what is the use of #ifndefs

[leo kirotawa]

it means you don't want to redefine a .h file

On Mon, Jul 20, 2015 at 7:03 AM, Ahmed Soliman
<ahmedsoliman0x666 at gmail.com> wrote:
> currently I started reading through the linux kernel and I started
> reading liunx/include/linux/list.h> I understood some of the functions
> but still I dont know what does these lines of code do
> #ifndef _LINUX_LIST_H
> #define _LINUX_LIST_H
> which exist at the very beginning of the file
> I also noticed that there is many similar ifndefs in almost any .h
> file in the kernel
> note that I understand wnat does ifndef do bu I dont understand what
> goal is it supposed to achieve at the beginning of the headerfile
>
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Leônidas S. Barbosa (Kirotawa)
blog: corecode.wordpress.com