Use one single DLL library to import other libraries at runtime

Question

I am writing a Win32 DLL library that can be redistributed. I am using different versions of the windows API because I want to support Windows 7 functions, but still have support for Windows 2000 (with some function disabled). What I have currently is MyLib2000.dll, MyLibXP.dll, and MyLibVista.dll, and my application chooses which library to load at runtime. I want a way to have a single DLL (MyLib.dll) that stores the other three in itself and when it's being loaded, it extracts the correct DLL out of itself and loads it.

I know this is not the best way to do this, so suggestions on another method of doing this is welcome.

Answer 1

Why not just abstract out the OS-version dependencies in a software layer, implemented in terms of something like STLSoft's dl_call() function template suite.

Answer 2

Use delayloading and implement the dliNotePreLoadLibrary notification hook to load the correct version of your DLL. The linker-provided delay load logic will then pull in all the functions from whichever DLL you loaded.

http://msdn.microsoft.com/en-us/library/z9h1h6ty(v=VS.100).aspx

Or use delay-loading and implement your functions to check the OS version before calling any function that could fail to be loaded (since it doesn't exist on the old OS).