Temporarily restore support for Win7 / Server 2008 R2

[StephanTLavavej]

🗺️ Overview

My ultrabosses have decided that dropping support for targeting Win7 / Server 2008 R2 in VS 2022 17.12 is too aggressive, so I'm being required to restore it. However, dropping support has been approved for the 18.0 Preview 1 release (whenever that will happen, and whatever its major version branding will be), so this restoration is temporary.

Windows 7 and Server 2008 R2 are insecure operating systems, which haven't been receiving security updates for many months. Targeting them is making the world a worse place.

📜 Commits

• Revert Drop support for Win7 / Server 2008 R2 #4742.
  • Resolve conflicts with Always use cmpxchg16b on x64 for atomic_ref<16 bytes> #4751:
  • In yvals_core.h, we dropped _STL_WIN32_WINNT_WIN7, then we dropped _STL_WIN32_WINNT_WINBLUE.
  • In atomic_wait.cpp, we dropped _ATOMIC_WAIT_ON_ADDRESS_STATICALLY_AVAILABLE machinery, then we dropped __std_atomic_compare_exchange_128_fallback.
• [cherry-pick] Cauterize usage of Win8 GetCurrentPackageId.
  • As previously explained:

    This is technically a bonus cleanup - instead of removing machinery dealing with the conditional absence of Win8 APIs, it's removing machinery dealing with the conditional presence of Win8 APIs.

  • We should preserve this improvement, because it doesn't affect Win7 targeting.
  • Conflict resolutions: We want to remove DEFINEFUNCTIONPOINTER/STOREFUNCTIONPOINTER for GetCurrentPackageId next to where the machinery for GetSystemTimePreciseAsFileTime has been re-added.
• Restore the system_clock comment change.
  • We don't need to mention the GetSystemTimeAsFileTime fallback for Win7 here.
• Restore the P1135R6_atomic_wait test changes.
  • This made it self-contained (instead of centralized in test_atomic_wait.hpp).
  • This also made it not bother to verify the API level. __std_atomic_set_api_level exists for test purposes only, and our dev/test machines are all modern.
• Rename P1135R6_atomic_wait_vista to P1135R6_atomic_wait_win7.
  • The directory name was confusing, since we've totally dropped Vista support.
• Fuse test_atomic_wait.hpp into P1135R6_atomic_wait_win7.
  • No changes other than dropping the duplicate banner and #pragma once.
  • Note divergence: <atomic>: ADL-proof implementation of atomic and atomic_ref #4221 (merged 2024-01-17, before we removed Win7 on 2024-06-24) added compile-only test coverage for incomplete types to P1135R6_atomic_wait only. There's no need to replicate that coverage.

Making P1135R6_atomic_wait and P1135R6_atomic_wait_win7 independent obviously duplicates test code, but will make final removal simpler (in 18.0p1).

⚠️ Note to self:

I will need to revert some of MSVC-PR-559637's internal changes, specifically "NON-GitHub: Link src/vctools/PDB binaries against synchronization.lib."

[MahmoudGSaleh]

LGTM. Thank you!

[jovibor]

A PR that was fraught with pain and sorrow😶‍🌫️...

[darkalexis1990]

Windows Server 2008 R2 is still supported ->Grandfathered[7] Premium Assurance security update support until January 13, 2026.[8][9]

August Updates ->
https://www.catalog.update.microsoft.com/Search.aspx?q=KB5041838