I admit to not understanding the code involved, but I *thought* that the
problem involved cases where there *is* a preferred encoding in the
environment but it is not one of those covered by:
    case kCFStringEncodingMacRoman: return "mac-roman";
    case kCFStringEncodingMacGreek: return "mac-greek";
    case kCFStringEncodingMacCyrillic: return "mac-cyrillic";
    case kCFStringEncodingMacTurkish: return "mac-turkish";
    case kCFStringEncodingMacIcelandic: return "mac-icelandic";
The work around basically ensures the preferred encoding given by the
environment is one of those listed so that the rest of that part of the
code doesn't run. I don't think that my crash, at least, resulted from
no preferred encoding being defined in the environment but maybe
something is going wrong in the locale module because it is not one from
the standard list.

Maybe?