C struct getting doubly included

Question

I can't figure this out...

I have object.h which looks like so

struct basicObject {
       int x, y;
}

void objectSet (int x, int y);

Now I need to include object.h in my main file but I also need the objectSet function and struct in a different file called svg.c

svg.h looks like

#define OUTPUT_FILE "output.svg"
#include "object.h"

void saveSVG (basicObject item);

But my main file also includes svg.h! So I'm getting 'redifinition errors' of struct basicObject. This clearly has something to do object.h getting included twice. How can I fix this?

If you're not compiling as C++ or have edited out a typedef, in saveSVG, you'd need struct basicObject. — Daniel Fischer
– Daniel Fischer, Commented Oct 4, 2012 at 22:40

rid · Accepted Answer · 2012-10-04 22:11:58Z

4

You should use include guards if you plan on using #include to refer to the same header file more than once, but you only need to include it the first time.

answered Oct 4, 2012 at 22:11

rid

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Comments

Bill Lynch · Accepted Answer · 2012-10-04 22:17:30Z

2

There are two main options. In your header file, do

#pragma once

or wrap the entire header file in:

#ifndef MY_SVG_H
#define MY_SVG_H

... your code ...

#endif

2 Comments

rid Over a year ago

(do note however that #pragma once is non-standard)

MandarineBleue Over a year ago

Suggest you to make both, #pragma once #ifndef .. #define .. => You keep advantage of fast compilation with pragma once, but portability with define.

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