Question

I have seen an interview question from Bloomberg from here: http://www.careercup.com/question?id=383154

extern void print(int *a, int z);
void print(int *a, int z);

Question 1> Will it compile?

Question 2> If it compiles, what does it mean?

extern int i;
int i;

Question 3> Will it compile?

Question 4> If it compiles, what does it mean?

Answer 1

// a function declaration
extern void print(int *a, int z);
// still a function declaration
void print(int *a, int z);

Answer 1

Yes, it compiles successfully.

Answer 2

A global function without a body {} is automatically a function declaration. The keyword extern is optional. So both of them are just declarations. And multiple declarations are just fine.

// a variable declaration
extern int i;
// a variable definition without an initializer
int i;

Answer 3

Yes, it compiles successfully.

Answer 4

One is a declaration and the other is definition. Note that this definition doesn’t have an initializer though. For global variables, you need explicitly add keyword extern to distinguish a declaration with a definition. And it’s perfectly conform to One Definition Rule in C++.

Edit: I cannot open the link there. I assume the code you mentioned is in a global context.