DLL unloading itself

Question

Is it possible for a function that is inside a DLL to unload the DLL? I need to do this so I can make sure the DLL is not in use, then write to the DLL's file.

Answer 1

I don't think it will work. Calling FreeLibrary with a handle from the outside (LoadLibrary would have been called from an area outside the DLL) as the code runs in a memory location that will not be valid anymore.

Even if this is possible, it smells like a bad design. Maybe you want to make some updater or alike. Explain a bit more what is the result you expect. Unloading a DLL from within itself is not the way to go.

Answer 2

If your asking if you can safely unload/unmap a DLL loaded in a process from code in the DLL itself, the answer is no - there isn't really a safe way to do this.

Think about it this way: Unloading a DLL is done by decrementing it's reference count using FreeLibrary(). The problem of course is that once the reference count of the DLL hits zero, the module is unmapped. Which means that the code in the DLL that called FreeLibrary() is gone.

Even if you could do this, you'd still need to ensure that there are no other threads executing any exported functions from the DLL.