Header guards and #pragma once

[The illusionist mirage]

Hello

I was making a program and had defined a file called Constants.h in it. When I tried to include it in main.cpp and in another class declaration player.h, I got an error that varible_xyz was defined more than once.

So, I googled up this issue and came to know that header guards can be used to prevent the inclusion of a file multiple times as this post says: http://www.cplusplus.com/forum/general/71787/ . But how do we use #pragma once in our codes?

I'd be very grateful if someone can give me a simple example or a link where this basic issue is addressed.

Thanks

[Catfish4]

// header file

#pragma once

#include "Stuff.hpp"

// function prototypes

void f1();
void f2();

http://en.wikipedia.org/wiki/Pragma_once
http://stackoverflow.com/questions/1143936/pragma-once-vs-include-guards

Header guards are basically a hack, which consists of using the preprocessor to "cut out" header files if they're included multiple times.

[z05DSL3A]

But how do we use #pragma once in our codes?

#pragma once
#ifndef _CONSTANTS_H_INCLUDED 
#define _CONSTANTS_H_INCLUDED 

//....

#endif 
//---END OF FILE 

Constants.h

[andywestken]

<snip>

(half read the question before replying...)

Andy