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c++initializationglobal-variablesconstants
weeo
weeo

Reputation: 2799

what's the formal way to initialize extern const variable?

I'm using a .h file to put all the global variables in one file to make sure all files can access the same value. But i have a const int, I wonder where should I inisilize it?

.h:

#ifndef globalVar_H
#define globalVar_H


const int MAXCPU;
const int MAXPreBorder;

#endif

.cpp:

int MAXCPU=12;
int MAXPreBorder=20;

I think I should declare in the .h file and initialize in the .cpp file. But the compiler said:

error: non-type template argument of type 'int' is not an integral constant expression

If I initialize in the .h file. the compiler would not complain.. I wonder if this is the right way?

.h:

#ifndef globalVar_H
#define globalVar_H


const int MAXCPU=12;
const int MAXPreBorder=20;

#endif

.cpp:

//nothing?

Upvotes: 2

Views: 2581

Answers (2)

Jerry Coffin
Jerry Coffin

Reputation: 490358

A const variable is also (by default) static, so you have a unique one for each .cpp file in which the header is included.

As such, you normally want to initialize it "in place", since the instance defined in one TU won't be the same as the instance you initialized in your source file.

Upvotes: 3

greatwolf
greatwolf

Reputation: 20858

globalVar.h:

#ifndef globalVar_H
#define globalVar_H


extern const int MAXCPU;
extern const int MAXPreBorder;

#endif

globalVar.cpp:

const int MAXCPU = 12;
const int MAXPreBorder = 20;

Upvotes: 2

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