package Carp;
our $VERSION = '1.14';
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
# 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.
# disable these by default, so they can live w/o require Carp
$CarpInternal{Carp}++;
$CarpInternal{warnings}++;
$Internal{Exporter}++;
$Internal{'Exporter::Heavy'}++;
# 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'; @_ }
sub longmess {
# Icky backwards compatibility wrapper. :-(
#
# The story is that the original implementation hard-coded the
# number of call levels to go back, so calls to longmess were off
# by one. Other code began calling longmess and expecting this
# behaviour, so the replacement has to emulate that behaviour.
my $call_pack = defined (*CORE::GLOBAL::caller{CODE}) ? *CORE::GLOBAL::caller{CODE}->() : caller();
if ($Internal{$call_pack} or $CarpInternal{$call_pack}) {
return longmess_heavy(@_);
}
else {
local $CarpLevel = $CarpLevel + 1;
return longmess_heavy(@_);
}
};
sub shortmess {
# Icky backwards compatibility wrapper. :-(
local @CARP_NOT = defined (*CORE::GLOBAL::caller{CODE}) ? *CORE::GLOBAL::caller{CODE}->() : caller();
shortmess_heavy(@_);
};
sub croak { die shortmess @_ }
sub confess { die longmess @_ }
sub carp { warn shortmess @_ }
sub cluck { warn longmess @_ }
sub caller_info {
my $i = shift(@_) + 1;
package DB;
my %call_info;
@call_info{
qw(pack file line sub has_args wantarray evaltext is_require)
} = defined (*CORE::GLOBAL::caller::{CODE}) ? *CORE::GLOBAL::{caller}->($i) : caller($i);
unless (defined $call_info{pack}) {
return ();
}
my $sub_name = Carp::get_subname(\%call_info);
if ($call_info{has_args}) {
my @args = map {Carp::format_arg($_)} @DB::args;
if ($MaxArgNums and @args > $MaxArgNums) { # More than we want to show?
$#args = $MaxArgNums;
push @args, '...';
}
# Push the args onto the subroutine
$sub_name .= '(' . join (', ', @args) . ')';
}
$call_info{sub_name} = $sub_name;
return wantarray() ? %call_info : \%call_info;
}
# Transform an argument to a function into a string.
sub format_arg {
my $arg = shift;
if (ref($arg)) {
$arg = defined($overload::VERSION) ? overload::StrVal($arg) : "$arg";
}
if (defined($arg)) {
$arg =~ s/'/\\'/g;
$arg = str_len_trim($arg, $MaxArgLen);
# Quote it?
$arg = "'$arg'" unless $arg =~ /^-?[\d.]+\z/;
} else {
$arg = 'undef';
}
# The following handling of "control chars" is direct from
# the original code - it is broken on Unicode though.
# Suggestions?
utf8::is_utf8($arg)
or $arg =~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1))/eg;
return $arg;
}
# Takes an inheritance cache and a package and returns
# an anon hash of known inheritances and anon array of
# inheritances which consequences have not been figured
# for.
sub get_status {
my $cache = shift;
my $pkg = shift;
$cache->{$pkg} ||= [{$pkg => $pkg}, [trusts_directly($pkg)]];
return @{$cache->{$pkg}};
}
# Takes the info from caller() and figures out the name of
# the sub/require/eval
sub get_subname {
my $info = shift;
if (defined($info->{evaltext})) {
my $eval = $info->{evaltext};
if ($info->{is_require}) {
return "require $eval";
}
else {
$eval =~ s/([\\\'])/\\$1/g;
return "eval '" . str_len_trim($eval, $MaxEvalLen) . "'";
}
}
return ($info->{sub} eq '(eval)') ? 'eval {...}' : $info->{sub};
}
# Figures out what call (from the point of view of the caller)
# the long error backtrace should start at.
sub long_error_loc {
my $i;
my $lvl = $CarpLevel;
{
++$i;
my $pkg = defined (*CORE::GLOBAL::caller{CODE}) ? *CORE::GLOBAL::caller{CODE}->($i) : caller($i);
