Segfault in rootwin_do_set_focus() in 20060107

[Daniel Erat]

I've been seeing crashes once or twice a week in ion3 20051210 and
20060107.  They seem to typically get triggered when I'm opening or
closing a firefox window that includes flash content.  I finally got a
core dump:

gdb bin/ion3 core.0
...
Program terminated with signal 11, Segmentation fault.
...
#0  0x08060c41 in rootwin_do_set_focus (rootwin=0x80bb750, warp=0) at
rootwin.c:448
448             FOR_ALL_SCREENS(scr){
(gdb) bt
#0  0x08060c41 in rootwin_do_set_focus (rootwin=0x80bb750, warp=0) at
rootwin.c:448
#1  0x0805c160 in region_do_set_focus (reg=0x80bb750, warp=0) at region.c:178
#2  0x08056da6 in ioncore_flush () at event.c:191
#3  0x08056e2f in ioncore_mainloop () at event.c:230
#4  0x080568d9 in main (argc=134745490, argv=0xffffffff) at ion.c:289

>From rootwin_do_set_focus() in rootwin.c:
  if(sub==NULL || !REGION_IS_MAPPED(sub)){
      WScreen *scr;
      FOR_ALL_SCREENS(scr){
          if(REGION_IS_MAPPED(sub)){
              sub=(WRegion*)scr;
              break;
          }
      }
  }

>From region.h:
  #define REGION_IS_MAPPED(R)     (((WRegion*)(R))->flags&REGION_MAPPED)

Back to gdb:
(gdb) print sub
$1 = (WRegion *) 0x0

Not knowing anything about the ion source, the "sub == NULL" test
followed by a call to a macro that dereferences sub seems like a bad
idea to me. :)