How to use c++ objects in Delphi - c++

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.