segfault in group peer name change handler with latest toxcore master

[zugz]

Overview

1. uTox version: 951234f
2. Operating system: Linux
3. Desktop Environment/Window Manager (Linux/BSD only): dwm

Issue

Testing utox with latest c-toxcore master (1b232228), which includes some changes to groups, I encountered a segfault which I have not managed to reproduce.

It happened like this.

• I made a friend request to my utox user from a toxic client running on the same machine;
• I accepted the friend request in utox
• in toxic, I invited the utox friend to a group
• utox crashed, with the output pasted at the end of this report.

As far as I can see, this must be a matter of toxcore newly tickling a bug in utox, rather than a bug in toxcore. I may be wrong. I looked a little into the utox handler for name changes, and I could see nothing amiss.

I recognise that this isn't the most useful bug report! But maybe someone has a theory what might have caused this?

XLib Tray:    Incoming tray window event (28)
XLib tray:    Reached end of function, this is bad juju!
AL lib: (WW) alcCloseDevice: Releasing context 0xb200f040
FileTransfer: We know nothing of this file. This is probably an error. Friend(1) FileNum(65536)
NATIVE:       Unable to delete file!
                /home/zugz/.config/tox/avatars/2182[...].png
get_group:     index: 0 is out of bounds.
ASAN:SIGSEGV
=================================================================
==17631==ERROR: AddressSanitizer: SEGV on unknown address 0xb4100000 (pc 0xb6b80bfd sp 0xaddfadf0 bp 0xffffffff T3)
    #0 0xb6b80bfc in TT_RunIns (/usr/lib/i386-linux-gnu/libfreetype.so.6+0x22bfc)
    #1 0xb6b6695d (/usr/lib/i386-linux-gnu/libfreetype.so.6+0x895d)
    #2 0xb6b83b40 (/usr/lib/i386-linux-gnu/libfreetype.so.6+0x25b40)
    #3 0xb6b8445c (/usr/lib/i386-linux-gnu/libfreetype.so.6+0x2645c)
    #4 0xb6b70e56 in FT_Load_Glyph (/usr/lib/i386-linux-gnu/libfreetype.so.6+0x12e56)
    #5 0xb6b71504 in FT_Load_Char (/usr/lib/i386-linux-gnu/libfreetype.so.6+0x13504)
    #6 0x80a4f87 in font_getglyph (/home/zugz/tmp/uTox/utox+0x80a4f87)
    #7 0x80b7974 in textwidth (/home/zugz/tmp/uTox/utox+0x80b7974)
    #8 0x806de0b in text_height (/home/zugz/tmp/uTox/utox+0x806de0b)
    #9 0x82e2614 in msgheight_group (/home/zugz/tmp/uTox/utox+0x82e2614)
    #10 0x82e275d in message_setheight.lto_priv.360 (/home/zugz/tmp/uTox/utox+0x82e275d)
    #11 0x82e297e in message_updateheight.lto_priv.361 (/home/zugz/tmp/uTox/utox+0x82e297e)
    #12 0x82e3409 in message_add (/home/zugz/tmp/uTox/utox+0x82e3409)
    #13 0x82e3ba3 in message_add_group (/home/zugz/tmp/uTox/utox+0x82e3ba3)
    #14 0x82ed21d in group_add_message (/home/zugz/tmp/uTox/utox+0x82ed21d)
    #15 0x82ee279 in group_peer_name_change (/home/zugz/tmp/uTox/utox+0x82ee279)
    #16 0x8278f88 in callback_group_peer_name_change (/home/zugz/tmp/uTox/utox+0x8278f88)
    #17 0xb722813b in tox_conference_peer_name_handler (/usr/local/lib/libtoxcore.so.2+0x3b13b)
    #18 0xb7223642 in setnick (/usr/local/lib/libtoxcore.so.2+0x36642)
    #19 0xb7225c0e in handle_send_peers (/usr/local/lib/libtoxcore.so.2+0x38c0e)
    #20 0xb7225d49 in handle_direct_packet (/usr/local/lib/libtoxcore.so.2+0x38d49)
    #21 0xb7226d70 in g_handle_packet (/usr/local/lib/libtoxcore.so.2+0x39d70)
    #22 0xb721a22d in handle_packet (/usr/local/lib/libtoxcore.so.2+0x2d22d)
    #23 0xb720e819 in handle_data_packet_core (/usr/local/lib/libtoxcore.so.2+0x21819)
    #24 0xb720ec32 in handle_packet_connection (/usr/local/lib/libtoxcore.so.2+0x21c32)  
    #25 0xb72101b2 in udp_handle_packet (/usr/local/lib/libtoxcore.so.2+0x231b2)
    #26 0xb71fa47c in networking_poll (/usr/local/lib/libtoxcore.so.2+0xd47c)
    #27 0xb722070b in do_messenger (/usr/local/lib/libtoxcore.so.2+0x3370b)
    #28 0xb7228efb in tox_iterate (/usr/local/lib/libtoxcore.so.2+0x3befb)
    #29 0x82888d2 in toxcore_thread (/home/zugz/tmp/uTox/utox+0x82888d2)
    #30 0xb729f51f (/usr/lib/i386-linux-gnu/libasan.so.1+0x5651f)
    #31 0xb7267077 (/usr/lib/i386-linux-gnu/libasan.so.1+0x1e077)
    #32 0xb6f6feca in start_thread (/lib/i386-linux-gnu/i686/cmov/libpthread.so.0+0x6eca)
    #33 0xb6a27d0d in clone (/lib/i386-linux-gnu/i686/cmov/libc.so.6+0xebd0d)

AddressSanitizer can not provide additional info.
SUMMARY: AddressSanitizer: SEGV ??:0 TT_RunIns
Thread T3 created by T0 here:
    #0 0xb726701f in pthread_create (/usr/lib/i386-linux-gnu/libasan.so.1+0x1e01f)
    #1 0x80ad05b in thread (/home/zugz/tmp/uTox/utox+0x80ad05b)
    #2 0x809330c in main (/home/zugz/tmp/uTox/utox+0x809330c)
    #3 0xb6955a62 in __libc_start_main (/lib/i386-linux-gnu/i686/cmov/libc.so.6+0x19a62)

==17631==ABORTING