Re: [log4perl-devel] Calling $logger->info() from DESTROY method of a Perl object

[Mike S. <log...@pe...>]

On Tue, 3 Jun 2003, Gordon Marler wrote:

> # tri-natured: function, class method, or object method
> sub _classobj {
>   my $objclass = shift || __PACKAGE__;
>   my $class = ref($objclass) || $objclass;
>   no strict "refs";  # to convert sym ref to real one
>   return \%$class;
> }
>
> for my $datum (keys %{ _classobj() } ) {
>   # turn off strict refs so that we can register a method
>   # in the symbol table
>   no strict "refs";
>   *$datum = sub {
>     use strict "refs";
>     my $self = shift->_classobj();
>     $self->{$datum} = shift if @_;
>     return $self->{$datum};
>   }
> }

Ok, the previously posted suggestions should fix the problem described here,
but just out of curiosity:

The reason for the warning message is very obscure. If you call the test
program test.pl, consisting of

   use BE;
   $be = new BE;
   undef $be;
   print "\nfinished\n";

you'll get

   (in cleanup) Can't call method "log" on an undefined value at (eval 14) line 37 during global destruction

with the BE.pm code previously posted by Gordon and attached at the end of
this email.

However, if you're using the debugger, and run it like

    perl -d test.pl
    DB<1> r

you'll just get

    finished
    Debugged program terminated.  Use q to quit or R to restart,

Seems like the perl core gets confused with the reference count somehow.
Would be interesting if we can isolate the problem to a couple of lines
of code so we could submit it to p5p for further investigation ...

-- Mike

Mike Schilli
log...@pe...
http://perlmeister.com
http://log4perl.sourceforge.net


############################################################
# Code for BE.pm
############################################################

package BE;

use Log::Log4perl qw(:easy);

%BE = (
  logger         => "",
  ConfigFile     => "/etc/lb_lutab",
  # List of all BE objects
  ALL            => [ ],
);

 #tri-natured: function, class method, or object method
sub _classobj {
  my $objclass = shift || __PACKAGE__;
  my $class = ref($objclass) || $objclass;
  no strict "refs";  # to convert sym ref to real one
  return \%$class;
}

for my $datum (keys %{ _classobj() } ) {
  # turn off strict refs so that we can register a method
  # in the symbol table
  no strict "refs";
 *$datum = sub {
    use strict "refs";
    my $self = shift->_classobj();
    $self->{$datum} = shift if @_;
   return $self->{$datum};
  }
}

# Constructor
sub new {
  my ($caller,%arg) = @_;
  my $caller_is_obj = ref($caller);
  my $class = $caller_is_obj || $caller;
  my ($logger);

  unless (BE->logger) {
    Log::Log4perl->easy_init($DEBUG);
    my $logger = Log::Log4perl->get_logger('BE');
    print "logger is $logger\n";
    BE->logger($logger);
  }

  $logger = Log::Log4perl->get_logger('BE');

  my $instance = {
    _name           => $arg{name}    ||  # Name of this BE
                       undef,
     #... Other members of the object ...
    _logger         => undef,
  };

  # Save a copy of BE->logger here so the reference to the logger can
  # for use inside DESTROY
  $instance->{_logger} = $logger;

  # Append this to the Class list of all BEs
  my ($all) = BE->ALL();
  push @{$all}, $instance;
  BE->ALL($all);
  bless $instance, $class;

}

sub DESTROY {
  my ($self) = @_;
  my ($logger) = Log::Log4perl->get_logger("BE");
  $logger->info("Entering DESTROY method for " . __PACKAGE__ . "\n");
}

1;