关于内部联系的困惑

Question

According to the definition of internal linkage that i have read everywhere states that internal linkage means object is visible at file scope or everywhere in same file.

int main()
{
    extern int i;
    i = 0; //linker error
}

static int i;

Would you have it any way to make i visible inside, if its declared after main() without defining before it?

Answer 1

This is not a linking problem, but a compilation problem. At the time your main is compiled, i is not yet declared. So you have to put i before your main function in order to compile it.

Answer 2

You're confusing several issues. First, "linkage" concerns symbols, not objects. And secondly, independently of linkage, a symbol must be declared before you can use it. Put the static int i before main, and there will be no problem.

Answer 3

Your solution doesn't work as extern says that the variable is globally visible, but static says that it is not.

Presumably the linker believes this to be two different variables, and gets confused.

You have to declare all objects before use, but you also have to be consistent.