On Sat, May 4, 2024 at 12:11 AM Eli Zaretskii <eliz@gnu.org> wrote:

> I have
> no idea how VirtualBox converts Windows clipboard data into X
> clipboard/selection data -- do you happen to know?  The reason of this
> problem is probably there.
>

Sorry I am unfamiliar with how VirtualBox implements this. I know they use
something called guest addition to allow bi-directional clipboard sharing.


> And finally, the values of the following variables are of interest:
>
> > #11 0x000055b069603f3e in print_error_message (data=<optimized out>,
> data@entry=0x55b085976613,
> > stream=stream@entry=0x30, context=<optimized out>, caller=caller@entry=0x7fe0)
> at lisp.h:1172
> >         obj = <optimized out>
> >         li = {tortoise = 0x55b0859765f3, max = 2, n = 0, q = 1}
> >         sep = 0x55b0696ad6a0 ", "
> >         errname = 0x11f40
> >         errmsg = 0x55b06c78e6e4
> >         file_error = 0x0
> >         tail = 0x55b0859765e3
>
> In this call-stack frame, what is the value of 'data'?  It is a Lisp
> object, so showing it should involve using the commands xtype, xcar,
> and xcdr, and probably also xstring (which are defined in .gdbinit).


I did as directed. Emacs soon crashed and here is the analysis:
(gdb) bt full
#0  raise (sig=<optimized out>) at ../sysdeps/unix/sysv/linux/raise.c:50
        set = {
          __val = {18446744067266837247, 0 <repeats 15 times>}
        }
        pid = <optimized out>
        tid = <optimized out>
#1  0x0000564c4c3e5cf8 in terminate_due_to_signal (sig=11,
backtrace_limit=40) at emacs.c:464
#2  0x0000564c4c4141b2 in handle_fatal_signal (sig=11) at sysdep.c:1783
#3  0x0000564c4c414187 in deliver_thread_signal (sig=11,
handler=0x564c4c414198 <handle_fatal_signal>) at sysdep.c:1775
        old_errno = 11
#4  0x0000564c4c4141ed in deliver_fatal_thread_signal (sig=11) at
sysdep.c:1795
#5  0x0000564c4c41438b in handle_sigsegv (sig=11, siginfo=0x564c4cb3e230
<sigsegv_stack+64528>, arg=0x564c4cb3e100 <sigsegv_stack+64224>) at
sysdep.c:1888
        fatal = false
#6  0x00007f8907b26140 in <signal handler called> () at
/lib/x86_64-linux-gnu/libpthread.so.0
#7  SYMBOL_NAME (sym=XIL(0x564c55abc5a0)) at lisp.h:2336
#8  0x0000564c4c4e0ca5 in print_object (obj=XIL(0x564c55abc5a0),
printcharfun=XIL(0x30), escapeflag=true) at print.c:2393
        len = 140226424574408
        i = 140729353894864
        name = XIL(0x21974e0)
        size_byte = 94885739624928
        p = 0x564c4c41f35a <set_buffer_internal_2+227> "H\213@
\bH\205\300t\fH\213E\330H\211\307\350\336\362\006"
        signedp = false
        confusing = false
        base_depth = 0
        base_sp = 0
        buf =
"\020H\220SLV\000\000\020H\220SLV\000\000`\205\264LLV\000\000`\000\000\000\000\000\000\000`\000\000\000\000\000\000\000\000\374%\033\376\177\000\000ܖHLLV"
#9  0x0000564c4c4dddb4 in print (obj=XIL(0x564c55abc5a0),
printcharfun=XIL(0x30), escapeflag=true) at print.c:1301
#10 0x0000564c4c4dcc92 in Fprin1 (object=XIL(0x564c55abc5a0),
printcharfun=XIL(0x30), overrides=XIL(0)) at print.c:776
        count = {
          bytes = 224
        }
        pc = {
          printcharfun = XIL(0x30),
          old_printcharfun = XIL(0x30),
          old_point = -1,
          start_point = -1,
          old_point_byte = -1,
          start_point_byte = -1,
          specpdl_count = {
