package Carp;
-our $VERSION = '1.00';
+our $VERSION = '1.04';
=head1 NAME
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
-
-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.
-
-However, rather than duplicating this effort in your own exception
-object, you can access the caller information that croak() would supply
-as shortmess(), and the full stack trace that confess() would generate
-as longmess() (Neither of these are exported by default.)
+Alternately, you can set the global variable C<$Carp::Verbose> to true.
+See the C<GLOBAL VARIABLES> section below.
=cut
# _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
+# 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
# $Max(EvalLen|(Arg(Len|Nums)) variables are used to specify how the eval
# text and function arguments should be formatted when printed.
-$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
+# Comments added by Jos I. Boumans <kane@dwim.org> 11-Aug-2004
+# I can not get %CarpInternal or %Internal to work as advertised,
+# therefor leaving it out of the below documentation.
+# $CarpLevel may be decprecated according to the last comment, but
+# after 6 years, it's still around and in heavy use ;)
+
+=pod
+
+=head1 GLOBAL VARIABLES
+
+=head2 $Carp::CarpLevel
+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:
+
+ $Carp::CarpLevel = 1;
+ sub bar { .... or _error('Wrong input') }
+ sub _error { Carp::carp(@_) }
+
+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.
+
+Defaults to C<0>.
+
+=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.
+
+Defaults to C<0>.
+
+=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.
+
+Defaults to C<64>.
+
+=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.
+
+Defaults to C<8>.
+
+=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>.
+
+Note, this is analogous to using C<use Carp 'verbose'>.
+
+Defaults to C<0>.
+
+=cut
+
+# disable these by default, so they can live w/o require Carp
$CarpInternal{Carp}++;
+$CarpInternal{warnings}++;
+$Internal{Exporter}++;
+$Internal{'Exporter::Heavy'}++;
+$CarpLevel = 0; # How many extra package levels to skip on carp.
+ # How many calls to skip on confess.
+ # Reconciling these notions is hard, use
+ # %Internal and %CarpInternal instead.
+$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');
@EXPORT_OK = qw(cluck verbose longmess shortmess);
@EXPORT_FAIL = qw(verbose); # hook to enable verbose mode
+=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
# if the caller specifies verbose usage ("perl -MCarp=verbose script.pl")
# then the following method will be called by the Exporter which knows
# each function call on the stack.
sub longmess {
- { local $@; require Carp::Heavy; } # XXX fix require to not clear $@?
- goto &longmess_heavy;
+ {
+ local $@;
+ # XXX fix require to not clear $@?
+ # don't use require unless we need to (for Safe compartments)
+ require Carp::Heavy unless $INC{"Carp/Heavy.pm"};
+ }
+ # 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(@_);
+ }
}
# 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;
+ {
+ local $@;
+ # XXX fix require to not clear $@?
+ # don't use require unless we need to (for Safe compartments)
+ require Carp::Heavy unless $INC{"Carp/Heavy.pm"};
+ }
+ # Icky backwards compatibility wrapper. :-(
+ my $call_pack = caller();
+ local @CARP_NOT = caller();
+ shortmess_heavy(@_);
}
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