Link-Time-Optimized build segfault during static initialization

[jevolk]

An optimized build with -flto crashes during execution. This does not occur in any other optimized build without -flto.

relevant portion of stacktrace:

(#0 ... #10 template jumble in /deps/boost/include/boost/spirit/home/karma/*)

#11 ircd::json::printer::operator()<boost::spirit::karma::rule<char*, ircd::string_view, boost::spirit::unused_type, boost::spirit::unused_type, boost::spirit::unused_type> const&, ircd::string_view const&>(ircd::buffer::mutable_buffer&, boost::spirit::karma::rule<char*, ircd::string_view, boost::spirit::unused_type, boost::spirit::unused_type, boost::spirit::unused_type> const&, ircd::string_view const&) const [clone .isra.1773] [clone .lto_priv.3466] (out=..., g=..., a#0=...) at json.cc:356
#12 0x00007ffff7b25b56 in ircd::json::serialized (v=...) at json.cc:2706
#13 0x00007ffff7b2634a in ircd::json::value::value (this=this@entry=0x7fffffffdd50, other=...) at json.cc:2985
#14 0x00007ffff7ab9973 in __base_ctor  (__y=..., __x=..., this=0x7fffffffdd50) at /usr/include/c++/6/bits/stl_pair.h:311
#15 ircd::json::member::member<char const (&) [30]>(ircd::string_view const&, char const (&) [30]) [clone .lto_priv.2021] (this=0x7fffffffdd50, key=..., v=...) at json/member.h:69
#16 0x00007ffff7ab96ae in __static_initialization_and_destruction_0 (__initialize_p=1, __priority=65535) at ircd.cc:26
#17 _GLOBAL__sub_I_ircd.cc.lto_priv.1875 () at ircd.cc:405
#18 0x00007ffff7adb82e in global constructors keyed to 65535_0_info.o.568086 () from /home/jason/charybdis/lib/libircd.so.3
#19 0x00007ffff7de76ba in call_init (l=<optimized out>, argc=argc@entry=3, argv=argv@entry=0x7fffffffde58, env=env@entry=0x7fffffffde78) at dl-init.c:72
#20 0x00007ffff7de77cb in call_init (env=0x7fffffffde78, argv=0x7fffffffde58, argc=3, l=<optimized out>) at dl-init.c:30
#21 _dl_init (main_map=0x7ffff7ffe168, argc=3, argv=0x7fffffffde58, env=0x7fffffffde78) at dl-init.c:120
#22 0x00007ffff7dd7c6a in _dl_start_user () from /lib64/ld-linux-x86-64.so.2
#23 0x0000000000000003 in ?? ()
#24 0x00007fffffffe221 in ?? ()
#25 0x00007fffffffe245 in ?? ()
#26 0x00007fffffffe24e in ?? ()
#27 0x0000000000000000 in ?? ()

Link-Time-Optimization is not enabled by default due to [at least] this issue. To enable it manually configure with --enable-lto.