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a0d0e21e | 1 | package Carp; |
8c3d9721 DM |
2 | |
3 | our $VERSION = '1.05'; | |
29ddba3b DM |
4 | # this file is an utra-lightweight stub. The first time a function is |
5 | # called, Carp::Heavy is loaded, and the real short/longmessmess_jmp | |
6 | # subs are installed | |
b75c8c73 | 7 | |
8c3d9721 DM |
8 | our $MaxEvalLen = 0; |
9 | our $Verbose = 0; | |
10 | our $CarpLevel = 0; | |
11 | our $MaxArgLen = 64; # How much of each argument to print. 0 = all. | |
12 | our $MaxArgNums = 8; # How many arguments to print. 0 = all. | |
748a9306 | 13 | |
a0d0e21e | 14 | require Exporter; |
8c3d9721 DM |
15 | our @ISA = ('Exporter'); |
16 | our @EXPORT = qw(confess croak carp); | |
17 | our @EXPORT_OK = qw(cluck verbose longmess shortmess); | |
18 | our @EXPORT_FAIL = qw(verbose); # hook to enable verbose mode | |
af80c6a7 | 19 | |
af80c6a7 JH |
20 | # if the caller specifies verbose usage ("perl -MCarp=verbose script.pl") |
21 | # then the following method will be called by the Exporter which knows | |
22 | # to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word | |
23 | # 'verbose'. | |
24 | ||
29ddba3b | 25 | sub export_fail { shift; $Verbose = shift if $_[0] eq 'verbose'; @_ } |
7b8d334a | 26 | |
29ddba3b DM |
27 | # fixed hooks for stashes to point to |
28 | sub longmess { goto &longmess_jmp } | |
29 | sub shortmess { goto &shortmess_jmp } | |
30 | # these two are replaced when Carp::Heavy is loaded | |
090656d2 DM |
31 | sub longmess_jmp { |
32 | local($@, $!); | |
33 | eval { require Carp::Heavy }; | |
34 | return $@ if $@; | |
35 | goto &longmess_jmp; | |
36 | } | |
37 | sub shortmess_jmp { | |
38 | local($@, $!); | |
39 | eval { require Carp::Heavy }; | |
40 | return $@ if $@; | |
41 | goto &shortmess_jmp; | |
42 | } | |
7b8d334a GS |
43 | |
44 | sub croak { die shortmess @_ } | |
45 | sub confess { die longmess @_ } | |
46 | sub carp { warn shortmess @_ } | |
47 | sub cluck { warn longmess @_ } | |
a0d0e21e | 48 | |
748a9306 | 49 | 1; |
0cda2667 DM |
50 | __END__ |
51 | ||
52 | =head1 NAME | |
53 | ||
54 | carp - warn of errors (from perspective of caller) | |
55 | ||
56 | cluck - warn of errors with stack backtrace | |
57 | (not exported by default) | |
58 | ||
59 | croak - die of errors (from perspective of caller) | |
60 | ||
61 | confess - die of errors with stack backtrace | |
62 | ||
63 | shortmess - return the message that carp and croak produce | |
64 | ||
65 | longmess - return the message that cluck and confess produce | |
66 | ||
67 | =head1 SYNOPSIS | |
68 | ||
69 | use Carp; | |
70 | croak "We're outta here!"; | |
71 | ||
72 | use Carp qw(cluck); | |
73 | cluck "This is how we got here!"; | |
74 | ||
75 | print FH Carp::shortmess("This will have caller's details added"); | |
76 | print FH Carp::longmess("This will have stack backtrace added"); | |
77 | ||
78 | =head1 DESCRIPTION | |
79 | ||
80 | The Carp routines are useful in your own modules because | |
81 | they act like die() or warn(), but with a message which is more | |
82 | likely to be useful to a user of your module. In the case of | |
83 | cluck, confess, and longmess that context is a summary of every | |
84 | call in the call-stack. For a shorter message you can use carp, | |
85 | croak or shortmess which report the error as being from where | |
86 | your module was called. There is no guarantee that that is where | |
87 | the error was, but it is a good educated guess. | |
88 | ||
89 | You can also alter the way the output and logic of C<Carp> works, by | |
90 | changing some global variables in the C<Carp> namespace. See the | |
91 | section on C<GLOBAL VARIABLES> below. | |
92 | ||
93 | Here is a more complete description of how shortmess works. What | |
94 | it does is search the call-stack for a function call stack where | |
95 | it hasn't been told that there shouldn't be an error. If every | |
96 | call is marked safe, it then gives up and gives a full stack | |
97 | backtrace instead. In other words it presumes that the first likely | |
