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macos (osx) - assembly language link error on macos

Assembly language link error on macOS

An error occurred when trying to link the source code in Shosuisha's "Low Level Programming" on the mac terminal. I tried writing and setting the environment while looking at the Github page of this book, but I couldn't solve it anyway, so I would like to lend my wisdom.

Github for Low Level Programming: https://github.com/Apress/low-level-programming

Error message 
% nasm -fmacho64 hello.asm&&ld hello.o&&./a.out
Undefined symbols for architecture x86_64:
  "_main", referenced from:
     implicit entry/start for main executable
ld: symbol (s) not found for architecture x86_64
Applicable source code 
global start
          section .text
start: mov rax, 0x02000004
          mov rdi, 1
          mov rsi, message
          mov rdx, 13
          syscall
          mov rax, 0x02000001
          xor rdi, rdi
          syscall
          section .data
message: db "Hello, World", 10

I changed what was originally _start to start, or changed it to main or _main.

Supplemental information (FW/tool version etc.)

mid-2012 13inch macbook air
intel core i5
macOS Catalina version 10.15.1
NASM version 2.14.02 compiled on Sep 28 2019

Append otn

2019/11/03 00:50

  I saw it as

_main.
  There are two places in start, have you both _main?

If both are _main

ld: dynamic main executables must link with libSystem.dylib for architecture x86_64
Another error message was

. Link and run

% nasm -fmacho64 hello.asm&&ld hello.o&&./a.out
It remains

. Thanks for your advice.

asm-san

2019/11/03 01:20

  

On github
  >Linking: ld -macosx_version_min 10.7.0 -lSystem -o hello_world
  Did you try this option?

If i try to link with that option

ld: warning: -arch not specified
ld: warning: ignoring file /usr/lib/libSystem.dylib, missing required architecture unknown in file /usr/lib/libSystem.dylib (2 slices)
Undefined symbols for architecture unknown:
  "start", referenced from:
     implicit entry/start for main executable
ld: symbol (s) not found for architecture unknown


The message has changed. By the way, the two parts that were the contents ofstartwere changed to_mainin response to otn's indication. Thanks for your advice.

macos(osx) github programminglanguage assemblylanguage
  • Answer # 1

    I think the github article about command line option specification was old at the time of writing (two years ago), and the target macOS version was also old. I tried it with macOS Mojave, but it was assembled by replacing the "start" with "_main" in the two places that were pointed out in the comments, and removing the "-macosx_version_min" option of theldcommand I was able to link with. Questioner's macOS is Catalina, but for reference.

    bash-3.2 $cat hello2.asm
          global _main
          section .text
_main: mov rax, 0x02000004
          mov rdi, 1
          mov rsi, message
          mov rdx, 13
          syscall
          mov rax, 0x02000001
          xor rdi, rdi
          syscall
          section .data
message: db "Hello, World", 10
bash-3.2 $nasm -fmacho64 hello2.asm
bash-3.2 $ld hello2.o -lSystem -o hello2
bash-3.2 $./hello2
Hello, World
bash-3.2 $

  • Answer # 2

    Are you aware of the cause (s) of Undefined symbols for architecture x86_64 :?

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