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typedef



Joined: 25 Jul 2010
Posts: 2913
Location: 0x77760000
typedef
So when we write this code

Code:
local strHey[5]:BYTE
    


Does the system allocate 5 null bytes on the stack so that the following would be ok without explicitly mov-ing a 0 at the 4th index of the string "hey!" to terminate it?

Code:
mov dword[strHey], "hey!" ; 4 bytes
;------------------------------ I want to skip mov byte[strHey+4],0
invoke MessageBoxA,0,addr strHey,0,0
...
    


I want to skip the extra step of having to manually put a null byte but at the same time I'm not sure if there'll be garbage or not.
Post 29 Oct 2012, 14:02
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AsmGuru62



Joined: 28 Jan 2004
Posts: 1409
Location: Toronto, Canada
AsmGuru62
There will be whatever is left on stack from previous code.
Post 29 Oct 2012, 14:41
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typedef



Joined: 25 Jul 2010
Posts: 2913
Location: 0x77760000
typedef
That makes sense. Thanks. I checked in OllyDbg and in my case since the proc was the first to execute, there was a huge cave of null's on the stack after ntdll and kernel used it.

Thanks for the answer though.
Post 29 Oct 2012, 23:50
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AsmGuru62



Joined: 28 Jan 2004
Posts: 1409
Location: Toronto, Canada
AsmGuru62
My code generator will have an option for this:
Code:
locals @8 =0      ; Align EBP to 8 byte boundary and set all local bytes to zero
{
    HANDLE  hFile
       INT32   value = -1
  PWCHAR  path = stkalloc (WCHAR, MAX_PATH)
   PVOID   pData
}
    
Post 30 Oct 2012, 02:32
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