use Data::Dumper;

sub do_nm
{
 my $obj = shift;
 open(NM,"nm -p $obj|") || die "Cannot open nm $obj:$!";
 $file{$obj} = {};
 while (<NM>)
  {
   if (/\b([A-Z])\b\s*_?(.*)$/)
    {
     my ($kind,$name) = ($1,$2);
     $file{$obj}{$name} = $kind;
     if ($kind ne 'U')
      {
       if (exists($def{$name}) && ($def{$name}[0] ne $kind || $def{$name}[1] ne $obj))
        {
         warn "$name " . Dumper($def{$name}) . " and [$kind,$obj]\n";
        }
       $def{$name} = [$kind,$obj];
      }
     else
      {
       $ref{$name} = [] unless (exists $ref{$name});
       push(@{$ref{$name}},$obj);
      }
    }
  }
 close(NM);
}

sub do_need
{
 my ($obj,$depth,$why)  = @_;
 die "No object" unless (defined $obj);
 my $hash = $file{$obj};
 die "No hash for $obj" unless (defined $hash);
 if (exists $need{$obj})
  {
   push(@{$need{$obj}},[$name,$why]);
   $depth{$obj} = $depth if ($depth < $depth{$obj});
  }
 else
  {
   $depth{$obj} = $depth;
   $need{$obj} = [];
   push(@{$need{$obj}},[$name,$why]);
   foreach $name (sort keys %$hash)
    {
     my $kind = $hash->{$name};
     if ($kind eq 'U')
      {
       if (exists $def{$name})
        {
         my ($kind,$file) = @{$def{$name}};
         do_need($file,$depth+1,$obj);
        }
       else
        {
         $unres{$name} = [] unless  (exists $unres{$name});
         push(@{$unres{$name}},$obj);
        }
      }
    }
  }
}

1;