            bytes = 224
          }
        }
#11 0x0000564c4c4dd82f in print_error_message (data=XIL(0x564c52d9c853),
stream=XIL(0x30), context=0x7f89023daa83 "", caller=XIL(0x293cb518a578)) at
print.c:1134
        obj = XIL(0x564c55abc5a0)
        li = {
          tortoise = XIL(0x564c52d9c873),
          max = 2,
          n = 0,
          q = 1
        }
        sep = 0x564c4c5c1c0c ", "
        errname = XIL(0x11f40)
        errmsg = XIL(0x564c520b0a84)
        file_error = XIL(0)
        tail = XIL(0x564c52d9c883)
#12 0x0000564c4c3ed1a9 in Fcommand_error_default_function
(data=XIL(0x564c52d9c853), context=XIL(0x7f8901be9284),
signal=XIL(0x293cb518a578)) at keyboard.c:1070
        sf = 0x564c4ec8f6c8
        conditions = XIL(0x7f89022845e3)
        is_minibuffer_quit = 0
#13 0x0000564c4c4b09a7 in funcall_subr (subr=0x564c4cabd2e0
<Scommand_error_default_function>, numargs=3, args=0x7f89014b1050) at
eval.c:3042
        argbuf = {XIL(0x564c4cb48500), XIL(0), XIL(0), XIL(0x7ffe1b25ffa0),
XIL(0x564c4c4ffe4b), XIL(0x4cabd2e5), XIL(0x7ffe1b25ffc0),
XIL(0x564c4c500741)}
        a = 0x7f89014b1050
        fun = XIL(0x7ffe1b25ffe0)
#14 0x0000564c4c50176b in exec_byte_code (fun=XIL(0x7f890204f18d),
args_template=771, nargs=3, args=0x7ffe1b260640) at bytecode.c:809
        call_nargs = 3
        call_fun = XIL(0x564c4cabd2e5)
        count1 = {
          bytes = 192
        }
        template = XIL(0x21b2600a0)
        val = XIL(0)
        call_args = 0x7f89014b1050
        original_fun = XIL(0x293cb5507120)
        bytecode = make_fixnum(1393703692)
        op = 3
        type = (unknown: 0x2398d60)
        targets =
          {0x564c4c504e7e <exec_byte_code+17280>, 0x564c4c504ea3
<exec_byte_code+17317>, 0x564c4c504ea5 <exec_byte_code+17319>,
0x564c4c504ea7 <exec_byte_code+17321>, 0x564c4c504ea9
<exec_byte_code+17323>, 0x564c4c504ea9 <exec_byte_code+17323>,
0x564c4c504f0e <exec_byte_code+17424>, 0x564c4c504f82
<exec_byte_code+17540>, 0x564c4c500f00 <exec_byte_code+1026>,
0x564c4c500f02 <exec_byte_code+1028>, 0x564c4c500f04 <exec_byte_code+1030>,
0x564c4c500f06 <exec_byte_code+1032>, 0x564c4c500f08 <exec_byte_code+1034>,
0x564c4c500f08 <exec_byte_code+1034>, 0x564c4c500f0e <exec_byte_code+1040>,
0x564c4c500ecf <exec_byte_code+977>, 0x564c4c50128d <exec_byte_code+1935>,
0x564c4c50128f <exec_byte_code+1937>, 0x564c4c501291 <exec_byte_code+1939>,
0x564c4c501293 <exec_byte_code+1941>, 0x564c4c501295 <exec_byte_code+1943>,
0x564c4c501295 <exec_byte_code+1943>, 0x564c4c5012ca <exec_byte_code+1996>,
0x564c4c50129b <exec_byte_code+1949>, 0x564c4c501480 <exec_byte_code+2434>,
0x564c4c501482 <exec_byte_code+2436>, 0x564c4c501484 <exec_byte_code+2438>,
0x564c4c501486 <exec_byte_code+2440>, 0x564c4c501488 <exec_byte_code+2442>,
0x564c4c501488 <exec_byte_code+2442>, 0x564c4c50143a <exec_byte_code+2364>,
0x564c4c501451 <exec_byte_code+2387>, 0x564c4c501535 <exec_byte_code+2615>,
0x564c4c501537 <exec_byte_code+2617>, 0x564c4c501539 <exec_byte_code+2619>,
0x564c4c50153b <exec_byte_code+2621>, 0x564c4c50153d <exec_byte_code+2623>,
0x564c4c50153d <exec_byte_code+2623>, 0x564c4c5014ef <exec_byte_code+2545>,
0x564c4c501506 <exec_byte_code+2568>, 0x564c4c501890 <exec_byte_code+3474>,
0x564c4c501892 <exec_byte_code+3476>, 0x564c4c501894 <exec_byte_code+3478>,
