Visual C++ Libraries as Shared Side-by-Side Assemblies

In Visual C++ 2005, the ATL, MFC, Standard C++, and CRT libraries support the new deployment model available on Windows XP, Windows Server 2003, and Windows Vista. The DLLs corresponding to all Visual C++ libraries have been grouped into several shared side-by-side assemblies and are installed into the native assembly cache, also called the WinSxS folder, under the operating system root directory. Similarly, while building a C++ application using Visual C++ 2005, by default the compiler and the linker generate a manifest file that describes runtime dependencies of this application on Visual C++ libraries.

Visual C++ libraries cannot be used by a C/C++ application without a manifest binding the application to these libraries. If a C/C++ application that depends on a Visual C++ library does not use a manifest, then an attempt to load the Visual C++ library as a dependent DLL from the application-local folder will result in an error message indicating that this is an unsupported way of loading a Visual C++ library.

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On versions of Windows that do not support deployment of shared side-by-side assemblies, such as Windows 98 and Windows 2000 Server, the Visual C++ libraries are installed in the System32 folder and WinSxS folder under the operating system root directory. This setup enables running Visual C++ applications on these operating system versions because they do not support manifest-based binding of applications to dependent DLLs. On these operating systems, when an application is loaded, the corresponding manifest file is ignored and the operating systems searches for dependent DLLs using paths set in the current running environment. However, on upgrading the operating system to a version that support manifest-based binding, such as Windows XP, Windows Server 2003, or Windows Vista, applications built with manifests start using the DLLs installed in the WinSxS folder.

This change to the deployment model of Visual C++ libraries prevents the problem of version conflicts between DLLs that occur when you add updates or configurations to a machine, and will allow support of side-by-side installation of two different Visual C++ toolsets. It will also allow you to produce reliable, self-describing applications and components that will not conflict with existing components. For more information on the advantages of new deployment model, please see Concepts of Isolated Applications and Side-by-side Assemblies. To learn about how this may impact deployment of existing native C++ applications, please refer to Redistributing Visual C++ Files.

Visual C++ libraries have been packaged in several shared side-by-side assemblies with corresponding manifest files.

Assembly Name

DLLs included in the assembly

Visual C++ Library

Microsoft.VC90.ATL

atl90.dll

Active Template Library

Microsoft.VC90.CRT

msvcr90.dll

msvcp90.dll

msvcm90.dll

C Runtime Library, release DLLs

Microsoft.VC90.DebugCRT

msvcr90d.dll

msvcp90d.dll

msvcm90d.dll

C Runtime Library, debug DLLs

Microsoft.VC90.MFC

mfc90.dll

mfcm90.dll

mfc90u.dll

mfcm90u.dll

Microsoft Foundation Classes, release DLLs

Microsoft.VC90.DebugMFC

mfc90d.dll

mfcm90d.dll

mfc90ud.dll

mfcm90ud.dll

Microsoft Foundation Classes, debug DLLs

Microsoft.VC90.MFCLOC

mfc90chs.dll

mfc90deu.dll

mfc90esp.dll

mfc90ita.dll

mfc90kor.dll

mfc90cht.dll

mfc90enu.dll

mfc90fra.dll

mfc90jpn.dll

Microsoft Foundation Classes, localized resources

Microsoft.VC90.OpenMP

vcomp.dll

OpenMP Library, release DLLs

Microsoft.VC90.DebugOpenMP

Vcompd.dll

OpenMP Library, debug DLLs

When you build applications with Visual C++ 2008, you may need to redistribute Visual C++ libraries and deploy the corresponding DLLs to customers' desktops. For more information please see Deployment (C++).