A proposal for ISO C++ to inspect and handle std::exception_ptr without throwing and catching.
You can see the rendered version here.
A note on licensing: All of my code in this repo is Apache2. However this library includes headers describing the platform ABI that is under its own license. The libstd++/libsupc++ code is under GPL. The MSCV header is cobbled together from various sources, so I don't know what license it is under.