alt Hacker Newsstrncpy doesn’t handle overlapping buffers (undefined behavior). Better to use strncpy_s (if you can) as it is safer overall. See: https://en.cppreference.com/w/c/string/byte/strncpy.html.
As an aside, this is part of the reason why there are so many C successor languages: you can end up with undefined behavior if you don’t always carefully read the docs.
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Back when strncpy was written there was no undefined behaviour (as the compiler interprets it today). The result would depend on the implementation and might differ between invocations, but it was never the "this will not happen" footgun of today. The modern interpretation of undefined behaviour in C is a big blemish on the otherwise excellent standards committee, committed (hah) in the name of extremely dubious performance claims. If "undefined" meaning "left to the implementation" was good enough when CPU frequency was measured in MHz and nobody had more than one, surely it is good enough today too.
Also I'm not sure what you mean with C successor languages not having undefined behaviour, as both Rust and Zig inherit it wholesale from LLVM. At least last I checked that was the case, correct me if I am wrong. Go, Java and C# all have sane behaviour, but those are much higher level.
> strncpy doesn’t handle overlapping buffers (undefined behavior).
It would make little sense for strncpy to handle this case, since, as I pointed out above, it converts between different kinds of strings.