At what exact moment is a local variable allocated storage?

Question

Suppose we have the following:

void print()
{
     int a;  // declaration
     a = 9;
     cout << a << endl;
}

int main ()
{
     print();
}
         


        

Answer 1

At least as things are typically implemented, it's in between the two. When you call a function, the compiler will generate code for the function call that evaluates the parameters (if any) and puts them in registers or on the stack. Then, when execution reaches the entry for the function, space for local variables will be allocated on the stack, and locals that need initialization will be initialized. At that point, there might be some code to save registers that are used by the function, shuffle values around to get them into the desired registers and such. The code for the body of the function starts to execute after that.