Changes to DllMain()

Writing correct DllMain() functions is difficult. MSDN describes a series of restrictions, but these are so often ignored that Microsoft had to relax these restrictions by adding IJW ("It Just Works") technology.

Briefly, the following are all disallowed within a DllMain():

Call into another DLL, except functions in kernel32.dll
Directly, or indirectly, call FreeLibrary, LoadLibrary, LoadLibraryEx
Perform synchronization between objects, using any of the Wait functions, such as WaitForSingleObject
Throw an exception

In C++, this also applies to global C++ objects, which are constructed just before DllMain(DLL_PROCESS_ATTACH) is called, and destroyed just after DllMain(DLL_PROCESS_DETACH) is called.

A majority of 3ds Max plug-ins violated one or more of these "rules", but worked properly because of IJW. With VS2005, we made the following changes:

DllMain() doesn't do anything anymore, except keep the DLL's HINSTANCE, and call DisableThreadLibraryCalls() if nothing special needs to be done during DLL_THREAD_ATTACH and DLL_THREAD_DETACH.
All the InitCommon* are now 'obsolete' -- calling them does nothing, and core.dll simply works for everyone
If a DLL still requires special initialization and cleanup, then it should do so in one of the two following functions:

__declspec( dllexport ) int LibInitialize(void);
__declspec( dllexport ) intLibShutdown(void);

These should be called only once each, but it is not strictly enforced; the functions must keep track of this. Changes will also have to be done in the module definition files (*.DEF) to take these two functions into account. See Changes to Module Definition Files (.DEF).