https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69191
--- Comment #10 from Jonathan Wakely <redi at gcc dot gnu.org> --- Use ldd to see which library is used at runtime. See what file that symlink points to. Compare with the version numbers of the releases. GCC 4.9.0: libstdc++.so.6.0.20 GCC 5.1.0: libstdc++.so.6.0.21