Thread: Sharing an object between separate modules

You need a .h file that you include in both files, containing the following.

Call it separate.h

Code:

#ifdef SEPARATE_H_INCLUDED
#define SEPARATE_H_INCLUDED

//////////////////////////////////////////////////////////////////////////
class LIBS
{
private:
   char  HABlib[100];
public:
    void setLIBS(int argc, char  *argv[])
    {
        strcpy(HABlib,"test");
    }
    char* getHABlib(void)   {return HABlib;} //return the ADDRESS of HABlib
};

//////////////////////////////////////////////////////////////////////////
extern LIBS L;
//////////////////////////////////////////////////////////////////////////
#endif

Then the two sources are

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <time.h>
#include <errno.h>
#include <iostream>

#include "separate.h"   // the file created above

using namespace std;
void funct_correlation(void);

//////////////////////////////////////////////////////////////////////////

// Create an instance of your object
LIBS L;

//////////////////////////////////////////////////////////////////////////
int main( int argc, char *argv[] ) 
{
   L.setLIBS(argc,argv);
   printf("HAB=%s\n", L.getHABlib()  ); //print string at location of address
   funct_correlation();

   return 0;
} //end main

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/time.h>
#include <time.h>
#include <errno.h>
#include <iostream>

#include "separate.h"   // the file created above

using namespace std;

//////////////////////////////////////////////////////////////////////////
void funct_correlation(void)
{
     char HL[100];
     strcpy( HL, L.getHABlib() );
     printf("HAB from funct=%s\n", HL  ); //print string at location of address
     
     return;
}

Each .cpp file (along with it's included text) forms a "compilation unit" that must be able to be compiled into an object file separately from the other .cpp files. As it stands, separate2.cpp has no knowledge of LIBS or L. Usually you would put class LIBS in a .h file and include it in separate1.cpp and separate2.cpp so they each know about that class.

As for L, if you really want it global like you have it, then you need to let separate2.cpp know about it by adding the following at global scope in separate2.cpp:

Code:

extern LIBS L;  // indicate the existence of L without defining it here

Alternatively you could define the object locally in main and pass it to the other function:

Code:

// libs.h ////////////////////////////////////////////////////////
 
#ifndef LIBS_H
#define LIBS_H
 
#include <cstring>
 
class LIBS
{
private:
    char  HABlib[100];
public:
    void setLIBS( int argc, char  *argv[] )
    {
        strcpy(HABlib,"test");
    }
    char* getHABlib(void) { return HABlib; }
};
 
#endif
 
// separate1.cpp /////////////////////////////////////////////////
 
#include <iostream>
#include "libs.h"
void funct_correlation( LIBS &libs );
using namespace std;
 
int main( int argc, char *argv[] ) 
{
   LIBS L;
   L.setLIBS(argc, argv);
   cout << "HAB=" << L.getHABlib() << "\n";
   funct_correlation(L);
 
   return 0;
}
 
// separate2.cpp /////////////////////////////////////////////////
 
#include <iostream>
#include <cstring>
#include "libs.h"
using namespace std;
 
void funct_correlation( LIBS &L )
{
     char HL[100];
     strcpy( HL, L.getHABlib() );
     cout << "HAB from funct=" << HL << "\n"; 
}

You can compile each unit separately (the -c file says to compile only, do not link yet) :

Code:

g++ -Wall -W -c separate1.cpp       # this will create separate1.o
g++ -Wall -W -c separate2.cpp       # this will create separate2.o
g++ separate1.o sepatate2.o -o separate   # this links the .o files
 
# Or you could compile and link everything at once:
g++ -Wall -W separate1.cpp separate2.cpp -o separate

BTW, we don't generally mix C-style I/O and C++-style I/O, so if you're including iostream and using cout, etc., then there's no reason to include stdio.h.
And <stdio.h> is usually spelled <cstdio> in C++; and <string.h> is <cstring>).
We also don't put (void) for an empty parameter list, but instead just write ().