How to use c++ objects in Delphi

Question

I am making a DLL file for delphi applicaton in visual studio. I am following http://rvelthuis.de/articles/articles-cppobjs.html link to make the dll.My code is as follows

DLL_CLASS.h

#pragma once


using namespace std ;
#include "stdafx.h"
class DLL_CLASS
{

    private:

    public:
        int TestValue;
        char*  getConnectedInverters (char* path);
         char*  getInverterParameters (int Device_Handle);
         char*  getInverter_SPOT_READINGS(int Device_Handle);
         char*  getPassword_varification();
         char*  get_Inverter_password();
         char*  get_Device_name(int Device_handle);
         int    get_Device_handel();
         char*  setAllInverterParameters(int Device_Handle,char* path_to_XML);
        char*  setYasdi_Reset_and_Shutdown();
         char*  get_Encryption(char* string_to_encrypt);
         char*  deviceXmlname();
         char*  RegExp(string Device_type);
        int Get_inst_code_Channel(int Device_Handle);
         char*  set_One_InverterParameters(int Device_Handle,int Channel_handle,string Value);

          DLL_CLASS();
        virtual ~DLL_CLASS();
};

and other file code is as below

#include "stdafx.h"
#include "DLL_CLASS.h"
#include <tchar.h>
#include <windows.h>;




// define a macro for the calling convention and export type
#define EXPORTCALL __declspec(dllexport) __stdcall
typedef DLL_CLASS *ConsoleHandle;
extern "C"
{

    ConsoleHandle EXPORTCALL NewConsole(void)
    {
        return new DLL_CLASS();
    }

    void EXPORTCALL DeleteConsole(ConsoleHandle handle)
    {
        delete handle;
    }

    char* EXPORTCALL NEW_getConnectedInverters(ConsoleHandle handle ,char* path)
    {
        handle->getConnectedInverters (path);
    }

    char* EXPORTCALL NEW_getInverterParameters (ConsoleHandle handle ,int Device_Handle)
    {
        handle->getInverterParameters(Device_Handle);
    }

    char* EXPORTCALL NEW_getInverter_SPOT_READINGS(ConsoleHandle handle,
        int Device_Handle)
    {
        handle->getInverter_SPOT_READINGS(Device_Handle);
    }

    char* EXPORTCALL NEW_getPassword_varification(ConsoleHandle handle)
    {
        handle->getPassword_varification();
    }

    char* EXPORTCALL NEW_get_Inverter_password(ConsoleHandle handle)
    {
        handle->get_Inverter_password();
    }

    char* EXPORTCALL NEW_get_Device_name(ConsoleHandle handle,
        int Device_handle)
    {
        handle->get_Device_name(Device_handle);
    }

    int EXPORTCALL NEW_get_Device_handel(ConsoleHandle handle)
    {
        return handle->get_Device_handel();
    }

    char* EXPORTCALL NEW_setAllInverterParameters(ConsoleHandle handle,int Device_Handle,char* path_to_XML)
    {
        return handle->setAllInverterParameters( Device_Handle, path_to_XML);
    }

    char* EXPORTCALL NEW_setYasdi_Reset_and_Shutdown(ConsoleHandle handle)
    {
        handle->setYasdi_Reset_and_Shutdown();
    }

    char* EXPORTCALL NEW_get_Encryption(ConsoleHandle handle,
        char* string_to_encrypt)
    {
        handle->get_Encryption(string_to_encrypt);
    }
    char* EXPORTCALL NEW_deviceXmlname(ConsoleHandle handle)
    {
        handle->deviceXmlname();
    }
    char* EXPORTCALL RegExp(ConsoleHandle handle,
        string Device_type)
    {
        handle->RegExp( Device_type);
    }
    char* EXPORTCALL NEW_set_One_InverterParameters(ConsoleHandle handle,
        int Device_Handle,int Channel_handle,string Value)
    {
        handle->set_One_InverterParameters( Device_Handle,Channel_handle, Value);
    }
    int  EXPORTCALL NEW_Get_inst_code_Channel(ConsoleHandle handle,
        int Device_Handle)
    {
        handle->Get_inst_code_Channel(Device_Handle);
    }
} // extern "C"

#pragma argsused
int WINAPI DllEntryPoint(HINSTANCE hinst, unsigned long reason, void* lpReserved)
{
    return 1;
}

But this Give me error as below

1>------ Build started: Project: inverter_library, Configuration: Release Win32 ------
1>  flatten.cpp
1>flatten.cpp(5): warning C4067: unexpected tokens following preprocessor directive - expected a newline
1>flatten.cpp(26): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(27): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(27): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(31): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(32): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(32): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(36): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(38): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(38): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(42): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(43): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(43): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(47): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(48): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(48): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(52): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(54): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(54): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(63): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(64): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(64): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(68): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(69): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(69): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(73): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(75): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(75): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(78): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(79): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(79): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(82): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(84): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(84): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(87): error C2059: syntax error : '__declspec(dllexport)'
1>flatten.cpp(89): error C2143: syntax error : missing ';' before '{'
1>flatten.cpp(89): error C2447: '{' : missing function header (old-style formal list?)
1>flatten.cpp(99): warning C4068: unknown pragma
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========

Can anyone suggest me Why this error is coming

I tried to find the solution but I could not find it....

Answer 1

You need to place the __declspec(dllexport) before the return value, and the __stdcall after the return value. For example:

__declspec(dllexport) int __stdcall foo(...)

Your macro places them together, after the function return value. Hence the syntax error. So if you want both in a single macro, you need a parameterized macro that takes the return type as a parameter.

It's simpler and clear to be explicit and skip the macros and write it out longhand, in my view. I suggest that you shun macros unless they give significant benefit in comparison to non-macro alternatives. In this case I see no such benefit.

Note that some of your flattening functions are missing return statements. And you also need to be clear on the lifetime of the char* pointers that you return. I trust you are already on top of that.