Support: unlock Windows API support, switch to Windows 10 RS1+ APIs

compnerd · mstorsjo · commit a48395f22730 · 2024-08-07T14:40:03.000+03:00
This addresses a small window of in-atomicity in the rename support for Windows. If the rename API is stressed sufficiently, it can run afoul of the small window of opportunity where the destination file will not exist. In Swift, this causes the `LockFileManager` to improperly handle file locking for module compilation resulting in spurious failures as the file file is failed to be read after writing due to multiple processes overwriting the file and exposing the window constantly to the scheduled process when building with `-num-threads` > for the Swift driver. The implementation of `llvm::sys::fs::rename` was changed in SVN r315079 (80e31f1) which even explicitly identifies the issue: ~~~ This implementation is still not fully POSIX. Specifically in the case where the destination file is open at the point when rename is called, there will be a short interval of time during which the destination file will not exist. It isn't clear whether it is possible to avoid this using the Windows API. ~~~ Special thanks to Ben Barham for the discussions and help with analyzing logging to track down this issue! This API was introduced with Windows 10 RS1, and although there are LTSC contracts that allow older versions to be supported still, the mainstream support system has declared this release to be obsoleted. As such, assuming that the OS is at least as new as this is reasonable.
diff --git a/llvm/include/llvm/Support/Windows/WindowsSupport.h b/llvm/include/llvm/Support/Windows/WindowsSupport.h
@@ -21,11 +21,18 @@
 #ifndef LLVM_SUPPORT_WINDOWSSUPPORT_H
 #define LLVM_SUPPORT_WINDOWSSUPPORT_H
 
+#if defined(__MINGW32__)
 // mingw-w64 tends to define it as 0x0502 in its headers.
 #undef _WIN32_WINNT
+#undef NTDDI_VERSION
+
+// Expose APIs from Windows 10 RS1. We only require Windows 7 at runtime,
+// so make sure that we only use such features optionally, with fallbacks
+// where relevant.
+#define _WIN32_WINNT 0x0A00
+#define NTDDI_VERSION 0x0A000002 // Expose APIs from WIN10_RS1
+#endif
 
-// Require at least Windows 7 API.
-#define _WIN32_WINNT 0x0601
 #define WIN32_LEAN_AND_MEAN
 #ifndef NOMINMAX
 #define NOMINMAX
diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
@@ -466,18 +466,39 @@ static std::error_code rename_internal(HANDLE FromHandle, const Twine &To,
                                   (ToWide.size() * sizeof(wchar_t)));
   FILE_RENAME_INFO &RenameInfo =
       *reinterpret_cast<FILE_RENAME_INFO *>(RenameInfoBuf.data());
-  RenameInfo.ReplaceIfExists = ReplaceIfExists;
+
+  RenameInfo.Flags = FILE_RENAME_FLAG_POSIX_SEMANTICS
+                   | (ReplaceIfExists ? FILE_RENAME_FLAG_REPLACE_IF_EXISTS : 0);
   RenameInfo.RootDirectory = 0;
   RenameInfo.FileNameLength = ToWide.size() * sizeof(wchar_t);
   std::copy(ToWide.begin(), ToWide.end(), &RenameInfo.FileName[0]);
 
   SetLastError(ERROR_SUCCESS);
-  if (!SetFileInformationByHandle(FromHandle, FileRenameInfo, &RenameInfo,
+  // FileRenameInfoEx requires Windows 10 RS1
+  if (!SetFileInformationByHandle(FromHandle, FileRenameInfoEx, &RenameInfo,
                                   RenameInfoBuf.size())) {
     unsigned Error = GetLastError();
     if (Error == ERROR_SUCCESS)
       Error = ERROR_CALL_NOT_IMPLEMENTED; // Wine doesn't always set error code.
-    return mapWindowsError(Error);
+    if (Error == ERROR_INVALID_PARAMETER || Error == ERROR_CALL_NOT_IMPLEMENTED) {
+      // If running on an older version of Windows, fall back on FileRenameInfo.
+      RenameInfo.ReplaceIfExists = ReplaceIfExists;
+      RenameInfo.RootDirectory = 0;
+      RenameInfo.FileNameLength = ToWide.size() * sizeof(wchar_t);
+      std::copy(ToWide.begin(), ToWide.end(), &RenameInfo.FileName[0]);
+
+      SetLastError(ERROR_SUCCESS);
+      if (!SetFileInformationByHandle(FromHandle, FileRenameInfo, &RenameInfo,
+                                      RenameInfoBuf.size())) {
+        unsigned Error = GetLastError();
+        if (Error == ERROR_SUCCESS)
+          Error = ERROR_CALL_NOT_IMPLEMENTED; // Wine doesn't always set error code.
+        return mapWindowsError(Error);
+      }
+    } else {
+      return mapWindowsError(Error);
+    }
+
   }
 
   return std::error_code();
