Elusive assertion failure related to completion

[Juanma Barranquero]

This is a crash I can consistently get while completing function
names. I'm not yet filing a bug report because details are a bit
sketchy.

Basically, starting Emacs my init.el, I do

 C-h f -functions

and I get an assertion failure:

  eval.c:3428: Emacs fatal error: assertion failed: SYMBOLP(this_binding.symbol)

  This application has requested the Runtime to terminate it in an unusual way.
  Please contact the application's support team for more information.

Unfortunately, trimming init.el to detect what's triggering it is not
easy; just commenting code around makes the bug much harder to
reproduce (but it still happens).

I just stumbled upon the bug today, but I can consistently repeat it
all the way to 23.0.90; I haven't tested earlier versions. As the
backtraces below suggest, it is related to using icomplete; removing
it makes the bug disappear.

I've been trying to debug it, but the backtraces are not always
identical. One sample follows.

    Juanma



gdb: unknown target exception 0xc0000029 at 0x7c9601cc

Program received signal ?, Unknown signal.
[Switching to thread 3668.0x718]
0x7c9601cc in ntdll!LdrFindEntryForAddress () from C:\WINDOWS\system32\ntdll.dll
(gdb) bt
#0  0x7c9601cc in ntdll!LdrFindEntryForAddress () from
C:\WINDOWS\system32\ntdll.dll
#1  0x0082e21c in ?? ()
#2  0x207ffe48 in ?? ()
#3  0x0082ffe0 in ?? ()
#4  0xc0000027 in ?? ()
#5  0x00000002 in ?? ()
#6  0x00000000 in ?? ()

