If the input is an empty array or is null, return an empty array.

You only return an empty array (list in Python) if that happens. When the list isn't empty and isn't null, you should return a list with the count of positives as first element and the sum of negatives as the second one. There is no incosistency. Print the input, those are different tests.

Agreed. The instructions are not consistent.

The ++ may not work as you expect in this example. Try rewriting it like the other one.

You can't / don't. The solution set-up has direction in the comments about using the provided pointers positivesCount, and negativesSum:

  // Please store the positives count in the memory, pointed to
  // by the positivesCount parameter.
  
  // Please store the negatives sum in the memory, pointed to
  // by the negativesSum parameter.

How can you return an array in C when the function is void?

You cannot modify any element of the array. You'll get an error if you try to.

C: basic tests throw warnings.

why is it "const unsigned *bits"? doesn't this mean that the pointer is pointing to a constant integer? what if the first element in the array is changed?
can someone explain me?