#!/usr/bin/perl -w

use strict;
use Data::Dumper;

my $vars = {};
my $state = [];

while (<>) {
	if (/^#define\s*([A-Za-z0-9_]*)/) {
		$vars->{$1} = 1;
		next;
	}
	if (/^#ifdef\s*([A-Za-z0-9_]*)/) {
		push(@$state, $1);
		next;
	}
	if (/^#ifndef\s*([A-Za-z0-9_]*)/) {
		push(@$state, '!'.$1);
		next;
	}
	if (/^#else/) {
		my $last = pop(@$state);
		if ($last =~ /^!(.*)$/) { $last = $1; }
		else { $last = '!' . $last; }
		push(@$state, $last);
		next;
	}
	if (/^#endif/) {
		pop(@$state);
		next;
	}

	my $cond = 1;
	foreach my $c (@$state) {
		if ($c =~ /^!(.*)$/) {
			if (defined($vars->{$1})) {
				$cond = 0;
				last;
			}
		} elsif ($c =~ /^(.*)$/) {
			if (!defined($vars->{$1})) {
				$cond = 0;
				last;
			}
		}
	}
	if ($cond) {
		s,//.*$,,;
		print $_;
	}
}