The change seems reasonable but this needs a change to config/abi/pre/gnu.ver to export the new symbol in the GLIBCXX_3.4.34 version.
Please add full stops (periods) to the ChangeLog entry, to make complete sentences. Is "PR libstdc++/nnnn, target/nnnn" valid like that? I don't think it is, it should be two separate lines: <TAB>PR libstdc++/nnnn <TAB>PR target/nnnn
