https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122729
--- Comment #6 from Andrew Pinski <pinskia at gcc dot gnu.org> --- Does not matter, libiberty.h is NOT designed to be used outside of gcc, gdb, binnutils. If it is installed, then it is NOT designed to be -Wundef clean anyways. This is not a normal user header, it does not matter otherwise. Also r0-28272-gf31e826ba314bc was the last time it changed back in 2000 way before -Wundef existed. If you need to use libiberty.h, then you can't use -Wundef simple as that. There exists __cxa_demangle which should be used instead and that is part of the ABI since GCC 3.0 when GCC changed to use the libstdc++v3 and changed to use IA64 C++ ABI.
