Hi,
yes, I'm pretty sure it does. When you look at the LibraryLink examples,
you see that LibraryLink uses UTF8 strings as well.
In the example code you find
char *instring = MArgument_getUTF8String(Args[0]);
char *substring = MArgument_getUTF8String(Args[1]);
mint i, n = strlen(instring);
mint slen = strlen(substring);
which doesn't uses the length but calls strlen instead. If the string is
not null-terminated, strlen would fail, because
how should it know whether the string is over if not by the final \0.
When MathLink and LibraryLink share the same Wolfram type (what they
hopefully do), you should be on the safe side.
Cheers
Patrick