'experimental::bitwise'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00", # [58]
111    'experimental::const_attr'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00", # [59]
112    'experimental::lexical_subs'	=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00", # [52]
113    'experimental::postderef'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00", # [55]
114    'experimental::re_strict'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00", # [60]
115    'experimental::refaliasing'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00", # [61]
116    'experimental::regex_sets'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00", # [53]
117    'experimental::signatures'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00", # [56]
118    'experimental::smartmatch'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00", # [54]
119    'experimental::win32_perlio'	=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10\x00", # [62]
120    'glob'				=> "\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [4]
121    'illegalproto'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00", # [47]
122    'imprecision'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00", # [46]
123    'inplace'				=> "\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [23]
124    'internal'				=> "\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [24]
125    'io'				=> "\x00\x54\x55\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00", # [5..11,57]
126    'layer'				=> "\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [8]
127    'locale'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x00", # [63]
128    'malloc'				=> "\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [25]
129    'misc'				=> "\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [12]
130    'missing'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01", # [64]
131    'newline'				=> "\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [9]
132    'non_unicode'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00", # [48]
133    'nonchar'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00", # [49]
134    'numeric'				=> "\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [13]
135    'once'				=> "\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [14]
136    'overflow'				=> "\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [15]
137    'pack'				=> "\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [16]
138    'parenthesis'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00", # [32]
139    'pipe'				=> "\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [10]
140    'portable'				=> "\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [17]
141    'precedence'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00\x00", # [33]
142    'printf'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00", # [34]
143    'prototype'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00", # [35]
144    'qw'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00", # [36]
145    'recursion'				=> "\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [18]
146    'redefine'				=> "\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [19]
147    'redundant'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04", # [65]
148    'regexp'				=> "\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [20]
149    'reserved'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00\x00", # [37]
150    'semicolon'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00", # [38]
151    'severe'				=> "\x00\x00\x00\x00\x00\x54\x05\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [21..25]
152    'signal'				=> "\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [26]
153    'substr'				=> "\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [27]
154    'surrogate'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00", # [50]
155    'syntax'				=> "\x00\x00\x00\x00\x00\x00\x00\x55\x55\x15\x00\x40\x00\x00\x00\x00\x00", # [28..38,47]
156    'syscalls'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00", # [57]
157    'taint'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00", # [39]
158    'threads'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00\x00\x00\x00\x00", # [40]
159    'uninitialized'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00\x00", # [41]
160    'unopened'				=> "\x00\x00\x40\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [11]
161    'unpack'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00", # [42]
162    'untie'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x40\x00\x00\x00\x00\x00\x00", # [43]
163    'utf8'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x15\x00\x00\x00\x00", # [44,48..50]
164    'void'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00", # [45]
165);
166
167our %DeadBits = (
168    'all'				=> "\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\x0a", # [0..65]
169    'ambiguous'				=> "\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [29]
170    'bareword'				=> "\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [30]
171    'closed'				=> "\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [6]
172    'closure'				=> "\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [1]
173    'debugging'				=> "\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [22]
174    'deprecated'			=> "\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [2]
175    'digit'				=> "\x00\x00\x00\x00\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [31]
176    'exec'				=> "\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [7]
177    'exiting'				=> "\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [3]
178    'experimental'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\xaa\xa2\x2a\x00", # [51..56,58..62]
179    'experimental::bitwise'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00", # [58]
180    'experimental::const_attr'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\x00\x00", # [59]
181    'experimental::lexical_subs'	=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00", # [52]
182    'experimental::postderef'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\x00\x00\x00", # [55]
183    'experimental::re_strict'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00", # [60]
184    'experimental::refaliasing'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00", # [61]
185    'experimental::regex_sets'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00", # [53]
186    'experimental::signatures'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00", # [56]
187    'experimental::smartmatch'		=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00", # [54]
188    'experimental::win32_perlio'	=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20\x00", # [62]
189    'glob'				=> "\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [4]
190    'illegalproto'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\x00\x00\x00\x00\x00", # [47]
