svn change r6839 breaks screendump from monitor

[Ryan Harper <ryanh@us.ibm.com>]

Running a something simple like:

% ./x86_64-softmmu/qemu-system-x86_64 -L pc-bios -hda /dev/null -monitor stdio
Could not open '/dev/kqemu' - QEMU acceleration layer not activated: No such file or directory
QEMU 0.10.0 monitor - type 'help' for more information
(qemu) screendump /tmp/f.ppm
Segmentation fault

qemu tip is broken
qemu stable 0.10.1 is OK, svn r6838 is OK.
kvm-84 OK, kvm-userspace.git tip broken from when r6839 was merged.

core stack trace looks like:


Core was generated by `./x86_64-softmmu/qemu-system-x86_64 -L pc-bios -hda /dev/null -monitor stdio'.
Program terminated with signal 11, Segmentation fault.
[New process 7388]
#0  0x0000000000437825 in vga_screen_dump_common (s=0xc79240, filename=0xbf6c10 "/tmp/foo.ppm", w=720, h=400)
    at ../console.h:152
152     return ds->allocator->create_displaysurface(width, height);    
(gdb) bt
#0  0x0000000000437825 in vga_screen_dump_common (s=0xc79240, filename=0xbf6c10 "/tmp/foo.ppm", w=720, h=400)
    at ../console.h:152
#1  0x0000000000437907 in vga_screen_dump (opaque=0xc79240, filename=0xbf6c10 "/tmp/foo.ppm")
    at /home/rharper/work/git/build/qemu/hw/vga.c:2650
#2  0x0000000000468c3b in vga_hw_screen_dump (filename=0x7fff91e4ba70 "") at console.c:183
#3  0x00000000004100aa in monitor_handle_command (mon=0xcdf8d0, cmdline=<value optimized out>)
    at /home/rharper/work/git/build/qemu/monitor.c:2741
#4  0x0000000000410194 in monitor_command_cb (mon=0xcdf8d0, cmdline=0xce1a60 "screendump /tmp/foo.ppm", 
    opaque=<value optimized out>) at /home/rharper/work/git/build/qemu/monitor.c:3009
#5  0x0000000000468686 in readline_handle_byte (rs=0xce1a60, ch=<value optimized out>) at readline.c:367
#6  0x00000000004101fd in monitor_read (opaque=<value optimized out>, buf=<value optimized out>, size=1)
    at /home/rharper/work/git/build/qemu/monitor.c:2995
#7  0x000000000047f094 in fd_chr_read (opaque=0xbf6a20) at qemu-char.c:565
#8  0x0000000000408ff2 in main_loop_wait (timeout=<value optimized out>)
    at /home/rharper/work/git/build/qemu/vl.c:3747
#9  0x000000000040cbba in main (argc=7, argv=0x7fff91e4d228, envp=<value optimized out>)
    at /home/rharper/work/git/build/qemu/vl.c:3931


-- 
Ryan Harper
Software Engineer; Linux Technology Center
IBM Corp., Austin, Tx
ryanh@us.ibm.com