A black comedy about cannibalism, Ravenous is a bit like The Thing plunked down in the Donner Pass. Starring Guy Pearce and Robert Carlyle, it opens with a closeup of bloody steaks at a victory feast and eventually moves on to bloody corpses. Set in 1847 in a remote military outpost (is there any other kind?) in California’s snowy Sierra Nevada mountains, it’s a not-so-Grand Guignol gross-out that posits the moral dilemma: Would you rather eat or be eaten? Make no mistake: In the movie business, where they devour their young, these questions are more than academic. The press book for Ravenous includes the recipes for numerous human taste treats and then, off to the side, in small letters, cautions: “All recipes are fictitious. Twentieth Century Fox does not condone cannibalism.” That’s reassuring. Don’t go to this movie on a full stomach. Better yet, don’t go.