There are several warnings with the latest (as of 2018.1.18) CPP runtime. This is the first runtime that I've tried, so I don't know if these warnings existed before. I'm using Visual Studio 2017, and compiling as x64.
This causes a problem, because if I were to introduce a warning on my own code (which is, otherwise, warning free), it would get lost in the warnings from Spine.
I think all the warnings are of these types:
skeletonbinary.cpp(907): warning C4267: 'argument': conversion from 'size_t' to 'int', possible loss of data
spine\ikconstrainttimeline.cpp(155): warning C4244: '=': conversion from 'int' to 'T', possible loss of data