Include guard macro query

Hi,

In Linux code we add a guard macro to avoid multiple declarations of
identifiers.
But I see some macros defined with trailing underscores.
e.g. In arch/x86/include/asm/

Normally it is defined like,

 #ifndef _ASM_X86_ALTERNATIVE_H
 #define _ASM_X86_ALTERNATIVE_H

But in some files I see trailing underscore after H ,

e.g. arch/x86/include/asm/intel_scu_ipc.h


#ifndef _ASM_X86_INTEL_SCU_IPC_H_
#define  _ASM_X86_INTEL_SCU_IPC_H_

There are others files also
arch/x86/include/asm/irqflags.h
http://lxr.linux.no/#linux+v3.3.2/arch/x86/include/asm/probe_roms.h


DOES THIS TRAILING UNDERSCORE HAS SPECIAL MEANING ???

Thanks
-- 

Pritam Bankar
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