C++: default constructor, virtual destructor: running time & computational cost

What happens if I have a default constructor [ construct(); ] and a virtual destructor [ virtual ~construct(); ] in my header (header.h) file, but still call them in my main file (Cheader.cpp)? Does it have repercussions on the computational costs, the running time or performance of the code?

I would call them in Cheader.cpp with [ header::header(); ] and with [header::~header(); ]