0x564c4c501896 <exec_byte_code+3480>, 0x564c4c501898 <exec_byte_code+3482>,
0x564c4c501898 <exec_byte_code+3482>, 0x564c4c50184a <exec_byte_code+3404>,
0x564c4c501861 <exec_byte_code+3427>, 0x564c4c5020e0 <exec_byte_code+5602>,
0x564c4c501f36 <exec_byte_code+5176>, 0x564c4c501f2d <exec_byte_code+5167>,
0x564c4c504e7e <exec_byte_code+17280>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c504e7e <exec_byte_code+17280>,
0x564c4c504e7e <exec_byte_code+17280>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c502325 <exec_byte_code+6183>,
0x564c4c50240f <exec_byte_code+6417>, 0x564c4c502471 <exec_byte_code+6515>,
0x564c4c5024d1 <exec_byte_code+6611>, 0x564c4c502533 <exec_byte_code+6709>,
0x564c4c501113 <exec_byte_code+1557>, 0x564c4c501195 <exec_byte_code+1687>,
0x564c4c5025ac <exec_byte_code+6830>, 0x564c4c501084 <exec_byte_code+1414>,
0x564c4c5011fd <exec_byte_code+1791>, 0x564c4c502614 <exec_byte_code+6934>,
0x564c4c50267c <exec_byte_code+7038>, 0x564c4c5026c4 <exec_byte_code+7110>,
0x564c4c50272c <exec_byte_code+7214>, 0x564c4c502792 <exec_byte_code+7316>,
0x564c4c502878 <exec_byte_code+7546>, 0x564c4c5028c0 <exec_byte_code+7618>,
0x564c4c502a01 <exec_byte_code+7939>, 0x564c4c502b6d <exec_byte_code+8303>,
0x564c4c502bb5 <exec_byte_code+8375>, 0x564c4c502bfd <exec_byte_code+8447>,
0x564c4c502c65 <exec_byte_code+8551>, 0x564c4c502ccd <exec_byte_code+8655>,
0x564c4c502d35 <exec_byte_code+8759>, 0x564c4c502dba <exec_byte_code+8892>,
0x564c4c502e09 <exec_byte_code+8971>, 0x564c4c502e58 <exec_byte_code+9050>,
0x564c4c502f1f <exec_byte_code+9249>, 0x564c4c502fc1 <exec_byte_code+9411>,
0x564c4c503063 <exec_byte_code+9573>, 0x564c4c503132 <exec_byte_code+9780>,
0x564c4c503214 <exec_byte_code+10006>, 0x564c4c5032f6
<exec_byte_code+10232>, 0x564c4c5033d8 <exec_byte_code+10458>,
0x564c4c5034ba <exec_byte_code+10684>, 0x564c4c5035ec
<exec_byte_code+10990>, 0x564c4c50368f <exec_byte_code+11153>,
0x564c4c5037bb <exec_byte_code+11453>, 0x564c4c503881
<exec_byte_code+11651>, 0x564c4c503947 <exec_byte_code+11849>,
0x564c4c503ccb <exec_byte_code+12749>, 0x564c4c501dad
<exec_byte_code+4783>, 0x564c4c503d26 <exec_byte_code+12840>,
0x564c4c503d6e <exec_byte_code+12912>, 0x564c4c503e30
<exec_byte_code+13106>, 0x564c4c503e8b <exec_byte_code+13197>,
0x564c4c503ee6 <exec_byte_code+13288>, 0x564c4c503f2e
<exec_byte_code+13360>, 0x564c4c503f71 <exec_byte_code+13427>,
0x564c4c503fb4 <exec_byte_code+13494>, 0x564c4c503fff
<exec_byte_code+13569>, 0x564c4c504e7e <exec_byte_code+17280>,
0x564c4c504057 <exec_byte_code+13657>, 0x564c4c50409a
<exec_byte_code+13724>, 0x564c4c5040dd <exec_byte_code+13791>,
0x564c4c504120 <exec_byte_code+13858>, 0x564c4c504163
<exec_byte_code+13925>, 0x564c4c5041a6 <exec_byte_code+13992>,
0x564c4c501dad <exec_byte_code+4783>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c5041ee <exec_byte_code+14064>,
0x564c4c50423e <exec_byte_code+14144>, 0x564c4c504286
<exec_byte_code+14216>, 0x564c4c5042ce <exec_byte_code+14288>,
0x564c4c504336 <exec_byte_code+14392>, 0x564c4c50439e
<exec_byte_code+14496>, 0x564c4c5043e6 <exec_byte_code+14568>,
0x564c4c50442e <exec_byte_code+14640>, 0x564c4c504496
<exec_byte_code+14744>, 0x564c4c5044fe <exec_byte_code+14848>,
0x564c4c504566 <exec_byte_code+14952>, 0x564c4c5045a9
<exec_byte_code+15019>, 0x564c4c504e7e <exec_byte_code+17280>,
