package Carp;
+our $VERSION = '1.04';
+
=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
-
-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.
+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 = qw(confess croak carp);
-@EXPORT_OK = qw(cluck verbose);
+@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 {
- return @_ if ref $_[0];
- my $error = join '', @_;
- my $mess = "";
- my $i = 1 + $CarpLevel;
- my ($pack,$file,$line,$sub,$hargs,$eval,$require);
- my (@a);
- #
- # crawl up the stack....
- #
- while (do { { package DB; @a = caller($i++) } } ) {
- # get copies of the variables returned from caller()
- ($pack,$file,$line,$sub,$hargs,undef,$eval,$require) = @a;
- #
- # if the $error error string is newline terminated then it
- # is copied into $mess. Otherwise, $mess gets set (at the end of
- # the 'else {' section below) to one of two things. The first time
- # through, it is set to the "$error at $file line $line" message.
- # $error is then set to 'called' which triggers subsequent loop
- # iterations to append $sub to $mess before appending the "$error
- # at $file line $line" which now actually reads "called at $file line
- # $line". Thus, the stack trace message is constructed:
- #
- # first time: $mess = $error at $file line $line
- # subsequent times: $mess .= $sub $error at $file line $line
- # ^^^^^^
- # "called"
- if ($error =~ m/\n$/) {
- $mess .= $error;
- } else {
- # Build a string, $sub, which names the sub-routine called.
- # This may also be "require ...", "eval '...' or "eval {...}"
- if (defined $eval) {
- if ($require) {
- $sub = "require $eval";
- } else {
- $eval =~ s/([\\\'])/\\$1/g;
- if ($MaxEvalLen && length($eval) > $MaxEvalLen) {
- substr($eval,$MaxEvalLen) = '...';
- }
- $sub = "eval '$eval'";
- }
- } elsif ($sub eq '(eval)') {
- $sub = 'eval {...}';
- }
- # if there are any arguments in the sub-routine call, format
- # them according to the format variables defined earlier in
- # this file and join them onto the $sub sub-routine string
- if ($hargs) {
- # we may trash some of the args so we take a copy
- @a = @DB::args; # must get local copy of args
- # don't print any more than $MaxArgNums
- if ($MaxArgNums and @a > $MaxArgNums) {
- # cap the length of $#a and set the last element to '...'
- $#a = $MaxArgNums;
- $a[$#a] = "...";
- }
- for (@a) {
- # set args to the string "undef" if undefined
- $_ = "undef", next unless defined $_;
- if (ref $_) {
- # dunno what this is for...
- $_ .= '';
- s/'/\\'/g;
- }
- else {
- s/'/\\'/g;
- # terminate the string early with '...' if too long
- substr($_,$MaxArgLen) = '...'
- if $MaxArgLen and $MaxArgLen < length;
- }
- # 'quote' arg unless it looks like a number
- $_ = "'$_'" unless /^-?[\d.]+$/;
- # print high-end chars as 'M-<char>' or '^<char>'
- s/([\200-\377])/sprintf("M-%c",ord($1)&0177)/eg;
- s/([\0-\37\177])/sprintf("^%c",ord($1)^64)/eg;
- }
- # append ('all', 'the', 'arguments') to the $sub string
- $sub .= '(' . join(', ', @a) . ')';
- }
- # here's where the error message, $mess, gets constructed
- $mess .= "\t$sub " if $error eq "called";
- $mess .= "$error at $file line $line";
- if (exists $main::{'Thread::'}) {
- my $tid = Thread->self->tid;
- $mess .= " thread $tid" if $tid;
- }
- $mess .= "\n";
- }
- # we don't need to print the actual error message again so we can
- # change this to "called" so that the string "$error at $file line
- # $line" makes sense as "called at $file line $line".
- $error = "called";
+ {
+ 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(@_);
}
- # this kludge circumvents die's incorrect handling of NUL
- my $msg = \($mess || $error);
- $$msg =~ tr/\0//d;
- $$msg;
}
# you always get a stack trace
sub shortmess { # Short-circuit &longmess if called via multiple packages
- goto &longmess if $Verbose;
- return @_ if ref $_[0];
- my $error = join '', @_;
- my ($prevpack) = caller(1);
- my $extra = $CarpLevel;
- my $i = 2;
- my ($pack,$file,$line);
- # when reporting an error, we want to report it from the context of the
- # calling package. So what is the calling package? Within a module,
- # there may be many calls between methods and perhaps between sub-classes
- # and super-classes, but the user isn't interested in what happens
- # inside the package. We start by building a hash array which keeps
- # track of all the packages to which the calling package belongs. We
- # do this by examining its @ISA variable. Any call from a base class
- # method (one of our caller's @ISA packages) can be ignored
- my %isa = ($prevpack,1);
-
- # merge all the caller's @ISA packages into %isa.
- @isa{@{"${prevpack}::ISA"}} = ()
- if(@{"${prevpack}::ISA"});
-
- # now we crawl up the calling stack and look at all the packages in
- # there. For each package, we look to see if it has an @ISA and then
- # we see if our caller features in that list. That would imply that
- # our caller is a derived class of that package and its calls can also
- # be ignored
- while (($pack,$file,$line) = caller($i++)) {
- if(@{$pack . "::ISA"}) {
- my @i = @{$pack . "::ISA"};
- my %i;
- @i{@i} = ();
- # merge any relevant packages into %isa
- @isa{@i,$pack} = ()
- if(exists $i{$prevpack} || exists $isa{$pack});
- }
-
- # and here's where we do the ignoring... if the package in
- # question is one of our caller's base or derived packages then
- # we can ignore it (skip it) and go onto the next (but note that
- # the continue { } block below gets called every time)
- next
- if(exists $isa{$pack});
-
- # Hey! We've found a package that isn't one of our caller's
- # clan....but wait, $extra refers to the number of 'extra' levels
- # we should skip up. If $extra > 0 then this is a false alarm.
- # We must merge the package into the %isa hash (so we can ignore it
- # if it pops up again), decrement $extra, and continue.
- if ($extra-- > 0) {
- %isa = ($pack,1);
- @isa{@{$pack . "::ISA"}} = ()
- if(@{$pack . "::ISA"});
- }
- else {
- # OK! We've got a candidate package. Time to construct the
- # relevant error message and return it. die() doesn't like
- # to be given NUL characters (which $msg may contain) so we
- # remove them first.
- my $msg;
- $msg = "$error at $file line $line";
- if (exists $main::{'Thread::'}) {
- my $tid = Thread->self->tid;
- $mess .= " thread $tid" if $tid;
- }
- $msg .= "\n";
- $msg =~ tr/\0//d;
- return $msg;
- }
- }
- continue {
- $prevpack = $pack;
+ {
+ 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"};
}
-
- # uh-oh! It looks like we crawled all the way up the stack and
- # never found a candidate package. Oh well, let's call longmess
- # to generate a full stack trace. We use the magical form of 'goto'
- # so that this shortmess() function doesn't appear on the stack
- # to further confuse longmess() about it's calling package.
- goto &longmess;
+ # Icky backwards compatibility wrapper. :-(
+ my $call_pack = caller();
+ local @CARP_NOT = caller();
+ shortmess_heavy(@_);
}
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