unless(defined($pkg)) {
# This *shouldn't* happen.
if (%Internal) {
local %Internal;
$i = long_error_loc();
last;
}
else {
# OK, now I am irritated.
return 2;
}
}
redo if $CarpInternal{$pkg};
redo unless 0 > --$lvl;
redo if $Internal{$pkg};
}
return $i - 1;
}
sub longmess_heavy {
return @_ if ref($_[0]); # don't break references as exceptions
my $i = long_error_loc();
return ret_backtrace($i, @_);
}
# Returns a full stack backtrace starting from where it is
# told.
sub ret_backtrace {
my ($i, @error) = @_;
my $mess;
my $err = join '', @error;
$i++;
my $tid_msg = '';
if (defined &threads::tid) {
my $tid = threads->tid;
$tid_msg = " thread $tid" if $tid;
}
my %i = caller_info($i);
$mess = "$err at $i{file} line $i{line}$tid_msg\n";
while (my %i = caller_info(++$i)) {
$mess .= "\t$i{sub_name} called at $i{file} line $i{line}$tid_msg\n";
}
return $mess;
}
sub ret_summary {
my ($i, @error) = @_;
my $err = join '', @error;
$i++;
my $tid_msg = '';
if (defined &threads::tid) {
my $tid = threads->tid;
$tid_msg = " thread $tid" if $tid;
}
my %i = caller_info($i);
return "$err at $i{file} line $i{line}$tid_msg\n";
}
sub short_error_loc {
# You have to create your (hash)ref out here, rather than defaulting it
# inside trusts *on a lexical*, as you want it to persist across calls.
# (You can default it on $_[2], but that gets messy)
my $cache = {};
my $i = 1;
my $lvl = $CarpLevel;
{
my $called = defined (*CORE::GLOBAL::caller{CODE}) ? *CORE::GLOBAL::caller{CODE}->($i) : caller($i);
$i++;
my $caller = defined (*CORE::GLOBAL::caller{CODE}) ? *CORE::GLOBAL::caller{CODE}->($i) : caller($i);
return 0 unless defined($caller); # What happened?
redo if $Internal{$caller};
redo if $CarpInternal{$caller};
redo if $CarpInternal{$called};
redo if trusts($called, $caller, $cache);
redo if trusts($caller, $called, $cache);
redo unless 0 > --$lvl;
}
return $i - 1;
}
sub shortmess_heavy {
return longmess_heavy(@_) if $Verbose;
return @_ if ref($_[0]); # don't break references as exceptions
my $i = short_error_loc();
if ($i) {
ret_summary($i, @_);
}
else {
longmess_heavy(@_);
}
}
# If a string is too long, trims it with ...
sub str_len_trim {
my $str = shift;
my $max = shift || 0;
if (2 < $max and $max < length($str)) {
substr($str, $max - 3) = '...';
}
return $str;
}
# Takes two packages and an optional cache. Says whether the
# first inherits from the second.
#
# Recursive versions of this have to work to avoid certain
# possible endless loops, and when following long chains of
# inheritance are less efficient.
sub trusts {
my $child = shift;
my $parent = shift;
my $cache = shift;
my ($known, $partial) = get_status($cache, $child);
# Figure out consequences until we have an answer
while (@$partial and not exists $known->{$parent}) {
my $anc = shift @$partial;
next if exists $known->{$anc};
$known->{$anc}++;
my ($anc_knows, $anc_partial) = get_status($cache, $anc);
my @found = keys %$anc_knows;
@$known{@found} = ();
push @$partial, @$anc_partial;
}
return exists $known->{$parent};
}
# Takes a package and gives a list of those trusted directly
sub trusts_directly {
my $class = shift;
no strict 'refs';
no warnings 'once';
return @{"$class\::CARP_NOT"}
? @{"$class\::CARP_NOT"}
: @{"$class\::ISA"};
}
1;
__END__
=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 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 C<carp>
or C<croak> 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 C<carp> and C<croak> work.
What they do is search the call-stack for a function call stack where
they have not been told that there shouldn't be an error. If every
call is marked safe, they give up and give a full stack backtrace
instead. In other words they presume that the first likely looking
potential suspect is guilty. Their 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 C<@CARP_NOT>, or
(if that array is empty) C<@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 C<@ISA>
with C<@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 Perl's warning system (eg Carp itself) is safe.
