[PATCH] Cygwin: console: Change timing of set/unset xterm compatible mode.

[Corinna Vinschen]

On Feb 17 18:45, Takashi Yano wrote:
> On Mon, 17 Feb 2020 10:00:15 +0100
> Corinna Vinschen wrote:
> > On Feb 16 17:13, Takashi Yano wrote:
> > > - If two cygwin programs are executed simultaneousley with pipes
> > >   in cmd.exe, xterm compatible mode is accidentally disabled by
> > >   the process which ends first. After that, escape sequences are
> > >   not handled correctly in the other app. This is the problem 2
> > >   reported in https://cygwin.com/ml/cygwin/2020-02/msg00116.html.
> > >   This patch fixes the issue. This patch also fixes the problem 3.
> > >   For these issues, the timing of setting and unsetting xterm
> > >   compatible mode is changed. For read, xterm compatible mode is
> > >   enabled only within read() or select() functions. For write, it
> > >   is enabled every time write() is called, and restored on close().
> > 
> > Oh well, I was just going to release 3.1.3 :}
> > 
> > In terms of this patch, rather than to change the mode on every
> > invocation of read/write/select/close, wouldn't it make more sense to
> > count the number of mode switches in a shared per-console variable, i.e.
> > 
> > LONG shared_console_info::xterms_mode = 0;
> > 
> > on open:
> > 
> >   if (InterlockedIncrement (&xterm_mode) == 1)
> >     switch to xterm mode;
> > 
> > on close:
> > 
> >   if (InterlockedDecrement (&xterm_mode)) == 0)
> >     switch back to compat mode;
> > 
> > ?
> 
> Thanks for the advice. However this unfortunately does not work
> in bash->cmd->bash case.
> For cmd.exe, xterm mode should be disabled, however, the second
> bash need xterm mode enabled.
> 
> On Mon, 17 Feb 2020 10:28:19 +0100
> Corinna Vinschen wrote:
> > On second thought, also consider that switching the mode and
> > reading/writing is not atomic.  You'd either have to add locking, or you
> > may suffer the same problem on unfortunate task switching.
> 
> Hmm, it may be. Let me consider. It may need time, so please
> go ahead for 3.1.3.

Ok.  I just wonder if I should merge your patch into 3.1.3 as is for the
time being.  It's better than the old state, right?


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
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