The source code that you have been using is buggy for some inputs. One such input is: n 0 1 2 4 8 7, which does not detect Player 2s victory. Your goal is to identify and fix the bug, while introducing only minimal changes to the source code. Your submission should be a source code patch, usable by patch, obtained by using diff on the original and on your fixed version. You can read about diff and patch online, or by reading their manual pages: man 1 diff and man 1 patch. The total measure of your change will be computed as the sum of the binary cmp of the stripped executables, the text cmp of the sources, and the byte size of the diff patch.

The file runme.sh has the implementation, where your fixed file is named Source_fixed.asm. You must also submit a brief description text file (source1.txt) explaining what the bug was and how you fixed it. It cannot exceed 200 words If your change does not fix the bug, you get 0 points. If your change breaks any existing feature, you get 0 points. If your patch is not conforming to the default patch format or fails to apply to the original source file for any reason, you get 0 points. If your explanation exceeds 200 words, you get 0 points. Any points earned are applicable only to the homework and project components of your final grade, and these components cannot exceed their maximum grade (i.e., if you end up with a perfect score in homeworks and projects you will not get any extra credit), but is applicable to both past and future homework and projects. All valid submissions will be ranked by measure (as defined above), in ascending order. The top solution (and any other ties) will get 5% extra credit, the next best (and ties) will get 4%, then 3%, 2%, and finally, all remaining valid submissions will get 1% extra credit. If you find additional bugs, you will get an additional bug bounty of 0.5% per accepted bug, plus 1.5% for a valid solution (patch + text description), up to a maximum of additional 6% (so three fixed bugs or twelve reported bugs), and my thanks :)

runme.sh

#! /bin/bash what="Source" what2="Source_fixed" nasm -f elf64 "${what}.asm" && ld -s -o "${what}" "${what}.o" nasm -f elf64 "${what2}.asm" && ld -s -o "${what2}" "${what2}.o" bincmp=`cmp -l "${what}" "${what2}" | wc -l` asmcmp=`cmp -l "${what}" "${what2}" | wc -l` diff=`diff -d "${what}.asm" "${what2}.asm" | wc -c` sum="$bincmp+$asmcmp+$diff" total=`echo "$sum" | bc` echo "Measure score (lower is better): ${sum} = ${total}"

