MSVC STL dev here. We're doing something different this time around. VS 2015 RTM and Update 1/2/3 were binary-compatible (as usual) while adding lots of features to the compiler and STL (unusual). VS 2017 RTM and its Updates will continue to be binary-compatible while adding features, meaning that our DLLs are still vcruntime140.dll, msvcp140.dll, etc. The versions are admittedly a mess, so here's the magic decoder ring:

VS 2015: IDE version 14, DLL version 140, toolset version 140, compiler version 19.0 (the C++ compiler is older than the Visual part of Visual C++). VS 2017: IDE version 15, DLL version 140 (same!), toolset version 141, compiler version 19.1

We still recommend that you build everything with VS 2017 consistently, as this will give you the most performance and correctness. However, you can mix in object files, static libraries, and DLLs compiled with previous versions all the way back to 2015 RTM, and things will continue to work (although you won't necessarily activate fixes in the newer version).

For more info, read the comments on https://blogs.msdn.microsoft.com/vcblog/2016/08/24/c1417-fea... where I mentioned WCFB02.