CHAPTER 8. ACCESSING PASSED ARGUMENTS CHAPTER 8. ACCESSING PASSED ARGUMENTS

Chapter 8

Accessing passed arguments

Now we figured out that thecallerfunction is passing arguments to thecalleevia the stack. But how does thecalleeaccess

them?

Listing 8.1: simple example

#include <stdio.h>

int f (int a, int b, int c)

{

return a*b+c;

};

int main()

{

printf ("%d\n", f(1, 2, 3));

return 0;

};

8.1 x86

8.1.1 MSVC

Here is what we get after compilation (MSVC 2010 Express):

Listing 8.2: MSVC 2010 Express

_TEXT SEGMENT

_a$ = 8 ; size = 4

_b$ = 12 ; size = 4

_c$ = 16 ; size = 4

_f PROC

push ebp

mov ebp, esp

mov eax, DWORD PTR _a$[ebp]

imul eax, DWORD PTR _b$[ebp]

add eax, DWORD PTR _c$[ebp]

pop ebp

ret 0

_f ENDP

_main PROC

push ebp

mov ebp, esp

push 3 ; 3rd argument

push 2 ; 2nd argument

push 1 ; 1st argument

call _f

add esp, 12

push eax

push OFFSET $SG2463 ; '%d', 0aH, 00H