191    'imprecision'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00", # [46]
192    'inplace'				=> "\x00\x00\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [23]
193    'internal'				=> "\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [24]
194    'io'				=> "\x00\xa8\xaa\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00", # [5..11,57]
195    'layer'				=> "\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [8]
196    'locale'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\x00", # [63]
197    'malloc'				=> "\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [25]
198    'misc'				=> "\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [12]
199    'missing'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02", # [64]
200    'newline'				=> "\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [9]
201    'non_unicode'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00", # [48]
202    'nonchar'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00", # [49]
203    'numeric'				=> "\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [13]
204    'once'				=> "\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [14]
205    'overflow'				=> "\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [15]
206    'pack'				=> "\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [16]
207    'parenthesis'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00", # [32]
208    'pipe'				=> "\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [10]
209    'portable'				=> "\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [17]
210    'precedence'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00\x00", # [33]
211    'printf'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00", # [34]
212    'prototype'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00", # [35]
213    'qw'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00", # [36]
214    'recursion'				=> "\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [18]
215    'redefine'				=> "\x00\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [19]
216    'redundant'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08", # [65]
217    'regexp'				=> "\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [20]
218    'reserved'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00\x00", # [37]
219    'semicolon'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00", # [38]
220    'severe'				=> "\x00\x00\x00\x00\x00\xa8\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [21..25]
221    'signal'				=> "\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [26]
222    'substr'				=> "\x00\x00\x00\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [27]
223    'surrogate'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00", # [50]
224    'syntax'				=> "\x00\x00\x00\x00\x00\x00\x00\xaa\xaa\x2a\x00\x80\x00\x00\x00\x00\x00", # [28..38,47]
225    'syscalls'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00", # [57]
226    'taint'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00\x00", # [39]
227    'threads'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x00\x00\x00\x00\x00", # [40]
228    'uninitialized'			=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00\x00", # [41]
229    'unopened'				=> "\x00\x00\x80\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00", # [11]
230    'unpack'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x20\x00\x00\x00\x00\x00\x00", # [42]
231    'untie'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x80\x00\x00\x00\x00\x00\x00", # [43]
232    'utf8'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x2a\x00\x00\x00\x00", # [44,48..50]
233    'void'				=> "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x08\x00\x00\x00\x00\x00", # [45]
234);
235
236# These are used by various things, including our own tests
237our $NONE				=  "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
238our $DEFAULT				=  "\x10\x01\x00\x00\x00\x50\x04\x00\x00\x00\x00\x00\x00\x55\x51\x55\x00", # [2,58,59,52,55,60,61,53,56,54,62,4,63,22,23,25]
239our $LAST_BIT				=  132 ;
240our $BYTES				=  17 ;
241
242our $All = "" ; vec($All, $Offsets{'all'}, 2) = 3 ;
243
244sub Croaker
245{
246    require Carp; # this initializes %CarpInternal
247    local $Carp::CarpInternal{'warnings'};
248    delete $Carp::CarpInternal{'warnings'};
249    Carp::croak(@_);
250}
251
252sub _bits {
253    my $mask = shift ;
254    my $catmask ;
255    my $fatal = 0 ;
256    my $no_fatal = 0 ;
257
258    foreach my $word ( @_ ) {
259	if ($word eq 'FATAL') {
260	    $fatal = 1;
261	    $no_fatal = 0;
262	}
263	elsif ($word eq 'NONFATAL') {
264	    $fatal = 0;
265	    $no_fatal = 1;
266	}
267	elsif ($catmask = $Bits{$word}) {
268	    $mask |= $catmask ;
269	    $mask |= $DeadBits{$word} if $fatal ;
270	    $mask &= ~($DeadBits{$word}|$All) if $no_fatal ;
271	}
272	else
273	  { Croaker("Unknown warnings category '$word'")}
274    }
275
276    return $mask ;
277}
278
279sub bits
280{
281    # called from B::Deparse.pm
282    push @_, 'all' unless @_ ;
283    return _bits(undef, @_) ;
284}
285
286sub import
287{
288    shift;
289
290    my $mask = ${^WARNING_BITS} // ($^W ? $Bits{all} : $DEFAULT) ;
291
292    if (vec($mask, $Offsets{'all'}, 1)) {
293	$mask |= $Bits{'all'} ;
294	$mask |= $DeadBits{'all'} if vec($mask, $Offsets{'all'}+1, 1);
295    }
296
297    # append 'all' when implied (after a lone "FATAL" or "NONFATAL")
298    push @_, 'all' if @_==1 && ( $_[0] eq 'FATAL' || $_[0] eq 'NONFATAL' );
299
300    # Empty @_ is equivalent to @_ = 'all' ;
301    ${^WARNING_BITS} = @_ ? _bits($mask, @_) : $mask | $Bits{all} ;
302}
303
304sub unimport
305{
306    shift;
307
308    my $catmask ;
309    my $mask = ${^WARNING_BITS} // ($^W ? $Bits{all} : $DEFAULT) ;
310
311    if (vec($mask, $Offsets{'all'}, 1)) {
312	$mask |= $Bits{'all'} ;
313	$mask |= $DeadBits{'all'} if vec($mask, $Offsets{'all'}+1, 1);
314    }
315
316    # append 'all' when implied (empty import list or after a lone "FATAL")
317    push @_, 'all' if !@_ || @_==1 && $_[0] eq 'FATAL';
318
319    foreach my $word ( @_ ) {
320	if ($word eq 'FATAL') {
321	    next;
322	}
323	elsif ($catmask = $Bits{$word}) {
324	    $mask &= ~($catmask | $DeadBits{$word} | $All);
325	}
326	else
327	  { Croaker("Unknown warnings category '$word'")}
328    }
329
330    ${^WARNING_BITS} = $mask ;
331}
332
333my %builtin_type; @builtin_type{qw(SCALAR ARRAY HASH CODE REF GLOB LVALUE Regexp)} = ();
334
335sub MESSAGE () { 4 };
336sub FATAL () { 2 };
337sub NORMAL () { 1 };
338
339sub __chk
340{
341    my $category ;
342    my $offset ;
343    my $isobj = 0 ;
344    my $wanted = shift;
345    my $has_message = $wanted & MESSAGE;
346
347    unless (@_ == 1 || @_ == ($has_message ? 2 : 0)) {
348	my $sub = (caller 1)[3];
349	my $syntax = $has_message ? "[category,] 'message'" : '[category]';
350	Croaker("Usage: $sub($syntax)");
351    }
352
353    my $message = pop if $has_message;
354
355    if (@_) {
356	# check the category supplied.
