Then (in my opinion) the library shouldn't advertise itself as compatible with Null terminated C strings, as users will assume that means they can use strlen (o

Then (in my opinion) the library shouldn't advertise itself as compatible with Null terminated C strings, as users will assume that means they can use strlen (or more likely, other functions which use strlen themselves). In a similar system I work on, we have a list of functions (like strlen, Strcat), where we carefully vet every occurrence in the code base. It's annoying but the only way to stop subtle bugs we've found.