C++ extern storage class life-span

Question

I am a C++ newbie and come from a Java background. I would like to confirm the following:

I am reading C++ by dissection by Ira Pohl and the book states that the life-span for a file/extern variable/function is the duration of the program (which makes sense because the variable is not declared in a class).

What I want to know; is that also the case for a variable declared in a class? If not, if a variable is declared in a class does that make the variable use the auto storage class?

Thanks.

Answer 1

A member variable in a class has a life-span corresponding to the life-span of the class's instances, unless declared static.

struct Foo {
    int x;
    static int y;
};

This Foo, and therefore its x, has program life-span:

static Foo foo;

This one is auto:

int main() { Foo foo; }

This one is dynamically allocated and lives until the Foo is delete'd:

int main() { Foo *foo = new Foo; }

In each case, the y has program life-span.