error: multiple declarations `xalloc' and `std::exception'

컴파일 하면 아래와 같이 에러가 나네요..왜 그런지 모르겠습니다.

c++ -fexceptions -c eg.cc
eg.cc: In function `int main(int, char**)':
eg.cc:43: error: multiple declarations `xalloc' and `std::exception'

#include <new>
#include <iostream>
#include <fstream>
#include "regexpr.h"

using namespace std;

class xalloc {} _xa;

void new_error()
{
	throw _xa;
}

int main(int argc, char *argv[])
{
	if(argc != 2 && argc != 3) {
		cerr << "Usage: " << argv[0] << " pattern [file]" << endl;
		return 1;
	}
	ifstream in(0);
	if(argc == 3) {
		in.close();
		in.open(argv[2]);
		if(!in) {
			cerr << argv[0] << ": Can't open " << argv[2] << endl;
			return 1;
		}
	}
	set_new_handler(new_error);
	RegExpr re;
	try {
		re.compile(argv[1]);
		int n;
		char buffer[500];
		while(!in.eof()) {
			in.getline(buffer, 500);
			n = re.search(buffer);
			if(n >= 0)
				cerr << buffer << endl;
		}
	}
	catch(xalloc exception) {
		cerr << endl << "Not enough memory." << endl;
		re.clear_after_error();
		return 1;
	}
	catch(xsyntax syntax) {
		cerr << endl << "Syntax error near character position "
			  << syntax.getErrorPos() << endl;
		re.clear_after_error();
		return 1;
	}
	return 0;
}