Initializing a DLL Using DLLMain Optional Entry Point

• Microsoft Windows NT Workstation version 4.0
• Microsoft Windows NT Server version 4.0

SUMMARY

In Win32, all dynamic link libraries (DLLs) may contain an optional entry- point function (usually called DllMain) that is called for both initialization and termination. This gives you an opportunity to allocate or release additional resources as needed. Windows calls the entry-point function in four situations: process attach, process detach, thread attach, and thread detach.

MORE INFORMATION

The DllEntryPoint function is an optional method of entry into a DLL. If the function is used, it is called by the system when processes and threads are initialized and terminated, or upon calls to the LoadLibrary and FreeLibrary functions.

The body of your DLL entry-point function should perform only simple initialization tasks, such as setting up thread local storage (TLS), creating synchronization objects, and opening files. You must not call LoadLibrary in the entry-point function, because you may create dependency loops in the DLL load order. This can result in a DLL being used before the system has carried out its initialization code.

Calling Windows functions other than TLS, synchronization, and file functions may result in problems that are difficult to diagnose. For example, calling User, Shell, COM, RPC, and Windows Sockets functions (or any functions that call these functions) can cause access violation errors, because their DLLs call LoadLibrary to load other system components.

Keywords : kbnetwork kbAPI kbRPC kbSDKPlatform nt32ap NTSrvWkst kbGrpNet
Version : WinNT:4.0
Platform : winnt
Issue type : kbinfo