Created attachment 333549 [details]
failed program

Compile attached program and run under valgrind using arguments "-t x -txxx x".

valgrind ./a.out -t x -txxx x
 Memcheck, a memory error detector
 Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
 Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
 Command: ./a.out -t x -t1 x
 
 Invalid free() / delete / delete[] / realloc()
    at 0x4C2BDEC: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    by 0x4E7ED18: Glib::OptionGroup::CppOptionEntry::release_c_arg() (optiongroup.cc:684)
    by 0x4E7ED50: Glib::OptionGroup::release_gobject() (optiongroup.cc:332)
    by 0x4E7EEA6: Glib::OptionGroup::~OptionGroup() (optiongroup.cc:344)
    by 0x40137C: MyOptionGroup::~MyOptionGroup() (in /home/andrey/tmp/test/a.out)
    by 0x401132: main (in /home/andrey/tmp/test/a.out)
  Address 0x6e80710 is 0 bytes inside a block of size 5 free'd
    at 0x4C2BDEC: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
    by 0x60417EF: parse_arg.isra.11 (goption.c:1284)
    by 0x6042043: parse_short_option (goption.c:1558)
    by 0x6043528: g_option_context_parse (goption.c:2066)
    by 0x4E7DD9A: Glib::OptionContext::parse(int&, char**&) (optioncontext.cc:212)
    by 0x401126: main (in /home/andrey/tmp/test/a.out)

Reproducible with git-master of glib and glibmm as of 18-August-2016.
The bug was initially found under OpenWrt with musl libc where it causes segfault.