1.20. ARRAYS
Optimizing Xcode 4.6.3 (LLVM) (Thumb-2 mode)
Let’s get back to our simple array example (1.20.1 on page 268),
again, now we can see how LLVM checks the correctness of the “canary”:
_main
var_64 = -0x64
var_60 = -0x60
var_5C = -0x5C
var_58 = -0x58
var_54 = -0x54
var_50 = -0x50
var_4C = -0x4C
var_48 = -0x48
var_44 = -0x44
var_40 = -0x40
var_3C = -0x3C
var_38 = -0x38
var_34 = -0x34
var_30 = -0x30
var_2C = -0x2C
var_28 = -0x28
var_24 = -0x24
var_20 = -0x20
var_1C = -0x1C
var_18 = -0x18
canary = -0x14
var_10 = -0x10
PUSH {R4-R7,LR}
ADD R7, SP, #0xC
STR.W R8, [SP,#0xC+var_10]!
SUB SP, SP, #0x54
MOVW R0, #aObjc_methtype ; "objc_methtype"
MOVS R2, #0
MOVT.W R0, #0
MOVS R5, #0
ADD R0, PC
LDR.W R8, [R0]
LDR.W R0, [R8]
STR R0, [SP,#0x64+canary]
MOVS R0, #2
STR R2, [SP,#0x64+var_64]
STR R0, [SP,#0x64+var_60]
MOVS R0, #4
STR R0, [SP,#0x64+var_5C]
MOVS R0, #6
STR R0, [SP,#0x64+var_58]
MOVS R0, #8
STR R0, [SP,#0x64+var_54]
MOVS R0, #0xA
STR R0, [SP,#0x64+var_50]
MOVS R0, #0xC
STR R0, [SP,#0x64+var_4C]
MOVS R0, #0xE
STR R0, [SP,#0x64+var_48]
MOVS R0, #0x10
STR R0, [SP,#0x64+var_44]
MOVS R0, #0x12
STR R0, [SP,#0x64+var_40]
MOVS R0, #0x14
STR R0, [SP,#0x64+var_3C]
MOVS R0, #0x16
STR R0, [SP,#0x64+var_38]
MOVS R0, #0x18
STR R0, [SP,#0x64+var_34]
MOVS R0, #0x1A
STR R0, [SP,#0x64+var_30]