In the Voice, the Hobereview of the film breaks down the literalness and the compromises quite well, though his take is slightly more bemused, as evidenced by his ironic-caps references to The Man, The Boy, The Redneck Slaughterhouse of Terror, and Hillcoat's one significant revision of the manuscript:
...my favorite addition to the novel is the close-up of The Post-Apocalyptic Puppy of Hope that appears in the movie's final scene. It's a last-minute Christmas card reminiscent of the voiceover that opens Sam Fuller's Vietnam-set China Gate: "In this ravaged city where people are starving, all the dogs have been eaten except one."
Well, yes, on the one hand The Post-Apocalyptic Puppy of Hope is up there with last year's "Fucking Arty Blood Splotch." But on the other hand...
Because Hobes is writing a review and not a message-board post, he's not actually spending paragraph upon paragraph interpreting and also giving away the nuances of the ending. So I'm not sure how spot-on he means his China Gate reference to be, narratively speaking. But it is. (Spoilers to follow.)
Dig: by the end of the book, the Man has died and the Boy is alone but, to grant us some semblance of hope, McCarthy has the Boy fall in—almost immediately—with a new, intact nuclear family. Except that the boy has been prepared to kill himself before being murdered and eaten by others, and isn't sure that this family won't, you know, kill and eat him. Post-apocalypse and all that.
So in the last scene of The Road, we have to be convinced that a) the boy drops the gun and goes with them, and that b) he won't be killed and eaten shortly after the credits roll.
Part a) is easy enough to demonstrate. Part b) is a little trickier. But McCarthy didn't mean for his ending to be ambiguous, I don't think, and Hillcoat (and Harvey Weinstein, who tinkered with the movie for over a year) didn't either.
And that's why the China Gate quote, aside from sorta hilariously pointing out the sappiness of the scene, accurately summarizes the dog's efficiency and clarity as a storytelling choice.
Walking out of The Road, we don't think, "I wonder if the kid is really ok," we think "phew he's ok, or as ok as he can be expected to be (post-apocalypse and all that)." This is because, well, the Boy's new Family has a dog. If after ten years of post-apocalyptic scavenging they haven't eaten their dog, they're not going to eat a kid.
So as goofily corny and uplifting as The Post-Apocalyptic Puppy of Hope is, it actually serves, quite admirably, as a way of dissolving ambiguity over the end of the film.
In conclusion: sorry, Jonny, for bigfooting you on the End Times and Puppy beats. Slow news day.