Extern const array

extern_const.cpp

#include <iostream>
#include "extern_const.hpp"

const int n = 10;
//const int a[] = {1, 2}; // this is also ok
extern const int a[] = {1, 2};

int main(int argc, char *argv[])
{
    increse();
    return 0;
}

extern_const.hpp

#include <iostream>
extern const int n;
extern const int a[1];//or just don't write any size
/* error: too many initializers for ‘const int [1]’
 extern const int a[] = {1, 2};*/
void increse();

extern_const2.cpp

#include <iostream>
#include "extern_const.hpp"

void increse(){
    // the n is initialized in extern_const.cpp
    std::cout << n++ << std::endl;//1.increase const -- error
}