http://www.perlmonks.org?node_id=819525

Random_Walk has asked for the wisdom of the Perl Monks concerning the following question:

Wise monks, and the rest ;)

I have a logging routine from a supplier that has the prototype ($$). The first parameter is the log level, the second the message to log. I am overriding this sub already to add a debug feature and all is good. Now I would like to change the prototype to ($@) and then convert the @ with a join before calling the original logger.

# Patch nimlog to echo to STDOUT in debug
{
    no warnings qw(redefine);

    sub nimLog ($@) {
        my $msg = join ', ', @_;
        Nimbus::API::nimLog( $_[0], $msg );
        say $msg if $main::debug and $main::setup->{loglevel} >= $_[1]
+;
    }
}

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of course now I get the error Prototype mismatch. Is there a way to do this or should I just behave and use a new name for my new logger?

Thanks,
R.

Pereant, qui ante nos nostra dixerunt!

Replies are listed 'Best First'.
Re: override prototype
by ikegami (Patriarch) on Jan 25, 2010 at 16:45 UTC

    First, why are you using a prototype at all?

    Second, why do you import nimLog if you're going to replace the imported symbol?

    Finally, the so-called errors is simply an expected warning that can be silenced by changing 

    no warnings qw(redefine);

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    to 
    no warnings qw( redefine prototype );

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      I use a prototype because nimLog uses one. I was using ($$) prototype months ago when I first redefined the sub so I got no prototype warning.

      I use nimLog because modules I use from the supplier use nimLog, when debugging I can get their logging in my logfile too (though not in my STDOUT debug stream).

      Thanks for the pragma to fix the warning. I was thinking it was an error because something else in my code was causing it to die prematurely, doh!

      I guess now I suppressed the warning anyway I can also remove the prototype completely.

      Thanks for your help,
      R.

      Pereant, qui ante nos nostra dixerunt!
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        I use a prototype because nimLog uses one.

        And I'm asking why it has one.

        I use nimLog because modules I use from the supplier use nimLog

        I'm asking about the module where you replace nimLog with your own function, not some other module that wasn't even mentioned. Compare 

        # What you do
use Nimbus::API qw( nimLog );

{
    no warnings ...;
    sub nimLog {
        ...
        Nimbus::API::nimLog( ... );
        ...
    }
}

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        vs 

        # Sanity restored
use Nimbus::API qw( );

sub nimLog {
    ...
    Nimbus::API::nimLog( ... );
    ...
}

        [download]

        My question stands.

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Re: override prototype
by cdarke (Prior) on Jan 25, 2010 at 16:59 UTC
    The prototype ($@) is very mis-leading. It means one parameter in scalar context followed by a list which could be empy. It does not mean a scalar followed by an array
    my @fred = qw (The quick brown fox);

sub mysub ($@) {
    print "@_\n";
}

mysub(@fred)

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    prints:4 but then I guess you knew that because otherwise you would not be using prototypes ;-)
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