Initializing a DLL Using DLLMain Optional Entry Point (177917)
The information in this article applies to:
- Microsoft Windows NT Workstation 4.0
- Microsoft Windows NT Server 4.0
This article was previously published under Q177917 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.
| Modification Type: | Major | Last Reviewed: | 8/9/2001 |
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| Keywords: | kbAPI kbinfo kbnetwork kbRPC KB177917 |
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