357	$category = shift ;
358	if (my $type = ref $category) {
359	    Croaker("not an object")
360		if exists $builtin_type{$type};
361	    $category = $type;
362	    $isobj = 1 ;
363	}
364	$offset = $Offsets{$category};
365	Croaker("Unknown warnings category '$category'")
366	    unless defined $offset;
367    }
368    else {
369	$category = (caller(1))[0] ;
370	$offset = $Offsets{$category};
371	Croaker("package '$category' not registered for warnings")
372	    unless defined $offset ;
373    }
374
375    my $i;
376
377    if ($isobj) {
378	my $pkg;
379	$i = 2;
380	while (do { { package DB; $pkg = (caller($i++))[0] } } ) {
381	    last unless @DB::args && $DB::args[0] =~ /^$category=/ ;
382	}
383	$i -= 2 ;
384    }
385    else {
386	$i = _error_loc(); # see where Carp will allocate the error
387    }
388
389    # Default to 0 if caller returns nothing.  Default to $DEFAULT if it
390    # explicitly returns undef.
391    my(@callers_bitmask) = (caller($i))[9] ;
392    my $callers_bitmask =
393	 @callers_bitmask ? $callers_bitmask[0] // $DEFAULT : 0 ;
394
395    my @results;
396    foreach my $type (FATAL, NORMAL) {
397	next unless $wanted & $type;
398
399	push @results, (vec($callers_bitmask, $offset + $type - 1, 1) ||
400			vec($callers_bitmask, $Offsets{'all'} + $type - 1, 1));
401    }
402
403    # &enabled and &fatal_enabled
404    return $results[0] unless $has_message;
405
406    # &warnif, and the category is neither enabled as warning nor as fatal
407    return if $wanted == (NORMAL | FATAL | MESSAGE)
408	&& !($results[0] || $results[1]);
409
410    require Carp;
411    Carp::croak($message) if $results[0];
412    # will always get here for &warn. will only get here for &warnif if the
413    # category is enabled
414    Carp::carp($message);
415}
416
417sub _mkMask
418{
419    my ($bit) = @_;
420    my $mask = "";
421
422    vec($mask, $bit, 1) = 1;
423    return $mask;
424}
425
426sub register_categories
427{
428    my @names = @_;
429
430    for my $name (@names) {
431	if (! defined $Bits{$name}) {
432	    $Bits{$name}     = _mkMask($LAST_BIT);
433	    vec($Bits{'all'}, $LAST_BIT, 1) = 1;
434	    $Offsets{$name}  = $LAST_BIT ++;
435	    foreach my $k (keys %Bits) {
436		vec($Bits{$k}, $LAST_BIT, 1) = 0;
437	    }
438	    $DeadBits{$name} = _mkMask($LAST_BIT);
439	    vec($DeadBits{'all'}, $LAST_BIT++, 1) = 1;
440	}
441    }
442}
443
444sub _error_loc {
445    require Carp;
446    goto &Carp::short_error_loc; # don't introduce another stack frame
447}
448
449sub enabled
450{
451    return __chk(NORMAL, @_);
452}
453
454sub fatal_enabled
455{
456    return __chk(FATAL, @_);
457}
458
459sub warn
460{
461    return __chk(FATAL | MESSAGE, @_);
462}
463
464sub warnif
465{
466    return __chk(NORMAL | FATAL | MESSAGE, @_);
467}
468
469# These are not part of any public interface, so we can delete them to save
470# space.
