Test Failure: System.IO.Tests.RandomAccess_NoBuffering.ReadWriteAsyncUsingMultipleBuffers #133278

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1. JulieLeeMSFT

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   on Sep 4, 2026
2. dotnet-policy-service

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   area-System.IO

   on Sep 4, 2026
4. dotnet-policy-service commented on Sep 4, 2026

   

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5. adamsitnik commented on Sep 7, 2026

   

   adamsitnik

   on Sep 7, 2026

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   System.NullReferenceException : Object reference not set to an instance of an object.
   Stack Trace:
   /_/src/libraries/System.Private.CoreLib/src/System/IO/RandomAccess.Windows.cs(673,0): at System.IO.RandomAccess.WriteGatherAtOffsetAsync(SafeFileHandle handle, IReadOnlyList`1 buffers, Int64 fileOffset, CancellationToken cancellationToken)

   The code:

   runtime/src/libraries/System.Private.CoreLib/src/System/IO/RandomAccess.Windows.cs

   Lines 671 to 675 in 58fee29

   	private static ValueTask WriteGatherAtOffsetAsync(SafeFileHandle handle, IReadOnlyList<ReadOnlyMemory<byte>> buffers, long fileOffset, CancellationToken cancellationToken)
   	{
   	if (!handle.IsAsync)
   	{
   	return AsyncOverSyncWithIoCancellation.InvokeAsync(static state => WriteGatherAtOffset(state.handle, state.buffers, state.fileOffset), (handle, buffers, fileOffset), cancellationToken);

   This particular line uses an argument passed to a public method that is ensured to not be null:

   runtime/src/libraries/System.Private.CoreLib/src/System/IO/RandomAccess.cs

   Lines 241 to 251 in 58fee29

   	public static ValueTask WriteAsync(SafeFileHandle handle, IReadOnlyList<ReadOnlyMemory<byte>> buffers, long fileOffset, CancellationToken cancellationToken = default)
   	{
   	ValidateInput(handle, fileOffset);
   	ValidateBuffers(buffers);
   	if (cancellationToken.IsCancellationRequested)
   	{
   	return ValueTask.FromCanceled(cancellationToken);
   	}
   	return WriteGatherAtOffsetAsync(handle, buffers, fileOffset, cancellationToken);

   runtime/src/libraries/System.Private.CoreLib/src/System/IO/RandomAccess.cs

   Lines 284 to 289 in 58fee29

   	private static void ValidateInput(SafeFileHandle handle, long fileOffset, bool allowUnseekableHandles = true)
   	{
   	if (handle is null)
   	{
   	ThrowHelper.ThrowArgumentNullException(ExceptionArgument.handle);
   	}

   Even the helper that is called (IsAsync) is using a state that can't be null:

   runtime/src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs

   Line 107 in 58fee29

   public bool IsAsync => (GetFileOptions() & FileOptions.Asynchronous) != 0;

   runtime/src/libraries/System.Private.CoreLib/src/Microsoft/Win32/SafeHandles/SafeFileHandle.Windows.cs

   Lines 278 to 328 in 58fee29

   	internal unsafe FileOptions GetFileOptions()
   	{
   	FileOptions fileOptions = _fileOptions;
   	if (fileOptions != UninitializedOptions)
   	{
   	return fileOptions;
   	}
   	Interop.NtDll.CreateOptions options;
   	int ntStatus = Interop.NtDll.NtQueryInformationFile(
   	FileHandle: this,
   	IoStatusBlock: out _,
   	FileInformation: &options,
   	Length: sizeof(uint),
   	FileInformationClass: Interop.NtDll.FileModeInformation);
   	if (ntStatus != Interop.StatusOptions.STATUS_SUCCESS)
   	{
   	int error = (int)Interop.NtDll.RtlNtStatusToDosError(ntStatus);
   	throw Win32Marshal.GetExceptionForWin32Error(error);
   	}
   	FileOptions result = FileOptions.None;
   	if ((options & (Interop.NtDll.CreateOptions.FILE_SYNCHRONOUS_IO_ALERT | Interop.NtDll.CreateOptions.FILE_SYNCHRONOUS_IO_NONALERT)) == 0)
   	{
   	result |= FileOptions.Asynchronous;
   	}
   	if ((options & Interop.NtDll.CreateOptions.FILE_WRITE_THROUGH) != 0)
   	{
   	result |= FileOptions.WriteThrough;
   	}
   	if ((options & Interop.NtDll.CreateOptions.FILE_RANDOM_ACCESS) != 0)
   	{
   	result |= FileOptions.RandomAccess;
   	}
   	if ((options & Interop.NtDll.CreateOptions.FILE_SEQUENTIAL_ONLY) != 0)
   	{
   	result |= FileOptions.SequentialScan;
   	}
   	if ((options & Interop.NtDll.CreateOptions.FILE_DELETE_ON_CLOSE) != 0)
   	{
   	result |= FileOptions.DeleteOnClose;
   	}
   	if ((options & Interop.NtDll.CreateOptions.FILE_NO_INTERMEDIATE_BUFFERING) != 0)
   	{
   	result |= FileStreamHelpers.NoBuffering;
   	}
   	return _fileOptions = result;
   	}

   Since the C# implementation was not changed for a very long time, I suspect it's some kind of a runtime bug, hence I change the area.
6. adamsitnik

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   on Sep 7, 2026
7. dotnet-policy-service commented on Sep 7, 2026

   

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8. jakobbotsch

   self-assigned this

   on Sep 7, 2026
9. jakobbotsch

   added a commit that references this issue on Sep 7, 2026

   JIT: Dispatch OSR resumptions in tail-await-only methods

   ...

   This issue will close once commit e3845ab is merged into the 'main' branch.

   e3845ab
10. JulieLeeMSFT

    added this to the 12.0.0 milestone on Sep 8, 2026
11. jakobbotsch

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    untriagedNew issue has not been triaged by the area ownerNew issue has not been triaged by the area owner

    on Sep 9, 2026
12. jakobbotsch

    closed this as completedin #133358on Sep 9, 2026
13. github-actions

    locked and limited conversation to collaborators on Oct 10, 2026