[14489] | 1 | package Carp;
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| 2 |
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| 3 | our $VERSION = '1.04';
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| 4 |
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| 5 | =head1 NAME
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| 6 |
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| 7 | carp - warn of errors (from perspective of caller)
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| 8 |
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| 9 | cluck - warn of errors with stack backtrace
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| 10 | (not exported by default)
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| 11 |
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| 12 | croak - die of errors (from perspective of caller)
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| 13 |
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| 14 | confess - die of errors with stack backtrace
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| 15 |
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| 16 | shortmess - return the message that carp and croak produce
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| 17 |
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| 18 | longmess - return the message that cluck and confess produce
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| 19 |
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| 20 | =head1 SYNOPSIS
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| 21 |
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| 22 | use Carp;
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| 23 | croak "We're outta here!";
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| 24 |
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| 25 | use Carp qw(cluck);
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| 26 | cluck "This is how we got here!";
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| 27 |
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| 28 | print FH Carp::shortmess("This will have caller's details added");
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| 29 | print FH Carp::longmess("This will have stack backtrace added");
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| 30 |
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| 31 | =head1 DESCRIPTION
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| 32 |
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| 33 | The Carp routines are useful in your own modules because
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| 34 | they act like die() or warn(), but with a message which is more
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| 35 | likely to be useful to a user of your module. In the case of
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| 36 | cluck, confess, and longmess that context is a summary of every
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| 37 | call in the call-stack. For a shorter message you can use carp,
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| 38 | croak or shortmess which report the error as being from where
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| 39 | your module was called. There is no guarantee that that is where
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| 40 | the error was, but it is a good educated guess.
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| 41 |
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| 42 | You can also alter the way the output and logic of C<Carp> works, by
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| 43 | changing some global variables in the C<Carp> namespace. See the
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| 44 | section on C<GLOBAL VARIABLES> below.
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| 45 |
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| 46 | Here is a more complete description of how shortmess works. What
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| 47 | it does is search the call-stack for a function call stack where
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| 48 | it hasn't been told that there shouldn't be an error. If every
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| 49 | call is marked safe, it then gives up and gives a full stack
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| 50 | backtrace instead. In other words it presumes that the first likely
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| 51 | looking potential suspect is guilty. Its rules for telling whether
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| 52 | a call shouldn't generate errors work as follows:
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| 53 |
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| 54 | =over 4
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| 55 |
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| 56 | =item 1.
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| 57 |
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| 58 | Any call from a package to itself is safe.
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| 59 |
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| 60 | =item 2.
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| 61 |
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| 62 | Packages claim that there won't be errors on calls to or from
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| 63 | packages explicitly marked as safe by inclusion in @CARP_NOT, or
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| 64 | (if that array is empty) @ISA. The ability to override what
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| 65 | @ISA says is new in 5.8.
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| 66 |
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| 67 | =item 3.
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| 68 |
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| 69 | The trust in item 2 is transitive. If A trusts B, and B
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| 70 | trusts C, then A trusts C. So if you do not override @ISA
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| 71 | with @CARP_NOT, then this trust relationship is identical to,
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| 72 | "inherits from".
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| 73 |
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| 74 | =item 4.
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| 75 |
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| 76 | Any call from an internal Perl module is safe. (Nothing keeps
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| 77 | user modules from marking themselves as internal to Perl, but
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| 78 | this practice is discouraged.)
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| 79 |
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| 80 | =item 5.
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| 81 |
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| 82 | Any call to Carp is safe. (This rule is what keeps it from
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| 83 | reporting the error where you call carp/croak/shortmess.)
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| 84 |
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| 85 | =back
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| 86 |
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| 87 | =head2 Forcing a Stack Trace
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| 88 |
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| 89 | As a debugging aid, you can force Carp to treat a croak as a confess
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| 90 | and a carp as a cluck across I<all> modules. In other words, force a
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| 91 | detailed stack trace to be given. This can be very helpful when trying
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| 92 | to understand why, or from where, a warning or error is being generated.
