Question

I realize this is a very specific question, and not very helpful outside of this scenario, although I am sure it applies to other questions with the same problem. I have a function to recursively search through windows (and their child windows) to find specific ones, it works exactly as expected, however it causes “function doesn’t return a value on all paths” warning. This is the only warning in my entire program, and although it might be silly, I’m interested in knowing if there is a way to stop this error from occurring, but still allowing the function to work properly.

    Public Function FindQWidgetWindows() As Integer
    Dim hWndStart As Integer = 0
    Dim WindowText As String = "*"
    Dim Classname As String = "QWidget"
    Dim hwnd As Integer
    Dim sWindowText As String
    Dim sClassname As String
    Dim r As Integer
    Static level As Integer

    If level = 0 Then
        If hWndStart = 0 Then hWndStart = GetDesktopWindow()
    End If

    level = level + 1

    hwnd = GetWindow(hWndStart, GW_CHILD)

    Do Until hwnd = 0
        Call FindQWidgetWindows()

        'Get the window text and class name'
        sWindowText = Space$(255)
        r = GetWindowText(hwnd, sWindowText, 255)
        sWindowText = Microsoft.VisualBasic.Left(sWindowText, r)
        sClassname = Space$(255)
        r = GetClassName(hwnd, sClassname, 255)
        sClassname = Microsoft.VisualBasic.Left(sClassname, r)

        If (sWindowText Like WindowText) And (sClassname Like Classname) Then
            Dim aRECT As RECT
            Dim hwndInt As Int32 = hwnd
            GetWindowRect(hwndInt, aRECT)
            FindQWidgetWindows = hwnd

            'uncommenting the next line causes the routine to'
            'only return the first matching window.'
            'Exit Do'

        End If

        hwnd = GetWindow(hwnd, GW_HWNDNEXT)

    Loop

    level = level - 1
End Function

Answer 1

You rely on the fact, that VB automatically declares a return variable with the name of your function. This variable can be used as any other variable in your function. So it also can get a default initialization.

As already mentioned, you only assign a value in a very nested If statement.
You should simply initialize your variable outside and before of your Do-loop with something like

FindQWidgetWindows = Nothing