Linking Error

[tenpoundbear]

Hi guys,

So I have this little solution with 3 projects and when I compile I am getting a linking error. I am using Visual Studio 2010 by the way.

1.error LNK2019:unresolved external symbol_func_2 referenced in function "void_cdecl func_1(void)"(?func_1@@YAXXZ)
2.error LNK1120: unresolved externals

I am not sure why and it has been bothering me for days.

The solution is just exporting some DLL's, very simple!

****** Project 1 **************
SHARETAP32.H

#ifdef DLLEXPORTIMPORT
	#define EXPORT_IMPORT _declspec(dllexport)
#else
	#define EXPORT_IMPORT _declspec(dllimport)
#endif

extern "C" void EXPORT_IMPORT Func_2( int a );

SHARETAP32.CPP

#define DLLEXPORTIMPORT
#include "sharetap32.h"

void func_2( int a )
{
	// Stub for now!
}

****** Project 1 **************


****** Project 2 **************
WINDEF32.H

#ifdef DLLEXPORTIMPORT
	#define EXPORT_IMPORT _declspec(dllexport)
#else
	#define EXPORT_IMPORT _declspec(dllimport)
#endif

extern "C" void EXPORT_IMPORT Func_1();

WINDEF32.CPP

#define DLLEXPORTIMPORT
#include "windef32.h" 

****** Project 2 **************


****** Project 3 **************
WINTAP32.H

struct Person
{
	char *name;
	int age;
};

WINDEF32.CPP

#include "wintap32.h"
#include "sharetap32\sharetap32.h"

void Func_1()
{
	func_2( 3 );
}

****** Project 3 **************

Do you guys know what the issue is? I am pretty sure it is due to the func_2( int a ) but I am not sure.

[kbw]

The functions in the .cpp files need to be exported too, not just the prototypes. Use depends to see what's in the DLL files. BTW, if a .lib file isn't generated, you're probably not exporting anything.

[tenpoundbear]

Yes! That solved the issue for me.

I didn't realize this until now.

Its funny though that my other practice/test solutions worked, although admittedly I didn't have a function calling another function inside it like I do above.
Would anyone be able to clarify that little difference?

Another question, with this code that I am working on at the moment I noticed that some functions are exported with

extern "C"

whilst some are not...

Is there a reason for this?

extern "C" int far _declspec(dllexport) WeeksLate(int myear, char far *fdate, char far *tdate);
void far _declspec(dllexport) PrintItemTitle (HDC hdcPrn,int ypos,int lMarg,int rMarg,int cxPage,int year);

I also noticed some functions are exported like so

_declspec(dllexport) void func_2( int a )
and others like
void _declspec(dllexport) func_2( int a )

I am just wondering is there a difference in the order? I have tried compiling both ways without problems.

Thanks KBW for that answer!