Using nasm to compile a minimal runnable example on MacOS / Darwin

; ----------------------------------------------------------------------------------------
; This is an macOS console program that writes "Hello, World" on one line and then exits.
; It uses puts from the C library.  
;
; To assemble:
;
;     nasm -fmacho64 helloworld.asm
;     clang -arch x86_64 helloworld.o -o helloworld
;
; To run:
;
;     ./helloworld
;
; ----------------------------------------------------------------------------------------

          global    _main
          extern    _puts

          section   .text
_main:    push      rbx                     ; Call stack must be aligned
          lea       rdi, [rel message]      ; First argument is address of message
          call_puts                   ; puts(message)
          pop       rbx                     ; Fix up stack before returning
          ret                          ; invoke operating system to exit

          section   .data
message:  db        "Hello, World", 10      ; note the newline at the end