Lisp Backtrace:
"byte-code" (0x82e510)
"icomplete-exhibit" (0x82e9f8)
"run-hooks" (0x82eaa4)
0x3040da4 PVEC_COMPILED
"run-hooks" (0x82eee4)
"completing-read" (0x82f4f0)
"setq" (0x82f668)
"let" (0x82f7f8)
"call-interactively" (0x82fafc)
(gdb) thread 1
[Switching to thread 1 (thread 3668.0x2f0)]#0  delete_all_subwindows
(w=0x33c0a00) at window.c:6314
6314      w->total_lines = w->buffer;       /* See
Fset_window_configuration for excuse.  */
(gdb) bt
#0  delete_all_subwindows (w=0x33c0a00) at window.c:6314
#1  0x011c099a in delete_all_subwindows (w=0x33c0000) at window.c:6308
#2  0x011bf523 in Fset_window_configuration (configuration=59128388)
at window.c:6105
#3  0x0103f82c in unbind_to (count=60, value=48252929) at eval.c:3401
#4  0x01193415 in Fall_completions (string=20048835,
collection=48254980, predicate=48317513, hide_spaces=48252929) at
minibuf.c:1693
#5  0x0103e191 in Ffuncall (nargs=4, args=0x82be10) at eval.c:3056
#6  0x011df86d in Fbyte_code (bytestr=20345539, vector=20345660,
maxdepth=40) at bytecode.c:678
#7  0x0103ecbd in funcall_lambda (fun=20345476, nargs=4,
arg_vector=0x82c138) at eval.c:3233
#8  0x0103e519 in Ffuncall (nargs=5, args=0x82c134) at eval.c:3092
#9  0x011df86d in Fbyte_code (bytestr=20346979, vector=20347036,
maxdepth=48) at bytecode.c:678
#10 0x0103c3c9 in Feval (form=20346965) at eval.c:2383
#11 0x0103a0da in internal_lisp_condition_case (var=48757169,
bodyform=20346965, handlers=20347077) at eval.c:1458
#12 0x011e0526 in Fbyte_code (bytestr=20346547, vector=20346764,
maxdepth=80) at bytecode.c:868
#13 0x0103ecbd in funcall_lambda (fun=20346468, nargs=4,
arg_vector=0x82c844) at eval.c:3233
#14 0x0103e519 in Ffuncall (nargs=5, args=0x82c840) at eval.c:3092
#15 0x011df86d in Fbyte_code (bytestr=20347315, vector=20347404,
maxdepth=48) at bytecode.c:678
#16 0x0103ecbd in funcall_lambda (fun=20347260, nargs=4,
arg_vector=0x82cb64) at eval.c:3233
#17 0x0103e519 in Ffuncall (nargs=5, args=0x82cb60) at eval.c:3092
#18 0x011df86d in Fbyte_code (bytestr=20333499, vector=20333556,
maxdepth=40) at bytecode.c:678
#19 0x0103ecbd in funcall_lambda (fun=20333468, nargs=1,
arg_vector=0x82ce84) at eval.c:3233
#20 0x0103e519 in Ffuncall (nargs=2, args=0x82ce80) at eval.c:3092
#21 0x011df86d in Fbyte_code (bytestr=20328795, vector=20328844,
maxdepth=24) at bytecode.c:678
#22 0x0103c3c9 in Feval (form=20328781) at eval.c:2383
#23 0x0103a0da in internal_lisp_condition_case (var=48757169,
bodyform=20328781, handlers=20328877) at eval.c:1458
#24 0x011e0526 in Fbyte_code (bytestr=20328683, vector=20328740,
maxdepth=24) at bytecode.c:868
#25 0x0103ecbd in funcall_lambda (fun=20328636, nargs=2,
arg_vector=0x82d564) at eval.c:3233
#26 0x0103e519 in Ffuncall (nargs=3, args=0x82d560) at eval.c:3092
#27 0x011df86d in Fbyte_code (bytestr=20333659, vector=20333716,
maxdepth=40) at bytecode.c:678
#28 0x0103ecbd in funcall_lambda (fun=20333596, nargs=4,
arg_vector=0x82d884) at eval.c:3233
#29 0x0103e519 in Ffuncall (nargs=5, args=0x82d880) at eval.c:3092
#30 0x011df86d in Fbyte_code (bytestr=20335099, vector=20335212,
maxdepth=56) at bytecode.c:678
#31 0x0103ecbd in funcall_lambda (fun=20335076, nargs=0,
arg_vector=0x82dba4) at eval.c:3233
#32 0x0103e519 in Ffuncall (nargs=1, args=0x82dba0) at eval.c:3092
#33 0x011df86d in Fbyte_code (bytestr=50133139, vector=56130308,
maxdepth=72) at bytecode.c:678
#34 0x0103ecbd in funcall_lambda (fun=50640196, nargs=4,
arg_vector=0x82ded4) at eval.c:3233
#35 0x0103e519 in Ffuncall (nargs=5, args=0x82ded0) at eval.c:3092
#36 0x011df86d in Fbyte_code (bytestr=50132915, vector=50233476,
maxdepth=40) at bytecode.c:678
#37 0x0103c3c9 in Feval (form=56006373) at eval.c:2383
#38 0x01039c2f in internal_catch (tag=55585033, func=0x103b98b
<Feval>, arg=56006373) at eval.c:1249
#39 0x011e0492 in Fbyte_code (bytestr=50226035, vector=50640036,
maxdepth=16) at bytecode.c:853
#40 0x0103c3c9 in Feval (form=56006605) at eval.c:2383
