Hi,
Anton Lindqvist wrote on Sun, Jan 22, 2017 at 02:57:12PM +0100:
> I recently encountered a bug related to UTF-8 in ksh(1).
>
> While inserting the following sequence, part of my prompt gets mangled:
>
> a<backward-char>ö
>
> With PS1='ksh$ ' I expect the following output:
>
> ksh$ öa
>
> ... actual output:
>
> kshöaa
I cannot reproduce. It works for me on OpenBSD-current (amd64).
Which version of OpenBSD are you using?
> Examining the output buffer when the 'ö' character is inserted
> shows the following, piped through hexdump:
>
> 00000000 c3 61 08 |.a.|
> 00000003
>
> 0xc3 is the first byte of the 'ö' character and the trailing
> backspace (0x08) causes the cursor to move past the incomplete UTF-8
> sequence.
I don't understand what you are talking about here. In particular,
what is that "output buffer" you are talking about?
> The backspace is emitted by the following lines in function x_ins:
>
> $ sed -n 460,464p /usr/src/bin/ksh/emacs.c
> if (adj == x_adj_done) {
> /* no */
> for (cp = xlp; cp > xcp; )
> x_bs(*--cp);
> }
>
> A solution would be to only emit a backspace if cp[-1] is a UTF-8
> continuation byte and cp[-2] a UTF-8 start byte. This removes one of
> erroneous backspaces that eats the prompt.
>
> Examining the output buffer when the last byte (0xb6) of 'ö' is
> inserted:
>
> 00000000 08 c3 b6 61 08 |...a.|
>
> The leading erroneous backspace is caused by the following lines in
> function x_zots, introduced in r1.64:
>
> $ sed -n 687,691p bin/ksh/emacs.c
> if (str > xbuf && isu8cont(*str)) {
> while (str > xbuf && isu8cont(*str))
> str--;
> x_e_putc('\b');
> }
>
> I haven't found any viable solution to not emit the backspace if a
> character is prepended, as opposed of appended.
>
> Any ideas on how to solve this issue would be much appreciated.
I neither understand the problem nor any part of your analysis.
Sorry,
Ingo
