Subject: bug#33530: 26.1.90; D-Bus crashes Emacs: consp, Fatal error 7: Bus error

From: Eli Zaretskii <[email-masked]>
Date: Wed, 28 Nov 2018 08:16:00 +0200

> From: Damien Cassou <[email-masked]>
> Date: Tue, 27 Nov 2018 21:59:01 +0100
> Cc: Paul Eggert <[email-masked]>, Michael Albinus <[email-masked]>
> 
> The following line crashes both Emacs 26 and Emacs master.
> 
> emacs -Q -batch --eval "(require 'dbus)" --eval "(dbus-call-method :system \"org.freedesktop.NetworkManager\" \"/org/freedesktop/NetworkManager/Devices/1\" \"org.freedesktop.NetworkManager.Device.Wireless\" \"RequestScan\" :dict-entry)"

It dies trying to display an error message:

> #5  0x0000000000674b2d in print_error_message (data=XIL(0x13472d3), stream=XIL(0x58b0), context=0xbc093e <pure+3999998> "", caller=XIL(0x2a90)) at print.c:980
>         obj = XIL(0xc8c7000c8421c6c5)
>         sep = 0x786fef ", "
>         errname = XIL(0xe3a0)
>         errmsg = XIL(0x7fb874)
>         file_error = XIL(0)
>         tail = XIL(0x13473b3)
> #6  0x0000000000591321 in Fcommand_error_default_function (data=XIL(0x13472d3), context=XIL(0x7f0064), signal=XIL(0x2a90)) at keyboard.c:1005
>         sf = 0xce2830 <bss_sbrk_buffer+511280>
> #7  0x00000000006485fa in funcall_subr (subr=0x7ebe80 <Scommand_error_default_function>, numargs=3, args=0x7fffffffce48) at eval.c:2939
>         internal_argbuf = {XIL(0x7fffffffcdb0), make_number(16107774448), XIL(0x7ebe80), XIL(0x7fffffffcd78), XIL(0x58716b), XIL(0xf00000000), XIL(0x7ebe85), XIL(0x7fffffffcd90)}
>         internal_args = 0x7fffffffce48
> #8  0x00000000006480ef in Ffuncall (nargs=4, args=0x7fffffffce40) at eval.c:2859
>         fun = XIL(0x7ebe85)
>         original_fun = XIL(0x9a9d0)
>         funcar = XIL(0x7fffffffceb0)
>         numargs = 3
>         val = XIL(0)
>         count = 3
> #9  0x0000000000647a93 in call3 (fn=XIL(0x9a9d0), arg1=XIL(0x13472d3), arg2=XIL(0x7f0064), arg3=XIL(0x2a90)) at eval.c:2726
> #10 0x00000000005911d8 in cmd_error_internal (data=XIL(0x13472d3), context=0x7fffffffceb0 "") at keyboard.c:972
> #11 0x00000000005910b7 in cmd_error (data=XIL(0x13472d3)) at keyboard.c:941
>         old_level = XIL(0)
>         old_length = XIL(0)
>         macroerror = "\000\316\377\377\001", '\000' <repeats 12 times>, "\317\377\377\377\177\000\000s_d", '\000' <repeats 13 times>, "ӛ1\001\000\000\000\000", <incomplete sequence \317>

Can you please show the value of 'data' in frame #10 or in frame #5,
in human-readable form?  This should be possible using the "xtype"
command followed by another x* command, according to what type is
shown by "xtype", probably "xsymbol".

Thanks.