471delete @warnings::{qw(NORMAL FATAL MESSAGE)};
472
4731;
474__END__
475=head1 NAME
476
477warnings - Perl pragma to control optional warnings
478
479=head1 SYNOPSIS
480
481    use warnings;
482    no warnings;
483
484    use warnings "all";
485    no warnings "all";
486
487    use warnings::register;
488    if (warnings::enabled()) {
489        warnings::warn("some warning");
490    }
491
492    if (warnings::enabled("void")) {
493        warnings::warn("void", "some warning");
494    }
495
496    if (warnings::enabled($object)) {
497        warnings::warn($object, "some warning");
498    }
499
500    warnings::warnif("some warning");
501    warnings::warnif("void", "some warning");
502    warnings::warnif($object, "some warning");
503
504=head1 DESCRIPTION
505
506The C<warnings> pragma gives control over which warnings are enabled in
507which parts of a Perl program.  It's a more flexible alternative for
508both the command line flag B<-w> and the equivalent Perl variable,
509C<$^W>.
510
511This pragma works just like the C<strict> pragma.
512This means that the scope of the warning pragma is limited to the
513enclosing block.  It also means that the pragma setting will not
514leak across files (via C<use>, C<require> or C<do>).  This allows
515authors to independently define the degree of warning checks that will
516be applied to their module.
517
518By default, optional warnings are disabled, so any legacy code that
519doesn't attempt to control the warnings will work unchanged.
520
521All warnings are enabled in a block by either of these:
522
523    use warnings;
524    use warnings 'all';
525
526Similarly all warnings are disabled in a block by either of these:
527
528    no warnings;
529    no warnings 'all';
530
531For example, consider the code below:
532
533    use warnings;
534    my @a;
535    {
536        no warnings;
537	my $b = @a[0];
538    }
539    my $c = @a[0];
540
541The code in the enclosing block has warnings enabled, but the inner
542block has them disabled.  In this case that means the assignment to the
543scalar C<$c> will trip the C<"Scalar value @a[0] better written as $a[0]">
544warning, but the assignment to the scalar C<$b> will not.
545
546=head2 Default Warnings and Optional Warnings
547
548Before the introduction of lexical warnings, Perl had two classes of
549warnings: mandatory and optional.
550
551As its name suggests, if your code tripped a mandatory warning, you
552would get a warning whether you wanted it or not.
553For example, the code below would always produce an C<"isn't numeric">
554warning about the "2:".
555
556    my $a = "2:" + 3;
557
558With the introduction of lexical warnings, mandatory warnings now become
559I<default> warnings.  The difference is that although the previously
560mandatory warnings are still enabled by default, they can then be
561subsequently enabled or disabled with the lexical warning pragma.  For
562example, in the code below, an C<"isn't numeric"> warning will only
563be reported for the C<$a> variable.
564
565    my $a = "2:" + 3;
566    no warnings;
567    my $b = "2:" + 3;
568
569Note that neither the B<-w> flag or the C<$^W> can be used to
570disable/enable default warnings.  They are still mandatory in this case.
571
572=head2 What's wrong with B<-w> and C<$^W>
573
574Although very useful, the big problem with using B<-w> on the command
575line to enable warnings is that it is all or nothing.  Take the typical
576scenario when you are writing a Perl program.  Parts of the code you
577will write yourself, but it's very likely that you will make use of
578pre-written Perl modules.  If you use the B<-w> flag in this case, you
579end up enabling warnings in pieces of code that you haven't written.
580
581Similarly, using C<$^W> to either disable or enable blocks of code is
582fundamentally flawed.  For a start, say you want to disable warnings in
583a block of code.  You might expect this to be enough to do the trick:
584
585     {
586         local ($^W) = 0;
587	 my $a =+ 2;
588	 my $b; chop $b;
589     }
590
591When this code is run with the B<-w> flag, a warning will be produced
592for the C<$a> line:  C<"Reversed += operator">.
593
594The problem is that Perl has both compile-time and run-time warnings.  To
595disable compile-time warnings you need to rewrite the code like this:
596
597     {
598         BEGIN { $^W = 0 }
599	 my $a =+ 2;
600	 my $b; chop $b;
601     }
602
603The other big problem with C<$^W> is the way you can inadvertently
604change the warning setting in unexpected places in your code.  For example,
605when the code below is run (without the B<-w> flag), the second call
606to C<doit> will trip a C<"Use of uninitialized value"> warning, whereas
607the first will not.
