The C++ std::string is both very complicated mechanically and underspecified, which is why Raymond Chen's article about std::string has to explain three different types (one for each of the three popular C++ stdlib implementations) and still got some details wrong resulting in a cycle of corrections.

So that wouldn't really fit C very well and I'd suggest that Rust's String, which is essentially just Vec<u8> plus a promise that this is a UTF-8 encoded string, is closer.