[kentonv]

Cap'n Proto supports MinGW as a target platform. (It has also supported Cygwin since very early on.) However, Cap'n Proto is a library, so it needs to support whatever compiler the users of that library are using, and for the vast majority of Windows developers that's MSVC.

[jcoffland]

Right, but you should be able to compile a library with either MinGW or clang from Linux that your users can use with MSVC.

[kentonv]

Not if it uses C++. MinGW uses the G++ ABI which is totally incompatible with the MSVC ABI.

(Also, a lot of the issues we face affect headers, which need to be compiled into the client projects.)

[jcoffland]

Since the code is so small and in C++ why not make it a header only library?