c - Gcc 内联 ASM 输入变量

Question

我有这段代码:

void  geninterrupt (int x) {
    __asm__(
    "movb x, %al \n"
        "movb %al, genint+1 \n"
        "jmp genint \n"
    "genint: \n"
        "int $0 \n"
    );
}

如何让 movb 使用 geninterrupt() 的参数？

Answer 1

您需要正确使用约束字段:

void  geninterrupt (int x) {
  __asm__("  movb %[x], %%al \n"
          "  movb %%al, genint+1 \n"
          "  jmp genint \n"
          "genint: \n"
          "  int $0 \n"
         : /* no outputs */
         : [x] "m" (x) /* use x as input */
         : "al" /* clobbers %al */
         );
}

Here's a good how-to about GCC inline assembly和一个 link to the relevant GCC documentation .

编辑:因为您的 GCC 似乎无法处理带标签的操作数