#!/usr/bin/perl

use strict;
use Inline 'C';
use Data::Dumper;

my $hash = { parent => { parent => {} } };

root($hash);

print "", Dumper({initial=>$hash, result=>root($hash)}), "\n";

__END__
__C__
SV* root(SV* sv) {
    if( SvOK(sv) && SvTYPE(sv) == SVt_RV ) {
        HV* h = SvRV(sv);
        SV* r;
        int i = 0;
        while( hv_exists(h, "parent", 6) ) {
            r = *( hv_fetch(h, "parent", 6, 0) );
            if( SvOK(r) && SvTYPE(r) == SVt_RV ) {
                h = SvRV(r);
                i = 1;
            }
        }

        if( i ) {
            SvREFCNT_inc(r);
            return r;
        }

    } else {
        croak("please pass hash refs to root");
    }

    return &PL_sv_undef;
}