在C语言中，变量名中的双下划线表示什么?
问题描述：
可能重复:
为什么人们这么多使用__(双下划线) C ++
Possible Duplicate:
Why do people use __(double underscore) so much in C++
我正在研究Linux内核编程代码.
I was studying the Linux kernel programming code.
有些数据结构和功能以双下划线开头，例如:
There are some data structures and functions which start with a double underscore like:
__u32 len
与普通变量有何不同?
答
这表示它是系统保留的名称. C标准规定，所有以两个下划线(或下划线和大写字母)开头的名称均保留供系统或编译器使用，不应在应用程序代码中定义.
It means it's a system-reserved name. The C standard says that all names beginning with two underscore, or underscore and capital letter, are reserved for the use of the system or compiler and should not be defined in application code.