Thread: Dll Loading Twice?

Hi guys I'm experimenting with DLL's and loading them. I've got a simple program that loads a DLL, and I've created a DLL that calls a function that displays a MessageBox.

The problem is when I launch my loader program, the MessageBox is displayed twice... I'm only calling LoadLibrary() once, so how can it be displayed twice?!

Any help would be greatly appreciated.

Here's the loader:

Code:

#include <iostream>
#include <Windows.h>

int main() {
	HMODULE hDll = LoadLibrary("messageboxdll.dll");
	
	if (!hDll) {
		printf("Could not load DLL.\n");
		return 1;
	}

	CloseHandle(hDll);
}

Here's the DLL:

Code:

#include <windows.h>

__declspec (dllexport) void Alert(void);

void Alert(void) {
	MessageBox(NULL, "Successfully loaded!", "Loaded", MB_OK);
}

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) {
	Alert();
	return TRUE;
}

I'm using Visual Studio 08.

DllMain is called once when your application loads it, and once when it unloads it. Your DllMain should look more like this instead:

Code:

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) {
	if(fdwReason == DLL_PROCESS_ATTACH)
		Alert();
	return TRUE;
}

Originally Posted by bithub

DllMain is called once when your application loads it, and once when it unloads it. Your DllMain should look more like this instead:

Code:

BOOL WINAPI DllMain(HINSTANCE hinstDLL, DWORD fdwReason, LPVOID lpvReserved) {
	if(fdwReason == DLL_PROCESS_ATTACH)
		Alert();
	return TRUE;
}

Wow, no wonder it was displaying it twice :P Thanks a lot!