Process Context

In generic thunking, the Win32-based DLL is run in the context of the process that loaded it, namely the 16-bit Windows-based application.

The GDI, dialog box, message box, and message functions work within 32-bit code loaded in the context of a 16-bit process. However, not all base features are supported in the context of a 16-bit process. In general, 32-bit code loaded by 16-bit processes can use the Win32 heap functions, memory-mapped file functions, file functions, and functions involving the current process and thread. You should avoid using third party Win32-based DLLs, unless you are sure they work safely in a 16 bit-environment.

Windows 95/98: There are a few additional limitations for Win32-based DLLs loaded by a 16-bit application:

• The DLL uses the stack reserved by the 16-bit application, which is much smaller than the 1MB default stack used by a Win32-based application (generally between 5 and 45K).
• The DLL cannot create new threads. Certain Win32 functions, such as those supporting the common dialog boxes or those supporting console applications, create threads on behalf of the calling application. Therefore, these functions cannot be used in a Win32-based DLL loaded by a 16-bit process.