https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95209
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #2) > You didn't provide the requested information when creating a new bug report, > please see https://gcc.gnu.org/bugs/ We're missing the output of 'gcc -v' but the preprocessed source shows the target is x86_64-suse-linux, and so this is the expected (and standard-conforming) behaviour. What meaning does //foo have on linux? As far as I know the linux kernel doesn't give it any special meaning. So for linux targets libstdc++ has a single implementation-defined root-name, which is the empty string and is never matched in a path.