https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64177
--- Comment #2 from iverbin at gcc dot gnu.org --- Actually, only 3 tests require 2+ workers (they fail with export CILK_NWORKERS=1): FAIL: c-c++-common/cilk-plus/CK/spawning_arg.c FAIL: c-c++-common/cilk-plus/CK/steal_check.c FAIL: g++.dg/cilk-plus/CK/catch_exc.cc It's unclear what happens with others. Maybe it's a bug in libcilkrts.