Static variable in template undefined

Question

Why isn't this code working and giving an "undefined max" ?

#include <iostream>
using namespace std;

template<typename T>
struct Foo {
  static T const max;
};

template<> struct Foo<int> { // Specialization
    static int max; 
};

template<typename T> T const Foo<T>::max = 22;

template struct Foo<int>;

int main() {

    struct Foo<int> ma;
    cout << ma.max;

    return 0;
}

I defined the static variable and I instantiated the template (I believe the explicit instantiation is useless here).

What's wrong?

check out this http://stackoverflow.com/questions/2342550/static-member-initialization-for-specialized-template-class — Rakib, Jun 20 '14 at 09:19

score 1 · Accepted Answer · answered Jun 20 '14 at 08:58

1

template<typename T> T const Foo<T>::max = 22; is the definition of the general case, not for the specialization.

You have also to define int Foo<int>::max = 22; for the int specialization.

answered Jun 20 '14 at 08:58

Jarod42

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why can't the definition for the general case be used? – user129506 Jun 20 '14 at 09:06
1

@user129506 Because an explicit specialisation of a class template is a separate class totally unrelated to the primary template - it can have entirely different members, for example. – Angew is no longer proud of SO Jun 20 '14 at 09:47

Static variable in template undefined

1 Answers1