Re: $Carp::Verbose ? (SOLVED)

It's not the first time I'm stumbling over the documentation for Carp and it's still confusing me every time...

Point is that carp and croak are meant for reporting module errors but from the perspective of a client who is using a module.

This is decided by checking the package of the subs in the call stack.

BUT if they all belong to the same package they will behave like confess and give the full stacktrace

Here is a more complete description of how carp and 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.

The following example shows what happens if the call happens from an OTHER package instead of the SAME.

-*- mode: compilation; default-directory: "d:/tmp/job/" -*-
Compilation started at Thu Sep 30 17:33:06

C:/Strawberry/perl/bin\perl.exe -w d:/tmp/job/test_carp.pl 
Perl-Version 5.032001 MSWin32S
====== default $Carp::Verbose =$VAR1 = 0;

====== Setting Verbose to 0
=== Testing die
Fehlermeldung at d:/tmp/job/test_carp.pl line 27.

=== Testing croak
Fehlermeldung at (eval 6) line 4.

=== Testing confess
Fehlermeldung at d:/tmp/job/test_carp.pl line 29.
    SAME::throw0("confess") called at d:/tmp/job/test_carp.pl line 34
    SAME::throw1("confess") called at d:/tmp/job/test_carp.pl line 38
    SAME::throw2("confess") called at (eval 7) line 4
    OTHER::client0("confess") called at (eval 7) line 7
    OTHER::client1("confess") called at (eval 7) line 9
    eval '            package OTHER;
            use Data::Dumper;
            sub client0 {
                SAME::throw2(@_);
            };
            sub client1 {
                client0(@_);
            };
            client1("confess");
' called at d:/tmp/job/test_carp.pl line 53

====== Setting Verbose to 1
=== Testing die
Fehlermeldung at d:/tmp/job/test_carp.pl line 27.

=== Testing croak
Fehlermeldung at d:/tmp/job/test_carp.pl line 25.
    SAME::throw0("croak") called at d:/tmp/job/test_carp.pl line 34
    SAME::throw1("croak") called at d:/tmp/job/test_carp.pl line 38
    SAME::throw2("croak") called at (eval 9) line 4
    OTHER::client0("croak") called at (eval 9) line 7
    OTHER::client1("croak") called at (eval 9) line 9
    eval '            package OTHER;
            use Data::Dumper;
            sub client0 {
                SAME::throw2(@_);
            };
            sub client1 {
                client0(@_);
            };
            client1("croak");
' called at d:/tmp/job/test_carp.pl line 53

=== Testing confess
Fehlermeldung at d:/tmp/job/test_carp.pl line 29.
    SAME::throw0("confess") called at d:/tmp/job/test_carp.pl line 34
    SAME::throw1("confess") called at d:/tmp/job/test_carp.pl line 38
    SAME::throw2("confess") called at (eval 10) line 4
    OTHER::client0("confess") called at (eval 10) line 7
    OTHER::client1("confess") called at (eval 10) line 9
    eval '            package OTHER;
            use Data::Dumper;
            sub client0 {
                SAME::throw2(@_);
            };
            sub client1 {
                client0(@_);
            };
            client1("confess");
' called at d:/tmp/job/test_carp.pl line 53


Compilation finished at Thu Sep 30 17:33:06
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here the code

Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

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Re^2: $Carp::Verbose ? (SOLVED) by LanX (Saint) on Sep 30, 2021 at 17:14 UTC
here a shorter test, avoiding string evals and concentrating on croak. (line 72 is inside sub client0) You can uncomment other cases if needed. -- mode: compilation; default-directory: "d:/tmp/job/" -- Compilation started at Thu Sep 30 19:14:48 C:/Strawberry/perl/bin\perl.exe -w d:/tmp/job/test_carp.pl xxxxxxxxx Perl-Version 5.032001 MSWin32S ******* Setting Verbose to 0 ====== Testing <croak> ... from SAME package error-messageby <croak> from SAME package at d:/tmp/job/test_carp.pl l +ine 54. SAME::throw0("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 63 SAME::throw1("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 67 SAME::throw2("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 82 SAME::client0("SAME", "croak") called at d:/tmp/job/test_carp.pl l +ine 85 SAME::client1("SAME", "croak") called at d:/tmp/job/test_carp.pl l +ine 42 eval {...} called at d:/tmp/job/test_carp.pl line 42 ... from OTHER package error-messageby <croak> from OTHER package at d:/tmp/job/test_carp.pl +line 74. ... from THIRD package error-messageby <croak> from THIRD package at d:/tmp/job/test_carp.pl +line 74. ******* Setting Verbose to 1 ====== Testing <croak> ... from SAME package error-messageby <croak> from SAME package at d:/tmp/job/test_carp.pl l +ine 54. SAME::throw0("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 63 SAME::throw1("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 67 SAME::throw2("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 82 SAME::client0("SAME", "croak") called at d:/tmp/job/test_carp.pl l +ine 85 SAME::client1("SAME", "croak") called at d:/tmp/job/test_carp.pl l +ine 42 eval {...} called at d:/tmp/job/test_carp.pl line 42 ... from OTHER package error-messageby <croak> from OTHER package at d:/tmp/job/test_carp.pl +line 54. SAME::throw0("OTHER", "croak") called at d:/tmp/job/test_carp.pl l +ine 63 SAME::throw1("OTHER", "croak") called at d:/tmp/job/test_carp.pl l +ine 67 SAME::throw2("OTHER", "croak") called at d:/tmp/job/test_carp.pl l +ine 74 OTHER::client0("OTHER", "croak") called at d:/tmp/job/test_carp.pl + line 77 OTHER::client1("OTHER", "croak") called at d:/tmp/job/test_carp.pl + line 42 eval {...} called at d:/tmp/job/test_carp.pl line 42 ... from THIRD package error-messageby <croak> from THIRD package at d:/tmp/job/test_carp.pl +line 54. SAME::throw0("THIRD", "croak") called at d:/tmp/job/test_carp.pl l +ine 63 SAME::throw1("THIRD", "croak") called at d:/tmp/job/test_carp.pl l +ine 67 SAME::throw2("THIRD", "croak") called at d:/tmp/job/test_carp.pl l +ine 74 OTHER::client0("THIRD", "croak") called at d:/tmp/job/test_carp.pl + line 90 THIRD::client0("THIRD", "croak") called at d:/tmp/job/test_carp.pl + line 93 THIRD::client1("THIRD", "croak") called at d:/tmp/job/test_carp.pl + line 42 eval {...} called at d:/tmp/job/test_carp.pl line 42 Compilation finished at Thu Sep 30 19:14:48 [download] use strict; use warnings; package SAME; use Carp; use Data::Dumper; sub out { $_[0] =~ m/^([-.=]+ )/; my $nl = "\n" x ( length($1//0)/3); warn $nl, @_,"\n" } out "xxxxxxxxx Perl-Version $] $^OS"; #out '========= default $Carp::Verbose = ',$Carp::Verbose; my $err_msg = "error-message"; for my $verbose ( 0, 1, ) { if (defined $verbose) { $Carp::Verbose = $verbose; out "******** Setting Verbose to $verbose"; } no warnings 'redefine'; # --- types of dieing for my $type ( # "die", "croak", # "confess", ) { out "====== Testing <$type>"; for my $PACKAGE (qw/SAME OTHER THIRD/) { out "... from $PACKAGE package"; eval { $PACKAGE->client1($type) } or out $@; } } } sub throw0 { my ($pkg,$type) = @_; my $err_msg = $err_msg . "by <$type> from $pkg package"; eval { goto $type } or die "Testcase '$type' not implemented"; croak: croak $err_msg; die: die $err_msg; confess: confess $err_msg; } sub throw1 { throw0(@_) } sub throw2 { throw1(@_) } package OTHER; sub client0 { SAME::throw2(@_); }; sub client1 { client0(@_); }; package SAME; sub client0 { SAME::throw2(@_); }; sub client1 { client0(@_); }; package THIRD; sub client0 { OTHER::client0(@_); }; sub client1 { client0(@_); }; [download] Cheers Rolf _{(addicted to the Perl Programming Language :) Wikisyntax for the Monastery}	[reply] [d/l] [select]

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Re^2: $Carp::Verbose ? (SOLVED)
by LanX (Saint) on Sep 30, 2021 at 17:14 UTC

(line 72 is inside sub client0)

You can uncomment other cases if needed.

