Re: [ANNOUNCEMENT] Updated: dash-0.5.8-3

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Jan 28 14:44, Houder wrote:
> On Wed, 25 Jan 2017 16:14:00, Steven Penny wrote:
> > Obviously Bash is not the problem, nor readline as Dash doesnt use readline. So
> > it appears the issue this time is again with cygwin1.dll, or perhaps the Dash
> > package.
> 
> .. uhm, it appears to me that Windows is the issue here.
> 
> As those in the know do not feel inclined to respond, I will provide some
> guesses that are my own:
> 
>  - in terms of input buffer management, utf-8 encoded characters will not
>    be recognized in case of bash and dash ... (they are under Fedora)
>     - see the output of stty -a: iutf8 is not present (it is under Fedora)
>  - readline provides bash with input buffer management for utf-8 encoded
>    characters on Windows (that is why it 'works' in case of bash)
>  - bash has support for utf-8 encoded characters ...
>    (e.g. ls -l ? will include one-character filenames in case the name is
>     made up of only one multi-byte character)
>  - dash has no such support ... [1][2]
> 
> Consequently, dash is only partly useful, even more so on Windows (as it
> would require an additional "helper" on Windows in order to obtain proper
> line-editing). Helper? readline, libedit ...
> 
> However, I am only guessing ... (only Erik and Corinna can provide expert
> details here).

I'm not quite sure yet but apparently the problem is in the handling of
VERASE in the termios implementation.  In cooked mode it fills a char
buffer with what has been typed.  The code doesn't know if the bytes in
the buffer are UTF-8 chars or just random bytes.  So VERASE erases
exactly one byte, which means, in case of UTF-8 chars it only erases the
last byte of of a mulitbyte character.

It seems the Linux termios implementation is different in that it
still knows which bytes constitute a single keypress and thus knows
how much byte it has to erase.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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