0x564c4c501cf7 <exec_byte_code+4601>, 0x564c4c5018fe <exec_byte_code+3584>,
0x564c4c500ff2 <exec_byte_code+1268>, 0x564c4c5019a3 <exec_byte_code+3749>,
0x564c4c501a27 <exec_byte_code+3881>, 0x564c4c501aa8 <exec_byte_code+4010>,
0x564c4c501b29 <exec_byte_code+4139>, 0x564c4c501cc0 <exec_byte_code+4546>,
0x564c4c5013e7 <exec_byte_code+2281>, 0x564c4c501d76 <exec_byte_code+4728>,
0x564c4c501de4 <exec_byte_code+4838>, 0x564c4c501e75 <exec_byte_code+4983>,
0x564c4c501ebe <exec_byte_code+5056>, 0x564c4c50212c <exec_byte_code+5678>,
0x564c4c5021a9 <exec_byte_code+5803>, 0x564c4c50222e <exec_byte_code+5936>,
0x564c4c502294 <exec_byte_code+6038>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c5045f1 <exec_byte_code+15091>,
0x564c4c504676 <exec_byte_code+15224>, 0x564c4c5046be
<exec_byte_code+15296>, 0x564c4c504706 <exec_byte_code+15368>,
0x564c4c50474e <exec_byte_code+15440>, 0x564c4c504796
<exec_byte_code+15512>, 0x564c4c5047fe <exec_byte_code+15616>,
0x564c4c504866 <exec_byte_code+15720>, 0x564c4c5048ce
<exec_byte_code+15824>, 0x564c4c504936 <exec_byte_code+15928>,
0x564c4c504a47 <exec_byte_code+16201>, 0x564c4c504aaf
<exec_byte_code+16305>, 0x564c4c504b17 <exec_byte_code+16409>,
0x564c4c504b5f <exec_byte_code+16481>, 0x564c4c504c1d
<exec_byte_code+16671>, 0x564c4c504cdb <exec_byte_code+16861>,
0x564c4c504d23 <exec_byte_code+16933>, 0x564c4c504d6b
<exec_byte_code+17005>, 0x564c4c503a85 <exec_byte_code+12167>,
0x564c4c503bd1 <exec_byte_code+12499>, 0x564c4c504dba
<exec_byte_code+17084>, 0x564c4c504e1c <exec_byte_code+17182>,
0x564c4c504e7e <exec_byte_code+17280>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c504e7e <exec_byte_code+17280>,
0x564c4c504e7e <exec_byte_code+17280>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c504e7e <exec_byte_code+17280>,
0x564c4c502800 <exec_byte_code+7426>, 0x564c4c502ea7 <exec_byte_code+9129>,
0x564c4c503db8 <exec_byte_code+12986>, 0x564c4c505011
<exec_byte_code+17683>, 0x564c4c505086 <exec_byte_code+17800>,
0x564c4c504e7e <exec_byte_code+17280>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c505118 <exec_byte_code+17946>,
0x564c4c50519f <exec_byte_code+18081>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c504e7e <exec_byte_code+17280>,
0x564c4c504e7e <exec_byte_code+17280>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c504e7e <exec_byte_code+17280>,
0x564c4c504e7e <exec_byte_code+17280>, 0x564c4c504e7e
<exec_byte_code+17280>, 0x564c4c504e7e <exec_byte_code+17280>,
0x564c4c5052f7 <exec_byte_code+18425> <repeats 64 times>}
        quitcounter = 1 '\001'
        bc = 0x564c4cab2410 <main_thread+496>
        top = 0x7f89014b1048
        pc = 0x7f89024b5001 "\210\002:\205:"
        bytestr = XIL(0x7f890204f674)
        vector = XIL(0x7f890204f1cd)
        maxdepth = make_fixnum(11)
        const_length = 7
        bytestr_length = 59
        vectorp = 0x7f890204f1d0
        max_stack = 11
        frame_base = 0x7f89014b1030
        fp = 0x7f89014b1088
        bytestr_data = 0x7f89024b4ffc "\300\003\003\003#\210\002:\205:"
        rest = false
        mandatory = 3
        nonrest = 3
        pushedargs = 3
        result = XIL(0)
#15 0x0000564c4c4b0c6d in fetch_and_exec_byte_code
(fun=XIL(0x7f890204f18d), args_template=771, nargs=3, args=0x7ffe1b260628)
at eval.c:3085
