strncpy documentation question

Question

At the following regarding strncpy: http://www.cplusplus.com/reference/clibrary/cstring/strncpy/, it mentions the following:

No null-char

Answer 1

The semantics of strncpy(), even when precisely explained as they are in the C++ reference above, are widely misunderstood. The behavior of this function is counterintuitive and error prone.

To avoid problems when using it or further down the development process, when the maintainer will misread the code and add more subtile bugs, there is a simple solution: NEVER EVER USE THIS FUNCTION.

You can read further details about this in this article by Bruce Dawson.

To answer your question: if the source string is longer than the size passed as a third argument (usually corresponding to the size of the destination buffer), the function will copy size characters to the destination and no null byte will be present among these. Calling strlen(destination); will then invoke undefined behavior because it will attempt to read beyond the end of the array until it finds a null terminator. This specific behavior is what makes strncpy so error prone.