Should re-include stuff thats already in the project scope precompiled header?

Question

I have a precompiled header stdafx.h which is used in all source files in my project. Thus all headers in the stdafx.h are available in all code files in the project.

What I'm unsure about is whether or not to re-include stuff thats already in the precompiled header. What do you guys think?

e.g.

stdafx.h

#pragma once

#include <memory>

my_class.h

#pragma once

#include <memory> // Re-include or not that's the question. Best practice?

struct my_class
{
};
typedef std::shared_ptr<my_class> my_class_ptr;

main.cpp

#include "stdafx.h"
#include "my_class.h"

int main()
{
}

Answer 1

I would include it so that the header could be reused in a project which has different stdafx.h Another way of stating this is each header should contain all the declarations (preferably forward ones) it needs on its own

There will not be any performance hit as the contents of the header will not be processed due to internal header guard (or for VS the #pragma:once in the header file.