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| 93 |
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| 94 | This feature is enabled by 'importing' the non-existent symbol
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| 95 | 'verbose'. You would typically enable it by saying
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| 96 |
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| 97 | perl -MCarp=verbose script.pl
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| 98 |
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| 99 | or by including the string C<MCarp=verbose> in the PERL5OPT
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| 100 | environment variable.
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| 101 |
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| 102 | Alternately, you can set the global variable C<$Carp::Verbose> to true.
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| 103 | See the C<GLOBAL VARIABLES> section below.
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| 104 |
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| 105 | =cut
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| 106 |
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| 107 | # This package is heavily used. Be small. Be fast. Be good.
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| 108 |
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| 109 | # Comments added by Andy Wardley <[email protected]> 09-Apr-98, based on an
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| 110 | # _almost_ complete understanding of the package. Corrections and
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| 111 | # comments are welcome.
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| 112 |
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| 113 | # The members of %Internal are packages that are internal to perl.
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| 114 | # Carp will not report errors from within these packages if it
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| 115 | # can. The members of %CarpInternal are internal to Perl's warning
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| 116 | # system. Carp will not report errors from within these packages
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| 117 | # either, and will not report calls *to* these packages for carp and
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| 118 | # croak. They replace $CarpLevel, which is deprecated. The
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| 119 | # $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
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| 120 | # text and function arguments should be formatted when printed.
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| 121 |
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| 122 | # Comments added by Jos I. Boumans <[email protected]> 11-Aug-2004
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| 123 | # I can not get %CarpInternal or %Internal to work as advertised,
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| 124 | # therefor leaving it out of the below documentation.
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| 125 | # $CarpLevel may be decprecated according to the last comment, but
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| 126 | # after 6 years, it's still around and in heavy use ;)
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| 127 |
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| 128 | =pod
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| 129 |
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| 130 | =head1 GLOBAL VARIABLES
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| 131 |
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| 132 | =head2 $Carp::CarpLevel
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| 133 |
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| 134 | This variable determines how many call frames are to be skipped when
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| 135 | reporting where an error occurred on a call to one of C<Carp>'s
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| 136 | functions. For example:
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| 137 |
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| 138 | $Carp::CarpLevel = 1;
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| 139 | sub bar { .... or _error('Wrong input') }
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| 140 | sub _error { Carp::carp(@_) }
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| 141 |
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| 142 | This would make Carp report the error as coming from C<bar>'s caller,
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| 143 | rather than from C<_error>'s caller, as it normally would.
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| 144 |
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| 145 | Defaults to C<0>.
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| 146 |
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| 147 | =head2 $Carp::MaxEvalLen
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| 148 |
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| 149 | This variable determines how many characters of a string-eval are to
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| 150 | be shown in the output. Use a value of C<0> to show all text.
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| 151 |
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| 152 | Defaults to C<0>.
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| 153 |
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| 154 | =head2 $Carp::MaxArgLen
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| 155 |
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| 156 | This variable determines how many characters of each argument to a
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| 157 | function to print. Use a value of C<0> to show the full length of the
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| 158 | argument.
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| 159 |
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| 160 | Defaults to C<64>.
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| 161 |
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| 162 | =head2 $Carp::MaxArgNums
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| 163 |
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| 164 | This variable determines how many arguments to each function to show.
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| 165 | Use a value of C<0> to show all arguments to a function call.
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| 166 |
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| 167 | Defaults to C<8>.
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| 168 |
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| 169 | =head2 $Carp::Verbose
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| 170 |
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| 171 | This variable makes C<Carp> use the C<longmess> function at all times.
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| 172 | This effectively means that all calls to C<carp> become C<cluck> and
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| 173 | all calls to C<croak> become C<confess>.
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| 174 |
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| 175 | Note, this is analogous to using C<use Carp 'verbose'>.
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| 176 |
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| 177 | Defaults to C<0>.
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| 178 |
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| 179 | =cut
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| 180 |
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| 181 |
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| 182 | $CarpInternal{Carp}++;
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| 183 | $CarpInternal{warnings}++;
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| 184 | $CarpLevel = 0; # How many extra package levels to skip on carp.
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| 185 | # How many calls to skip on confess.
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| 186 | # Reconciling these notions is hard, use
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| 187 | # %Internal and %CarpInternal instead.