608
609    sub doit
610    {
611        my $b; chop $b;
612    }
613
614    doit();
615
616    {
617        local ($^W) = 1;
618        doit()
619    }
620
621This is a side-effect of C<$^W> being dynamically scoped.
622
623Lexical warnings get around these limitations by allowing finer control
624over where warnings can or can't be tripped.
625
626=head2 Controlling Warnings from the Command Line
627
628There are three Command Line flags that can be used to control when
629warnings are (or aren't) produced:
630
631=over 5
632
633=item B<-w>
634X<-w>
635
636This is  the existing flag.  If the lexical warnings pragma is B<not>
637used in any of you code, or any of the modules that you use, this flag
638will enable warnings everywhere.  See L<Backward Compatibility> for
639details of how this flag interacts with lexical warnings.
640
641=item B<-W>
642X<-W>
643
644If the B<-W> flag is used on the command line, it will enable all warnings
645throughout the program regardless of whether warnings were disabled
646locally using C<no warnings> or C<$^W =0>.
647This includes all files that get
648included via C<use>, C<require> or C<do>.
649Think of it as the Perl equivalent of the "lint" command.
650
651=item B<-X>
652X<-X>
653
654Does the exact opposite to the B<-W> flag, i.e. it disables all warnings.
655
656=back
657
658=head2 Backward Compatibility
659
660If you are used to working with a version of Perl prior to the
661introduction of lexically scoped warnings, or have code that uses both
662lexical warnings and C<$^W>, this section will describe how they interact.
663
664How Lexical Warnings interact with B<-w>/C<$^W>:
665
666=over 5
667
668=item 1.
669
670If none of the three command line flags (B<-w>, B<-W> or B<-X>) that
671control warnings is used and neither C<$^W> nor the C<warnings> pragma
672are used, then default warnings will be enabled and optional warnings
673disabled.
674This means that legacy code that doesn't attempt to control the warnings
675will work unchanged.
676
677=item 2.
678
679The B<-w> flag just sets the global C<$^W> variable as in 5.005.  This
680means that any legacy code that currently relies on manipulating C<$^W>
681to control warning behavior will still work as is.
682
683=item 3.
684
685Apart from now being a boolean, the C<$^W> variable operates in exactly
686the same horrible uncontrolled global way, except that it cannot
687disable/enable default warnings.
688
689=item 4.
690
691If a piece of code is under the control of the C<warnings> pragma,
692both the C<$^W> variable and the B<-w> flag will be ignored for the
693scope of the lexical warning.
694
695=item 5.
696
697The only way to override a lexical warnings setting is with the B<-W>
698or B<-X> command line flags.
699
700=back
701
702The combined effect of 3 & 4 is that it will allow code which uses
703the C<warnings> pragma to control the warning behavior of $^W-type
704code (using a C<local $^W=0>) if it really wants to, but not vice-versa.
705
706=head2 Category Hierarchy
707X<warning, categories>
708
709A hierarchy of "categories" have been defined to allow groups of warnings
710to be enabled/disabled in isolation.
711
712The current hierarchy is:
713
714    all -+
715         |
716         +- closure
717         |
718         +- deprecated
719         |
720         +- exiting
721         |
722         +- experimental --+
723         |                 |
724         |                 +- experimental::bitwise
725         |                 |
726         |                 +- experimental::const_attr
727         |                 |
728         |                 +- experimental::lexical_subs
729         |                 |
730         |                 +- experimental::postderef
731         |                 |
732         |                 +- experimental::re_strict
733         |                 |
734         |                 +- experimental::refaliasing
735         |                 |
736         |                 +- experimental::regex_sets
737         |                 |
738         |                 +- experimental::signatures
739         |                 |
740         |                 +- experimental::smartmatch
741         |                 |
742         |                 +- experimental::win32_perlio
743         |
744         +- glob
745         |
746         +- imprecision
747         |
748         +- io ------------+
749         |                 |
750         |                 +- closed
751         |                 |
752         |                 +- exec
753         |                 |
754         |                 +- layer
755         |                 |
756         |                 +- newline
757         |                 |
758         |                 +- pipe
759         |                 |
760         |                 +- syscalls
761         |                 |
762         |                 +- unopened
763         |
764         +- locale
765         |
766         +- misc
767         |
768         +- missing
769         |
770         +- numeric
771         |
772         +- once
773         |
774         +- overflow
775         |
776         +- pack
777         |
778         +- portable
779         |
780         +- recursion
781         |
782         +- redefine
783         |
784         +- redundant
785         |
786         +- regexp
787         |
788         +- severe --------+
789         |                 |
790         |                 +- debugging
791         |                 |
792         |                 +- inplace
793         |                 |
794         |                 +- internal
795         |                 |
796         |                 +- malloc
797         |
798         +- signal
799         |
800         +- substr
801         |
802         +- syntax --------+
803         |                 |
804         |                 +- ambiguous
805         |                 |
806         |                 +- bareword
807         |                 |
808         |                 +- digit
809         |                 |
810         |                 +- illegalproto
811         |                 |
812         |                 +- parenthesis
813         |                 |
814         |                 +- precedence
815         |                 |
816         |                 +- printf
817         |                 |
818         |                 +- prototype
819         |                 |
820         |                 +- qw
821         |                 |
822         |                 +- reserved
823         |                 |
824         |                 +- semicolon
825         |
826         +- taint
827         |
828         +- threads
829         |
830         +- uninitialized
831         |
832         +- unpack
833         |
834         +- untie
835         |
836         +- utf8 ----------+
837         |                 |
838         |                 +- non_unicode
839         |                 |
840         |                 +- nonchar
841         |                 |
842         |                 +- surrogate
843         |
844         +- void
845
846Just like the "strict" pragma any of these categories can be combined
847
848    use warnings qw(void redefine);
849    no warnings qw(io syntax untie);
850
851Also like the "strict" pragma, if there is more than one instance of the
852C<warnings> pragma in a given scope the cumulative effect is additive.
