移动字符数组的值以注册x86内联汇编

Question

I'm doing an inline assembly coding with Microsoft Visual C++ 2010 Express.

I have this kind of code. The main point is I need to access each single character of an array of character. Below is just an not that relevant example, when it reach the end of the string (the terminating null character) it will jump to finish or else it will separate each character of the string with a new line.

line[10] = "I am Kevin";
format[] = "%c\n";

_asm {
  mov  ebx,0
loop:
  cmp  line[ebx],0
  jz   finish
  mov  eax, line[ebx]
  push eax
  lea  eax, format
  push eax
  call printf
  jmp  loop

finish:
  ....
}

Somehow I keep having error for this line:

mov  eax, line[ebx]

It kept on saying error C2443: operand size conflict

Answer 1

" eax " describes 32 bits of register a .

The low 8 bits of register a is al . This will move 8 bits:

mov  al, line[ebx]

Answer 2

使用零扩展字节加载insn movzx ：

  movzx  eax, line[ebx]