Question

Does only declaring a variable reserves a space for it in the program memory? And if not, then please consider the following snippet:

void foo(int bar, int baz){
int a;
char b[4];
}

This code as soon as it enters foo allocates a space in stack and creates an activation record like this:

---

| baz |

---

| bar |

---

| saved PC |

---

| a |

---

| b |

So, how does this activation record allocates space for a and b even if they are only declared and not defined?

Answer 1

a and b are defined but not used. Since the program can’t tell whether they were created, the compiler is free to ignore them.