Cats are finicky, so mftrs entice with a ton of flavor. My prob has always been keeping the dogs out of the litter box, because cat food tastes better than dog food even the 2nd time 'round. One thingyou do not want is your dog eating scoopable litter. It can form a solid block in the stomach, necessitating blockage surgery. Blockage can be lethal.
You'll need to keep the foods out of reach of each.
My cat will eat dog chow. It isn't as good for her as cat food. Each is designed for the animal needs.
Cat food is too rich for dogs,and you'll see digestive upsets often (read: runs).
When one of my dogs is on a hunger strike, I mix canned cat food in with his kibble to get him to eat.