> Before writing to the buffer you should've ensured that it's big enough, and decided what to do if it's not, long before actually doing it. In other words, what happens if it's not big enough?

If you planned all this out, you're still making an assertion as to the length. The contract is "give me a string of this length" and if that's not enforced by the compiler, it ought to be enforced at runtime so that the error is detected and dealt with as soon as possible.

So maybe "safe string functions" should really be "fail fast string functions."