package Carp;
-# This package implements handy routines for modules that wish to throw
-# exceptions outside of the current package.
+our $VERSION = '1.01';
+
+=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
+
+shortmess - return the message that carp and croak produce
+
+longmess - return the message that cluck and confess produce
+
+=head1 SYNOPSIS
+
+ use Carp;
+ croak "We're outta here!";
+
+ 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 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.
+
+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
+
+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 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 members of %Internal are packages that are internal to perl.
+# Carp will not report errors from within these packages if it
+# can. The members of %CarpInternal are internal to Perl's warning
+# system. Carp will not report errors from within these packages
+# either, and will not report calls *to* these packages for carp and
+# croak. They replace $CarpLevel, which is deprecated. The
+# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
+# text and function arguments should be formatted when printed.
+
+$CarpInternal{Carp}++;
+$CarpInternal{warnings}++;
+$CarpLevel = 0; # How many extra package levels to skip on carp.
+ # How many calls to skip on confess.
+ # Reconciling these notions is hard, use
+ # %Internal and %CarpInternal instead.
+$MaxEvalLen = 0; # How much eval '...text...' to show. 0 = all.
+$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 longmess shortmess);
+@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";
+ { local $@; require Carp::Heavy; } # XXX fix require to not clear $@?
+ # Icky backwards compatibility wrapper. :-(
+ my $call_pack = caller();
+ if ($Internal{$call_pack} or $CarpInternal{$call_pack}) {
+ return longmess_heavy(@_);
+ }
+ else {
+ local $CarpLevel = $CarpLevel + 1;
+ return longmess_heavy(@_);
}
- $mess || $error;
}
-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 $@?
+ # Icky backwards compatibility wrapper. :-(
+ my $call_pack = caller();
+ local @CARP_NOT = caller();
+ 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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