Hi tech@
attaching a fix for the following crash caused by a null pointer dereference
while the modeline is trying to work on a unusable display
#0 0x00000bf6a4e04433 in modeline (wp=0xbf948d9d400, modelinecolor=2) at
display.c:800
800 vscreen[n]->v_color = modelinecolor; /* Mode line color.
*/
(gdb) bt
#0 0x00000bf6a4e04433 in modeline (wp=0xbf948d9d400, modelinecolor=2) at
display.c:800
#1 0x00000bf6a4e04ecf in update (modelinecolor=2) at display.c:501
#2 0x00000bf6a4e0ee28 in main (argc=Variable "argc" is not available.
) at main.c:199
quite easy to reproduce:
1. start a tmux session
2. split the screen in half (^B ")
3. start mg in one screen
4. resize the mg screen to 2 lines (smallest allow by tmux)
5. by now tmux should be showing unusable display
6. type something or do a modeline command
segfault.
The interesting thing is that mg works without a crash if it's started from
a 2 line display regardless of what you do. So I am having doubts how sane
that check for 'unusable' display is.
I also assume there might be more places that die when trying to work
with an unusable display (I didn't find/hit them yet).
Thinking about it made me try another diff. Which removes the 'window is
unusable'
check completely. So far I havent seen a single crash with it and I can resize
the window down to 2 lines and back.
I guess I'm asking for an OK for the second diff (or a reason why we should not)
versus OK'ing the first one :)
Regards,
awolk
Index: display.c
===================================================================
RCS file: /cvs/src/usr.bin/mg/display.c,v
retrieving revision 1.47
diff -u -p -r1.47 display.c
--- display.c 3 Apr 2015 22:10:29 -0000 1.47
+++ display.c 6 Sep 2016 21:15:51 -0000
@@ -797,6 +797,8 @@ modeline(struct mgwin *wp, int modelinec
int len;
n = wp->w_toprow + wp->w_ntrows; /* Location. */
+ if (!vscreen[n])
+ return;
vscreen[n]->v_color = modelinecolor; /* Mode line color. */
vscreen[n]->v_flag |= (VFCHG | VFHBAD); /* Recompute, display. */
vtmove(n, 0); /* Seek to right line. */
Index: window.c
===================================================================
RCS file: /cvs/src/usr.bin/mg/window.c,v
retrieving revision 1.36
diff -u -p -r1.36 window.c
--- window.c 18 Nov 2015 18:21:06 -0000 1.36
+++ window.c 6 Sep 2016 21:29:48 -0000
@@ -89,12 +89,6 @@ do_redraw(int f, int n, int force)
while (wp->w_wndp != NULL)
wp = wp->w_wndp;
- /* check if too small */
- if (nrow < wp->w_toprow + 3) {
- dobeep();
- ewprintf("Display unusable");
- return (FALSE);
- }
wp->w_ntrows = nrow - wp->w_toprow - 2;
sgarbf = TRUE;
update(CMODE);
