Re: lib/48957 libedit/readline.c prompt bug

["Simon J. Gerraty" <sjg%juniper.net@localhost>]

The following reply was made to PR lib/48957; it has been noted by GNATS.

From: "Simon J. Gerraty" <sjg%juniper.net@localhost>
To: <christos%netbsd.org@localhost>, <fgsch%lodoss.net@localhost>, <gnats-bugs%netbsd.org@localhost>,
        <sjg%juniper.net@localhost>
Cc: 
Subject: Re: lib/48957 libedit/readline.c prompt bug
Date: Thu, 7 Dec 2017 17:49:12 -0800

 Simon J. Gerraty <sjg%juniper.net@localhost> wrote:
 > If I tweak that to stop doing the
 > write "\r                  \r" dance,
 > (which is hiding the extra prompt output)
 > we see that the bug is there:
 > 
 > prompt> hi
 > prompt> prompt> there
 > prompt> prompt> oops
 > prompt> prompt>
 > 
 > as I said, I'm not certain what the best fix is, but
 > calling el_set(e, EL_UNBUFFERED, 1) here does not appear to be correct.
 
 With the patch below, python works correctly:
 
 Python 2.7.8 (default, Dec  6 2017, 13:52:53)
 [GCC 4.2.1 Compatible Juniper Clang 3.7.1
 (git%psd-tools-git01.juniper.net@localhost:tool on junos
 Type "help", "copyright", "credits" or "license" for more information.
 
 >>> print 'hi'
 hi
 >>> ^D
 
 and fgsch's test app appears to behave as well as it might (without the
 write dance hiding anything) and initializing rl_already_prompted=0
 which makes more sense since the app isn't issuing the prompt itself:
 
 prompt> hi
 prompt> hi there
 prompt>  there
 prompt>  there
 prompt>
 prompt> one
 
 
 
 Index: lib/libedit/readline.c
 ===================================================================
 RCS file: /cvsroot/src/lib/libedit/readline.c,v
 retrieving revision 1.144
 diff -u -p -r1.144 readline.c
 --- lib/libedit/readline.c	17 Sep 2017 08:10:08 -0000	1.144
 +++ lib/libedit/readline.c	8 Dec 2017 01:39:24 -0000
 @@ -2079,7 +2079,10 @@ rl_callback_read_char(void)
  		} else
  			wbuf = NULL;
  		(*(void (*)(const char *))rl_linefunc)(wbuf);
 -		el_set(e, EL_UNBUFFERED, 1);
 +		if (!rl_already_prompted) {
 +		    el_set(e, EL_UNBUFFERED, 1);
 +		    rl_already_prompted = 1;
 +		}
  	}
  }