ReadFileEx incorrectly takes a Span<byte>

[colejohnson66]

CsWin32 generates a ReadFileEx and WriteFileEx that take Span<byte>. The generated methods increment the reference count on the handle, pin the span, then invoke the native routines. For asynchronous I/O (which these are designed for), this is incorrect. When the native method returns, two issues occur:

1. Decrementing the reference count could inadvertently dispose the safe handle
2. Unpinning the span leaves a GC hold that the underlying I/O driver will be reading or writing against

Generated code

[SupportedOSPlatform("windows5.1.2600")]
internal static unsafe winmdroot.Foundation.BOOL ReadFileEx(SafeHandle hFile, Span<byte> lpBuffer, ref global::System.Threading.NativeOverlapped lpOverlapped, delegate *unmanaged[Stdcall]<uint,uint,global::System.Threading.NativeOverlapped*,void> lpCompletionRoutine)
{
    bool hFileAddRef = false;
    try
    {
        fixed (global::System.Threading.NativeOverlapped* lpOverlappedLocal = &lpOverlapped)
        {
            fixed (byte* lpBufferLocal = lpBuffer)
            {
                winmdroot.Foundation.HANDLE hFileLocal;
                if (hFile is object)
                {
                    hFile.DangerousAddRef(ref hFileAddRef);
                    hFileLocal = (winmdroot.Foundation.HANDLE)hFile.DangerousGetHandle();
                }
                else
                    throw new ArgumentNullException(nameof(hFile));
                winmdroot.Foundation.BOOL __result = PInvoke.ReadFileEx(hFileLocal, lpBufferLocal, (uint )lpBuffer.Length, lpOverlappedLocal, lpCompletionRoutine);
                return __result;
            }
        }
    }
    finally
    {
        if (hFileAddRef)
            hFile.DangerousRelease();
    }
}

Expected behavior

CsWin32 should at least not generate "nice" Span<byte> overloads for ReadFileEx and WriteFileEx.

If you want to go further, you could provide a Memory<byte> version that handles pinning, and a completion routine that wraps the users' to unpin it. This is what one has to do anyways to properly use these APIs.

Repro steps

NativeMethods.txt content:

ReadFileEx
WriteFileEx

Context

• CsWin32 version: 0.3.106
• Target Framework: net8.0
• LangVersion: Latest

[AArnott]

This sounds like a dupe (in area at least) of #1066.
But the two functions you mention wouldn't be included in the fix for that because they are missing an attribute in the metadata. I filed microsoft/win32metadata#1994 to track that.