Error in making DLL class in Eclipse IDE with g++ compiler - c++

Question

I make a project in Eclipse to export a dll class with g++ compiler. My OS is Ubuntu and the application will run in Ubuntu OS. I created a shared project.
I have compile error as
expected constructor, destructor, or type conversion before ‘(’ token OCR_dll.h /OCR line 19 C/C++ Problem
The error happened at #define DLLCLASS __declspec(dllexport) and how to solve the error. Thank you.
My dll codes header file is
OCR_dll.h
#ifndef OCR_DLL_H_
#define OCR_DLL_H_
#include <stdio.h>
#include <opencv/cv.h>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <tesseract/baseapi.h>
#include <iostream>
#include "Define.h"
#ifdef EXPORT
#define DLLCLASS __declspec(dllexport)
#else
#define DLLCLASS __declspec(dllimport)
#endif
using namespace cv;
#ifdef __cplusplus
extern "C" {
#endif
namespace VIDEOANALYTICS_PLATFORM {
class iOCR{
public:
virtual ~iOCR(){}
virtual int preProcessing(Mat &img) = 0;
virtual int textExtraction(Mat &img) = 0;
};
class OCR : public iOCR{
public:
OCR(){}
~OCR(){ ; }
int preProcessing(Mat &img);
int textExtraction(Mat &img);
private:
};
extern "C"{ DLLCLASS iOCR* __stdcall createOCRObject(); };
}
#ifdef __cplusplus
}
#endif
#endif /* OCR_DLL_H_ */

Answer 1

I got the solution. In Linux environment, dll is called shared library.
The way I create the shared lib is
Headerfile
#ifndef OCR_DLL_H_
#define OCR_DLL_H_
#include <opencv/cv.h>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <tesseract/baseapi.h>
#include <iostream>
#include "Define.h"
using namespace cv;
namespace VIDEOANALYTICS_PLATFORM {
class iOCR{
public:
virtual ~iOCR(){}
virtual int preProcessing(Mat &img) = 0;
virtual int textExtraction(Mat &img) = 0;
};
class OCR : public iOCR{
public:
OCR(){}
~OCR(){ ; }
int preProcessing(Mat &img);
int textExtraction(Mat &img);
private:
};
}
#endif /* OCR_DLL_H_ */
CPP file
#include "OCR_dll.h"
namespace VIDEOANALYTICS_PLATFORM {
extern "C" iOCR* create_object(){
iOCR *p = new OCR();
return p;
}
extern "C" void destroy_object( iOCR* object )
{
delete object;
}
int OCR::preProcessing(Mat &img){
return SUCCESS;
}
int OCR::textExtraction(Mat &img){
return SUCCESS;
}
}
MAKEFILE
g++ -fPIC -shared OCR_dll.cpp -o OCR_dll.so
Then we can create shared lib object for a class.