Comment 2 for bug 1695546

The test case results in traces like this.

#0 0xb7758cf9 in __kernel_vsyscall ()
No symbol table info available.
#1 0xb728b050 in __libc_signal_restore_set (set=0xbf8395e0) at ../sysdeps/unix/sysv/linux/nptl-signals.h:79
No locals.
#2 __GI_raise (sig=6) at ../sysdeps/unix/sysv/linux/raise.c:55
        set = {__val = {18946, 0, 808464438, 926376493, 808466485, 762454064, 807432237, 808464432, 540028976, 809119792, 540024880, 538976288, 538976288, 1987468064, 173896289, 892811106, 808464440, 926376493, 808476981, 762454064, 807432312, 808464432, 540028976, 809119792, 540024880, 538976288, 538976288, 1685478176, 173895539, 892811106, 808464481, 926376493}}
        pid = <optimised out>
        tid = <optimised out>
        ret = 0
#3 0xb728c577 in __GI_abort () at abort.c:89
        save_stage = 2
        act = {__sigaction_handler = {sa_handler = 0x30320a5d, sa_sigaction = 0x30320a5d}, sa_mask = {__val = {908996910, 892822026, 808465971, 929180976, 808923957, 1914712112, 544222509, 1664102448, 808464481, 979592736, 840970544, 859255606, 538976310, 1815027744, 1764713065, 758528051, 1970170220, 1852255608, 1768697717, 1919117154, 779382905, 841903987, 774975024, 929172022, 808923957, 1647128624, 1630745911, 540028976, 1882027890, 808464416, 0, 4096}}, sa_flags = -1222154106, sa_restorer = 0xbf839840}
        sigs = {__val = {32, 0 <repeats 31 times>}}
#4 0xb72c6f4f in __libc_message (do_abort=<optimised out>, fmt=<optimised out>) at ../sysdeps/posix/libc_fatal.c:175
        ap = <optimised out>
        fd = 2
        on_2 = <optimised out>
        list = <optimised out>
        nlist = <optimised out>
        cp = <optimised out>
        written = <optimised out>
#5 0xb72cdb47 in malloc_printerr (action=<optimised out>, str=0xb73c2d5c "double free or corruption (out)", ptr=<optimised out>, ar_ptr=0xb7415780 <main_arena>) at malloc.c:5046
        buf = "809d68b0"
        cp = <optimised out>
        ar_ptr = 0xb7415780 <main_arena>
        ptr = <optimised out>
        str = 0xb73c2d5c "double free or corruption (out)"
        action = <optimised out>
#6 0xb72ce406 in _int_free (av=0xb7415780 <main_arena>, p=0x809d68a8, have_lock=0) at malloc.c:3902
        size = <optimised out>
        fb = <optimised out>
        nextchunk = <optimised out>
        nextsize = <optimised out>
        nextinuse = <optimised out>
        prevsize = <optimised out>
        bck = <optimised out>
        fwd = <optimised out>
        errstr = <optimised out>
        locked = <optimised out>
        __func__ = "_int_free"
#7 0xb75a76fe in source_free.lto_priv.128 (s=<optimised out>) at ../src/libsystemd/sd-event/sd-event.c:887
No locals.
#8 0xb7602507 in sd_event_source_unref (s=<optimised out>) at ../src/libsystemd/sd-event/sd-event.c:1402
No locals.
#9 0x800523b6 in dns_stream_stop.lto_priv.71 (s=<optimised out>) at ../src/resolve/resolved-dns-stream.c:35
No locals.
#10 0x8005240b in dns_stream_complete (s=<optimised out>, error=<optimised out>) at ../src/resolve/resolved-dns-stream.c:55
No locals.
#11 0x80052689 in on_stream_io.lto_priv.64 (es=0x809d6640, fd=18, revents=1, userdata=0x809d6738) at ../src/resolve/resolved-dns-stream.c:321
        s = 0x809d6738
        r = <optimised out>
        __PRETTY_FUNCTION__ = "on_stream_io"
#12 0xb7607cbf in source_dispatch (s=s@entry=0x809d6640) at ../src/libsystemd/sd-event/sd-event.c:2275
        r = <optimised out>
        __PRETTY_FUNCTION__ = "source_dispatch"
        __func__ = "source_dispatch"
#13 0xb7607e89 in sd_event_dispatch (e=0x809cf220) at ../src/libsystemd/sd-event/sd-event.c:2626
        p = <optimised out>
        r = <optimised out>
        __PRETTY_FUNCTION__ = "sd_event_dispatch"
#14 0xb760974b in sd_event_run (e=0x809cf220, timeout=18446744073709551615) at ../src/libsystemd/sd-event/sd-event.c:2685
        r = 1
        __PRETTY_FUNCTION__ = "sd_event_run"
#15 0xb760996d in sd_event_loop (e=0x809cf220) at ../src/libsystemd/sd-event/sd-event.c:2705
        r = <optimised out>
        __PRETTY_FUNCTION__ = "sd_event_loop"
#16 0x8003d908 in main (argc=<optimised out>, argv=<optimised out>) at ../src/resolve/resolved.c:106
        m = 0x0
        user = 0x8006da46 "systemd-resolve"
        uid = 102
        gid = 104
        r = 0
        __func__ = "main"
        __PRETTY_FUNCTION__ = "main"