Linker Error while linking .lib files "nresolved external symbol"

[programmer1234]

Hi guys,

I have project named TestingDLL(Win32 DLL project). It has the following header file

(The code has been taken from a site which I dont remember but for discussion purpose this is fine)
sampledll.h
---------------
#ifndef INDLL_H
#define INDLL_H

#ifdef EXPORTING_DLL
extern __declspec(dllexport) void HelloWorld() ;
#else
extern __declspec(dllimport) void HelloWorld() ;
#endif
#endif

and a .cpp file
sampldll.cpp
---------------
#define EXPORTING_DLL
#include "sampledll.h"
#include <stdio.h>

void HelloWorld()
{
printf("hello");
}


I have build this project and I got the TestingDLL.lib sucessfully after the build.

I have another project CallingDLL(Win 32 Console application) whose code is as follows
calling.cpp
--------------
#include "sampledll.h"
#pragma comment(lib,"TestingDLL.lib")
int main()
{
HelloWorld();
return 0;
}

this code calls the library function Helloworld(). Now I went to projects->settings->link->input
and specified the .lib file name and the path to find it. I also made chages in C/C++->preprocessor->Additional include directories and added the path where sampledll.h is found.

I always get

compiling...
calling.cpp
Linking...
calling.obj : error LNK2001: unresolved external symbol "__declspec(dllimport) void __cdecl HelloWorld(void)" (__imp_?HelloWorld@@YAXXZ)
Debug/CallingDll.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

CallingDll.exe - 2 error(s), 0 warning(s)

I have also tried some other ways like going to tools->options->Directories and adding the paths but still I get the same error.

It would be great help if someone tells me in a systematic manner on how to link a .lib file to another project.

Thanks

[Marc G]

See documentation here: http://msdn.microsoft.com/en-us/libr...z2(VS.71).aspx

[hypheni]

seems to be you did it in correct manner, may be you missing proper path.. check all settings once again..

[VictorN]

When DLL (und lib) is created (compiled( the EXPORTING_DLL is defined. So the type of the HelloWorld() is

extern __declspec(dllexport) void HelloWorld() ;

But if EXPORTING_DLL is not defined in exe project then HelloWorld() would be declared as

extern __declspec(dllimport) void HelloWorld() ;

And it seems to be the case here: the linker in exe project looks for "__declspec(dllimport) void __cdecl HelloWorld(void)" while the lib contains only "__declspec(dllexport) void __cdecl HelloWorld(void)"

[programmer1234]

Hi guys
thanks for the replies. I havent got rid of the previous problem but I tried a new toy project to understand the linking. It is as follows

code for dll
example.cpp
---------------

/ Example.cpp : Defines the entry point for the DLL application.
//

#include "stdafx.h"

// This function is used to calculate the total area of a parallelepiped rectangle
double BoxArea(double L, double H, double W);
// This function is used to calculate the volume of a parallelepiped rectangle
double BoxVolume(double L, double H, double W);
// This function is used to get the dimensions of a rectangular parallelepiped
// calculate the area and volume, then pass the calculated values to the
// function that called it.
extern "C" __declspec(dllexport)void BoxProperties(double Length, double Height,
double Width, double& Area, double& Volume);

BOOL APIENTRY DllMain( HANDLE hModule,
DWORD ul_reason_for_call,
LPVOID lpReserved
)
{
return TRUE;
}

double BoxArea(double L, double H, double W)
{
return 2 * ((L*H) + (L*W) + (H*W));
}

double BoxVolume(double L, double H, double W)
{
return L * H * W;
}

void BoxProperties(double L, double H, double W, double& A, double& V)
{
A = BoxArea(L, H, W);
V = BoxVolume(L, H, W);
}

I build the project and there were no errors and I got the .lib and .dll files upon building the project.

There is another project where I am trying to use the .lib generated above. I have copied the Example.lib, Example.dll and Example.obj to the new project folder . I also added these files to the project. In the project->settings->link->input I appended Example.lib to the Object/Library module text box . I wrote the following cpp code in the new project.
test.cpp
-----------
#include <iostream>

extern "C" __declspec(dllimport)void BoxProperties(double L, double H,
double W, double& A, double& V);

int main()
{
double Length, Height, Width, Area, Volume;

cout << "Enter the dimensions of the box\n";
cout << "Length: ";
cin >> Length;
cout << "Height: ";
cin >> Height;
cout << "Width: ";
cin >> Width;

BoxProperties(Length, Height, Width, Area, Volume);

cout << "\nProperties of the box";
cout << "\nLength: " << Length;
cout << "\nHeight: " << Height;
cout << "\nWidth: " << Width;
cout << "\nArea: " << Area;
cout << "\nVolumne: " << Volume;

cout << "\n\n";

return 0;
}

After building the code I get the following linker error(no previous linker errors ):

--------------------Configuration: Exampletest - Win32 Debug--------------------
Linking...
Creating library Debug/Exampletest.lib and object Debug/Exampletest.exp
LIBCMTD.lib(crt0.obj) : error LNK2001: unresolved external symbol _main
Debug/Exampletest.exe : fatal error LNK1120: 1 unresolved externals
Error executing link.exe.

Exampletest.exe - 2 error(s), 0 warning(s)

Guys help me resolve this

Thanks

[VictorN]

Please, edit your post adding Code tags around code snippets. Otherwise your code is absolutely unreadable!

[programmer1234]

Thanks for the suggestion Victor! I will take care of that in my future posts.

Well thanks for all the help you guys have done. I finally resolved my issues regarding linker error. I will update this post with step by step procedure I figured out to make a dll and use it in other applications.