Compile error using d3dcompiler_47.dll to compile a Pixel Shader file

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C#

VB

DirectX

I got a non working copy Shazzam Shader Editor, and there are some Dll imports to some legacy dll functions. So I thought I update it a bit using this instead:
https://msdn.microsoft.com/en-us/library/windows/desktop/hh446872(v=vs.85).aspx[^]

So I took the original code and modified it to fit the new function:

<Guid("8BA5FB08-5195-40e2-AC58-0D989C3A0102"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)> _
  Private Interface ID3DXBuffer
      <PreserveSig> _
      Function GetBufferPointer() As IntPtr
      <PreserveSig> _
      Function GetBufferSize() As Integer
  End Interface

  <PreserveSig> _
  <DllImport("d3dcompiler_47.dll", CharSet:=CharSet.Auto, CallingConvention:=CallingConvention.Cdecl)> _
  Private Shared Function D3DCompileFromFile(<MarshalAs(UnmanagedType.LPStr)> pFilename As String,
                                                        pDefines As IntPtr,
                                                        pInclude As IntPtr,
                                                        <MarshalAs(UnmanagedType.LPStr)> pEntrypoint As String,
                                                        <MarshalAs(UnmanagedType.LPStr)> pTarget As String,
                                                        flags1 As Integer,
                                                        flags2 As Integer,
                                                        ByRef ppCode As ID3DXBuffer,
                                                        ByRef ppErrorMsgs As ID3DXBuffer) As Integer
  End Function

  Public Sub Compile(ByVal File As HLSLFileHelperClass)
      Dim pFilename As String = File.GetSourceFileFullName
      Dim pDefines As IntPtr = IntPtr.Zero
      Dim pInclude As IntPtr = IntPtr.Zero

      Dim pEntrypoint As String = File.HLSLEntryPoint
      Dim pTarget As String = File.ShaderCompilerVersion.ToString

      Dim flags1 As Integer = 0
      Dim flags2 As Integer = 0
      Dim ppCode As ID3DXBuffer = Nothing
      Dim ppErrorMsgs As ID3DXBuffer = Nothing

      Dim CompileResult As Integer = 0

      CompileResult = D3DCompileFromFile(pFilename,
                                         pDefines,
                                         pInclude,
                                         pEntrypoint,
                                         pTarget,
                                         flags1,
                                         flags2,
                                         ppCode,
                                         ppErrorMsgs)

      If CompileResult <> 0 Then

          Dim errors As IntPtr = ppErrorMsgs.GetBufferPointer()

          Dim size As Integer = ppErrorMsgs.GetBufferSize()

          ErrorText = Marshal.PtrToStringAnsi(errors)
          IsCompiled = False
      Else
          ErrorText = ""
          IsCompiled = True
          Dim psPath = File.GetCompiledFileFullName
          Dim pCompiledPs As IntPtr = ppCode.GetBufferPointer()
          Dim compiledPsSize As Integer = ppCode.GetBufferSize()

          Dim compiledPs = New Byte(compiledPsSize - 1) {}
          Marshal.Copy(pCompiledPs, compiledPs, 0, compiledPs.Length)
          Using psFile = IO.File.Open(psPath, FileMode.Create, FileAccess.Write)
              psFile.Write(compiledPs, 0, compiledPs.Length)
          End Using
      End If

      If ppCode IsNot Nothing Then
          Marshal.ReleaseComObject(ppCode)
      End If
      ppCode = Nothing

      If ppErrorMsgs IsNot Nothing Then
          Marshal.ReleaseComObject(ppErrorMsgs)
      End If
      ppErrorMsgs = Nothing


  End Sub

However using this code I get the following error:

Additional information: A call to PInvoke function 'WpfAdventuresInPixelShader!WpfAdventuresInPixelShader.ShaderCompiler::D3DCompileFromFile' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature.

If there is a handler for this exception, the program may be safely continued.

If I change the attribute from this:

<DllImport("d3dcompiler_47.dll", CharSet:=CharSet.Auto, CallingConvention:=CallingConvention.Cdecl)>

to this:

<DllImport("d3dcompiler_47.dll", CharSet:=CharSet.Auto)>

I get a result from the compiler of Integer.MinValue -2.....

So what do I need to do to get this working?
(oh, there is nothing wrong with the files I want to compile, as I can do that with the fxc.exe without any problems)