When should a C function return newly allocated memory?

Question

In a response elsewhere, I found the following snippet:

In general it is nicer in C to have the caller allocate memory, not the callee - hence why str

Answer 1

By allocating and deallocating memory in the same function (or source file), you'll have an easier time identifying potential memory leaks (or convincing yourself there are none) without having to hop around to different places in your program. If a callee allocates memory, it's ambiguous where the deallocation should take place. In contrast, by having the caller do it, that code is taking "full responsibility" for the memory.

Above all, though, consistency is the key. Pick one approach and stick with it.