Scary DLL Problem, DLLs crash?

So I been trying to code a bunch of DLL stuff, I've done it before, but for some reason this time it's not working. It crashes.

Now, bear in mind that to simplify the problem, I've created a simple application that will run one function. But even that crashes!

How is this possible? Is it a vista thing? I tried both CodeBlocks and DevCpp.

Main PROGRAM:

Code:

---

#include <iostream>
#include <windows.h>

typedef int (*DLLFUNCTION)(int);

HINSTANCE g_hDLLinst;

int main(){
    DLLFUNCTION Message = NULL;
    std::cout << "Running DLL" << std::endl;
    g_hDLLinst = LoadLibrary("test.dll");
    std::cout << "Library Loaded" << std::endl;
    if(g_hDLLinst != NULL){
      Message = (DLLFUNCTION)GetProcAddress(g_hDLLinst, "Message");
    }
    std::cout << "Message Loaded" << std::endl;
    int x = Message(5);
    if(x == 5){
      std::cout << "Message Worked" << std::endl;
    }
    FreeLibrary(g_hDLLinst);
    return 0;
}

---

DLL:
MAIN.H:

Code:

---

#ifndef __MAIN_H__
#define __MAIN_H__

#include <windows.h>

/*  To use this exported function of dll, include this header
 *  in your project.
 */

#define DLL_EXPORT __declspec(dllexport)


#ifdef __cplusplus
extern "C"
{
#endif

int DLL_EXPORT DLLMessage(int x);

#ifdef __cplusplus
}
#endif

#endif // __MAIN_H__

---

MAIN.CPP

Code:

---

#include "main.h"

// a sample exported function
int DLL_EXPORT DLLMessage(int x){
    MessageBox(0, "DLL Worked", "DLL Message", MB_OK | MB_ICONINFORMATION);
    return x;
}

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved){
    switch (fdwReason)
    {
        case DLL_PROCESS_ATTACH:
            // attach to process
            // return FALSE to fail DLL load
            break;

        case DLL_PROCESS_DETACH:
            // detach from process
            break;

        case DLL_THREAD_ATTACH:
            // attach to thread
            break;

        case DLL_THREAD_DETACH:
            // detach from thread
            break;
    }
    return TRUE; // succesful
}

---

I put both the dll and the exe into the same folder, and it does:
Running DLL
Library Loaded
Message Loaded
Crash.......

Is the return value from GetProcAddress NULL? (I'm assuming you imported DLLMessage as Message, but who knows.)

Yes it's null, but I don't know why, I didn't do anything weird.

That's because you misspelled "DLLMessage" as "Message".

Have you ever bothered to crawl through the code one line at a time using a debugger?

Did you think about checking the pointer for NULL before trying to call it?

Oh thank you tabstop, I didn't notice that.

"Message" should have been "DLLMessage"
I guess it's been a long night. I was hoping it was something else though, because my other DLL program has everything right and that doesn't work either. I might have to post that as well :O.

And Salem, even if I had known that it was NULL before, or with a debugger, I still wouldn't have seen that error.

Seen what error?

Code:

---

Message = (DLLFUNCTION)GetProcAddress(g_hDLLinst, "Message");
if ( Message == NULL ) {
  // DANGER!!! - CLIFF AHEAD
}
int x = Message(5); // Keep on truckin'

---

Elaborating on Salems suggestion, you should always check return values.

Code:

---

int
main( void )
{
        HMODULE
                dll = LoadLibrary( "test.dll" );
        if( dll != NULL )
        {
                DLLFUNCTION
                        function = ( DLLFUNCTION )GetProcAddress( dll, "Message" );
                if( function != NULL )
                {
                        int
                                x = function( 5 );
                        if( x == 5 )
                        {
                                cout << "Success." << endl;
                        }
                        else
                        {
                                cerr << "Unexpected result!" << endl;
                        }
                }
                else
                {
                        cerr << "GetProcAddress failed!" << endl;
                }
                FreeLibrary( dll );       
        }
        else
        {
                cerr << "LoadLibrary failed!" << endl;
        }
}

---