All string manipulation code in C deals with trailing NULL bytes, so if you try doing something different, you may get issues when you try to link to other code. It's not a great system, but good C programmers should know the shortfalls.

As an example of the alternate approach, the Rust language uses (ptr, size) to represent all arrays (called slices) and strings internally. This seems like a much better method, allowing you to reference substrings without allocating a buffer, and perform out-of-bounds checking at runtime.