/// Pops the stack top and assigns the `system_ceiling` to the new stack top.
Pops the stack top and assigns the `system_ceiling` to the new stack top.
Pops the stack top and assigns the ` system_ceiling ` to the new stack top .
pub fn pop_stack(&mut self) -> Result<(), KernelError> {
        if self.top == 0 {
            return Err(KernelError::Empty);
        }
        self.top -= 1;
        self.system_ceiling = self.pi_stack[self.top];
        Ok(())
    }
pub fn pop_stack ( & mut self ) -> Result < ( ) , KernelError > { if self . top == 0 { return Err ( KernelError :: Empty ) ; } self . top -= 1 ; self . system_ceiling = self . pi_stack [ self . top ] ; Ok ( ( ) ) }
Pops the stack top and assigns the `system_ceiling` to the new stack top.
Pops the stack top and assigns the ` system_ceiling ` to the new stack top .
&mut self