class c2{
    public:
        function2(std::ifstream &f){
            here it breaks
        }
};

class c1{
    public:
        c2 thing
        function1(std::ifstream &f){
            thing.function2(f);
        }
};
void funct2(std::ifstream &f){
    c1 stuff;
    stuff.function1(f);
}
void funct1(){
    std::ifstream f("whatever");
    funct2(f);
}