cc65 generated programs with the default setup run with the I/O area enabled, which gives a usable memory range of $8000 - $FFF9. More ROM may need additional bankswitching code.
Special locations:
No conio support is currently available for the Supervision.
The C runtime stack is located at $1FFF and growing downwards.
The C heap is located at the end of the program and grows towards the C runtime stack.