[llvm] Support: unlock Windows API support, switch to Windows 10 RS1+ APIs (PR #102240)

[Martin Storsjö via llvm-commits]

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@@ -466,21 +466,41 @@ 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.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);
+  static const struct {
+    DWORD dwFlag;
+    FILE_INFO_BY_HANDLE_CLASS Class;
+  } kRenameStyles[] = {
+    { FILE_RENAME_FLAG_POSIX_SEMANTICS, FileRenameInfoEx },
+    { 0, FileRenameInfo },
+  };
+
+  for (const auto &style : kRenameStyles) {
+    RenameInfo.Flags = style.dwFlag |
+                       (ReplaceIfExists ? FILE_RENAME_FLAG_REPLACE_IF_EXISTS
+                                        : 0);
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mstorsjo wrote:

This way of setting the flags, in what is a union in `FILE_RENAME_INFO` doesn't seem right for the old version; we should be setting `RenameInfo.ReplaceIfExists = ReplaceIfExists;` in that case. Writing to `Flags` which is aliased with `ReplaceIfExists` might work somehow, but we should be passing in the value `ReplaceIfExists` (and nothing else in that case) - and it doesn't feel entirely kosher to set a union field via another field. (I don't remember exactly, this may be a case which is ok in C but invalid in C++.)

https://github.com/llvm/llvm-project/pull/102240