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I'm trying to add arrA and arrB and store the values into arrC and print out.. once I run the code it takes me to infinite loop. How can I break the loop? Any suggestions greatly appreciated.

ExitProcess PROTO
WriteHex64  PROTO
.data
 arrA BYTE 10h, 30h
 arrB BYTE 0E0h, 40h
 arrC BYTE 0, 0
 string BYTE ", ", 00h 

 .code
 main PROC
   nop

   mov rdi, OFFSET arrA
   mov rsi, OFFSET arrB
   mov rbx, OFFSET arrC
   mov rdx, OFFSET string
 
   mov rcx, LENGTHOF arrA

   mov rax, 0

   L1:
     mov rax, [rdi]
     mov rax, [rsi]
     add rdi, TYPE arrA
     add rsi, TYPE arrB
     mov [rbx], rax
     add rbx, TYPE arrC
     call WriteHex64
     call WriteString
     loop L1
     
   nop
     
   mov ecx, 0
   call ExitProcess
 main ENDP
 END
Lin
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    Are you familiar with [x64 calling conventions](https://learn.microsoft.com/en-us/cpp/build/x64-calling-convention?view=msvc-160)? Assuming that your `WriteHex64` and `WriteString` functions follow them, they need their arguments in certain registers which you don't seem to be loading, and they may overwrite registers that you don't seem to be saving (especially `rcx`). – Nate Eldredge Mar 08 '21 at 01:33
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    Also, is this really your entire code, and how are you building it? There should be some way to mark your program's `main` function or other entry point. Otherwise you can't be sure that it will run the code you want it to. – Nate Eldredge Mar 08 '21 at 01:34
  • `. data` does that even assemble, with a space there? Also, if the loop did exit, are you sure execution doesn't just fall into something that jumps back to the top of your code? There's no exit system call. – Peter Cordes Mar 08 '21 at 03:08

0 Answers0