c++ function passes bad parameter

I have this function as constructor:

Graph::Graph(std::string filename)
{
    std::ifstream file(filename);
    file >> vertexNum_;
    edgeNum_ = 0;
    int edges;
    file >> edges;
    for(int i = 0; i < edges; edges++)
    {
        int s,e;
        file >> s;
        file >> e;
        if(!AddEdge(s,e)){
            std::cout << "Bad file!";
            break;
        }
    }
    file.close();
}

When I call from main Graph g("test.in"); it gives me Segfault because in the function parameter filename is empty string (shown in debugger). I'm using QtCreator.

Any ideas where the problem is?