#16 0x0000564c4c4b0fe1 in funcall_lambda (fun=XIL(0x7f890204f18d), nargs=3,
arg_vector=0x7ffe1b260628) at eval.c:3157
        val = XIL(0x7ffe1b260560)
        syms_left = make_fixnum(771)
        next = XIL(0)
        lexenv = XIL(0x1e0204f158)
        count = {
          bytes = 192
        }
        i = 45340716723288
        optional = false
        rest = false
        previous_rest = false
#17 0x0000564c4c4b050d in funcall_general (fun=XIL(0x7f890204f18d),
numargs=3, args=0x7ffe1b260628) at eval.c:2949
        original_fun = XIL(0x293cb5506c58)
#18 0x0000564c4c4b078e in Ffuncall (nargs=4, args=0x7ffe1b260620) at
eval.c:2999
        count = {
          bytes = 160
        }
        val = XIL(0x7ffe1b2605f0)
#19 0x0000564c4c3eaf38 in call3 (fn=XIL(0x293cb5506c58),
arg1=XIL(0x564c52d9c853), arg2=XIL(0x7f8901be9284),
arg3=XIL(0x293cb518a578)) at lisp.h:3262
#20 0x0000564c4c3ecf9f in cmd_error_internal (data=XIL(0x564c52d9c853),
context=0x7ffe1b2606d0 "") at keyboard.c:1013
#21 0x0000564c4c3ece84 in cmd_error (data=XIL(0x564c52d9c853)) at
keyboard.c:981
        old_level = XIL(0)
        old_length = XIL(0)
        count = {
          bytes = 96
        }
        conditions = XIL(0x7f89022845e3)
        macroerror =
"\000\a&\033\376\177\000\000L\316JLLV\000\000\367\213JL\001\000\000\000`\000\000\000\000\000\000\000\060\a&\033\376\177\000\000\324S\316RLV\000\000\000"
#22 0x0000564c4c4ac9ee in internal_condition_case (bfun=0x564c4c3ed64e
<command_loop_1>, handlers=XIL(0x90), hfun=0x564c4c3ecc8c <cmd_error>) at
eval.c:1470
        val = XIL(0x564c52d9c853)
        c = 0x564c4e5443e0
#23 0x0000564c4c3ed316 in command_loop_2 (handlers=XIL(0x90)) at
keyboard.c:1133
        val = make_fixnum(0)
#24 0x0000564c4c4ac0be in internal_catch (tag=XIL(0x10080),
func=0x564c4c3ed2ef <command_loop_2>, arg=XIL(0x90)) at eval.c:1197
        val = XIL(0x7ffe1b260810)
        c = 0x564c4e5424c0
#25 0x0000564c4c3ed2ab in command_loop () at keyboard.c:1111
#26 0x0000564c4c3ec837 in recursive_edit_1 () at keyboard.c:720
        count = {
          bytes = 32
        }
        val = make_fixnum(23721424373675)
#27 0x0000564c4c3ec9e0 in Frecursive_edit () at keyboard.c:803
        count = {
          bytes = 0
        }
        buffer = XIL(0)
#28 0x0000564c4c3e8dbf in main (argc=1, argv=0x7ffe1b260af8) at emacs.c:2521
        stack_bottom_variable = 0x564c4e4a3f20
        no_loadup = false
        junk = 0x0
        dname_arg = 0x0
        ch_to_dir = 0x0
        original_pwd = 0x0
        dump_mode = 0x0
        skip_args = 0
        temacs = 0x0
        attempt_load_pdump = true
        only_version = false
        rlim = {
          rlim_cur = 10022912,
          rlim_max = 18446744073709551615
        }
        lc_all = 0x0
        sockfd = -1
        module_assertions = false
You can't do that without a process to debug.
(gdb) frame 11
#11 0x0000564c4c4dd82f in print_error_message (data=XIL(0x564c52d9c853),
stream=XIL(0x30), context=0x7f89023daa83 "", caller=XIL(0x293cb518a578)) at
print.c:1134
1134  Fprin1 (obj, stream, Qnil);
(gdb) info locals
obj = XIL(0x564c55abc5a0)
li = {
  tortoise = XIL(0x564c52d9c873),
  max = 2,
  n = 0,
  q = 1
}
sep = 0x564c4c5c1c0c ", "
errname = XIL(0x11f40)
errmsg = XIL(0x564c520b0a84)
file_error = XIL(0)
tail = XIL(0x564c52d9c883)