98 | looking potential suspect is guilty. Its rules for telling whether | |
99 | a call shouldn't generate errors work as follows: | |
100 | ||
101 | =over 4 | |
102 | ||
103 | =item 1. | |
104 | ||
105 | Any call from a package to itself is safe. | |
106 | ||
107 | =item 2. | |
108 | ||
109 | Packages claim that there won't be errors on calls to or from | |
110 | packages explicitly marked as safe by inclusion in @CARP_NOT, or | |
111 | (if that array is empty) @ISA. The ability to override what | |
112 | @ISA says is new in 5.8. | |
113 | ||
114 | =item 3. | |
115 | ||
116 | The trust in item 2 is transitive. If A trusts B, and B | |
117 | trusts C, then A trusts C. So if you do not override @ISA | |
118 | with @CARP_NOT, then this trust relationship is identical to, | |
119 | "inherits from". | |
120 | ||
121 | =item 4. | |
122 | ||
123 | Any call from an internal Perl module is safe. (Nothing keeps | |
124 | user modules from marking themselves as internal to Perl, but | |
125 | this practice is discouraged.) | |
126 | ||
127 | =item 5. | |
128 | ||
129 | Any call to Carp is safe. (This rule is what keeps it from | |
130 | reporting the error where you call carp/croak/shortmess.) | |
131 | ||
132 | =back | |
133 | ||
134 | =head2 Forcing a Stack Trace | |
135 | ||
136 | As a debugging aid, you can force Carp to treat a croak as a confess | |
137 | and a carp as a cluck across I<all> modules. In other words, force a | |
138 | detailed stack trace to be given. This can be very helpful when trying | |
139 | to understand why, or from where, a warning or error is being generated. | |
140 | ||
141 | This feature is enabled by 'importing' the non-existent symbol | |
142 | 'verbose'. You would typically enable it by saying | |
143 | ||
144 | perl -MCarp=verbose script.pl | |
145 | ||
146 | or by including the string C<MCarp=verbose> in the PERL5OPT | |
147 | environment variable. | |
148 | ||
149 | Alternately, you can set the global variable C<$Carp::Verbose> to true. | |
150 | See the C<GLOBAL VARIABLES> section below. | |
151 | ||
152 | =head1 GLOBAL VARIABLES | |
153 | ||
154 | =head2 $Carp::CarpLevel | |
155 | ||
156 | This variable determines how many call frames are to be skipped when | |
157 | reporting where an error occurred on a call to one of C<Carp>'s | |
158 | functions. For example: | |
159 | ||
160 | $Carp::CarpLevel = 1; | |
161 | sub bar { .... or _error('Wrong input') } | |
162 | sub _error { Carp::carp(@_) } | |
163 | ||
164 | This would make Carp report the error as coming from C<bar>'s caller, | |
165 | rather than from C<_error>'s caller, as it normally would. | |
166 | ||
167 | Defaults to C<0>. | |
168 | ||
169 | =head2 $Carp::MaxEvalLen | |
170 | ||
171 | This variable determines how many characters of a string-eval are to | |
172 | be shown in the output. Use a value of C<0> to show all text. | |
173 | ||
174 | Defaults to C<0>. | |
175 | ||
176 | =head2 $Carp::MaxArgLen | |
177 | ||
178 | This variable determines how many characters of each argument to a | |
179 | function to print. Use a value of C<0> to show the full length of the | |
180 | argument. | |
181 | ||
182 | Defaults to C<64>. | |
183 | ||
184 | =head2 $Carp::MaxArgNums | |
185 | ||
186 | This variable determines how many arguments to each function to show. | |
187 | Use a value of C<0> to show all arguments to a function call. | |
188 | ||
189 | Defaults to C<8>. | |
190 | ||
191 | =head2 $Carp::Verbose | |
192 | ||
193 | This variable makes C<Carp> use the C<longmess> function at all times. | |
194 | This effectively means that all calls to C<carp> become C<cluck> and | |
195 | all calls to C<croak> become C<confess>. | |
196 | ||
197 | Note, this is analogous to using C<use Carp 'verbose'>. | |
198 | ||
199 | Defaults to C<0>. | |
200 | ||
0cda2667 DM |
201 | =head1 BUGS |
202 | ||
203 | The Carp routines don't handle exception objects currently. | |
204 | If called with a first argument that is a reference, they simply | |
205 | call die() or warn(), as appropriate. | |
206 |