Blerg. Spent two hours last night chasing bugs through "How did this code ever work" mode, and then discovered that the reason why I hadn't seen any bugs go away in the past two hours was because when I switched makefiles, I was now building the executable "gimp_ace" instead of "gimp-ace", and "gimp-ace" was the one I was testing.
I knew having a hyphenated executable name would get me into trouble one of these days.
On the up side, you can expect to see a shiny new preview thingamabob in gimp adaptive contrast enhancement before much longer.
Update: Hit a snag in getting that preview to work right. Sent out a distress call... and now I wait and hope for someone to deliver me a clue. In the meantime, I guess it's a good time to mow the lawn.