Re: undefined error message for static variable during link phase

[Paul Pluzhnikov]

jk <joerg-at-ibk@web.de> writes:

> struggling with C++ I run into an error which I do not understand.
> see the attached files

Again you should have tried to make a reduced test case:

    struct Foo { static int x; };
    int main()  { Foo f; return f.x; }

> the static variable foo1 is being declared undefined during link phase.

That's correct: you provided a declaration, but no definition for it.
Fix:

    struct Foo { static int x; };
    int Foo::x = 0; // storage for 'Foo::x' is reserved here (and only here)
    int main()  { Foo f; return f.x; }

> I have an example from "goto Objekt Orientierung" by Herold/Klar/Klar
> (Addison Wesley) which exactly allows this kind of use of a "static"
> variable

Either the example in your book has a bug, or (more likely) you
missed the fact that you must define the static variable as well
as declare it.

Cheers,
-- 
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