Emacs aborts (xassert) when PageUp key used in semi-binary file

[Tim Van Holder]

This is probably related to the problem I reported this morning.
This time I had a semi-binary file (some sort of mainframe file dump)
open (i.e. there were lots of \nnn character respresentations in the
buffer (plain old Fundamental mode).  Pressing PageUp when halfway
through the file caused emacs to abort.

gdb stacktrace:

Breakpoint 1, abort () at $HOME/gnu/emacs/src/emacs.c:454
454       kill (getpid (), SIGABRT);
(gdb) up
#1  0x08072309 in move_it_vertically_backward (it=0xbfffc8c0, dy=0) at
$HOME/gnu/emacs/src/xdisp.c:6296
6296          xassert (IT_CHARPOS (*it) <= start_pos);
(gdb) up
#2  0x08072747 in move_it_by_lines (it=0xbfffc8c0, dvpos=-2,
need_y_p=0) at $HOME/gnu/emacs/src/xdisp.c:6470
6470          move_it_vertically_backward (it, 0);
(gdb) up
#3  0x080a5de7 in window_scroll_pixel_based (window=138754572, n=-1,
whole=1, noerror=0) at $HOME/gnu/emacs/src/window.c:4809
4809                  move_it_by_lines (&it, -2, 0);
(gdb) bt
#0  abort () at $HOME/gnu/emacs/src/emacs.c:454
#1  0x08072309 in move_it_vertically_backward (it=0xbfffc8c0, dy=0) at
$HOME/gnu/emacs/src/xdisp.c:6296
#2  0x08072747 in move_it_by_lines (it=0xbfffc8c0, dvpos=-2,
need_y_p=0) at $HOME/gnu/emacs/src/xdisp.c:6470
#3  0x080a5de7 in window_scroll_pixel_based (window=138754572, n=-1,
whole=1, noerror=0) at $HOME/gnu/emacs/src/window.c:4809
#4  0x080a4f86 in window_scroll (window=138754572, n=-1, whole=1,
noerror=0) at $HOME/gnu/emacs/src/window.c:4518
#5  0x080a63cc in scroll_command (n=137731209, direction=-1) at
$HOME/gnu/emacs/src/window.c:4993
#6  0x080a6489 in Fscroll_down (arg=137731209) at
$HOME/gnu/emacs/src/window.c:5029
#7  0x08193fb7 in Feval (form=138461741) at $HOME/gnu/emacs/src/eval.c:2130
#8  0x08192aca in Fcondition_case (args=142486045) at
$HOME/gnu/emacs/src/eval.c:1332
#9  0x081c9d8a in Fbyte_code (bytestr=137933227, vector=141065860,
maxdepth=24) at $HOME/gnu/emacs/src/bytecode.c:864
#10 0x08195597 in funcall_lambda (fun=139928388, nargs=1,
arg_vector=0xbfffd014) at $HOME/gnu/emacs/src/eval.c:2967
#11 0x08194fbe in Ffuncall (nargs=2, args=0xbfffd010) at
$HOME/gnu/emacs/src/eval.c:2828
#12 0x08190cf8 in Fcall_interactively (function=142025345,
record_flag=137731209, keys=137788084)
    at $HOME/gnu/emacs/src/callint.c:877
#13 0x08127672 in Fcommand_execute (cmd=142025345,
record_flag=137731209, keys=137731209, special=137731209)
    at $HOME/gnu/emacs/src/keyboard.c:9693
#14 0x0811a86a in command_loop_1 () at $HOME/gnu/emacs/src/keyboard.c:1788
#15 0x08192bdd in internal_condition_case (bfun=0x8119479
<command_loop_1>, handlers=137792201, hfun=0x8118fb6 <cmd_error>)
    at $HOME/gnu/emacs/src/eval.c:1385
#16 0x081192fb in command_loop_2 () at $HOME/gnu/emacs/src/keyboard.c:1315
#17 0x081926bc in internal_catch (tag=137786201, func=0x81192d8
<command_loop_2>, arg=137731209)
    at $HOME/gnu/emacs/src/eval.c:1144
#18 0x081192b1 in command_loop () at $HOME/gnu/emacs/src/keyboard.c:1294
#19 0x08118d38 in recursive_edit_1 () at $HOME/gnu/emacs/src/keyboard.c:987
#20 0x08118e7d in Frecursive_edit () at $HOME/gnu/emacs/src/keyboard.c:1048
#21 0x081177ad in main (argc=3, argv=0xbfffda04) at
$HOME/gnu/emacs/src/emacs.c:1763