so - the warning wasn't regarding ordering of a vector<int> and int but rather my original assumption. the intialization list has to match the order of variables as they are declared in the *.hpp. 

consider
struct A {
    int i;
    int j;
    A() : j(0), i(j) { }
};

i is initialized to some unknown value. order may also matter 
A(int n) : j(n++), i(n++) { }