Microsoft KB Archive/207132

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INFO: How Regsvr32.exe Registers and Unregisters COM DLLs

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Q207132

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The information in this article applies to:


 * Microsoft Windows 95
 * Microsoft Windows 98
 * Microsoft Windows NT Advanced Server, version 4.0
 * Microsoft Windows NT Server version 4.0
 * Microsoft Windows NT Workstation version 4.0
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Datacenter Server
 * Microsoft Windows 2000 Professional
 * Microsoft Windows 2000 Server

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SUMMARY
This article describes how the RegSvr32.exe program registers and unregisters a Component Object Model (COM) dynamic-link library (DLL). You can use this information to troubleshoot errors that occur when you try to use RegSvr32.exe program with your COM DLL.

MORE INFORMATION
RegSvr32.exe calls the following Win32 functions in this order:


 * OleInitialize
 * LoadLibrary to load the DLL
 * DllRegisterServer or DllUnregisterServer
 * FreeLibrary
 * OleUninitialize

Most often, RegSvr32.exe fails because the LoadLibrary, DllRegisterServer, or DllUnregisterServer function fails. LoadLibrary can fail if the DLL is not in the specified path, or if the specified path is incorrect. LoadLibrary can also fail if one of the dependencies of the DLL that you are trying to load is not met; in other words, if a dependent DLL is not present or is not in the specified path.

NOTE: You can use the Depends.exe tool to check whether or not all of the dependencies of your DLL are met. Depends.exe is included with the Microsoft Platform Software Development Kit (SDK), which ships with Microsoft Visual Studio.

Your DLL must implement DllRegisterServer and DllUnregisterServer, which contain the logic that is necessary to add or delete the required registry entries for the COM component. RegSvr32.exe finds the entry point to these functions, and calls them appropriately.

NOTE: If you use the Microsoft Active Template Library (ATL) Wizard to create the COM DLL, the Wizard generates the necessary code for DllRegisterServer and DllUnregisterServer.

If you use Microsoft Visual C++, refer to the Platform SDK sample at \Platform SDK\Samples\Com\Fundamentals\Async\Server.

Step-by-Step Example
The following sample describes registry functions that you can use to register and unregister your COM DLL.

You can also write your own code to do what RegSvr32.exe does. This helps to identify, isolate, and troubleshoot errors more easily.

To create a Win32 Application that you can use to register or unregister your COM DLL, perform the following steps:


 * 1) In Visual C++, create a new Win32 Application named Register. Accept all of the defaults.
 * 2) Create a new .cpp file named Register.cpp, and add it to the project.
 * 3) Paste the following code in Register.cpp:
 * 4) Build the application, and use it to register or unregister your COM DLL.