C arrays “know” their size. (String literals do too.)
Worse, it's an easy way to get burned on the sizeof() function, especially if you at some point refactor the code and put that chunk in a function separate from the original declaration.
This is why C programmers get gunshy about relying on that information and instead just treat strings like pointers all of the time.
Good programmers do nothing of the sort.
If you're talking about the old stdlib.h calls, don't use them with blind pointers where the size isn't known. I'd say use the "n" versions but you don't even have to do that.
'C' gets easier when you do faux RAII and make "objects" with internal state, at least think about not using dynamic allocation for everything and think a little bit about what might make the API usable by the extremely lazy.