package Carp;
+our $VERSION = '1.05';
+# this file is an utra-lightweight stub. The first time a function is
+# called, Carp::Heavy is loaded, and the real short/longmessmess_jmp
+# subs are installed
+
+our $MaxEvalLen = 0;
+our $Verbose = 0;
+our $CarpLevel = 0;
+our $MaxArgLen = 64; # How much of each argument to print. 0 = all.
+our $MaxArgNums = 8; # How many arguments to print. 0 = all.
+
+require Exporter;
+our @ISA = ('Exporter');
+our @EXPORT = qw(confess croak carp);
+our @EXPORT_OK = qw(cluck verbose longmess shortmess);
+our @EXPORT_FAIL = qw(verbose); # hook to enable verbose mode
+
+# if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
+# then the following method will be called by the Exporter which knows
+# to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word
+# 'verbose'.
+
+sub export_fail { shift; $Verbose = shift if $_[0] eq 'verbose'; @_ }
+
+# fixed hooks for stashes to point to
+sub longmess { goto &longmess_jmp }
+sub shortmess { goto &shortmess_jmp }
+# these two are replaced when Carp::Heavy is loaded
+sub longmess_jmp {{ local($@, $!); require Carp::Heavy} goto &longmess_jmp}
+sub shortmess_jmp {{ local($@, $!); require Carp::Heavy} goto &shortmess_jmp}
+
+sub croak { die shortmess @_ }
+sub confess { die longmess @_ }
+sub carp { warn shortmess @_ }
+sub cluck { warn longmess @_ }
+
+1;
+__END__
+
=head1 NAME
carp - warn of errors (from perspective of caller)
confess - die of errors with stack backtrace
+shortmess - return the message that carp and croak produce
+
+longmess - return the message that cluck and confess produce
+
=head1 SYNOPSIS
use Carp;
use Carp qw(cluck);
cluck "This is how we got here!";
+ print FH Carp::shortmess("This will have caller's details added");
+ print FH Carp::longmess("This will have stack backtrace added");
+
=head1 DESCRIPTION
The Carp routines are useful in your own modules because
-they act like die() or warn(), but report where the error
-was in the code they were called from. Thus if you have a
-routine Foo() that has a carp() in it, then the carp()
-will report the error as occurring where Foo() was called,
-not where carp() was called.
+they act like die() or warn(), but with a message which is more
+likely to be useful to a user of your module. In the case of
+cluck, confess, and longmess that context is a summary of every
+call in the call-stack. For a shorter message you can use carp,
+croak or shortmess which report the error as being from where
+your module was called. There is no guarantee that that is where
+the error was, but it is a good educated guess.
+
+You can also alter the way the output and logic of C<Carp> works, by
+changing some global variables in the C<Carp> namespace. See the
+section on C<GLOBAL VARIABLES> below.
+
+Here is a more complete description of how shortmess works. What
+it does is search the call-stack for a function call stack where
+it hasn't been told that there shouldn't be an error. If every
+call is marked safe, it then gives up and gives a full stack
+backtrace instead. In other words it presumes that the first likely
+looking potential suspect is guilty. Its rules for telling whether
+a call shouldn't generate errors work as follows:
+
+=over 4
+
+=item 1.
+
+Any call from a package to itself is safe.
+
+=item 2.
+
+Packages claim that there won't be errors on calls to or from
+packages explicitly marked as safe by inclusion in @CARP_NOT, or
+(if that array is empty) @ISA. The ability to override what
+@ISA says is new in 5.8.
+
+=item 3.
+
+The trust in item 2 is transitive. If A trusts B, and B
+trusts C, then A trusts C. So if you do not override @ISA
+with @CARP_NOT, then this trust relationship is identical to,
+"inherits from".
+
+=item 4.
+
+Any call from an internal Perl module is safe. (Nothing keeps
+user modules from marking themselves as internal to Perl, but
+this practice is discouraged.)
+
+=item 5.
+
+Any call to Carp is safe. (This rule is what keeps it from
+reporting the error where you call carp/croak/shortmess.)
+
+=back
=head2 Forcing a Stack Trace
perl -MCarp=verbose script.pl
-or by including the string C<MCarp=verbose> in the L<PERL5OPT>
+or by including the string C<MCarp=verbose> in the PERL5OPT
environment variable.
