VBA kernel32 InterlockedIncrement not available in 64 bit host, what should I do?

Question

I'm in the process of upgrading some code from 32 to 64 bit VBA. It uses the InterlockedIncrement function:

Private Declare PtrSafe Function InterlockedIncrement Lib "kernel32" (ByRef Addend As Long) As Long

This was formerly exported by kernel32 but only for x86 callers. Running from 64-bit Excel it's not so simple, I get a "Can't find DLL entry point InterlockedIncrement in kernel32" error - here's the reason I found:

On 64 bit windows these are not real functions [...] they are compiler intrinsics instead. The code that is P/Invoking that function should be using the Interlocked managed class

What's a good alternative/ can I fix this?

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For context, I'm updating the code from this answer on SO where InterlockedIncrement & InterlockedDecrement are used to do COM reference counting. Now I understand these Interlocked functions are atomic operations which is important for multithreading, however since VBA runs in a single threaded apartment do I even need to bother? Is this.refCount = this.refCount + 1 sufficient? The code is slightly above my head so I can't be 100% certain that I won't introduce a bug by forgetting about these functions but let me know either way.

Answer 1

Single threaded drop-in replacements

Private Function InterlockedIncrement(ByRef Addend As Long) As Long
    Addend = Addend + 1
    InterlockedIncrement = Addend
End Function

Private Function InterlockedDecrement(ByRef Addend As Long) As Long
    Addend = Addend - 1
    InterlockedDecrement = Addend
End Function