853
854    use warnings qw(void); # only "void" warnings enabled
855    ...
856    use warnings qw(io);   # only "void" & "io" warnings enabled
857    ...
858    no warnings qw(void);  # only "io" warnings enabled
859
860To determine which category a specific warning has been assigned to see
861L<perldiag>.
862
863Note: Before Perl 5.8.0, the lexical warnings category "deprecated" was a
864sub-category of the "syntax" category.  It is now a top-level category
865in its own right.
866
867Note: Before 5.21.0, the "missing" lexical warnings category was
868internally defined to be the same as the "uninitialized" category. It
869is now a top-level category in its own right.
870
871=head2 Fatal Warnings
872X<warning, fatal>
873
874The presence of the word "FATAL" in the category list will escalate
875warnings in those categories into fatal errors in that lexical scope.
876
877B<NOTE:> FATAL warnings should be used with care, particularly
878C<< FATAL => 'all' >>.
879
880Libraries using L<warnings::warn|/FUNCTIONS> for custom warning categories
881generally don't expect L<warnings::warn|/FUNCTIONS> to be fatal and can wind up
882in an unexpected state as a result.  For XS modules issuing categorized
883warnings, such unanticipated exceptions could also expose memory leak bugs.
884
885Moreover, the Perl interpreter itself has had serious bugs involving
886fatalized warnings.  For a summary of resolved and unresolved problems as
887of January 2015, please see
888L<this perl5-porters post|http://www.nntp.perl.org/group/perl.perl5.porters/2015/01/msg225235.html>.
889
890While some developers find fatalizing some warnings to be a useful
891defensive programming technique, using C<< FATAL => 'all' >> to fatalize
892all possible warning categories -- including custom ones -- is particularly
893risky.  Therefore, the use of C<< FATAL => 'all' >> is
894L<discouraged|perlpolicy/discouraged>.
895
896The L<strictures|strictures/VERSION-2> module on CPAN offers one example of
897a warnings subset that the module's authors believe is relatively safe to
898fatalize.
899
900B<NOTE:> users of FATAL warnings, especially those using
901C<< FATAL => 'all' >>, should be fully aware that they are risking future
902portability of their programs by doing so.  Perl makes absolutely no
903commitments to not introduce new warnings or warnings categories in the
904future; indeed, we explicitly reserve the right to do so.  Code that may
905not warn now may warn in a future release of Perl if the Perl5 development
906team deems it in the best interests of the community to do so.  Should code
907using FATAL warnings break due to the introduction of a new warning we will
908NOT consider it an incompatible change.  Users of FATAL warnings should
909take special caution during upgrades to check to see if their code triggers
910any new warnings and should pay particular attention to the fine print of
911the documentation of the features they use to ensure they do not exploit
912features that are documented as risky, deprecated, or unspecified, or where
913the documentation says "so don't do that", or anything with the same sense
914and spirit.  Use of such features in combination with FATAL warnings is
915ENTIRELY AT THE USER'S RISK.
916
917The following documentation describes how to use FATAL warnings but the
918perl5 porters strongly recommend that you understand the risks before doing
919so, especially for library code intended for use by others, as there is no
920way for downstream users to change the choice of fatal categories.
921
922In the code below, the use of C<time>, C<length>
923and C<join> can all produce a C<"Useless use of xxx in void context">
924warning.