-=head1 BUGS
+Alternately, you can set the global variable C<$Carp::Verbose> to true.
+See the C<GLOBAL VARIABLES> section below.
-The Carp routines don't handle exception objects currently.
-If called with a first argument that is a reference, they simply
-call die() or warn(), as appropriate.
+=head1 GLOBAL VARIABLES
-=cut
+=head2 $Carp::CarpLevel
-# This package is heavily used. Be small. Be fast. Be good.
+This variable determines how many call frames are to be skipped when
+reporting where an error occurred on a call to one of C<Carp>'s
+functions. For example:
-# Comments added by Andy Wardley <abw@kfs.org> 09-Apr-98, based on an
-# _almost_ complete understanding of the package. Corrections and
-# comments are welcome.
+ $Carp::CarpLevel = 1;
+ sub bar { .... or _error('Wrong input') }
+ sub _error { Carp::carp(@_) }
-# The $CarpLevel variable can be set to "strip off" extra caller levels for
-# those times when Carp calls are buried inside other functions. The
-# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
-# text and function arguments should be formatted when printed.
+This would make Carp report the error as coming from C<bar>'s caller,
+rather than from C<_error>'s caller, as it normally would.
-$CarpLevel = 0; # How many extra package levels to skip on carp.
-$MaxEvalLen = 0; # How much eval '...text...' to show. 0 = all.
-$MaxArgLen = 64; # How much of each argument to print. 0 = all.
-$MaxArgNums = 8; # How many arguments to print. 0 = all.
-$Verbose = 0; # If true then make shortmess call longmess instead
+Defaults to C<0>.
-require Exporter;
-@ISA = ('Exporter');
-@EXPORT = qw(confess croak carp);
-@EXPORT_OK = qw(cluck verbose);
-@EXPORT_FAIL = qw(verbose); # hook to enable verbose mode
+=head2 $Carp::MaxEvalLen
+This variable determines how many characters of a string-eval are to
+be shown in the output. Use a value of C<0> to show all text.
-# if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
-# then the following method will be called by the Exporter which knows
-# to do this thanks to @EXPORT_FAIL, above. $_[1] will contain the word
-# 'verbose'.
+Defaults to C<0>.
-sub export_fail {
- shift;
- $Verbose = shift if $_[0] eq 'verbose';
- return @_;
-}
+=head2 $Carp::MaxArgLen
+This variable determines how many characters of each argument to a
+function to print. Use a value of C<0> to show the full length of the
+argument.
-# longmess() crawls all the way up the stack reporting on all the function
-# calls made. The error string, $error, is originally constructed from the
-# arguments passed into longmess() via confess(), cluck() or shortmess().
-# This gets appended with the stack trace messages which are generated for
-# each function call on the stack.
+Defaults to C<64>.
-sub longmess {
- require Carp::Heavy;
- goto &longmess_heavy;
-}
+=head2 $Carp::MaxArgNums
+This variable determines how many arguments to each function to show.
+Use a value of C<0> to show all arguments to a function call.
-# shortmess() is called by carp() and croak() to skip all the way up to
-# the top-level caller's package and report the error from there. confess()
-# and cluck() generate a full stack trace so they call longmess() to
-# generate that. In verbose mode shortmess() calls longmess() so
-# you always get a stack trace
+Defaults to C<8>.
-sub shortmess { # Short-circuit &longmess if called via multiple packages
- require Carp::Heavy;
- goto &shortmess_heavy;
-}
+=head2 $Carp::Verbose
+This variable makes C<Carp> use the C<longmess> function at all times.
+This effectively means that all calls to C<carp> become C<cluck> and
+all calls to C<croak> become C<confess>.
-# the following four functions call longmess() or shortmess() depending on
-# whether they should generate a full stack trace (confess() and cluck())
-# or simply report the caller's package (croak() and carp()), respectively.
-# confess() and croak() die, carp() and cluck() warn.
+Note, this is analogous to using C<use Carp 'verbose'>.
-sub croak { die shortmess @_ }
-sub confess { die longmess @_ }
-sub carp { warn shortmess @_ }
-sub cluck { warn longmess @_ }
+Defaults to C<0>.
+
+=head1 BUGS
+
+The Carp routines don't handle exception objects currently.
+If called with a first argument that is a reference, they simply
+call die() or warn(), as appropriate.
-1;
https://perl5.git.perl.org / perl5.git / blobdiff