Question

Consider:

int main()
{
    __asm__("movl $0x1,%%eax;
            movl $0x0,%%ebx;
            int $0x80;
            ":::"eax","ebx");
}

I try to simulate the behavior of exit() in Linux. But in modern Linux I find it’s very difficult to do that since some exit handlers will be called after exit().

So I write an old version of exit(). Maybe 10 years ago you can find it in some code.
I compile it with GCC.

gcc -o exit exit.c

And it gives me these messages.

exit.c: In function ‘main’:
exit.c:3:13: warning: missing terminating " character [enabled by default]
exit.c:3:5: error: missing terminating " character
exit.c:4:13: error: expected string literal before ‘movl’
exit.c:6:27: warning: missing terminating " character [enabled by default]
exit.c:6:13: error: missing terminating " character

I have carefully examined my code and I don’t think my code is wrong. So what is that?

Answer 1

You cannot have embedded newlines inside quoted strings

// bad
"two
lines"

Rewrite as

// good
"two\n"
"lines"

The preprocessor will join the strings seamlessly, to

"two\nlines"