-*- mode: compilation; default-directory: "d:/tmp/job/" -*- Compilation started at Thu Sep 30 19:14:48 C:/Strawberry/perl/bin\perl.exe -w d:/tmp/job/test_carp.pl xxxxxxxxx Perl-Version 5.032001 MSWin32S ********* Setting Verbose to 0 ====== Testing <croak> ... from SAME package error-messageby <croak> from SAME package at d:/tmp/job/test_carp.pl l +ine 54. SAME::throw0("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 63 SAME::throw1("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 67 SAME::throw2("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 82 SAME::client0("SAME", "croak") called at d:/tmp/job/test_carp.pl l +ine 85 SAME::client1("SAME", "croak") called at d:/tmp/job/test_carp.pl l +ine 42 eval {...} called at d:/tmp/job/test_carp.pl line 42 ... from OTHER package error-messageby <croak> from OTHER package at d:/tmp/job/test_carp.pl +line 74. ... from THIRD package error-messageby <croak> from THIRD package at d:/tmp/job/test_carp.pl +line 74. ********* Setting Verbose to 1 ====== Testing <croak> ... from SAME package error-messageby <croak> from SAME package at d:/tmp/job/test_carp.pl l +ine 54. SAME::throw0("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 63 SAME::throw1("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 67 SAME::throw2("SAME", "croak") called at d:/tmp/job/test_carp.pl li +ne 82 SAME::client0("SAME", "croak") called at d:/tmp/job/test_carp.pl l +ine 85 SAME::client1("SAME", "croak") called at d:/tmp/job/test_carp.pl l +ine 42 eval {...} called at d:/tmp/job/test_carp.pl line 42 ... from OTHER package error-messageby <croak> from OTHER package at d:/tmp/job/test_carp.pl +line 54. SAME::throw0("OTHER", "croak") called at d:/tmp/job/test_carp.pl l +ine 63 SAME::throw1("OTHER", "croak") called at d:/tmp/job/test_carp.pl l +ine 67 SAME::throw2("OTHER", "croak") called at d:/tmp/job/test_carp.pl l +ine 74 OTHER::client0("OTHER", "croak") called at d:/tmp/job/test_carp.pl + line 77 OTHER::client1("OTHER", "croak") called at d:/tmp/job/test_carp.pl + line 42 eval {...} called at d:/tmp/job/test_carp.pl line 42 ... from THIRD package error-messageby <croak> from THIRD package at d:/tmp/job/test_carp.pl +line 54. SAME::throw0("THIRD", "croak") called at d:/tmp/job/test_carp.pl l +ine 63 SAME::throw1("THIRD", "croak") called at d:/tmp/job/test_carp.pl l +ine 67 SAME::throw2("THIRD", "croak") called at d:/tmp/job/test_carp.pl l +ine 74 OTHER::client0("THIRD", "croak") called at d:/tmp/job/test_carp.pl + line 90 THIRD::client0("THIRD", "croak") called at d:/tmp/job/test_carp.pl + line 93 THIRD::client1("THIRD", "croak") called at d:/tmp/job/test_carp.pl + line 42 eval {...} called at d:/tmp/job/test_carp.pl line 42 Compilation finished at Thu Sep 30 19:14:48
[download]

use strict;
use warnings;

package SAME;

use Carp;

use Data::Dumper;

sub out {
    $_[0] =~ m/^([-.*=]+ )/;
    my $nl = "\n" x ( length($1//0)/3);
    warn $nl, @_,"\n"
}

out "xxxxxxxxx Perl-Version $] $^OS";

#out '========= default $Carp::Verbose = ',$Carp::Verbose;

my $err_msg = "error-message";


for my $verbose (
                 0,
                 1,
                ) {
    if (defined $verbose) {
        $Carp::Verbose = $verbose;
        out "********* Setting Verbose to $verbose";
    }

    no warnings 'redefine';
    # --- types of dieing
    for my $type (
                  # "die",
                  "croak",
                  # "confess",
                 ) {
        out "====== Testing <$type>";
        for my $PACKAGE (qw/SAME OTHER THIRD/) {
        out "... from $PACKAGE package";
            eval { $PACKAGE->client1($type) } or out $@;
        }
    }
}


sub throw0 {
    my ($pkg,$type) = @_;

    my $err_msg = $err_msg . "by <$type> from $pkg package";

    eval { goto $type } or die "Testcase '$type' not implemented";
  croak:
    croak $err_msg;
  die:
    die $err_msg;
  confess:
    confess $err_msg;
}

sub throw1 {
    throw0(@_)
}

sub throw2 {
    throw1(@_)
}



package OTHER;
sub client0 {
    SAME::throw2(@_);
};
sub client1 {
    client0(@_);
};

package SAME;
sub client0 {
    SAME::throw2(@_);
};
sub client1 {
    client0(@_);
};

package THIRD;
sub client0 {
    OTHER::client0(@_);
};
sub client1 {
    client0(@_);
};
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Cheers Rolf
_{(addicted to the Perl Programming Language :)

Wikisyntax for the Monastery}

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