Re: performance bug of `wc -m`

[Kaz Kylheku (Coreutils)]

On 2018-05-20 16:43, Bruno Haible wrote:
> Kaz Kylheku wrote in
> https://lists.gnu.org/archive/html/coreutils/2018-05/msg00036.html :
>
> > In what situation are there printable characters in the range [0, 
> > UCHAR_MAX) that
> > have a width > 1?
>
> That's the wrong question. The question is which characters in this 
> range
> have width > 1 or <= 0.
>
> The program below shows that the answer (on a glibc system) is:
> The character 0x00AD (= SOFT HYPHEN) is printable but has width == 0.

I tried printing this on several terminals; all actually render 
something that is one character position wide.

A program which calculates column positions on a terminal will be wrong 
if 0xAD
has been printed, and it relies on this bogus datum from glibc.