Sorry - no idea. I have never used XC8, and am not prioritising it as generally the PIC18 is not recommended for use with (any) pre-emptive RTOS.
Note that C18 generates code that is not reentrant, and I'm lead to believe (but have not verified) that XC18 is the same.
What if I disable pre-emption by:
Will it still work especially priority scheduling.
I don't need preemption