DLL Function / Load Library Problem

I'm having a bit of a problem calling a function in a DLL I created. Now it works fine when I call a function which returns void and has no arguments, but when I try to call this function (the following is from the DLL):

Code:

---

extern "C" _declspec (dllexport) int AddNums (int a, int b)
{
        return (a + b);
}

---

I get this runtime error:

Quote:

---

Run-Time Check Failure #0 - The value of ESP was not properly saved across a function call. This is usually the result of calling a function delcared with one calling convention with a function pointer declared witha a different calling convention.

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I can understand what's it's saying, but at the same time I can't because the function pointer... well, see for yourself. Here's the program trying to call the function:

Code:

---

#include "stdafx.h"

typedef void (WINAPI* DLL_NumberList) ();
typedef int  (WINAPI* DLL_AddNums) (int, int);

DLL_NumberList  NumberList;
DLL_AddNums    AddNums;


int main(int argc, char **argv[])
{
        HINSTANCE      hLib = LoadLibrary ("DLLProj.dll");
        char            cModName[_MAX_PATH];
        int            iAns = 0;

        if (hLib == NULL)
        {
                std::cerr << "Unable to load library!" << std::endl;
                getchar ();
                return 1;
        }
       
        memset (cModName, '\0', _MAX_PATH);
        GetModuleFileName ((HMODULE) hLib, (LPSTR) cModName, _MAX_PATH);
        std::cout << "Library Loaded: " << cModName << std::endl;

        NumberList = (DLL_NumberList) GetProcAddress ((HMODULE) hLib, "NumberList");
        AddNums = (DLL_AddNums) GetProcAddress ((HMODULE) hLib, "AddNums");

        if (NumberList == NULL)
        {
                std::cerr << "Unable to load function NumberList!" << std::endl;
                FreeLibrary ((HMODULE) hLib);
                getchar ();
                return 1;
        }

        if (AddNums == NULL)
        {
                std::cerr << "Unable to load function AddNums!" << std::endl;
                FreeLibrary ((HMODULE) hLib);
                getchar ();
                return 1;
        }

        NumberList ();
        iAns = AddNums (10, 10);
        std::cout << "Answer: " << iAns << std::endl;

        FreeLibrary ((HMODULE) hLib);
        return 0;
}

---

Now NumberList is loaded / called fine, I just get that runtime error when I try to call AddNums ("iAns = AddNums (10,10);").

UPDATE: Ah strange: When I get the error dialog, if I press Ignore the answer still appears (correctly) in the console (Answer: 20), but the same ESP error persists.

Try to declare function with standard calling convention, like
extern "C" _declspec (dllexport) WINAPI int AddNums (int a, int b)

Hmm I got the following error:

Quote:

---

error C2144: syntax error : 'int' should be preceded by ';'

---

When I added the WINAPI; here it is now:

Code:

---

extern "C" _declspec (dllexport) WINAPI int AddNums (int a, int b)
{
        return (a + b);
}

---

Ah I forgot to include windows.h in the dll project, but now I get some warnings:

Quote:

---

c:\Documents and Settings\lee\Desktop\DLLProj\DLLProj.cpp(14) : warning C4518: 'int ' : storage-class or type specifier(s) unexpected here; ignored
c:\Documents and Settings\lee\Desktop\DLLProj\DLLProj.cpp(14) : warning C4230: anachronism used : modifiers/qualifiers interspersed; qualifier ignored

---

Should they present a problem?

UPDATE: Yes, yes they ........ing do. Now it can't load the function. Here's the updated code:

Code:

---

// DLLProj.cpp
extern "C" _declspec (dllexport) int WINAPI AddNums (int a, int b)
{
        return (a + b);
}

// Program trying to load function
#include "stdafx.h"

typedef void (WINAPI *DLL_NumberList) ();
typedef int  (WINAPI *DLL_AddNums) (int, int);

DLL_NumberList  NumberList;
DLL_AddNums    AddNums;


int main(int argc, char **argv[])
{
        HINSTANCE      hLib = LoadLibrary ("DLLProj.dll");
        char            cModName[_MAX_PATH];
        int            iAns = 0;

        if (hLib == NULL)
        {
                std::cerr << "Unable to load library!" << std::endl;
                getchar ();
                return 1;
        }
       
        memset (cModName, '\0', _MAX_PATH);
        GetModuleFileName ((HMODULE) hLib, (LPSTR) cModName, _MAX_PATH);
        std::cout << "Library Loaded: " << cModName << std::endl;

        NumberList = (DLL_NumberList) GetProcAddress ((HMODULE) hLib, "NumberList");
        AddNums = (DLL_AddNums) GetProcAddress ((HMODULE) hLib, "AddNums");

        if (NumberList == NULL)
        {
                std::cerr << "Unable to load function NumberList!" << std::endl;
                FreeLibrary ((HMODULE) hLib);
                getchar ();
                return 1;
        }

        if (AddNums == NULL)
        {
                std::cerr << "Unable to load function AddNums!" << std::endl;
                FreeLibrary ((HMODULE) hLib);
                getchar ();
                return 1;
        }

        NumberList ();
        iAns = AddNums (10, 10);
        std::cout << "Answer: " << iAns << std::endl;

        FreeLibrary ((HMODULE) hLib);
        return 0;
}

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This is starting to really annoy me now. Each time I change something it either makes no difference or the function can't be loaded. :mad:

Solved it. Removed WINAPI from the function pointer declaration and it all works fine (I also removed WINAPI from the DLL function declaration).

Change:

Code:

---

extern "C" _declspec (dllexport) int WINAPI AddNums (int a, int b)
{
        return (a + b);
}

---

to:

Code:

---

// DLLProj.cpp
extern "C" _declspec (dllexport)int AddNums (int a, int b)
{
        return (a+b);
}

---

Get rid of the WINAPI