925
926    use warnings;
927
928    time;
929
930    {
931        use warnings FATAL => qw(void);
932        length "abc";
933    }
934
935    join "", 1,2,3;
936
937    print "done\n";
938
939When run it produces this output
940
941    Useless use of time in void context at fatal line 3.
942    Useless use of length in void context at fatal line 7.
943
944The scope where C<length> is used has escalated the C<void> warnings
945category into a fatal error, so the program terminates immediately when it
946encounters the warning.
947
948To explicitly turn off a "FATAL" warning you just disable the warning
949it is associated with.  So, for example, to disable the "void" warning
950in the example above, either of these will do the trick:
951
952    no warnings qw(void);
953    no warnings FATAL => qw(void);
954
955If you want to downgrade a warning that has been escalated into a fatal
956error back to a normal warning, you can use the "NONFATAL" keyword.  For
957example, the code below will promote all warnings into fatal errors,
958except for those in the "syntax" category.
959
960    use warnings FATAL => 'all', NONFATAL => 'syntax';
961
962As of Perl 5.20, instead of C<< use warnings FATAL => 'all'; >> you can
963use:
964
965   use v5.20;       # Perl 5.20 or greater is required for the following
966   use warnings 'FATAL';  # short form of "use warnings FATAL => 'all';"
967
968If you want your program to be compatible with versions of Perl before
9695.20, you must use C<< use warnings FATAL => 'all'; >> instead.  (In
970previous versions of Perl, the behavior of the statements
971C<< use warnings 'FATAL'; >>, C<< use warnings 'NONFATAL'; >> and
972C<< no warnings 'FATAL'; >> was unspecified; they did not behave as if
973they included the C<< => 'all' >> portion.  As of 5.20, they do.)
974
975=head2 Reporting Warnings from a Module
976X<warning, reporting> X<warning, registering>
977
978The C<warnings> pragma provides a number of functions that are useful for
979module authors.  These are used when you want to report a module-specific
980warning to a calling module has enabled warnings via the C<warnings>
981pragma.
982
983Consider the module C<MyMod::Abc> below.
984
985    package MyMod::Abc;
986
987    use warnings::register;
988
989    sub open {
990        my $path = shift;
991        if ($path !~ m#^/#) {
992            warnings::warn("changing relative path to /var/abc")
993                if warnings::enabled();
994            $path = "/var/abc/$path";
995        }
996    }
997
998    1;
999
1000The call to C<warnings::register> will create a new warnings category
1001called "MyMod::Abc", i.e. the new category name matches the current
1002package name.  The C<open> function in the module will display a warning
1003message if it gets given a relative path as a parameter.  This warnings
1004will only be displayed if the code that uses C<MyMod::Abc> has actually
1005enabled them with the C<warnings> pragma like below.
1006
1007    use MyMod::Abc;
1008    use warnings 'MyMod::Abc';
1009    ...
1010    abc::open("../fred.txt");
1011
1012It is also possible to test whether the pre-defined warnings categories are
1013set in the calling module with the C<warnings::enabled> function.  Consider
1014this snippet of code:
1015
1016    package MyMod::Abc;
1017
1018    sub open {
1019        if (warnings::enabled("deprecated")) {
1020            warnings::warn("deprecated",
1021                           "open is deprecated, use new instead");
1022        }
1023        new(@_);
1024    }
1025
1026    sub new
1027    ...
1028    1;
1029
1030The function C<open> has been deprecated, so code has been included to
1031display a warning message whenever the calling module has (at least) the
1032"deprecated" warnings category enabled.  Something like this, say.
1033
1034    use warnings 'deprecated';
1035    use MyMod::Abc;
1036    ...
1037    MyMod::Abc::open($filename);
1038
1039Either the C<warnings::warn> or C<warnings::warnif> function should be
1040used to actually display the warnings message.  This is because they can
1041make use of the feature that allows warnings to be escalated into fatal
1042errors.  So in this case
1043
1044    use MyMod::Abc;
1045    use warnings FATAL => 'MyMod::Abc';
1046    ...
1047    MyMod::Abc::open('../fred.txt');
1048
1049the C<warnings::warnif> function will detect this and die after
1050displaying the warning message.
1051
1052The three warnings functions, C<warnings::warn>, C<warnings::warnif>
1053and C<warnings::enabled> can optionally take an object reference in place
1054of a category name.  In this case the functions will use the class name
1055of the object as the warnings category.
