Are the orcs of the D&D core canon cannibals, i.e. not above eating sentient humanoids?
As far as I can remember, Tolkien's orcs seem to have no qualms about doing so (thanks for the link, Flamma), though I'm not sure they would've eaten their own kind as well.
What's the official stance (if there's any) on the feeding habits of DnD's orcs?
I'd be most interested in v3.5's "core setting" or that of the upcoming Next's (and least interested in v4's anything :)), though a comprehensive but abridged history could be a nice plus.
Best Answer
Yes, orcs are continuously depicted as cannibals (or, if you prefer, anthropophagous) in D&D lore.
AD&D 1e
Monster Manual, p.76:
Basic D&D
Orcs of Thar: I couldn't find anything on cannibalism with a quick scan, but this is an inordinately goofy book anyway.
AD&D 2e
Monstrous Manual:
This is repeated without comment in PHBR10 The Complete Book of Humanoids. Sounds like they will eat people, but as a secondary recourse once the burgers and brats run out.
D&D 3/3.5e
No comments one way or another in the core books or Savage Species. There are parenthetical references to orcish cannibalism in non-canon sources, like this WotC blog article.
Pathfinder
Orcs of Golarion, p. 5:
D&D 4e
Monster Manual p. 205:
D&D 5e
However, neither entry on orcs for 5e (Monster Manual p. 244; Volo's Guide to Everything p. 82) makes them out to be cannibals, merely murderous.