C++ names decoration is a problem. no_mangle refers to Rust (i.e. it's useful for calling Rust code from other languages). Rust has no control over C++ names mangling.
MSVC: probably not; Clang's MSVC ABI support is coming along well, but last time I checked there was no COFF support in the JIT. GCC on Itanium ABI platforms should be fine, although mixing C++ stdlib versions would be risky (primarily an issue on OS X).
Calling into C++ is generally a big problem in any programming language though, and for most, you have to write a C wrapper.