EDIT2: Disregard. I have no idea what I'm doing. Awaiting your response.
EDIT: I fixed it by myself. I think I have misunderstood how the library should be compiled in, and had included the chaiscript stdlibrary and stl_extra cpp source files. Removing them solves the issue.
Old post here (my own fix commited)
Very minimal reproducable example: https://github.com/haikarainen/chaitest
If you're on linux, just clone and run ./build.sh. Otherwise its as easy as cmake.
Note: This repo contains my own convenience-patched version of chaiscript (a few very tiny changes, like using std::cout for printing to flush buffers immediately). It should however be no different in this context.