1.15. SWITCH()/CASE/DEFAULT
x86
Non-optimizing MSVC
We get (MSVC 2010):
Listing 1.152: MSVC 2010tv64 = -4 ; size = 4
_a$ = 8 ; size = 4
_f PROC
push ebp
mov ebp, esp
push ecx
mov eax, DWORD PTR _a$[ebp]
mov DWORD PTR tv64[ebp], eax
cmp DWORD PTR tv64[ebp], 4
ja SHORT $LN1@f
mov ecx, DWORD PTR tv64[ebp]
jmp DWORD PTR $LN11@f[ecx*4]
$LN6@f:
push OFFSET $SG739 ; 'zero', 0aH, 00H
call _printf
add esp, 4
jmp SHORT $LN9@f
$LN5@f:
push OFFSET $SG741 ; 'one', 0aH, 00H
call _printf
add esp, 4
jmp SHORT $LN9@f
$LN4@f:
push OFFSET $SG743 ; 'two', 0aH, 00H
call _printf
add esp, 4
jmp SHORT $LN9@f
$LN3@f:
push OFFSET $SG745 ; 'three', 0aH, 00H
call _printf
add esp, 4
jmp SHORT $LN9@f
$LN2@f:
push OFFSET $SG747 ; 'four', 0aH, 00H
call _printf
add esp, 4
jmp SHORT $LN9@f
$LN1@f:
push OFFSET $SG749 ; 'something unknown', 0aH, 00H
call _printf
add esp, 4
$LN9@f:
mov esp, ebp
pop ebp
ret 0
npad 2 ; align next label
$LN11@f:
DD $LN6@f ; 0
DD $LN5@f ; 1
DD $LN4@f ; 2
DD $LN3@f ; 3
DD $LN2@f ; 4
_f ENDP
What we see here is a set ofprintf()calls with various arguments. All they have not only addresses in
the memory of the process, but also internal symbolic labels assigned by the compiler. All these labels
are also mentioned in the$LN11@finternal table.
At the function start, ifais greater than 4, control flow is passed to label$LN1@f, whereprintf()with
argument'something unknown'is called.