Microsoft fixes a misfired PopCnt block but Windows 11 24H2 requirements may be here to stay

In the last couple of weeks, the internet has been abuzz with a possible upcoming alteration to the Windows 11 24H2 system requirements, wherein Microsoft is seemingly looking to make PopCnt, an SSE 4.2-based instruction, mandatory in the next version of Windows 11, version 24H2. This meant older CPUs were failing to boot Canary build 25905, and bypasses, like the one where a single command trick is used also did not work.

While it was not known at that time, PopCnt was also seemingly the culprit behind broken Microsoft Store apps on Windows 10 such that old processors were not able to launch on those systems often leading to a "File System Error (-2147219196)."

A Microsoft engineer, Mahmoud G Saleh, who is the Principal Software Engineering Manager of MSVC (Microsoft Visual C++), later confirmed that the problem was related to a buggy Visual C++ Libraries (VCLibs) package. They wrote:

Hi, the Visual C++ team has identified the problem as a regression in the vclibs framework package that the Photos app and other apps depend on. The problem affects computers with older hardware (that do not support SSE 4.2 instructions). Microsoft is currently working on validating a solution and it's expected to rollout to affected customers soon.

The credit for raising the issue goes to Masahiro Takegami, who noticed the PopCnt-related bug on their Intel Core 2 Quad Q6600 back in November last year. The issue was seemingly introduced with Visual Studio update version 17.8.0.

The latest version of Visual Studio 2022, version 17.9.1, fixes this issue alongside a couple of other bugs. The full changelog is given below:

Summary of What's New in this Release of Visual Studio 2022 version 17.9.1

 

• Updated the 16.11 MSVC toolset to 16.11.34 (14.29.30154.0) for customers who use the 16.11 C++ toolset with VS 17.9.
• Fixed a bug where the libconcrt.lib used when static linking could contain an SSE 4.2 instruction that was illegal on older X64 systems.
• Added support for char8_t as a built-in type for C++20 with /clr.

While this should fix the VS Code issue as well as the apps not working issue on older processors, it seems unlikely that older chips will work on Windows 11 24H2. The setup file for the Windows 11 version has apparently started showing a "This PC's processor doesn't support a critical feature (PopCnt)" message when users try to install version 24H2 on such systems. The message suggests Microsoft may consciously be introducing this change.

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