[libcxx-commits] [libcxx] [libc++] Fixed get count threads multi-CPU system with NUMA architecture (#72267) (PR #72270)

[Alexandre Ganea via libcxx-commits]

================
@@ -81,9 +81,43 @@ thread::hardware_concurrency() noexcept
         return 0;
     return static_cast<unsigned>(result);
 #elif defined(_LIBCPP_WIN32API)
+  // This implementation supports both conventional single-cpu PC configurations
+  // and multi-cpu system on NUMA (Non-uniform_memory_access) architecture
+  DWORD length = 0;
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aganea wrote:

Why not move all this Win32-specific code in `libcxx/src/support/win32/thread_win32.cpp (see other comments)
Also move everything in a lambda that is executed only once with a local static, i.e
```
unsigned __libcpp_hardware_concurrency()
{
  static unsigned hardware_threads = []() { ... };
}
```

https://github.com/llvm/llvm-project/pull/72270