Assembly Language for Beginners

1.15. SWITCH()/CASE/DEFAULT

After the jump we are at0x010B103A: the code printing “two” will now be executed:

Figure 1.53:OllyDbg: now we at thecase:label

Non-optimizing GCC

Let’s see what GCC 4.4.1 generates:

Listing 1.153: GCC 4.4.1
public f
f proc near ; CODE XREF: main+10

var_18 = dword ptr -18h
arg_0 = dword ptr 8

push ebp

mov ebp, esp

sub esp, 18h

cmp [ebp+arg_0], 4

ja short loc_8048444

mov eax, [ebp+arg_0]

shl eax, 2

mov eax, ds:off_804855C[eax]

jmp eax

loc_80483FE: ; DATA XREF: .rodata:off_804855C
mov [esp+18h+var_18], offset aZero ; "zero"
call _puts
jmp short locret_8048450

loc_804840C: ; DATA XREF: .rodata:08048560
mov [esp+18h+var_18], offset aOne ; "one"
call _puts
jmp short locret_8048450

loc_804841A: ; DATA XREF: .rodata:08048564
mov [esp+18h+var_18], offset aTwo ; "two"
call _puts
jmp short locret_8048450

loc_8048428: ; DATA XREF: .rodata:08048568