Of course strl... functions are still braindamaged because they still return the length of the original string, regardless of what parameter you specified in the third argument. So if the initial string has lost its null terminator the strl... functions will still core dump even if you specified an otherwise safe size. Also, if you're copying the first few bytes out of an enormous buffer (especially a file mmap) it can take a long time for the function to chew through the rest of the buffer calculating that return value that you don't even care about.

That's why it's usually better to just use memcpy or memmove instead.