crash without warning

gistfile1.cpp

#include <iostream>
#include <cstring>
#include <string>
using namespace std;

int main() {
	string xbn_filename;
	string line_str;
	string block_str;

	//this is the code block that reads the ???.xbn file
	xbn_filename = "input.xbn";
	ifstream xbn_file (xbn_filename.c_str());
	if (xbn_file.is_open()) {
		while (!xbn_file.eof()) {
			getline(xbn_file, line_str);
			//cout<<line_str<<endl;
			//block_str.append(line_str);
			//block_str.append("\n");
		}
		//cout<<block_str<<endl;
		xbn_file.close();
	}
        return 0;
}