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C ++ multiple definition static array class variable

I am writing some code where I need to have a class variable, a static int array. I understand that I can do this with something like this in the header file, Ah:

#ifndef A_H_
#define A_H_

class A
{
public:
  static const int a[];
};

const int A::a[] = {1,2};

#endif

This works fine if I include this header in only one other file, something like the following: main.cpp:

#include "A.h"

#include <iostream>
using namespace std;

int main()
{

  A myA;  
  cout << "0: " << myA.a[0] << endl;
  cout << "1: " << myA.a[1] << endl;
}

But suppose I need my class A to be a little more complicated, and I want to have an A.cpp file. I will save the main.cpp file the same way, but then change Ah as follows (I just added a function, printA):

#ifndef A_H_
#define A_H_

class A
{
public:
  void printA() const;
  static const int a[];
};

const int A::a[] = {1,2};

#endif

And then in the A.cpp file:

#include "A.h"

#include <iostream>
using namespace std;

void A::printA() const
{

  cout << "Printing in A.cpp." << endl;
  cout << "A.0: " << a[0] << endl;
  cout << "A.1: " << a[1] << endl;

}

Compiling Ao with gcc -o Ao -c A.cpp is fine. But linking this when compiling main.cpp (gcc -o atest main.cpp Ao) fails with the "multiple definition" A :: a ".

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+5
2

. :

//A.cpp
#include "A.h"
const int A::a[] = {1,2};

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+17

"const int A:: a [] = {1,2};" . .cpp. , .

+7

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