Looks like SML is using user-defined literals [0, 1] to effectively pre-process the string literal into state/event objects. Looks like the string itself is turned into a template parameter in the process and I believe those shouldn't show up in the compiled code (maybe unless there's some mangling-related thing going on?)

[0]: https://en.cppreference.com/w/cpp/language/user_literal.html

[1]: https://github.com/boost-ext/sml/blob/f232328b49adf708737bef...

Thanks, I didn't know that was a thing.