(gdb) print data
$1 = XIL(0x564c52d9c853)
(gdb) xtype data
Lisp_Cons
(gdb) xcar data
$2 = 0x11f40
(gdb) xcdr data
$3 = 0x0
(gdb) xstring data
$4 = (struct Lisp_String *) 0x0
"DEAD"

(gdb) print obj
$31 = XIL(0x564c55abc5a0)
(gdb) xtype obj
Lisp_Symbol
(gdb) xcar obj
$32 = 0x0
(gdb) xcdr obj
$33 = 0x0
(gdb) xstring obj
$34 = (struct Lisp_String *) 0x0
"DEAD"

(gdb) print li
$35 = {
  tortoise = XIL(0x564c52d9c873),
  max = 2,
  n = 0,
  q = 1
}
(gdb) xtype li
Invalid cast.
(gdb) xcar li
Invalid cast.
(gdb) xcdr li
Invalid cast.
(gdb) xstring li
Invalid cast.

(gdb) print sep
$36 = 0x564c4c5c1c0c ", "
(gdb) xtype sep
Lisp_String
(gdb) xcar sep
$37 = 0x0
(gdb) xcdr sep
$38 = 0x0
(gdb) xstring sep
$39 = (struct Lisp_String *) 0x0
"DEAD"

(gdb) print errname
$40 = XIL(0x11f40)
(gdb) xtype errname
Lisp_Symbol
(gdb) xcar errname
$41 = 0x0
(gdb) xcdr errname
$42 = 0x0
(gdb) xstring errname
$43 = (struct Lisp_String *) 0x0
"DEAD"

(gdb) print errmsg
$44 = XIL(0x564c520b0a84)
(gdb) xtype errmsg
Lisp_String
(gdb) xcar errmsg
$45 = 0x0
(gdb) xcdr errmsg
$46 = 0x0
(gdb) xstring errmsg
$47 = (struct Lisp_String *) 0x0
"DEAD"

(gdb) print file
No symbol "file" in current context.
(gdb) xtype file
Lisp_Symbol
(gdb) xcar file
$48 = 0x0
(gdb) xcdr file
$49 = 0x0
(gdb) xstring file
$50 = (struct Lisp_String *) 0x0
"DEAD"

(gdb) print tail
$51 = XIL(0x564c52d9c883)
(gdb) xtype tail
Lisp_Cons
(gdb) xcar tail
$52 = 0x564c55abc5a0
(gdb) xcdr tail
$53 = 0x0
(gdb) xstring tail
$54 = (struct Lisp_String *) 0x0
"DEAD"


> Also, if you know what was the text copied from the other application,
> please show that text.
>

It seems to crash randomly. I will try to note down what I copied next time
it crashes.