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"global redefined" - C++

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Started by Element of Power February 15, 2010 04:17 AM

5 comments, last by Element of Power 14 years, 2 months ago

Element of Power

122

Author

February 15, 2010 04:17 AM

I've got this "global" library for my project, which will include all the standard includes and define all the "project-wide" globals, but I have a problem: when I try to add a global variable in, VC++, and I include the globals library in more than one file, I get this "globals redefined". Here is my code:

#ifndef __GLOBALS__
#define __GLOBALS__

#include "DarkGDK.h"
#include "d3dfunc.h"

#define SWIDTH  600
#define SHEIGHT 600
#define SDEPTH  32

struct Globals
{
	bool end;
} globals;

#endif

I've also tried

#pragma once

, but that didn't work either. How to I declare these globals?

GregMichael

135

February 15, 2010 05:09 AM

Try this (just guessing...) in the header file...

struct Globals
{
bool end;

};

extern Globals globals;

This defines what a Globals structure looks like rather than creating one.

Then you'll need to create a Globals structure once in a cpp file...

Globals globals;

Or just avoid globals altogether :)

gumpy

795

February 15, 2010 05:25 AM

See problem #4 in this article for a detailed explanation.

This space for rent.

Element of Power

122

Author

February 15, 2010 09:12 AM

But I need my globals to be usable in most of my core cpp files - I can't redefine them in each file, it just wouldn't work...

Brother Bob

10,350

February 15, 2010 09:22 AM

Quote:Original post by Element of Power
But I need my globals to be usable in most of my core cpp files - I can't redefine them in each file, it just wouldn't work...

Problem #4 as gumpy linked explains how to do that. Declare your globally accessible variables as extern and then define them in exactly one source file, instead of defining them in the header file. It's the multiple definition that is causing your error.

jpetrie

13,220

February 15, 2010 10:01 AM

You should also be aware that such "global" headers can introduce subtle compiler errors if they are including a lot of your own files, and can also drastically increase compile times, if implemented incorrectly.

Element of Power

122

Author

February 15, 2010 11:20 AM

Quote:Problem #4 as gumpy linked explains how to do that. Declare your globally accessible variables as extern and then define them in exactly one source file, instead of defining them in the header file. It's the multiple definition that is causing your error.

Ah, I didn't realise there are multiple pages. I'll try that.

"global redefined" - C++

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"global redefined" - C++

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