require_once

[teguh123]

is a PhP languange

What's the equivalent in C++

[4Gb4jE8b]

well... considering i don't know PhP i have no idea from your question. Maybe if you told us what it does?

[Gladdok]

Looks like an inclusion guard.

In C++ add to the top of your headers:
#ifndef HEADERNAME_H
#define HEADERNAME_H

and on the last line of the header:
#endif

[teguh123]

Hmm... I am trying to find a way around it actually. No way isn't it :)

That seems to be pretty messy. Why can't there be a macro #includeonce is beyond me.

[sohguanh]

That seems to be pretty messy. Why can't there be a macro #includeonce is beyond me.

The answer is simple. The PHP creator decide on a new keyword instead of re-use C syntax for similar features.

In Java it is the keyword import which is similar in concept.

[teguh123]

Visual C++ has

#pragma once

Not all implementation support that

Bravo microsoft!

[lionishy]

teguh123>#pragma once

Nevertheless, with #pragma once the one to be included contains the include rule, while in php with require_once the one, that includes, contains the rule.

#pragma once make no difference with Gladdok proposal.

[kbw]

http://www.cplusplus.com/forum/beginner/7877/#msg36635

[Duthomhas]

I always use both. This gives the superpowers that #pragma once gives, but falls back on something better if it fails.

#pragma once
#ifndef FOOEY_HPP
#define FOOEY_HPP

...

#endif 

[teguh123]

Actually I have an idea.

Why not put the guard on the file that includes like lionishy said

#ifndef FOOEY_HPP
#define FOOEY_HPP
#include "fooey.h"
#endif 

Tada....

No need a include guard on the .h file

with one small catch,

for some reason putting include guard on the .h file is far more popular.

Why?

[kbw]

Then in some other file someone in your team does the same again in a different file:

#ifndef F00EY_HPP
#define F00EY_HPP
#include "fooey.h"
#endif  

and it breaks your build. 2 days later, you find it has 0 instead of O.