https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103638
--- Comment #1 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jonathan Wakely <r...@gcc.gnu.org>: https://gcc.gnu.org/g:ffb632517fc446474baba10ee2ff13a218ec2c7b commit r12-5895-gffb632517fc446474baba10ee2ff13a218ec2c7b Author: Jonathan Wakely <jwak...@redhat.com> Date: Fri Dec 10 11:44:29 2021 +0000 libstdc++: Guard mutex and condvar with gthreads macro [PR103638] A mutex and condition variable is used for timed waits on atomics if there is no "platform wait" (e.g. futex) supported. But the use of those types wasn't guarded by the _GLIBCXX_HAS_GTHREADS macro, causing errors for --disable-threads builds. This fix allows <atomic> to work on targets with futexes but no gthreads. libstdc++-v3/ChangeLog: PR libstdc++/103638 * include/bits/atomic_timed_wait.h: Check _GLIBCXX_HAS_GTHREADS before using std::mutex and std::__condvar.