[Bug c++/78177] New: adding -flto flags causes linker error "undefined reference to vtable"

[steve.lorimer at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78177

            Bug ID: 78177
           Summary: adding -flto flags causes linker error "undefined
                    reference to vtable"
           Product: gcc
           Version: 5.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: steve.lorimer at gmail dot com
  Target Milestone: ---

I have code which compiles and links fine.

I'm now trying to enable link-time optimizations, but adding -flto to my
compiler and linker flags is causing a linker error:

/usr/local/lib/libboost_thread.a(thread.o): \
    In function `void
boost::throw_exception<boost::bad_lexical_cast>(boost::bad_lexical_cast
const&)':
   
thread.cpp:(.text._ZN5boost15throw_exceptionINS_16bad_lexical_castEEEvRKT_[_ZN5boost15throw_exceptionINS_16bad_lexical_castEEEvRKT_]+0x124):
\
        undefined reference to `vtable for boost::bad_lexical_cast'

The only flag I've added is -flto.

set(CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS_RELEASE} -flto" )
set(CMAKE_EXE_LINKER_FLAGS_RELEASE "${CMAKE_EXE_LINKER_FLAGS_RELEASE} -flto" )

To be clear:

Without -flto the app builds and links fine
With -flto (and no other changes), the app fails to link with the above error

I'm running version 5.4.0-6ubuntu1~16.04.2