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| 188 | $MaxEvalLen = 0; # How much eval '...text...' to show. 0 = all.
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| 189 | $MaxArgLen = 64; # How much of each argument to print. 0 = all.
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| 190 | $MaxArgNums = 8; # How many arguments to print. 0 = all.
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| 191 | $Verbose = 0; # If true then make shortmess call longmess instead
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| 192 |
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| 193 | require Exporter;
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| 194 | @ISA = ('Exporter');
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| 195 | @EXPORT = qw(confess croak carp);
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| 196 | @EXPORT_OK = qw(cluck verbose longmess shortmess);
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| 197 | @EXPORT_FAIL = qw(verbose); # hook to enable verbose mode
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| 198 |
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| 199 | =head1 BUGS
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| 200 |
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| 201 | The Carp routines don't handle exception objects currently.
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| 202 | If called with a first argument that is a reference, they simply
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| 203 | call die() or warn(), as appropriate.
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| 204 |
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| 205 | =cut
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| 206 |
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| 207 | # if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
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| 208 | # then the following method will be called by the Exporter which knows
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| 209 | # to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word
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| 210 | # 'verbose'.
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| 211 |
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| 212 | sub export_fail {
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| 213 | shift;
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| 214 | $Verbose = shift if $_[0] eq 'verbose';
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| 215 | return @_;
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| 216 | }
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| 217 |
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| 218 |
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| 219 | # longmess() crawls all the way up the stack reporting on all the function
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| 220 | # calls made. The error string, $error, is originally constructed from the
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| 221 | # arguments passed into longmess() via confess(), cluck() or shortmess().
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| 222 | # This gets appended with the stack trace messages which are generated for
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| 223 | # each function call on the stack.
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| 224 |
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| 225 | sub longmess {
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| 226 | {
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| 227 | local($@, $!);
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| 228 | # XXX fix require to not clear $@ or $!?
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| 229 | # don't use require unless we need to (for Safe compartments)
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| 230 | require Carp::Heavy unless $INC{"Carp/Heavy.pm"};
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| 231 | }
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| 232 | # Icky backwards compatibility wrapper. :-(
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| 233 | my $call_pack = caller();
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| 234 | if ($Internal{$call_pack} or $CarpInternal{$call_pack}) {
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| 235 | return longmess_heavy(@_);
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| 236 | }
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| 237 | else {
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| 238 | local $CarpLevel = $CarpLevel + 1;
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| 239 | return longmess_heavy(@_);
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| 240 | }
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| 241 | }
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| 242 |
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| 243 |
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| 244 | # shortmess() is called by carp() and croak() to skip all the way up to
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| 245 | # the top-level caller's package and report the error from there. confess()
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| 246 | # and cluck() generate a full stack trace so they call longmess() to
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| 247 | # generate that. In verbose mode shortmess() calls longmess() so
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| 248 | # you always get a stack trace
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| 249 |
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| 250 | sub shortmess { # Short-circuit &longmess if called via multiple packages
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| 251 | {
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| 252 | local($@, $!);
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| 253 | # XXX fix require to not clear $@ or $!?
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| 254 | # don't use require unless we need to (for Safe compartments)
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| 255 | require Carp::Heavy unless $INC{"Carp/Heavy.pm"};
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| 256 | }
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| 257 | # Icky backwards compatibility wrapper. :-(
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| 258 | my $call_pack = caller();
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| 259 | local @CARP_NOT = caller();
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| 260 | shortmess_heavy(@_);
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| 261 | }
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| 262 |
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| 263 |
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| 264 | # the following four functions call longmess() or shortmess() depending on
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| 265 | # whether they should generate a full stack trace (confess() and cluck())
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| 266 | # or simply report the caller's package (croak() and carp()), respectively.
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| 267 | # confess() and croak() die, carp() and cluck() warn.
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| 268 |
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| 269 | sub croak { die shortmess @_ }
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| 270 | sub confess { die longmess @_ }
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| 271 | sub carp { warn shortmess @_ }
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| 272 | sub cluck { warn longmess @_ }
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| 273 |
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| 274 | 1;
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