It's a cheap solution, but I would probably write a wrapper. 

sub setresuid {
    # force @_ to have three elements
    $#_ = 2;

    # replace undefs in @_ with -1
    for ( @_ ) {
        $_ = -1 if ! defined $_;
    }

    # magic goto the real setresuid
    goto &real_setresuid;
}

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In reply to Re: Passing undef to XSUB by kyle
in thread Passing undef to XSUB by pileofrogs

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