Customers running the latest Windows client and server operating systems from Microsoft can download an update designed to advance the backward compatibility feature of the two platforms. the Redmond company is offering the refresh in order to ensure that both Windows 7 and in Windows Server 2008 R2 play nice with older applications, designed for the OS that preceded the latest releases, namely Windows Vista.
“The backward compatibility feature in Windows 7 and in Windows Server 2008 R2 detects the manifest in a DLL and sets the dynamic context of a DLL to Windows 7 or to Windows Vista. This enables Windows 7 and Windows Server 2008 R2 to provide a Windows Vista context for applications that are designed for earlier versions of Windows,” Microsoft stated.
The update is designed to allow a dynamic-link library (DLL) belonging to apps tailored to older versions of Windows to run in what Microsoft refers to as a Vista context. Still, a few criteria must be met before such a scenario would get the green light. Specifically, this will only be possible is the “The DLL does not specify an RT_MANIFEST resource. [AND] the DLL calls an API that uses the dynamic compatibility context. For example, the DLL calls the GetOverlappedResults API,” the company explained.
At the same time, Microsoft informs that the DLL can still run in a Windows 7 context, and doing so unexpectedly. This can happen in the eventuality in which the DLL is not manifested correctly. For this to happen, Windows 7’s compatibility mechanism needs to erroneously infer that the DLL is compatible with the operating system, in the absence of an RT_MANIFEST resource.
“This issue occurs especially if all the other DLLs in an application are not manifested or if the other DLLs are manifested with Windows 7 compatible GUIDs. This causes the "faulty" DLL to run in Windows 7 compatible mode. This behavior causes the application that loads the DLL to stop responding. Therefore, customers cannot run an application in Windows 7 context if the application loads at least one DLL in those two conditions,” Microsoft added.
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