Heap 4C in extended memory; use bug

As I read the code, the part of heap4c would overwrite the definition that I’d add in my code (elsewhere), or conflict with it, since the ucHeap apparently needs to be defined in heap4c. Note that their code is an either/or definition depending on whether or not the memory definition is user supplied or not. Since I don’t see a weak attribute, I don’t think the compiler would override that definition with my own.

Have I missed something?

How would you suggest this change be made?