How to fix an error with an RCPP Package on Windows old-rel


I am developing a small package that uses one small rcpp function to calculate a coordinate. The function is only a very few lines of code. The package builds fine on all systems, except on Solaris and Windows-oldrel.
The error occurs in my own testthat function, where I test my function against fixed values.
Since the function is a very simple mathematical function, I have no idea what part of that math could go wrong on Windows Oldrel or solaris. I have tried running tests on rhub, however without debugging into the code I really don't know what could be the problem.

Are there any changes between R 3.6 and R 4.0 that only matter on Windows and Solaris that could explain why a simple math function breaks?

Thanks for you time.
Btw. the package is

Is the break an error, or a numeric mismatch.
If the latter its probably an issue of precision I would guess.

Yeah, the numbers don't match up. However, it only uses integers so I don't think precision would be a problem. Would it? And if so, why only Windows oldrel and not Ubuntu oldrel or Mac oldrel?

What are the values ?

Thanks for the tip. Hmm. More detailed tests shows it only occurs on i386 architecture. So I guess I need to debug my cpp code on i386 32-Bit.