Question

我在原始linux内核代码中找到了以下内容。（link）

static inline _syscall0(int,fork)
static inline _syscall0(int,pause)
static inline _syscall0(int,setup)
static inline _syscall0(int,sync)

它不能是函数调用，因为static inline带有前缀。它不能是原型，因为函数不能在C中重载。最后没有分号。这是什么？

此外，它之前是此评论（如果您也可以解释这一点）

/*
 * we need this inline - forking from kernel space will result
 * in NO COPY ON WRITE (!!!), until an execve is executed. This
 * is no problem, but for the stack. This is handled by not letting
 * main() use the stack at all after fork(). Thus, no function
 * calls - which means inline code for fork too, as otherwise we
 * would use the stack upon exit from 'fork()'.
 *
 * Actually only pause and fork are needed inline, so that there
 * won't be any messing with the stack from main(), but we define
 * some others too.
 */

Answer 1

因为_syscall0是macro（在unistd.h中）：

#define _syscall0(type,name) \
type name(void) \
{ \
type __res; \
__asm__ volatile ("int $0x80" \
        : "=a" (__res) \
        : "0" (__NR_##name)); \
if (__res >= 0) \
        return __res; \
errno = -__res; \
return -1; \
}

简化示例：

#define call(type,name) \
    type name(void) \
    {return 0;}

static inline call(int,func)

int main(void)
{
    return func();
}

扩展为：

static inline int func(void) {return 0;}

int main(void)
{
    return func();
}

功能原型与否？

1 个答案: