How can I automatically load DLLs from a subdirectory?

Question

In Visual Studio, you create a .dll project and it creates a .dll and .lib files. You link statically to the .lib, and if the .dll is in the same folder as the .exe, everything works.

I suspect that everything would also work if the .dll was in System32 or any other PATH folder (confirm or correct, please).

But here's the question: I want my exe to find the .dll in ./DLLS/ folder, that is, if my exe is in ....../MyApp/MyApp.exe then it should look for the .dll in ...../MyApp/DLLS/MyDll.dll. I DO NOT want to include the DLLS folder in path. Is there any way I can do this?

Please note that I do not wish to use LoadLibrary explicitly, so I can't specify the path there.

Thanks in advance for any help.

Answer 1

You could use SetDllDirectory for this. The loader will use the additional directory you specify when loading libraries. There can only be one additional directory, however, so you need to make sure that there aren't other calls to this at a later point in your application, otherwise the directory you specify will be ignored.

If that API does not allow relative directories (I'm not sure), you could always call GetModuleFileName with a NULL first parameter to get the file name of the currently executing program. With a little string manipulation, you can get the absolute path to your DLLs folder.

Answer 2

Here is the default sequence which Win32 applications go through when looking for a DLL:

http://msdn.microsoft.com/en-us/library/7d83bc18(VS.80).aspx

So according to this, another approach might be to call SetCurrentDirectory or SetDllDirectory. But in order for this to work you have to use the Delay Loaded Library functionality (you specify that in Project Settings in Visual Studio). Delay loaded library means that the DLL is loaded only at the moment when the program needs it, not automatically at the programs' startup.