https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70560
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to James Hilliard from comment #5) > That might be somewhere here: > http://autobuild.buildroot.org/results/3be/ > 3bedf404de0ea42ee3ba624cded65d310a847af9/apcupsd-3.14.14/config.log No, I meant the command that fails when running 'make'. But it doesn't matter now, because ... > It appears reference to _ZN9__gnu_cxx18__exchange_and_addEPVii are in the > following objects in libsupc++.a. I was looking for the definition of the function not the references to it, but I think the problem is that those functions are defined by src/c++98/atomicity.cc which isn't included in libsupc++.a at all. Using the atomic functions in libsupc++.a assumes that atomic builtins are supported and so we won't need the extern functions from atomicity.cc, which isn't necessarily true. I think this has been broken since r244051 enabled std::exception_ptr for targets without lock-free atomic built-ins. Previously if we didn't have atomic built-ins, libsupc++ just wouldn't try to use atomics. Now it uses the built-ins or falls back to the extern functions in atomicity.cc, but the latter are not in libsupc++.a so it only works if you link to the full libstdc++.{a,so} library. Please file a new bug, yours is a separate issue to this one.
