GCC 5.x contains libstdc++ with [dual ABI][1] support and we have now switched to the new ABI. While the old C++ ABI is still available, it is recommended that you build all non-repo packages to have the new ABI. This is particularly important if they link to another library built against the new ABI. You can get a list of packages to rebuild using the following shell script: #!/bin/bash while read pkg; do mapfile -t files < <(pacman -Qlq $pkg | grep -v /$) grep -Fq libstdc++.so.6 "${files[@]}" 2>/dev/null && echo $pkg done < <(pacman -Qmq) (Original announcement text by Allan McRae [[link][2]]) [1]: https://gcc.gnu.org/onlinedocs/libstdc++/manual/using_dual_abi.html [2]: https://lists.archlinux.org/pipermail/arch-dev- public/2015-December/027597.html URL: https://www.archlinux.org/news/c-abi-change/