| 1 | package Carp; |
| 2 | |
| 3 | =head1 NAME |
| 4 | |
| 5 | carp - warn of errors (from perspective of caller) |
| 6 | |
| 7 | cluck - warn of errors with stack backtrace |
| 8 | (not exported by default) |
| 9 | |
| 10 | croak - die of errors (from perspective of caller) |
| 11 | |
| 12 | confess - die of errors with stack backtrace |
| 13 | |
| 14 | =head1 SYNOPSIS |
| 15 | |
| 16 | use Carp; |
| 17 | croak "We're outta here!"; |
| 18 | |
| 19 | use Carp qw(cluck); |
| 20 | cluck "This is how we got here!"; |
| 21 | |
| 22 | =head1 DESCRIPTION |
| 23 | |
| 24 | The Carp routines are useful in your own modules because |
| 25 | they act like die() or warn(), but report where the error |
| 26 | was in the code they were called from. Thus if you have a |
| 27 | routine Foo() that has a carp() in it, then the carp() |
| 28 | will report the error as occurring where Foo() was called, |
| 29 | not where carp() was called. |
| 30 | |
| 31 | =head2 Forcing a Stack Trace |
| 32 | |
| 33 | As a debugging aid, you can force Carp to treat a croak as a confess |
| 34 | and a carp as a cluck across I<all> modules. In other words, force a |
| 35 | detailed stack trace to be given. This can be very helpful when trying |
| 36 | to understand why, or from where, a warning or error is being generated. |
| 37 | |
| 38 | This feature is enabled by 'importing' the non-existent symbol |
| 39 | 'verbose'. You would typically enable it by saying |
| 40 | |
| 41 | perl -MCarp=verbose script.pl |
| 42 | |
| 43 | or by including the string C<MCarp=verbose> in the L<PERL5OPT> |
| 44 | environment variable. |
| 45 | |
| 46 | =head1 BUGS |
| 47 | |
| 48 | The Carp routines don't handle exception objects currently. |
| 49 | If called with a first argument that is a reference, they simply |
| 50 | call die() or warn(), as appropriate. |
| 51 | |
| 52 | =cut |
| 53 | |
| 54 | # This package is heavily used. Be small. Be fast. Be good. |
| 55 | |
| 56 | # Comments added by Andy Wardley <abw@kfs.org> 09-Apr-98, based on an |
| 57 | # _almost_ complete understanding of the package. Corrections and |
| 58 | # comments are welcome. |
| 59 | |
| 60 | # The $CarpLevel variable can be set to "strip off" extra caller levels for |
| 61 | # those times when Carp calls are buried inside other functions. The |
| 62 | # $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval |
| 63 | # text and function arguments should be formatted when printed. |
| 64 | |
| 65 | $CarpLevel = 0; # How many extra package levels to skip on carp. |
| 66 | $MaxEvalLen = 0; # How much eval '...text...' to show. 0 = all. |
| 67 | $MaxArgLen = 64; # How much of each argument to print. 0 = all. |
| 68 | $MaxArgNums = 8; # How many arguments to print. 0 = all. |
| 69 | $Verbose = 0; # If true then make shortmess call longmess instead |
| 70 | |
| 71 | require Exporter; |
| 72 | @ISA = ('Exporter'); |
| 73 | @EXPORT = qw(confess croak carp); |
| 74 | @EXPORT_OK = qw(cluck verbose); |
| 75 | @EXPORT_FAIL = qw(verbose); # hook to enable verbose mode |
| 76 | |
| 77 | |
| 78 | # if the caller specifies verbose usage ("perl -MCarp=verbose script.pl") |
| 79 | # then the following method will be called by the Exporter which knows |
| 80 | # to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word |
| 81 | # 'verbose'. |
| 82 | |
| 83 | sub export_fail { |
| 84 | shift; |
| 85 | $Verbose = shift if $_[0] eq 'verbose'; |
| 86 | return @_; |
| 87 | } |
| 88 | |
| 89 | |
| 90 | # longmess() crawls all the way up the stack reporting on all the function |
| 91 | # calls made. The error string, $error, is originally constructed from the |
| 92 | # arguments passed into longmess() via confess(), cluck() or shortmess(). |
| 93 | # This gets appended with the stack trace messages which are generated for |
| 94 | # each function call on the stack. |
| 95 | |
| 96 | sub longmess { |
| 97 | require Carp::Heavy; |
| 98 | goto &longmess_heavy; |
| 99 | } |
| 100 | |
| 101 | |
| 102 | # shortmess() is called by carp() and croak() to skip all the way up to |
| 103 | # the top-level caller's package and report the error from there. confess() |
| 104 | # and cluck() generate a full stack trace so they call longmess() to |
| 105 | # generate that. In verbose mode shortmess() calls longmess() so |
| 106 | # you always get a stack trace |
| 107 | |
| 108 | sub shortmess { # Short-circuit &longmess if called via multiple packages |
| 109 | require Carp::Heavy; |
| 110 | goto &shortmess_heavy; |
| 111 | } |
| 112 | |
| 113 | |
| 114 | # the following four functions call longmess() or shortmess() depending on |
| 115 | # whether they should generate a full stack trace (confess() and cluck()) |
| 116 | # or simply report the caller's package (croak() and carp()), respectively. |
| 117 | # confess() and croak() die, carp() and cluck() warn. |
| 118 | |
| 119 | sub croak { die shortmess @_ } |
| 120 | sub confess { die longmess @_ } |
| 121 | sub carp { warn shortmess @_ } |
| 122 | sub cluck { warn longmess @_ } |
| 123 | |
| 124 | 1; |