package Carp;
-# This package implements handy routines for modules that wish to throw
-# exceptions outside of the current package.
+=head1 NAME
+
+carp - warn of errors (from perspective of caller)
+
+cluck - warn of errors with stack backtrace
+ (not exported by default)
+
+croak - die of errors (from perspective of caller)
+
+confess - die of errors with stack backtrace
+
+=head1 SYNOPSIS
+
+ use Carp;
+ croak "We're outta here!";
+
+ use Carp qw(cluck);
+ cluck "This is how we got here!";
+
+=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.
+
+=head2 Forcing a Stack Trace
+
+As a debugging aid, you can force Carp to treat a croak as a confess
+and a carp as a cluck across I<all> modules. In other words, force a
+detailed stack trace to be given. This can be very helpful when trying
+to understand why, or from where, a warning or error is being generated.
+
+This feature is enabled by 'importing' the non-existent symbol
+'verbose'. You would typically enable it by saying
+
+ perl -MCarp=verbose script.pl
+
+or by including the string C<MCarp=verbose> in the L<PERL5OPT>
+environment variable.
+
+=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.
+
+=cut
+
+# This package is heavily used. Be small. Be fast. Be good.
+
+# 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.
+
+# The $CarpLevel variable can be set to "strip off" extra caller levels for
+# those times when Carp calls are buried inside other functions. The
+# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
+# text and function arguments should be formatted when printed.
+
+$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
require Exporter;
-@ISA = Exporter;
+@ISA = ('Exporter');
@EXPORT = qw(confess croak carp);
+@EXPORT_OK = qw(cluck verbose);
+@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';
+ return @_;
+}
+
+
+# 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.
sub longmess {
- my $error = shift;
- my $mess = "";
- my $i = 2;
- my ($pack,$file,$line,$sub);
- while (($pack,$file,$line,$sub) = caller($i++)) {
- $mess .= "\t$sub " if $error eq "called";
- $mess .= "$error at $file line $line\n";
- $error = "called";
- }
- $mess || $error;
+ { local $@; require Carp::Heavy; } # XXX fix require to not clear $@?
+ goto &longmess_heavy;
}
-sub shortmess {
- my $error = shift;
- my ($curpack) = caller(1);
- my $i = 2;
- my ($pack,$file,$line,$sub);
- while (($pack,$file,$line,$sub) = caller($i++)) {
- return "$error at $file line $line\n" if $pack ne $curpack;
- }
- longmess $error;
+
+# 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
+
+sub shortmess { # Short-circuit &longmess if called via multiple packages
+ { local $@; require Carp::Heavy; } # XXX fix require to not clear $@?
+ goto &shortmess_heavy;
}
-sub confess { die longmess @_; }
-sub croak { die shortmess @_; }
-sub carp { warn shortmess @_; }
+# 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.
+
+sub croak { die shortmess @_ }
+sub confess { die longmess @_ }
+sub carp { warn shortmess @_ }
+sub cluck { warn longmess @_ }
+
+1;
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