I am trying to put a WINAPI WinMain in a dll

Question

I am making a dll file and at the same time trying to call this function automatically when my DLL is loaded. How can I do this? It is a Windows API main function that creates a window but I dont know how do it. My first idea is to put it into DllMain function but I am really sure if this will work and also what to fill in the variables "HINSTANCE hInstance, HINSTANCE hPrevInstance,LPSTR lpCmdLine, int nCmdShow"

Below is the function I am trying to call automatically when my dll is loaded and I expect it to open a Window. Thanks.

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance,LPSTR lpCmdLine, int nCmdShow);

Export a function from the DLL that the host can call – David Heffernan Aug 08 '14 at 07:15 — David Heffernan, Aug 08 '14 at 07:15

score 4 · Accepted Answer · answered Aug 08 '14 at 02:51

There are limitations on what you can do in a DllMain function:

Calling functions that require DLLs other than Kernel32.dll may result in problems that are difficult to diagnose. For example, calling User, Shell, and COM functions can cause access violation errors, because some functions load other system components.

That rules out creating a window directly from DllMain. What you can do, however, is launch a thread from your DllMain, and that thread can create a window.

I did it without thread and it froze my Application. After I added thread to it, everything works fine. Thanks — Programmer, Aug 10 '14 at 04:28

score 2 · Answer 2 · answered Aug 08 '14 at 02:26

DLLs do have a WinMain() function. DllMain() or DllEntryPoint() are what you are looking for. Windows itself calls them when the DLL is loaded and unloaded. You do not call them yourself, you implement them instead. As for creating a window, you call CreateWindow/Ex() and related functions.

I am trying to put a WINAPI WinMain in a dll

2 Answers2