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

[Thomas Wolff <towo at towo dot net>]

Am 14.02.2017 um 20:56 schrieb Eric Blake:
> On 02/14/2017 01:40 PM, Thomas Wolff wrote:
> > > No.  We're talking about a function in the master side of the tty, while
> > > the applications started in the terminal are on the slave side.
> > I am not familiar with the concept of setting termios properties on
> > either the master or slave side of a pty. I've only ever set them in the
> > client application, including my tests about IUTF8 which worked. Would
> > setting on the master side imply it's set for the clients implicitly,
> > and can it be changed later, e.g. when mintty character encoding is
> > being changed from the Options dialog?
> > And you say the function of erasing characters on BS is in the master
> > side? To be honest, this confuses me. I thought it's a client function,
> > like readline() would perform if used (apparently not by dash), which is
> > kind of an enhanced version of the tty cooked mode and used to work even
> > without the new flag, right?
> The readline source code does not mention IUTF8; and neither bash nor
> dash need to reference it, because if the tty handling code sets it
> correctly for what the terminal is going to display, then the clients
> that are read()ing from the tty never even see BS in cooked mode (the
> master side of the terminal handles BS before the read() completes in
> the slave, if I'm understanding it correctly).
This does not comply with my (limited) understanding of pty stuff. In 
mintty, forkpty will create a master/slave pty; mintty feeds it on the 
master side, while the client program (usually a shell) reads from the 
slave side. Mintty never handles BS for input, it simply feeds it into 
the pty. "Line disciplines" like cooked mode must be handled on the 
slave side.

> > > iutf8 is set in Linux by default and by most terminal applications ionly
> > > reset if the LC_CTYPE setting in the environment of the terminal
> > > application is not set to the utf8 codeset.  This is determined at
> > > terminal startup, not by the inferior processes runnin in the terminal.
> > > The applications still can set iutf8 via termios control (or stty(1)).
> > Will you patch stty as well to address the new flag?
> Already patched; coreutils-8.26-2 was promoted to current yesterday.
>
> > > For mintty I just thought it might be helpful to honor the character set
> > > setting in its options and to default to iutf8 if it's not set.
> > Sure, but it would be better to find a solution that implicitly works in
> > all terminals. Isn't it possible to handle this in forkpty()/openpty()?
> Does forkpty()/openpty() currently pay attention to environment
> variables to even know what encoding is currently in use?
Don't know, but maybe it simply should for this purpose, for a 
widely-useful solution.

>    And what's to
> say that the environment used to fork the master side will match the
> locale settings of the slave process that connects to the pty, so how do
> we know whether to default IUTF8 on or off based solely on the slave's
> environment, when it is the master that is handling BS and therefore the
> master's character encoding that matters for how much BS should erase ?
See above; the master isn't handling BS. But there should be no such 
inconsistency in the case of mintty because master and slave are forked 
from common initial code. I think this consideration is only relevant 
for reattaching programs like screen.
------
Thomas

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