Replace strncpy and strcpy altogether with calls to snprintf. It takes a fixed buffer size, terminates correctly with the null character, and safely does everything strncpy does and more. It's a POSIX standard, so it should be portable to most systems too.

And yes, maybe it'll impact performance. Worry about that _after_ you profile your code and have the numbers to show it -- I'd bet good money that 95% of developers will never need to worry about it.