Undefined reference of header variable in Qt C++

Question

I am having a problem with my program where in I declared the variable from a header file and execute it on a CPP file. I am getting an error which is the undefined reference to the variable.

here a sample code of my project:

CPP FILE

#include "function.h"
CClass::CClass() : m_Db(HOST,USER,PASSWORD,DATABASE)
{
   ...
}

HEADER FILE

#ifndef CONNECTION_H
#define CONNECTION_H

#include "crypt.h"

extern CCrypt *c_crypting;

#define HOST c_crypting->Decrypt_Host()
#define USER c_crypting->Decrypt_Username()
#define PASSWORD c_crypting->Decrypt_Password()
#define DATABASE c_crypting->Decrypt_Database()

#endif // DBCONNECTION_H

if i run this code I get an error of "undefined reference to 'c_crypting'"

Mat · Accepted Answer · 2011-06-09 05:31:11Z

2

This line in your header file:

extern CCrypt *c_crypting;

does not create a c_crypting pointer. It only says "one of my code modules will have a pointer to CCrypt that is called c_crypting" so that the other code files can use that. You'll need to have something like:

CCrypt *c_crypting; // possibly '= 0;'

in one of your .cpp files, and initialize it properly somewhere.

answered Jun 9, 2011 at 5:31

Mat

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2 Comments

Andro Miguel M. Bondoc Over a year ago

hmm.. is there a way where i wont initialize the CCrypt*c_crypting in a CPP file?

Mat Over a year ago

Well, not really. It has to be initialized somewhere, otherwise it won't point to anything so your code will crash the first time you try to do something with it.

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