C++

Forum

 
 
shared object problem

nemobluesix (2)
Hello all,

I'm writing a program that uses (one at a time) many similar objects based on a common one with some data/functions overwritten. I thought that would be easier to dynamically load the custom objects using polymorphism.

This is the setup:
baseclass - common data and functions
childclass1...n - different types of operations on the objects
module1..n - object with specific data and/or functions overwritten
mainprogram - loads modules/objects based on program arguments and executes some function in them

The problem is that running the main program gives me a segfault :(

Here are the files (might be more clear than my explanations :) )

$ ls -1 *.cpp *.h
baseclass.cpp
baseclass.h
childclass.cpp
childclass.h
mainprogram.cpp
module1.cpp
module2.cpp


file: baseclass.cpp
1
2
3
4
5
6
7
 
#include "baseclass.h"
#include <iostream>

using namespace std;

void BaseClass::execute(){ cout<<"executed from BaseClass x is " << x << endl; }

file: baseclass.h
1
2
3
4
5
6
7
8
9
10
11
 
#ifndef  BASECLASS_FILE_HEADER_INC
#define  BASECLASS_FILE_HEADER_INC

class BaseClass{
        public:
                int x;
                virtual void execute();
};

#endif   /* ----- #ifndef BASECLASS_FILE_HEADER_INC  ----- */

file: childclass.cpp
1
2
3
4
5
6
7
8
 
#include "childclass.h"
#include <iostream>

using namespace std;

void ChildClass::execute(){
        cout << "executed from ChildClass x is " << x << endl;
}

file: childclass.h
1
2
3
4
5
6
7
8
9
10
11
12
 
#ifndef  CHILDCLASS_FILE_HEADER_INC
#define  CHILDCLASS_FILE_HEADER_INC

#include "baseclass.h"

class ChildClass: public BaseClass{
        public:
                void execute();
};

#endif   /* ----- #ifndef CHILDCLASS_FILE_HEADER_INC  ----- */

file: mainprogram.cpp
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
 
#include <stdlib.h>
#include <stdio.h>
#include <dlfcn.h>
#include <string.h>

#include "baseclass.h"
//#include <iostream>

using namespace std;

int main (int argc, char *argv[])
{
        void *handle;
        BaseClass *a=NULL;
        char *error, dll[9];

        if(argc==1) strcpy(dll,"./module1.so");
        else strcpy(dll,"./module2.so");

        handle = dlopen (dll, RTLD_LAZY);
        if (!handle) {
                fputs (dlerror(), stderr);
                exit(1);
        }

        a = (BaseClass*)dlsym(handle, "obj");
        if ((error = dlerror()) != NULL)  {
                fputs(error, stderr);
                exit(1);
        }

        a->execute();
        dlclose(handle);
        return 0;
}

file: module1.cpp
1
2
3
4
5
6
7
8
9
10
 
#include "childclass.h"
#include "baseclass.h"

class Module1: public ChildClass{
        public:
                Module1(){
                        int x=1;
                }
} mobj;
BaseClass *obj=&mobj;

file: module2.cpp
1
2
3
4
5
6
7
8
9
10
 
#include "childclass.h"
#include "baseclass.h"

class Module1: public ChildClass{
        public:
                Module1(){
                        int x=2;
                }
} mobj;
BaseClass *obj=&mobj;


compilation:
g++ -c baseclass.cpp -o baseclass.o
g++ -c childclass.cpp -o childclass.o

g++ -c module1.cpp -o module1.o
g++ -shared module1.o baseclass.o childclass.o -o module1.so

g++ -c module2.cpp -o module2.o
g++ -shared module2.o baseclass.o childclass.o -o module2.so

g++ -c mainprogram.cpp -o mainprogram.o
g++ mainprogram.o baseclass.o -o mainprogram -ldl

./mainprogram 
Segmentation fault (core dumped)

Any ideas?
Thx.
nemobluesix (2)
well... in case someone is interested in the solution, this how-to cleared the mist for me
http://www.faqs.org/docs/Linux-mini/C++-dlopen.html
Topic archived. No new replies allowed.