[src/trunk]: src/lib/libcurses Fix a NULL dereference if the exit_alt_charset...

[dsainty <dsainty%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/0b23219d52ee
branches:  trunk
changeset: 790193:0b23219d52ee
user:      dsainty <dsainty%NetBSD.org@localhost>
date:      Wed Sep 25 03:28:20 2013 +0000

description:
Fix a NULL dereference if the exit_alt_charset_mode capability is not defined.

The previous version of this file changed a terminal initialisation test on
the exit_attribute_mode capability, checking for the exit_alt_charset_mode
capability as a substring, rather than performing a search for the hard-coded
^O character.

That works better on terminals where ^O is not the correct value for
exit_alt_charset_mode.  But it works worse on terminals that don't have a
definition specified for exit_alt_charset_mode.

For example:

% TERMCAP='xterm:me=\E[m:' TERM=xterm vi
segmentation fault (core dumped)  TERMCAP='xterm:me=\E[m:' TERM=xterm vi

The crash can be avoided (without fixing the bug) by defining
exit_alt_charset_mode:

% TERMCAP='xterm|:me=\E[m:ae=:' TERM=xterm vi
ex/vi: Error: xterm: No such process

We now test exit_alt_charset_mode for NULL before continuing with the fatal
test, restoring the original no-crash behaviour.

XXX does_ctrl_o() is now just a naive reimplementation of strstr(), so should
probably just use strstr() instead.

diffstat:

 lib/libcurses/setterm.c |  5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diffs (26 lines):

diff -r 45af7694ae2f -r 0b23219d52ee lib/libcurses/setterm.c
--- a/lib/libcurses/setterm.c   Wed Sep 25 03:14:55 2013 +0000
+++ b/lib/libcurses/setterm.c   Wed Sep 25 03:28:20 2013 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: setterm.c,v 1.50 2013/05/05 14:24:05 jdc Exp $ */
+/*     $NetBSD: setterm.c,v 1.51 2013/09/25 03:28:20 dsainty Exp $     */
 
 /*
  * Copyright (c) 1981, 1993, 1994
@@ -34,7 +34,7 @@
 #if 0
 static char sccsid[] = "@(#)setterm.c  8.8 (Berkeley) 10/25/94";
 #else
-__RCSID("$NetBSD: setterm.c,v 1.50 2013/05/05 14:24:05 jdc Exp $");
+__RCSID("$NetBSD: setterm.c,v 1.51 2013/09/25 03:28:20 dsainty Exp $");
 #endif
 #endif /* not lint */
 
@@ -172,6 +172,7 @@
         * It might turn off ACS, so check for that.
         */
        if (t_exit_attribute_mode(screen->term) != NULL &&
+           t_exit_alt_charset_mode(screen->term) != NULL &&
            does_ctrl_o(t_exit_attribute_mode(screen->term),
            t_exit_alt_charset_mode(screen->term)))
                screen->mask_me = 0;