C中的内联汇编

Question

#include<stdio.h>
#include<stdlib.h>

int main (void)
{
 int a=10, b;
 asm ("movl %1, %%eax;
       movl %%eax, %0;"
      :"=r"(b)        /* output */
      :"r"(a)         /* input */
      :"%eax"         /* clobbered register */
     );
 printf("%d", b);
 system("pause");
}

我是一个新手，我复制了昨天买的书中的示例代码，但是当我编译我的第一个 asm 代码时，我刚刚从下面列出的 GCC-mingw32 编译器报告了一些警告和错误：

In function 'main':
line 7 --> warning: missing terminating " character
line 7 --> error: missing terminating " character
line 8 --> error: expected string literal before 'movl'
line 8 --> warning: missing terminating " character
line 8 --> error: missing terminating " character

如何编译成功？在此先感谢:-)

Answer 1

每条指令都应该放在双引号中 "" as "movl %1, %%eax;"

Answer 2

asm 代码的前两行必须有左引号和右引号，如下所示：

#include<stdio.h>
#include<stdlib.h>

int main (void)
{
int a=10, b;
asm ("movl %1, %%eax;"
"movl %%eax, %0;"
:"=r"(b) /* output */
:"r"(a) /* input */
:"%eax" /* clobbered register */
);
printf("%d", b);
system("pause");
}