(This rule is what keeps it from reporting the error at the
point where you call C<carp> or C<croak>.)
=item 6.
C<$Carp::CarpLevel> can be set to skip a fixed number of additional
call levels. Using this is not recommended because it is very
difficult to get it to behave correctly.
=back
=head2 Forcing a Stack Trace
As a debugging aid, you can force Carp to treat a croak as a confess
and a carp as a cluck across I<all> modules. In other words, force a
detailed stack trace to be given. This can be very helpful when trying
to understand why, or from where, a warning or error is being generated.
This feature is enabled by 'importing' the non-existent symbol
'verbose'. You would typically enable it by saying
perl -MCarp=verbose script.pl
or by including the string C<-MCarp=verbose> in the PERL5OPT
environment variable.
Alternately, you can set the global variable C<$Carp::Verbose> to true.
See the C<GLOBAL VARIABLES> section below.
=head1 GLOBAL VARIABLES
=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 $Carp::Verbose
This variable makes C<carp> and C<cluck> generate stack backtraces
just like C<cluck> and C<confess>. This is how C<use Carp 'verbose'>
is implemented internally.
Defaults to C<0>.
=head2 @CARP_NOT
This variable, I<in your package>, says which packages are I<not> to be
considered as the location of an error. The C<carp()> and C<cluck()>
functions will skip over callers when reporting where an error occurred.
NB: This variable must be in the package's symbol table, thus:
# These work
our @CARP_NOT; # file scope
use vars qw(@CARP_NOT); # package scope
@My::Package::CARP_NOT = ... ; # explicit package variable
# These don't work
sub xyz { ... @CARP_NOT = ... } # w/o declarations above
my @CARP_NOT; # even at top-level
Example of use:
package My::Carping::Package;
use Carp;
our @CARP_NOT;
sub bar { .... or _error('Wrong input') }
sub _error {
# temporary control of where'ness, __PACKAGE__ is implicit
local @CARP_NOT = qw(My::Friendly::Caller);
carp(@_)
}
This would make C<Carp> report the error as coming from a caller not
in C<My::Carping::Package>, nor from C<My::Friendly::Caller>.
Also read the L</DESCRIPTION> section above, about how C<Carp> decides
where the error is reported from.
Use C<@CARP_NOT>, instead of C<$Carp::CarpLevel>.
Overrides C<Carp>'s use of C<@ISA>.
=head2 %Carp::Internal
This says what packages are internal to Perl. C<Carp> will never
report an error as being from a line in a package that is internal to
Perl. For example:
$Carp::Internal{ (__PACKAGE__) }++;
# time passes...
sub foo { ... or confess("whatever") };
would give a full stack backtrace starting from the first caller
outside of __PACKAGE__. (Unless that package was also internal to
Perl.)
=head2 %Carp::CarpInternal
This says which packages are internal to Perl's warning system. For
generating a full stack backtrace this is the same as being internal
to Perl, the stack backtrace will not start inside packages that are
listed in C<%Carp::CarpInternal>. But it is slightly different for
the summary message generated by C<carp> or C<croak>. There errors
will not be reported on any lines that are calling packages in
C<%Carp::CarpInternal>.
For example C<Carp> itself is listed in C<%Carp::CarpInternal>.
Therefore the full stack backtrace from C<confess> will not start
inside of C<Carp>, and the short message from calling C<croak> is
not placed on the line where C<croak> was called.
=head2 $Carp::CarpLevel
This variable determines how many additional call frames are to be
skipped that would not otherwise be when reporting where an error
occurred on a call to one of C<Carp>'s functions. It is fairly easy
to count these call frames on calls that generate a full stack
backtrace. However it is much harder to do this accounting for calls
that generate a short message. Usually people skip too many call
frames. If they are lucky they skip enough that C<Carp> goes all of
the way through the call stack, realizes that something is wrong, and
then generates a full stack backtrace. If they are unlucky then the
error is reported from somewhere misleading very high in the call
stack.
Therefore it is best to avoid C<$Carp::CarpLevel>. Instead use
C<@CARP_NOT>, C<%Carp::Internal> and C<%Carp::CarpInternal>.
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.