#41 0x0103a0da in internal_lisp_condition_case (var=48252929,
bodyform=56006605, handlers=56006229) at eval.c:1458
#42 0x011e0526 in Fbyte_code (bytestr=50227795, vector=55440516,
maxdepth=56) at bytecode.c:868
#43 0x0103ecbd in funcall_lambda (fun=50642660, nargs=0,
arg_vector=0x82e9f8) at eval.c:3233
#44 0x0103e519 in Ffuncall (nargs=1, args=0x82e9f4) at eval.c:3092
#45 0x0103d2b5 in run_hook_with_args (nargs=1, args=0x82e9f4,
cond=to_completion) at eval.c:2705
#46 0x0103cffa in Frun_hooks (nargs=1, args=0x82eaa4) at eval.c:2568
#47 0x0103dc44 in Ffuncall (nargs=2, args=0x82eaa0) at eval.c:3027
#48 0x011df86d in Fbyte_code (bytestr=52989251, vector=50204292,
maxdepth=16) at bytecode.c:678
#49 0x0103ecbd in funcall_lambda (fun=50597284, nargs=0,
arg_vector=0x82ee28) at eval.c:3233
#50 0x0103e519 in Ffuncall (nargs=1, args=0x82ee24) at eval.c:3092
#51 0x0103d2b5 in run_hook_with_args (nargs=1, args=0x82ee24,
cond=to_completion) at eval.c:2705
#52 0x0103cffa in Frun_hooks (nargs=1, args=0x82eee4) at eval.c:2568
#53 0x0103dc44 in Ffuncall (nargs=2, args=0x82eee0) at eval.c:3027
#54 0x0103d5b7 in call1 (fn=48423985, arg1=48304657) at eval.c:2827
#55 0x0100b9c6 in safe_run_hooks_1 (hook=2) at keyboard.c:2158
#56 0x0103a1d6 in internal_condition_case (bfun=0x100b992
<safe_run_hooks_1>, handlers=48252977, hfun=0x100b9d1
<safe_run_hooks_error>)
    at eval.c:1513
#57 0x0100ba70 in safe_run_hooks (hook=48304657) at keyboard.c:2186
#58 0x0100a9d7 in command_loop_1 () at keyboard.c:1922
#59 0x0103a1d6 in internal_condition_case (bfun=0x100725a
<command_loop_1>, handlers=48316609, hfun=0x10069d0 <cmd_error>) at
eval.c:1513
#60 0x01006e69 in command_loop_2 () at keyboard.c:1359
#61 0x01039c2f in internal_catch (tag=48426657, func=0x1006e49
<command_loop_2>, arg=48252929) at eval.c:1249
#62 0x01006dd2 in command_loop () at keyboard.c:1324
#63 0x01006127 in recursive_edit_1 () at keyboard.c:953
#64 0x011903f2 in read_minibuf (map=48242149, initial=48252929,
prompt=60318691, backup_n=0, expflag=0, histvar=48480121, histpos=0,
    defalt=20410179, allow_props=0, inherit_input_method=0) at minibuf.c:739
#65 0x01193769 in Fcompleting_read (prompt=60318691,
collection=48254980, predicate=48317513, require_match=48252977,
    initial_input=48252929, hist=48252929, def=20410179,
inherit_input_method=48252929) at minibuf.c:1823
#66 0x0103c73d in Feval (form=52546973) at eval.c:2405
#67 0x01037f3d in Fsetq (args=52546965) at eval.c:552
#68 0x0103beb1 in Feval (form=52546957) at eval.c:2324
#69 0x01037d69 in Fprogn (args=52546717) at eval.c:450
#70 0x01039788 in Flet (args=52546949) at eval.c:1091
#71 0x0103beb1 in Feval (form=52546869) at eval.c:2324
#72 0x011e3152 in Fcall_interactively (function=49501401,
record_flag=48252929, keys=48286468) at callint.c:364
#73 0x0103e0f0 in Ffuncall (nargs=4, args=0x82faf8) at eval.c:3052
#74 0x0103d62d in call3 (fn=48450945, arg1=49501401, arg2=48252929,
arg3=48252929) at eval.c:2872
#75 0x01023f40 in Fcommand_execute (cmd=49501401,
record_flag=48252929, keys=48252929, special=48252929) at
keyboard.c:10530
#76 0x0100a977 in command_loop_1 () at keyboard.c:1903
#77 0x0103a1d6 in internal_condition_case (bfun=0x100725a
<command_loop_1>, handlers=48316609, hfun=0x10069d0 <cmd_error>) at
eval.c:1513
#78 0x01006e69 in command_loop_2 () at keyboard.c:1359
#79 0x01039c2f in internal_catch (tag=48312729, func=0x1006e49
<command_loop_2>, arg=48252929) at eval.c:1249
#80 0x01006e20 in command_loop () at keyboard.c:1338
#81 0x01006127 in recursive_edit_1 () at keyboard.c:953
#82 0x010065fc in Frecursive_edit () at keyboard.c:1015
#83 0x01002a8d in main (argc=1, argv=0xa92720) at emacs.c:1849

Lisp Backtrace:
"byte-code" (0x82e510)
"icomplete-exhibit" (0x82e9f8)
"run-hooks" (0x82eaa4)
0x3040da4 PVEC_COMPILED
"run-hooks" (0x82eee4)
"completing-read" (0x82f4f0)
"setq" (0x82f668)
"let" (0x82f7f8)
"call-interactively" (0x82fafc)
(gdb)