http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49973
--- Comment #6 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2011-08-04 14:38:16 UTC --- The GCS says "column numbers should start from 1 at the beginning of the line ... Calculate column numbers assuming that space and all ASCII printing characters have equal width, and assuming tab stops every 8 columns.". This doesn't say how other characters should be counted, although for the results of wcswidth seem appropriate.
