D Hello World in Assembly without libc

hello.d

/**

   Inspired by https://4zm.org/2024/12/25/a-simple-elf.html

   Found MacOS syscall code by luck on https://stackoverflow.com/questions/47834513/64-bit-syscall-documentation-for-macos-assembly

   ASM register explanations: https://www.tutorialspoint.com/assembly_programming/assembly_registers.htm

   Compile this with: "dmd -betterC -ofhello hello.d"
   
**/
extern(C) int main()
{
  auto hip = "hello D\n".ptr;
  size_t len = 8;

  //   write(1, message, length)
  asm {
    mov RDX, len;              // Buffer length
    mov RSI, hip;              // Message buffer
    mov EDI, 1;                // Stdout file descriptor (0x01)
    mov RAX, 0x2000004;        // write syscall number (0x01 on Linux)
    syscall;                   // Make the syscall
  }

  return 0;
}