Integer Vs Long Confusion

Question

I have seen many believe in the following

VBA converts all integer values to type Long

In fact, even the MSDN article says

Answer 1

“In recent versions, however, VBA converts all integer values to type Long, even if they're declared as type Integer.”

I don't believe that documentation. Consider the following simple example (run in Excel 2010):

Sub checkIntegerVsLong()
    
    'Check the total memory allocation for an array
    Dim bits As Integer 'or long? :)
    Dim arrInteger() As Integer
    ReDim arrInteger(1 To 5)
    arrInteger(1) = 12
    arrInteger(2) = 456
    'get total memory allocation for integer in array
    bits = VarPtr(arrInteger(2)) - VarPtr(arrInteger(1))
    Debug.Print "For integer: " & bits & " bits and " & bits * 8 & " bytes."


    Dim arrLong() As Long
    ReDim arrLong(1 To 5)
    arrLong(1) = 12
    arrLong(2) = 456
    
    'get memory allocation for long
    bits = VarPtr(arrLong(2)) - VarPtr(arrLong(1))
    Debug.Print "For long: " & bits & " bits and " & bits * 8 & " bytes."

End Sub

This prints:

For integer: 2 bits and 16 bytes.

For long: 4 bits and 32 bytes.

You can also test this on individual variables using the following:

Sub testIndividualValues()
    
    Dim j As Long
    Dim i As Integer
    Dim bits As Integer
    
    bits = LenB(i)
    Debug.Print "Length of integer: " & bits & " bits and " & bits * 8 & " bytes."
    bits = LenB(j)
    Debug.Print "Length of long: " & bits & " bits and " & bits * 8 & " bytes."

    
    
End Sub

which prints

Length of integer: 2 bits and 16 bytes.

Length of long: 4 bits and 32 bytes.

Last, you can use a type comparison here:

Public Type myIntegerType
    a As Integer
    b As Integer
End Type
Public Type myLongType
    a As Long
    b As Long
End Type

Public Sub testWithTypes()
    Dim testInt As myIntegerType
    Dim testLong As myLongType
    Dim bits As Integer
    
    bits = VarPtr(testInt.b) - VarPtr(testInt.a)
    Debug.Print "For integer in types: " & bits & " bits and " & bits * 8 & " bytes."
    
    bits = VarPtr(testLong.b) - VarPtr(testLong.a)
    Debug.Print "For long in types: " & bits & " bits and " & bits * 8 & " bytes."
    
End Sub

which also prints:

For integer in types: 2 bits and 16 bytes.

For long in types: 4 bits and 32 bytes.

This is pretty compelling evidence to me that VBA actually does treat Integer and Long differently.

If VBA silently converted behind the scenes, you would expect those to return the same number of bits/bytes for each of the pointer allocations locations. But in the first case, with Integer, it is only allocating 16 bits, while for Long variables, it allocates 32 bits.

So what?

So to your question of

If VBA converts all Integer values to type Long even if they're declared as type Integer, then the above should never give you the Overflow error!

It makes complete sense that you would get an Overflow error, as VBA has not actually allocated the memory for a Long to the Integer declaration.

I would be curious too if this returns the same on all versions of Office. I can only test on Office 2010 on 64 bit Windows 7.