Non-constexpr function's use in constexpr constructor is valid

The following is valid in gcc 4.8:

class Value {
    private:
        static std::vector<float> compile_time_vector;
        const bool compile_time_bool;

        static bool f(void) {
            compile_time_vector.push_back(2.3);

            return true;
        }

    public:
        template <typename type_t>
        constexpr Value(const type_t& value): compile_time_bool(f()) {}
};

std::vector isn't designed to work at compile time, so exactly what kind of code is this generating? I've used the class to make sure it isn't optimized out.