Using the following version of g++

    $ g++ --version
    g++ (GCC) 8.1.0
    Copyright (C) 2018 Free Software Foundation, Inc.
    This is free software; see the source for copying conditions.  There is NO
    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

I get the following error when building NS3

    ../src/mesh/model/dot11s/ie-dot11s-beacon-timing.cc: In member function ‘virtual bool ns3::dot11s::IeBeaconTiming::operator==(const ns3::WifiInformationElement&) const’:
    ../src/mesh/model/dot11s/ie-dot11s-beacon-timing.cc:209:15: error: catching polymorphic type ‘class std::bad_cast’ by value [-Werror=catch-value=]
       catch (std::bad_cast)
                   ^~~~~~~~
    cc1plus: all warnings being treated as errors

    Waf: Leaving directory `/home/mettinger/SNS3/ns-3-debug/build'
    Build failed
     -> task in 'ns3-mesh' failed (exit status 1): 
	    {task 139826318416080: cxx ie-dot11s-beacon-timing.cc -> ie-dot11s-beacon-timing.cc.1.o}
    ['/usr/bin/g++', '-O0', '-ggdb', '-g3', '-Wall', '-Werror', '-std=c++11', '-Wno-error=deprecated-declarations', '-fstrict-aliasing', '-Wstrict-aliasing', '-fPIC', '-pthread', '-I.', '-I..', '-DNS3_BUILD_PROFILE_DEBUG', '-DNS3_ASSERT_ENABLE', '-DNS3_LOG_ENABLE', '-DHAVE_SYS_IOCTL_H=1', '-DHAVE_IF_NETS_H=1', '-DHAVE_NET_ETHERNET_H=1', '-DHAVE_PACKET_H=1', '-DHAVE_IF_TUN_H=1', '-DHAVE_=1', '-DHAVE_GSL=1', '-DHAVE_SQLITE3=1', '../src/mesh/model/dot11s/ie-dot11s-beacon-timing.cc', '-c', '-o', '/home/mettinger/SNS3/ns-3-debug/build/src/mesh/model/dot11s/ie-dot11s-beacon-timing.cc.1.o']


A simple fix is to catch (std::bad_cast&) instead.