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this is the source code

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%define cmpb cmp byte %define decb dec byte %define incb inc byte %define xorb xor byte %define movb mov byte %define movq mov qword section .bss ; Uninitialized data buffer resb 4 pfunc resq 1 section .data ; Initialized data mdbg db "Do you want to enable debug information?", 0xA mdbgl equ $ - mdbg mPXO db "Player X" mPXOl equ $ - mPXO mplay2 db ", choose your location (0-8):", 0xA, "Current board:", 0xA mplay2l equ $ - mplay2 mwin2 db " wins!", 0xA mwin2l equ $ - mwin2 spot equ 7 ; Offset of X/O magic equ 0x17 ; Magic! =D mtie db "It's a draw (tie)!", 0xA mtiel equ $ - mtie mfinal db "Final board:", 0xA mfinall equ $ - mfinal merr db "That location is out of range or already taken.", 0xA merrl equ $ - merr pbd1 db " | | ", 0xA pbd1l equ $ - pbd1 pbd2 db "-----", 0xA pbd2l equ $ - pbd2 dbd1 db " 012345678 ", 0xA, "[" dbd1l equ $ - dbd1 board db " " ; 3x3 linearized game board bdl equ $ - board dbd2 db "]", 0xA dbd2l equ $ - dbd2 ebd1 db "Current board (hex):", 0xA, " 0 1 2 3 4 5 6 7 8 ", 0xA, "[" ebd1l equ $ - ebd1 eboard db "20 58 20 4F 20 58 20 20 4F" ; Hex linearized game board el equ $ - eboard ebd2 db "]", 0xA ebd2l equ $ - ebd2 hexdigits db '0123456789ABCDEF' mbd1 db "Current board (mem):", 0xA, "&board = 0x" mbd1l equ $ - mbd1 mboard db "FFFFFFFFFFFFFFFF" ml equ $ - mboard mbd2 db 0xA, "+offset / hex / ASCII", 0xA mbd2l equ $ - mbd2 mbd3 db "0x0/: 58h X", 0xA ; The '/' is not a typo mbd3l equ $ - mbd3 lol db 2,1,6,3,8,4,9,9, \ 2,0,7,4,9,9,9,9, \ 1,0,8,5,6,4,9,9, \ 5,4,6,0,9,9,9,9, \ 5,3,7,5,8,0,6,2, \ 4,3,8,2,9,9,9,9, \ 8,7,3,0,4,2,9,9, \ 8,6,5,4,9,9,9,9, \ 7,6,5,2,4,0,9,9 top equ lol+7 kek db 5,3,5,3,7,3,5,3,5 section .text ; Code global _start ; Export entry point print_int: ; ecx: const char* msg, edx: size_t msgl mov eax,4 ; System call number (sys_write) mov ebx,1 ; First argument: file descriptor (stdout == 1) int 0x80 ; Call kernel ret read_int: ; ecx: char* msg, ; edx: size_t msgl mov eax,3 ; System call number (sys_read) xor ebx,ebx ; First argument: file descriptor (stdin == 0) int 0x80 ; Call kernel ret check_line: ; The offsets are expected in esi and edi mov bl,[mPXO+spot] ; One mark add bl,bl ; Two marks sub bl,[board+esi] ; One mark sub bl,[board+edi] ; Zero marks jz win ret tie: ; No return, (it's a tie) mov ecx,mtie ; Second argument: pointer to message to write mov edx,mtiel+mfinall ; Third argument: message length call print_int jmp pfinalb win: ; No return, (someone won) mov ecx,mPXO ; Second argument: pointer to message to write mov edx,mPXOl ; Third argument: message length call print_int mov ecx,mwin2 ; Second argument: pointer to message to write mov edx,mwin2l ; Third argument: message length call print_int mov ecx,mfinal ; Second argument: pointer to message to write mov edx,mfinall ; Third argument: message length call print_int ; Fallthrough pfinalb: ; No return, (print final board and exit) call [pfunc] mov eax,1 ; System call number (sys_exit) xor ebx,ebx ; First syscall argument: exit code int 0x80 ; Call kernel ; No ret debug_board: mov ecx,dbd1 ; Second argument: pointer to message to write mov edx,dbd1l+bdl+dbd2l ; Third argument: message length call print_int mov ecx,8 ; Locations hexboard: mov bl,[board+ecx] mov dx,'20' cmp bl,' ' cmove ax,dx mov dx,'58' cmp bl,'X' cmove ax,dx mov dx,'4F' cmp bl,'O' cmove ax,dx mov [eboard+2*ecx+ecx],al mov [eboard+2*ecx+ecx+1],ah dec ecx jns hexboard mov ecx,ebd1 ; Second argument: pointer to message to write mov edx,ebd1l+el+ebd2l ; Third argument: message length call print_int mov ecx,mbd1 ; Second argument: pointer to message to write mov edx,mbd1l+ml+mbd2l ; Third argument: message length call print_int mov rsi,board mov rdi,mbd3 memboard: incb [rdi+3] ; Counter mov bl,[rsi] ; Mark (ASCII) mov [rdi+10],bl mov dx,'20' cmp bl,' ' cmove ax,dx mov dx,'58' cmp bl,'X' cmove ax,dx mov dx,'4F' cmp bl,'O' cmove ax,dx mov [rdi+6],ax ; Mark (hex) mov ecx,mbd3 ; Second argument: pointer to message to write mov edx,mbd3l ; Third argument: message length call print_int inc rsi cmp rsi,board+9 jne memboard movb [rdi+3],'/' ; Reset counter ret print_board: xor esi,esi ; Row nrow: mov edi,2 ; Col ncol: mov dl,[board+esi+edi] ; Src mov [pbd1+edi*2],dl ; Dst dec edi jns ncol ; Three columns mov ecx,pbd1 ; Second argument: pointer to message to write add esi,3 ; Next row cmp esi,9 ; Last row je pdone mov edx,pbd1l+pbd2l ; Third argument: message length call print_int jmp nrow pdone: mov edx,pbd1l ; Third argument: message length call print_int ret _start: ; Enable debug? mov ecx,mdbg ; Second argument: pointer to message to write mov edx,mdbgl ; Third argument: message length call print_int ; Read answer mov ecx,buffer ; Store input at location 'buffer' mov edx,2 ; Read these many bytes call read_int ; Switch case cmpb [buffer],'Y' je do_debug cmpb [buffer],'y' je do_debug cmpb [buffer],'D' je do_debug cmpb [buffer],'d' je do_debug ; Default movq [pfunc],print_board jmp play do_debug: movq [pfunc],debug_board mov ecx,15 ; Offset of last hexdigit of address mov rdx, board ; rdx will be tampered with mov rbx, hexdigits ; Table memheader: mov rax,rdx ; Need nibble in al and rax,0x000000000000000f xlatb ; al updated mov byte [mboard+ecx],al dec ecx mov rax,rdx ; Need nibble in al and rax,0x00000000000000f0 shr rax,4 ; This time, higher nibble xlatb ; al updated mov byte [mboard+ecx],al shr rdx,8 ; Next byte (two nibbles) dec ecx jns memheader jmp play invalid: mov ecx,merr ; Second argument: pointer to message to write mov edx,merrl ; Third argument: message length call print_int ; Fallthrough play: ; Print messages and board mov ecx,mPXO ; Second argument: pointer to message to write mov edx,mPXOl+mplay2l ; Third argument: message length call print_int call [pfunc] ; Read input mov ecx,buffer ; Store input at location 'buffer' mov edx,2; ; Read these many bytes call read_int ; Validate movzx eax, byte [buffer] sub al,'0' ; Poor man's atoi cmp al,8 ja invalid ; Range is valid cmpb [board+eax],' ' ; Is empty? jne invalid ; Move is fully valid mov bl,[mPXO + spot] mov [board+eax],bl ; Place mark ; Check if winning move movzx ecx, byte [kek+eax] ; Terms (adjusted) pair: movzx esi, byte [lol+eax*8+ecx] dec ecx movzx edi, byte [lol+eax*8+ecx] call check_line dec ecx jns pair ; Next term pair decb [top] ; Check if tie jz tie xorb [mPXO+spot],magic ; Ready the other player's mark jmp play