Pádraig Brady wrote:
> I've pushed the c_iscntrl patch since it's simplest
> and probably most appropriate patch for an existing release.

Yes, that makes sense for a quick patch. However, for the next release I think 
it'd be better to catch encoding errors and multibyte control characters, given 
the problems noted. I installed the attached further patch to try to do this. 
This fixes the problem that Bruno noted, along with two others; my earlier patch 
neglected the possibility that mbrtowc can return 0, and it incorrectly assumed 
wide control characters always have a single-byte representation.

Either way the original bug appears to be fix so I'm boldly closing the bug report.