[libcxx-commits] [PATCH] D104987: Use GetSystemTimePreciseAsFileTime() if available

[Sizhe Zhao via Phabricator via libcxx-commits]

Prince213 created this revision.
Prince213 added a reviewer: compnerd.
Prince213 added a project: libc++.
Prince213 requested review of this revision.
Herald added a subscriber: libcxx-commits.
Herald added a reviewer: libc++.

We will try to use GetSystemTimePreciseAsFileTime if possible.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D104987

Files:
  libcxx/src/chrono.cpp


Index: libcxx/src/chrono.cpp
===================================================================
--- libcxx/src/chrono.cpp
+++ libcxx/src/chrono.cpp
@@ -74,11 +74,17 @@
   static _LIBCPP_CONSTEXPR const seconds nt_to_unix_epoch{11644473600};
 
   FILETIME ft;
-#if _WIN32_WINNT >= _WIN32_WINNT_WIN8 && WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
-  GetSystemTimePreciseAsFileTime(&ft);
-#else
-  GetSystemTimeAsFileTime(&ft);
-#endif
+  typedef void (*GetSysTime_t)(LPFILETIME);
+  static GetSysTime_t getSysTime_p;
+
+  GetSysTime_t getSysTime_f = getSysTime_p;
+  if (nullptr == getSysTime_f) {
+    getSysTime_f = (GetSysTime_t)GetProcAddress(GetModuleHandleA("kernel32.dll"), "GetSystemTimePreciseAsFileTime");
+    if (nullptr == getSysTime_f)
+      getSysTime_f = GetSystemTimeAsFileTime;
+    getSysTime_p = getSysTime_f;
+  }
+  getSysTime_f(&ft);
 
   filetime_duration d{(static_cast<__int64>(ft.dwHighDateTime) << 32) |
                        static_cast<__int64>(ft.dwLowDateTime)};


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