1056
1057Consider this example:
1058
1059    package Original;
1060
1061    no warnings;
1062    use warnings::register;
1063
1064    sub new
1065    {
1066        my $class = shift;
1067        bless [], $class;
1068    }
1069
1070    sub check
1071    {
1072        my $self = shift;
1073        my $value = shift;
1074
1075        if ($value % 2 && warnings::enabled($self))
1076          { warnings::warn($self, "Odd numbers are unsafe") }
1077    }
1078
1079    sub doit
1080    {
1081        my $self = shift;
1082        my $value = shift;
1083        $self->check($value);
1084        # ...
1085    }
1086
1087    1;
1088
1089    package Derived;
1090
1091    use warnings::register;
1092    use Original;
1093    our @ISA = qw( Original );
1094    sub new
1095    {
1096        my $class = shift;
1097        bless [], $class;
1098    }
1099
1100
1101    1;
1102
1103The code below makes use of both modules, but it only enables warnings from
1104C<Derived>.
1105
1106    use Original;
1107    use Derived;
1108    use warnings 'Derived';
1109    my $a = Original->new();
1110    $a->doit(1);
1111    my $b = Derived->new();
1112    $a->doit(1);
1113
1114When this code is run only the C<Derived> object, C<$b>, will generate
1115a warning.
1116
1117    Odd numbers are unsafe at main.pl line 7
1118
1119Notice also that the warning is reported at the line where the object is first
1120used.
1121
1122When registering new categories of warning, you can supply more names to
1123warnings::register like this:
1124
1125    package MyModule;
1126    use warnings::register qw(format precision);
1127
1128    ...
1129
1130    warnings::warnif('MyModule::format', '...');
1131
1132=head1 FUNCTIONS
1133
1134=over 4
1135
1136=item use warnings::register
1137
1138Creates a new warnings category with the same name as the package where
1139the call to the pragma is used.
1140
1141=item warnings::enabled()
1142
1143Use the warnings category with the same name as the current package.
1144
1145Return TRUE if that warnings category is enabled in the calling module.
1146Otherwise returns FALSE.
1147
1148=item warnings::enabled($category)
1149
1150Return TRUE if the warnings category, C<$category>, is enabled in the
1151calling module.
1152Otherwise returns FALSE.
1153
1154=item warnings::enabled($object)
1155
1156Use the name of the class for the object reference, C<$object>, as the
1157warnings category.
1158
1159Return TRUE if that warnings category is enabled in the first scope
1160where the object is used.
1161Otherwise returns FALSE.
1162
1163=item warnings::fatal_enabled()
1164
1165Return TRUE if the warnings category with the same name as the current
1166package has been set to FATAL in the calling module.
1167Otherwise returns FALSE.
1168
1169=item warnings::fatal_enabled($category)
1170
1171Return TRUE if the warnings category C<$category> has been set to FATAL in
1172the calling module.
1173Otherwise returns FALSE.
1174
1175=item warnings::fatal_enabled($object)
1176
1177Use the name of the class for the object reference, C<$object>, as the
1178warnings category.
1179
1180Return TRUE if that warnings category has been set to FATAL in the first
1181scope where the object is used.
1182Otherwise returns FALSE.
1183
1184=item warnings::warn($message)
1185
1186Print C<$message> to STDERR.
1187
1188Use the warnings category with the same name as the current package.
1189
1190If that warnings category has been set to "FATAL" in the calling module
1191then die. Otherwise return.
1192
1193=item warnings::warn($category, $message)
1194
1195Print C<$message> to STDERR.
1196
1197If the warnings category, C<$category>, has been set to "FATAL" in the
1198calling module then die. Otherwise return.
1199
1200=item warnings::warn($object, $message)
1201
1202Print C<$message> to STDERR.
1203
1204Use the name of the class for the object reference, C<$object>, as the
1205warnings category.
1206
1207If that warnings category has been set to "FATAL" in the scope where C<$object>
1208is first used then die. Otherwise return.
1209
1210
1211=item warnings::warnif($message)
1212
1213Equivalent to:
1214
1215    if (warnings::enabled())
1216      { warnings::warn($message) }
1217
1218=item warnings::warnif($category, $message)
1219
1220Equivalent to:
1221
1222    if (warnings::enabled($category))
1223      { warnings::warn($category, $message) }
1224
1225=item warnings::warnif($object, $message)
1226
1227Equivalent to:
1228
1229    if (warnings::enabled($object))
1230      { warnings::warn($object, $message) }
1231
1232=item warnings::register_categories(@names)
1233
1234This registers warning categories for the given names and is primarily for
1235use by the warnings::register pragma.
1236
1237=back
1238
1239See also L<perlmodlib/Pragmatic Modules> and L<perldiag>.
1240
1241=cut
1242
1243# ex: set ro:
1244