extern variable and array declare issue c++ -

i have problem extern variable , array declaration it. how declare array global variable located not in declarable file.

file1.cpp

const int size = 10; 

---

mainfile.cpp

extern const int size;  void main() {   int mas[size]; } 

---

int mas[size]; 

this line has issue. please guess??

first of constants have internal linkage. these declarations

file1.cpp const int size = 10; 

and

mainfile.cpp extern const int size; 

refer different entities.

the constant declared in file1.cpp not visible outside corresponding compilation unit.

according c++ standard (3.5 program , linkage)

3 name having namespace scope (3.3.6) has internal linkage if name of

— non-volatile variable explicitly declared const or constexpr , neither explicitly declared extern nor declared have external linkage; or

in mainfile value of size not specified compiler issue error statement

int mas[size]; 

becuase size of array shall compile-time constant expression.

the simplest solution place constant definition

const int size = 10; 

in common headet file included in each translation unit there reference constant.