[bug #48452] termios flag OTILDE conflicts with TAB1

[Kalle Olavi Niemitalo]

URL:
  <http://savannah.gnu.org/bugs/?48452>

                 Summary: termios flag OTILDE conflicts with TAB1  
                 Project: The GNU Hurd
            Submitted by: kon
            Submitted on: Sat Jul  9 17:47:19 2016
                Category: Hurd Servers
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
         Reproducibility: Every Time
              Size (loc): None
         Planned Release: None
                  Effort: 0.00
Wiki-like text discussion box: 

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Details:

In the Hurd, term/term.h defines:

#define OTILDE (1 << 10)

This conflicts with <bits/termios.h>:

# define TAB1   (1 << 10)       /* TAB delay type 1.  */

So if I do "stty tab1", then the terminal converts each tilde (~) to
backslash-backtick (\`), even though that conversion has nothing to do with
tabs.

This conflict could be fixed by renumbering OTILDE, and then perhaps moving
its definition to termios.h like the comment in term/term.h says.  However, I
think it's better to remove OTILDE altogether, because:

* GNU/Linux, NetBSD, OpenBSD, and FreeBSD neither implement an  output mode
like this nor define an OTILDE macro.
* stty in coreutils does not have an option specifically for OTILDE.
* It's not documented in the glibc manual:
https://www.gnu.org/software/libc/manual/html_node/Output-Modes.html
* If the bash prompt contains a tilde (denoting the home directory) and it's
converted like this, then readline miscomputes the cursor position.
* The mode may have been useful for terminals that cannot display a tilde
(e.g. Hazeltine 1500), but it's unlikely that anyone is using such terminals
with the Hurd nowadays.





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