CSC231 Exercises On Functions

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Exercise 1

What is the behavior of this loop?

mov eax, 0 mov ecx, 10 for: call func1 ... loop for func1: add eax, 1 ret	The loop goes 10 times and the function is called 10 times, adding 1 to eax every time. Eax ends with 10 in it.

Exercise 2

Same question:

mov eax, 0 mov ecx, 10 for: call func1 ... loop for func1: sub ecx, 1 ret	The function decrements ecx by 1 every time through the loop. The loop is going to go twice as fast.

Exercise 3

Draw the stack as the processor executes this program:

mov eax, 0 mov ebx, 0 mov ecx, 10 for: call func1 ... loop for func1: add eax, 1 call func2 ret func2: add ebx, 1 ret	Just go through the motion and draw the stack. The return address of the instruction after the call gets pushed in the stack every time the processor executes a call. It is popped out of the stack every time the processor executes a ret.

Exercise 4

Same question, but now observe that the programmer forgot the ret instruction at the end of the first function.

	mov	eax, 0
	mov	ebx, 0
	mov	ecx, 10
for:	call	func1
	...
	loop	for



func1:	add	eax, 1
	call	func2

func2:	add	ebx, 1
	ret