repro for mono dns lookup crash results dgb

gistfile1.txt

$ mono --debug test3.exe
Cannot handle address family 7136
Stacktrace:

  at <unknown> <0xffffffff>
  at (wrapper managed-to-native) System.Net.Dns.GetHostByName_internal (string,string&,string[]&,string[]&) <IL 0x00010, 0xffffffff>
  at System.Net.Dns.GetHostByName (string) [0x00011] in /tmp/buildd/mono-4.0.1.44/mcs/class/System/System.Net/Dns.cs:419
  at System.Net.Dns.GetHostEntry (string) [0x00061] in /tmp/buildd/mono-4.0.1.44/mcs/class/System/System.Net/Dns.cs:382
  at StatsdClient.StatsdUDP.GetIpv4Address (string) <IL 0x00012, 0x0004f>
  at StatsdClient.StatsdUDP..ctor (string,int,int) <IL 0x0002c, 0x000f9>
  at StatsdClient.Metrics.CreateStatsD (StatsdClient.MetricsConfig) <IL 0x00036, 0x000d1>
  at StatsdClient.Metrics.Configure (StatsdClient.MetricsConfig) <IL 0x0003f, 0x000b3>
  at Tests.IPV4ParsingTests.Main (string[]) <IL 0x00014, 0x0008b>
  at (wrapper runtime-invoke) <Module>.runtime_invoke_void_object (object,intptr,intptr,intptr) <IL 0x00060, 0xffffffff>

Native stacktrace:

        mono() [0x4b1fac]
        /lib/x86_64-linux-gnu/libpthread.so.0(+0x10340) [0x7fcd53636340]
        /lib/x86_64-linux-gnu/libc.so.6(gsignal+0x39) [0x7fcd53297cc9]
        /lib/x86_64-linux-gnu/libc.so.6(abort+0x148) [0x7fcd5329b0d8]
        mono() [0x629309]
        mono() [0x629517]
        mono() [0x6295c2]
        mono() [0x624c35]
        mono() [0x578b26]
        [0x40928da0]

Debug info from gdb:

  File "/usr/lib/debug/usr/bin/mono-sgen-gdb.py", line 34
    c = "\u%X".format (val)
                       ^
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 0-1: truncated \uXXXX escape
[New LWP 20361]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
0x00007fcd53635ee9 in __libc_waitpid (pid=20362, stat_loc=0x7fffa8a80dcc, options=0) at ../sysdeps/unix/sysv/linux/waitpid.c:40
40      ../sysdeps/unix/sysv/linux/waitpid.c: No such file or directory.
  Id   Target Id         Frame
  2    Thread 0x7fcd50b7b700 (LWP 20361) "Finalizer" sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:85
* 1    Thread 0x7fcd541687c0 (LWP 20360) "mono" 0x00007fcd53635ee9 in __libc_waitpid (pid=20362, stat_loc=0x7fffa8a80dcc, options=0) at ../sysdeps/unix/sysv/linux/waitpid.c:40

Thread 2 (Thread 0x7fcd50b7b700 (LWP 20361)):
#0  sem_wait () at ../nptl/sysdeps/unix/sysv/linux/x86_64/sem_wait.S:85
#1  0x000000000061e6a8 in mono_sem_wait ()
#2  0x00000000005a1c5e in ?? ()
#3  0x0000000000586f98 in ?? ()
#4  0x00000000006234d6 in ?? ()
#5  0x00007fcd5362e182 in start_thread (arg=0x7fcd50b7b700) at pthread_create.c:312
#6  0x00007fcd5335b47d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111

Thread 1 (Thread 0x7fcd541687c0 (LWP 20360)):
#0  0x00007fcd53635ee9 in __libc_waitpid (pid=20362, stat_loc=0x7fffa8a80dcc, options=0) at ../sysdeps/unix/sysv/linux/waitpid.c:40
#1  0x00000000004b2039 in ?? ()
#2  <signal handler called>
#3  0x00007fcd53297cc9 in __GI_raise (sig=sig@entry=6) at ../nptl/sysdeps/unix/sysv/linux/raise.c:56
#4  0x00007fcd5329b0d8 in __GI_abort () at abort.c:89
#5  0x0000000000629309 in ?? ()
#6  0x0000000000629517 in ?? ()
#7  0x00000000006295c2 in ?? ()
#8  0x0000000000624c35 in ?? ()
#9  0x0000000000578b26 in ?? ()
#10 0x0000000040928da0 in ?? ()
#11 0x00000000022e9380 in ?? ()
#12 0x00007fcd52400d70 in ?? ()
#13 0x00007fcd52a08140 in ?? ()
#14 0x00007fcd52a08140 in ?? ()
#15 0x00007fcd52a08140 in ?? ()
#16 0x00000000022e4640 in ?? ()
#17 0x0000000040928d23 in ?? ()
#18 0x00007fffa8a82210 in ?? ()
#19 0x00007fffa8a81fe0 in ?? ()
#20 0x0000000040928c8e in ?? ()
#21 0x00007fcd52a08140 in ?? ()
#22 0x0000000000000000 in ?? ()

=================================================================
Got a SIGABRT while executing native code. This usually indicates
a fatal error in the mono runtime or one of the native libraries
used by your application.
=================================================================

Aborted