1.14 Conditional jumps
xor eax, eax
ret 0
_main ENDP
However, the compiler forgot to remove the “skip me!” string.
1.13.2 Exercise
Try to achieve the same result using your favorite compiler and debugger.
1.14 Conditional jumps
1.14.1 Simple example
#include <stdio.h>
void f_signed (int a, int b)
{
if (a>b)
printf ("a>b\n");
if (a==b)
printf ("a==b\n");
if (a<b)
printf ("a<b\n");
};
void f_unsigned (unsigned int a, unsigned int b)
{
if (a>b)
printf ("a>b\n");
if (a==b)
printf ("a==b\n");
if (a<b)
printf ("a<b\n");
};
int main()
{
f_signed(1, 2);
f_unsigned(1, 2);
return 0;
};
x86
x86 + MSVC
Here is how thef_signed()function looks like:
Listing 1.106: Non-optimizing MSVC 2010_a$ = 8
_b$ = 12
_f_signed PROC
push ebp
mov ebp, esp
mov eax, DWORD PTR _a$[ebp]
cmp eax, DWORD PTR _b$[ebp]
jle SHORT $LN3@f_signed
push OFFSET $SG737 ; 'a>b'
call _printf
add esp, 4